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materials selection for ball mill

4 installation steps, 10 requirements and medium selection of ball mill | fote machinery

4 installation steps, 10 requirements and medium selection of ball mill | fote machinery

Ball mill installation is a must step before it is put into production, which will affect the subsequent use of the ball mill, and even affect the production volume, crushing rate, service life, etc., so the importance of ball mill installation is self-evident.

In addition, the choice of grinding medium is also crucial. In the grinding process, different grinding medium can be used for different materials, models and equipment, which can reduce production costs and improve production efficiency.

There are four chassis should be installed: the front tile base, the rear tile base, the motor chassis and the reducer chassis. During the installation of the chassis, the horizontality and horizontal elevation of the chassis must be checked by a level or level gauge and a steel rule.

At the same time, the width of these wedges should be between 50 and 60 mm; the length should be at least ensured to exceed the centerline of the anchor bolts inside the chassis, and the outside should be exposed to a length of 10 to 50 mm; the slope of the wedge should be between 1:10 and 1:20.

If the actual combined size between the motor cylinder and the hollow shaft is inconsistent with the technical documents of the equipment or the relevant design, the construction may be carried out according to the actual size after obtaining the consent of the relevant unit personnel.

The transverse centerlines of the two main bearing chassis must coincide and allow for a combined error of no more than 0.5 mm. The non-horizontal degree of the main bearing chassis is allowed to differ by 0.1 mm/m, and the error of the non-parallelism is 0.5 mm/m, but the ball mill must be ensured to discharge materials.

Before the installation of the spherical surface of the main bearing, it is necessary to carefully check whether there are blisters, pores, cracks and other defects on the babbitt surface and the spherical surface, and there is no possibility of shrinking the shell in the interval between the hollow shaft and the contact surface of the bushing. phenomenon.

Firstly, before assembling the cylinder and the end cap, check the cylinder to ensure that the ellipse of the cylinder is not larger than 4 of the diameter of the cylinder. And meanwhile, the ovality and surface smoothness of the hollow journal should also be checked.

After the end cap and the cylinder bolt hole are aligned with the positioning pin, put a 1/4 number of bolts and tighten by hand, one-third of which are half tightened, and the concentricity is adjusted within 0.25mm, and then tightened.

Next, the cylinder and end cap assembly are transferred into the main bearing, but the housing must be adjusted to meet the requirements before the cylinder and end cap assembly are installed in the main bearing.

After assembling, the assembled cylinder should be measured and the total length and the length of the center of the two journals are compared with the center distance of the bearing housing to make sure they match with each other, otherwise, the bearing housing or the position of the main base need to be adjusted.

The inner surface of the ball mill cylinder is generally equipped with liners of various shapes that are the main wearing parts of the ball mill, and whose cost is about 2%-3% of the price of the whole product.

Thus, the performance and service life of the lining plate are issues that users are very concerned about, for its performance will directly affect the performance of the ball mill. The following are the 10 requirements for the liner installation.

The greater the density of the grinding medium is, the shorter the grinding time is. In order to increase the grinding effect, the hardness of the grinding medium must be greater than the hardness of the material to be ground.

According to long-term experience, the Mohs hardness of the medium is preferably greater than the hardness of the material to be ground by more than three grades. In addition, the smaller the size of the grinding medium is, the more the contact points it will be.

The loading amount has a direct influence on the grinding efficiency, and the particle size of the grinding medium determines the loading amount of the grinding medium. It must be ensured that when the grinding medium moves in the disperser, the porosity of the medium is not less than 40%.

For different fineness requirements, it is necessary to adjust the ability of the grinding medium to break and grind. The filling rate is high and the grinding ability is strong. On the contrary, the crushing ability is weak. When super fine grinding, the high filling rate is generally adopted.

Grinding medium generally is spherical because other irregularly shaped medium can wear themselves and cause unnecessary contamination. The size of the medium directly affects the grinding efficiency and product fineness.

The larger the diameter is, the larger the product size and the yield are. Conversely, the smaller the particle size is, the smaller the particle size and the the yield are. In actual production, it is generally determined by the feed size and the required product fineness.

Generally speaking, in the continuous grinding process, the size of the grinding medium is distributed regularly. The medium size ratio is directly related to whether the grinding ability can be exerted and how to reduce the wear of the medium.

In the process, it will not always maintain at a fixed medium ratio. So, the method of replenishing large balls is used to restore the grinding of the system. It is difficult for the mill to maintain at a fixed medium ratio for a long time.

In the production process, it is necessary to explore the appropriate ratio according to the type of material and the characteristics of the process, and remove the too small medium in time to reduce the cost.

The wear resistance and chemical stability of the grinding medium are important conditions for measuring the quality of the grinding medium. The non-wearing media needs to be supplemented by the need of abrasion, which not only increases the cost, but more importantly affects the production.

As common grinding equipment, ball mills are widely used in power, chemical, mining, cement and other processing sectors. At present, there are many kinds of ball mills popular in the market, with various functions and different prices.

Therefore, enterprises often face a dazzling situation when purchasing. Generally, when selecting a ball mill, the company must combine the material properties, abrasive requirements, production environment, energy consumption and other factors through scientifically comparing to select the ball mill that is most suitable for its use requirements.

As a leading mining machinery manufacturer and exporter in China, we are always here to provide you with high quality products and better services. Welcome to contact us through one of the following ways or visit our company and factories.

Based on the high quality and complete after-sales service, our products have been exported to more than 120 countries and regions. Fote Machinery has been the choice of more than 200,000 customers.

bal-tec - ball material selection

bal-tec - ball material selection

You need some balls just like the sample, but how do you find out what it is? Or you may need help in choosing the right ball material for a particular application. The safest place to start is with the application itself. What does the ball do?

"Bearing balls" is the general term for any hard steel ball that will function in a roller bearing application. Common materials are hard chrome steel 52100, C/S, 440C hard stainless steel and carbonized high carbon steel. High speed steel might be added to this list for severe and high temperature applications.

If it is a ball bearing application, the most likely material is chrome steel which is 52100 chrome alloy steel. This is a relatively inexpensive material. This material is very hard, at about 62 HRC (Hardness on the Rockwell "C" scale). It is highly magnetic. It is not corrosion resistant, it will rust easily. Chrome alloy steel balls comprise about 90% of all balls manufactured. This material is a high carbon (1.00%), chrome (1.36%) alloy steel that will harden into the 60 - 65 HRC range when oil quenched from a soaking temperature of 1475 F. The hardness usually ends up at 62 HRC. The stress relieving or drawing temperature is 325 F. This does not mean that this steel can be used up to this temperature. We have run repeated tests where we elevated the temperature to 325 F. In the first three cycles, the samples dropped one point of HRC each time they were treated. It begins to lose its hardness at temperatures above 300 F. It is a fine grade material that can be precision ground and lapped spherical within a few millionths of an inch with a sub micro inch surface quality. It is highly magnetic in the sense that it will be attracted by a magnet.

51100 steel is a very low alloy chrome steel that was widely used during WW II as a means of conserving chromium. It is more susceptible to stress cracking during the quenching cycle of heat treating than the more conventional 52100 chrome alloy steel. This material is highly magnetic. It will through harden in reasonable sections. It will harden to 60 to 65 HRC. With a 325 F draw, it will average 62 HRC.

The third possibility is that, it is a case hardened carbon steel, i.e. hard carbon steel. For the most part, these less expensive balls are used in cheap bearings for casters, conveyors, bicycles and toys.

This material is highly magnetic. It has a thin carbon rich layer, cooked into the surface, that is then hardened to the equivalent of 60 HRC. This material is extremely rust prone. These balls are manufactured from low carbon steel wire, i.e. type 1018 steel. The ball blanks are cold headed, flashed and ground. They are then heated to 1700 F in a very carbon-rich, gaseous environment to develop a high carbon case or shell in a rotary hearth furnace--carbon is literally cooked into the outer surface of the steel balls. After cooling, they are re-heated and oil or water quenched, depending on size. Next, they are tempered at 325 F to relieve the stresses and to reduce the hardness slightly so they won't be brittle. After carbonizing, this material may be heat treated to the equivalent of 60 HRC. Because of the thin hardened layer, a special micro hardness test must be used to evaluate the hardness. It should be remembered that the hard outer surface is only a thin case or shell. Finally, these balls are ground and polished.

Soft low carbon steel (type 1018; 0.18% Carbon, 0.8% Manganese, balance Fe - Iron) balls are produced commercially in most common fractional inch sizes, up to 1 inch ( 25.4 mm). These balls are ground round with a highly polished decorative finish.

We custom produce soft, low carbon steel balls in the entire size range from subminiature to 17 inches (432 mm). These custom made balls can be supplied as: precision machined only, precision ground, or precision ground and polished. This material can be easily drilled, threaded, and otherwise machined with conventional chip-making machines. Type 1018, soft, low carbon steel, balls are very weldable.

The last common bearing material is high-speed extremely high temperature alloy steel. This is only found in hot bearing applications. High speed steel balls are usually produced from type M50 or M10 steel. Many of the "T" type high speed steels are almost impossible to purchase today, High speed steel's main property is its very high temperature resistance. High speed steel will remain hard even at red temperatures. High speed steels are generally harder than the standard chrome steel. It is typically 65 HRC. This material is highly magnetic. We can usually grind this material with expensive cubic boron nitride abrasive. It can be drilled, threaded and otherwise machined using the EDM process (Electro Discharge Machine).

Precision balls can be produced from this material, but there is really no good reason to use it. The properties of this material have no advantage over the standard 52100 chrome alloy steel, which is less expensive and more readily available.

06 Tool Steel finds frequent use for the production of large and very precision balls. It is reasonably machinable. It is readily available in large diameter, cylindrical form. It will through harden, even in very large diameters. It can be ground and lapped to a very high quality.

Ball screws are very similar to ball bearings in that they generally use either chrome steel or type 440C hard stainless steel. A peculiarity of ball screws is that they typically have a load ball and the next ball is a .001-inch undersized spacer ball, and so on. One half of the balls are load balls and one half are spacer balls.

In exotic aerospace or life threatening situations, you should obviously not use home-grown tests to validate materials since sophisticated alloys like high-speed steel, Stellite or HASTELLOY may test similar to other common materials, but in fact have extremely different physical properties. The Stellite alloys most most frequently used for balls are Star J or number three. They are very hard and wear resistant. See our page, Radiations Hardened Kinematic Systems for more information on Stellite.

Another place where balls are widely used is in the plumbing of pneumatic and hydraulic systems. Ball check valves, flow control valves, pressure relief valves and pressure regulating valves all use ball and seat combinations to perform their functions.

In pure hydraulic oil systems, the most common ball material is chrome alloy 52100 steel. This ball will be very hard, and highly magnetic, but it is not corrosion resistant and will test positive in any of the corrosion tests. In the grinding spark test it will be orange in color with many side bursts, as the carbon burns with the oxygen in the atmosphere (incineration).

Some high-end hydraulic systems may use type 440C stainless steel. This material is highly magnetic, it is hard and it will not react to any of the corrosion tests. In the grinding spark test, it will have a short red spark with almost no side burst. In the plumbing for the food processing industry, HASTELLOY, Stellite and even Tungsten Carbide (TC) balls are often used.

is very hard. It is almost non magnetic. It is extremely corrosive resistant. When spark tested, it will give off almost no indication at all, outside of a few red tracers. HASTELLOY is tough but not very hard. A file will cut it with ease. It is an extremely corrosion-resistant material. The cylindrical bar stock to make these balls costs us $71.00 per pound in 2008. High quality balls of any size can be produced from this material.

Tungsten-carbide is very very heavy. Many times all you have to do is to heft it to distinguish its enormous mass. It will not react to any of the corrosion tests. It will emit no spark at all when ground with a conventional abrasive wheel. It is the hardest of all synthetic materials. If you look at this material critically, it is not a silvery metallic but is a dark gray in color. Tungsten-carbide is only slightly magnetic and is usually easy to distinguish from steel. See our shopping cart for available stock.

In tap water systems, brass balls are often used, although type 316 stainless steel will show up in high-end systems. The bright golden color of the brass gives it away. It is dead soft. It is entirely non-magnetic. The corrosion tests will only brighten the gold color.

Is the ball hard? Measuring the actual hardness of a precision ball is a complicated and difficult procedure. To make a shop test of hardness, first procure a brand-new, flat, fine toothed, mill bastard file. Hold the ball to be tested in the jaws of a set of clamping pliers like vise grips.

A good fast test of corrosion resistance is to immerse pre-cleaned test balls in a 5 percent solution of nitric-acid in alcohol. This "Nital" solution will turn all steels a light to dark gray in just 2 minutes. It won't change the color of corrosive-resistant materials.

An even better test is the copper-sulfate test. This solution consists of copper-sulfate crystals dissolved in a 6-percent solution of sulfuric-acid and water. A drop of this solution on the surface of a clean steel ball will immediately form a bright spot of copper-plating. This solution will not affect any of the corrosive resistant materials within a two-minute period, but may react to hard ferritic or Martensitic stainless-steel after a long period of exposure. See our picture gallery page.

Is the ball magnetic? Here we must be a little careful. Many materials that most people consider totally non-magnetic, like 300 series stainless steels, can become slightly magnetic when it is cold work-hardened. Remember that commercial balls are made by cold-heading the blanks from wire. Then they are rolled between two hard steel plates to remove the cold heading flash from them. Both of these processes generate strains in the balls that will make them at least slightly magnetic.

Use an ordinary pocket magnet to test for magnetism, not one of the very powerful rare earth magnets. If the magnet strongly attracts the ball, it is one of the steel materials. If it doesn't attract it at all, or if it only has a very slight attraction it is one of the corrosive resistant materials, or else a totally nonferrous (without iron) material.

It may sound obvious, but look at the sample ball. For many applications on board ships, it is not unusual to find brass, bronze, or aluminum-bronze balls. It is also common to find these materials in plumbing and valve applications. Clean the ball with a strong detergent; brassy materials will be a golden yellow color. Brass and bronze are totally non-magnetic while aluminum-bronze will be very slightly attracted by a magnet.

is a fairly common plastic ball material. It is heavier than most plastics and quickly sinks in water. It is very white in color. It will actually feel slippery to the touch. This material is the most corrosion-resistant plastic material. This material will operate at the highest and the lowest temperatures of any plastic ball material. This is one of the most expensive plastic materials. See our PTFE ball stock in our shopping cart.

The spark test can be a very effective test procedure to help identify a material. Use an ordinary shop grinder for this test. Ideally use a course (40) grit grinding wheel. This test is more effective in an almost dark area. The grinding wheel should be dressed to remove any metal embedded in the surface. Hold the ball in the same vise grip pliers used for the file hardness test. Hold the ball lightly against the rotating grinding wheel and observe the sparks that result. Lets break the appearance of the sparks coming off the grinding wheel down into three categories: The color of the spark. Don't look at anything but the color. 440c and high-speed steel will give a very red spark. Chrome steel will give a bright orange spark. Hard carbon steel will give a nearly white spark. 300 series stainless, Monel K-Monel and HASTELLOY will give almost no spark at all. If you use a heavy pressure you may get a few tiny red darts. The length of the spark is the next characteristic to look at; 440c and high-speed steel will throw a short spark. Chrome steel will throw a medium long spark. Hard carbon steel will throw a much longer spark on the same wheel at the same pressure. The nature of the spark will vary with the different materials. The free carbon in the steel incinerates or burns in the oxygen of our atmosphere. This forms a burst or side spark that comes off the main spark at an angle. In high alloy steels the carbon is tied up in high temperature combinations of chrome, cobalt, molybdenum or tungsten, so there is very little burst, if any. This group includes type 440C stainless steel and the high-speed steels. In materials such as chrome steel, which only a small percent of alloy, the incineration or explosion of the spark is much more pronounced and occurs closer to the grinding wheel. There will be a lot of side sparks. High carbon steel basically has no alloy except extremely high carbon content, so there are lots of sparks up and down the streamers leaving the wheel. There will be almost no spark with many materials like 300 series stainless, HASTELLOY, Monels or Stellites. Synopsis The best possible aid to spark testing is to have balls of known materials to compare the sparks with. Break the spark into the three characteristics of color, length, and incineration (side sparks or bursts). Add the information regarding the hardness, magnetism and corrosion resistance and you will be able to nail down ninety five percent of the ball materials. Please give our office a call at (323) 582-7348 with any questions, or toll-free at 800-322-5832. Quality To the quest of determining the material, we must add that of determining the required quality. For bearings and ball screws with balls from 1/16" (.0625 inch, 1.59 mm) to 5/8" (.625 inch, 15.9 mm), A.F.B.M.A. grade-25 is a good commercial quality that is good enough for most commercial applications. Request a ball grade chart, printed on plastic, from our office to better understand the quality and grade specifications and one will be sent to you free of charge. It is available as a download from our web site. For larger and smaller balls, a lower quality grade may be used for economic reasons. Grade 50 or grade 100 are usually available as an economic alternative to grade 25. In valve and plumbing applications, much softer corrosive-resistant materials are often used. It is very expensive to produce the highest quality balls in these soft stainless steel and non-ferrous materials. The high quality balls in these materials are usually Grade 100 and good commercial quality balls are Grade 200. Call our office for technical assistance. Ball Materials 1018 Soft Mild Steel Type 1018 soft mild steel has a very low carbon content. This steel is not hard. It can be machined, drilled and tapped. This material is highly magnetic. It will be strongly attracted by a magnet. This is one of the most weldable steel alloys. Hardness is rated at 28 HRC. 17-4 PH 17-4 PH is one of the family of precipitation hardened nickel based alloys. It combines high strength and good corrosion resistance with moderate hardness. It is hardened by soaking at an elevated temperature for a period of time. The most common soaking temperature is 900 F. This heat treating is referred to as H-900. In the solution annealed condition, this material has moderately good machining properties. 15-5 PH is another of the common PH alloys. 300 Series Stainless Steel If the application isn't too severe, type 316 stainless steel may be used. The 300 series stainless steels are basically an alloy of 18% chromium and 8% nickel with the balance ferrite (iron). This material is dead soft at about 30 HRC (Hardness Rockwell "C" scale), and is almost non magnetic in the annealed condition. Pneumatic In pneumatic systems, there is usually water or water vapor present. To prevent rust, type 316 stainless steel is used. The spark test will yield only tiny red tracers. This material will not respond to any of the corrosion tests. It is almost non-magnetic. It is dead soft and the file test will put an immediate flat on the ball. 420 Stainless Steel Type 420 hard stainless steel is the material widely used in Europe. It is very similar to type 440C, which is more widely used in the United States. Type 420 is not quite as hard as the type 440C. One of the advantages of 420 over type 440C is that it has a higher magnetic permeability, so that it is attracted more strongly by a magnetic field. 440C Stainless Steel 440C Stainless Steel is one of the most amazing standard ball materials. It is a very high chromium, high carbon, martensitic stainless steel. Martensite is the very hard state of a high carbon steel. When heat treated from the spherodize annealed condition, it forms an extremely fine grain structure. For hardening, it must be raised to 1900 F. It will harden to 58 - 63 HRC. It is usually at the low end of this range, when tempered at 400 F If the bearing is used in a corrosive or wet environment, it may be a type 440C hard martensitic stainless steel. This material is very magnetic and it is hard, but it is not as hard as chrome steel. It is about 58 HRC (Hardness Rockwell "C" scale). This material is only mildly corrosive resistant and will only respond to corrosion tests with slight pitting. It will eventually corrode in tap water and will not stand up to sea water at all. It is widely used as a premium bearing material and it is the top material for use in gaging products. See our article, Stainless Steel Balls, Type 440C Hardened for more information. Aluminum Balls 1100 series aluminum is commercially pure aluminum. It is a very light weight material that is a silvery white color, one of the natural base elements, and very ductile. Balls made of 1100 series aluminum are often used as closures. They are squashed or upset to permanently close a hole (an inside diameter). It is difficult to locate this material in less than mill-run quantities. 2017 aluminum is a copper alloy of aluminum that was originally developed for the manufacture of rivets. Its number one quality is that it can be safely cold-headed, which makes it an excellent choice as a material for precision balls. This is the aluminum alloy specified by Mil-B-1083, the generally accepted military specification for precision balls. This alloy has also been chosen by the AFBMA (Anti Friction Bearing Manufacturers Association as a standard ball material. This material is usually heat treated to the "T4" condition. This is not a good choice if the ball is to be anodized. High quality balls can be produced from this alloy. Aluminum Alloy 2017 Manganese 0.7% Copper 4.0% Magnesium 0.5% Aluminum balance 2024 aluminum alloy is an aluminum copper alloy. It is a high strength material, widely used in aircraft. It can be cold headed. The tensile strength of this alloy can be improved by heat treating. This alloy is not a good choice for hard anodizing as the segregation of copper will form voids and can even cause incineration of the metal during the anodizing process. Aluminum balls of all type are often used as closures by compressing them to seal a close fitting hole. Aluminum Alloy 6061 6061 Aluminum alloy is a widely used, readily available, aluminum material. This material should never be cold headed--it can develop internal fissures that will lead to catastrophic failure. This alloy has much better machining qualities than 2017 alloy. This alloy is an excellent choice when the balls are to be hard anodized. The tensile strength of this alloy can be improved by heat treating. This aluminum alloy is relatively light at 0.098 lbs/ cu in. Aluminum Bronze It is very slightly magnetic. An aluminum bronze ball will roll towards a powerful magnet. This material is very resistant to sea water. Some alloys of this material can be heat treated to increase its hardness and tensile strength, but the hardening process reduces corrosive resistance. It is a very good electrical conductor. A286 Balls A286 is one of the exotic Space Age materials. It has good wear properties. It is corrosion resistant. This material must be heat treated to develop its best physical properties. This material is very expensive. Very high quality balls can be produced from this material. Black Oxide Balls Black Phosphate Balls High quality steel balls of both chrome steel and hard stainless steel can be treated chemically to color the surface black. This black iron phosphate actually penetrates the surface so that the original size and surface quality is not affected. The most common application for this surface treatment is to provide identity for these balls. In some bearing and ball screw applications, two different size balls are used in the same device. The larger diameter balls are load bearing balls, and the smaller diameter black balls are used as spacer balls. Brass Balls We manufacture and stock a large variety of brass balls. Brass balls are gold or bright yellow in color. The Standard alloy is 70-30, which is 70% copper and 30% zinc. The only major problem with the metallurgy of brass is segregation. This is due to the high melting point of copper (3000 F) and the low melting point of zinc (800 F). This material is quite ductile and very malleable. It is corrosive resistant to tap water, but does not stand up well in sea water. It is nonmagnetic, an excellent electrical conductor, and has excellent solder ability with soft solder, but may require chemical cleaning to remove an oxide layer. Brass has a hardness of less than 30 HRC, is very machinable, and it may be drilled and tapped easily. Brass is a relatively heavy material at .275 - .316 lbs/cu in (7.60 - 8.75 g / cc). Naval Brass or Naval Bronze Naval Brass or Naval Bronze is very similar to brass, but has an addition of 0.5% to 1.0% tin. This small addition gives to material good corrosive resistance to sea water.Naval brass or bronze is a relatively heavy material at .305 lbs/ cu in. We will custom manufacture special alloys if the material is commercially available. Brass balls are precision ground and polished. They can be produced to AFBMA standards when required. We produce brass balls in all sizes from the sub-miniature to very large diameters. Copper We manufacture copper balls in the entire range of sizes from sub-miniature to several inches in diameter. Pure copper, as well as the many copper alloys, can be used to produce highly accurate precision balls. Copper, usually oxygen free, has excellent electrical and heat conductivity, as well as good corrosion resistance in many harsh environments. It is nonmagnetic. It is sometimes annealed after all forming and machining is completed, to enhance its electrical properties. It is extremely malleable and ductile. It is very soft, but it is gummy and very difficult to machine, tending to gall easily. It is very solderable, and it is very corrosive resistant to sea water. Copper has a distinctly red color. Diamond-Impregnated Brass Balls Diamond-impregnated balls are used to lap the spherical radius in ball valves. They usually have a stem or handle attached to facilitate holding during the lapping process. See our Diamond Impregnated Ball Lap page for more information. Gold An obvious use for gold is for jewelry. The nobility of gold meaning its resistance to corrosion and its good electrical conductivity leads to use in electrical applications. Gold has a high level of x-ray opacity and good bio-compatibility, which leads to its use as x-ray markers in medical applications. As gold is such an expensive material, we do not maintain a stock of gold balls. Hevimet Hevimet is usually sintered from powdered tungsten and powdered copper. Its very heavy weight makes it an alternative to lead in some uses. It is machinable, and unlike lead it is biologically safe. Ball's made of this material are used as counter-weights, and to add mass to mechanical structures. High Speed Steel High speed steel such as M50 and M10 or T15 are usually reserved for hot end bearings and high temperature ball screw applications. These materials are not corrosive resistant and will react to any of the corrosive tests. These materials are very hard. They will test up to 65 HRC. They will be strongly attracted by a magnet. When spark tested, they will give short red tracers with almost no side bursts. These balls are often supplied in very high quality grades, up to A.F.B.M.A. Grade 10. Inconel X Balls 7-18 Inconel is of one the exotic space-age metals, a trademark of Special Metals Corp. Inconel 7-18 is truly an aerospace metal. Inconel is hard and strong. It will continue to perform at high temperatures. It will also perform at temperatures so cold that hydrogen is a liquid. These low temperatures are so cold that there is a special word for it, cryogenic. The highest quality is required for these aerospace oriented balls. In many cases, every single individual ball must have its own pedigree accompanying it. This will include the physical and chemical analysis of the individual bar of material, an ultrasonic examination, and the heat treating process that was performed on it. Along with this will be the diameter of the ball on three orthogonal axii and three polar charts of the roundness taken on three orthogonal axii. A rocket engine using inconel balls depends on the integrity of each individual ball, making them crucial parts of the rocket engine. In addition, Inconel is highly corrosive resistant. It is precipitation hardened. This metal alloy must be heat-treated to develop its good physical properties. Care should be exercised in specifying the desired heat treatment as the furnace time for some processes may be very long and therefore, very expensive. We manufactured Inconel balls for the Apollo and Space Shuttle programs. Inconel is a very expensive material, and may require considerable lead time just to procure the raw material. To see our stock of Inconel balls, click here. Monel There are a number of different Monel alloys, a trademark of Special Metals Corp.. The basic alloy has a minimum of 23% copper and minimum of 60% nickel with small amounts of iron and manganese. This material is very tough but not very hard. It is not heat treatable. Monel is used in very corrosive environments. It is excellent in salt water applications such as valves for sea water. It is also used in the food processing industry. We make Monel balls in a wide range of sizes. Due to its relatively soft nature, AFBMA grade 200 is the normal quality specification, although grade 100 can be achieved with some difficulty. It is relatively soft at about 38 HRC, and it is difficult to drill and tap. MP35N MP35N finds use for check valve applications where no other metal could ever survive. In down hole control valves where the chemistry of the environment would eat a stainless steel ball, balls made of this material will last indefinitely. This material is so tough that producing precision balls from it is a major problem. It cannot be cold headed at all. The forging temperatures are extreme. Like many of the exotic metals, MP35N can be lapped to a very high level of quality, once the spherical blank has been produced. The word expensive was coined to describe this material. Delivery is also a problem as the material has to be special ordered. MP35N Composition Ni, Nickel 35% Co, Cobalt 35% Cr, Chrome 20% Mo, Molybdenum 10% Niobium Niobium, a high density material, is very malleable and ductile. It is widely used in body jewelry. Platinum Platinum balls are widely used in high reliability electrical contacts. For this application, the platinum is alloyed with a small percentage of other elements. In the United States, it is usually alloyed with iridium; and in Europe, it is alloyed with nickel. These toughening and hardening metals have only a slight effect on the properties of the platinum. Platinum is the most noble of metals and is impervious to attack by most acids and bases. Platinum has one of the highest melting points of any metal (1768.3 C, 3214.9 F). As platinum is an expensive material, we do not maintain any platinum items in stock . Phenol Balls Bakelite Balls Phenol Formaldehyde Balls Unlike most other plastic balls, this material is a thermosetting plastic. This means that once this material has been heat cured in the mold, it will not melt again. You can raise the temperature of this plastic until it incinerates, but it will not melt. This material is much harder than any other commercially available plastic ball. It must be compression molded or catalyzed in a mold at high temperature, which makes it much more expensive than thermo plastics that can be injection molded. Ren 41 Ren 41 is an extremely tough high temperature nickel-chrome-molybdenum alloy. The machinability of this material is the very lowest of any commercially available alloy. But once the blank is machined, grinding and lapping are no problem. High quality balls can be produced from this material. Tantalum Balls / Tantalum Beads Tantalum balls or beads find frequent use as radiographic markers, because of their bio-compatibility. These balls can be implanted to form three dimensional markers for orthopedic evaluation after surgery. A ring of these radio graphically opaque markers are used at both ends of stints and shunts, providing a well defined address for the implanted devices. This material is used as an x-ray-opaque tracer in medical implants. An attached ball will define the position of a catheter. Tantalum is a very dense heavy metal (Ta) atomic weight is 180.947, density: 16.6g/cm^3. Unlike tungsten, it is very ductile and malleable. It will produce no reaction with either hydrochloric acid ( HCL) or nitric acid (HNO3). When Tantalum is implanted in a patient, it must be processed according to specification ASTM F560 (Medical Grade). See our sister site, www.tantalumbeads.com, for more information. See our shopping cart for available stock. Titanium Titanium Balls are made in two popular titanium materials. The first is basically pure titanium. This material, grade 2, is widely used in medical applications, where it is frequently used in body implants because it is very bio-compatible. The second, and by far the most frequently used alloy is 6AL4V (6 % Aluminum, 4% Vanadium) titanium. This alloy is available in a variety of wire and bar forms for easy processing into precision balls. Satin finished titanium balls are used as calibration devices for optical inspection devices. Titanium has an unusual hexagonal close-pack atomic structure, as contrasted with a face-centered or a body-centered cubic of most metallic elements. Tungsten Balls Tungsten has one of the highest melting points of any available metal. This is one of the heaviest metals. It is hard, tough, and non-magnetic. This metal is expensive and it is very difficult to machine, grind, or lap. Very high-quality balls can be produced from this material. Waspaloy Balls Waspaloy is one of the older exotic alloys used in high temperature applications. This material is very expensive and is only available in a limited number of shapes. Aluminum Oxide (Ceramic Ball) Aluminum Oxide is an almost white ceramic. Chemically it is Al2O3, also known as alumina balls or aloxite balls . This material is extremely hard. It has excellent electrical insulation properties. It is one of the least expensive and most widely used ceramic ball materials. It is very wear resistant, and it is very stiff with a young's modulus (YM) of elasticity of approximately 45,000,000 pounds per square inch. It can only be used in bearings at low speeds and very light loads. Star J and #3 are the alloys most frequently used for balls. They are very hard and wear-resistant. Silicon Nitride (Ceramic Ball) Silicon Nitride (Si3N4) ceramic has become the standard ceramic ball material for hybrid Ball Bearings. This material is very hard, over 2000 Knoop, and very wear resistant. The weight of silicon nitride balls is only 40% of steel at 3.2 grams per cm (cubic centimeter) . This material is hot isostatic pressed from 1 to 3 micro powder, has excellent fracture toughness even at elevated temperature, and ball quality as good as AFBMA grade-5 can be achieved on this material. Silicon nitride has excellent dielectric properties and extremely high resistivity (insulating properties). More Information For more information on engineering materials, see the site matweb.com .

The best possible aid to spark testing is to have balls of known materials to compare the sparks with. Break the spark into the three characteristics of color, length, and incineration (side sparks or bursts). Add the information regarding the hardness, magnetism and corrosion resistance and you will be able to nail down ninety five percent of the ball materials.

For bearings and ball screws with balls from 1/16" (.0625 inch, 1.59 mm) to 5/8" (.625 inch, 15.9 mm), A.F.B.M.A. grade-25 is a good commercial quality that is good enough for most commercial applications.

Request a ball grade chart, printed on plastic, from our office to better understand the quality and grade specifications and one will be sent to you free of charge. It is available as a download from our web site.

In valve and plumbing applications, much softer corrosive-resistant materials are often used. It is very expensive to produce the highest quality balls in these soft stainless steel and non-ferrous materials. The high quality balls in these materials are usually Grade 100 and good commercial quality balls are Grade 200. Call our office for technical assistance.

Type 1018 soft mild steel has a very low carbon content. This steel is not hard. It can be machined, drilled and tapped. This material is highly magnetic. It will be strongly attracted by a magnet. This is one of the most weldable steel alloys. Hardness is rated at 28 HRC.

17-4 PH is one of the family of precipitation hardened nickel based alloys. It combines high strength and good corrosion resistance with moderate hardness. It is hardened by soaking at an elevated temperature for a period of time.

The most common soaking temperature is 900 F. This heat treating is referred to as H-900. In the solution annealed condition, this material has moderately good machining properties. 15-5 PH is another of the common PH alloys.

If the application isn't too severe, type 316 stainless steel may be used. The 300 series stainless steels are basically an alloy of 18% chromium and 8% nickel with the balance ferrite (iron). This material is dead soft at about 30 HRC (Hardness Rockwell "C" scale), and is almost non magnetic in the annealed condition.

In pneumatic systems, there is usually water or water vapor present. To prevent rust, type 316 stainless steel is used. The spark test will yield only tiny red tracers. This material will not respond to any of the corrosion tests. It is almost non-magnetic. It is dead soft and the file test will put an immediate flat on the ball.

Type 420 hard stainless steel is the material widely used in Europe. It is very similar to type 440C, which is more widely used in the United States. Type 420 is not quite as hard as the type 440C. One of the advantages of 420 over type 440C is that it has a higher magnetic permeability, so that it is attracted more strongly by a magnetic field.

440C Stainless Steel is one of the most amazing standard ball materials. It is a very high chromium, high carbon, martensitic stainless steel. Martensite is the very hard state of a high carbon steel. When heat treated from the spherodize annealed condition, it forms an extremely fine grain structure. For hardening, it must be raised to 1900 F. It will harden to 58 - 63 HRC. It is usually at the low end of this range, when tempered at 400 F

If the bearing is used in a corrosive or wet environment, it may be a type 440C hard martensitic stainless steel. This material is very magnetic and it is hard, but it is not as hard as chrome steel. It is about 58 HRC (Hardness Rockwell "C" scale). This material is only mildly corrosive resistant and will only respond to corrosion tests with slight pitting. It will eventually corrode in tap water and will not stand up to sea water at all. It is widely used as a premium bearing material and it is the top material for use in gaging products. See our article, Stainless Steel Balls, Type 440C Hardened for more information.

1100 series aluminum is commercially pure aluminum. It is a very light weight material that is a silvery white color, one of the natural base elements, and very ductile. Balls made of 1100 series aluminum are often used as closures. They are squashed or upset to permanently close a hole (an inside diameter). It is difficult to locate this material in less than mill-run quantities.

2017 aluminum is a copper alloy of aluminum that was originally developed for the manufacture of rivets. Its number one quality is that it can be safely cold-headed, which makes it an excellent choice as a material for precision balls. This is the aluminum alloy specified by Mil-B-1083, the generally accepted military specification for precision balls. This alloy has also been chosen by the AFBMA (Anti Friction Bearing Manufacturers Association as a standard ball material. This material is usually heat treated to the "T4" condition. This is not a good choice if the ball is to be anodized. High quality balls can be produced from this alloy.

2024 aluminum alloy is an aluminum copper alloy. It is a high strength material, widely used in aircraft. It can be cold headed. The tensile strength of this alloy can be improved by heat treating. This alloy is not a good choice for hard anodizing as the segregation of copper will form voids and can even cause incineration of the metal during the anodizing process.

6061 Aluminum alloy is a widely used, readily available, aluminum material. This material should never be cold headed--it can develop internal fissures that will lead to catastrophic failure. This alloy has much better machining qualities than 2017 alloy. This alloy is an excellent choice when the balls are to be hard anodized. The tensile strength of this alloy can be improved by heat treating. This aluminum alloy is relatively light at 0.098 lbs/ cu in.

It is very slightly magnetic. An aluminum bronze ball will roll towards a powerful magnet. This material is very resistant to sea water. Some alloys of this material can be heat treated to increase its hardness and tensile strength, but the hardening process reduces corrosive resistance. It is a very good electrical conductor.

A286 is one of the exotic Space Age materials. It has good wear properties. It is corrosion resistant. This material must be heat treated to develop its best physical properties. This material is very expensive. Very high quality balls can be produced from this material.

High quality steel balls of both chrome steel and hard stainless steel can be treated chemically to color the surface black. This black iron phosphate actually penetrates the surface so that the original size and surface quality is not affected. The most common application for this surface treatment is to provide identity for these balls. In some bearing and ball screw applications, two different size balls are used in the same device. The larger diameter balls are load bearing balls, and the smaller diameter black balls are used as spacer balls.

We manufacture and stock a large variety of brass balls. Brass balls are gold or bright yellow in color. The Standard alloy is 70-30, which is 70% copper and 30% zinc. The only major problem with the metallurgy of brass is segregation. This is due to the high melting point of copper (3000 F) and the low melting point of zinc (800 F). This material is quite ductile and very malleable. It is corrosive resistant to tap water, but does not stand up well in sea water. It is nonmagnetic, an excellent electrical conductor, and has excellent solder ability with soft solder, but may require chemical cleaning to remove an oxide layer. Brass has a hardness of less than 30 HRC, is very machinable, and it may be drilled and tapped easily. Brass is a relatively heavy material at .275 - .316 lbs/cu in (7.60 - 8.75 g / cc).

Naval Brass or Naval Bronze is very similar to brass, but has an addition of 0.5% to 1.0% tin. This small addition gives to material good corrosive resistance to sea water.Naval brass or bronze is a relatively heavy material at .305 lbs/ cu in. We will custom manufacture special alloys if the material is commercially available. Brass balls are precision ground and polished. They can be produced to AFBMA standards when required. We produce brass balls in all sizes from the sub-miniature to very large diameters.

We manufacture copper balls in the entire range of sizes from sub-miniature to several inches in diameter. Pure copper, as well as the many copper alloys, can be used to produce highly accurate precision balls.

Copper, usually oxygen free, has excellent electrical and heat conductivity, as well as good corrosion resistance in many harsh environments. It is nonmagnetic. It is sometimes annealed after all forming and machining is completed, to enhance its electrical properties. It is extremely malleable and ductile. It is very soft, but it is gummy and very difficult to machine, tending to gall easily. It is very solderable, and it is very corrosive resistant to sea water. Copper has a distinctly red color.

Diamond-impregnated balls are used to lap the spherical radius in ball valves. They usually have a stem or handle attached to facilitate holding during the lapping process. See our Diamond Impregnated Ball Lap page for more information.

An obvious use for gold is for jewelry. The nobility of gold meaning its resistance to corrosion and its good electrical conductivity leads to use in electrical applications. Gold has a high level of x-ray opacity and good bio-compatibility, which leads to its use as x-ray markers in medical applications. As gold is such an expensive material, we do not maintain a stock of gold balls.

Hevimet is usually sintered from powdered tungsten and powdered copper. Its very heavy weight makes it an alternative to lead in some uses. It is machinable, and unlike lead it is biologically safe. Ball's made of this material are used as counter-weights, and to add mass to mechanical structures.

High speed steel such as M50 and M10 or T15 are usually reserved for hot end bearings and high temperature ball screw applications. These materials are not corrosive resistant and will react to any of the corrosive tests. These materials are very hard. They will test up to 65 HRC. They will be strongly attracted by a magnet.

Inconel 7-18 is truly an aerospace metal. Inconel is hard and strong. It will continue to perform at high temperatures. It will also perform at temperatures so cold that hydrogen is a liquid. These low temperatures are so cold that there is a special word for it, cryogenic.

The highest quality is required for these aerospace oriented balls. In many cases, every single individual ball must have its own pedigree accompanying it. This will include the physical and chemical analysis of the individual bar of material, an ultrasonic examination, and the heat treating process that was performed on it. Along with this will be the diameter of the ball on three orthogonal axii and three polar charts of the roundness taken on three orthogonal axii.

A rocket engine using inconel balls depends on the integrity of each individual ball, making them crucial parts of the rocket engine. In addition, Inconel is highly corrosive resistant. It is precipitation hardened. This metal alloy must be heat-treated to develop its good physical properties. Care should be exercised in specifying the desired heat treatment as the furnace time for some processes may be very long and therefore, very expensive.

There are a number of different Monel alloys, a trademark of Special Metals Corp.. The basic alloy has a minimum of 23% copper and minimum of 60% nickel with small amounts of iron and manganese. This material is very tough but not very hard. It is not heat treatable. Monel is used in very corrosive environments. It is excellent in salt water applications such as valves for sea water. It is also used in the food processing industry.

We make Monel balls in a wide range of sizes. Due to its relatively soft nature, AFBMA grade 200 is the normal quality specification, although grade 100 can be achieved with some difficulty. It is relatively soft at about 38 HRC, and it is difficult to drill and tap.

MP35N finds use for check valve applications where no other metal could ever survive. In down hole control valves where the chemistry of the environment would eat a stainless steel ball, balls made of this material will last indefinitely.

This material is so tough that producing precision balls from it is a major problem. It cannot be cold headed at all. The forging temperatures are extreme. Like many of the exotic metals, MP35N can be lapped to a very high level of quality, once the spherical blank has been produced.

Platinum balls are widely used in high reliability electrical contacts. For this application, the platinum is alloyed with a small percentage of other elements. In the United States, it is usually alloyed with iridium; and in Europe, it is alloyed with nickel. These toughening and hardening metals have only a slight effect on the properties of the platinum. Platinum is the most noble of metals and is impervious to attack by most acids and bases. Platinum has one of the highest melting points of any metal (1768.3 C, 3214.9 F).

Unlike most other plastic balls, this material is a thermosetting plastic. This means that once this material has been heat cured in the mold, it will not melt again. You can raise the temperature of this plastic until it incinerates, but it will not melt. This material is much harder than any other commercially available plastic ball.

Ren 41 is an extremely tough high temperature nickel-chrome-molybdenum alloy. The machinability of this material is the very lowest of any commercially available alloy. But once the blank is machined, grinding and lapping are no problem. High quality balls can be produced from this material.

Tantalum balls or beads find frequent use as radiographic markers, because of their bio-compatibility. These balls can be implanted to form three dimensional markers for orthopedic evaluation after surgery. A ring of these radio graphically opaque markers are used at both ends of stints and shunts, providing a well defined address for the implanted devices. This material is used as an x-ray-opaque tracer in medical implants. An attached ball will define the position of a catheter. Tantalum is a very dense heavy metal (Ta) atomic weight is 180.947, density: 16.6g/cm^3. Unlike tungsten, it is very ductile and malleable. It will produce no reaction with either hydrochloric acid ( HCL) or nitric acid (HNO3). When Tantalum is implanted in a patient, it must be processed according to specification ASTM F560 (Medical Grade).

Titanium Balls are made in two popular titanium materials. The first is basically pure titanium. This material, grade 2, is widely used in medical applications, where it is frequently used in body implants because it is very bio-compatible. The second, and by far the most frequently used alloy is 6AL4V (6 % Aluminum, 4% Vanadium) titanium. This alloy is available in a variety of wire and bar forms for easy processing into precision balls. Satin finished titanium balls are used as calibration devices for optical inspection devices.

Tungsten has one of the highest melting points of any available metal. This is one of the heaviest metals. It is hard, tough, and non-magnetic. This metal is expensive and it is very difficult to machine, grind, or lap. Very high-quality balls can be produced from this material.

Aluminum Oxide is an almost white ceramic. Chemically it is Al2O3, also known as alumina balls or aloxite balls . This material is extremely hard. It has excellent electrical insulation properties. It is one of the least expensive and most widely used ceramic ball materials. It is very wear resistant, and it is very stiff with a young's modulus (YM) of elasticity of approximately 45,000,000 pounds per square inch. It can only be used in bearings at low speeds and very light loads. Star J and #3 are the alloys most frequently used for balls. They are very hard and wear-resistant.

Silicon Nitride (Si3N4) ceramic has become the standard ceramic ball material for hybrid Ball Bearings. This material is very hard, over 2000 Knoop, and very wear resistant. The weight of silicon nitride balls is only 40% of steel at 3.2 grams per cm (cubic centimeter) .

This material is hot isostatic pressed from 1 to 3 micro powder, has excellent fracture toughness even at elevated temperature, and ball quality as good as AFBMA grade-5 can be achieved on this material. Silicon nitride has excellent dielectric properties and extremely high resistivity (insulating properties).

ball mill liners selection and design | ball mill rubber liner

ball mill liners selection and design | ball mill rubber liner

The ball mill liners are located on the inner surface of the ball mill barrel, which protects the barrel from the direct impact and friction of the grinding media and the material. The ball mill liners material and shape are different which base on requirements. When the grinding media contacts with different shape of ball mill liners, the movement state will also change, thus enhancing the crushing effect on the material. This design of the mill liners effectively improves the grinding efficiency of the ball mill machine, increases production, and reduces metal consumption.

The grinding mill liners are the main wearing part of the ball mill equipment. The ball mill liner replacement should in time when the lining plate is excessively worn. Therefore, the selection and design of mill liners have always been of great concern to users.

As one of professional ball mill liners manufacturers, we summarize the main functions of the three-point ball mill liners. It mainly involves the protection of the barrel and the control of the grinding medium.

The mill liner is installed inside the ball mill barrel, separating the grinding media from the barrel, effectively buffering the direct impact of the grinding media on the barrel. Therefore, the barrel is protected, and the service life of the barrel and the entire ball mill equipment is prolonged. The ball mill liners are embedded with the barrel, and at the same time, the rigidity of the barrel is enhanced.

Due to the special shape of the grinding mill liner surface, the grinding media contacts the grinding mill liners, and the huge friction force drives the steel ball upward. The steel ball is lifted to a certain height and dropped, while impacting and grinding materials.

Angle spiral grinding mill liner and cone classification liner have automatic classification function, which can make grinding media of different quality in the cylinder carry out reasonable forward classification along the axial direction of the mill and the change of material size. The automatic grading ball mill liners enable the larger steel balls in the barrel to be concentrated at the feed end to crush larger materials, while the smaller steel balls are concentrated at the discharge end to crush smaller materials.

Different ball mill equipment is suitable for different grinding materials, and the type of grinding mill liners selected will also be different. For example, is the rod mill liners the same as the sag mill liner design? Which type of cement mill liner should be used to grind cement in order to reduce the frequency of ball mill liner replacement as much as possible?

According to the material classification, the common ball mill liners mainly include high manganese steel mill liners, alloy steel mill liners, rubber mill liners, ceramic mill liners and magnetic mill liners.

The mainstream ball mill liners materials currently used in the market are alloy steel and rubber. Alloy steel mill liner is wear-resistant and impact-resistant. Alloy steel has good physical and chemical properties due to its alloy properties, and its service life is more than twice that of high-manganese steel. The ball mill rubber liner has a high wear resistance index, high rebound rate, and high abrasion resistance and tear strength. It also has the advantage of reducing noise.

According to different grinding requirements, ball mill liners are roughly divided into 9 types, which are wedge-shaped, corrugated, flat-convex, flat, stepped, elongated, rudder-shaped, K-shaped ball mill rubber liner and B-shaped ball mill rubber liner. These 9 kinds of grinding mill liners can be classified into two categories: smooth grinding mill liner and unsmooth grinding mill liner.

The smooth grinding mill liner has a large sliding property, has a strong grinding effect, and is suitable for fine grinding processes. The friction of the unsmoothed grinding mill liner is large, which can improve the material and steel ball very well, and has strong agitation effect, so it is more suitable for rough grinding process.

As a ball mills supplier with 22 years of experience in the grinding industry, we can provide customers with types of ball mill, vertical mill, rod mill and AG/SAG mill for grinding in a variety of industries and materials.

ball mill - an overview | sciencedirect topics

ball mill - an overview | sciencedirect topics

The ball mill accepts the SAG or AG mill product. Ball mills give a controlled final grind and produce flotation feed of a uniform size. Ball mills tumble iron or steel balls with the ore. The balls are initially 510 cm diameter but gradually wear away as grinding of the ore proceeds. The feed to ball mills (dry basis) is typically 75 vol.-% ore and 25% steel.

The ball mill is operated in closed circuit with a particle-size measurement device and size-control cyclones. The cyclones send correct-size material on to flotation and direct oversize material back to the ball mill for further grinding.

Grinding elements in ball mills travel at different velocities. Therefore, collision force, direction and kinetic energy between two or more elements vary greatly within the ball charge. Frictional wear or rubbing forces act on the particles, as well as collision energy. These forces are derived from the rotational motion of the balls and movement of particles within the mill and contact zones of colliding balls.

By rotation of the mill body, due to friction between mill wall and balls, the latter rise in the direction of rotation till a helix angle does not exceed the angle of repose, whereupon, the balls roll down. Increasing of rotation rate leads to growth of the centrifugal force and the helix angle increases, correspondingly, till the component of weight strength of balls become larger than the centrifugal force. From this moment the balls are beginning to fall down, describing during falling certain parabolic curves (Figure 2.7). With the further increase of rotation rate, the centrifugal force may become so large that balls will turn together with the mill body without falling down. The critical speed n (rpm) when the balls are attached to the wall due to centrifugation:

where Dm is the mill diameter in meters. The optimum rotational speed is usually set at 6580% of the critical speed. These data are approximate and may not be valid for metal particles that tend to agglomerate by welding.

The degree of filling the mill with balls also influences productivity of the mill and milling efficiency. With excessive filling, the rising balls collide with falling ones. Generally, filling the mill by balls must not exceed 3035% of its volume.

The mill productivity also depends on many other factors: physical-chemical properties of feed material, filling of the mill by balls and their sizes, armor surface shape, speed of rotation, milling fineness and timely moving off of ground product.

where b.ap is the apparent density of the balls; l is the degree of filling of the mill by balls; n is revolutions per minute; 1, and 2 are coefficients of efficiency of electric engine and drive, respectively.

A feature of ball mills is their high specific energy consumption; a mill filled with balls, working idle, consumes approximately as much energy as at full-scale capacity, i.e. during grinding of material. Therefore, it is most disadvantageous to use a ball mill at less than full capacity.

The ball mill is a tumbling mill that uses steel balls as the grinding media. The length of the cylindrical shell is usually 11.5 times the shell diameter (Figure 8.11). The feed can be dry, with less than 3% moisture to minimize ball coating, or slurry containing 2040% water by weight. Ball mills are employed in either primary or secondary grinding applications. In primary applications, they receive their feed from crushers, and in secondary applications, they receive their feed from rod mills, AG mills, or SAG mills.

Ball mills are filled up to 40% with steel balls (with 3080mm diameter), which effectively grind the ore. The material that is to be ground fills the voids between the balls. The tumbling balls capture the particles in ball/ball or ball/liner events and load them to the point of fracture.

When hard pebbles rather than steel balls are used for the grinding media, the mills are known as pebble mills. As mentioned earlier, pebble mills are widely used in the North American taconite iron ore operations. Since the weight of pebbles per unit volume is 3555% of that of steel balls, and as the power input is directly proportional to the volume weight of the grinding medium, the power input and capacity of pebble mills are correspondingly lower. Thus, in a given grinding circuit, for a certain feed rate, a pebble mill would be much larger than a ball mill, with correspondingly a higher capital cost. However, the increase in capital cost is justified economically by a reduction in operating cost attributed to the elimination of steel grinding media.

In general, ball mills can be operated either wet or dry and are capable of producing products in the order of 100m. This represents reduction ratios of as great as 100. Very large tonnages can be ground with these ball mills because they are very effective material handling devices. Ball mills are rated by power rather than capacity. Today, the largest ball mill in operation is 8.53m diameter and 13.41m long with a corresponding motor power of 22MW (Toromocho, private communications).

Planetary ball mills. A planetary ball mill consists of at least one grinding jar, which is arranged eccentrically on a so-called sun wheel. The direction of movement of the sun wheel is opposite to that of the grinding jars according to a fixed ratio. The grinding balls in the grinding jars are subjected to superimposed rotational movements. The jars are moved around their own axis and, in the opposite direction, around the axis of the sun wheel at uniform speed and uniform rotation ratios. The result is that the superimposition of the centrifugal forces changes constantly (Coriolis motion). The grinding balls describe a semicircular movement, separate from the inside wall, and collide with the opposite surface at high impact energy. The difference in speeds produces an interaction between frictional and impact forces, which releases high dynamic energies. The interplay between these forces produces the high and very effective degree of size reduction of the planetary ball mill. Planetary ball mills are smaller than common ball mills, and are mainly used in laboratories for grinding sample material down to very small sizes.

Vibration mill. Twin- and three-tube vibrating mills are driven by an unbalanced drive. The entire filling of the grinding cylinders, which comprises the grinding media and the feed material, constantly receives impulses from the circular vibrations in the body of the mill. The grinding action itself is produced by the rotation of the grinding media in the opposite direction to the driving rotation and by continuous head-on collisions of the grinding media. The residence time of the material contained in the grinding cylinders is determined by the quantity of the flowing material. The residence time can also be influenced by using damming devices. The sample passes through the grinding cylinders in a helical curve and slides down from the inflow to the outflow. The high degree of fineness achieved is the result of this long grinding procedure. Continuous feeding is carried out by vibrating feeders, rotary valves, or conveyor screws. The product is subsequently conveyed either pneumatically or mechanically. They are basically used to homogenize food and feed.

CryoGrinder. As small samples (100 mg or <20 ml) are difficult to recover from a standard mortar and pestle, the CryoGrinder serves as an alternative. The CryoGrinder is a miniature mortar shaped as a small well and a tightly fitting pestle. The CryoGrinder is prechilled, then samples are added to the well and ground by a handheld cordless screwdriver. The homogenization and collection of the sample is highly efficient. In environmental analysis, this system is used when very small samples are available, such as small organisms or organs (brains, hepatopancreas, etc.).

The vibratory ball mill is another kind of high-energy ball mill that is used mainly for preparing amorphous alloys. The vials capacities in the vibratory mills are smaller (about 10 ml in volume) compared to the previous types of mills. In this mill, the charge of the powder and milling tools are agitated in three perpendicular directions (Fig. 1.6) at very high speed, as high as 1200 rpm.

Another type of the vibratory ball mill, which is used at the van der Waals-Zeeman Laboratory, consists of a stainless steel vial with a hardened steel bottom, and a single hardened steel ball of 6 cm in diameter (Fig. 1.7).

The mill is evacuated during milling to a pressure of 106 Torr, in order to avoid reactions with a gas atmosphere.[44] Subsequently, this mill is suitable for mechanical alloying of some special systems that are highly reactive with the surrounding atmosphere, such as rare earth elements.

A ball mill is a relatively simple apparatus in which the motion of the reactor, or of a part of it, induces a series of collisions of balls with each other and with the reactor walls (Suryanarayana, 2001). At each collision, a fraction of the powder inside the reactor is trapped between the colliding surfaces of the milling tools and submitted to a mechanical load at relatively high strain rates (Suryanarayana, 2001). This load generates a local nonhydrostatic mechanical stress at every point of contact between any pair of powder particles. The specific features of the deformation processes induced by these stresses depend on the intensity of the mechanical stresses themselves, on the details of the powder particle arrangement, that is on the topology of the contact network, and on the physical and chemical properties of powders (Martin et al., 2003; Delogu, 2008a). At the end of any given collision event, the powder that has been trapped is remixed with the powder that has not undergone this process. Correspondingly, at any instant in the mechanical processing, the whole powder charge includes fractions of powder that have undergone a different number of collisions.

The individual reactive processes at the perturbed interface between metallic elements are expected to occur on timescales that are, at most, comparable with the collision duration (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b). Therefore, unless the ball mill is characterized by unusually high rates of powder mixing and frequency of collisions, reactive events initiated by local deformation processes at a given collision are not affected by a successive collision. Indeed, the time interval between successive collisions is significantly longer than the time period required by local structural perturbations for full relaxation (Hammerberg et al., 1998; Urakaev and Boldyrev, 2000; Lund and Schuh, 2003; Delogu and Cocco, 2005a,b).

These few considerations suffice to point out the two fundamental features of powder processing by ball milling, which in turn govern the MA processes in ball mills. First, mechanical processing by ball milling is a discrete processing method. Second, it has statistical character. All of this has important consequences for the study of the kinetics of MA processes. The fact that local deformation events are connected to individual collisions suggests that absolute time is not an appropriate reference quantity to describe mechanically induced phase transformations. Such a description should rather be made as a function of the number of collisions (Delogu et al., 2004). A satisfactory description of the MA kinetics must also account for the intrinsic statistical character of powder processing by ball milling. The amount of powder trapped in any given collision, at the end of collision is indeed substantially remixed with the other powder in the reactor. It follows that the same amount, or a fraction of it, could at least in principle be trapped again in the successive collision.

This is undoubtedly a difficult aspect to take into account in a mathematical description of MA kinetics. There are at least two extreme cases to consider. On the one hand, it could be assumed that the powder trapped in a given collision cannot be trapped in the successive one. On the other, it could be assumed that powder mixing is ideal and that the amount of powder trapped at a given collision has the same probability of being processed in the successive collision. Both these cases allow the development of a mathematical model able to describe the relationship between apparent kinetics and individual collision events. However, the latter assumption seems to be more reliable than the former one, at least for commercial mills characterized by relatively complex displacement in the reactor (Manai et al., 2001, 2004).

A further obvious condition for the successful development of a mathematical description of MA processes is the one related to the uniformity of collision regimes. More specifically, it is highly desirable that the powders trapped at impact always experience the same conditions. This requires the control of the ball dynamics inside the reactor, which can be approximately obtained by using a single milling ball and an amount of powder large enough to assure inelastic impact conditions (Manai et al., 2001, 2004; Delogu et al., 2004). In fact, the use of a single milling ball avoids impacts between balls, which have a remarkable disordering effect on the ball dynamics, whereas inelastic impact conditions permit the establishment of regular and periodic ball dynamics (Manai et al., 2001, 2004; Delogu et al., 2004).

All of the above assumptions and observations represent the basis and guidelines for the development of the mathematical model briefly outlined in the following. It has been successfully applied to the case of a Spex Mixer/ Mill mod. 8000, but the same approach can, in principle, be used for other ball mills.

The Planetary ball mills are the most popular mills used in MM, MA, and MD scientific researches for synthesizing almost all of the materials presented in Figure 1.1. In this type of mill, the milling media have considerably high energy, because milling stock and balls come off the inner wall of the vial (milling bowl or vial) and the effective centrifugal force reaches up to 20 times gravitational acceleration.

The centrifugal forces caused by the rotation of the supporting disc and autonomous turning of the vial act on the milling charge (balls and powders). Since the turning directions of the supporting disc and the vial are opposite, the centrifugal forces alternately are synchronized and opposite. Therefore, the milling media and the charged powders alternatively roll on the inner wall of the vial, and are lifted and thrown off across the bowl at high speed, as schematically presented in Figure 2.17.

However, there are some companies in the world who manufacture and sell number of planetary-type ball mills; Fritsch GmbH (www.fritsch-milling.com) and Retsch (http://www.retsch.com) are considered to be the oldest and principal companies in this area.

Fritsch produces different types of planetary ball mills with different capacities and rotation speeds. Perhaps, Fritsch Pulverisette P5 (Figure 2.18(a)) and Fritsch Pulverisette P6 (Figure 2.18(b)) are the most popular models of Fritsch planetary ball mills. A variety of vials and balls made of different materials with different capacities, starting from 80ml up to 500ml, are available for the Fritsch Pulverisette planetary ball mills; these include tempered steel, stainless steel, tungsten carbide, agate, sintered corundum, silicon nitride, and zirconium oxide. Figure 2.19 presents 80ml-tempered steel vial (a) and 500ml-agate vials (b) together with their milling media that are made of the same materials.

Figure 2.18. Photographs of Fritsch planetary-type high-energy ball mill of (a) Pulverisette P5 and (b) Pulverisette P6. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).

Figure 2.19. Photographs of the vials used for Fritsch planetary ball mills with capacity of (a) 80ml and (b) 500ml. The vials and the balls shown in (a) and (b) are made of tempered steel agate materials, respectively (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).

More recently and in year 2011, Fritsch GmbH (http://www.fritsch-milling.com) introduced a new high-speed and versatile planetary ball mill called Planetary Micro Mill PULVERISETTE 7 (Figure 2.20). The company claims this new ball mill will be helpful to enable extreme high-energy ball milling at rotational speed reaching to 1,100rpm. This allows the new mill to achieve sensational centrifugal accelerations up to 95 times Earth gravity. They also mentioned that the energy application resulted from this new machine is about 150% greater than the classic planetary mills. Accordingly, it is expected that this new milling machine will enable the researchers to get their milled powders in short ball-milling time with fine powder particle sizes that can reach to be less than 1m in diameter. The vials available for this new type of mill have sizes of 20, 45, and 80ml. Both the vials and balls can be made of the same materials, which are used in the manufacture of large vials used for the classic Fritsch planetary ball mills, as shown in the previous text.

Retsch has also produced a number of capable high-energy planetary ball mills with different capacities (http://www.retsch.com/products/milling/planetary-ball-mills/); namely Planetary Ball Mill PM 100 (Figure 2.21(a)), Planetary Ball Mill PM 100 CM, Planetary Ball Mill PM 200, and Planetary Ball Mill PM 400 (Figure 2.21(b)). Like Fritsch, Retsch offers high-quality ball-milling vials with different capacities (12, 25, 50, 50, 125, 250, and 500ml) and balls of different diameters (540mm), as exemplified in Figure 2.22. These milling tools can be made of hardened steel as well as other different materials such as carbides, nitrides, and oxides.

Figure 2.21. Photographs of Retsch planetary-type high-energy ball mill of (a) PM 100 and (b) PM 400. The equipment is housed in the Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR).

Figure 2.22. Photographs of the vials used for Retsch planetary ball mills with capacity of (a) 80ml, (b) 250ml, and (c) 500ml. The vials and the balls shown are made of tempered steel (Nanotechnology Laboratory, Energy and Building Research Center (EBRC), Kuwait Institute for Scientific Research (KISR)).

Both Fritsch and Retsch companies have offered special types of vials that allow monitoring and measure the gas pressure and temperature inside the vial during the high-energy planetary ball-milling process. Moreover, these vials allow milling the powders under inert (e.g., argon or helium) or reactive gas (e.g., hydrogen or nitrogen) with a maximum gas pressure of 500kPa (5bar). It is worth mentioning here that such a development made on the vials design allows the users and researchers to monitor the progress tackled during the MA and MD processes by following up the phase transformations and heat realizing upon RBM, where the interaction of the gas used with the freshly created surfaces of the powders during milling (adsorption, absorption, desorption, and decomposition) can be monitored. Furthermore, the data of the temperature and pressure driven upon using this system is very helpful when the ball mills are used for the formation of stable (e.g., intermetallic compounds) and metastable (e.g., amorphous and nanocrystalline materials) phases. In addition, measuring the vial temperature during blank (without samples) high-energy ball mill can be used as an indication to realize the effects of friction, impact, and conversion processes.

More recently, Evico-magnetics (www.evico-magnetics.de) has manufactured an extraordinary high-pressure milling vial with gas-temperature-monitoring (GTM) system. Likewise both system produced by Fritsch and Retsch, the developed system produced by Evico-magnetics, allowing RBM but at very high gas pressure that can reach to 15,000kPa (150bar). In addition, it allows in situ monitoring of temperature and of pressure by incorporating GTM. The vials, which can be used with any planetary mills, are made of hardened steel with capacity up to 220ml. The manufacturer offers also two-channel system for simultaneous use of two milling vials.

Using different ball mills as examples, it has been shown that, on the basis of the theory of glancing collision of rigid bodies, the theoretical calculation of tPT conditions and the kinetics of mechanochemical processes are possible for the reactors that are intended to perform different physicochemical processes during mechanical treatment of solids. According to the calculations, the physicochemical effect of mechanochemical reactors is due to short-time impulses of pressure (P = ~ 10101011 dyn cm2) with shift, and temperature T(x, t). The highest temperature impulse T ~ 103 K are caused by the dry friction phenomenon.

Typical spatial and time parameters of the impactfriction interaction of the particles with a size R ~ 104 cm are as follows: localization region, x ~ 106 cm; time, t ~ 108 s. On the basis of the obtained theoretical results, the effect of short-time contact fusion of particles treated in various comminuting devices can play a key role in the mechanism of activation and chemical reactions for wide range of mechanochemical processes. This role involves several aspects, that is, the very fact of contact fusion transforms the solid phase process onto another qualitative level, judging from the mass transfer coefficients. The spatial and time characteristics of the fused zone are such that quenching of non-equilibrium defects and intermediate products of chemical reactions occurs; solidification of the fused zone near the contact point results in the formation of a nanocrystal or nanoamor- phous state. The calculation models considered above and the kinetic equations obtained using them allow quantitative ab initio estimates of rate constants to be performed for any specific processes of mechanical activation and chemical transformation of the substances in ball mills.

There are two classes of ball mills: planetary and mixer (also called swing) mill. The terms high-speed vibration milling (HSVM), high-speed ball milling (HSBM), and planetary ball mill (PBM) are often used. The commercial apparatus are PBMs Fritsch P-5 and Fritsch Pulverisettes 6 and 7 classic line, the Retsch shaker (or mixer) mills ZM1, MM200, MM400, AS200, the Spex 8000, 6750 freezer/mill SPEX CertiPrep, and the SWH-0.4 vibrational ball mill. In some instances temperature controlled apparatus were used (58MI1); freezer/mills were used in some rare cases (13MOP1824).

The balls are made of stainless steel, agate (SiO2), zirconium oxide (ZrO2), or silicon nitride (Si3N). The use of stainless steel will contaminate the samples with steel particles and this is a problem both for solid-state NMR and for drug purity.

However, there are many types of ball mills (see Chapter 2 for more details), such as drum ball mills, jet ball mills, bead-mills, roller ball mills, vibration ball mills, and planetary ball mills, they can be grouped or classified into two types according to their rotation speed, as follows: (i) high-energy ball mills and (ii) low-energy ball mills. Table 3.1 presents characteristics and comparison between three types of ball mills (attritors, vibratory mills, planetary ball mills and roller mills) that are intensively used on MA, MD, and MM techniques.

In fact, choosing the right ball mill depends on the objectives of the process and the sort of materials (hard, brittle, ductile, etc.) that will be subjecting to the ball-milling process. For example, the characteristics and properties of those ball mills used for reduction in the particle size of the starting materials via top-down approach, or so-called mechanical milling (MM process), or for mechanically induced solid-state mixing for fabrications of composite and nanocomposite powders may differ widely from those mills used for achieving mechanically induced solid-state reaction (MISSR) between the starting reactant materials of elemental powders (MA process), or for tackling dramatic phase transformation changes on the structure of the starting materials (MD). Most of the ball mills in the market can be employed for different purposes and for preparing of wide range of new materials.

Martinez-Sanchez et al. [4] have pointed out that employing of high-energy ball mills not only contaminates the milled amorphous powders with significant volume fractions of impurities that come from milling media that move at high velocity, but it also affects the stability and crystallization properties of the formed amorphous phase. They have proved that the properties of the formed amorphous phase (Mo53Ni47) powder depends on the type of the ball-mill equipment (SPEX 8000D Mixer/Mill and Zoz Simoloter mill) used in their important investigations. This was indicated by the high contamination content of oxygen on the amorphous powders prepared by SPEX 8000D Mixer/Mill, when compared with the corresponding amorphous powders prepared by Zoz Simoloter mill. Accordingly, they have attributed the poor stabilities, indexed by the crystallization temperature of the amorphous phase formed by SPEX 8000D Mixer/Mill to the presence of foreign matter (impurities).

ball mill liners material selection and application

ball mill liners material selection and application

The ball mill liners and grinding media are the largest consumption of wear-resistant iron and steel parts with an annual consumption of 2 million tons in China. With the development of Chinas economic construction, the demand for cement is increasing year by year, and the consumption of wear-resistant materials is also increasing correspondingly, which will consume more metals and increase the production cost of cement. For the cement with special requirements (such as white cement), the quality of cement will be reduced, and the production can not be carried out smoothly. According to the cement output in 2003, more than 60000 tons of high-quality wear-resistant steel are needed for mill liners only. Moreover, the materials used for lining board production in China are uneven, and the actual consumption can be nearly 100000 tons. According to the characteristics of the cement industry, this paper carefully analyzes the working environment and wear failure reasons of cylinder liner, studies and selects ball mill liners material, and carries out production application.

The main function of the ball mill liner is to protect the mill and use the convex peak of the liner to play the ball to grind and crush the material. Therefore, the main failure mode of the liner is abrasive wear under the repeated impact of small energy. Fig. 1 shows the motion diagram of grinding ball and material. In the movement of grinding bodies and materials, the grinding balls with large diameters are mainly distributed in the outer ring. Most of the grinding balls fall on the bottom of the material bed and only a small part on the liner plate. Due to the buffering effect of materials and the mutual impact between the materials and the grinding body, the running track of the grinding body is disturbed, and the falling point deviates, and the falling height is reduced. As a result, the impact of the abrasive body on the liner is greatly reduced, the impact times and the impact frequency are increased.

The impact of the grinding ball on the ball mill liner is shown in Fig. 2. The impact point diameter D0 of the ball mill is smaller than the effective diameter D of the mill. Through analyses, it is determined that most of the grinding bodies in the bin only hit the lining plate after several times of impact and folding. Therefore, the impact on the lining plate is far less than the impact energy produced by the vertical falling object of 0.95 D (usually the thickness of the lining plate accounts for 0.5 % of the effective diameter).

Figure 3 shows the relative position of grinding balls. When the ball is brought down to a certain height by the rotating ball mill liner, only when x > R1 + R2, the movement direction V0 of Q1 will not change and form a direct impact on the liner; when x = R1 + R2, Q1 and Q2 pass each other, and the movement direction V0 of Q1 will not change greatly, However, a small amount of friction will reduce the impact on the liner, and most of the cases of x < R1 + R2 will not form a direct impact on the liner.

The main force of liner fracture caused by the impact of the abrasive body on the liner is the vertical component of tangential force between the surface of the liner and the contact point of the abrasive body. The size of this force is affected by the shape of liner; the movement state, speed, and direction of the abrasive body, which greatly weakens the strength of direct connection and improves the impact degree of the liner.

In order to improve the service life of the liner, reduce the material consumption and production cost, it is very important to carry out reasonable structural design under the condition of meeting the requirements of the cement grinding process. The large mill imported by Jidong Cement Company, Hebei Taihang Cement Company, and other units has small lining plate size, large plate thickness and bolt free installation, which lays a good design foundation for the application of high hardness materials to lining plate, and makes it possible to greatly increase the service life of lining plate. At present, the design basis of high manganese steel is still used in the lining plate of ball mill in China. From the geometric structure, it is usually thin and large, and there is obvious stress concentration at the bolt installation hole. In order to ensure the stable application of the new type of wear-resistant casting material and give full play to its unique advantages, this point must be taken into account when adopting new high wear-resistant casting materials.

In addition, the installation quality also plays an extremely important role in the reliable service of high hardness materials. After a long time of experimental exploration, it is found that for the application of casting materials with high hardness and high wear resistance, the supplier and application unit of lining plate should cooperate well, so that the user can better understand the characteristics of the new material, and the lining plate can not be suspended or loosened during installation And can get a certain cushion effect. This is easy to do in the installation process of cement mill, which can effectively ensure the good wear resistance of the lining plate.

Up to now, nearly half of the lining materials of ball mill in the domestic cement industry are still made of ordinary high manganese steel. The main failure modes of high manganese steel ball mill liners are as follows:

Fracture failure: the ball mill liner is greatly impacted by the grinding body and materials, especially in the situation of large-scale development of high-efficiency and energy-saving cement mill, the impact energy of lining plate increases. Although the toughness of high manganese steel is very good, the current supply quality can not be guaranteed very well, for example, the carbon content is too high, the manganese carbon ratio is improper, and the water toughening treatment has problems, the fracture failure will occur.

Protrusion deformation: the volume of high manganese steel liner is increased due to the continuous impact of abrasives and materials. At the same time, due to the extension of plastic materials caused by impact, the thickness of mill liner decreases, and the circumferential dimension increases. However, the circumferential dimension of the liner is limited by the overall dimension of the ball mill, and there is not much expansion space to cause the liner to protrude, As a result, the fastening bolts are broken and some lining plates fall off. This phenomenon often occurs in larger mills and in smaller mills.

Wear failure: abrasive wear is one of the main forms of ball mill failure. Even if the lining plate working in the first chamber of large grinding mill bears large stress and the surface is easy to produce work hardening, the hardening layer is very thin. Under the repeated action of abrasive, the metal which is extruded and bulged and the hardened layer impacted by large abrasive edges and corners is easy to crack and peel off. It is found that there is more friction between the plow board and the surface of the plow board under the condition of grinding and hardening.

Through the analysis of the working condition of the liner and the failure analysis of the high manganese steel liner, we realize that it is safe and effective to select the material with high hardness and high wear resistance with good comprehensive mechanical properties according to the working conditions of the cement mill.

Most of the ball mills used for cement production are tube mills with length diameter ratio L / d > 2.5. The mill has a coarse grinding bin and a fine grinding bin (some of which are three bins). The coarse grinding bin is mainly used for crushing and the fine grinding bin is mainly for grinding. The liner plates of the primary mill are mainly stepped liner and wavy liner, and the liner plates of some new high efficiency and energy-saving mills are not separated from their basic forms. The main forms of the fine grinding bin are pattern lining plate, small corrugated lining plate, and flat-lining plate. The effect of the coarse grinding chamber and fine grinding chamber is different, and the ball diameter of the grinding body loaded is different, and the impact on the lining plate is also very different. With the same mill diameter, the diameter of the grinding body in the coarse grinding chamber is large, the material fragmentation is also large, the impact on the lining plate is large, and the wear speed is high; the situation of the fine grinding bin is much better. When choosing lining materials, different materials must be determined according to different conditions.

Industrial growth increases the consumption of wear-resistant parts and then stimulates and drives the development of the wear-resistant material industry. The production process, mechanical properties, and industrial application effect of 40-50 typical brands of wear-resistant steel materials have been industrialized, and the process characteristics of various varieties and small batch have been formed. After many years of production and research of wear-resistant materials, it is considered that the application of multi Alloying High Chromium Cast Iron in the coarse grinding bin of mill with size less than or equal to 3.0 m can be used safely and stably with excellent wear resistance effect and comprehensive economic effect; The application of medium carbon low alloy chromium manganese steel in the roughing bin of the mill with a diameter of fewer than 3 m has good wear resistance and appropriate comprehensive mechanical properties. In general, many kinds of wear-resistant steel materials can be selected for the fine grinding bin, and the medium carbon low-alloy chromium manganese steel developed and produced by us has achieved good results. If there is a strong investment ability, the application of high chromium cast iron can achieve the effect of no replacement for many years, and the comprehensive economic and social benefits are more prominent.

All brand names, model names or marks are owned by their respective manufacturers. MGS Casting has no affiliation with the OEM. These terms are used for identification purposes only and are not intended to indicate affiliation with or approval by the OEM. All parts are manufactured by, for and warranted by MGS Casting and are not manufactured by, purchased from or warranted by the OEM.

experimental investigation on a grinding rate constant of solid materials by a ball milleffect of ball diameter and feed size - sciencedirect

experimental investigation on a grinding rate constant of solid materials by a ball milleffect of ball diameter and feed size - sciencedirect

In the present work, a grinding rate constant, i.e., a selection function was measured for five solid materials using a tumbling ball mill, and effects of a grinding ball diameter and a feed particle size on the grinding rate constant of the materials were investigated. The tendency in the variation of the grinding rate constant with the feed size was similar in the all materials used, but was independent of the ball diameter. These relations for all materials can be expressed by modifying Snow's equation. In addition, we examined the descriptions of the grinding rate constant using two kinds of selection functions derived theoretically by Tanaka.

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