[Introduction]: Casting steel ball (casting grinding ball) is made of the scrap steel, scrap metal and other waste scrap which are melted by the heating of intermediate frequency electric furnace. In the melting process, the amount of precious metal alloy (such as iron, manganese, vanadium etc.) is added into the furnace for chemical composition. Then pour the qualified molten iron into the production line mold of steel ball when temperature of molten iron reaches more than 1550 and the molten iron meets other technology requirements.
Notes:1. The ball with diameter 100mm is used in impact fatigue test; the test height is 3.5m; the impact times of the ball with other diameter are calculated by this formula, Nx=N*100/D, N is time. 2. The impact toughness and impact fatigue life index is not treated as delivery basis.
3. Chemical composition test: when the volume smelting furnace more than 0.5 tons, we should check the chemical composition furnace by furnace; when the volume smelting furnace not more than 0.5 tons, we should check the chemical composition once per shift. Once there is one furnace unqualified, we need to sample double furnace for test. If there is still one not qualified, this branch of balls is unqualified.
4. Surface hardness test: sampling from different location of each batch of heating furnace, the number of the ball 5.Once there is one unqualified, we need to sample double balls for test. If there is still a ball not qualified, this branch of balls is unqualified.
5. Internal quality detection: we sample 1 largest size casting iron grinding ball in 100 tons the same type cast iron grinding ball of each continuous production. Once there is one unqualified, we need to sample double balls for test. If there is still a ball not qualified, this branch of balls is unqualified.
JALALPURA, Nagpur Shri Gokulesh Bhavan, Near Rapid Transport Co., Behind Prateesh Sales Near Madhur Courier, Opposite Shankar Mandir, Gandhi Bagh,, JALALPURA, Nagpur - 440002, Dist. Nagpur, Maharashtra
JALALPURA, Nagpur Shri Gokulesh Bhavan, Near Rapid Transport Co., Behind Prateesh Sales Near Madhur Courier, Opposite Shankar Mandir, Gandhi Bagh,, JALALPURA, Nagpur - 440002, Dist. Nagpur, Maharashtra
Nagdevi, Mumbai Burhani House, Room No. 21, 2nd Floor, 53, Bhajipala Lane, Near 142, Nagdevi Street Bombay Mercantile Bank Lane, Masjid Bunder West, Nagdevi, Mumbai - 400003, Dist. Mumbai, Maharashtra
High chromium Cast Iron Balls High chromium ball also known as wear-resistant steel ball ,are widely used in the ball mill grinding process. Production technology : Iron mould coated sand production line, constant temperature pouring casting, the bottom leakage type pouring,pouring the inlet filter Application : Cement building materials, metal mining, coal thermal power, chemical engineering, light industrial papermaking,magnetic materials, ceramic coatings Wear-resistant high Chromium ball technology parameters Wear-resistant steel ball mechanical properties and microstructure analysis name brand surface hardness (HRC) Impact value Ak(J/cm2) microstructure Falling ball impact fatigue life high chromium ball ZQCr10 58-66 2.5 M+C 80 15000 80 10000 Ccarbide Mmartensite Specifications(mm) Each weight(Kg) Quantity(pcs) per ton 30 0.11 9091 40 0.257 3891 50 0.50 2000 60 0.867 1153 70 1.37 729 80 2.05 487 90 2.90 345 100 4.00 250 110 5.30 188 120 6.80 147 125 7.75 129 130 8.74 114 Packaging & Shipping Packing :Container bags or steel drums or others. For Container Bag, Net weight 1000Kgs ,Gross Weight 1002KGS ,Measurement 0.4CBM For Steel Drums ,Net weight 850-950Kgs ,Gross Weight 865-965KGS ,Measurement 0.3CBM . Shipping and delivery Port of loading:Qingdao Port,China Delivery time : Normally 2-3 weeks after down payment received. Partial shippment allowed FAQ Payment terms :T/T (30% DP,balance against copy of B/L.; L/C Samples : Free samples are provided for test before trial order MOQ :1 Ton Key words : High Chromium ball ,High chrome grinding ball, high chrome ball, high chrome cast steel ball, High Chrome Casting Grinding Balls,High Chrome grinding media ball,High Chrome mill ball For more information about our products ,Pls feel free to contact us
In all ore dressing and milling Operations, including flotation, cyanidation, gravity concentration, and amalgamation, the Working Principle is to crush and grind, often with rob mill & ball mills, the ore in order to liberate the minerals. In the chemical and process industries, grinding is an important step in preparing raw materials for subsequent treatment.In present day practice, ore is reduced to a size many times finer than can be obtained with crushers. Over a period of many years various fine grinding machines have been developed and used, but the ball mill has become standard due to its simplicity and low operating cost.
A ball millefficiently operated performs a wide variety of services. In small milling plants, where simplicity is most essential, it is not economical to use more than single stage crushing, because the Steel-Head Ball or Rod Mill will take up to 2 feed and grind it to the desired fineness. In larger plants where several stages of coarse and fine crushing are used, it is customary to crush from 1/2 to as fine as 8 mesh.
Many grinding circuits necessitate regrinding of concentrates or middling products to extremely fine sizes to liberate the closely associated minerals from each other. In these cases, the feed to the ball mill may be from 10 to 100 mesh or even finer.
Where the finished product does not have to be uniform, a ball mill may be operated in open circuit, but where the finished product must be uniform it is essential that the grinding mill be used in closed circuit with a screen, if a coarse product is desired, and with a classifier if a fine product is required. In most cases it is desirable to operate the grinding mill in closed circuit with a screen or classifier as higher efficiency and capacity are obtained. Often a mill using steel rods as the grinding medium is recommended, where the product must have the minimum amount of fines (rods give a more nearly uniform product).
Often a problem requires some study to determine the economic fineness to which a product can or should be ground. In this case the 911Equipment Company offers its complete testing service so that accurate grinding mill size may be determined.
Until recently many operators have believed that one particular type of grinding mill had greater efficiency and resulting capacity than some other type. However, it is now commonly agreed and accepted that the work done by any ballmill depends directly upon the power input; the maximum power input into any ball or rod mill depends upon weight of grinding charge, mill speed, and liner design.
The apparent difference in capacities between grinding mills (listed as being the same size) is due to the fact that there is no uniform method of designating the size of a mill, for example: a 5 x 5 Ball Mill has a working diameter of 5 inside the liners and has 20 per cent more capacity than all other ball mills designated as 5 x 5 where the shell is 5 inside diameter and the working diameter is only 48 with the liners in place.
Ball-Rod Mills, based on 4 liners and capacity varying as 2.6 power of mill diameter, on the 5 size give 20 per cent increased capacity; on the 4 size, 25 per cent; and on the 3 size, 28 per cent. This fact should be carefully kept in mind when determining the capacity of a Steel- Head Ball-Rod Mill, as this unit can carry a greater ball or rod charge and has potentially higher capacity in a given size when the full ball or rod charge is carried.
A mill shorter in length may be used if the grinding problem indicates a definite power input. This allows the alternative of greater capacity at a later date or a considerable saving in first cost with a shorter mill, if reserve capacity is not desired. The capacities of Ball-Rod Mills are considerably higher than many other types because the diameters are measured inside the liners.
The correct grinding mill depends so much upon the particular ore being treated and the product desired, that a mill must have maximum flexibility in length, type of grinding medium, type of discharge, and speed.With the Ball-Rod Mill it is possible to build this unit in exact accordance with your requirements, as illustrated.
To best serve your needs, the Trunnion can be furnished with small (standard), medium, or large diameter opening for each type of discharge. The sketch shows diagrammatic arrangements of the four different types of discharge for each size of trunnion opening, and peripheral discharge is described later.
Ball-Rod Mills of the grate discharge type are made by adding the improved type of grates to a standard Ball-Rod Mill. These grates are bolted to the discharge head in much the same manner as the standard headliners.
The grates are of alloy steel and are cast integral with the lifter bars which are essential to the efficient operation of this type of ball or rod mill. These lifter bars have a similar action to a pump:i. e., in lifting the product so as to discharge quickly through the mill trunnion.
These Discharge Grates also incorporate as an integral part, a liner between the lifters and steel head of the ball mill to prevent wear of the mill head. By combining these parts into a single casting, repairs and maintenance are greatly simplified. The center of the grate discharge end of this mill is open to permit adding of balls or for adding water to the mill through the discharge end.
Instead of being constructed of bars cast into a frame, Grates are cast entire and have cored holes which widen toward the outside of the mill similar to the taper in grizzly bars. The grate type discharge is illustrated.
The peripheral discharge type of Ball-Rod Mill is a modification of the grate type, and is recommended where a free gravity discharge is desired. It is particularly applicable when production of too many fine particles is detrimental and a quick pass through the mill is desired, and for dry grinding.
The drawings show the arrangement of the peripheral discharge. The discharge consists of openings in the shell into which bushings with holes of the desired size are inserted. On the outside of the mill, flanges are used to attach a stationary discharge hopper to prevent pulp splash or too much dust.
The mill may be operated either as a peripheral discharge or a combination or peripheral and trunnion discharge unit, depending on the desired operating conditions. If at any time the peripheral discharge is undesirable, plugs inserted into the bushings will convert the mill to a trunnion discharge type mill.
Unless otherwise specified, a hard iron liner is furnished. This liner is made of the best grade white iron and is most serviceable for the smaller size mills where large balls are not used. Hard iron liners have a much lower first cost.
Electric steel, although more expensive than hard iron, has advantage of minimum breakage and allows final wear to thinner section. Steel liners are recommended when the mills are for export or where the source of liner replacement is at a considerable distance.
Molychrome steel has longer wearing qualities and greater strength than hard iron. Breakage is not so apt to occur during shipment, and any size ball can be charged into a mill equipped with molychrome liners.
Manganese liners for Ball-Rod Mills are the world famous AMSCO Brand, and are the best obtainable. The first cost is the highest, but in most cases the cost per ton of ore ground is the lowest. These liners contain 12 to 14% manganese.
The feed and discharge trunnions are provided with cast iron or white iron throat liners. As these parts are not subjected to impact and must only withstand abrasion, alloys are not commonly used but can be supplied.
Gears for Ball-Rod Mills drives are furnished as standard on the discharge end of the mill where they are out of the way of the classifier return, scoop feeder, or original feed. Due to convertible type construction the mills can be furnished with gears on the feed end. Gear drives are available in two alternative combinations, which are:
All pinions are properly bored, key-seated, and pressed onto the steel countershaft, which is oversize and properly keyseated for the pinion and drive pulleys or sheaves. The countershaft operates on high grade, heavy duty, nickel babbitt bearings.
Any type of drive can be furnished for Ball-Rod Mills in accordance with your requirements. Belt drives are available with pulleys either plain or equipped with friction clutch. Various V- Rope combinations can also be supplied.
The most economical drive to use up to 50 H. P., is a high starting torque motor connected to the pinion shaft by means of a flat or V-Rope drive. For larger size motors the wound rotor (slip ring) is recommended due to its low current requirement in starting up the ball mill.
Should you be operating your own power plant or have D. C. current, please specify so that there will be no confusion as to motor characteristics. If switches are to be supplied, exact voltage to be used should be given.
Even though many ores require fine grinding for maximum recovery, most ores liberate a large percentage of the minerals during the first pass through the grinding unit. Thus, if the free minerals can be immediately removed from the ball mill classifier circuit, there is little chance for overgrinding.
This is actually what has happened wherever Mineral Jigs or Unit Flotation Cells have been installed in the ball mill classifier circuit. With the installation of one or both of these machines between the ball mill and classifier, as high as 70 per cent of the free gold and sulphide minerals can be immediately removed, thus reducing grinding costs and improving over-all recovery. The advantage of this method lies in the fact that heavy and usually valuable minerals, which otherwise would be ground finer because of their faster settling in the classifier and consequent return to the grinding mill, are removed from the circuit as soon as freed. This applies particularly to gold and lead ores.
Ball-Rod Mills have heavy rolled steel plate shells which are arc welded inside and outside to the steel heads or to rolled steel flanges, depending upon the type of mill. The double welding not only gives increased structural strength, but eliminates any possibility of leakage.
Where a single or double flanged shell is used, the faces are accurately machined and drilled to template to insure perfect fit and alignment with the holes in the head. These flanges are machined with male and female joints which take the shearing stresses off the bolts.
The Ball-Rod Mill Heads are oversize in section, heavily ribbed and are cast from electric furnace steel which has a strength of approximately four times that of cast iron. The head and trunnion bearings are designed to support a mill with length double its diameter. This extra strength, besides eliminating the possibility of head breakage or other structural failure (either while in transit or while in service), imparts to Ball-Rod Mills a flexibility heretofore lacking in grinding mills. Also, for instance, if you have a 5 x 5 mill, you can add another 5 shell length and thus get double the original capacity; or any length required up to a maximum of 12 total length.
On Type A mills the steel heads are double welded to the rolled steel shell. On type B and other flanged type mills the heads are machined with male and female joints to match the shell flanges, thus taking the shearing stresses from the heavy machine bolts which connect the shell flanges to the heads.
The manhole cover is protected from wear by heavy liners. An extended lip is provided for loosening the door with a crow-bar, and lifting handles are also provided. The manhole door is furnished with suitable gaskets to prevent leakage.
The mill trunnions are carried on heavy babbitt bearings which provide ample surface to insure low bearing pressure. If at any time the normal length is doubled to obtain increased capacity, these large trunnion bearings will easily support the additional load. Trunnion bearings are of the rigid type, as the perfect alignment of the trunnion surface on Ball-Rod Mills eliminates any need for the more expensive self-aligning type of bearing.
The cap on the upper half of the trunnion bearing is provided with a shroud which extends over the drip flange of the trunnion and effectively prevents the entrance of dirt or grit. The bearing has a large space for wool waste and lubricant and this is easily accessible through a large opening which is covered to prevent dirt from getting into the bearing.Ball and socket bearings can be furnished.
Scoop Feeders for Ball-Rod Mills are made in various radius sizes. Standard scoops are made of cast iron and for the 3 size a 13 or 19 feeder is supplied, for the 4 size a 30 or 36, for the 5 a 36 or 42, and for the 6 a 42 or 48 feeder. Welded steel scoop feeders can, however, be supplied in any radius.
The correct size of feeder depends upon the size of the classifier, and the smallest feeder should be used which will permit gravity flow for closed circuit grinding between classifier and the ball or rod mill. All feeders are built with a removable wearing lip which can be easily replaced and are designed to give minimum scoop wear.
A combination drum and scoop feeder can be supplied if necessary. This feeder is made of heavy steel plate and strongly welded. These drum-scoop feeders are available in the same sizes as the cast iron feeders but can be built in any radius. Scoop liners can be furnished.
The trunnions on Ball-Rod Mills are flanged and carefully machined so that scoops are held in place by large machine bolts and not cap screws or stud bolts. The feed trunnion flange is machined with a shoulder for insuring a proper fit for the feed scoop, and the weight of the scoop is carried on this shoulder so that all strain is removed from the bolts which hold the scoop.
High carbon steel rods are recommended, hot rolled, hot sawed or sheared, to a length of 2 less than actual length of mill taken inside the liners. The initial rod charge is generally a mixture ranging from 1.5 to 3 in diameter. During operation, rod make-up is generally the maximum size. The weights per lineal foot of rods of various diameters are approximately: 1.5 to 6 lbs.; 2-10.7 lbs.; 2.5-16.7 lbs.; and 3-24 lbs.
Forged from the best high carbon manganese steel, they are of the finest quality which can be produced and give long, satisfactory service. Data on ball charges for Ball-Rod Mills are listed in Table 5. Further information regarding grinding balls is included in Table 6.
Rod Mills has a very define and narrow discharge product size range. Feeding a Rod Mill finer rocks will greatly impact its tonnage while not significantly affect its discharge product sizes. The 3.5 diameter rod of a mill, can only grind so fine.
Crushers are well understood by most. Rod and Ball Mills not so much however as their size reduction actions are hidden in the tube (mill). As for Rod Mills, the image above best expresses what is going on inside. As rocks is feed into the mill, they are crushed (pinched) by the weight of its 3.5 x 16 rods at one end while the smaller particles migrate towards the discharge end and get slightly abraded (as in a Ball Mill) on the way there.
We haveSmall Ball Mills for sale coming in at very good prices. These ball mills are relatively small, bearing mounted on a steel frame. All ball mills are sold with motor, gears, steel liners and optional grinding media charge/load.
Ball Mills or Rod Mills in a complete range of sizes up to 10 diameter x20 long, offer features of operation and convertibility to meet your exactneeds. They may be used for pulverizing and either wet or dry grindingsystems. Mills are available in both light-duty and heavy-duty constructionto meet your specific requirements.
All Mills feature electric cast steel heads and heavy rolled steelplate shells. Self-aligning main trunnion bearings on large mills are sealedand internally flood-lubricated. Replaceable mill trunnions. Pinion shaftbearings are self-aligning, roller bearing type, enclosed in dust-tightcarrier. Adjustable, single-unit soleplate under trunnion and drive pinionsfor perfect, permanent gear alignment.
Ball Mills can be supplied with either ceramic or rubber linings for wet or dry grinding, for continuous or batch type operation, in sizes from 15 x 21 to 8 x 12. High density ceramic linings of uniform hardness male possible thinner linings and greater and more effective grinding volume. Mills are shipped with liners installed.
Complete laboratory testing service, mill and air classifier engineering and proven equipment make possible a single source for your complete dry-grinding mill installation. Units available with air swept design and centrifugal classifiers or with elevators and mechanical type air classifiers. All sizes and capacities of units. Laboratory-size air classifier also available.
A special purpose batch mill designed especially for grinding and mixing involving acids and corrosive materials. No corners mean easy cleaning and choice of rubber or ceramic linings make it corrosion resistant. Shape of mill and ball segregation gives preferential grinding action for grinding and mixing of pigments and catalysts. Made in 2, 3 and 4 diameter grinding drums.
Nowadays grinding mills are almost extensively used for comminution of materials ranging from 5 mm to 40 mm (3/161 5/8) down to varying product sizes. They have vast applications within different branches of industry such as for example the ore dressing, cement, lime, porcelain and chemical industries and can be designed for continuous as well as batch grinding.
Ball mills can be used for coarse grinding as described for the rod mill. They will, however, in that application produce more fines and tramp oversize and will in any case necessitate installation of effective classification.If finer grinding is wanted two or three stage grinding is advisable as for instant primary rod mill with 75100 mm (34) rods, secondary ball mill with 2540 mm(11) balls and possibly tertiary ball mill with 20 mm () balls or cylpebs.To obtain a close size distribution in the fine range the specific surface of the grinding media should be as high as possible. Thus as small balls as possible should be used in each stage.
The principal field of rod mill usage is the preparation of products in the 5 mm0.4 mm (4 mesh to 35 mesh) range. It may sometimes be recommended also for finer grinding. Within these limits a rod mill is usually superior to and more efficient than a ball mill. The basic principle for rod grinding is reduction by line contact between rods extending the full length of the mill, resulting in selective grinding carried out on the largest particle sizes. This results in a minimum production of extreme fines or slimes and more effective grinding work as compared with a ball mill. One stage rod mill grinding is therefore suitable for preparation of feed to gravimetric ore dressing methods, certain flotation processes with slime problems and magnetic cobbing. Rod mills are frequently used as primary mills to produce suitable feed to the second grinding stage. Rod mills have usually a length/diameter ratio of at least 1.4.
Tube mills are in principle to be considered as ball mills, the basic difference being that the length/diameter ratio is greater (35). They are commonly used for surface cleaning or scrubbing action and fine grinding in open circuit.
In some cases it is suitable to use screened fractions of the material as grinding media. Such mills are usually called pebble mills, but the working principle is the same as for ball mills. As the power input is approximately directly proportional to the volume weight of the grinding media, the power input for pebble mills is correspondingly smaller than for a ball mill.
A dry process requires usually dry grinding. If the feed is wet and sticky, it is often necessary to lower the moisture content below 1 %. Grinding in front of wet processes can be done wet or dry. In dry grinding the energy consumption is higher, but the wear of linings and charge is less than for wet grinding, especially when treating highly abrasive and corrosive material. When comparing the economy of wet and dry grinding, the different costs for the entire process must be considered.
An increase in the mill speed will give a directly proportional increase in mill power but there seems to be a square proportional increase in the wear. Rod mills generally operate within the range of 6075 % of critical speed in order to avoid excessive wear and tangled rods. Ball and pebble mills are usually operated at 7085 % of critical speed. For dry grinding the speed is usually somewhat lower.
The mill lining can be made of rubber or different types of steel (manganese or Ni-hard) with liner types according to the customers requirements. For special applications we can also supply porcelain, basalt and other linings.
The mill power is approximately directly proportional to the charge volume within the normal range. When calculating a mill 40 % charge volume is generally used. In pebble and ball mills quite often charge volumes close to 50 % are used. In a pebble mill the pebble consumption ranges from 315 % and the charge has to be controlled automatically to maintain uniform power consumption.
In all cases the net energy consumption per ton (kWh/ton) must be known either from previous experience or laboratory tests before mill size can be determined. The required mill net power P kW ( = ton/hX kWh/ton) is obtained from
Trunnions of S.G. iron or steel castings with machined flange and bearing seat incl. device for dismantling the bearings. For smaller mills the heads and trunnions are sometimes made in grey cast iron.
The mills can be used either for dry or wet, rod or ball grinding. By using a separate attachment the discharge end can be changed so that the mills can be used for peripheral instead of overflow discharge.
High Chrome Cast Iron Grinding Ball Used for Cement Plant Ball Mill with Good Quality 1. Chemical Composition of High Chrome Cast Iron Grinding Ball Used for Cement Plant Ball Mill with Good Quality Name Designation Chemical compositionCSiMnCrMo P SHigh chromium cast grinding balls ZQCr262.0-2.81.00.5-2.021-281.00.100.08ZQCr202.0-2.81.00.5-2.017-221.50.100.08ZQCr172.0-3.21.00.5-2.014-181.50.100.08ZQCr131.8-188.8.131.520-151.50.100.08 2. Properties and Microstructure of High Chrome Cast Iron Grinding Ball Used for Cement Plant Ball Mill with Good Quality Name DesignationHardness(HRC)AK(J/CM2)MicrostructureTime of falling ballsQuenchedUnquenchedHigh chromium cast grinding balls ZQCr26584540M+C8000ZQCr2058453.58000ZQCr1758453.08000ZQCr1358452.38000 3. Advantages of High Chrome Cast Iron Grinding Ball Used for Cement Plant Ball Mill with Good Quality a).Our products from Grinding Ball production to after sale is based on Shandong province China high quality and low-cost. Worthy of your trust. b).The Heat treatment technology is very perfect, especially the tempering process, it increase the hardness of the forging steel ball and more wear-resisting. c).Our grinding ball has been exported to Japan, Indonesia, Malaysia and many other countries and have got great reputation from our customer at home and abroad 4. Quality assurance and after-sales service of High Chrome Cast Iron Grinding Ball Used for Cement Plant Ball Mill with Good Quality a>The quality of the security deposit. b>The third party inspection. c>Test report issued by our customer. d>Before delivery,you can test products by yourselves. e>Free samples can be provided for testing,or Sample orders(20Ton) 5. Packing Methods of High Chrome Cast Iron Grinding Ball Used for Cement Plant Ball Mill with Good Quality
Jayaswal Neco Industries Limited (JNIL), which started in 1976 as a small Iron foundry unit at Nagpur, is the flagship company of NECO Group of Industries. JNIL is today an INR 26 billion (US$ 472 million) turnover company with technologically advanced production infrastructure and a strong country-wide marketing network. Today our total production capacity of Iron and Steel castings exceeds 140,000 MTPA. The companys strategy of backward and forward integration has enabled it absorb the fluctuations in business cycles. The NECO name is synonymous with Quality, Reliability and Durability of products.
Conventionally, grinding media was made of Cast iron, Cast steel and even through Forged process in EN specifications. However, High Chrome Grinding media has surpassed the conventionally produced grinding media in terms of performance and is now widely being used by all industries across the globe.
The large focus is on the power consumption and increased output. The grades of HCGM of SBIPL are such that the balls retain their shape as they tend to wear. De-shaped balls are like dead balls, which do not assist in effective grinding, and tend to slide as they move up the periphery of mill, instead of falling or toppling from the top. Such dead load decreases the grinding efficiency, increases the power consumption of the mill and also results in decreased output.
Air Hammer forging steel ball main production process: Round steel bars are cut according to ball size after passing the inspection; Steel is heated to a certain temperature by a medium frequency furnace to ensure an effective forming variable in the forging; the red-hot steel forging is fed into an air hammer and is knocked over by a skilled operator. After forging, the red-hot steel balls are quenched and tempered immediately in the heat treatment equipment to obtain high and uniform hardness.
Thecastinggrinding ball is a kind of grindingballs which uses the medium frequency electric furnace tomeltthe scrap steel, scrap iron and so on.The furnace charge is fully melted and the precious metal alloy (such as ferrochromium, Ferromanganese, ferrovanadium, etc.) is added to the furnace for chemical composition conditioning.After heating,the qualified molten iron is poured into the steel ball metal mold or automatic steel ball production lines moldwhen the molten iron temperature reaches above 1550Cso thatmeets the technical requirements.
After molding, then start to heat treatment. It includes quenching parts and tempering parts. For quenching, it alsodivides into oil quench, air quench according to the different composition of balls.
For casting grinding balls, there are also two types. One isthe white cast iron with chromium as the main alloy element, which is called Chromium Alloy cast iron. It means the ballsmade of chromium alloy cast iron(chrome grinding balls); another typeismade of nodularcast iron (called nodular cast iron grinding ball).The Matrix obtained by heat treatment is mainly Bainite spheroidal graphite cast iron grinding ball referred to as Bainite spheroidal graphite iron grinding ball; The Matrix obtained by heat treatment is mainly a martensite spheroidal graphite cast iron grinding ball referred to as the Martensite Ball.
The grinding balls, including casting type and forging type, widely used in metallurgical mines, cement building materials, thermal power generation, flue gas desulphurization, magnetic materials, chemicals, coal-water slurry, pellets, slag, ultra-fine powder, fly ash, calcium carbonate, quartz sand and other industries ball mill.
ABSTRACT: A heat treatment process of high chromium cast iron grinding media with trace alloying elements Mo, V, NB was studied. The heat treatment processes of quenching at 980 C, tempering at 400 C and 600 C was adopted. The microstructure of the quenched Matrix is quenched Martensite, tempered at 400 C and tempered at 600 C is tempered Sorbate.
The results of hardness analysis and wear resistance analysis show that the hardness of the sample treated by quenching is 65HRCand the wear amount is the smallest, the hardness decreases to 62.8 HRC after tempering at 400 C and the wear amount increases by 18.2% compared with the quenched state, and the hardness decreases to 57.6 HRC after moderating at 600 C The wear rate increased by 30.3% compared with the quenching state.
Ball mill is widely used in cement, electric power, mineral processing, building materials, and other industries. As the grinding medium in the ball mill, the grinding ball must have both high wear resistance and good toughness. In recent years, with the rapid development of Chinas industry, the consumption of grinding ball is very large. The method of improving the performance of the grinding ball and increasing its service life will produce great economic benefits. The wear resistance of the grinding ball is closely related to its heat treatment process. In this paper, the metallographic structure and properties of the high chromium alloy ball are analyzed through the experimental study on the composition design and heat treatment process A heat treatment process for improving the wear resistance of high chromium alloy balls was proposed.
(1) Carbon: C has a significant effect on the matrix structure and carbide of high chromium cast iron. C is the main element for the formation of eutectic carbide (C R, F e)7 c 3, which plays a vital role in wear resistance.
(2) CR: Cr is a basic alloy element which ensures excellent wear resistance and toughness of high chromium white cast iron. The content of CR determines the type of carbide. When the content of CR reaches a certain amount, the increase of the content is not obvious for the improvement of wear resistance, too little cannot form a high hardness carbide (CR, Fe)7 C3.
(5) Niobium: After adding Niobium into high chrome cast iron, the properties of high chromium cast iron can be improved by improving the matrix structure and carbide morphology. The improvement of wear resistance and impact toughness is the primary performance.
(6) Trace alloying element: In High Chromium cast iron, the concentration of chromium in the Matrix is not enough to restrain the transformation of pearlite shape because most of the added chromium goes into carbide. In order to improve the as-cast hardenability of the grinding ball, it is necessary to add Mo, Cu, V, and w to the grinding ball for micro-alloying, the content (mass fraction) of which is less than 1.0 %. The combination of Molybdenum and copper can improve the impact toughness of the alloy and prolong the service life of the grinding ball.
Based on the failure analysis of the wear-resistant ball in a steel plant in Shanxi Province, the key to improve the wear-resistant performance of the ball is how to make the hardness and toughness of the Matrix match well. The toughness of the material can be further improved through grain boundary purification, grain refinement, carbide content control, carbide morphology, and size improvement while obtaining high hardness. The effect of composition optimization on the microstructure and properties of high chromium white cast iron was studied by increasing the content of CR, Mo and adding Re. The chemical composition of the optimized wear-resistant ball is shown in table 1.
The sample of 10mm* 10 mm* 8 mm in size at the center of the grinding ball was cut by weld and polished with 200 # to 1500 # metallographic sandpaper. The etching agent was 4% nitric alcohol and the etching time was 10S. The microstructure was observed and analyzed by MDS-type metalloscope.
Hardness is an important index of wear resistance, and the uniformity of ball hardness reflects the uniformity of wear. In this experiment, HR-150A Rockwell hardness tester was used, the load was 5kgs, the loading time was 5m, and the hardness was measured from the center of the specimen to the edge of the specimen. The hardness values of high chromium white cast iron after as-cast and heat treatment were measured and compared to study the effects of composition and heat treatment process on the hardness of the material.
Wear resistance is evaluated by the amount of wear under the same wear condition. Adopts ML-10 type tester, the Motor Speed is 90 r / min, the quartz sandpaper is 140 # , the load is 200g, 400g, and 800g respectively, the specimen size is dia 6 * 10mm, and the specimen is measured by the Electronic Analytical Balance (accuracy is 0.1 mg) after the specimen is worn by positive rotation and reverse rotation Wear capacity M = mass before wear M 1-mass after wear M2.
Fig. 3 is the microstructure of grinding media after different heat treatment processes. The as-cast structure shown in Fig. 3(a) is composed of Pearlite P + Carbide + Abnormal Ledeburite, with less ledeburite and more cementite, and the carbides are mostly net-like carbides. 3(B) shows the microstructure of the sample quenched at 980 C and air-cooled to room temperature, and its Matrix is acicular martensite m + granular carbide + a small amount of retained austenite. 3(C) is quenched at 980 C and air-cooled to room temperature and tempered at 400 C. The microstructure from air cooling to room temperature, the matrix structure is tempered tobolite T + Carbide + a small amount of retained AUSTENITE A, Fig. 4(d) is the microstructure from air cooling to room temperature after quenching at 980 C, and then after high temperature tempering at 600 C, Air Cooling to room temperature. The microstructure is tempered sorbite + carbide + a small amount of retained austenite. High-temperature tempering results in the decomposition of Martensite to form sorbite, and the ferrite and carbide are coarse.
Fig. 4 is the hardness contrast of grinding media under different heat treatment process. From Fig. 4, it can be seen that the hardness of grinding media is the highest after quenching at 980 C, and the hardness reaches 65HRC. The results show that the microstructure of sample an at room temperature is metamorphosed, Ledeburite as Matrix and contains pearlite and carbide, and the hardness is not high; the microstructure of sample B is mainly quenched acicular martensite with high hardness; The Matrix is mainly tempered troostite, the hardness decreases, and sample D is tempered from high temperature to room temperature, wear-resisting, the martensite in the ball structure decomposes and forms tempered sorbite, which causes the hardness to decrease seriously.
Fig. 5 is a comparison of abrasive wear of grinding media under different heat treatment processes. As can be seen from Fig. 5, after quenching at 980 C, the wear amount is the smallest, which is related to the high hardness of the quenched structure, but the internal stress is easy to exist in the quenched structure, and after quenching and tempering at 980 c, the wear amount is larger than that of the wear resistant ball quenched at 980 C The results show that the wear resistance of the ball after tempering at 400 C is lower than that after tempering at 600C, and the wear resistance of the ball after tempering at 400 C is better than that after tempering at 600C.
In this experiment, the grinding media samples were heat-treated by different processes in a high-temperature heating furnace. The microstructure and wear resistance of the grinding media after heat-treatment were analyzed by means of the metallographic microscope, Rockwell hardness tester and wear tester And came to the following conclusions:
1) At room temperature after quenching at 980 C, the Matrix structure is mainly quenched martensite, at which time the grinding media has high hardness and wear resistance, but the internal stress often exists in the quenched structure, which is easy to cause the crack and deformation of the grinding media, so it must be tempered to eliminate the internal stress and improve the toughness of the grinding media.
2) After tempering at 400 C, the Matrix structure is mainly tempered tobolite at room temperature, and the grinding media has higher hardness and wear resistance, and after tempering at 600 C, the Matrix structure is mainly tempered sorbite and contains a lot of coarse ferrite and carbide, which leads to the poor hardness and wear resistance of the grinding media. Therefore, the optimum heat treatment process for the alloy components studied is quenching at 980 C and tempering at 400 C.
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