Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
  • B02C17/18—Details
  • B02C17/20—Disintegrating members
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/18—Hardening; Quenching with or without subsequent tempering
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/36—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for balls; for rollers
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/36—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/56—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.7% by weight of carbon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/001—Austenite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/002—Bainite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/004—Dispersions; Precipitations
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/009—Pearlite

Definitions

• the present invention relates to cast iron grinding balls with a high chromium content, intended for semi-autogenous grinding. It also relates to the method of manufacturing said balls.
• the current process is based on a semi-autogenous rotary mill and one or more rotary ball mills.
• a semi-autogenous rotary mill is characterized by an original design.
• the diameter is very large, more than five meters in general, with a proportionately short length. It is characterized by a length to diameter ratio generally less than 1, preferably between 0.5 and 1.
• the ore feed, made continuously, comes directly from the mine or from a crushing section. A varying amount of water is added to the mineral blocks of different sizes.
• the throughputs are very high, often much greater than 1000 tonnes per hour.
• FIGs 1A and 1B show a semi-autogenous mill 1. These mills have shields 2 with protruding parts called lifters 3, which allow very intensive lifting. When the crusher is rotating around its horizontal axis, the pieces of rock are lifted up and fall back onto the bed of rocks in the part lower. Moreover, by a relative movement between blocks and the impacts linked to the rotation, the material is reduced in size significantly, which justifies the term “autogenous grinding”.
• the grinding balls used in semi-autogenous mills must have good impact resistance as well as good wear resistance.
• the balls used in the semi-autogenous mill are subjected to significant wear by abrasion and to numerous impacts. This is due to the combined action of very hard minerals in the form of large blocks and often having sharp edges and destruction by breaking and chipping, in relation to the impact conditions inside this equipment. Worn or broken balls of smaller size are no longer effective in their role of crushing critical size blocks that accumulate in the crusher. These small balls also exit the mill through open orifices existing in the discharge grid of the semi-autogenous mill. To best combine the properties of wear resistance and impact resistance, two types of balls are generally used.
• These steels contain 0.4 to 0.9% carbon by weight, less than 1% manganese, chromium and silicon as well as elements in smaller quantities such as molybdenum, vanadium, titanium, niobium as well as impurities. more harmful such as sulfur and phosphorus for example.
• These balls are shaped by forging a bar resulting from the casting.
• the chrome cast iron balls with a chromium content greater than or equal to 5% by weight, which are directly shaped by casting in a sand or metal mold.
• These alloys have the characteristic of comprising chromium carbides, called primary, which appear during solidification during casting.
• M7C3 type carbides are M7C3 type carbides.
• austenite cells virgin of carbides appear first.
• network carbides form at the eutectic point around these austenite cells.
• FIGS. 2A and 2B typically represent the distribution of carbides in a cast iron formed by casting in a mold.
• FIG. 2A shows the network distribution of the carbides 5 which formed between the austenite dendrites during solidification.
• the concentration section generally by flotation for sulphide ores such as copper or lead and zinc.
• sulphide ores such as copper or lead and zinc.
• the chromium enrichment in the balls made of cast iron optimizes the flotation stages that take place during the recovery in this section.
• the presence of chromium makes it possible to obtain a pulp of better quality with, as a corollary, a reduction in the quantity of reagent required.
• the chromium content must be perfectly dosed to avoid an additional cost associated with the addition of chromium.
• the content of carbides and therefore of carbon must also be perfectly controlled in cast irons to avoid embrittlement of the material by excess of carbides.
• CN 103 710 646 discloses grinding balls obtained by molding.
• the grinding balls have a carbon content of between 1.7 and 2.15% by weight and a chromium content of between 5.3 and 8%. Aims of the invention
• the present invention provides a grinding ball having the advantages of low-alloy steels as well as the advantages of chromium castings, that is to say having both good impact resistance and good resistance to wear while having an optimized chromium content for the concentration section. To do so, according to the invention, the composition and the manufacturing process are optimized. The present invention provides this type of ball in particular for use in the context of a semi-autogenous grinding process.
• the present invention relates to a grinding ball comprising by weight:
• said grinding ball comprising a discrete distribution of chromium carbides as opposed to a network distribution, which gives the ball improved impact resistance properties.
• the carbon content is maintained in the range 1.1 -1.4% by weight to obtain the sufficient but not too large quantity of carbides in order to avoid weakening the ball.
• the chromium content is kept in the range 10-14% to obtain a matrix rich enough in chromium for better recovery after grinding while avoiding an additional cost linked to the addition of chromium.
• the carbon content and the chromium content are correlated according to the following inequalities:
• the carbides are finely distributed within the microstructure of the ball. Preferably, they have an equivalent diameter less than 100 ⁇ m, more preferably less than 50 ⁇ m and even more preferably less than 20 ⁇ m.
• the microstructure comprises a matrix in which the chromium carbides are distributed.
• the microstructure comprises martensite with a percentage greater than 50%, residual austenite with a percentage between 7 and 25%, a total fraction of perlite and bainite between 2 and 10%, the balance being constituted chromium carbides with a percentage less than or equal to 22%.
• the present invention also relates to the method of manufacturing this grinding ball comprising the following steps:
• Figure 1A shows a schematic view of a semi-autogenous mill.
• Figure 1B illustrates the grinding mechanism within the semi-autogenous mill.
• Figure 2A is an optical metallography of a high chrome cast iron ball formed by casting in a mold according to the prior art.
• Figure 2B is a schematic representation of the distribution of the carbides of Figure 2A.
• FIG. 3A shows two optical metallographies of a high-chromium cast iron ball shaped by forging after the continuous casting according to the invention.
• Figure 3B is a schematic representation of the distribution of the carbides of Figure 3A.
• Figures 4A and 4B illustrate the method of measuring the number of grains measured respectively along the X axis and the Y axis to assess the average grain size.
• Figure 5 is a schematic representation of the continuous casting step implemented in the method according to the invention.
• Figure 6 illustrates schematically following Figure 5 the optional step of rolling the bar resulting from the continuous casting.
• Figure 7 illustrates schematically following Figure 5 or Figure 6 the forging step of the bar resulting from continuous casting or rolling.
• Figure 8 illustrates the forging step in more detail.
• Figure 9 illustrates the joint effect of carbon and chromium on the composition of the matrix and on the carbide content.
• the present invention relates to the method of manufacturing grinding balls and to the grinding balls more specifically intended for application in a semi-autogenous mill.
• these are balls with a diameter of between 90 mm and 150 mm.
• the grinding ball is made from a high chromium cast iron having the following composition by weight:
• composition by weight Preferably and as claimed, it has the following composition by weight:
• any impurities such as vanadium, niobium and titanium with a total content of less than 0.5%
• the chromium content and the carbon content are jointly and respectively maintained in the range 10-14% and 1.1-1.4%.
• the carbon content and the chromium content are closely related.
• the dotted lines, called conodes are lines representing alloys having the same composition of the matrix, that is to say, among other things, the same chromium content in the matrix. Going from one conode to another by following the arrow in solid lines results in an increase in the chromium content in the matrix. On the other hand, by moving along a conode, the composition of the matrix remains unchanged but the carbide content changes and increases as one moves in the direction of the arrow in dotted lines.
• an increase in the chromium content in the overall composition is accompanied by an increase in the content of chromium in the matrix and an increase in the content of carbides in the matrix. It is therefore necessary to find a compromise between the carbon and chromium contents in order to obtain the sufficient but not too large quantity of carbides and chromium in the matrix. This compromise is found with the aforementioned ranges of 10-14% and 1.1-1.4% by weight for chromium and carbon respectively.
• the carbon and chromium contents are correlated according to the two inequalities: 2.55 ⁇ Cr-5.42 * C ⁇ 7.67 and 41.76 ⁇ Cr + 28.66 * C ⁇ 53.69.
• the ball according to the invention has a predominantly martensitic microstructure, ie. with a percentage of martensite greater than 50%, with a fine and homogeneous distribution of chromium carbides, called primary carbides, of the M7C3 type within the matrix.
• the primary carbides have an equivalent diameter of size less than 100 ⁇ m, more preferably less than 50 ⁇ m and even more preferably less than 20 ⁇ m.
• the carbides are not perfectly circular.
• the average of the equivalent diameters is obtained on the basis of measurements taken on at least three images.
• the measurements are, for example, taken on images having a size of 660 ⁇ m x 495 ⁇ m.
• the size of the carbides is substantially homogeneous between the surface and the heart of the ball with the manufacturing process described below.
• the method of manufacturing the grinding ball according to the invention comprises the following steps:
• the continuous casting step is illustrated with the aid of Figure 5, more specifically for horizontal continuous casting. This technique promotes fine-grained solidification by rapid cooling in a shell 9 cooled by circulating water.
• the installation comprises a liquid metal reservoir, said ladle 8, serving as a buffer between the melting equipment which is an induction furnace 6a or an arc furnace 7, and the horizontal continuous casting.
• Solidification (the liquid part is referenced 12a) is initiated in the shell 9 made of a copper alloy combining good thermal conductivity and good resistance to frictional wear, possibly followed by a graphite part enclosed in a copper envelope. water cooled and possibly followed by secondary cooling by water jets.
• the internal morphology of this copper or composite shell takes into account the specific contraction linked to the composition of the alloy which will change from the liquid state to the solid state.
• the bar 12 or billet begins to solidify in this part of the equipment and then continues to solidify towards the center in the ambient air with a movement exerted by an extraction system 10 Sometimes, some short movements against the direction of extraction are possible to improve the quality of the billet surface.
• the bar 12 is then subjected to a magnetic stirring system 11 before the cutting equipment 13 which cuts the bar 12 to the chosen length. It should be noted that several magnetic stirring systems can, if necessary, be used on the continuous casting line.
• a first parameter is the casting temperature which must be as close as possible to the solidification temperature but compatible with industrial production.
• a Superheating of 5 to 40 ° C above the solidification temperature will be the rule, while preferring an overheating of 10 to 15 ° C. This technique ensures good internal health of the billet by reducing shrinkage in the liquid metal.
• the water jets will be controlled to accelerate solidification while avoiding the formation of cracks on the surface.
• the speed of extraction and the step of extraction out of the shell will have to be adapted to the cast alloy.
• Programming the extraction speed can be complex with stops and jerks, or even acceleration and braking.
• the extraction pitch for a 90 mm round billet will be between 4 and 12 mm and preferably around 7 to 8 mm.
• the extraction speed will be between 50 and 250 steps per minute and preferably around 150 steps per minute.
• magnetic stirrers can be placed in different places to ensure the internal health of the bar. Indeed, the solidification is of the dendritic type and develops from the surface initially in contact with the copper shell. Then, the dendrites continue to grow towards the center, those corresponding to the bottom of the billet will grow faster given gravity; temperature gradients can also be created in the not yet solidified volume of the solidifying billet, which sometimes increases the risk of a central defect.
• a first electromagnetic stirrer can be positioned around the shell allowing a relatively low but homogeneous casting temperature.
• a second stirrer can be positioned at the end of the pour when the solidified thickness is approximately 20 mm.
• the electromagnetic stirrer can be placed at a distance corresponding to the end of solidification of said billet, ie approximately 7 m from the shell.
• the structure comprises a fine distribution of chromium carbides, called primary carbides, of the M7C3 type, which appear during eutectic solidification.
• primary carbides of the M7C3 type
• Two optical microscopies and their schematic representations are data respectively in Figures 3A and 3B (after forging).
• the carbides 5 do not appear in the form of a network but rather with a discrete distribution within the matrix.
• These primary carbides distributed in a point-wise or in other words discrete manner as opposed to a network distribution, provide improved abrasion resistance without deteriorating impact resistance properties. It will be noted that the carbides can exhibit a certain orientation which is given by the subsequent deformation sequences.
• the size of the solidification grain is reduced by virtue of the rapid and directed solidification of the continuous casting step according to the invention as well as by the use of the magnetic stirrer (s). This fineness of grain also contributes, but to a lesser extent, to improving impact resistance.
• the interpolation method is used for the evaluation of grain size.
• the number of grains crossed in the X direction is counted as described in FIG. 4A.
• a reference length is chosen arbitrarily, ie 200 ⁇ m for example.
• the numbers on the right side give the number of intersections.
• This method is repeated in the other direction Y. In the example illustrated, an average value of 35 ⁇ m is obtained in X and 100 ⁇ m in Y, ie an overall average of 67 ⁇ m.
• the size of the solidification grain is less than 90 ⁇ m, preferably less than 80 ⁇ m and particularly preferably between 30 and 70. pm especially in the first 15 millimeters below the surface, preferably the 20 mm, or even 25 mm below the surface.
• the grain size obtained by sand mold foundry is 100 to 400 ⁇ m and 100 to 200 ⁇ m in metal mold.
• the shaping step which can be carried out by rolling and / or forging. It is illustrated with the aid of FIGS. 6 to 8. It can be produced by rolling in a train of grooved cylinders progressively forming the ball. More often it is carried out by forging in a press 16 of a slug 18 cut from the bar 12 as shown in Figures 7 and 8. It is also possible to carry out a first rolling to reduce the diameter of the bar as shown in Figure 6 and then to shape the slips from the bar in the forging press. It is also conceivable to carry out, following the forging in the press, a rolling sequence in order to perfect the sphericity of the ball coming from the press.
• the bar 12 is heated in a pushing furnace 14 or through a series of induction furnaces 6b in the austenitic range before being rolled in the rolling stands 15, to reduce the thickness of the bar and close any porosities. Then, the rolled bar 12 is reheated again in these same types of furnaces 14,6b in the austenitic range before being introduced into the forging press 16 ( Figure 7). Typically the reheating is carried out at a temperature between 950 and 1250 ° C. The bar 12 is then cut by the knife 17 into a slug 18 which is introduced into the press 16 comprising in the example illustrated a fixed part 16a and a movable part 16b.
• the billet 18 is deformed into a blank having the shape of the ball 19 by the movable part 16b moved towards the fixed part 16a.
• the sphericity of the blank can then be improved by passing it between two cylinders having a shape close to an Archimedean screw.
• the blank in the form of a ball is then subjected to a heat treatment in one or more cycles to obtain the final product.
• the austenitization is carried out in a temperature range of between 880 and 1075 ° C for a time of between 30 minutes and 3 hours.
• this cycle can be carried out in several stages with a first level of maintenance at a temperature between 620 and 730 ° C for a time between 15 minutes and two hours followed by the second maintenance between 880 and 1075 ° C for a time between between 30 minutes and 3 hours.
• the blank is subjected to quenching to a temperature below 220 ° C to form the martensite.
• the quenching can be carried out in oil, water, blown air, in a polymer, etc.
• This austenitization and quenching cycle can be followed by an expansion tempering at a temperature of between 150 and 400 ° C for a time of between 30 minutes and 6 hours.
• the purpose of this relaxation income is to slightly reduce the internal stresses generated by the transformation of austenite into martensite.
• the process described above can be carried out continuously so as to avoid or at least limit the reheating phases between the casting and the shaping for example or between the shaping and the heat treatment .
• a microstructure is obtained with a matrix comprising martensite in a percentage greater than 50%, preferably between 60 and 80%, of the residual austenite with a percentage between 7 and 25% and preferably between 10 and 20%, and a fraction of perlite and bainite in total between 2 and 10%.
• the microstructure comprises the primary carbides distributed in the matrix and possibly a few secondary carbides of the M23C6 type, formed during the heat treatment cycles.
• the microstructure thus comprises, for a total percentage of 100%, the aforementioned structures with a balance consisting of chromium carbides with a percentage which can reach 22%.
• the fraction of residual austenite is measured by X-ray diffraction according to the ASTM E975-13 standard and the fractions of the other phases are measured by image analysis.
• the final properties are a hardness of 54 to 65 Rc and more generally close to 60 Rc, the Rockwell C hardness being measured according to the ISO6508-1: 2016 standard.
• the grinding balls according to the invention thus have excellent resistance to wear conferred in a known manner by the high hardness of the alloy obtained by virtue of the presence of martensite and chromium carbides. On the other hand, surprisingly, this excellent wear resistance is combined with very good impact resistance properties thanks to the fine distribution of primary carbides as well as to the small size of the solidification grains.
• the impact resistance properties were tested and compared with those of high chromium cast iron grinding balls shaped by casting according to the prior art.
• the test is based on a technical article from the US Bureau of Mines (R. Collinsensderfer and JH Tylczak, Minerais & Metallu ical processinci, May 1989, pp 60-66).
• the test consists in dropping for each of the two types of balls, 46 balls with a diameter of 125 mm from a height of 10 m.
• the test is carried out by cycle with each of the balls released successively and then reintegrated into the loop to be released again.
• the balls are regularly weighed. If the weight loss is greater than 50%, the test is stopped.
• the basic specification is a minimum of 60,000 impacts.
• the grinding balls according to the invention thus exhibit excellent wear resistance with impact resistance properties at least equal to those of conventional forged carbon steels.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Food Science & Technology (AREA)
• Crushing And Grinding (AREA)
• Heat Treatment Of Steel (AREA)
• Forging (AREA)
• Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
• Grinding Of Cylindrical And Plane Surfaces (AREA)

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• 2020
  • 2020-01-16 BE BE20205031A patent/BE1027395B1/fr active IP Right Grant
• 2021
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  • 2021-01-14 WO PCT/EP2021/050656 patent/WO2021144347A1/fr not_active Ceased
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• 2022
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