Preparation method of low-cost high-performance large-diameter forged grinding ball

Abstract

The invention discloses a preparation method of a low-cost high-performance large-diameter forged grinding ball, and belongs to the technical field of grinding balls. The method comprises the following steps: taking Q235 scrap steel and waste high manganese steel ZG120Mn13 as main raw materials, adding a small amount of ferroboron, aluminum-magnesium alloy, ferrotitanium and a carburant, smelting molten steel by adopting an electric furnace, continuously casting to form a steel billet, rolling and forging the steel billet, and optimizing a heat treatment process to obtain the low-cost high-performance large-diameter forged grinding ball. The wear-resistant grinding ball has the characteristics of high strength, high hardness, high wear resistance and impact resistance, the surface hardness of the wear-resistant grinding ball can reach 61-63 HRC, the hardness distribution is uniform, the internal and external hardness difference is small, and the defects of quenching soft spots and the like are avoided. The wear-resistant grinding ball is high in tensile strength and free of out-of-round in use, is used for grinding iron ore, reduces the ball consumption per ton of ore by more than 25% compared with a common forged wear-resistant steel ball under the same working condition, has excellent wear resistance, and has good economic and social benefits in popularization and application.

Description

Technical Field

[0001] The invention discloses a method for preparing a forged grinding ball, in particular to a method for preparing a low-cost, high-performance, large-diameter forged grinding ball, and belongs to the technical field of wear-resistant material preparation. Background Art

[0002] Mills are widely used in many industries such as metallurgy, mining, building materials, electricity, fertilizers, coal, chemicals and pharmaceuticals. Grinding balls are important consumables in the use of mills. During the working process, the grinding balls are repeatedly lifted to a certain height and then dropped, and are gradually worn by the impact, friction and extrusion of the materials to be crushed and the liner of the ball mill. The grinding balls used in large semi-autogenous mills are lifted to a higher height, and the impact, friction and extrusion are more intense. Therefore, the grinding balls are required to have better performance, with both high hardness and wear resistance, as well as good toughness and impact resistance. In order to improve the grinding efficiency of materials, the large-scale mill is an inevitable trend. The large-scale mill leads to the large-scale size of the matching grinding balls. Although traditional cast chromium alloy cast iron grinding balls and ductile iron grinding balls can obtain high surface hardness (≥58HRC), they have many internal shrinkage holes, looseness and other defects, low impact toughness, high crushing rate, and are difficult to meet the use requirements. During the forging process, the microstructure of metal materials becomes more compact, making the impact resistance and crushing rate of forged grinding balls significantly better than those of cast grinding balls of the same material. At the same time, after forging, the austenite grains are broken and there is no time to recover and recrystallize and grow, so the grains of the grinding balls are fine, and the strength and hardness are improved. The rolling method can produce grinding balls with high efficiency, but the deformation depth is limited. It is generally used for small and medium diameter steel balls. Most high-performance large diameter grinding balls are produced by forging.

[0003] In order to reduce costs and improve the performance of large-diameter forged grinding balls, Chinese invention patent CN117286405A also discloses a high-hardness forged wear-resistant steel ball and a preparation method thereof. The high-hardness forged wear-resistant steel ball comprises, by mass fraction, C: 0.7% to 1.2%, Si: 0.2% to 0.6%, Mn: 0.7% to 1.3%, Cr: 0.2% to 2.0%, Ni: ≤0.25%, Mo: ≤0.2%, Cu: ≤0.2%, Al: ≤0.05%, P: ≤0.022%, S: ≤0.022%, and the rest are Fe and impurities. The preparation method comprises the following steps S1, preparing round steel, S2, forging steel balls, S3, quenching the steel balls, S4, tempering the steel balls, and S5, low temperature treatment; the low temperature treatment improves the degree of transformation of the martensitic structure, eliminates residual austenite to the greatest extent, refines the structure, and enables the grinding balls to have the characteristics of high hardness, high toughness, high strength, wear resistance, corrosion resistance, long life, and strong adaptability. Chinese invention patent CN116695002A also discloses a high-hardness and high-toughness wear-resistant steel ball and its preparation process. The element components and weight ratios of the wear-resistant steel ball are divided into: C: 0.95-1.1%; Si: 0.1-0.4%; Mn: 0.1-0.4%; S: 0.1-0.3%; P: 0.1-0.3%; Cr: 15.0-20.0%; Ni: 1.0-1.5%; Mo: 0.9-1.1%; V: 0.3-0.6%, Nb: 0.2-0.4%; Re: 0.02-0.04%; Cu: 0.7-1.1%, and the balance is Fe and inevitable impurities. The wear-resistant steel ball prepared by the invention, which is based on chromium and carbon as raw materials, and is supplemented by tungsten, manganese, niobium and other metal raw materials, and forged by forging technology, has good high hardness, high impact resistance, and high toughness performance, and can effectively improve the consistency of hardness, wear resistance, and smoothness of the steel ball, making it suitable for various fields and can be better promoted and used. Chinese invention patent CN115976427A also discloses a corrosion-resistant, high-wear-resistant, large-size forged steel ball for semi-autogenous grinding machine and a manufacturing method, which belongs to the field of metal material production technology. The corrosion-resistant and highly wear-resistant large-sized forged steel balls for semi-autogenous mills include the following components in mass percentage: C0.62-0.85%, Si1.50-2.00%, Mn0.8-1.50%, Cu0.52-1.0%, Cr0.5-1.0%, B0.002-0.0070%, P0.015-0.030%, S≤0.010%, and the balance is Fe and unavoidable impurities. The invention reduces the amount of precious metal elements added and adjusts the production process of large-sized wear-resistant steel balls by designing the composition of large-sized wear-resistant steel balls for large semi-autogenous mills, thereby reducing production costs, improving production efficiency, improving the wear resistance and toughness of large-sized wear-resistant steel balls, and improving the corrosion resistance of steel balls.Chinese invention patent CN111485180A also discloses a method for preparing a tempered martensitic wear-resistant steel ball with TiC particles precipitated in a complex phase, which belongs to the field of metal material processing technology. The wear-resistant steel ball is made of the following alloy components in weight percentage: C: 0.65-0.9wt.%, Si: 1.5-3.0wt.%, Mn: 0.5-2.0wt.%, Cr: 0.5-1.5wt.%, Ti: 1-2%, and the balance is Fe and inevitable impurities; through forging residual heat quenching (no need to heat again) + low temperature tempering process, a high-hardness tempered martensitic structure is obtained, and second-phase particles are precipitated in the matrix. The strength and wear resistance of the material are ensured by the dispersed second-phase particles of different scales. The nano-scale precipitated particles improve the strength of the matrix, while the micron-scale precipitated particles improve the wear resistance of the material. In this alloy system, adding different contents of Ti elements can significantly improve the comprehensive performance of the material. Chinese invention patent CN112853193A also discloses a method for preparing high-carbon grinding ball steel, which specifically includes scrap steel smelting, molten steel refining, vacuum degassing, continuous casting steel billet, steel billet cutting, forging, and heat treatment. In this invention, 0.50-0.65% Mn is added to the molten steel by weight, which enhances the hardness of the round steel and improves the wear resistance of the grinding ball. 0.30-0.40% Cr is added to the molten steel by weight, which can enhance the corrosion resistance of the round steel. During the smelting and refining process, Ar is always introduced, and vacuum treatment is performed to avoid oxidation of the molten steel. The cut steel billet is heated by an induction furnace, which makes it easy to control the heating temperature and heating speed during the forging process, so that the steel billet is not easy to produce surface decarburization and overheating during the insulation process, ensuring product quality. During the forging process, the time used for the pushing process of each steel billet is controlled to be not less than 5 minutes, which can ensure that the steel billet is burned through and has sufficient forging plastic deformation capacity. Chinese invention patent CN111286681A also discloses a high wear-resistant and low-cost steel for forged wet grinding balls and its preparation method. A medium-frequency induction furnace is used to produce cast steel with the following chemical composition (wt.%): C: 1.05-1.7, Si: 1.6-2.5, Cr: 1.5-2.5, Mn: 0.5-1.5, Mo: 0.5-2.0, P≤0.05, S≤0.02, and the balance is Fe. First, high-temperature homogenization treatment is carried out: the temperature is 1050-1100℃ and kept warm for 40-60min, and air cooling or mist cooling is carried out. Forging: heating to 1100-1130℃ and keeping warm for 60min, and air hammer forging. Stage isothermal quenching: the billets that still have residual heat after forging are quenched into nitrate salts of different salt compositions and temperatures in turn for keeping warm, and air cooling to room temperature. The grinding balls produced by this invention are used in large-scale wet grinding of ore without any breakage or loss of roundness, and have achieved super high wear resistance.Chinese invention patent CN110791619A also discloses a large-diameter forged grinding ball for mining and a preparation process thereof. The chemical composition mass percentage of the large-diameter forged grinding ball for mining is: 0.62%-0.67% C, 0.70%-1.00% Mn, 0.70%-1.20% Cr, 1.60%-1.90% Si, P≦0.03%, S≦0.03%, and the balance is Fe; the process comprises the following steps: step 1, preparation of raw materials: cutting round steel blanks with the same chemical composition into a certain length, heating to 1100-1200°C by induction heating, and then forging the grinding balls; step 2, quenching treatment: quenching treatment is performed by secondary spiral drum water cooling; step 3, tempering treatment: after quenching the grinding balls, low-temperature tempering treatment is promptly performed at 180-220°C for 10 hours, and then cooling. The invention obtains large-diameter forged grinding balls for mining with good comprehensive mechanical properties through reasonable forging process and heat treatment process. Chinese invention patent CN CN115838901A provides a high-toughness 60Mn forged grinding ball and its production method, with the composition: C: 0.60% to 0.65%; Si: 0.17% to 0.37%; Mn: 0.75% to 0.85%; Ti: 0.020% to 0.035%, N: 0.005% to 0.007%, P < 0.020%, S < 0.020%, and the balance is Fe and unavoidable impurities. Compared with the prior art, the invention adds microalloying element Ti, and produces dispersed TiN precipitates in steel through reasonable smelting and continuous casting processes. Such dispersed TiN precipitates will not dissolve during forging heating, and can pin the grain boundaries during and after forging, inhibiting the growth of dynamic recrystallization and static recrystallization grains, significantly refining the grain size, and combined with an adjusted heat treatment process, can significantly improve the impact toughness and service life of 60Mn forged grinding balls. Chinese invention patent CN110846586A also discloses a high-strength, high-toughness, and high-wear-resistant steel ball steel and its preparation method, which solves the problem that the strength and toughness of existing wear-resistant steel ball steel cannot meet the requirements at the same time and the uniformity is poor. The composition of the steel for wear-resistant steel balls is calculated by mass percentage as follows: C: 0.60%-0.70%, Si: 1.50%-1.80%, Mn: 0.92%-1.2%, Cr: 1.30%-2.00%, Mo: 0.01%-0.20%, Ni: 0.25%-0.60%, Al: 0.01%-0.05%, Cu: 0.05%-0.10%, V: 0.01%-0.20%, S≤0.03%, P: 0.01%-0.02%, and the rest is Fe and inevitable trace impurities, wherein (Mo+V)≥0.08%. The preparation method comprises the following steps: smelting molten steel, then casting to obtain an ingot; forging the ingot to obtain a billet; quenching and tempering the billet or quenching and partitioning the billet.The high-strength and high-toughness wear-resistant steel ball of the invention has good strength and toughness, good uniformity and wide application range. However, the forged grinding balls or forged steel balls generally have the disadvantages of large amount of alloy elements added and high manufacturing cost of the grinding balls.

[0004] Chinese invention patent CN118989230A discloses a rolling forging steel ball production line and forming process, which mainly relates to the field of steel ball processing. A rolling forging steel ball forming process includes: feeding; transferring the blanks one by one to the conveying device through the feeding device, and the conveying device conveys the blanks to the top forging machine at a uniform speed for horizontal forging; the time interval of each cycle of the cutting module and the forming die is consistent; rolling forging; the steel balls after horizontal forging are lifted by the elevator to the rolling forging machine for rolling forging; isothermal control; the temperature of the steel balls at the outlet is controlled by controlling the conveying rate of the isothermal equipment; quenching; the steel balls after isothermal control are quenched; tempering; the quenched steel balls are conveyed to the tempering furnace via the cooling bed for tempering. The beneficial effects of the invention are: the steel balls processed by the present invention have high overall hardness, uniform gradient distribution, high toughness, low wear, low breakage rate, almost no loss of roundness, strong acid and alkali corrosion resistance, etc. Chinese invention patent CN118122931A also discloses a CO2 protected forging process for wear-resistant steel balls, which relates to the field of forging technology, including: heating the blank material, the heating temperature range is 1050℃-1100℃, and the insulation time is 1h; using a hot shear to cut the blank; using a pneumatic forging hammer to forge the blank cut in step 2 into a steel ball, and air-cooling the steel ball to room temperature; reheating the steel ball obtained in step 3, the heating temperature range is 880℃-900℃, and the insulation time is 1h; then quenching the steel ball in a water pool; the present invention utilizes the CO2 generated during its own heating process to protect the entire steel ball forging process, so that the air is isolated from the forging blank, which can effectively reduce the occurrence of oxidation, reduce material loss and pollution, and is of great significance to improving material utilization, increasing output, and increasing the economic benefits of the enterprise. At the same time, it also has positive significance for improving the surface quality of steel balls, extending the service life of forging dies, and environmental protection. Chinese invention patent CN117000924A also discloses an online production process for forging steel balls with high hardness and high toughness, which relates to the field of steel ball forging production technology. In order to solve the problem that the steel ball forging device in the prior art uses a mold to achieve hot pressing shaping during hot forging operation, due to its circular shape, hot pressing is performed on a single side, which easily leads to uneven and rounded surfaces of other end faces, thus affecting the quality of its molding. The step 1: first prepare the raw materials. The main raw materials of the steel ball are carbon steel, alloy steel, and stainless steel metal materials. The materials are processed to become steel bars that meet the requirements; step 2: the steel bars are cut and cut into small pieces of a certain length. These small pieces are further processed to become steel balls that meet the requirements; step 3: the small pieces after cutting are heat treated, and the heat treatment improves the performance of the steel ball and improves its hardness, strength and toughness.Chinese invention patent CN116117053A also discloses a forging device for wear-resistant steel balls, including a frame and a forging unit installed on the frame, the forging unit including a z-direction forging assembly, an x-direction forging assembly and a y-direction forging assembly, and also including a clamping assembly for clamping a steel bar blank during z-direction forging, the clamping assembly including a positioning plate, a mounting rod, a spring, a pull rope, a winding wheel and a second motor. The invention performs multi-directional forging on the steel bar blank in sequence by arranging a z-direction forging assembly, an x-direction forging assembly and a y-direction forging assembly, and has a good forging effect, does not need to flip and adjust the angle of the steel bar blank, and improves work efficiency; a clamping assembly is provided, and the steel bar blank is clamped and positioned by two positioning plates during z-direction forging, so as to avoid the steel bar blank from tilting during z-direction forging and making it impossible to perform forging operation, and improves stability during z-direction forging. Chinese invention patent CN116197340A also discloses a forging process for wear-resistant steel balls with a diameter of ≥130mm, which belongs to the field of forging production technology of wear-resistant steel balls in the metallurgical industry. The technical scheme is: ① Heating: First, a round steel billet of a certain length is heated by a stepping bottom heating furnace, and the furnace temperature is 850-950℃; then an electric induction heater is used for supplementary heating, and the target temperature is 1050-1150℃; ② Forging and finishing; ③ Normalizing: The finished wear-resistant steel ball is air-cooled to 450-550℃; ④ Heating before quenching: The wear-resistant steel air-cooled to 450-550℃ is heated for the second time; ⑤ Quenching; ⑥ Tempering: The tempering temperature is 180-200℃, and it is naturally cooled after leaving the furnace. The beneficial effects of the present invention are: high production efficiency, low energy consumption, good hardness uniformity, and high toughness. Chinese invention patent CNCN115852131A also discloses a method for producing a high hardenability steel ball, which includes the following steps: S1, forging steel balls: the raw material of the steel balls is cylindrical steel material; it is placed in a heating furnace and heated to 1050-1200°C, kept warm for 20 minutes, placed in a forging machine to forge into steel balls, and then quenched with oil; S2, when the surface temperature of the steel ball drops to 60-80°C, it is heated to 800-900°C, kept warm for 50-60 minutes, quenched with water at a temperature of 30-40°C for 5-8s, tempered the steel ball, and then the tempering temperature is controlled between 200-260°C for 1-2h; S3, air cooling: air cooling the steel ball to the design temperature, pre-cooling the steel ball, so that the cooling rate curve of different areas of the steel ball is relatively gentle and the hardening depth is greater. The invention uses elements in different proportions to match each other, and uses residual heat to quench oil after forging, followed by secondary heating and quenching to match. The strength difference between the surface and the inside of the steel ball is small, and the hardenability and hardenability of the steel ball are greatly improved.Chinese invention patent CN114618981A also discloses a semi-automatic forging production method for steel balls, which comprises: S1, preparing steel bar blanks; S2, one-step forging and forming, forging the steel bar blanks once by a hydraulic press to obtain a semi-finished steel ball; S3, two-step forging and forming, and then forging the semi-finished steel ball obtained in S2 by an electro-hydraulic hammer at multiple angles and in multiple directions to obtain a steel ball formed product; S4, heat treating the steel ball; and also provides a semi-automatic forging production device for steel balls, comprising a hydraulic press and an electro-hydraulic hammer, the hydraulic press comprising a first upper die and a first lower die, the first upper die being provided with a first upper ball socket, the first lower die being provided with a first lower ball socket, the electro-hydraulic hammer comprising a second upper die and a second lower die, the second upper die being provided with a second upper ball socket, the second lower die being provided with a second lower ball socket; and has the effect of reducing the forging time and improving the production efficiency when forging a large number of steel balls. Chinese invention patent CN112501421A also discloses a wear-resistant steel ball heat treatment process using the residual heat of forging, including the following steps: 1) transmitting the wear-resistant steel balls at 800±50℃ after forging to the feed end of the double-layer material bed one by one; 2) the wear-resistant steel balls enter the lower track from the feed end, and roll freely along the lower track to the first ball outlet end, while the temperature of the wear-resistant steel balls is reduced to 550±10℃ under air cooling; 3) the wear-resistant steel balls transmitted from the first ball outlet end are lifted to the second ball outlet end of the upper track, and roll freely along the upper track to the second ball outlet end, the upper track is divided into two sections, the temperature of the wear-resistant steel balls in the front section is 350±10℃, and the temperature of the wear-resistant steel balls in the rear section is 200±5℃; 4) the wear-resistant steel balls are transmitted out of the double-layer material bed through the automatic ball discharge unit. On the one hand, the invention can use the residual heat of forged wear-resistant steel balls for preheating, thereby eliminating energy loss and waste and reducing production costs; on the other hand, it reduces the space occupied by the track. Chinese invention patent CN111299482A also discloses a steel ball forging production method, which includes: S1, preparing steel bar blanks; S2, forging the steel bar blanks in three directions in three-dimensional space to obtain steel balls, the three directions are perpendicular to each other, and the first forging is along the axial direction of the steel bar blank; S3, heat treating the steel balls. A steel ball forging production device is also provided, which includes: a forging die, the forging die includes an upper die and a lower die, the upper die is provided with an upper ball socket, and the lower die is provided with a lower ball socket; a manipulator, the manipulator is used to clamp the blank; the forging die and the manipulator cooperate to forge the steel bar blank in three directions, the three directions are perpendicular to each other, and the first forging is along the axial direction of the steel bar blank. It can reduce processing time, reduce labor and improve safety.Chinese invention patent CN110434274A also discloses a fully automated production system for large-diameter wear-resistant steel balls, including a pretreatment unit, a transfer and transportation unit, and a forging and forming unit. The pretreatment unit includes a natural gas heating furnace (1) and a roller (2). The natural gas heating furnace (1) is provided with a feed port and a discharge port, and the roller (2) is connected to the discharge port. The transfer unit includes a bar cutting module, and the bar cutting module includes a bar shear (5) which is docked with the roller (2) to shear the heated long bar into short bar; the forging and forming unit includes an electric screw press (9), a mold (10) and a rounding machine (12). The system of the invention adopts a screw press forging and forming to complete the fully automated production of the large-diameter wear-resistant steel balls. However, the production of grinding balls using the above process method has high equipment cost and high grinding ball manufacturing cost. Summary of the invention

[0005] The present invention aims to solve the problems of large diameter forged grinding balls, such as high equipment cost and large amount of alloy elements in the grinding balls, which lead to high production cost of the grinding balls. The present invention uses Q235 scrap steel and waste high manganese steel as main raw materials, adds a small amount of ferroboron, ferrotitanium and carburizer, optimizes the grinding ball forging process and heat treatment process on this basis, and thus obtains low-cost and high-performance large diameter forged grinding balls.

[0006] The present invention provides a method for preparing a low-cost, high-performance, large-diameter forged grinding ball, which is characterized in that the specific preparation process steps are:

[0007] ①Use Q235 scrap steel and waste high manganese steel ZG120Mn13 as the main raw materials, add a small amount of ferroboron, aluminum-magnesium alloy, ferrotitanium and carburizer, and use an electric furnace to smelt molten steel; use 76.5-77.0% Q235 scrap steel, 20.5-21.0% waste high manganese steel ZG120Mn13, 0.8-1.0% carburizer, 0.8-0.9% ferrotitanium, 0.50-0.55% ferroboron and 0.20-0.25% aluminum-magnesium alloy ingredients, the total mass fraction of the charge is 100%; first heat and melt the scrap high manganese steel ZG120Mn13 with a mass fraction of 20.5-21.0%, and then melt the Q235 scrap steel with a mass fraction of 76.5-77.0% and 0.8-1.0% of the carburizer into the furnace, then heat the molten steel to 1628-1643℃, and then insert a 18-20m diameter m aluminum-magnesium alloy bar, the amount of aluminum-magnesium alloy added accounts for 0.20-0.25% of the total mass fraction of the charge; the surface of the aluminum-magnesium alloy bar is coated with a passivation layer, the thickness of the passivation layer is 0.25-0.30mm, the chemical composition and mass fraction of the passivation layer are: 30-33% aluminum oxide, 38-41% iron oxide, 28-30% magnesium oxide; the passivation layer uses water glass as a binder, and the amount of water glass added in the passivation layer accounts for After 6-8 minutes of heat preservation, add 0.8-0.9% of ferrotitanium by mass, and continue to keep warm for 8-10 minutes before all the molten steel is discharged into the ladle; when 1 / 3 to 1 / 2 of the molten steel in the furnace has entered the ladle, add ferroboron with a particle size of 4-8mm and preheated at 650-750℃ for 120-150 minutes into the ladle, and the amount of ferroboron added accounts for 0.50-0.55% of the total mass fraction of the charge;

[0008] ② After the molten steel in the ladle is deslagging and standing, when the temperature drops to 1531-1544°C, the molten steel is poured into the crystallizer on the continuous casting machine and continuously cast into square billets. The size of the square billets is preferably 240mm×240mm, and the square billets are directly rolled into cylindrical steel with a diameter of Φ100-110mm on the rolling mill;

[0009] ③ The cylindrical steel with a diameter of Φ100-110mm obtained in step ② is heated to 1180-1230℃ by a walking natural gas heating furnace, kept warm for 80-100 minutes, and then sheared into a cylinder with a length of 220-275mm required for a single ball by a rod shearing machine, and the cylinder is rough-forged by a CNC hammer, and the deformation amount is controlled at 8-10% each time. After 5-8 deformations, a blank grinding ball is obtained; then the blank grinding ball is fine-forged by an air hammer to obtain a Φ150mm-170mm grinding ball;

[0010] ④ When the surface temperature of the grinding ball after fine forging in step ③ drops to 835-870°C, it is placed in a water glass quenching liquid pool for quenching, wherein the mass concentration of water glass in the quenching liquid pool is 8.5%-10%; the temperature of the water glass quenching liquid is 25-38°C, and the mass ratio of the water glass quenching liquid to the grinding ball in the water glass quenching liquid pool is greater than 12:1; after the grinding ball is cooled in the water glass quenching liquid pool for 8-10 minutes, the grinding ball is quickly taken out and rinsed in clean water; and the quenched and rinsed grinding ball is tempered at 180-195°C for 16-18 hours, furnace cooled to a temperature below 150°C, and air cooled to room temperature after being taken out of the furnace, thereby obtaining a low-cost, high-performance, large-diameter forged grinding ball.

[0011] As mentioned above, the chemical composition and mass fraction of Q235 scrap steel are: 0.14-0.22% C, 0.30-0.65% Mn, 0.15-0.32% Si, ≤0.050% S, ≤0.045% P, the remainder Fe and other inevitable elements.

[0012] As mentioned above, the chemical composition and mass fraction of the scrap high manganese steel ZG120Mn13 are: 1.05-1.35% C, 0.30-0.90% Si, 11.00-14.00% Mn, ≤0.060% P, ≤0.040% S, the remainder Fe and other inevitable elements.

[0013] As mentioned above, the chemical composition and mass fraction of ferrotitanium are: 69.05-71.72% Ti, 1.54-2.19% Al, <0.5% Si, and the remainder is Fe and unavoidable impurities.

[0014] As mentioned above, the chemical composition and mass fraction of ferroboron are: 19.27-20.88% B, ≤0.5% C, ≤2% Si, ≤0.5% Al, ≤0.01% S, ≤0.1% P, and the remainder is Fe and unavoidable impurities.

[0015] As mentioned above, the chemical composition and mass fraction of the aluminum-magnesium alloy are: 91.5-92.0% Al, 8.0-8.5% Mg.

[0016] As mentioned above, the mass fraction of carbon in the recarburizer is greater than 98.9%.

[0017] In order to solve the problems of high equipment cost and high production cost of grinding balls caused by large-diameter forged grinding balls, the present invention proposes to use cheap Q235 scrap steel and waste high-manganese steel as the main raw materials to reduce the manufacturing cost of grinding balls. In order to improve the hardness and wear resistance of the grinding balls, a small amount of ferroboron, ferrotitanium and carburizer are added. On this basis, by optimizing the grinding ball forging and heat treatment process, low-cost and high-performance large-diameter forged grinding balls can be obtained. The specific preparation process steps are:

[0018] The present invention uses cheap and easily available Q235 scrap steel (the chemical composition and mass fraction of the Q235 scrap steel are: 0.14-0.22% C, 0.30-0.65% Mn, 0.15-0.32% Si, ≤0.050% S, ≤0.045% P, the balance is Fe and other inevitable elements) and waste high manganese steel ZG120Mn13 (the chemical composition and mass fraction of the waste high manganese steel ZG120Mn13 are: 1.05-1.35% C, 0.30-0.90% Si, 11.00-14.00% Mn, ≤0.060% P, ≤0.040% S, the balance is Fe and other inevitable elements) as main raw materials. High manganese steel is a widely used wear-resistant material, commonly used in mining, building materials, thermal power, chemical industry, metallurgy and other mechanical equipment, to make excavator shovel teeth, cone crusher mortar wall and crushing wall, jaw crusher liner, ball mill liner, railway switch, plate hammer, hammer head, with an annual production of hundreds of thousands of tons, and a large amount of waste high manganese steel is generated after use. Using Q235 scrap steel and scrap high manganese steel ZG120Mn13 as the main raw materials to produce grinding balls can achieve efficient utilization of scrap steel. On this basis, a small amount of ferroboron (the chemical composition and mass fraction of the ferroboron are: 19.27-20.88% B, ≤0.5% C, ≤2% Si, ≤0.5% Al, ≤0.01% S, ≤0.1% P, the balance is Fe and inevitable impurities), aluminum-magnesium alloy (the chemical composition and mass fraction of the aluminum-magnesium alloy are: 91.5-92.0% Al, 8.0-8.5% Mg), ferrotitanium (the chemical composition and mass fraction of the ferrotitanium are: 69.05-71.72% Ti, 1.54-2.19% Al, <0.5% Si, the balance is Fe and inevitable impurities) and recarburizer (the mass fraction of carbon in the recarburizer is greater than 98.9%) are added, and the molten steel is smelted in an electric furnace. 76.5-77.0% of Q235 scrap steel, 20.5-21.0% of waste high manganese steel ZG120Mn13, 0.8-1.0% of carburizer, 0.8-0.9% of ferrotitanium, 0.50-0.55% of ferroboron and 0.20-0.25% of aluminum-magnesium alloy are used, and the total mass fraction of the charge is 100%.

[0019] Scrap high manganese steel ZG120Mn13 contains 11.00-14.00% Mn and 1.05-1.35% C, has a low melting temperature and is easy to melt. The present invention first heats and melts scrap high manganese steel ZG120Mn13 with a mass fraction of 20.5-21.0%, and then melts Q235 scrap steel with a mass fraction of 76.5-77.0% and 0.8-1.0% of recarburizer into a furnace. Q235 scrap steel has a low carbon content, a high melting point, and is difficult to melt. Directly adding it to the scrap high manganese steel ZG120Mn13 melt can increase the melting rate of Q235 scrap steel and reduce the oxidation and burning of iron elements. In addition, adding the recarburizer to the scrap high manganese steel ZG120Mn13 melt can significantly increase the absorption rate of carbon in molten steel and reduce the oxidation and burning of the recarburizer. Then, the molten steel is heated to 1628-1643°C, and then an aluminum-magnesium alloy rod with a diameter of 18-20 mm is inserted into the molten steel. The chemical composition and mass fraction of the aluminum-magnesium alloy are: 91.5-92.0% Al, 8.0-8.5% Mg, and the amount of the aluminum-magnesium alloy added accounts for 0.20-0.25% of the total mass fraction of the furnace charge. Since the present invention uses Q235 scrap steel and waste high manganese steel ZG120Mn13 as main raw materials to smelt molten steel, there are many oxygen, hydrogen and non-metallic inclusions in the molten steel, which seriously affects the quality of the cast product. The oxygen, hydrogen and non-metallic inclusions in the molten steel cannot be removed by simply using aluminum deoxidation.

[0020] The present invention adds magnesium element to aluminum metal to obtain aluminum-magnesium alloy, and the amount of aluminum-magnesium alloy added accounts for 0.20-0.25% of the total mass fraction of the furnace charge. Since the aluminum-magnesium alloy contains 8.0-8.5% Mg, it has excellent deoxidation, desulfurization and dehydrogenation effects, and can also significantly reduce the number of inclusions, thereby significantly improving the quality of the cast square billet product, and indirectly improving the performance of the square billet product forged into grinding balls. However, the magnesium element has a low boiling point and is easily gasified when directly added to molten steel, causing the molten steel to violently churn, which seriously affects safe production. The present invention coats a passivation layer on the surface of the aluminum-magnesium alloy bar material, the thickness of the passivation layer is 0.25-0.30mm, and the chemical composition and mass fraction of the passivation layer are: 30-33% aluminum oxide, 38-41% iron oxide, and 28-30% magnesium oxide; the passivation layer uses water glass as a binder, and the amount of water glass added to the passivation layer accounts for 1.2-1.3% of the mass fraction of the passivation layer. This can ensure that the aluminum-magnesium alloy rod reacts smoothly in the molten steel, ensuring safety during the steelmaking process and preventing the molten steel from splashing out of the furnace.

[0021] After the heat preservation for 6-8 minutes, the method adds 0.8-0.9% ferrotitanium by mass, and after the heat preservation for 8-10 minutes, all the molten steel is discharged from the furnace into the ladle; when the molten steel in the furnace enters 1 / 3 to 1 / 2 of the ladle, ferroboron with a particle size of 4-8 mm and preheated at 650-750°C for 120-150 minutes is added into the ladle, and the amount of ferroboron added accounts for 0.50-0.55% of the total mass fraction of the furnace charge. The titanium element in the ferrotitanium and the boron element in the ferroboron can be combined to generate high-hardness TiB2, which significantly improves the hardness and wear resistance of the grinding ball. Part of the boron element is solid-dissolved in the iron matrix, which significantly improves the hardenability of the grinding ball. After the molten steel in the ladle is slag-stripped and left to stand, when the temperature drops to 1531-1544℃, the molten steel is poured into the crystallizer on the continuous casting machine and continuously cast into 240mm×240mm square billets, and the square billets are directly rolled into cylindrical steel with a diameter of Φ100-110mm on the rolling mill. Combining square billet continuous casting and square billet rolling can achieve low energy consumption and high efficiency production. Then the cylindrical steel is heated to 1180-1230℃ by a stepping natural gas heating furnace, kept warm for 80-100 minutes, and then sheared into a cylinder with a length of 220-275mm required for a single ball by a rod shearing machine, and the cylinder is roughly forged with a CNC hammer, and the deformation amount is controlled at 8-10% each time. After 5-8 deformations, the blank grinding ball is obtained; then the blank grinding ball is finely forged with an air hammer to obtain a Φ150mm-170mm grinding ball.

[0022] In order to further improve the hardness and wear resistance of the grinding balls, when the surface temperature of the grinding balls after fine forging drops to 835-870°C, the grinding balls are quenched in a water glass quenching liquid pool, and the water glass concentration in the quenching liquid pool is 8.5%-10%; the water glass quenching liquid temperature is 25-38°C, and the mass ratio of the water glass quenching liquid to the grinding balls in the water glass quenching liquid pool is greater than 12:1. Compared with direct quenching with aqueous solution, the cooling rate of the water glass quenching liquid is lower than the cooling rate of the aqueous solution quenching, which overcomes the shortcoming that the large direct grinding balls quenched with aqueous solution are prone to cracking due to too fast cooling rate. Compared with direct quenching with quenching oil, the cooling rate of the water glass quenching liquid is higher than the cooling rate of the quenching oil quenching, which overcomes the shortcoming that the large direct grinding balls quenched with quenching oil have low hardness in the core due to too slow cooling rate. Water glass quenching liquid is an environmentally friendly quenching medium with the characteristics of low cost, easy availability, non-flammable and non-explosive. Compared with other quenching liquids, it is safer and more reliable. The basic component of water glass quenching liquid is sodium silicate aqueous solution. Compared with other quenching liquids, water glass quenching liquid has higher operating safety and is simple to operate. As an environmentally friendly quenching liquid, water glass quenching liquid has relatively low cost, does not cause pollution to the environment, and has better economy. In the quenching process of water glass, water glass and water need to be mixed in a certain proportion first. According to the diameter of the grinding ball, the concentration of water glass in the quenching liquid is controlled at 8.5%-10%. In the quenching process, the sodium silicate in the water glass reacts with the metal to form silicate. Due to the intensity of this reaction, the grinding ball can obtain high-hardness martensite + appropriate amount of bainite + a small amount of residual austenite, ensuring that the grinding ball has excellent wear resistance. After the grinding ball of the present invention is cooled in the water glass quenching liquid pool for 8-10 minutes, the grinding ball is quickly taken out and rinsed in clean water to remove the silicate remaining on the surface of the grinding ball. The quenched and rinsed grinding ball is tempered at 180-195°C for 16-18 hours to eliminate the internal stress of the grinding ball quenching. The furnace is cooled to a temperature below 150°C and then air-cooled to room temperature to obtain low-cost, high-performance large-diameter forged grinding balls.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The grinding balls of the present invention are made of cheap and easily available Q235 scrap steel and waste high manganese steel ZG120Mn13 as main raw materials, without adding ferrosilicon, ferromanganese, ferrochrome and other iron alloys, nor expensive alloy elements such as molybdenum, nickel, vanadium, niobium, etc., but only adding a small amount of ferrotitanium and ferroboron, and have a lower production cost, which is more than 35% lower than that of ordinary forged wear-resistant steel balls;

[0025] (2) The present invention realizes efficient and safe utilization of scrap steel and waste high manganese steel by coating a passivation layer on the surface of the aluminum-magnesium alloy bar, thereby significantly reducing environmental pollution;

[0026] (3) The present invention uses square billets to roll into round steel, performs rough forging on the round steel with a large compression ratio to obtain blank grinding balls, and uses an air hammer to finely forge the blank grinding balls. The obtained grinding balls have a denser and finer structure, are free of defects such as pores, shrinkage cavities, and looseness, have a small diameter deviation, and are strictly controlled in size;

[0027] (4) The quenching method of the present invention is to quench in a water glass quenching liquid. Under the condition of ensuring the quenching quality, the use of the water glass quenching liquid for quenching will save costs compared with the use of quenching oil, and also prevent the direct use of water to quench large diameter high carbon steel grinding balls, which is prone to cracking accidents;

[0028] (5) The wear-resistant grinding balls of the present invention have the characteristics of high strength, high hardness, high wear resistance and impact resistance. The surface hardness can reach 61-63HRC, and the hardness distribution is uniform. The hardness difference between the inside and outside is small. The hardness difference of the same section is less than 3HRC. There are no defects such as quenching soft spots. The wear-resistant grinding balls of the present invention have good impact performance. The unnotched impact toughness value of the Φ150mm-170mm grinding ball can reach 40J / cm 2 The above ensures that the grinding balls will not crack or peel off when used in large grinding mills; the tensile strength of the wear-resistant grinding balls of the present invention exceeds 1250MPa, ensuring that the grinding balls will not lose their roundness during use; the grinding balls of the present invention are used in ball mills larger than Φ5m and semi-autogenous grinding mills larger than Φ10m to grind iron ore. Under the same working conditions, the ball consumption per ton of ore is reduced by more than 25% compared with ordinary forged wear-resistant steel balls, and the balls have excellent wear resistance. Popularization and application of the products of the present invention have good economic and social benefits. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the examples, but the present invention is not limited to the following examples.

[0030] Embodiment 1:

[0031] The preparation method of low-cost, high-performance large-diameter forged grinding balls uses Q235 scrap steel and waste high-manganese steel as the main raw materials, and then adds a small amount of ferroboron, ferrotitanium and carburizer. On this basis, the grinding ball forging process and heat treatment process are optimized to obtain low-cost, high-performance large-diameter forged grinding balls. The specific preparation process steps are:

[0032] ① Q235 scrap steel (the chemical composition and mass fraction of the Q235 scrap steel are: 0.19% C, 0.51% Mn, 0.26% Si, 0.040% S, 0.043% P, the balance is Fe and other inevitable elements), scrap high manganese steel ZG120Mn13 (the chemical composition and mass fraction of the scrap high manganese steel ZG120Mn13 are: 1.26% C, 0.73% Si, 12.82% Mn, 0.054% P, 0.029% S, the balance is Fe and other inevitable elements) Other elements) are used as the main raw materials, and then a small amount of ferroboron (the chemical composition and mass fraction of the ferroboron are: 19.75% B, 0.32% C, 1.64% Si, 0.33% Al, 0.009% S, 0.065% P, the balance is Fe and inevitable impurities), aluminum-magnesium alloy (the chemical composition and mass fraction of the aluminum-magnesium alloy are: 91.8% Al, 8.2% Mg), ferrotitanium (the chemical composition and mass fraction of the ferrotitanium are: 70.61% Ti, 1.87% Al, 0.26% Si, the balance is Fe and inevitable impurities) and a recarburizer (the mass fraction of carbon in the recarburizer is greater than 98.9%), and an electric furnace is used to smelt molten steel; 76.8% of Q235 scrap steel, 20.7% of waste high manganese steel ZG120Mn13, 0.85% of recarburizer, 0.85% of ferrotitanium, 0.55% of ferroboron and 0.25% of aluminum-magnesium alloy ingredients are used, and the total mass fraction of the furnace charge is 100%; firstly, the waste high manganese steel ZG120Mn13 with a mass fraction of 20.7% is heated and melted, and then the Q235 scrap steel with a mass fraction of 76.8% and the recarburizer with a mass fraction of 0.85% are melted in the furnace, and then the molten steel is heated to 1636°C, and then an aluminum-magnesium alloy rod with a diameter of 19 mm is inserted into the molten steel , the amount of aluminum-magnesium alloy added accounts for 0.25% of the total mass fraction of the charge; the surface of the aluminum-magnesium alloy bar is coated with a passivation layer, the thickness of the passivation layer is 0.25-0.30mm, and the chemical composition and mass fraction of the passivation layer are: 32% aluminum oxide, 39% iron oxide, and 29% magnesium oxide; the passivation layer uses water glass as a binder, and the amount of water glass added to the passivation layer accounts for 1.25% of the mass fraction of the passivation layer; after keeping warm for 7 minutes, add titanium iron with a mass fraction of 0.85%, and continue to keep warm for 9 minutes before all the molten steel is discharged from the furnace into the ladle; when the molten steel in the furnace enters 1 / 3 to 1 / 2 of the ladle, add ferroboron with a particle size of 4-8mm and preheated at 710℃ for 130 minutes into the ladle, and the amount of ferroboron added accounts for 0.55% of the total mass fraction of the charge;

[0033] ② After the molten steel in the ladle is slag-stripped and left to stand, when the temperature drops to 1537℃, the molten steel is poured into the crystallizer on the continuous casting machine and continuously cast into 240mm×240mm square billets, which are then directly rolled into cylindrical steel with a diameter of Φ105mm on the rolling mill;

[0034] ③ The cylindrical steel with a diameter of Φ105 mm obtained in step ② is heated to 1200°C by a walking natural gas heating furnace, kept warm for 90 minutes, and then sheared into a cylinder with a length of 247.7 mm required for a single ball by a rod shearing machine, and the cylinder is rough-forged by a CNC hammer, and the deformation amount is controlled at 9% each time. After 7 deformations, a blank grinding ball is obtained; then the blank grinding ball is fine-forged by an air hammer to obtain a Φ160 mm grinding ball;

[0035] ④ When the surface temperature of the grinding ball after fine forging in step ③ drops to 837-866°C, it is quenched in a water glass quenching liquid pool, and the water glass concentration in the quenching liquid pool is 9.5%; the temperature of the water glass quenching liquid is 31°C, and the mass ratio of the water glass quenching liquid to the grinding ball in the water glass quenching liquid pool is greater than 12:1; after the grinding ball is cooled in the water glass quenching liquid pool for 9 minutes, the grinding ball is quickly taken out and rinsed in clean water; and the quenched and rinsed grinding ball is tempered at 190°C for 17 hours, furnace cooled to a temperature below 150°C, and air cooled to room temperature after being taken out of the furnace, so that low-cost, high-performance large-diameter forged grinding balls can be obtained, and their mechanical properties are shown in Table 1.

[0036] Embodiment 2:

[0037] The preparation method of low-cost, high-performance large-diameter forged grinding balls uses Q235 scrap steel and waste high-manganese steel as the main raw materials, and then adds a small amount of ferroboron, ferrotitanium and carburizer. On this basis, the grinding ball forging process and heat treatment process are optimized to obtain low-cost, high-performance large-diameter forged grinding balls. The specific preparation process steps are:

[0038] ① Q235 scrap steel (the chemical composition and mass fraction of the Q235 scrap steel are: 0.22% C, 0.30% Mn, 0.32% Si, 0.041% S, 0.042% P, the balance is Fe and other inevitable elements), scrap high manganese steel ZG120Mn13 (the chemical composition and mass fraction of the scrap high manganese steel ZG120Mn13 are: 1.35% C, 0.37% Si, 13.68% Mn, 0.055% P, 0.035% S, the balance is Fe and other inevitable elements) Other elements) are used as the main raw materials, and a small amount of ferroboron (the chemical composition and mass fraction of the ferroboron are: 20.88% B, 0.18% C, 0.95% Si, 0.31% Al, 0.007% S, 0.084% P, the balance is Fe and unavoidable impurities), aluminum-magnesium alloy (the chemical composition and mass fraction of the aluminum-magnesium alloy are: 92.0% Al, 8.0% Mg), ferrotitanium (the chemical composition and mass fraction of the ferrotitanium are: 71.72% Ti, 1.54% Al, 0.30% Si, the balance is Fe and inevitable impurities) and a recarburizer (the mass fraction of carbon in the recarburizer is greater than 98.9%), and an electric furnace is used to smelt molten steel; 77.0% of Q235 scrap steel, 20.5% of waste high manganese steel ZG120Mn13, 1.0% of recarburizer, 0.8% of ferrotitanium, 0.50% of ferroboron and 0.20% of aluminum-magnesium alloy ingredients are used, and the total mass fraction of the furnace charge is 100%; firstly, the waste high manganese steel ZG120Mn13 with a mass fraction of 20.5% is heated and melted, and then the Q235 scrap steel with a mass fraction of 77.0% and 1.0% of the recarburizer are melted in the furnace, and then the molten steel is heated to 1628°C, and then an aluminum-magnesium alloy rod with a diameter of 18mm is inserted into the molten steel, The amount of aluminum-magnesium alloy added accounts for 0.20% of the total mass fraction of the charge; the surface of the aluminum-magnesium alloy bar is coated with a passivation layer, the thickness of the passivation layer is 0.25-0.30mm, and the chemical composition and mass fraction of the passivation layer are: 30% aluminum oxide, 41% iron oxide, and 29% magnesium oxide; the passivation layer uses water glass as a binder, and the amount of water glass added to the passivation layer accounts for 1.2% of the mass fraction of the passivation layer; after keeping warm for 8 minutes, add titanium iron with a mass fraction of 0.8%, and keep warm for 10 minutes before all the molten steel is discharged from the furnace into the ladle; when 1 / 3 to 1 / 2 of the molten steel in the furnace enters the ladle, add ferroboron with a particle size of 4-8mm and preheated at 650°C for 150 minutes into the ladle, and the amount of ferroboron added accounts for 0.50% of the total mass fraction of the charge;

[0039] ② After the molten steel in the ladle is slag-stripped and left to stand, when the temperature drops to 1531℃, the molten steel is poured into the crystallizer on the continuous casting machine and continuously cast into 240mm×240mm square billets, which are then directly rolled into cylindrical steel with a diameter of Φ110mm on the rolling mill;

[0040] ③ The cylindrical steel with a diameter of Φ110 mm obtained in step ② is heated to 1230°C by a walking natural gas heating furnace, kept warm for 80 minutes, and then sheared into a cylinder with a length of 270.7 mm required for a single ball by a rod shearing machine, and the cylinder is rough-forged by a CNC hammer, and the deformation amount is controlled at 10% each time. After 5 deformations, a blank grinding ball is obtained; then the blank grinding ball is fine-forged by an air hammer to obtain a Φ170 mm grinding ball;

[0041] ④ When the surface temperature of the grinding ball after fine forging in step ③ drops to 842-870°C, it is placed in a water glass quenching liquid pool for quenching, and the water glass concentration in the quenching liquid pool is 10%; the temperature of the water glass quenching liquid is 25°C, and the mass ratio of the water glass quenching liquid to the grinding ball in the water glass quenching liquid pool is greater than 12:1; after the grinding ball is cooled in the water glass quenching liquid pool for 9 minutes, the grinding ball is quickly taken out and rinsed in clean water; and the quenched and rinsed grinding ball is tempered at 195°C for 16 hours, furnace cooled to a temperature below 150°C, and air cooled to room temperature after being taken out of the furnace, thereby obtaining a low-cost, high-performance large-diameter forged grinding ball, and its mechanical properties are shown in Table 1.

[0042] Embodiment 3:

[0043] The preparation method of low-cost, high-performance large-diameter forged grinding balls uses Q235 scrap steel and waste high-manganese steel as the main raw materials, and then adds a small amount of ferroboron, ferrotitanium and carburizer. On this basis, the grinding ball forging process and heat treatment process are optimized to obtain low-cost, high-performance large-diameter forged grinding balls. The specific preparation process steps are:

[0044] ① Q235 scrap steel (the chemical composition and mass fraction of the Q235 scrap steel are: 0.14% C, 0.65% Mn, 0.15% Si, 0.047% S, 0.044% P, the balance is Fe and other inevitable elements), scrap high manganese steel ZG120Mn13 (the chemical composition and mass fraction of the scrap high manganese steel ZG120Mn13 are: 1.05% C, 0.87% Si, 11.23% Mn, 0.051% P, 0.035% S, the balance is Fe and other inevitable elements) Other elements) are used as the main raw materials, and then a small amount of ferroboron (the chemical composition and mass fraction of the ferroboron are: 19.27% ​​B, 0.29% C, 1.25% Si, 0.36% Al, 0.008% S, 0.064% P, the balance is Fe and inevitable impurities), aluminum-magnesium alloy (the chemical composition and mass fraction of the aluminum-magnesium alloy are: 91.5% Al, 8.5% Mg), ferrotitanium (the chemical composition and mass fraction of the ferrotitanium are: 69.05% Ti, 2.19% Al, 0.28% Si, the balance is Fe and inevitable impurities) and a recarburizer (the mass fraction of carbon in the recarburizer is greater than 98.9%), and an electric furnace is used to smelt molten steel; 76.5% of Q235 scrap steel, 21.0% of waste high manganese steel ZG120Mn13, 0.8% of recarburizer, 0.9% of ferrotitanium, 0.55% of ferroboron and 0.25% of aluminum-magnesium alloy ingredients are used, and the total mass fraction of the furnace charge is 100%; firstly, the waste high manganese steel ZG120Mn13 with a mass fraction of 21.0% is heated and melted, and then the Q235 scrap steel with a mass fraction of 76.5% and the recarburizer with a mass fraction of 0.8% are melted in the furnace, and then the molten steel is heated to 1643°C, and then an aluminum-magnesium alloy rod with a diameter of 20 mm is inserted into the molten steel , the amount of aluminum-magnesium alloy added accounts for 0.25% of the total mass fraction of the charge; the surface of the aluminum-magnesium alloy bar is coated with a passivation layer, the thickness of the passivation layer is 0.25-0.30mm, and the chemical composition and mass fraction of the passivation layer are: 33% aluminum oxide, 39% iron oxide, and 28% magnesium oxide; the passivation layer uses water glass as a binder, and the amount of water glass added to the passivation layer accounts for 1.2% of the mass fraction of the passivation layer; after keeping warm for 6 minutes, add 0.9% titanium iron by mass, and continue to keep warm for 9 minutes before all the molten steel is discharged from the furnace into the ladle; when the molten steel in the furnace enters 1 / 3 to 1 / 2 of the ladle, add ferroboron with a particle size of 4-8mm and preheated at 750℃ for 120 minutes into the ladle, and the amount of ferroboron added accounts for 0.55% of the total mass fraction of the charge;

[0045] ② After the molten steel in the ladle is slag-stripped and left to stand, when the temperature drops to 1544℃, the molten steel is poured into the crystallizer on the continuous casting machine and continuously cast into 240mm×240mm square billets, which are then directly rolled into cylindrical steel with a diameter of Φ100mm on the rolling mill;

[0046] ③ The cylindrical steel with a diameter of Φ100 mm obtained in step ② is heated to 1180°C by a walking natural gas heating furnace, kept warm for 100 minutes, and then sheared into a cylinder with a length of 225 mm required for a single ball by a rod shearing machine, and the cylinder is rough-forged by a CNC hammer, and the deformation amount is controlled at 8% each time. After 8 deformations, a blank grinding ball is obtained; then the blank grinding ball is fine-forged by an air hammer to obtain a Φ150 mm grinding ball;

[0047] ④ When the surface temperature of the grinding ball after fine forging in step ③ drops to 835-860°C, it is placed in a water glass quenching liquid pool for quenching, and the water glass concentration in the quenching liquid pool is 8.5%; the temperature of the water glass quenching liquid is 38°C, and the mass ratio of the water glass quenching liquid to the grinding ball in the water glass quenching liquid pool is greater than 12:1; after the grinding ball is cooled in the water glass quenching liquid pool for 8 minutes, the grinding ball is quickly taken out and rinsed in clean water; and the quenched and rinsed grinding ball is tempered at 180°C for 18 hours, furnace cooled to a temperature below 150°C, and air cooled to room temperature after being taken out of the furnace, thereby obtaining a low-cost, high-performance large-diameter forged grinding ball, and its mechanical properties are shown in Table 1.

[0048] Table 1 Mechanical properties of grinding balls

[0049]

[0050] The grinding ball of the present invention uses cheap and easily available Q235 scrap steel and waste high manganese steel ZG120Mn13 as main raw materials, does not add ferrosilicon, ferromanganese and ferrochrome and other iron alloys, does not add expensive alloy elements such as molybdenum, nickel, vanadium, niobium, etc., only adds a small amount of ferrotitanium and ferroboron, has a lower production cost, and the production cost is reduced by more than 35% compared with ordinary forged wear-resistant steel balls. The present invention realizes the efficient and safe utilization of scrap steel and waste high manganese steel by coating a passivation layer on the surface of aluminum-magnesium alloy rods, and significantly reduces environmental pollution. The present invention uses square billets to roll into round steel, rough forges the round steel with a large compression ratio to obtain blank grinding balls, and fine forges the blank grinding balls with an air hammer, so that the obtained grinding balls have a more dense and fine structure, are free of defects such as pores, shrinkage cavities, looseness, etc., and have a small diameter deviation and strict size control. The quenching method of the present invention is to carry out quenching in a water glass quenching liquid. Under the condition of ensuring the quenching quality, the use of water glass quenching liquid for quenching will save costs compared with the use of quenching oil, and also prevent the large diameter high carbon steel grinding balls from cracking accidents that are prone to occur when directly quenching with water. The wear-resistant grinding balls of the present invention have the characteristics of high strength, high hardness, high wear resistance and impact resistance. The surface hardness can reach 61-63HRC, and the hardness distribution is uniform. The hardness difference between the inside and outside is small. The hardness difference of the same section is less than 3HRC, and there are no defects such as quenching soft spots. The wear-resistant grinding balls of the present invention have good impact performance. The unnotched impact toughness value of the Φ150mm-170mm grinding balls can reach 40J / cm 2The above ensures that the grinding balls will not crack or peel off when used in large mills. The tensile strength of the wear-resistant grinding balls of the present invention exceeds 1250MPa, ensuring that the grinding balls will not lose their roundness during use. The grinding balls of the present invention have been used in ball mills larger than Φ5m and semi-autogenous mills larger than Φ10m for grinding iron ore. Under the same working conditions, the ball consumption per ton of ore is reduced by more than 25% compared with ordinary forged wear-resistant steel balls, and have excellent wear resistance. The use of the products of the present invention can reduce the consumption of grinding balls, reduce the labor intensity of workers, and improve the grinding efficiency. The promotion and application of the products has good economic and social benefits.

Claims

1. A method for preparing low-cost, high-performance, large-diameter forged grinding balls, characterized in that: Q235 scrap steel and waste high manganese steel are used as the main raw materials, and a small amount of ferroboron, ferrotitanium, aluminum-magnesium alloy and carburizer are added. The molten steel is poured into a billet, and the billet is processed into a grinding ball through rolling and forging. The specific preparation process steps include the following: ①Use Q235 scrap steel and waste high manganese steel ZG120Mn13 as the main raw materials, add a small amount of ferroboron, aluminum-magnesium alloy, ferrotitanium and carburizer, and use an electric furnace to smelt molten steel; use 76.5-77.0% Q235 scrap steel, 20.5-21.0% waste high manganese steel ZG120Mn13, 0.8-1.0% carburizer, 0.8-0.9% ferrotitanium, 0.50-0.55% ferroboron and 0.20-0.25% aluminum-magnesium alloy ingredients, the total mass fraction of the charge is 100%; first heat and melt the scrap high manganese steel ZG120Mn13 with a mass fraction of 20.5-21.0%, and then melt the Q235 scrap steel with a mass fraction of 76.5-77.0% and 0.8-1.0% of the carburizer into the furnace, then heat the molten steel to 1628-1643℃, and then insert a 18-20m diameter m aluminum-magnesium alloy bar, the amount of aluminum-magnesium alloy added accounts for 0.20-0.25% of the total mass fraction of the charge; the surface of the aluminum-magnesium alloy bar is coated with a passivation layer, the thickness of the passivation layer is 0.25-0.30mm, the chemical composition and mass fraction of the passivation layer are: 30-33% aluminum oxide, 38-41% iron oxide, 28-30% magnesium oxide; the passivation layer uses water glass as a binder, and the amount of water glass added in the passivation layer accounts for After 6-8 minutes of heat preservation, add 0.8-0.9% of ferrotitanium by mass, and continue to keep warm for 8-10 minutes before all the molten steel is discharged into the ladle; when 1 / 3 to 1 / 2 of the molten steel in the furnace has entered the ladle, add ferroboron with a particle size of 4-8mm and preheated at 650-750℃ for 120-150 minutes into the ladle, and the amount of ferroboron added accounts for 0.50-0.55% of the total mass fraction of the charge; ② After the molten steel in the ladle is deslagging and standing, when the temperature drops to 1531-1544℃, the molten steel is poured into the crystallizer on the continuous casting machine and continuously cast into square billets, which are then directly rolled into cylindrical steel with a diameter of Φ100-110mm on the rolling mill; ③ The cylindrical steel with a diameter of Φ100-110mm obtained in step ② is heated to 1180-1230℃ by a walking natural gas heating furnace, kept warm for 80-100 minutes, and then sheared into a cylinder with a length of 220-275mm required for a single ball by a rod shearing machine, and the cylinder is rough-forged by a CNC hammer, and the deformation amount is controlled at 8-10% each time. After 5-8 deformations, a blank grinding ball is obtained; then the blank grinding ball is fine-forged by an air hammer to obtain a Φ150mm-170mm grinding ball; ④ When the surface temperature of the grinding ball after fine forging in step ③ drops to 835-870°C, it is placed in a water glass quenching liquid pool for quenching, and the water glass concentration in the quenching liquid pool is 8.5%-10%; the temperature of the water glass quenching liquid is 25-38°C, and the mass ratio of the water glass quenching liquid to the grinding ball in the water glass quenching liquid pool is greater than 12:1; after the grinding ball is cooled in the water glass quenching liquid pool for 8-10 minutes, the grinding ball is quickly taken out and rinsed in clean water; and the quenched and rinsed grinding ball is tempered at 180-195°C for 16-18 hours, furnace cooled to a temperature below 150°C, and air cooled to room temperature after being taken out of the furnace, so as to obtain a low-cost, high-performance large-diameter forged grinding ball.

2. The method according to claim 1, characterized in that Step ② The size of the billet is 240mm×240mm.

3. The method according to claim 1, characterized in that The chemical composition and mass fraction of the Q235 scrap steel are: 0.14-0.22% C, 0.30-0.65% Mn, 0.15-0.32% Si, ≤0.050% S, ≤0.045% P, and the remainder is Fe and other inevitable elements.

4. The method according to claim 1, characterized in that The chemical composition and mass fraction of the waste high manganese steel ZG120Mn13 are: 1.05-1.35% C, 0.30-0.90% Si, 11.00-14.00% Mn, ≤0.060% P, ≤0.040% S, and the remainder is Fe and other inevitable elements.

5. The method according to claim 1, characterized in that The chemical composition and mass fraction of the ferrotitanium are: 69.05-71.72% Ti, 1.54-2.19% Al, <0.5% Si, the balance is Fe and inevitable impurities.

6. The method according to claim 1, characterized in that The chemical composition and mass fraction of the ferroboron are: 19.27-20.88% B, ≤0.5% C, ≤2% Si, ≤0.5% Al, ≤0.01% S, ≤0.1% P, and the remainder is Fe and unavoidable impurities.

7. The method according to claim 1, characterized in that The chemical composition and mass fraction of the aluminum-magnesium alloy are: 91.5-92.0% Al, 8.0-8.5% Mg.

8. The method according to claim 1, characterized in that The mass fraction of carbon in the recarburizer is greater than 98.9%.

9. A large diameter forged grinding ball prepared by the method according to any one of claims 1 to 8.

Images