Preparation technology and use method of wear-resistant steel ball for large semi-autogenous mill

Abstract

The invention relates to a preparation technology and a use method of a wear-resistant steel ball for a large semi-autogenous mill, which are characterized in that a scrapped car shell, a scrapped cold roll and waste silicon carbide are used as main furnace charges to smelt molten steel in an electric furnace, and a small amount of aluminum-silicon-calcium alloy, rare earth magnesium-silicon-iron alloy and nano TiC are added to improve the quality of the molten steel. Molten steel is directly poured into a square billet on a square billet continuous casting machine, after the continuous casting square billet is rolled and forged, forging waste heat water cooling short-time quenching and isothermal quenching composite heat treatment is adopted, the wear-resistant steel ball with excellent obdurability and wear resistance is obtained, the phenomena of cracking, stripping and out-of-round do not occur when the wear-resistant steel ball is used on a large semi-autogenous mill, wear is low, and the service life of the wear-resistant steel ball is prolonged. And the production efficiency of the large semi-autogenous mill can be remarkably improved, the ore grinding cost is reduced, and remarkable economic and social benefits are achieved in application and popularization.

Description

Technical Field

[0001] The invention discloses a preparation technology of wear-resistant steel balls and a use method thereof, and particularly relates to a preparation technology of wear-resistant steel balls for large semi-autogenous grinding mills and a use method thereof, belonging to the technical field of grinding ball preparation and use. Background Art

[0002] Large-scale semi-autogenous mill is a kind of equipment that uses the impact and grinding effect of the ore itself for crushing. As an efficient ore crushing equipment, it has gradually become the core equipment in the field of mining processing. Its working principle is to put the ore and a small amount of steel balls into the mill cylinder together, and make the ore and steel balls collide and rub against each other through the rotation of the cylinder, so as to achieve the purpose of crushing the ore. Compared with the traditional ball mill, the large-scale semi-autogenous mill reduces the use of steel balls in the crushing process, reduces wear and energy consumption. Large-scale semi-autogenous mills have been widely used in the beneficiation process of metal and non-metallic ores, especially for processing ores with higher hardness. For example, in the beneficiation process of metal ores such as gold, copper, and iron, large-scale semi-autogenous mills can efficiently crush the ore to the required particle size and improve the beneficiation efficiency. In addition, large-scale semi-autogenous mills also perform well in the processing of non-metallic ores such as graphite and quartz, and can significantly improve the purity and quality of the product. With the continuous advancement of beneficiation technology, large-scale semi-autogenous mills will play a more important role in the field of mining processing. In order to improve the grinding efficiency, the size of steel balls in large semi-autogenous grinding mills has been continuously increased, which puts higher requirements on the strength and toughness of the steel balls.

[0003] In order to improve the toughness of wear-resistant steel balls in large semi-autogenous mills, Chinese invention patent CN116875914A discloses a high-strength and toughness steel ball and a production method thereof. The steel ball contains, by weight percentage, 0.13%-0.15% C, 5.50%-6.70% W, 1.50%-2.50% Mn, 0.25%-0.55% Co, 0.22%-0.45% Mo, and the balance is Fe and inevitable impurities. A production method for high-strength and toughness steel balls comprises the following steps: A, smelting iron ore, reducing the ore to molten iron, and desulfurizing; B, introducing high-pressure oxygen into a converter to heat the molten iron, adding lime for dephosphorization, and removing impurities. The invention performs desulfurization and dephosphorization, and improves the toughness of the steel ball. By adding C, W, Mn, Co and Mo into the molten iron, C increases the rigidity of the steel ball, and the content is low, which prevents the steel ball from being too brittle. Mn can improve the strength of steel, weaken and eliminate the adverse effects of sulfur, and improve the hardenability of steel. W can improve the red hardness and heat strength of steel, and improve the wear resistance of steel. Co further improves the strength of the steel ball. Chinese invention patent CN115354208A also discloses a high-chromium alloy composite wear-resistant steel ball, which is prepared by the following method: ordinary scrap steel, carburizer, ferrochrome, ferromanganese, ferroboron, ferromolybdenum, ferrosilicon, copper plate, metal nickel and metal aluminum are added into a smelting furnace to melt into molten iron, and the chemical composition and mass fraction of the molten iron are controlled as follows: 2.0-3.0% C, 0.4-1.0% Si, 17-21% Cr, 0.5-1.0% Mn, 0.4-0.8% B, 0. 1-0.3% Mo, 0.5-1.0% Cu, 0.05-0.2% Ni, 0.05-0.1% Al, S≤0.05%, P≤0.05%, and the balance is Fe; when the temperature of the molten iron drops to 1530-1560℃, it is taken out of the furnace, and the inoculant is added to the molten iron for inoculation treatment. After standing and slag removal, a casting liquid is obtained; the casting liquid is poured into a mold, cast to form a spherical casting, and after quenching and tempering, the high-chromium alloy composite wear-resistant steel ball is obtained. The invention proposes a high-chromium alloy composite wear-resistant steel ball, which has excellent wear resistance and high toughness by effectively designing the composition of the wear-resistant steel ball, thereby further extending the service life of the wear-resistant steel ball. Chinese invention patent CN105112767A also discloses a high-carbon, high-chromium, high-boron alloy steel ball for a ball mill and a preparation method thereof, wherein the chemical components and mass percentages thereof are: C3.2-4.4, Si0.4-0.8, Cr16.5-18.7, B1.8-2.6, Mn0.3-0.5, Mo0.45-0.65, Nb0.2-0.4, Ni0.1-0.3, Ta0.09-0.16, Al0.04-0.08, Pm0.03-0.05, Gd0.02-0.04, S≤0.03, P≤0.02, and the remainder is Fe.The steel balls produced by this invention have excellent comprehensive performance. On the premise of excellent toughness, they also have high hardness and excellent wear resistance, long service life, and a wide range of applications. They can be used in ball mills in metallurgical mining, cement building materials, thermal power generation and other industries. Chinese invention patent CN104651596A also discloses a heat treatment technology for strong and tough, impact-resistant bearing steel balls. The heat treatment process regulations for bearing steel balls before machining: First, normalizing treatment: when the material is heated to a temperature of 860-880°C in the furnace, keep it warm for 30-40 minutes; then cool the material in oil to a surface temperature of 300-400°C, take out the material and cool it in the air; second, annealing treatment: when the material is heated to a temperature of 730-740°C in the furnace, keep it warm for 4-5 hours, and cool it down with the furnace. The semi-finished product heat treatment after mechanical processing of bearing steel balls, quenching and tempering process regulations: the first is quenching treatment: when the workpiece is heated to a temperature of 870-880°C in the furnace, keep it warm for 25-35 minutes, and then quench the workpiece in a rapid quenching oil at 60-80°C; the second is tempering treatment: when the workpiece is heated to a temperature of 220-240°C in the furnace, keep it warm for 4-5 hours. This invention can make the steel ball obtain the best strength and toughness combination, and effectively improve the life of the steel ball. Although the above-mentioned wear-resistant steel balls have good strength and toughness, they contain more expensive alloy elements such as tungsten, cobalt, molybdenum, and chromium, resulting in excessively high production costs of steel balls and poor market competitiveness.

[0004] In order to reduce the amount of alloy elements added to steel balls and reduce the production cost of steel balls, Chinese invention patent CN114892086A discloses a corrosion-resistant, high-strength, wear-resistant steel ball, which is prepared by the following method: smelting target molten steel, the composition of the target molten steel includes C0.65-0.80%, Si0.40-0.85%, Mn0.65-0.95%, Cr0.40-1.00%, Mo0.04-0.06%, Ti0.02-0.04%, Cu0.04-0.08%, S≤0.020%, P≤0.020%, and the balance is Fe and inevitable impurities; casting to form a cast billet; rolling to form a steel ball billet; cooling and heat treatment to form a steel ball, which is the wear-resistant steel ball. The invention proposes a corrosion-resistant, high-strength, wear-resistant steel ball. By designing the composition of the wear-resistant steel ball and adjusting the production process of the wear-resistant steel ball, the wear-resistant steel ball has excellent wear resistance and high strength and toughness, and the corrosion resistance of the steel ball is further improved. Chinese invention patent CN107164618A also discloses a heat treatment process suitable for low-chromium steel balls, and its process steps are as follows: 1) when the temperature of the molten iron containing 3-5% chromium by mass rises to 1350-1400°C, aluminum is inserted for deoxidation, the slag is removed from the furnace, rare earth ferrosilicon is placed in the ladle to modify the molten iron, the molten iron is allowed to stand for 3-5 minutes after being removed from the furnace, and casting is performed at about 1350°C; 2) the low-chromium steel balls are placed in a vacuum heating furnace and heated to 900-930°C, and kept warm for 20-30 minutes for standby use, wherein the atmosphere in the vacuum heating furnace is composed of nitrogen and nitric oxide; 3) the hot low-chromium steel balls are placed in a water-based quenching liquid for isothermal quenching treatment for 15-20 minutes; the invention is quenched and tempered to obtain a high-hardness and tough martensitic matrix, and at the same time can improve the impact fatigue resistance of the casting, eliminate and significantly reduce internal stress. Chinese invention patent CN104532139A also discloses a high-strength and toughness steel ball and a production method thereof. The high-strength and toughness steel ball contains 0.15%-0.3% C, 1.3-2.0% Si, 1.5%-2.5% Mn, 0.5%-1.0% Cr, 0.2-0.5% Mo, and the balance is Fe and inevitable impurities, in terms of weight percentage. The preparation method comprises the following steps: smelting molten steel; casting to form a continuous casting billet; heating the billet and then rolling: the continuous casting billet is heated to 1150-1300°C and kept warm for 1-4h before rolling to form a steel ball billet; the steel ball billet is heated to 1100-1250°C and kept warm for 10-60s, and then forged into a steel ball with a desired cross-section, with a final forging temperature of 900-1050°C; the forged steel ball is air-cooled to a surface temperature of 750-850°C, and then quenched in water, and when the surface temperature of the steel ball drops to 60-80°C, it is taken out and quickly tempered, and then degreased and finished to obtain a steel ball. The obtained steel ball has high hardness and good toughness.Chinese invention patent CN102418044A also discloses a steel for steel balls and a method for manufacturing the steel balls. The method for manufacturing the steel balls comprises the following steps: smelting molten steel; treating the molten steel with an out-of-furnace refining process, wherein the obtained molten steel is composed of 0.90% to 1.00% C, 0.30% to 1.00% Si, 0.80% to 1.20% Mn, 0.40% to 0.70% Cr, 0.01% to 0.05% Ti, not more than 0.025% P, not more than 0.025% S, not more than 2.0ppm [H], the remainder Fe and inevitable impurities by weight percentage; casting; rolling; cutting to form a steel ball blank; heating the steel ball blank, then forging; quenching, tempering, followed by air cooling and finishing treatment to obtain a steel ball. The steel ball of the invention has high wear resistance, good strength and toughness, does not break or lose roundness during use, and has a long service life. Chinese invention patent CN102443741A also discloses a steel ball for a ball mill and a manufacturing method thereof. The method for manufacturing a ball mill steel ball comprises the following steps: smelting molten steel; treating the molten steel with an out-of-furnace refining process, wherein the molten steel obtained is composed of 0.90% to 1.00% C, 0.30% to 1.00% Si, 0.80% to 1.20% Mn, 0.40% to 0.70% Cr, 0.01% to 0.05% Ti, not more than 0.025% P, not more than 0.025% S, the remainder Fe and inevitable impurities by weight percentage; casting; rolling; cutting to form a steel ball blank; heating the steel ball blank and then forging; quenching, tempering, followed by air cooling and finishing treatment to obtain a steel ball. The above steel balls generally have the disadvantages of low hardness, poor hardenability and poor wear resistance.

[0005] The ball adding method of a large-scale semi-autogenous mill also seriously affects the working efficiency of the semi-autogenous mill. Currently, a variety of ball adding equipment and methods have been disclosed. Chinese invention patent CN102443741A discloses an intelligent ball adding system for a semi-autogenous mill, including an automatic material taking device (2), a screening machine (3), an online detector for ore impact crushing properties (4), intelligent ball adding software for the mill and a host computer (5), a mill (6), an online detection sensor for mill filling rate (8), a sensor data acquisition instrument (9) and a power monitoring device (10). The application of this technical solution can realize the intelligent operation and maintenance of the semi-autogenous mill and achieve the goal of reducing costs, increasing efficiency and increasing production. Chinese invention patent CN108654763A also discloses a method for reasonably adding steel balls to a semi-autogenous mill - a dynamic ball adding method, which is characterized in that under the premise of maintaining the required grinding particle size and the set appropriate grinding concentration, according to the changes in parameters such as the specifications, rotation rate, feed amount, filling rate, operating power, return amount, and grinding fineness of the semi-autogenous mill, the appropriate amount of additional balls and the time of additional balls are dynamically determined, so that the load filling rate of the semi-autogenous mill is kept within an appropriate range, and the feed amount of the semi-autogenous mill is at the required range. This method keeps the working state of the semi-autogenous mill dynamically within the optimal range, thereby achieving the lowest unit steel ball consumption, unit liner steel consumption, and unit grinding power consumption, and can also improve production capacity, reduce product particle size, or improve mineral processing recovery rate. Chinese invention patent CN112169928A discloses a power and shaft pressure control method for a semi-autogenous mill, which relates to the field of semi-autogenous mill equipment. The method processes the power and shaft pressure setting values ​​and feedback values ​​of the semi-autogenous mill through a PID controller and outputs three control signals U1, U2, and U3. The U1 control signal is input to the feeder, the U2 control signal is input to the feed water valve, and the U3 control signal is input to the ball adding machine. The feed amount of the semi-autogenous mill changes after adjustment. The shaft pressure signal of the semi-autogenous mill collected by the shaft pressure sensor is compared with the shaft pressure setting value of the semi-autogenous mill. The power signal of the semi-autogenous mill collected by the power transmitter is compared with the power setting value of the semi-autogenous mill, and finally the deviation is sent to the PID controller. The method judges the state and load of the mill by the three parameters of the power, shaft pressure, and grinding sound of the semi-autogenous mill, and controls the feed amount, feed water, and ball adding amount of the semi-autogenous mill that affect the load of the semi-autogenous mill, so that the power and shaft pressure of the semi-autogenous mill are kept in the optimal grinding area. Chinese invention patent CN105013572A also discloses a large-scale semi-autogenous mill ball adding method with a diameter of 10 meters. The invention achieves the best ball adding effect by controlling the mill power and the amount of returned ore. In addition, the volume of the ball in the mill is checked at any time. If the volume of the ball in the mill is less than 9%, it should be added to 9%. Through the ball adding method of the invention, the particle size qualification rate of the grinding product and the grinding efficiency of the mill are improved, the ball consumption and power consumption are reduced, and the ultimate goal of reducing the cost of mineral processing is achieved.Chinese utility model CN217856512U also discloses an automatic ball adding device for a semi-autogenous mill, which is composed of a ball storage mechanism, a ball adding mechanism and a transmission mechanism; a ball storage bin is arranged on the upper part of the ball storage mechanism, an inner inclined plate is arranged on the lower part of the ball storage bin, a lower ball inclined surface is arranged on the bottom of the ball storage bin, and a baffle is arranged at the tail of the lower ball inclined surface; the ball adding mechanism is arranged behind the baffle, and is composed of a roller bracket, a ball adding roller and a ball claw, the ball adding roller is arranged on the roller bracket, and the ball adding roller is provided with a ball claw; the transmission mechanism is composed of a motor, a motor bracket, a reducer and a coupling, the motor and the reducer are arranged on the motor bracket, the motor is connected to the reducer, and the reducer is connected to the ball adding roller through a coupling. Through the structure of the ball storage mechanism and the ball adding mechanism, the phenomenon of ball jamming, ball blocking and ball failure is solved, and the grinding ball consumption is reduced, thereby improving the grinding efficiency of the semi-autogenous mill. Summary of the invention

[0006] The high-strength, toughness and wear-resistant steel balls used in large semi-autogenous grinding mills may contain more expensive alloy elements such as tungsten, cobalt, molybdenum, etc., which leads to high production costs of the steel balls and poor market competitiveness; or there are problems such as low hardness, poor hardenability and poor wear resistance. The present invention optimizes the steel ball composition and improves the steel ball processing technology to make the steel balls have high strength, toughness and excellent wear resistance. On this basis, the ball adding method is improved during use to further improve the grinding efficiency of large semi-autogenous grinding mills.

[0007] A method for preparing wear-resistant steel balls for large semi-autogenous grinding mills, characterized in that the wear-resistant steel balls are made of continuous casting billets smelted mainly from scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide, and the specific process steps include the following:

[0008] ① First, the scrapped car shell is roughly shredded by a scrap car shredder, and then the roughly shredded scrapped car shell is packaged into steel blocks with a size of 180-260mm×180-260mm×180-260mm by a scrap steel baler; the scrapped cold rolling roller 9Cr2Mo is also crushed into cold rolling roller 9Cr2Mo blocks with a size of 10-220mm×10-220mm×10-220mm by a drop hammer crushing device;

[0009] ② The steel blocks and 9Cr2Mo cold-rolled roller fragments, waste silicon carbide and aluminum silicon calcium alloy in step ① are used as furnace charges, and molten steel is smelted in an electric furnace; the mass compositions of the steel blocks, 9Cr2Mo cold-rolled roller fragments, waste silicon carbide and aluminum silicon calcium alloy in the furnace charges are: 86.0-86.6%, 10.0-10.8%, 2.5-2.7%, 0.6-0.7%, respectively, and the sum of the mass fractions of the four furnace charges is 100%; firstly, the steel blocks with a mass fraction of 86.0-86.6% and the cold-rolled roller 9Cr2Mo fragments with a mass fraction of 10.0-10.8% are mixed, heated and melted in an electric furnace; after the steel blocks and the cold-rolled roller 9Cr2Mo fragments are completely melted, waste silicon carbide with a mass fraction of 2.5-2.7% is added; after the waste silicon carbide is completely melted, the temperature is raised to 1633-1648°C, Aluminum-silicon-calcium alloy with a mass fraction of 0.6-0.7% is added, and after heat preservation for 8-10 minutes, the molten steel in the furnace is taken out of the furnace into a ladle, and rare earth magnesium-silicon-iron alloy and nano-TiC with a particle size of 5-10 mm are pre-added to the bottom of the ladle; the nano-TiC is placed on the rare earth magnesium-silicon-iron alloy, and the amount of rare earth magnesium-silicon-iron alloy and nano-TiC added accounts for 0.50-0.65% and 0.12-0.13% of the mass fraction of the molten steel entering the ladle respectively; after the molten steel is slag-scraped and left to stand, when the temperature drops to 1516-1528° C., the molten steel is directly cast into a square billet with a cross-section of 180 mm×180 mm on a billet continuous casting machine, and the billet is continuously pulled out at an outlet of the crystallizer at a pulling speed of 0.70-0.85 m / min; then the square billet is directly rolled into a round steel bar with a diameter of Φ90-110 mm on a rolling mill;

[0010] ③ The round steel rod with a diameter of Φ90-110 mm obtained in step ② is cut into 6-8 m in length; the round steel rod with a length of 6-8 m is then placed in a heating furnace for heating, and after the round steel rod is uniformly heated to 1250-1280° C. and kept warm for 80-100 minutes, the round steel rod is conveyed to a continuous cutting machine through a steel rod conveying device with a heat preservation device for cutting to obtain steel segments with a length of 225-275 mm; the steel segments are then forged into steel balls with a diameter of Φ140-170 mm in various diameters, The final forging temperature is controlled at 980-1050°C; when the forged steel ball is air-cooled to a surface temperature of 835-870°C, it is placed in a water pool at a temperature of 25-38°C for cooling for 60-80 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1; then the water-cooled steel ball is directly isothermally quenched in a nitrate melt at a temperature of 265-300°C for an isothermal time of 2.0-2.5 hours; in the isothermal quenching pool, the mass ratio of nitrate melt to steel ball is greater than 8:1; then air-cooling is performed to obtain the wear-resistant steel ball;

[0011] As mentioned above, the chemical composition and mass fraction of the scrapped cold rolling roller 9Cr2Mo are: 0.85-0.95% C, 1.70-2.10% Cr, 0.20-0.35% Mn, 0.20-0.40% Mo, 0.25-0.45% Si, ≤0.25% Ni, ≤0.025% P, ≤0.025% S, and the remainder is Fe and unavoidable impurities.

[0012] As mentioned above, the chemical composition and mass fraction of the aluminum-silicon-calcium alloy are: 8.64-8.97% Ca, 28.37-29.81% Si, and the remainder is Al and unavoidable impurities.

[0013] As mentioned above, the chemical composition and mass fraction of rare earth magnesium ferrosilicon alloy are: 6-8% RE, 7-9% Mg, 35-44% Si, ≤1% Ti, ≤1% Al, and the remainder is Fe and unavoidable impurities.

[0014] As mentioned above, nitrate is composed of 50-55% by mass of KNO 3 and 45-50% NaNO 3 composition.

[0015] The method for using the wear-resistant steel balls obtained by the present invention is characterized in that the wear-resistant steel balls with diameters of Φ140-170 mm and multiple different diameters are added into a large semi-autogenous mill with a diameter greater than 10 meters for crushing ore, and the ball adding method is as follows: the volume of the added wear-resistant steel balls occupies 30%-35% of the volume of the semi-autogenous mill; the diameters of the wear-resistant steel balls with diameters of Φ140-170 mm and multiple different diameters are respectively: Φ140 mm, Φ150 mm, Φ160 mm and Φ170 mm, and the added amounts of the wear-resistant steel balls with diameters of Φ140 mm, Φ150 mm, Φ160 mm and Φ170 mm respectively account for 12-15%, 15-18%, 25-28% and 40-45% of the total mass fraction of the wear-resistant steel balls added into the semi-autogenous mill.

[0016] The present invention discloses a wear-resistant steel ball preparation technology for a large semi-autogenous mill and a method for adding and using the same, characterized in that the wear-resistant steel ball is processed by a continuous casting billet smelted mainly from scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide. my country is a major automobile producer and consumer. In 2024 alone, my country's automobile production and sales will exceed 30 million vehicles, and the annual scrapped automobiles will exceed 10 million vehicles. In the past, scrapped automobile shells mainly entered the steelmaking workshop of a steel plant, entered an electric furnace or a converter, and were used to produce molten steel. However, in order to improve the corrosion resistance of the automobile shell, its surface is often plated with a zinc layer with a thickness of tens of microns by hot plating or electroplating. During the high-temperature smelting process, zinc reacts with other elements in the steel, resulting in a decrease in the mechanical properties of the steel, such as reduced strength and toughness. The presence of zinc in the automobile shell causes the automobile shell to be added to the steel as a furnace charge, which will seriously affect the quality of the final steel product. This is unacceptable for industries that require high-strength steel, such as automobile manufacturing and construction. Therefore, in order to ensure the quality of steel products, it has become an important quality standard that scrap steel scraps cannot contain zinc. This results in the inability of scrapped car shells to be used in the production of high-performance steel products, limiting the application of scrapped car shells. In addition, my country is a major steel producer, with an annual crude steel output of more than 1 billion tons, ranking first in the world, and accounting for more than 50% of the world's total steel production. Rollers are important consumable materials in steel production. my country consumes nearly one million tons of rolls per year, and more than 100,000 tons of cold-rolled rolls are scrapped each year. Most of the scrapped cold-rolled rolls are used to produce ordinary steel castings, resulting in a huge waste of resources. The present invention uses scrapped car shells and scrapped cold-rolled rolls in combination, which can utilize the iron and a small amount of alloy elements in the scrapped car shells. The zinc content in the scrapped car shells is moderate in steel, which can significantly improve the hardness of the steel and improve the wear resistance. The alloy elements such as chromium and molybdenum in the scrapped cold-rolled rolls can also be used to improve the hardenability and hardenability of the material, and overcome the adverse effect of the presence of zinc in the scrapped car shell on the performance reduction of the steel.

[0017] In addition, the furnace charge of the present invention also contains waste silicon carbide and aluminum silicon calcium alloy; silicon carbide is a man-made material, the molecular formula of silicon carbide is SiC, the molecular weight is 40.07, and the mass percentage composition is 70.045% of silicon and 29.955% of carbon. The waste silicon carbide is added in the present invention mainly to supplement the silicon and carbon content in the steel ball. The raw materials of the present invention are mainly scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide, without any iron alloy, which ensures that the steel ball of the present invention has a low production cost. However, the molten steel made entirely of waste metallurgy contains more gas and inclusions, and the quality of the cast product is poor. For this reason, the present invention also adds aluminum silicon calcium alloy accounting for 0.6-0.7% of the total mass fraction of the furnace charge, and the chemical composition and mass fraction of the aluminum silicon calcium alloy are: 8.64-8.97% Ca, 28.37-29.81% Si, and the balance is Al and inevitable impurities, which has a good deoxidation and inclusion removal effect. In addition, as a new type of metallurgical material, aluminum silicon calcium alloy can remove impurities, improve the morphology of inclusions, save metallurgical materials and reduce power consumption. It can also replace aluminum wire and silicon calcium and other materials, has a good deoxidation and purification effect on molten steel, can improve the fluidity of molten steel, and prevent nozzle nodules.

[0018] The specific process steps of the present invention are as follows: firstly, the scrapped car shell is roughly shredded by a scrapped car shredder, and then the roughly shredded scrapped car shell is packaged into steel blocks with a size of 180-260mm×180-260mm×180-260mm by a scrap steel baler; and the scrapped cold rolling roller 9Cr2Mo is crushed into cold rolling roller 9Cr2Mo fragments with a size of 10-220mm×10-220mm×10-220mm by a drop hammer crushing device. The chemical composition and mass fraction of the scrapped cold rolling roller 9Cr2Mo are: 0.85-0.95% C, 1.70-2.10% Cr, 0.20-0.35% Mn, 0.20-0.40% Mo, 0.25-0.45% Si, ≤0.25% Ni, ≤0.025% P, ≤0.025% S, and the balance is Fe and unavoidable impurities. The steel block, the cold-rolled roller 9Cr2Mo fragments, the waste silicon carbide and the aluminum silicon calcium alloy are used as the furnace charge, and the molten steel is smelted in an electric furnace; the mass compositions of the steel block, the cold-rolled roller 9Cr2Mo fragments, the waste silicon carbide and the aluminum silicon calcium alloy in the furnace charge are: 86.0-86.6%, 10.0-10.8%, 2.5-2.7%, 0.6-0.7%, and the sum of the mass fractions of the four furnace charges is 100%. In order to improve the efficiency of molten steel smelting, the steel block with a mass fraction of 86.0-86.6% and the cold-rolled roller 9Cr2Mo fragments with a mass fraction of 10.0-10.8% are first mixed and heated and melted in an electric furnace. The melting point of silicon carbide is as high as 2700°C, and it is difficult to melt directly in the electric furnace, and it is easy to be oxidized and burned.

[0019] After the steel block and the cold rolling roller 9Cr2Mo fragments are completely melted, the waste silicon carbide with a mass fraction of 2.5-2.7% is added, and the waste silicon carbide is completely immersed in the molten steel in the furnace, which can accelerate the dissolution and melting of the waste silicon carbide and improve the smelting efficiency. After the waste silicon carbide is completely melted, the temperature is raised to 1633-1648°C, and the aluminum silicon calcium alloy with a mass fraction of 0.6-0.7% is added. After keeping the temperature for 8-10 minutes, the molten steel in the furnace is taken out of the furnace into the ladle. The addition of the aluminum silicon calcium alloy can have a good deoxidation and slag removal effect on the molten steel. Rare earth magnesium silicon iron alloy and nano TiC with a particle size of 5-10mm are pre-added to the bottom of the ladle; the nano TiC is placed on the rare earth magnesium silicon iron alloy, and the amount of rare earth magnesium silicon iron alloy and nano TiC added accounts for 0.50-0.65% and 0.12-0.13% of the mass fraction of the molten steel entering the ladle, respectively. Adding 0.12-0.13% of nano-TiC is mainly used to promote the solidification of molten steel, refine the solidification structure, and especially refine the residual ZnO in the molten steel, which can significantly improve the mechanical properties of the subsequently cast steel billet. However, the density of nano-TiC is small and it is easy to agglomerate. In order to achieve uniform distribution of nano-TiC in molten steel, the present invention places nano-TiC on the rare earth magnesium ferrosilicon alloy, and the magnesium element in the rare earth magnesium ferrosilicon alloy has a low boiling point and is rapidly gasified under high-temperature molten steel operation, which promotes the violent tumbling of the molten steel in the ladle, and is conducive to the uniform distribution of nano-TiC in the molten steel. In addition, the magnesium and rare earth elements in the rare earth magnesium ferrosilicon alloy have excellent desulfurization and deoxidation effects, which promote the further refinement and purification of the cast steel solidification structure and improve the mechanical properties of the subsequently cast steel billet.

[0020] After the molten steel of the present invention is slag-stripped and left to stand, when the temperature drops to 1516-1528°C, the molten steel is directly cast into a square billet with a cross-section of 180mm×180mm on a square billet continuous casting machine, and the billet is continuously pulled out at a pulling speed of 0.70-0.85 m / min at the outlet of the crystallizer. Subsequently, the square billet is directly rolled into a round steel bar with a diameter of Φ90-110mm on a rolling mill, realizing the integration of casting and rolling, and having the advantages of energy saving and efficient production. The present invention cuts the length of the round steel bar with a diameter of Φ90-110mm into 6-8m, and then places the round steel bar with a length of 6-8m in a heating furnace for heating. After the round steel bar is uniformly heated to 1250-1280°C and kept warm for 80-100 minutes, it is completely austenitized, has excellent high-temperature plasticity, and can be used for subsequent forging processing. The present invention transports the round steel rod to a continuous cutting machine through a steel rod conveying device with a heat preservation device to obtain steel segments with a length of 225 to 275 mm; then the steel segments are forged into different steel balls with a diameter of Φ140 to 170 mm, and the final forging temperature is controlled at 980 to 1050° C. The final forging temperature cannot be too low, otherwise a pearlite structure with low hardness is likely to appear in the center of the steel ball, which will reduce the wear resistance of the steel ball.

[0021] After the forged steel ball of the present invention is air-cooled to a surface temperature of 835-870°C, it is placed in a water pool at a temperature of 25-38°C and cooled for 60-80 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1. Rapid cooling of the surface of the steel ball can take away the heat inside the steel ball, which is beneficial to obtaining lower bainite with excellent performance during subsequent isothermal quenching. The present invention directly performs isothermal quenching on the water-cooled steel ball in a nitrate melt at a temperature of 265-300°C, wherein the nitrate is composed of 50-55% by mass of KNO 3 and 45-50% NaNO 3 The composition of the present invention is as follows: the isothermal time is 2.0 to 2.5 hours; in the isothermal quenching pool, the mass ratio of the nitrate melt to the steel ball is greater than 8:1; and then the wear-resistant steel ball can be obtained by air cooling. The steel ball of the present invention contains more silicon and carbon elements, the austenitizing temperature is too low, the carbon and alloy elements dissolved in the high-temperature austenite are less, the high-temperature austenite has poor stability, pearlite and ferrite structures are prone to appear in the isothermal quenching structure, and the strength, toughness and wear resistance of the steel ball are reduced. The austenitizing temperature is too high, the carbon and alloy elements dissolved in the high-temperature austenite are too much, the high-temperature austenite has high stability, a large amount of austenite is prone to appear in the isothermal quenching structure, and the austenitizing temperature is too high, which also makes the structure of the steel ball significantly coarsened, reducing the strength, toughness and wear resistance of the steel ball. Therefore, when the steel ball of the present invention is air-cooled to a surface temperature of 835-870°C (austenitizing temperature), it is placed in a water pool at a temperature of 25-38°C and cooled for 60-80 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1; and then the water-cooled steel ball is directly austempered in a nitrate melt at a temperature of 265-300°C. In addition, the austempering temperature has a significant effect on the organization and performance of the steel ball. The microstructures obtained under different austempering treatment conditions are all typical carbide-free austenitic-bainitic structures. When the austempering temperature is low, the bainitic ferrite laths are relatively small and the orientation is very messy. With the increase of the austempering temperature, the bainitic ferrite laths are widened and the carbon-rich residual austenite film therebetween is thickened. This is because when the austempering temperature is high, the incubation period of the bainitic ferrite transformation is shortened, the diffusion capacity of carbon atoms is enhanced, the growth rate of the bainitic ferrite is accelerated, and the amount of carbon-rich stable austenite is also increased. At the same time, the orientation of the bainitic ferrite laths gradually becomes consistent, and bainitic ferrite lath bundles with different orientations and a certain intersection angle with each other are generated inside an original austenite grain. When the transformation temperature is higher than 350°C, the structure changes significantly, the bainitic ferrite becomes coarse and branched, and the austenite film thickens. The isothermal quenching temperature of the present invention is controlled at 265-300°C, and the isothermal time is 2.0-2.5 hours. In the isothermal quenching pool, the mass ratio of the nitrate melt to the steel ball is greater than 8:1, and then air cooling can obtain wear-resistant steel balls with high strength, toughness, hardness and excellent wear resistance.

[0022] The wear-resistant steel balls of the present invention are added to a large semi-autogenous mill with a diameter greater than 10 meters for crushing ore. The method of adding the balls is as follows: the amount of wear-resistant steel balls added accounts for 30% to 35% of the volume of the semi-autogenous mill. During the operation of the semi-autogenous mill, it is very important to determine the appropriate addition ratio of the steel balls. The invention makes the amount of wear-resistant steel balls added account for 30% to 35% of the volume of the semi-autogenous mill. The ratio of 30% to 35% is based on ensuring that the steel balls can effectively cover the bottom of the mill, achieve efficient grinding effects, and prevent equipment wear or efficiency reduction caused by too many steel balls. The amount of wear-resistant steel balls added with diameters of Φ140mm, Φ150mm, Φ160mm and Φ170mm of the present invention respectively accounts for 12 to 15%, 15 to 18%, 25 to 28% and 40 to 45% of the total added mass fraction of wear-resistant steel balls entering the semi-autogenous mill. The invention ensures high grinding efficiency and prolongs the life of the equipment by reasonably determining and adjusting the addition ratio of steel balls in the semi-autogenous mill.

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

[0024] (1) The wear-resistant steel ball of the present invention is made of continuous casting steel billets smelted with scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide as main furnace materials, without adding alloy raw materials such as ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, ferrovanadium, nickel, copper, etc., with low production cost and efficient utilization of waste materials.

[0025] (2) After forging, the wear-resistant steel ball of the present invention adopts a composite process of short-time quenching by waste water cooling + isothermal quenching to prepare a steel ball with a diameter of 140mm-170mm, which has excellent hardenability, surface hardness ≥61HRC, core hardness ≥58HRC, and impact toughness ≥45J / cm 2 , tensile strength ≥1400MPa, single ball drop times >8000 times, steel ball microstructure is fine and evenly distributed, with excellent impact crushing resistance and high impact fatigue life.

[0026] (3) The wear-resistant steel ball of the present invention realizes continuous casting and rolling, has high production efficiency, and has a high steel ball forging qualified rate of more than 99.5%, which makes it easy to achieve efficient production.

[0027] (4) The wear-resistant steel ball of the present invention has a complex phase structure of lower bainite + 8-12% of retained austenite by volume, and has an excellent work hardening effect. When used on a large semi-autogenous grinding mill with a diameter of more than 10 meters, the surface hardness of the steel ball is increased by 3-5HRC to more than 64HRC, without cracking, peeling or loss of roundness. It can meet the use requirements of mines, improve the grinding efficiency of semi-autogenous grinding mills, and significantly improve the competitiveness, market share and economic benefits of large-diameter forged grinding ball products. DETAILED DESCRIPTION

[0028] The present invention is further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0029] Embodiment 1:

[0030] A wear-resistant steel ball preparation technology and ball adding method for large semi-autogenous grinding mill, characterized in that the wear-resistant steel ball is made of continuous casting billet smelted mainly from scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide, and the specific process steps are as follows:

[0031] ① First, the scrapped car shell is roughly shredded by a scrapped car shredder, and then the roughly shredded scrapped car shell is packaged into steel blocks with a size of 180-260 mm×180-260 mm×180-260 mm by a scrap steel baler; and the scrapped cold rolling roller 9Cr2Mo (the chemical composition and mass fraction of the scrapped cold rolling roller 9Cr2Mo are: 0.85% C, 2.10% Cr, 0.20% Mn, 0.40% Mo, 0.25% Si, 0.08% Ni, 0.022% P, 0.009% S, and the remainder is Fe and unavoidable impurities) is crushed into cold rolling roller 9Cr2Mo fragments with a size of 10-220 mm×10-220 mm×10-220 mm by a drop hammer crushing device;

[0032] ② Use the steel block and cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy (the chemical composition and mass fraction of the aluminum silicon calcium alloy are: 8.64% Ca, 29.81% Si, the balance is Al and inevitable impurities) as the charge, using an electric furnace to smelt molten steel; the mass compositions of steel blocks, cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy in the charge are: 86%, 10.8%, 2.5%, 0.7%, and the sum of the mass fractions of the four charges is 100%; firstly, the steel blocks with a mass fraction of 86% and the cold rolling roller 9Cr2Mo fragments with a mass fraction of 10.8% are mixed and heated to melt in an electric furnace; after the steel blocks and the cold rolling roller 9Cr2Mo fragments are completely melted, waste silicon carbide with a mass fraction of 2.5% is added; after the waste silicon carbide is completely melted, the temperature is raised to 1633℃, and aluminum silicon calcium alloy with a mass fraction of 0.7% is added. After keeping warm for 10 minutes, the molten steel in the furnace is taken out of the furnace into a ladle, and a particle size of 5 to 1 0mm rare earth magnesium ferrosilicon alloy (the chemical composition and mass fraction of the rare earth magnesium ferrosilicon alloy are: 6.27% RE, 8.72% Mg, 35.88% Si, 0.33% Ti, 0.65% Al, the balance is Fe and inevitable impurities) and nano-TiC; the nano-TiC is placed on the rare earth magnesium ferrosilicon alloy, and the rare earth magnesium ferrosilicon alloy and the nano-TiC added account for 0.50% and 0.12% of the mass fraction of the molten steel entering the ladle respectively; after the molten steel is slag-stripped and allowed to stand, when the temperature drops to 1516°C, the molten steel is directly cast into a square billet with a cross-section of 180mm×180mm on a billet continuous casting machine, and the billet is continuously pulled out at a pulling speed of 0.70 m / min at the outlet of the crystallizer; then the square billet is directly rolled into a round steel bar with a diameter of Φ90mm on a rolling mill;

[0033] ③ The round steel bar with a diameter of Φ90mm obtained in step ② is cut into 6m in length; then the round steel bar with a length of 6m is placed in a heating furnace for heating, and after the round steel bar is uniformly heated to 1250°C and kept warm for 100 minutes, the round steel bar is transported to a continuous cutting machine through a steel bar conveying device with a heat preservation device for cutting to obtain a steel segment with a length of 225.9mm; then the steel segment is forged into a steel ball with a diameter of Φ140mm, and the final forging temperature is controlled at 980-1020°C; when the forged steel ball is air-cooled to a surface temperature of 835-856°C, it is placed in a water pool at a temperature of 25°C for cooling for 60 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1; then the water-cooled steel ball is directly heated in a nitrate solution (the nitrate is composed of 50% by mass of KNO 3 and 50% NaNO 3 The isothermal quenching is carried out in the molten metal of the composition, and the isothermal time is 2.0 hours; in the isothermal quenching pool, the mass ratio of the nitrate melt to the steel ball is greater than 8:1; and then the wear-resistant steel ball can be obtained by air cooling. The mechanical properties of the steel ball are shown in Table 1;

[0034] ④ The wear-resistant steel balls obtained in step ③ are added into a large semi-autogenous mill with a diameter of 10.8 meters for crushing gold ore. The ball adding method is as follows: the amount of wear-resistant steel balls added accounts for 30% of the volume of the semi-autogenous mill; the amount of wear-resistant steel balls with diameters of Φ140mm, Φ150mm, Φ160mm and Φ170mm respectively accounts for 12%, 18%, 25% and 45% of the total mass fraction of wear-resistant steel balls added into the semi-autogenous mill.

[0035] Embodiment 2:

[0036] A wear-resistant steel ball preparation technology and ball adding method for large semi-autogenous grinding mill, characterized in that the wear-resistant steel ball is made of continuous casting billet smelted mainly from scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide, and the specific process steps are as follows:

[0037] ① First, the scrapped car shell is roughly shredded by a scrapped car shredder, and then the roughly shredded scrapped car shell is packaged into steel blocks with a size of 180-260 mm×180-260 mm×180-260 mm by a scrap steel baler; and the scrapped cold rolling roller 9Cr2Mo (the chemical composition and mass fraction of the scrapped cold rolling roller 9Cr2Mo are: 0.95% C, 1.70% Cr, 0.35% Mn, 0.20% Mo, 0.45% Si, 0.09% Ni, 0.020% P, 0.022% S, and the remainder is Fe and unavoidable impurities) is crushed into cold rolling roller 9Cr2Mo fragments with a size of 10-220 mm×10-220 mm×10-220 mm by a drop hammer crushing device;

[0038] ② Use the steel block and cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy (the chemical composition and mass fraction of the aluminum silicon calcium alloy are: 8.97% Ca, 28.37% Si, the balance is Al and inevitable impurities) as the charge, using an electric furnace to smelt molten steel; the mass compositions of steel blocks, cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy in the charge are: 86.6%, 10.1%, 2.7%, 0.6%, respectively, and the sum of the mass fractions of the four charges is 100%; firstly, the steel blocks with a mass fraction of 86.6% and the cold rolling roller 9Cr2Mo fragments with a mass fraction of 10.1% are mixed and heated to melt in an electric furnace; after the steel blocks and the cold rolling roller 9Cr2Mo fragments are completely melted, waste silicon carbide with a mass fraction of 2.7% is added; after the waste silicon carbide is completely melted, the temperature is raised to 1648℃, and aluminum silicon calcium alloy with a mass fraction of 0.6% is added. After keeping warm for 8 minutes, the molten steel in the furnace is taken out of the furnace into a ladle, and the bottom of the ladle is pre-added with particles of 5 to 600 g / cm2. 10mm rare earth magnesium ferrosilicon alloy (the chemical composition and mass fraction of the rare earth magnesium ferrosilicon alloy are: 7.70% RE, 7.05% Mg, 43.68% Si, 0.61% Ti, 0.48% Al, the balance is Fe and inevitable impurities) and nano-TiC; the nano-TiC is placed on the rare earth magnesium ferrosilicon alloy, and the rare earth magnesium ferrosilicon alloy and the nano-TiC added account for 0.65% and 0.13% of the mass fraction of the molten steel entering the ladle respectively; after the molten steel is slag-stripped and allowed to stand, when the temperature drops to 1528°C, the molten steel is directly cast on a billet continuous casting machine into a billet with a cross-section of 180mm×180mm, and the billet is continuously pulled out at a pulling speed of 0.85 m / min at the outlet of the crystallizer; then the billet is directly rolled on a rolling mill into a round steel bar with a diameter of Φ110mm;

[0039] ③ The length of the round steel bar with a diameter of Φ110mm obtained in step ② is cut into 8m; then the round steel bar with a length of 8m is placed in a heating furnace for heating, and after the round steel bar is evenly heated to 1280°C and kept warm for 80 minutes, the round steel bar is transported to a continuous cutting machine through a steel bar conveying device with a heat preservation device for cutting to obtain a steel segment with a length of 270.7mm; then the steel segment is forged into a steel ball with a diameter of Φ170mm, and the final forging temperature is controlled at 1006-1050°C; when the forged steel ball is air-cooled to a surface temperature of 852-870°C, it is placed in a water pool at a temperature of 38°C for cooling for 80 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1; then the water-cooled steel ball is directly heated in a nitrate (the nitrate is composed of 55% by mass of KNO) at a temperature of 265°C 3 and 45% NaNO 3 The isothermal quenching is carried out in the molten metal (composition) for 2.5 hours; in the isothermal quenching pool, the mass ratio of the nitrate molten metal to the steel ball is greater than 8:1; and then the wear-resistant steel ball is obtained by air cooling. The mechanical properties of the steel ball are shown in Table 1;

[0040] ④ The wear-resistant steel balls obtained in step ③ are added into a large semi-autogenous mill with a diameter of 11.3 meters for crushing iron ore. The method of adding the balls is as follows: the amount of wear-resistant steel balls added accounts for 35% of the volume of the semi-autogenous mill; the amount of wear-resistant steel balls with diameters of Φ140mm, Φ150mm, Φ160mm and Φ170mm respectively accounts for 15%, 15%, 28% and 42% of the total mass fraction of wear-resistant steel balls added into the semi-autogenous mill.

[0041] Embodiment 3:

[0042] A wear-resistant steel ball preparation technology and ball adding method for large semi-autogenous grinding mill, characterized in that the wear-resistant steel ball is made of continuous casting billet smelted mainly from scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide, and the specific process steps are as follows:

[0043] ① First, the scrapped car shell is roughly shredded by a scrapped car shredder, and then the roughly shredded scrapped car shell is packaged into steel blocks with a size of 180-260 mm×180-260 mm×180-260 mm by a scrap steel baler; and the scrapped cold rolling roller 9Cr2Mo (the chemical composition and mass fraction of the scrapped cold rolling roller 9Cr2Mo are: 0.87% C, 1.91% Cr, 0.28% Mn, 0.25% Mo, 0.33% Si, 0.16% Ni, 0.017% P, 0.013% S, and the remainder is Fe and unavoidable impurities) is crushed into cold rolling roller 9Cr2Mo fragments with a size of 10-220 mm×10-220 mm×10-220 mm by a drop hammer crushing device;

[0044] ② Use the steel block and cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy (the chemical composition and mass fraction of the aluminum silicon calcium alloy are: 8.80% Ca, 28.73% Si, the balance is Al and inevitable impurities) as the charge, using an electric furnace to smelt molten steel; the mass compositions of steel blocks, cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy in the charge are: 86.4%, 10.3%, 2.6%, 0.7%, respectively, and the sum of the mass fractions of the four charges is 100%; firstly, the steel blocks with a mass fraction of 86.4% and the cold rolling roller 9Cr2Mo fragments with a mass fraction of 10.3% are mixed and heated to melt in an electric furnace; after the steel blocks and the cold rolling roller 9Cr2Mo fragments are completely melted, waste silicon carbide with a mass fraction of 2.6% is added; after the waste silicon carbide is completely melted, the temperature is raised to 1637℃, and aluminum silicon calcium alloy with a mass fraction of 0.7% is added. After keeping warm for 9 minutes, the molten steel in the furnace is taken out of the furnace into a ladle, and a particle size of 5 ~10mm rare earth magnesium ferrosilicon alloy (the chemical composition and mass fraction of the rare earth magnesium ferrosilicon alloy are: 6.92% RE, 7.85% Mg, 38.61% Si, 0.36% Ti, 0.44% Al, the balance is Fe and inevitable impurities) and nano-TiC; the nano-TiC is placed on the rare earth magnesium ferrosilicon alloy, and the amount of rare earth magnesium ferrosilicon alloy and nano-TiC added accounts for 0.55% and 0.12% of the mass fraction of the molten steel entering the ladle respectively; after the molten steel is slag-stripped and allowed to stand, when the temperature drops to 1523°C, the molten steel is directly cast into a square billet with a cross-section of 180mm×180mm on a billet continuous casting machine, and the billet is continuously pulled out at an outlet of the crystallizer at a pulling speed of 0.75 m / min; then the billet is directly rolled into a round steel bar with a diameter of Φ95mm on a rolling mill;

[0045] ③ The length of the round steel bar with a diameter of Φ95mm obtained in step ② is cut into 7m; then the round steel bar with a length of 7m is placed in a heating furnace for heating, and after the round steel bar is evenly heated to 1260°C and kept warm for 90 minutes, the round steel bar is transported to a continuous cutting machine through a steel bar conveying device with a heat preservation device for cutting to obtain a steel segment with a length of 249.3mm; then the steel segment is forged into a steel ball with a diameter of Φ150mm, and the final forging temperature is controlled at 990-1040°C; when the forged steel ball is air-cooled to a surface temperature of 845-868°C, it is placed in a water pool at a temperature of 29°C for cooling for 70 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1; then the water-cooled steel ball is directly heated in a nitrate (the nitrate is composed of 52% by mass of KNO) at a temperature of 275°C 3 and 48% NaNO 3 The isothermal quenching is carried out in the molten metal (composition) for 2.2 hours; in the isothermal quenching pool, the mass ratio of the nitrate molten metal to the steel ball is greater than 8:1; and then the wear-resistant steel ball is obtained by air cooling. The mechanical properties of the steel ball are shown in Table 1;

[0046] ④ The wear-resistant steel balls obtained in step ③ are added into a large semi-autogenous mill with a diameter of 10.5 meters for crushing copper ore. The adding method is as follows: the amount of wear-resistant steel balls added accounts for 32% of the volume of the semi-autogenous mill; the amount of wear-resistant steel balls with diameters of Φ140mm, Φ150mm, Φ160mm and Φ170mm respectively accounts for 13%, 17%, 27% and 43% of the total mass fraction of wear-resistant steel balls added into the semi-autogenous mill.

[0047] Embodiment 4:

[0048] A wear-resistant steel ball preparation technology and ball adding method for large semi-autogenous grinding mill, characterized in that the wear-resistant steel ball is made of continuous casting billet smelted mainly from scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide, and the specific process steps are as follows:

[0049] ① First, the scrapped car shell is roughly shredded by a scrapped car shredder, and then the roughly shredded scrapped car shell is packaged into steel blocks with a size of 180-260 mm×180-260 mm×180-260 mm by a scrap steel baler; and the scrapped cold rolling roller 9Cr2Mo (the chemical composition and mass fraction of the scrapped cold rolling roller 9Cr2Mo are: 0.91% C, 1.97% Cr, 0.32% Mn, 0.35% Mo, 0.42% Si, 0.05% Ni, 0.024% P, 0.010% S, and the remainder is Fe and unavoidable impurities) is crushed into cold rolling roller 9Cr2Mo fragments with a size of 10-220 mm×10-220 mm×10-220 mm by a drop hammer crushing device;

[0050] ② Use the steel block and cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy (the chemical composition and mass fraction of the aluminum silicon calcium alloy are: 8.82% Ca, 29.27% Si, the balance is Al and inevitable impurities) as the charge, using an electric furnace to smelt molten steel; the mass compositions of steel blocks, cold rolling roller 9Cr2Mo fragments, waste silicon carbide and aluminum silicon calcium alloy in the charge are: 86.4%, 10.4%, 2.6%, 0.6%, and the sum of the mass fractions of the four charges is 100%; firstly, the steel blocks with a mass fraction of 86.4% and the cold rolling roller 9Cr2Mo fragments with a mass fraction of 10.4% are mixed and heated to melt in an electric furnace; after the steel blocks and the cold rolling roller 9Cr2Mo fragments are completely melted, waste silicon carbide with a mass fraction of 2.6% is added; after the waste silicon carbide is completely melted, the temperature is raised to 1645℃, and aluminum silicon calcium alloy with a mass fraction of 0.6% is added. After keeping warm for 9 minutes, the molten steel in the furnace is taken out of the furnace into a ladle, and the bottom of the ladle is pre-added with particles of 5 to 600 g / cm2. 10mm rare earth magnesium ferrosilicon alloy (the chemical composition and mass fraction of the rare earth magnesium ferrosilicon alloy are: 7.26% RE, 8.19% Mg, 41.03% Si, 0.71% Ti, 0.55% Al, the balance is Fe and inevitable impurities) and nano-TiC; the nano-TiC is placed on the rare earth magnesium ferrosilicon alloy, and the rare earth magnesium ferrosilicon alloy and the nano-TiC added account for 0.60% and 0.13% of the mass fraction of the molten steel entering the ladle respectively; after the molten steel is slag-stripped and allowed to stand, when the temperature drops to 1523°C, the molten steel is directly cast on a billet continuous casting machine into a billet with a cross-section of 180mm×180mm, and the billet outlet of the crystallizer is continuously pulled out at a pulling speed of 0.80 m / min; then the billet is directly rolled on a rolling mill into a round steel bar with a diameter of Φ100mm;

[0051] ③ The length of the round steel bar with a diameter of Φ100mm obtained in step ② is cut into 7.5m; then the round steel bar with a length of 7.5m is placed in a heating furnace for heating, and after the round steel bar is evenly heated to 1270°C and kept warm for 85 minutes, the round steel bar is transported to a continuous cutting machine through a steel bar conveying device with a heat preservation device for cutting to obtain a steel segment with a length of 273.1mm; then the steel segment is forged into a steel ball with a diameter of Φ160mm, and the final forging temperature is controlled at 995-1045°C; when the forged steel ball is air-cooled to a surface temperature of 840-866°C, it is placed in a water pool at a temperature of 33°C for cooling for 75 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1; then the water-cooled steel ball is directly heated in a nitrate (the nitrate is composed of 53% by mass of KNO) at a temperature of 295°C 3 and 47% NaNO 3The isothermal quenching is carried out in the molten metal of the composition, and the isothermal time is 2.4 hours; in the isothermal quenching pool, the mass ratio of the nitrate melt to the steel ball is greater than 8:1; then the wear-resistant steel ball can be obtained by air cooling, and the mechanical properties of the steel ball are shown in Table 1;

[0052] ④ The wear-resistant steel balls obtained in step ③ are added into a large semi-autogenous mill with a diameter of 11.3 meters for crushing molybdenum ore. The method of adding the balls is as follows: the amount of wear-resistant steel balls added accounts for 33% of the volume of the semi-autogenous mill; the amount of wear-resistant steel balls with diameters of Φ140mm, Φ150mm, Φ160mm and Φ170mm respectively accounts for 15%, 17%, 28% and 40% of the total mass fraction of wear-resistant steel balls added into the semi-autogenous mill.

[0053] Table 1 Mechanical properties of steel balls

[0054]

[0055] The wear-resistant steel balls of the present invention are made of continuous casting steel billets smelted with scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide as the main furnace materials, without adding alloy raw materials such as ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, ferrovanadium, nickel, copper, etc., with low production cost and efficient utilization of waste materials. The material cost of the steel balls of the present invention is more than 30% lower than that of the commonly used B3 steel. The wear-resistant steel balls of the present invention realize continuous casting and rolling, with high production efficiency and a high steel ball forging qualified rate of more than 99.5%, making it easy to achieve efficient production. After forging, the wear-resistant steel balls of the present invention adopt a composite process of short-time quenching by waste water cooling + isothermal quenching to prepare steel balls with a diameter of 140mm-170mm, which have excellent hardenability, surface hardness ≥61HRC, core hardness ≥58HRC, and impact toughness ≥45J / cm 2 , tensile strength ≥1400MPa. A drop test was carried out on a drop ball test machine at a height of 5 meters, and the number of single ball drops was >8000 times without cracking or breaking. The wear-resistant steel ball has fine microstructure, uniform distribution, excellent impact crushing resistance, and high impact fatigue life. The wear-resistant steel ball of the present invention obtains a complex phase structure of lower bainite + residual austenite with a volume fraction of 8-12%, and has an excellent work hardening effect. After being used on a large semi-autogenous mill with a diameter of more than 10 meters, the surface hardness of the steel ball is increased by 3-5HRC, reaching more than 64HRC. The wear-resistant steel ball of the present invention does not crack, peel off or lose roundness during use, and can meet the use requirements of mines. Under the same working conditions, the wear of the wear-resistant steel ball of the present invention is more than 32% lower than that of the B3 steel forging ball. The use of the wear-resistant steel ball of the present invention can significantly improve the production efficiency of large semi-autogenous mills, reduce the grinding cost, and has significant economic and social benefits.

Claims

1. A method for preparing wear-resistant steel balls for large semi-autogenous grinding mills, characterized in that: Wear-resistant steel balls are made from continuous casting billets smelted mainly from scrapped automobile shells, scrapped cold rolling rollers and waste silicon carbide. The specific process steps include the following: ① First, the scrapped car shell is roughly shredded by a scrap car shredder, and then the roughly shredded scrapped car shell is packaged into steel blocks with a size of 180-260mm×180-260mm×180-260mm by a scrap steel baler; the scrapped cold rolling roller 9Cr2Mo is also crushed into cold rolling roller 9Cr2Mo blocks with a size of 10-220mm×10-220mm×10-220mm by a drop hammer crushing device; ② The steel blocks and 9Cr2Mo cold-rolled roller fragments, waste silicon carbide and aluminum silicon calcium alloy in step ① are used as furnace charges, and molten steel is smelted in an electric furnace; the mass compositions of the steel blocks, 9Cr2Mo cold-rolled roller fragments, waste silicon carbide and aluminum silicon calcium alloy in the furnace charges are: 86.0-86.6%, 10.0-10.8%, 2.5-2.7%, 0.6-0.7%, respectively, and the sum of the mass fractions of the four furnace charges is 100%; firstly, the steel blocks with a mass fraction of 86.0-86.6% and the cold-rolled roller 9Cr2Mo fragments with a mass fraction of 10.0-10.8% are mixed, heated and melted in an electric furnace; after the steel blocks and the cold-rolled roller 9Cr2Mo fragments are completely melted, waste silicon carbide with a mass fraction of 2.5-2.7% is added; after the waste silicon carbide is completely melted, the temperature is raised to 1633-1648°C, Aluminum-silicon-calcium alloy with a mass fraction of 0.6-0.7% is added, and after heat preservation for 8-10 minutes, the molten steel in the furnace is taken out of the furnace into a ladle, and rare earth magnesium-silicon-iron alloy and nano-TiC with a particle size of 5-10 mm are pre-added to the bottom of the ladle; the nano-TiC is placed on the rare earth magnesium-silicon-iron alloy, and the amount of rare earth magnesium-silicon-iron alloy and nano-TiC added accounts for 0.50-0.65% and 0.12-0.13% of the mass fraction of the molten steel entering the ladle respectively; after the molten steel is slag-scraped and left to stand, when the temperature drops to 1516-1528° C., the molten steel is directly cast into a square billet with a cross-section of 180 mm×180 mm on a billet continuous casting machine, and the billet is continuously pulled out at an outlet of the crystallizer at a pulling speed of 0.70-0.85 m / min; then the square billet is directly rolled into a round steel bar with a diameter of Φ90-110 mm on a rolling mill; ③ The round steel rod with a diameter of Φ90-110 mm obtained in step ② is cut into 6-8 m in length; the round steel rod with a length of 6-8 m is then placed in a heating furnace for heating, and after the round steel rod is uniformly heated to 1250-1280° C. and kept warm for 80-100 minutes, the round steel rod is conveyed to a continuous cutting machine through a steel rod conveying device with a heat preservation device for cutting to obtain steel segments with a length of 225-275 mm; the steel segments are then forged into steel balls with a diameter of Φ140-170 mm in various diameters, The final forging temperature is controlled at 980-1050°C; when the forged steel ball is air-cooled to a surface temperature of 835-870°C, it is placed in a water pool at a temperature of 25-38°C for cooling for 60-80 seconds; the mass ratio of water to steel ball in the water pool is greater than 10:1; the water-cooled steel ball is then directly isothermally quenched in a nitrate melt at a temperature of 265-300°C for an isothermal time of 2.0-2.5 hours; in the isothermal quenching pool, the mass ratio of nitrate melt to steel ball is greater than 8:1; and then air-cooling is performed to obtain the wear-resistant steel ball.

2. The preparation method according to claim 1, characterized in that: The chemical composition and mass fraction of the scrapped cold rolling roller 9Cr2Mo are: 0.85-0.95% C, 1.70-2.10% Cr, 0.20-0.35% Mn, 0.20-0.40% Mo, 0.25-0.45% Si, ≤0.25% Ni, ≤0.025% P, ≤0.025% S, and the remainder is Fe and unavoidable impurities.

3. The preparation method according to claim 1, characterized in that: The chemical composition and mass fraction of the aluminum-silicon-calcium alloy are: 8.64-8.97% Ca, 28.37-29.81% Si, and the remainder is Al and unavoidable impurities.

4. The preparation method according to claim 1, characterized in that: The chemical composition and mass fraction of the rare earth magnesium ferrosilicon alloy are: 6-8% RE, 7-9% Mg, 35-44% Si, ≤1% Ti, ≤1% Al, and the remainder is Fe and unavoidable impurities.

5. The preparation method according to claim 1, characterized in that: The nitrate is composed of 50-55% by mass of KNO3 and 45-50% by mass of NaNO3.

6. A wear-resistant steel ball prepared according to the method described in any one of claims 1 to 5.

7. A method for using the wear-resistant steel ball prepared by the method according to any one of claims 1 to 5, characterized in that: Wear-resistant steel balls of various diameters ranging from Φ140 to 170 mm are added to a large semi-autogenous mill with a diameter greater than 10 meters for crushing ore. The method for adding the balls is as follows: the volume of the wear-resistant steel balls added accounts for 30% to 35% of the volume of the semi-autogenous mill; the diameters of the wear-resistant steel balls of various diameters ranging from Φ140 to 170 mm are Φ140 mm, Φ150 mm, Φ160 mm and Φ170 mm respectively; the added amounts of the wear-resistant steel balls of diameters Φ140 mm, Φ150 mm, Φ160 mm and Φ170 mm respectively account for 12 to 15%, 15 to 18%, 25 to 28% and 40 to 45% of the total mass fraction of the wear-resistant steel balls added into the semi-autogenous mill.

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