Non-ferrous metal mine wear-resistant steel ball and preparation method thereof

Abstract

The application discloses a non-ferrous metal mine wear-resistant steel ball and a preparation method thereof, and relates to the field of metal materials. The preparation method comprises the following steps: mixing raw materials to carry out refining, continuously casting to obtain a round long blank, subsequently heating and precision forging to obtain a forged ball, and carrying out multistage cyclic isothermal quenching-tempering heat treatment to obtain the wear-resistant steel ball; the wear-resistant steel ball comprises C: 0.58%-0.66%, Si: 1.50%-1.90%, Mn: 0.70%-0.90% and Cr: 0.70%-0.90%. The application adopts a hypoeutectoid steel system, meanwhile, high Si content is adopted to compensate for the solid solution loss of carbon, the demand of a medium-sized steel ball on high hardenability can be met, aluminum and oxygen are controlled in the whole process, and external oxidation is avoided. Meanwhile, the multistage cyclic isothermal quenching-tempering heat treatment process is customized, the multi-phase organization ratio is finely controlled and regulated, and the hardness and impact performance of the wear-resistant steel ball are improved through multi-organization collaborative optimization, so that the comprehensive capability of the wear-resistant steel ball is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of metallic materials, and more particularly to a wear-resistant steel ball for non-ferrous metal mining and its preparation method. Background Technology

[0002] In the field of mining resource development, non-ferrous metal ore crushing is a crucial process before mineral sorting, and its operational efficiency and equipment maintenance costs directly determine the economic benefits of non-ferrous metal ore mining. Wear-resistant steel balls, as core vulnerable components of crushing equipment such as ball mills, directly participate in the impact and grinding process of ore, and their performance significantly affects crushing efficiency, equipment energy consumption, and production continuity. Compared to soft minerals such as iron ore and coal, non-ferrous metal ores generally have high hardness and strong abrasiveness, resulting in more demanding crushing conditions. This places higher demands on the hardness, wear resistance, and impact toughness of wear-resistant steel balls, driving the development of mining wear-resistant parts technology towards high performance and long service life.

[0003] Currently, wear-resistant steel balls used in non-ferrous metal ore crushing mainly include ordinary high-carbon steel balls, low-chromium alloy balls, and high-chromium cast iron balls. While ordinary high-carbon steel balls possess a certain degree of impact toughness, their insufficient hard phase content in the matrix leads to rapid wear in the high-hardness grinding environment of non-ferrous metal ores, resulting in a short service life and frequent downtime for replacement, severely impacting production efficiency. Low-chromium alloy balls improve wear resistance by adding a small amount of chromium; however, the increase in hardness is limited and still insufficient to meet the demands of high-strength crushing. High-chromium cast iron balls, on the other hand, suffer from insufficient toughness, making them prone to cracking and breakage under impact loads. This not only causes wear on the steel balls themselves but may also damage the ball mill cylinder, further increasing equipment maintenance costs.

[0004] Moreover, the traditional production of wear-resistant steel balls mostly adopts the process of "melting-casting-single quenching and tempering". This process has many limitations. On the one hand, the conventional melting and refining process has low precision in controlling the composition of the molten steel, which can easily lead to uneven distribution of key elements such as carbon, silicon and chromium, thus affecting the uniformity of the steel ball matrix. On the other hand, the cast steel balls are prone to defects such as shrinkage cavities and porosity. Subsequent single heat treatment processes are difficult to effectively eliminate these defects and cannot achieve synergistic optimization of hardness and toughness.

[0005] In summary, current wear-resistant steel balls for non-ferrous metal mining generally suffer from the technical bottleneck of balancing hardness and toughness. Furthermore, the corresponding manufacturing processes cannot precisely control the composition and microstructure of the steel balls, making them unsuitable for the high-hardness, high-impact crushing conditions of non-ferrous metal mines. As non-ferrous metal resource development extends to deeper, higher-hardness ore bodies, and the mining industry's demand for cost reduction, efficiency improvement, and green, low-carbon production becomes increasingly urgent, developing a wear-resistant steel ball specifically designed for non-ferrous metal mines that combines high hardness, high wear resistance, and excellent impact toughness has become a pressing technical challenge in the field of wear-resistant parts for mining machinery. Summary of the Invention

[0006] This invention provides a forged steel ball for non-ferrous metal mining and its preparation method. By optimizing the component ratio, controlling aluminum and oxygen throughout the entire process, and combining a multifunctional microstructure-controlled heat treatment process, a medium-sized, high-fracture, wear-resistant steel ball with high hardness and impact resistance can be prepared.

[0007] To address the aforementioned technical problems, one objective of this invention is to provide a method for preparing wear-resistant steel balls for non-ferrous metal mining, comprising the following steps: (1) Weigh the required raw materials according to the stoichiometric ratio of C, Si, Mn, Cr and Fe in the wear-resistant steel balls, mix them and add them to the refining equipment. Cover the surface with refining slag, blow inert gas at the bottom and refine to obtain molten steel. (2) The molten steel is transferred to the continuous casting tundish, the surface is covered with a tundish covering agent, and an inert gas is introduced for protection. A round billet is obtained by continuous casting. (3) After the circular billet is sawn, it is heated and precision forged to obtain a forged ball; (4) The forged balls are heat-treated by isothermal treatment at temperature M1 in a salt bath furnace for time T1, followed by holding at temperature M2 for time T2, then water-quenched to room temperature, and then low-temperature tempering at temperature M3 for time T3. M1 is 160-180℃, T1 is 1-3 h, M2 is 850-900℃, T2 is 3-10 min, M3 is 300-350℃, T3 is 20-40 min, and water-quenched to room temperature to obtain wear-resistant steel balls. The wear-resistant steel ball comprises the following components by mass fraction: C: 0.58%-0.66%, Si: 1.50%-1.90%, Mn: 0.70%-0.90%, Cr: 0.70%-0.90%, Mo≤0.15%, Al≤0.01%, O≤0.02%, P≤0.025%, S≤0.025%, with the balance being Fe and unavoidable impurities. The diameter of the wear-resistant steel ball is 110-130 mm.

[0008] This application optimizes the alloy composition system, employing a hypoeutectoid steel system with high C content while using a higher Si content to compensate for the lack of carbon solid solution, resulting in high impact resistance and high hardenability, meeting the high hardenability requirements for processing medium-sized steel balls. Furthermore, it controls aluminum and oxygen throughout the entire process, utilizing the alloying elements C, Si, and Mn for deoxidation while minimizing external oxidation through efficient refining and protective methods. Simultaneously, it customizes the heat treatment process based on the alloy's thermal expansion phase transformation curve and phase transformation behavior, finely controlling the multiphase microstructure ratio, enabling the steel balls to possess both high hardness and high impact resistance and wear resistance.

[0009] Specifically, this application describes a multi-stage cyclic isothermal quenching-tempering process for the involved composition system. After forging, the system first undergoes low-temperature salt bath quenching at temperature M1. By controlling the cooling rate, the phase transformation is controlled to occur simultaneously with bainite and martensite, significantly avoiding the generation of internal stress. The simultaneous occurrence of diffusionless and semi-diffusional phase transformations promotes tight microstructure bonding and inhibits dislocation propagation. Next, after isothermal quenching, the system undergoes re-austenitization at temperature M2. This re-austenitizes some of the high-activation-energy grains at the edges, or spheroidizes some of the retained austenite. Water quenching then forces this portion of austenite to transform into martensite, further refining the microstructure, but also introducing some internal stress. Finally, low-temperature tempering at temperature M3 restores the internal stress generated by the multi-stage cyclic isothermal quenching and also partially distributes carbon, increasing the carbon content of the retained austenite and enabling the TRIP effect to absorb more external stress. Ultimately, a multi-structure synergistic optimization structure is formed, with the edge structure consisting of wear-resistant bainite, martensite, and austenite, and the core structure consisting of bainite and austenite. This results in the preparation of medium-sized wear-resistant steel balls with high hardness, high wear resistance, and impact resistance, further enhancing their overall performance.

[0010] In some embodiments, the mass fraction of Si in the wear-resistant steel ball is 1.6%-1.9%.

[0011] In some embodiments, the mass fraction of C in the wear-resistant steel ball is 0.62%-0.66%.

[0012] The Si and C contents in the wear-resistant steel balls of this application are preferably within the aforementioned higher range. The wear-resistant steel balls utilize the C content of a hypoeutectoid steel system. This ensures sufficient martensite formation after quenching, resulting in higher hardness and wear resistance. Simultaneously, it avoids excessively high C content, which could lower the martensitic transformation temperature (Ms), increase retained austenite, and raise quenching stress, thereby reducing the risk of heat treatment cracking and service-related brittle fracture. This range facilitates a balance between hardness and impact toughness in medium-sized steel balls, while preventing quenching cracking during heat treatment. Furthermore, the higher Si content compensates for the lack of carbon solid solution, preventing the decrease in impact performance caused by hypereutectoid carbon. This ensures that while maintaining high hardness, the steel balls also possess high impact resistance and high hardenability, meeting the high hardenability requirements during the processing of medium-sized steel balls. If the hardenability is too low, the cooling rate of the steel ball core is slow, which easily forms soft structures such as pearlite, ferrite or coarse upper bainite, resulting in an increased difference in hardness between the surface and the core. During service, deformation, spalling, out-of-roundness and premature breakage are likely to occur, thereby reducing the crushing efficiency and service life.

[0013] In some embodiments, in step (1), the required raw materials are weighed according to the stoichiometric ratio of C, Si, Mn, Cr and Fe.

[0014] In some embodiments, in step (1), the refining slag is a magnesium oxide-containing refining slag. Using MgO-containing refining slag is beneficial to improving the slag's ability to cover and protect the molten steel and adsorb inclusions, and to reducing secondary pollution caused by furnace lining erosion during the refining process.

[0015] In some embodiments, in step (1), the refining slag comprises 45%-55% CaO, 35%-45% SiO2, 1%-5% Al2O3 and 5%-10% MgO by mass fraction.

[0016] In some embodiments, in step (1), the raw material includes at least one of molten iron, industrial graphite, industrial ferrosilicon, industrial electrolytic manganese and industrial chromium, wherein the industrial ferrosilicon has an Al mass fraction of less than or equal to 0.5%.

[0017] In some embodiments, in step (1), the industrial ferrosilicon comprises 70%-80% Si, 0.1%-0.5% Al and the balance Fe by mass.

[0018] In some implementations, the refining time in step (1) is 35-45 min.

[0019] In some implementations, in step (1), the inert gas flow rate is indicated by the slight movement of the slag surface.

[0020] In some embodiments, in step (2), the intermediate covering agent comprises 35%-45% CaO and 25%-35% SiO by mass fraction. 2、 1%-5% Al2O3, 12%-18% MgO and 10%-15% CaF2.

[0021] This application employs strict aluminum control throughout the entire manufacturing process, utilizing low-alumina refining slag, intermediate ladle covering agents, and industrial ferrosilicon raw materials. This prevents the formation of angular inclusions from the alumina resulting from the combination of aluminum and oxygen. These inclusions are highly susceptible to becoming crack initiations during impact, wear resistance, and service life, especially cracking caused by stress concentration at the corners of these inclusions, which significantly impacts service life. Simultaneously, the entire manufacturing process undergoes rigorous anti-oxidation protection. By using magnesium oxide-containing refining slag and refining and casting under inert gas conditions, external oxidation is significantly reduced, avoiding the deoxidation difficulties associated with low-alumina materials. This effectively improves the cleanliness and microstructure uniformity of the raw billet, thereby enhancing the hardness and impact performance of the wear-resistant steel balls.

[0022] In some embodiments, in step (2), the diameter of the circular blank is 100-150 mm.

[0023] In some embodiments, in step (3), the heating temperature is 1100-1200 ℃ and the holding time is 1-2 h.

[0024] The steel balls used in this application are forged at high temperatures, which can minimize internal and external cracking caused by the processing, allow for full dynamic recrystallization to form fine and broken austenite grains, and further refine the microstructure and promote uniform composition during subsequent heat treatment.

[0025] In some implementations, in step (3), the forging pressure of precision forging is less than or equal to 3 mm.

[0026] In some embodiments, in step (4), the salt used in the salt bath furnace is industrial silica sand salt with uniform particle size.

[0027] To solve the above-mentioned technical problems, the second objective of this invention is to provide a wear-resistant steel ball for non-ferrous metal mining.

[0028] Compared with the prior art, the present invention has the following beneficial effects: 1. The wear-resistant steel ball of this application optimizes the alloy composition system and adopts a hypoeutectoid steel system to avoid quenching cracks in the wear-resistant steel ball during the heat treatment stage. At the same time, it uses a higher Si content to make up for the lack of carbon solid solution and avoids the decrease in impact performance caused by carbon hypereutectoid. It has high impact resistance and high hardenability while maintaining high hardness, which can meet the high hardenability requirements of medium-sized steel ball processing.

[0029] 2. This application employs a multi-stage cyclic isothermal quenching-tempering process for the involved composition system. Low-temperature salt bath quenching is performed at 160-180℃ to control the co-occurrence of lower bainite and martensite during phase transformation. The system is then held at 850-900℃ for re-austenitization, and water quenching forces this portion of austenite to transform into martensite, refining the microstructure. Low-temperature tempering at 300-350℃ promotes an increase in the carbon content of the residual austenite and absorbs external stress. Ultimately, a multi-structure synergistic optimization structure is formed, with the edge microstructure consisting of wear-resistant bainite, martensite, and austenite, and the core microstructure consisting of bainite and austenite. This improves the hardness and impact performance of the wear-resistant steel ball, resulting in high comprehensive performance.

[0030] 3. This application uses low-aluminum refining slag, intermediate ladle covering agent and raw materials to strictly control aluminum throughout the entire process, so as to avoid the products formed by the combination of aluminum and oxygen, which are extremely easy to become crack sources during impact, wear resistance and service. At the same time, strict anti-oxidation protection is carried out throughout the process, which can significantly reduce external oxidation, avoid the deoxidation difficulties caused by low aluminum, effectively improve the cleanliness and uniformity of the raw billet, thereby improving the hardness and impact performance of wear-resistant steel balls. Attached Figure Description

[0031] Figure 1 This is a metallographic image of a wear-resistant steel ball for non-ferrous metal mining according to Embodiment 1 of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0034] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0035] As used in this article: In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0036] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0037] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", etc., indicating orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0038] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are all commercially available, and the same raw materials were used in parallel experiments.

[0039] Example 1 A wear-resistant steel ball for non-ferrous metal mining comprises the following components by mass fraction: C: 0.66%, Si: 1.60%, Mn: 0.90%, Cr: 0.83%, Mo: 0.004%, Al: 0.002%, O: 0.0019%, P: 0.01%, S: 0.001%, with the balance being Fe and unavoidable impurities. The preparation method of this wear-resistant steel ball includes the following steps: (1) Weigh the required raw materials according to the composition ratio of C, Si, Mn, Cr and Fe in the wear-resistant steel ball and the amount of burning loss. The raw materials are molten iron, industrial graphite, low-aluminum industrial ferrosilicon, industrial electrolytic manganese and industrial chromium. Among them, industrial ferrosilicon includes 75% Si, 0.5% Al and the balance Fe by mass. (2) Alloying: Industrial graphite is added to the molten iron at the end of the converter. After being transferred to the LF refining furnace, industrial chromium, industrial ferrosilicon and industrial electrolytic manganese are added in sequence. Then, a low-alumina refining slag containing magnesium oxide is covered on top. Argon gas is blown from the bottom and the refining is carried out for 40 minutes. The argon gas flow rate is indicated by the slight movement of the slag surface. The refining slag includes 50% CaO, 40% SiO2, 3% Al2O3 and 7% MgO by mass fraction to prepare molten steel. (3) Casting: The molten steel is transferred to the continuous casting tundish. A low-alumina tundish covering agent is added to the surface of the molten steel in the tundish for covering. At the same time, a small amount of argon gas is blown from the top for protection. The tundish covering agent includes 40% CaO and 30% SiO2 by mass. 2、 3% Al2O3, 15% MgO and 12% CaF2, the sprue is made of zirconium oxide, and it is continuously cast into a Ø120 mm round billet through a circular crystallizer. (4) Forging: After the round billet is sawn, it is heated to 1150 ℃ in a medium frequency furnace and held for 1 h for precision forging. The forging pressure does not exceed 3 mm to obtain Ø120 mm forged ball; (5) Heat treatment: The forged balls are air-cooled through a slide and run to a salt bath furnace. The salt used is industrial silica sand salt with uniform particle size. After isothermal treatment at M1 temperature for T1 time, the balls are held at M2 temperature in a medium frequency furnace for T2 time. Then, they are water-quenched to room temperature, dried, and then tempered at low temperature in a low temperature furnace at M3 temperature for T3 time. M1 is 160 ℃, T1 is 2 h, M2 is 900 ℃, T2 is 5 min, M3 is 350 ℃, T3 is 30 min. Finally, the balls are water-quenched to room temperature to obtain wear-resistant steel balls.

[0040] Example 2 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as that in Example 1, with the same raw materials, equipment and process parameters. The difference is that the wear-resistant steel ball includes the following components by mass fraction: C: 0.58%, Si: 1.90%, Mn: 0.70%, Cr: 0.76%, Mo: 0.005%, Al: 0.003%, O: 0.0023%, P: 0.015%, S: 0.004%, with the balance being Fe and unavoidable impurities.

[0041] Example 3 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1, with the same raw materials, equipment and process parameters. The difference is that the wear-resistant steel ball includes the following components by mass fraction: C: 0.60%, Si: 1.73%, Mn: 0.78%, Cr: 0.89%, Mo: 0.005%, Al: 0.002%, O: 0.0021%, P: 0.016%, S: 0.002%, with the balance being Fe and unavoidable impurities.

[0042] Example 4 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1. The difference is that in step (5), M1 is 180 ℃, T1 is 2 h, M2 is 900 ℃, T2 is 5 min, M3 is 350 ℃, and T3 is 30 min.

[0043] Example 5 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1. The difference is that in step (5), M1 is 160 ℃, T1 is 2 h, M2 is 850 ℃, T2 is 5 min, M3 is 350 ℃, and T3 is 30 min.

[0044] Example 6 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1. The difference is that in step (5), M1 is 160 ℃, T1 is 2 h, M2 is 900 ℃, T2 is 5 min, M3 is 300 ℃, and T3 is 30 min.

[0045] Example 7 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1, with the same raw materials, equipment and process parameters. The difference is that the wear-resistant steel ball includes the following components by mass fraction: C: 0.66%, Si: 1.90%, Mn: 0.90%, Cr: 0.83%, Mo: 0.005%, Al: 0.003%, O: 0.0022%, P: 0.011%, S: 0.002%, with the balance being Fe and unavoidable impurities.

[0046] Example 8 A wear-resistant steel ball for non-ferrous metal mining is prepared using the same method as in Example 1, with the same raw materials, equipment, and process parameters. The difference lies in that the wear-resistant steel ball comprises the following components by mass fraction: C: 0.66%, Si: 1.50%, Mn: 0.90%, Cr: 0.83%, Mo: 0.003%, Al: 0.002%, O: 0.0021%, P: 0.015%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0047] Example 9 A wear-resistant steel ball for non-ferrous metal mining is prepared using the same method as in Example 1, with the same raw materials, equipment, and process parameters. The difference lies in that the wear-resistant steel ball comprises the following components by mass fraction: C: 0.58%, Si: 1.60%, Mn: 0.90%, Cr: 0.83%, Mo: 0.002%, Al: 0.001%, O: 0.0015%, P: 0.017%, S: 0.001%, with the balance being Fe and unavoidable impurities.

[0048] Example 10 A wear-resistant steel ball for non-ferrous metal mining is prepared using the same method as in Example 1, with the same raw materials, equipment, and process parameters. The difference lies in that the wear-resistant steel ball comprises the following components by mass fraction: C: 0.62%, Si: 1.60%, Mn: 0.90%, Cr: 0.83%, Mo: 0.005%, Al: 0.003%, O: 0.0021%, P: 0.012%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0049] Comparative Example 1 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1, with the same raw materials, equipment and process parameters. The difference is that in step (1), low-aluminum industrial ferrosilicon is replaced by conventional ferrosilicon in equal amounts. Conventional ferrosilicon includes 75% Si, 2% Al and the balance Fe by mass. In step (2), low-aluminum refining slag containing magnesium oxide is replaced by high-aluminum refining slag in equal amounts. High-aluminum refining slag includes 50% CaO, 5% SiO2 and 45% Al2O3 by mass. Conventional magnesium-aluminum material is used for the nozzle. In step (5), the forged balls are air-cooled through a slide to a medium-frequency furnace, held at temperature M2 for time T2, then water-quenched to room temperature, dried, and then tempered at low temperature in a low-temperature furnace at temperature M3 for time T3. M2 is 900 ℃, T2 is 30 min, M3 is 400 ℃, T3 is 2 h, and then water-quenched to room temperature to obtain wear-resistant steel balls.

[0050] Comparative Example 2 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1, except that in step (5), the forged ball is air-cooled through a slide to a medium-frequency furnace, held at M2 temperature for T2 time, then water-quenched to room temperature, dried, and then held at M3 temperature for T3 time in a low-temperature furnace for low-temperature tempering. M2 is 900 ℃, T2 is 30 min, M3 is 400 ℃, T3 is 2 h, and then water-quenched to room temperature to obtain the wear-resistant steel ball.

[0051] Comparative Example 3 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1. The difference is that in step (5), M1 is 120 ℃, T1 is 2 h, M2 is 900 ℃, T2 is 5 min, M3 is 350 ℃, and T3 is 30 min.

[0052] Comparative Example 4 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1. The difference is that in step (5), M1 is 250 ℃, T1 is 2 h, M2 is 900 ℃, T2 is 5 min, M3 is 350 ℃, and T3 is 30 min.

[0053] Comparative Example 5 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1. The difference is that in step (5), M1 is 160 ℃, T1 is 2 h, M2 is 900 ℃, T2 is 5 min, M3 is 250 ℃, and T3 is 30 min.

[0054] Comparative Example 6 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1. The difference is that in step (5), M1 is 160 ℃, T1 is 2 h, M2 is 900 ℃, T2 is 5 min, M3 is 400 ℃, and T3 is 30 min.

[0055] Comparative Example 7 A wear-resistant steel ball for non-ferrous metal mining is prepared using the same method as in Example 1, with the same raw materials, equipment, and process parameters. The difference lies in that the wear-resistant steel ball comprises the following components by mass fraction: C: 0.77%, Si: 1.60%, Mn: 0.90%, Cr: 0.83%, Mo: 0.003%, Al: 0.001%, O: 0.0017%, P: 0.014%, S: 0.002%, with the balance being Fe and unavoidable impurities.

[0056] Comparative Example 8 A wear-resistant steel ball for non-ferrous metal mining is prepared using the same method as in Example 1, with the same raw materials, equipment, and process parameters. The difference lies in that the wear-resistant steel ball comprises the following components by mass fraction: C: 0.66%, Si: 1.00%, Mn: 0.90%, Cr: 0.83%, Mo: 0.005%, Al: 0.002%, O: 0.0017%, P: 0.012%, S: 0.004%, with the balance being Fe and unavoidable impurities.

[0057] Comparative Example 9 A wear-resistant steel ball for non-ferrous metal mining is prepared using the same method as in Example 1, with the same raw materials, equipment, and process parameters. The difference lies in that the wear-resistant steel ball comprises the following components by mass fraction: C: 0.66%, Si: 1.00%, Mn: 0.90%, Cr: 0.83%, Mo: 0.005%, Al: 0.003%, O: 0.0022%, P: 0.012%, S: 0.004%, with the balance being Fe and unavoidable impurities. In step (3), the diameter of the circular blank is 80 mm; In step (4), the diameter of the forging ball is 80 mm.

[0058] Comparative Example 10 A wear-resistant steel ball for non-ferrous metal mining is prepared in the same way as in Example 1, with the same raw materials, equipment and process parameters. The difference is that the wear-resistant steel ball includes the following components by mass fraction: C: 0.66%, Si: 1.60%, Mn: 0.90%, Cr: 0.50%, Mo: 0.004%, Al: 0.001%, O: 0.0011%, P: 0.015%, S: 0.002%, with the balance being Fe and unavoidable impurities.

[0059] Comparative Example 11 A wear-resistant steel ball for non-ferrous metal mining is prepared using the same method as in Example 1, with the same raw materials, equipment, and process parameters. The difference lies in that the wear-resistant steel ball comprises the following components by mass fraction: C: 0.66%, Si: 1.60%, Mn: 0.50%, Cr: 0.83%, Mo: 0.006%, Al: 0.002%, O: 0.0018%, P: 0.018%, S: 0.003%, with the balance being Fe and unavoidable impurities.

[0060] Table 1 - Composition and content of wear-resistant steel balls in the embodiments and comparative examples of this application Performance testing 1. Metallographic Examination: The wear-resistant steel balls prepared in Example 1 were subjected to metallographic examination according to the ASTM metallographic examination standard. The metallographic images were observed using a metallographic microscope, and the results are shown below. Figure 1 As shown. By Figure 1 As can be seen, the microstructure of the steel ball in Example 1 is relatively fine and uniform, with no obvious coarse network carbides or severe microstructure segregation. The matrix is ​​mainly composed of bainite, martensite, and a small amount of retained austenite. In this multiphase microstructure, martensite provides high hardness and wear resistance, bainite improves impact toughness, and retained austenite can absorb external stress through the TRIP effect under impact load, thereby achieving a synergistic improvement in hardness and impact resistance.

[0061] 2. Hardness: The wear-resistant steel balls prepared in the examples and comparative examples were tested using a Rockwell hardness tester in accordance with GB / T230.1-2004 "Metallic materials - Rockwell hardness test method". The test results are shown in Table 2 below.

[0062] 3. Impact toughness: Using a pendulum impact testing machine, the wear-resistant steel balls prepared in the examples and comparative examples were tested for impact toughness in accordance with GB229-63 "Metallic materials - Test method for impact toughness at room temperature". The test was repeated three times, and the final result was the average of the three tests. The test results are shown in Table 2 below.

[0063] Table 2 - Performance test results of wear-resistant steel balls in the embodiments and comparative examples of this application In Examples 1-10 of this application, a hypoeutectoid steel system is used, while the high Si content compensates for the lack of carbon solid solution and meets the high hardenability requirement for processing 120 nm medium-sized steel balls. The entire preparation process strictly controls aluminum and oxygen, effectively avoiding external oxidation and aluminum-oxygen bonding products becoming crack sources. At the same time, the heat treatment is customized based on the alloy's thermal expansion phase transformation curve and phase transformation behavior. Through a multi-stage cyclic isothermal quenching-tempering process, the multiphase microstructure ratio is finely controlled, so that the steel balls have high hardness while also having high impact resistance. The higher hardness is beneficial to improving the steel balls' impact crushing and wear resistance against ore, while the higher impact toughness can prevent the steel balls from cracking, peeling, or breaking during repeated impacts, thus improving their overall performance.

[0064] Compared to Example 1, the wear-resistant steel ball of Comparative Example 1 was prepared using industrial ferrosilicon with high aluminum content, refining slag, and intermediate coating agent, resulting in an aluminum content of 0.01% in the final product, which is significantly higher than that of Example 1. This high aluminum content easily combines with oxygen to form angular alumina inclusions, which are extremely prone to becoming crack sources during impact, wear resistance, and service. In particular, the cracking caused by stress concentration at the corners of the inclusions leads to a significant reduction in the hardness and impact performance of the wear-resistant steel ball.

[0065] Compared to Example 1, the wear-resistant steel ball in Comparative Example 2 was not subjected to isothermal treatment at temperature M1 after precision forging. Its basic structure consisted only of martensite, resulting in high internal stress. Subsequently, it underwent austenitization at temperature M2 to form partially reversed austenite. Then, it underwent low-temperature tempering at temperature M3 to stabilize the reversed austenite. However, since it did not contain bainite, although the hardness of the wear-resistant steel ball was not reduced, its impact performance was poor.

[0066] Compared to Example 1, the wear-resistant steel ball in Comparative Example 3 had an excessively low M1 temperature during the heat treatment stage, resulting in insufficient bainite transformation and a high proportion of martensite, thus significantly reducing the impact toughness of the steel ball. In Comparative Example 4, the wear-resistant steel ball had an excessively high M1 temperature during the heat treatment stage, which easily led to the formation of coarser bainite or an unstable microstructure, resulting in a decrease in both hardness and toughness.

[0067] Compared to Example 1, the wear-resistant steel ball in Comparative Example 5 had an excessively low M3 temperature during the heat treatment stage, resulting in insufficient tempering and inadequate release of residual stress, thus reducing the impact toughness of the steel ball. The wear-resistant steel ball in Comparative Example 6 had an excessively high M3 temperature during the heat treatment stage, leading to over-tempering and softening, and a significant decrease in hardness. Although its impact toughness recovered somewhat compared to Comparative Example 5, its overall performance was still inferior to that of Example 1.

[0068] Compared to Example 1, the C content in the wear-resistant steel ball of Comparative Example 7 is too high at 0.77%. It is a eutectoid steel system, but the risk of quenching cracking, excessive retained austenite, and carbide embrittlement is significantly increased. It will quench cracking during heat treatment, resulting in a significant reduction in impact performance.

[0069] Compared to Example 1, the Si content of 1% in the wear-resistant steel ball of Comparative Example 8 is too low. For a medium-sized steel ball of 120 mm, this results in insufficient hardenability, uneven core structure, and a significant decrease in both hardness and impact toughness. Similarly, like Comparative Example 8, the Si content of the wear-resistant steel ball in Comparative Example 9 is also low at 1%. The difference lies in the fact that the wear-resistant steel ball of Comparative Example 9 is a small steel ball with a diameter of 80 mm, and its cross-section is smaller than that of the 120 mm medium-sized steel ball of Comparative Example 8. Therefore, its cooling rate is faster, and the adverse effects of low Si content are reduced. Thus, the performance of the steel ball in Comparative Example 9 is superior to that in Comparative Example 8.

[0070] Compared to Example 1, the Cr content in the wear-resistant steel ball of Comparative Example 10 is too low at 0.5%, resulting in insufficient hardenability and wear-resistant hard structure formation ability, thus reducing hardness and impact toughness due to uneven microstructure. The Mn content in the wear-resistant steel ball of Comparative Example 11 is also too low at 0.5%, reducing hardenability and the uniformity of the microstructure in thick sections, thus resulting in lower hardness and impact toughness than in Example 1.

[0071] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for preparing wear-resistant steel balls for non-ferrous metal mining, characterized in that, Includes the following steps: (1) Weigh the required raw materials according to the stoichiometric ratio of C, Si, Mn, Cr and Fe in the wear-resistant steel balls, mix them and add them to the refining equipment. Cover the surface with refining slag, blow inert gas at the bottom and refine to obtain molten steel. (2) The molten steel is transferred to the continuous casting tundish, the surface is covered with a tundish covering agent, and an inert gas is introduced for protection. A round billet is obtained by continuous casting. (3) After the circular billet is sawn, it is heated and precision forged to obtain a forged ball; (4) The forged balls are heat-treated by isothermal treatment at temperature M1 in a salt bath furnace for time T1, followed by holding at temperature M2 for time T2, then water-quenched to room temperature, and then low-temperature tempering at temperature M3 for time T3. M1 is 160-180℃, T1 is 1-3h, M2 is 850-900℃, T2 is 3-10 min, M3 is 300-350℃, T3 is 20-40 min, and water-quenched to room temperature to obtain wear-resistant steel balls. The wear-resistant steel ball comprises the following components by mass fraction: C: 0.58%-0.66%, Si: 1.50%-1.90%, Mn: 0.70%-0.90%, Cr: 0.70%-0.90%, Mo≤0.15%, Al≤0.01%, O≤0.02%, P≤0.025%, S≤0.025%, with the balance being Fe and unavoidable impurities. The diameter of the wear-resistant steel ball is 110-130 mm.

2. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 1, characterized in that, The mass fraction of Si in the wear-resistant steel ball is 1.6%-1.9%.

3. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 1, characterized in that, The mass fraction of carbon in the wear-resistant steel ball is 0.62%-0.66%.

4. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 1, characterized in that, In step (1), the refining slag comprises 45%-55% CaO, 35%-45% SiO2, 1%-5% Al2O3 and 5%-10% MgO by mass fraction.

5. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 1, characterized in that, In step (1), the raw material includes at least one of molten iron, industrial graphite, industrial ferrosilicon, industrial electrolytic manganese and industrial chromium, wherein the mass fraction of Al in the industrial ferrosilicon is less than or equal to 0.5%.

6. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 5, characterized in that, In step (1), the industrial ferrosilicon comprises 70%-80% Si, 0.1%-0.5% Al and the balance Fe by mass.

7. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 1, characterized in that, In step (2), the intermediate covering agent comprises 35%-45% CaO and 25%-35% SiO by mass fraction. 2、 1%-5% Al2O3, 12%-18% MgO and 10%-15% CaF2.

8. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 1, characterized in that, In step (3), the heating temperature is 1100-1200 ℃ and the holding time is 1-2 h.

9. The method for preparing wear-resistant steel balls for non-ferrous metal mining as described in claim 1, characterized in that, In step (4), the salt used in the salt bath furnace is industrial silica sand salt with uniform particle size.

10. A wear-resistant steel ball for non-ferrous metal mining prepared by the preparation method according to any one of claims 1-9.

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