Low-surface-defect high-chromium wear-resistant ball and preparation method thereof

Abstract

The application discloses a high-chromium wear-resistant ball with low surface defects, and the chemical components of the high-chromium wear-resistant ball include, in percentage by mass, C: 2.2-2.6%, Si: 0.5-0.7%, Mn: 0.4-0.6%, Cr: 10.0-12.0%, Mo: 0.3-0.5%, V: 0.04-0.05%, S: ≤0.02%, P: ≤0.04%, and the balance of Fe and inevitable impurities; wherein 0.5≤Mo+V≤0.6%, and Cr / C is 4.0-5.0. By selecting and controlling the chemical components and contents of the wear-resistant ball, and optimizing the steps and parameters of the preparation process, the wear-resistant ball with a metallographic structure of 60-65% (volume) of martensite, 30-35% (volume) of eutectic carbide M7C3+M3C and 2-5% (volume) of residual austenite, high hardness and high toughness is prepared, and the surface porosity, slag inclusion and sand inclusion of the wear-resistant ball are significantly reduced; the hardness HRC of the high-chromium wear-resistant ball is 65-68, the impact value is 7.6-8.6 J / cm 2 , and the falling ball impact frequency is ≥24000.

Description

Technical Field

[0001] This invention relates to the preparation of wear-resistant ball media, specifically to a high-chromium wear-resistant ball with low surface defects and its preparation method. Background Technology

[0002] High-chromium wear-resistant balls are widely used in industries such as mineral processing, metallurgy, power, and cement, and are a type of consumable with high consumption. Because they are constantly in motion, they are subjected to both abrasive wear and impact fatigue, thus requiring excellent wear resistance, hardness, and high toughness. Although there are many types of wear-resistant ball media, high-chromium wear-resistant balls are the preferred consumable material in terms of both wear resistance and cost.

[0003] Patent CN113755742A discloses a high-hardness chromium alloy cast ball, wherein the chemical composition of the cast ball, by mass percentage, includes: C: 3.4%. 3.8%, Si: 0.3% 0.9%, Mn: 0.4% 0.9%, Cr: 11.0% 15.4% Fe, S: ≤0.02%, P: ≤0.05%, with the remainder being Fe and other unavoidable impurities. The cast balls have a hardness of not less than 65 HRC, a hardness difference between the surface and the core of the ball of not more than 1 HRC, and an impact toughness of not less than 5 J / cm. 2 .

[0004] Patent CN112011723A discloses a horse cowry The austenitic high-chromium multi-element alloy cast iron grinding ball comprises the following elements by weight percentage: C 2.0-3.3%, Si 1.5-2.5%, Mn 0.3-1.5%, Cr > 10.0-14.0%, Cu 0-1.2%, Mo 0-4%, P < 0.1%, S < 0.06%, with the balance being Fe. By adding a high content of silicon, the carbide grains in the high-chromium grinding ball are refined, and the carbide distribution is improved, resulting in a fine and dispersed distribution within the matrix. This reduces the tendency of carbides to fracture the matrix. Combined with an oil-quenching and isothermal tempering heat treatment process, the grinding ball achieves a martensitic-beta-austenitic microstructure, improving the matrix's toughness and ductility, reducing the out-of-roundness and breakage rate of the grinding ball, and enhancing its wear resistance.

[0005] Patent CN102703796A discloses a high-wear-resistant, high-chromium alloy cast iron grinding ball for mining, characterized by its chemical composition and percentage content as follows: C: 2.00~2.30, Si: 0.30~0.80, Mn: 0.40~1.00, Cr: 12.50~14.00, Re: 0.02~0.03, P: ≤0.10, S: ≤0.06, Mo: ≤0.20, with the balance being Fe. It can produce mining alloy cast balls with a diameter of 100-140mm and achieves an optimal combination of metallographic structures, namely martensite (M) + alloy carbides (M7C3) + retained austenite (A). 残 This ensures the product's surface hardness, core hardness, and impact toughness, resulting in optimal overall performance. Consequently, it reduces ball consumption and breakage rate in mining production, extends the ball replenishment cycle, and thus lowers production costs and improves production efficiency.

[0006] However, the steel balls used in the applicant's foundry experience high wear throughout the year at the Dashan ore dressing plant. Therefore, the company is intensifying its new product development efforts, seeking breakthroughs in processes and materials. Through continuous experimentation, the company aims to determine optimal material composition and heat treatment processes to maximize efficiency, gradually replacing existing grinding ball varieties. This approach, aimed at reducing steel ball usage and wear, remains the direction of its research and development. Summary of the Invention

[0007] To address the shortcomings of existing technologies and practical needs, this invention provides a high-chromium wear-resistant ball with low surface defects and its preparation method. By optimizing the composition, content, and processing of the wear-resistant ball, a high-hardness and high-toughness wear-resistant ball is prepared. At the same time, the porosity, slag inclusions, and sand inclusions on the surface of the wear-resistant ball are significantly reduced. This effectively improves the service life of the wear-resistant ball and reduces the production cost for enterprises.

[0008] To achieve the above effects, the present invention adopts the following technical solution:

[0009] A high-chromium wear-resistant ball with low surface defects, wherein the chemical composition of the high-chromium wear-resistant ball, by mass percentage, comprises: C: 2.2-2.6%, Si: 0.5-0.7%, Mn: 0.4-0.6%, Cr: 10.0-12.0%, Mo: 0.3-0.5%, V: 0.1-0.3%, S: ≤0.02%, P: ≤0.04%, with the balance being Fe and unavoidable impurities; wherein 0.5≤Mo+V≤0.6%, and Cr / C is 4.0-5.0.

[0010] Furthermore, the metallographic structure of the high-chromium wear-resistant ball is 60-65% by volume of martensite, 30-35% by volume of eutectic carbide M7C3+M3C, and 2-5% by volume of retained austenite, wherein the mass ratio of M7C3 in the eutectic carbide M7C3+M3C is greater than 98.5%.

[0011] Furthermore, the high-chromium wear-resistant ball has a hardness of HRC 65–68 and an impact value of 7.6–8.6 J / cm. 2 Number of ball impacts ≥ 24000.

[0012] Higher carbon content leads to more carbides, which improves the hardness and wear resistance of the wear-resistant ball. However, excessive carbon content can reduce the toughness of the wear-resistant ball. The carbon content also needs to be balanced with chromium; the preferred carbon content is 2.2–2.6%. A Cr / C ratio of 4.0–5.0 can achieve a comprehensive balance of high hardness, high toughness, and high wear resistance, while also helping to avoid the formation of ferrite phases.

[0013] Silicon is beneficial for the deoxidation of molten steel and can improve the flowability of molten steel, thereby optimizing the castability of high-chromium wear-resistant balls. When the silicon content is below 0.5%, it is difficult to exert the above effects; however, when the content exceeds 0.7%, it will lead to embrittlement of the wear-resistant balls and will also reduce the hardness of high-chromium cast iron to a certain extent. Based on this, the silicon content in this application is preferably 0.5 to 0.7 wt%.

[0014] Similar to silicon, manganese contributes to the deoxidation and desulfurization of molten metal, and also improves hardenability and wear resistance. When the manganese content is below 0.4%, the effectiveness of these functions and effects is significantly reduced; however, when the content exceeds 0.6%, it easily leads to cracking of the wear-resistant balls during quenching. Furthermore, although manganese improves hardenability, a high manganese content also increases the proportion of retained austenite after quenching in high-chromium cast iron, thus reducing hardness. Therefore, the preferred manganese content in this application is 0.4% to 0.6%.

[0015] Chromium forms hard eutectic carbides (such as M7C3) with carbon, and is an important element in forming high-hardness carbides and ensuring wear resistance. Below 10.0%, wear resistance decreases significantly; however, when the content exceeds 12.0%, the improvement in wear resistance is not significant, which is not commensurate with the effect of increasing content, and it becomes cost-inefficient, while also reducing the castability of the steel. Therefore, the preferred chromium content in this application is 10-12%.

[0016] Molybdenum can partially enter the carbide phase, and a small portion dissolves into austenite, significantly improving the hardenability of cast iron; however, the addition of molybdenum will reduce hardness to some extent. Therefore, the preferred molybdenum content in this application is 0.3% to 0.5%.

[0017] Vanadium increases the density of wear-resistant balls, effectively ensuring the surface quality of heat-treated balls, reducing surface porosity defects, and resulting in higher elasticity and toughness. Furthermore, vanadium in carbides improves their stability and hardness. Therefore, the preferred vanadium content in this application is 0.1–0.3%; and controlling the content of molybdenum and vanadium balances hardness and impact resistance. Through extensive research, the applicant has determined that 0.5 ≤ Mo + V ≤ 0.6%.

[0018] Phosphorus is a harmful impurity element that tends to segregate at grain boundaries, forming a brittle eutectic phase with a low melting point and high hardness, which reduces the toughness of cast iron. Therefore, the preferred phosphorus content in this application is ≤0.04%.

[0019] A method for preparing a high-chromium wear-resistant ball with low surface defects, comprising the following steps:

[0020] (1) According to the chemical composition and content of high chromium wear-resistant balls, put the raw materials into a crucible, heat to 1600-1700℃ to melt into molten iron, take the molten iron to test whether the chemical composition is in compliance; if it is not in compliance, add the pure component of the insufficient element to the molten iron until the chemical composition is in compliance.

[0021] (2) Add a silicon-calcium alloy to the molten iron. After the treatment, control the content of residual total calcium in the molten iron to be 40-50 ppm. The amount of calcium-silicon alloy added is 1.3-1.5 kg / t.

[0022] (3) Sprinkle perlite slag onto the surface of the molten iron and remove the slag before pouring the molten iron;

[0023] (4) Control the temperature of the molten iron to 1450-1500℃, pour it into the casting ladle, and obtain the rough product of wear-resistant balls after cooling;

[0024] (5) After heating the rough wear-resistant balls in a heating furnace to 900-950℃ and holding for 2-3 hours, put them into quenching oil for quenching treatment for 15-20 minutes.

[0025] (6) Put the rough wear-resistant balls into a tempering furnace for tempering treatment. The tempering temperature is controlled at 150-200℃ and the tempering time is 6-7h. Then cool to room temperature.

[0026] Furthermore, the raw materials include pig iron, scrap steel, ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, and ferrovanadium.

[0027] We must ensure the quality of raw materials from the source, especially by improving the quality of main materials such as purchased scrap steel and pig iron, and reducing the impact of impurities such as mud and oil carried by scrap steel on the purity of molten iron.

[0028] During the preparation process, the addition of silicon-calcium alloy and the sprinkling of perlite slag purify the molten steel, effectively degassing it and ensuring the cleanliness of the molten iron to the greatest extent possible. The resulting wear-resistant balls exhibit significantly reduced inclusions in their metallographic structure, with a marked decrease in surface porosity, slag inclusions, and sand inclusions.

[0029] When the casting temperature is too high, the spherulites produced will be relatively large. Therefore, it is required that the temperature of each batch of molten iron be measured with a temperature gun before it is tapped, and the temperature should be controlled between 1450 and 1500℃. Furthermore, the temperature of the molten iron should be controlled between 1460 and 1480℃.

[0030] In existing technologies, most wear-resistant balls are manufactured using tempering processes at temperatures above 250°C. In practical production, the applicant modified the tempering process, lowering the tempering temperature from 250°C to 150°C. This resulted in wear-resistant balls with a hardness 1-3 degrees higher than conventional balls, while also exhibiting good impact resistance.

[0031] Compared with existing technologies, the present invention has the following beneficial effects: The present invention proposes a high-chromium wear-resistant ball with low surface defects. By selecting and controlling the chemical composition and content of the wear-resistant ball, and optimizing the steps and parameters of the preparation process, a wear-resistant ball with a metallographic structure of 60-65 vol% martensite, 30-35 vol% eutectic carbides M7C3+M3C, and 2-5 vol% retained austenite is prepared, exhibiting high hardness and high toughness. Simultaneously, the porosity, slag inclusions, and sand inclusions on the surface of the wear-resistant ball are significantly reduced. The high-chromium wear-resistant ball has a hardness HRC of 65-68 and an impact value of 7.6-8.6 J / cm. 2 Number of ball impacts ≥ 24000. Attached Figure Description

[0032] Figure 1 The images show the metallographic structure of the wear-resistant balls after corrosion in Examples 1, 6-7, and Comparative Examples 5-6. Detailed Implementation

[0033] The technical solutions of the present invention will now be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] The main technical solutions are as follows:

[0035] A high-chromium wear-resistant ball with low surface defects, wherein the chemical composition of the high-chromium wear-resistant ball, by mass percentage, comprises: C: 2.2-2.6%, Si: 0.5-0.7%, Mn: 0.4-0.6%, Cr: 10.0-12.0%, Mo: 0.3-0.5%, V: 0.1-0.3%, S: ≤0.02%, P: ≤0.04%, with the balance being Fe and unavoidable impurities; wherein the Cr / C ratio is 4.0-5.0.

[0036] A method for preparing a high-chromium wear-resistant ball with low surface defects, comprising the following steps:

[0037] (1) According to the chemical composition and content of high chromium wear-resistant balls, put the raw materials into a crucible, heat to 1600-1700℃ to melt into molten iron, take the molten iron to test whether the chemical composition is in compliance; if it is not in compliance, add the pure component of the insufficient element to the molten iron until the chemical composition is in compliance.

[0038] (2) Add a silicon-calcium alloy to the molten iron. After the treatment, control the content of residual total calcium in the molten iron to be 40-50 ppm. The amount of calcium-silicon alloy added is 1.3-1.5 kg / t.

[0039] (3) Sprinkle perlite slag onto the surface of the molten iron and remove the slag before pouring the molten iron;

[0040] (4) Control the temperature of the molten iron to 1450-1500℃, pour it into the casting ladle, and obtain the rough product of wear-resistant balls after cooling;

[0041] (5) After heating the rough wear-resistant balls in a heating furnace to 900-950℃ and holding for 2-3 hours, put them into quenching oil for quenching treatment for 15-20 minutes.

[0042] (6) Put the rough wear-resistant balls into a tempering furnace for tempering treatment. The tempering temperature is controlled at 150-200℃ and the tempering time is 6-7h. Then cool to room temperature.

[0043] Examples 1-5, Comparative Examples 1-4

[0044] To control the consistency of process parameters in the preparation method of high-chromium wear-resistant balls, high-chromium wear-resistant balls with different chemical compositions were prepared by adjusting the content of raw materials, and their mechanical properties were tested.

[0045] The consistent process steps are as follows:

[0046] (1) According to the chemical composition and content of high chromium wear-resistant balls, put the raw materials into a crucible, heat to 1650℃ to melt into molten iron, take the molten iron to test whether the chemical composition is in compliance; if it is not in compliance, add the pure component of the insufficient element to the molten iron until the chemical composition is in compliance; (2) Add silicon-calcium alloy to the molten iron, and after the treatment, control the content of residual total calcium in the molten iron to be 40-50ppm, and the amount of calcium-silicon alloy added is 1.4kg / t; (3) Sprinkle perlite slag on the surface of the molten iron, and remove the slag before pouring the molten iron; (4) Control the temperature of the molten iron to 1480℃, pour it into the casting ladle, and obtain the rough product of wear-resistant balls after cooling; (5) Put the rough product of wear-resistant balls into a heating furnace and heat to 950℃, keep it at the temperature for 2h, and then put it into quenching oil for quenching treatment. The quenching treatment time is 0min; (6) Put the rough product of wear-resistant balls into a tempering furnace for tempering treatment. The tempering temperature is controlled at 180℃ and the tempering time is 6h. Then cool to room temperature.

[0047] The specific data are shown in Tables 1 and 2 below:

[0048] Table 1

[0049]

[0050] Table 2

[0051]

[0052] Based on the above data, the high-chromium wear-resistant ball described in this application has a hardness of HRC 65–68 and an impact value of 7.6–8.6 J / cm. 2 The sample exhibits a drop ball impact count ≥24,000, demonstrating excellent mechanical properties and minimal difference between surface and core hardness. However, while Comparative Examples 1-4 also achieve a drop ball impact count ≥24,000, their hardness, impact energy, and the difference between surface and core hardness are inferior to those of this application.

[0053] By observing the appearance of the wear-resistant balls prepared above, no obvious pores were observed on the surface of the wear-resistant balls in Examples 1 to 5 of this application.

[0054] Metallographic analysis was performed on the wear-resistant balls, and the metallographic structure and content are shown in Table 3.

[0055] Table 3

[0056]

[0057] Based on the above test results, the microstructure of the wear-resistant ball in this application is martensitic eutectic carbide M7C3+M3C, residual...

[0058] The rough wear-resistant balls obtained in the batch of Example 1 were annealed at different temperatures to investigate the effect of annealing temperature on the hardness and impact energy of the wear-resistant balls. The specific test data are shown in Table 4.

[0059] Table 4

[0060]

[0061] The applicant reduced the tempering temperature from 250℃ to 150℃ during the production process by changing the tempering process. The wear-resistant balls showed a significant increase in hardness, by 1-3 HRC, and the impact energy value also increased. The metallographic structure of the two balls showed no significant difference, indicating that the method of increasing the hardness of steel balls by reducing the tempering temperature is feasible.

[0062] Also considering the presence of micro-cracks inside the steel balls, full corrosion tests were performed on the wear-resistant balls from Examples 1, 6, and 7, which failed after drop ball impact tests, as well as Comparative Examples 5 and 6. Figure 1 (1)-(3) correspond to Examples 1, 6, and 7. Figure 1 (4)-(5) Corresponding to Comparative Examples 5 and 6, high-power microscopic observation showed that the samples of the examples did not have microscopic cracks, and therefore did not have failures caused by casting defects. After corrosion, we observed that the grains of the steel balls were relatively fine, and the surface showed centripetal growth. However, high-power microscopic observation of the samples of Comparative Examples 5 and 6 revealed that their grain distribution was uneven and the grain size was also larger; and there were also a small amount of inclusion phases. The coarse grains are related to the casting temperature and the elemental composition and content, and are the main factors in improving product performance.

[0063] The applicant compiled workshop production data for replacing the wear-resistant balls used in this application, and the specific data is shown in Table 5.

[0064] Table 5

[0065]

[0066] Calculations show that after replacing the wear-resistant balls with those of this application, the unit consumption of wear-resistant balls is reduced by 0.04. The cost difference (in yuan) between the high-chromium wear-resistant balls of this application and those currently used is calculated as follows: Total unit cost of the high-chromium wear-resistant balls of this application - Total unit cost of the high-chromium wear-resistant balls currently used = 35,157,909.15 yuan - 37,247,240.03 yuan = -2,089,330.876 yuan. It is estimated that using high-chromium balls in ball mills #1, #7, and #9 will save 2 million yuan annually compared to the current high-chromium wear-resistant balls. After the widespread adoption of the high-chromium wear-resistant balls of this application, it is estimated that the annual cost of wear-resistant balls used in the grinding and flotation section can be reduced by 5 million yuan. In other words, the low-surface-defect high-chromium wear-resistant balls prepared in this application have significant economic value.

[0067] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-chromium wear-resistant ball with low surface defects, characterized in that, The chemical composition of the high-chromium wear-resistant ball, by mass percentage, includes: C: 2.2–2.6%, Si: 0.5–0.7%, Mn: 0.4–0.6%, Cr: 10.0–12.0%, Mo: 0.3–0.5%, V: 0.1–0.3%, S: ≤0.02%, P: ≤0.04%, with the balance being Fe and unavoidable impurities; wherein 0.5 ≤ Mo + V ≤ 0.6%, and Cr / C is 4.0–5.

0. The metallographic structure of the high-chromium wear-resistant ball is 60-65% by volume martensite, 30-35% by volume eutectic carbide M7C3+M3C, and 2-5% by volume retained austenite, wherein the mass ratio of M7C3 in the eutectic carbide M7C3+M3C is greater than 98.5%. The high-chromium wear-resistant ball has a hardness of HRC 65–68 and an impact value of 7.6–8.6 J / cm. 2 Number of ball impacts ≥ 24000; The preparation method of the high-chromium wear-resistant ball with low surface defects includes the following steps: (1) According to the chemical composition and content of high chromium wear-resistant balls, put the raw materials into a crucible, heat to 1600-1700℃ to melt into molten iron, take the molten iron to test whether the chemical composition is in compliance; if it is not in compliance, add the pure component of the insufficient element to the molten iron until the chemical composition is in compliance. (2) Add silicon-calcium alloy to molten iron, and after the treatment, control the content of residual total calcium in molten iron to be 40-50 ppm. The amount of silicon-calcium alloy added is 1.3-1.5 kg / t. (3) Sprinkle perlite slag onto the surface of the molten iron and remove the slag before pouring the molten iron; (4) Control the temperature of the molten iron to 1450-1500℃, pour it into a casting ladle, and obtain the rough product of wear-resistant balls after cooling. (5) After heating the rough wear-resistant balls in a heating furnace to 900-950℃ and holding for 2-3 hours, put them into quenching oil for quenching treatment for 15-20 minutes. (6) The quenched wear-resistant balls are placed in a tempering furnace for tempering treatment. The tempering temperature is controlled at 150-200℃ and the tempering time is 6-7h. Then, they are cooled to room temperature.

2. The high-chromium wear-resistant ball with low surface defects according to claim 1, characterized in that, The raw materials include pig iron, scrap steel, ferrosilicon, ferromanganese, ferrochrome, and ferromolybdenum.

3. The high-chromium wear-resistant ball with low surface defects according to any one of claims 1 to 2, characterized in that, In step (4), the temperature of the molten iron is controlled to be 1460-1480℃.

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