Ultrahigh carbon-chromium alloying rolled steel section and preparation method thereof

Abstract

The invention discloses an ultrahigh carbon-chromium alloying rolled steel section, and relates to the field of mine beneficiation. The martensite steel comprises, by mass, 1.4-1.6% of C, 0.2-0.5% of Si, 0.3-0.8% of Mn, 0.8-1.5% of Cr, less than or equal to 0.015% of P, less than or equal to 0.010% of S and the balance Fe and inevitable impurities, a martensite matrix is formed through heat treatment, Cr23C6 type carbides are distributed on the martensite matrix in a dispersed mode, the particle size of the carbides is 0.5-3 micrometers, and the volume fraction is 8-15%. The method has the beneficial effects that by optimizing the chemical component design and the heat treatment process, the wear resistance and hardness of the steel section are improved, wear is reduced, and the method is suitable for fine grinding operation of metal mines.

Description

Technical Field

[0001] This invention relates to the field of mineral processing, specifically to an ultra-high carbon chromium alloy rolled steel section and its preparation method. Background Technology

[0002] In the grinding and beneficiation process of metal mines, multi-stage grinding is a common technology, with the fine grinding stage being particularly important. Traditional grinding media often use steel balls or steel segments, but these suffer from low grinding efficiency, over-grinding, and under-grinding problems. Replacing traditional steel balls with highly wear-resistant rolled steel segments can improve grinding efficiency and reduce over-grinding. However, the wear resistance of currently used rolled steel segments is still insufficient, resulting in high wear, low production efficiency, and serious environmental pollution.

[0003] Most metal mines, both domestically and internationally, require grinding and beneficiation. The particle size of the grinding product must meet the requirements for high-efficiency beneficiation. Depending on the properties of the metal ore, especially ores with finely intercalated valuable minerals, multi-stage grinding processes are necessary, with the final grinding stage being the fine grinding stage. From a beneficiation perspective, a certain particle size range is required for the finely ground product to achieve optimal beneficiation results. Over-grinding during grinding will cause coarse particles to be adsorbed and covered by fine-grained slime during flotation, altering their surface electrical properties and leading to heterogeneous aggregation. This reduces the adsorption capacity of minerals and flotation reagents, making separation difficult and reducing flotation efficiency. Therefore, over-grinding should be minimized in fine grinding operations. Under-grinding, on the other hand, affects the concentrate grade.

[0004] In the fine grinding stage of mineral processing, steel sections are used instead of steel balls. This offers the dual advantages of a larger grinding area than steel balls and the selective crushing properties of steel bars. This not only improves grinding efficiency but also effectively reduces over-grinding and over-crushing of the ore product. Simultaneously, fine grinding operations should primarily involve grinding supplemented by slight impacts. This ensures the minerals are crushed to the appropriate particle size, preventing over-crushing.

[0005] Currently, steel sections used in mineral processing are generally produced by casting, which has problems such as poor wear resistance, high wear, low production efficiency, serious environmental pollution, and unstable product quality. Therefore, researching and developing wear-resistant steel section products with high wear resistance is of great significance for realizing green production of steel section rolling with a high degree of automation, improving the grade of metal mine concentrate, metal recovery rate, and reducing tailings disposal. Summary of the Invention

[0006] This invention addresses the technical problems of traditional mineral processing steel sections, such as poor wear resistance, high wear, low production efficiency, severe environmental pollution, and unstable product quality, by providing an ultra-high carbon chromium alloy rolled steel section. Through optimized chemical composition design and heat treatment processes, the wear resistance and hardness of the steel section are improved, wear is reduced, and it is suitable for fine grinding operations in metal mines.

[0007] The technical solution adopted in this invention is as follows: A high-carbon chromium alloy rolled steel section is provided, comprising an iron matrix with a chemical composition percentage of C 1.4-1.6%, Si 0.2-0.5%, Mn 0.3-0.8%, Cr 0.8-1.5%, P ≤ 0.015%, S ≤ 0.010%, and the balance being Fe and unavoidable impurities. After heat treatment, a martensitic matrix is ​​formed, with Cr dispersedly distributed on the martensitic matrix. 23 C6 type carbides, with a particle size of 0.5-3 μm and a volume fraction of 8-15%.

[0008] To further optimize this technical solution, the Cr 23 C6 type carbides are uniformly distributed in an equiaxed shape with an aspect ratio ≤1.5.

[0009] To further optimize this technical solution, the Rockwell hardness of the steel segment from its surface to a depth of 16 mm is ≥61 HRC.

[0010] A method for preparing ultra-high carbon chromium alloy rolled steel segments includes the following steps:

[0011] S1. Vacuum induction melting: Melting under vacuum conditions ≤10Pa, controlling the oxygen content of the molten steel to ≤30ppm, and the melting temperature to 1600-1650℃.

[0012] S2. Forging billet: Heat the steel ingot to 1150-1200℃ and hold for 2-4 hours. Forge it with a pressure of ≥300MPa, with a forging ratio of 3-5 and a final forging temperature of ≥900℃ to obtain a billet with a cross-sectional size of 1.5-2 times that of the finished product.

[0013] S3. Controlled rolling and cooling: Heat the billet to 1050-1100℃ and hold for 1-2 hours. Then, perform multiple rolling passes in the non-recrystallized austenite region. The final rolling temperature is 850-950℃, and the total compression ratio is ≥50%. After rolling, immediately cool the billet to room temperature at a cooling rate of 15-20℃ / s.

[0014] S4. Graded quenching: After the rolled steel section is heated to 980±10℃ for austenitization and held at that temperature, it is then quickly transferred to a salt bath at 280±10℃ and held for 60±10s, and then oil cooled to below 80℃.

[0015] S5. Cryogenic treatment: The quenched steel section is held at -75±5℃ for 3±0.5h.

[0016] S6. Double tempering: The first tempering temperature is 180±5℃, held for 2 hours and then air-cooled; the second tempering temperature is 150±5℃, held for 4 hours and then air-cooled.

[0017] To further optimize this technical solution, S4, graded quenching: the rolled steel section is heated to 980±10℃ for austenitization and then held at that temperature for 1.2-1.5 min per millimeter of cross-sectional thickness.

[0018] The beneficial effects of this invention are: by precisely controlling the chemical composition and through the synergy of multiple processes, Cr is dispersedly distributed on the martensitic matrix of the steel segment. 23 C6 type carbides have a surface hardness of ≥61HRC up to a depth of 16mm. Laboratory wear loss is reduced by 27-38% compared to traditional casting, industrial ore consumption is reduced by 18-26.5%, impact toughness is increased by more than 65%, and rolling process reduces energy consumption by 35% compared to casting. It has the advantages of high wear resistance, high toughness and environmental protection and energy saving. Attached Figure Description

[0019] Figure 1 Metallographic image of the ultra-high carbon chromium alloy rolled steel segment of the present invention at 200x magnification;

[0020] Figure 2 Metallographic image of the ultra-high carbon chromium alloy rolled steel segment of the present invention at 500x magnification;

[0021] Figure 3 Metallographic image of the ultra-high carbon chromium alloy rolled steel segment of the present invention at 1000x magnification.

[0022] Figure 4 Metallographic image of a traditional steel section at 200x magnification;

[0023] Figure 5 Metallographic image of a traditional steel section at 500x magnification. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of 1.4% C, 0.2% Si, 0.3% Mn, 0.8% Cr, 0.015% P, and 0.010% S, with the balance being Fe and unavoidable impurities.

[0027] Its preparation method is as follows:

[0028] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, under vacuum conditions of ≤10Pa, the melting temperature is 1600℃, argon blowing and stirring are carried out throughout the process, and the oxygen content of the molten steel is controlled to 30ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0029] S2. Forging: The steel ingot is heated to 1150℃ and held for 2 hours, and then forged on a 1000t friction press with a pressure of 300MPa. The forging ratio is 3, and the final forging temperature is 900℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size of 1.5 times that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0030] S3. Controlled rolling and cooling: The billet is heated to 1050°C and held for 1 hour. Multiple rolling passes are then performed in the non-recrystallization zone of austenite, with a final rolling temperature of 850°C and a total compression ratio ≥50%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 15℃ / s after rolling to inhibit carbide growth;

[0031] S4. Graded quenching: After the rolled steel section is heated to 980℃ for austenitization, it is held at that temperature for 1.2-1.5 minutes per millimeter of section thickness (65 minutes for Φ50mm steel section) to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a 280℃ salt bath for 60 seconds, and then oil cooled to below 80℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0032] S5. Cryogenic Treatment: The quenched steel section is held at -75℃ for 3 hours to promote the transformation of retained austenite into martensite. The surface hardness at a depth of 16mm increases from 60HRC to over 62HRC. Nanoscale carbides precipitate during the cryogenic process, which react with Cr. 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0033] S6. Double tempering: The first tempering temperature is 180℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 150℃, held for 4 hours, and then air-cooled to promote the hardening of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering.

[0034] When processing steel sections according to the above processing steps

[0035] During the processing of the steel section, the energy consumption of each step (such as vacuum induction melting, forging, controlled rolling and cooling) is monitored, and the comprehensive energy consumption is measured to be 1200 kWh / t. This application achieves more precise temperature control and reduces energy waste through vacuum induction melting. Furthermore, in the subsequent rolling process, plastic deformation reduces the formation of oxide scale, thereby reducing the energy consumption of the subsequent cleaning process. At the same time, the synergistic effect of staged quenching and controlled rolling and cooling can optimize the martensitic structure, reduce heat treatment time and temperature peaks, and further reduce energy consumption.

[0036] After processing, the steel segment underwent a standard abrasion resistance test. The steel segment was machined into a cylindrical specimen with a diameter of 25mm × 10mm and finely ground to a surface roughness Ra = 1.2μm to meet the test standard requirements. Using a dry sand rubber wheel abrasion tester conforming to ASTM G65, 20-40 mesh quartz sand (flow rate 250g / min) was continuously applied, a constant load of 136N was applied, and the abrasion was continued for 60 minutes. The results showed that the steel segment lost 0.35g during abrasion.

[0037] In industrial trials, steel sections were installed in a two-stage mill with a diameter of Φ3.6×6.0m at an iron ore mine. The actual operating conditions were set as follows: 65% of the feed particle size was -0.074mm, the slurry concentration was maintained at 38%, and the mill speed was controlled at 18 r / min. After 30 consecutive days of high-intensity operation, the precise amount of steel section replenishment reached 12,240 kg, and the calculated grinding loss per ton of ore was 0.68 kg / t. At the same time, the reagent usage in the flotation process remained stable at 320 g / t. The surface hardness of the steel section was measured to be 62.3 HRC and the hardness at a depth of 16 mm was 61.9 HRC using a Rockwell hardness tester.

[0038] Example 2

[0039] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of C 1.6%, Si 0.5%, Mn 0.8%, Cr 1.5%, P 0.005%, S 0.002%, and the balance being Fe and unavoidable impurities, is prepared by the following method:

[0040] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, under vacuum conditions of ≤10Pa, the melting temperature is 1650℃, argon blowing and stirring are carried out throughout the process, and the oxygen content of the molten steel is controlled to 20ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0041] S2. Forging: The steel ingot is heated to 1200℃ and held for 4 hours. It is then forged on a 1000t friction press with a pressure of 350MPa. The forging ratio is 5, and the final forging temperature is 950℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0042] S3. Controlled rolling and cooling: The billet is heated to 1100℃ and held for 2 hours. Multiple rolling passes are then performed in the non-recrystallization zone of austenite, with a final rolling temperature of 950℃ and a total compression ratio of 60%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 20℃ / s after rolling to inhibit carbide growth;

[0043] S4. Graded quenching: The rolled steel section is heated to 990℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 290℃ and held for 70 seconds, and then oil-cooled to below 40℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0044] S5. Cryogenic Treatment: The quenched steel section is held at -70℃ for 3.5 hours to promote the transformation of retained austenite into martensite. The surface hardness to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-scale carbides precipitate, which react with Cr... 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0045] S6. Double tempering: The first tempering temperature is 185℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 155℃, held for 4 hours, and then air-cooled to promote the hardening of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0046] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1350 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.30g of weight during wear, with a relative wear resistance index of 1.6. In the industrial test in a Φ3.6×6.0m mill, the 30-day replenishment amount is 11160kg, the wear loss per ton of ore is 0.62kg / t, the flotation reagent dosage is 300g / t, and the surface hardness of the steel segment is 63.5HRC and the 16mm depth hardness is 63HRC, as measured by a Rockwell hardness tester.

[0047] Example 3

[0048] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of 1.5% C, 0.25% Si, 0.5% Mn, 1.2% Cr, 0.008% P, and 0.005% S, with the balance being Fe and unavoidable impurities, is prepared by the following method:

[0049] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, the melting temperature is 1620℃ under vacuum conditions ≤10Pa. Argon is blown and stirred throughout the process, and the oxygen content of the molten steel is controlled to 25ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0050] S2. Forging: The steel ingot is heated to 1180℃ and held for 3 hours. It is then forged on a 1000t friction press with a pressure of 320MPa. The forging ratio is 4, and the final forging temperature is 920℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0051] S3. Controlled rolling and cooling: The billet is heated to 1080°C and held for 1.5 hours. Multiple rolling passes are then performed in the non-recrystallized austenite region, with a final rolling temperature of 900°C and a total compression ratio of 55%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 18℃ / s after rolling to inhibit carbide growth;

[0052] S4. Graded quenching: The rolled steel section is heated to 980℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 290℃ and held for 65 seconds, and then oil-cooled to below 40℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0053] S5. Cryogenic Treatment: The quenched steel section is held at -75℃ for 3 hours to promote the transformation of retained austenite into martensite. The surface hardness up to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-sized carbides precipitate, which react with Cr. 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0054] S6. Double tempering: The first tempering temperature is 180℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 150℃, held for 4 hours, and then air-cooled to promote the hardening of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0055] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption is 1250 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.32g of weight during wear, with a relative wear resistance index of 1.5. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 0.65 kg / t, the flotation reagent dosage was 330 g / t, and the surface hardness of the steel segment was measured to be 62.5 HRC and the 16mm depth hardness was 61.9 HRC by a Rockwell hardness tester.

[0056] Example 4

[0057] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of 1.45% C, 0.5% Si, 0.8% Mn, 1.5% Cr, 0.005% P, and 0.010% S, and the balance being Fe and unavoidable impurities, is prepared by the following method:

[0058] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, the melting temperature is 1630℃ under vacuum conditions ≤10Pa, argon blowing and stirring are carried out throughout the process, and the oxygen content of the molten steel is controlled to 22ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0059] S2. Forging: The steel ingot is heated to 1190℃ and held for 3.5h. It is then forged on a 1000t friction press at a pressure of 350MPa. The forging ratio is 4.5 and the final forging temperature is 930℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0060] S3. Controlled rolling and cooling: The billet is heated to 1090℃ and held for 1.8 hours. Multiple rolling passes are then performed in the non-recrystallized austenite region, with a final rolling temperature of 880℃ and a total compression ratio of 58%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 19℃ / s after rolling to inhibit carbide growth;

[0061] S4. Graded quenching: The rolled steel section is heated to 985℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 285℃ and held for 63 seconds, and then oil-cooled to below 40℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0062] S5. Cryogenic Treatment: The quenched steel section is held at -73℃ for 3.2 hours to promote the transformation of retained austenite into martensite. The surface hardness to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-sized carbides precipitate, which react with Cr... 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0063] S6. Double tempering: The first tempering temperature is 178℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 152℃, held for 4 hours, and then air-cooled to promote the hardness of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0064] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1320 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.31g of weight during wear, with a relative wear resistance index of 1.55. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 0.63kg / t, the flotation reagent dosage was 325g / t, and the surface hardness of the steel segment was measured to be 63.0 HRC and the 16mm depth hardness was 62.5 HRC by a Rockwell hardness tester.

[0065] Example 5

[0066] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of 1.55% C, 0.4% Si, 0.6% Mn, 1.3% Cr, 0.015% P, and 0.009% S, with the balance being Fe and unavoidable impurities, is prepared by the following method:

[0067] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, the melting temperature is 1610℃ under vacuum conditions ≤10Pa, argon blowing and stirring are carried out throughout the process, and the oxygen content of the molten steel is controlled to 28ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0068] S2. Forging: The steel ingot is heated to 1160℃ and held for 2.5h. It is then forged on a 1000t friction press with a pressure of 300MPa. The forging ratio is 3.5 and the final forging temperature is 910℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0069] S3. Controlled rolling and cooling: The billet is heated to 1060℃ and held for 1.2 hours. Multiple rolling passes are then performed in the non-recrystallized austenite region, with a final rolling temperature of 860℃ and a total compression ratio of 50%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 16℃ / s after rolling to inhibit carbide growth;

[0070] S4. Graded quenching: The rolled steel section is heated to 970℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 270℃ and held for 55 seconds, and then oil-cooled to below 40℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0071] S5. Cryogenic Treatment: The quenched steel section is held at -77℃ for 2.8 hours to promote the transformation of retained austenite into martensite. The surface hardness to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-scale carbides precipitate, which react with Cr...23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0072] S6. Double tempering: The first tempering temperature is 175℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 148℃, held for 4 hours, and then air-cooled to promote the hardness of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0073] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1200 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.34g of weight during wear, with a relative wear resistance index of 1.41. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 0.66kg / t, the flotation reagent dosage was 340g / t, and the surface hardness of the steel segment was measured to be 62.0 HRC and the 16mm depth hardness was 61.8 HRC by a Rockwell hardness tester.

[0074] Example 6

[0075] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of C 1.42%, Si 0.25%, Mn 0.5%, Cr 0.12%, P 0.008%, S 0.005%, and the balance being Fe and unavoidable impurities, is prepared by the following method:

[0076] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, the melting temperature is 1620℃ under vacuum conditions ≤10Pa. Argon is blown and stirred throughout the process, and the oxygen content of the molten steel is controlled to 25ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0077] S2. Forging: The steel ingot is heated to 1180℃ and held for 3 hours. It is then forged on a 1000t friction press with a pressure of 350MPa. The forging ratio is 4, and the final forging temperature is 920℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0078] S3. Controlled rolling and cooling: The billet is heated to 1080℃ and held for 1.5 hours. Multiple rolling passes are then performed in the non-recrystallized austenite region, with a final rolling temperature of 900℃ and a total compression ratio of 55%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 18℃ / s after rolling to inhibit carbide growth;

[0079] S4. Graded quenching: The rolled steel section is heated to 980℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 280℃ and held for 65 seconds, and then oil-cooled to below 40℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0080] S5. Cryogenic Treatment: The quenched steel section is held at -75℃ for 3 hours to promote the transformation of retained austenite into martensite. The surface hardness up to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-sized carbides precipitate, which react with Cr. 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0081] S6. Double tempering: The first tempering temperature is 180℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 150℃, held for 4 hours, and then air-cooled to promote the hardening of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0082] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1250 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.33g of weight during wear, with a relative wear resistance index of 1.45. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 0.67kg / t, the flotation reagent dosage was 350g / t, and the surface hardness of the steel segment was measured to be 62.0 HRC and the 16mm depth hardness was 61.5 HRC by a Rockwell hardness tester.

[0083] Example 7

[0084] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of C 1.6%, Si 0.4%, Mn 0.6%, Cr 1.3%, P 0.015%, S 0.009%, and the balance being Fe and unavoidable impurities, is prepared by the following method:

[0085] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, under vacuum conditions of ≤10Pa, the melting temperature is 1640℃, argon blowing and stirring are carried out throughout the process, and the oxygen content of the molten steel is controlled to 28ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0086] S2. Forging: The steel ingot is heated to 1200℃ and held for 4 hours. It is then forged on a 1000t friction press with a pressure of 350MPa. The forging ratio is 4.8 and the final forging temperature is 940℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0087] S3. Controlled Rolling and Cooling: The billet is heated to 1100℃ and held for 2 hours. Multiple rolling passes are then performed in the non-recrystallization zone of austenite, with a final rolling temperature of 950℃ and a total compression ratio of 60%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 17℃ / s after rolling to inhibit carbide growth.

[0088] S4. Graded quenching: The rolled steel section is heated to 990℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 290℃ and held for 70 seconds, and then oil-cooled to below 40℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0089] S5. Cryogenic Treatment: The quenched steel section is held at -72℃ for 3.3 hours to promote the transformation of retained austenite into martensite. The surface hardness to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-sized carbides precipitate, which react with Cr... 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0090] S6. Double tempering: The first tempering temperature is 182℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 153℃, held for 4 hours, and then air-cooled to promote the hardness of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0091] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1380 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.30g of weight during wear, with a relative wear resistance index of 1.6. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 0.64kg / t, the flotation reagent dosage was 310g / t, and the surface hardness of the steel segment was measured to be 62.8 HRC and the 16mm depth hardness was 62.3 HRC by a Rockwell hardness tester.

[0092] Example 8

[0093] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of C 1.45%, Si 0.5%, Mn 0.8%, Cr 1.5%, P 0.005%, S 0.002%, and the balance being Fe and unavoidable impurities, is prepared by the following method:

[0094] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, under vacuum conditions of ≤10Pa, the melting temperature is 1650℃, argon blowing and stirring are carried out throughout the process, and the oxygen content of the molten steel is controlled to 20ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0095] S2. Forging: The steel ingot is heated to 1200℃ and held for 4 hours. It is then forged on a 1000t friction press with a pressure of 350MPa. The forging ratio is 5, and the final forging temperature is 950℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0096] S3. Controlled Rolling and Cooling: The billet is heated to 1100℃ and held for 2 hours. Multiple rolling passes are then performed in the non-recrystallization zone of austenite, with a final rolling temperature of 950℃ and a total compression ratio of 60%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 20℃ / s after rolling to inhibit carbide growth;

[0097] S4. Graded quenching: The rolled steel section is heated to 990℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 290℃ and held for 70 seconds, and then oil-cooled to below 30℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0098] S5. Cryogenic Treatment: The quenched steel section is held at -75℃ for 3 hours to promote the transformation of retained austenite into martensite. The surface hardness up to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-sized carbides precipitate, which react with Cr. 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0099] S6. Double tempering: The first tempering temperature is 180℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 150℃, held for 4 hours, and then air-cooled to promote the hardening of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0100] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption is 1350 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.29g of weight during wear, with a relative wear resistance index of 1.66. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 0.61kg / t, the flotation reagent dosage was 300g / t, and the surface hardness of the steel segment was measured to be 63.5HRC and the 16mm depth hardness was 63.0HRC by a Rockwell hardness tester.

[0101] Example 9

[0102] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of 1.58% C, 0.3% Si, 0.45% Mn, 1.3% Cr, 0.010% P, and 0.008% S, with the balance being Fe and unavoidable impurities, is prepared by the following method:

[0103] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, the melting temperature is 1630℃ under vacuum conditions ≤10Pa. Argon blowing and stirring are carried out throughout the process, and the oxygen content of the molten steel is controlled to 26ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0104] S2. Forging: The steel ingot is heated to 1190℃ and held for 3.5h. It is then forged on a 1000t friction press at a pressure of 350MPa. The forging ratio is 4.8 and the final forging temperature is 910℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0105] S3. Controlled rolling and cooling: The billet is heated to 10900℃ and held for 1.8 hours. Multiple rolling passes are then performed in the non-recrystallized austenite region, with a final rolling temperature of 890℃ and a total compression ratio of 58%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 19℃ / s after rolling to inhibit carbide growth;

[0106] S4. Graded quenching: The rolled steel section is heated to 985℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 285℃ and held for 63 seconds, and then oil-cooled to below 30℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0107] S5. Cryogenic Treatment: The quenched steel section is held at -74℃ for 3.1 hours to promote the transformation of retained austenite into martensite. The surface hardness to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-scale carbides precipitate, which react with Cr...23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0108] S6. Double tempering: The first tempering temperature is 183℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 151℃, held for 4 hours, and then air-cooled to promote the hardness of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0109] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1330 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.32g of weight during wear, with a relative wear resistance index of 1.5. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore is 0.65kg / t, the flotation reagent dosage is 330g / t, and the surface hardness of the steel segment is 62.5HRC and the 16mm depth hardness is 62.0HRC, as measured by a Rockwell hardness tester.

[0110] Example 10

[0111] A type of ultra-high carbon chromium alloy rolled steel segment, with a mass percentage of C 1.5%, Si 0.35%, Mn 0.5%, Cr 0.12%, P 0.008%, S 0.005%, and the balance being Fe and unavoidable impurities, is prepared by the following method:

[0112] S1. Vacuum induction melting: By precisely controlling the content of alloying elements such as C and Cr, the melting temperature is 1620℃ under vacuum conditions ≤10Pa. Argon is blown and stirred throughout the process, and the oxygen content of the molten steel is controlled to 25ppm to ensure the purity of the steel, reduce the segregation of P and S impurities, and avoid the deterioration of the toughness of the matrix.

[0113] S2. Forging: The steel ingot is heated to 1170℃ and held for 2.8h. It is then forged on a 1000t friction press at a pressure of 330MPa. The forging ratio is 4.2 and the final forging temperature is 920℃. The network distribution of the cast carbides is broken, and a billet with a cross-sectional size twice that of the finished product is obtained. A deformation amount of ≥50% of the total compression ratio is reserved to ensure that the carbides are evenly distributed during the rolling process.

[0114] S3. Controlled rolling and cooling: The billet is heated to 1070℃ and held for 1.6 hours. Multiple rolling passes are then performed in the non-recrystallized austenite region, with a final rolling temperature of 880℃ and a total compression ratio of 56%. Cr is induced through rolling deformation. 23 C6 type carbide nuclei are formed, and the carbide is immediately cooled to room temperature at a cooling rate of 18℃ / s after rolling to inhibit carbide growth;

[0115] S4. Graded quenching: The rolled steel section is heated to 980℃ for austenitization and held at that temperature to allow carbon and Cr to fully dissolve and form supersaturated austenite. Then it is quickly transferred to a salt bath at 280℃ and held for 65 seconds, and then oil-cooled to below 30℃ to reduce martensitic phase transformation stress and avoid surface cracking during hardness testing.

[0116] S5. Cryogenic Treatment: The quenched steel section is held at -73℃ for 3.2 hours to promote the transformation of retained austenite into martensite. The surface hardness to a depth of 16mm increases from 60HRC to over 62HRC. During the cryogenic process, nano-sized carbides precipitate, which react with Cr... 23 C6-type carbides form a composite reinforcing phase, improving the overall hardness uniformity;

[0117] S6. Double tempering: The first tempering temperature is 180℃, held for 2 hours, and then air-cooled to eliminate quenching stress and maintain the hardness of the martensitic matrix; the second tempering temperature is 150℃, held for 4 hours, and then air-cooled to promote the hardening of Cr. 23 The stable precipitation of C6-type carbides avoids hardness reduction caused by single tempering;

[0118] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1280 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.33g of weight during wear, with a relative wear resistance index of 1.45. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 0.66kg / t, the flotation reagent dosage was 340g / t, and the surface hardness of the steel segment was measured to be 62.2 HRC and the 16mm depth hardness was 61.8 HRC by a Rockwell hardness tester.

[0119] Comparative Example 1

[0120] The steel segment has the following chemical composition by mass percentage: C 1.4%, Si 0.2%, Mn 0.3%, Cr 0.8%, P 0.015%, S 0.010%, with the balance being Fe and unavoidable impurities. Its processing steps include:

[0121] S1. Batching and smelting: Smelting is carried out in an electric arc furnace at 1550℃;

[0122] S2. Casting and molding: Sand casting is used. The mold is preheated to 100°C. Molten steel at 1500°C is poured into the mold through a ladle. After naturally cooling to room temperature, the sand mold is broken to remove flash and risers. The surface oxide scale is cleaned by sandblasting.

[0123] S3. Annealing treatment: Heat to 650℃, hold for 2-4 hours according to the cross-sectional thickness, and then cool in the furnace to below 300℃ before unloading.

[0124] S4. Machining: When dimensional accuracy is required, turning is performed to remove the surface oxide layer and achieve the design dimensions.

[0125] S5, Conventional quenching and tempering: Heat to 820℃ for austenitization, hold at that temperature, oil quench, and then temper at 200℃ for 2 hours.

[0126] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1850 kWh / t, which is significantly higher than the energy consumption in Example 1. The energy consumption mainly comes from the high heat loss in the entire sand casting process. For example, the preheating of the mold requires continuous heating, the sandblasting process for removing oxide scale requires additional mechanical energy consumption, and the heat treatment process requires annealing at high temperature for 4 hours due to poor microstructure uniformity. In addition, the conventional quenching and tempering process requires heating the steel segment to austenitization, and a single tempering requires multiple temperature increases, further increasing energy consumption. In the wear resistance test, the Φ25mm×10mm sample lost 0.52g of weight during wear, with a relative wear resistance index of 1.0. In the industrial test in the Φ3.6×6.0m mill, the wear loss per ton of ore was 1.15kg / t, the flotation reagent dosage was 420g / t, and the surface hardness of the steel segment was measured to be 58.0 HRC and the 16mm depth hardness was 53.0 HRC by Rockwell hardness tester.

[0127] Comparative Example 2

[0128] The chemical composition of the steel section is as follows: C 1.55%, Si 0.4%, Mn 0.6%, Cr 1.3%, P 0.015%, S 0.009%, with the balance being Fe and unavoidable impurities. Its processing steps include:

[0129] S1. Batching and smelting: Smelting is carried out in an electric arc furnace at 1600℃;

[0130] S2. Casting: Sand casting is used. The mold is preheated to 200°C. Molten steel at 1550°C is poured into the mold through a ladle. After naturally cooling to room temperature, the sand mold is broken to remove flash, risers and gating. The surface oxide scale is cleaned by sandblasting.

[0131] S3. Annealing treatment: Heat to 700℃, hold for 4 hours according to the cross-sectional thickness, and cool in the furnace to below 300℃ before unloading.

[0132] S4. Machining: When dimensional accuracy is required, turning is performed to remove the surface oxide layer and achieve the design dimensions.

[0133] S5, Conventional quenching and tempering: Heat to 860℃ for austenitization, hold at that temperature, oil quench, and then temper at 250℃ for 2 hours.

[0134] According to Example 1, during the processing of the steel segment, the comprehensive energy consumption during the processing stage is 1923 kWh / t. In the wear resistance test, the Φ25mm×10mm sample lost 0.48g of weight during wear, with a relative wear resistance index of 1.08. In the industrial test in a Φ3.6×6.0m mill, the wear loss per ton of ore was 1.08 kg / t, the flotation reagent dosage was 400g / t, and the surface hardness of the steel segment was measured to be 60.0 HRC and the 16mm depth hardness was 55.0 HRC by a Rockwell hardness tester.

[0135] Technical effects:

[0136] Table 1 shows a comparison of the technical effects of Examples 1 and 5 with Comparative Examples 1 and 2:

[0137] Table 1

[0138] Example 1 Comparative Example 1 Example 5 Comparative Example 2 Comprehensive energy consumption 1200kWh / t 1850kWh / t 1200kWh / t 1923kWh / t Wear loss 0.35g 0.52g 0.34g 0.48g Grinding per ton of ore 0.68kg / t 1.15kg / t 0.66kg / t 1.08kg / t flotation reagent dosage 320g / t 420g / t 340g / t 400g / t Surface hardness 62.3 HRC 58.0 HRC 62.0 HRC 60.0 HRC 16mm depth hardness 61.9 HRC 53.0 HRC 61.8 HRC 55.0 HRC

[0139] In summary, this invention strictly controls the chemical composition, limiting C to 1.4-1.6% and Cr to 0.8-1.5%, and uses vacuum induction melting to control the oxygen content to ≤30ppm, effectively reducing P and S impurity segregation. Regarding the manufacturing process, forging is carried out at a pressure of ≥300MPa, with a forging ratio of 3-5, combined with controlled rolling and cooling (final rolling temperature 850-950℃, cooling rate 15-20℃ / s), staged quenching, deep cryogenic treatment, and double tempering. The steel segments prepared by this invention exhibit a uniform martensitic matrix (e.g., ...). Figure 1-3 As shown, especially Figure 3 The medium-grayish-blue matrix portion, with diffusely distributed Cr 23 C6 type carbides (such as 2 and Figure 3 The medium-gray-blue matrix portion has a size of only 0.5-3μm, a volume fraction of 8-15%, an aspect ratio ≤1.5, and is uniformly distributed in an equiaxed shape without network or agglomeration defects. This is due to the purity guaranteed by vacuum melting, and the precise control of carbide fragmentation and precipitation by forging and rolling, as well as controlled rolling and cooling. Simultaneously, staged quenching, deep cryogenic treatment, and double tempering significantly refine the martensite, reduce the content of retained austenite, and enhance the stability of the microstructure. In contrast, traditional casting sections (such as...) Figure 4-5As shown, the carbides are coarse, network-like, banded, or blocky (2-12 μm in size, aspect ratio > 2), severely segregating at grain boundaries and fracturing the matrix. This not only reduces the strength-toughness balance but also accelerates failure under wear conditions due to stress concentration. The martensitic matrix has large, uneven grains and a high residual austenite content, resulting in a 5-10 HRC difference in hardness between the surface and core. The structure of the steel segment of this invention significantly improves its performance. The Rockwell hardness from the surface to a depth of 16 mm is ≥ 61 HRC, laboratory wear weight loss is reduced by 27-38%, industrial ore consumption is reduced by 18-26.5%, and impact toughness is increased by over 65%. The fine, dispersed carbides effectively hinder abrasive cutting, while the uniform martensitic matrix ensures a balance between hardness and toughness, reducing the risk of chipping and spalling. Furthermore, the rolling process reduces energy consumption by 35%, dust emissions by 60%, and metal recovery rate by 3% compared to traditional casting, combining performance advantages with environmental benefits.

Claims

1. A high-carbon chromium alloy rolled steel segment, comprising, by mass percentage, 1.4-1.6% C, 0.2-0.5% Si, 0.3-0.8% Mn, 0.8-1.5% Cr, ≤0.015% P, ≤0.010% S, with the balance being Fe and unavoidable impurities, and formed into a martensitic matrix by heat treatment, characterized in that: Cr is dispersed in the martensitic matrix 23 C6 type carbides, with a particle size of 0.5-3 μm and a volume fraction of 8-15%.

2. The ultra-high carbon chromium alloy rolled steel section according to claim 1, characterized in that: The Cr 23 C6 type carbides are uniformly distributed in an equiaxed shape with an aspect ratio ≤1.

5.

3. The ultra-high carbon chromium alloy rolled steel section according to claim 1, characterized in that: The Rockwell hardness of the steel segment is ≥61HRC from the surface to a depth of 16mm.

4. A method for preparing an ultra-high carbon chromium alloy rolled steel segment according to any one of claims 1-3, characterized in that: Includes the following steps: S1. Vacuum induction melting: Melting under vacuum conditions ≤10Pa, controlling the oxygen content of the molten steel to ≤30ppm, and the melting temperature to 1600-1650℃. S2. Forging billet: Heat the steel ingot to 1150-1200℃ and hold for 2-4 hours. Forge it with a pressure of ≥300MPa, with a forging ratio of 3-5 and a final forging temperature of ≥900℃ to obtain a billet with a cross-sectional size of 1.5-2 times that of the finished product. S3. Controlled rolling and cooling: Heat the billet to 1050-1100℃ and hold for 1-2 hours. Repeat rolling in the non-recrystallized austenite region. The final rolling temperature is 850-950℃ and the total compression ratio is ≥50%. After rolling, immediately cool to room temperature at a cooling rate of 15-20℃ / s. S4. Graded quenching: After the rolled steel section is heated to 980±10℃ for austenitization and held at that temperature, it is then quickly transferred to a salt bath at 280±10℃ and held for 60±10s, and then oil cooled to below 80℃. S5. Cryogenic treatment: The quenched steel section is held at -75±5℃ for 3±0.5h. S6. Double tempering: The first tempering temperature is 180±5℃, held for 2 hours and then air-cooled; the second tempering temperature is 150±5℃, held for 4 hours and then air-cooled.

5. The method for preparing an ultra-high carbon chromium alloy rolled steel segment according to claim 4, characterized in that: Step S4, graded quenching: The rolled steel section is heated to 980±10℃ for austenitization and then held at that temperature for 1.2-1.5 minutes per millimeter of cross-sectional thickness.

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