Steel for disc bearing of intelligent precision seeder and production method of steel

Abstract

The invention relates to steel for a disc bearing of an intelligent precision planter and a production method of the steel. The steel comprises the following chemical components in percentage by mass: 0.36-0.48% of C, 0.20-0.30% of Si, 0.40-0.60% of Mn, 0.60-1.00% of Cr, 0.10-0.25% of Mo, 0.01-0.05% of Al, less than or equal to 0.020% of P, less than or equal to 0.010% of S, less than or equal to 0.20% of Cu, 0.005-0.015% of N, less than or equal to 0.0010% of Ca, less than or equal to 0.0020% of Ti, less than or equal to 0.0010% of O and the balance of Fe and inevitable impurities. The metallographic structure of the steel is sorbite, and the grain size is greater than or equal to grade 6. The production method comprises the steps of converter primary smelting, external refining, RH vacuum degassing, continuous casting, continuous rolling, finishing, conventional heat treatment, subcritical quenching, tempering treatment and piece making and warehousing. The steel is better in strength, toughness and wear resistance and lower in production cost, and the market competitiveness of the steel product is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of special steel smelting, and specifically relates to steel for a disc bearing of an intelligent precision seed drill and a production method thereof. Background Art

[0002] "If you plant a grain of millet in spring, you will harvest ten thousand seeds in autumn." Spring plowing and sowing are the foundation for a good harvest. As agricultural mechanization is being continuously promoted, the status of the seeder is particularly important. With the advancement of science and technology, the technology of seeders is also constantly innovating and developing towards intelligence and efficiency. At present, the intelligence level of modern intelligent precision seeders has been further improved. They have advanced technologies such as AI decision support systems, remote control, and autonomous operation, realizing unmanned operation throughout the process and real-time data feedback. At the same time, as the concept of environmental protection and energy saving penetrates into product design, low-energy consumption, zero-emission electric or hybrid seeders are also the development trend of future seeders.

[0003] The ditching disc of precision seed drill is an important component of the seed drill and is the key to the performance of the seed drill. The high temperature in spring and autumn is a real test for agricultural farming. The hard soil tests the ultimate strength of all mechanical parts. The vibration and high-intensity impact that lasts throughout the entire operating season are another heavy burden on mechanical equipment. In such a working environment, the ditching disc of the seed drill needs to have a stronger load-bearing capacity. Among them, the disc bearing is limited by the harsh working conditions of the ditching disc and needs to withstand greater impact during use, which puts higher requirements on the disc bearing material of the precision seed drill. Therefore, in addition to the requirements of high strength, high hardness, and high wear resistance, the material for manufacturing such bearings must also have sufficient impact resistance.

[0004] At present, the raw materials of traditional seed drill ditching disc bearings in China are GCr15 or GCr15SiMn materials, which belong to traditional high-carbon chromium bearing steels and have a wide range of applications. However, the carbon content of this material is high, it is very brittle, and its toughness is low. It is very easy to have defects such as decarburization during the heating or heat treatment of the raw materials, which has a great impact on subsequent processing. At the same time, the traditional process of quenching and tempering heat treatment of raw materials for seed drill disc bearings used in China generally adopts complete quenching + high-temperature tempering. In the actual production process, problems such as low toughness and uneven hardness sometimes occur, and at the same time, problems such as high rework rate occur, which affects the delivery quality and cycle of the final product.

[0005] In view of the above technical difficulties, the present invention provides a precision seed drill disc bearing steel that is different from the above materials, and also proposes an optimized heat treatment method. The surface of the seed drill disc bearing obtained by this process has high hardness, high wear resistance, and high strength, while the core has good toughness, which meets the use requirements of the seed drill bearing. This technology has a short production process, low production cost, and excellent product performance. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a medium carbon bearing steel for disc bearings of intelligent precision seed drills in accordance with the above-mentioned prior art, which is produced by a continuous casting method. The medium carbon bearing steel has strong market competitiveness on the basis of meeting the quality requirements of disc bearing steels of intelligent precision seed drills.

[0007] The technical solution adopted by the present invention to solve the above-mentioned problem is: a steel for a disc bearing of an intelligent precision seed drill, the chemical composition of the steel comprising, by mass percentage, C: 0.36-0.48%, Si: 0.20-0.30%, Mn: 0.40-0.60%, Cr: 0.60-1.00%, Mo: 0.10-0.25%, Al: 0.01-0.05%, P≤0.020%, S≤0.010%, Cu≤0.20%, N: 0.005-0.015%, Ca≤0.0010%, Ti≤0.0020%, O≤0.0010%, and the remainder is Fe and unavoidable impurities.

[0008] The chemical composition design of the present invention is based on the following: 1) Determination of C content The C element is one of the most important elements that affect the hardness and strength of parts. It is also an element necessary to ensure the wear resistance of steel. Increasing the carbon content in steel will increase its martensitic transformation ability, thereby increasing its hardness and strength, and further improving wear resistance. However, too high a C content will reduce the plasticity and toughness of the steel. The steel used for the disc bearing of the intelligent precision seed drill must have both high strength and certain toughness and impact resistance. In addition, the present invention controls its content to 0.36-0.48%. The steel of the present invention belongs to the category of medium carbon steel.

[0009] 2) Determination of Si content Si is a deoxidizing element in the steelmaking process and is also a key element in the present invention. Si is solid-dissolved in the ferrite phase and has a strong solid-solution strengthening effect, which can significantly improve the strength of ferrite. Si can reduce the diffusion rate of C elements in ferrite, making it difficult for carbides precipitated during tempering to aggregate, thereby increasing the tempering stability of steel. In addition, Si can reduce the oxidation effect during frictional heating and thus improve the wear resistance of steel, but too high Si content will reduce the plasticity and toughness of ferrite. The setting range of Si content in the present invention is 0.20-0.30%.

[0010] 3) Determination of Mn content Mn is a deoxidizing and desulfurizing element in the steelmaking process. It also plays a role in solid solution strengthening of steel and improves the strength of steel. Mn can also improve the hardenability of steel and improve the hot working performance of steel. Mn can form MnS inclusions with S elements during steelmaking, making it easy to break during cutting and ensuring the processability of steel. However, if the Mn content is too high, the toughness of steel will be reduced. The Mn content of the present invention is controlled at 0.40-0.60%.

[0011] 4) Determination of Al content Al is added as a deoxidizing element in steel, which easily reacts with dissolved oxygen in molten steel to form Al with a high melting point. 2 O 3 Non-metallic inclusions such as Al and N are fully floated and removed during the smelting process, thereby improving the purity of the molten steel. At the same time, Al and N form dispersed and fine aluminum nitride inclusions to refine the grains. However, when the Al content is too high, large non-metallic inclusions are easily formed, which cannot be fully floated and remain in the molten steel, affecting the purity of the material. Therefore, the Al content of the present invention is determined to be in the range of 0.01-0.05%.

[0012] 5) Determination of Cr content Cr is a carbide-forming element that can improve the hardenability, wear resistance and corrosion resistance of steel. However, if the Cr content is too high, the impact toughness of the steel will be reduced. The Cr content of the present invention is determined to be in the range of 0.60 to 1.00%.

[0013] 6) Determination of Mo content The main function of Mo is to improve hardenability and mechanical properties of steel, especially to improve toughness, and to reduce the tough-to-brittle transition temperature of steel and inhibit the temper brittleness of steel. However, Mo is a precious metal, and excessive addition will increase manufacturing costs. The Mo content of the present invention is determined to be in the range of 0.10%-0.25%.

[0014] 7) Determination of Ca content The Ca content will increase the number and size of the point oxides in the steel. At the same time, since the point oxides have high hardness and poor plasticity, they do not deform when the steel is deformed, and are prone to form gaps at the interface, which deteriorates the performance of the steel. The range of the Ca content in the present invention is determined to be ≤0.0010%.

[0015] 8) Determination of [O] content The [O] content represents the total amount of oxide inclusions. Oxide brittle inclusions limit the service life of the finished product. A large number of tests have shown that reducing the oxygen content is significantly beneficial to improving the purity of steel, especially reducing the content of oxide brittle inclusions in steel grades. The range of the [O] content in the present invention is determined to be ≤0.0010%.

[0016] 9) Determination of Ti content Ti exists in the material in the form of TiN or Ti (C, N) type brittle inclusions, which are usually angular and more harmful to the fatigue life of the material than spherical oxides. The Ti content of the present invention shall not exceed 0.0020%.

[0017] 10) Determination of N content Because the Al element is added for deoxidation during the smelting process, a certain amount of acid-soluble aluminum will be present, and the Al element is also easy to combine with the N element to form stable AlN. The AlN precipitation temperature is relatively high, and the AlN precipitates will prevent the austenite grains from growing, thereby refining the grains. AlN is precipitated according to an atomic ratio of 1:1, that is, a weight ratio of 27:14. If the N content is too high and the Al atomic concentration is too low, it is not conducive to the precipitation of AlN. Therefore, in order to meet the grain size requirements of the steel for the disc bearing of the intelligent precision seed drill, the N content of the present invention must be controlled at 0.005-0.015%.

[0018] 11) Determination of P and S content Phosphorus causes serious segregation during solidification in steel. Phosphorus dissolves in ferrite to cause grain distortion and coarsening, and increases cold brittleness. The content of Phosphorus in the present invention is determined to be ≤0.020%. Phosphorus causes hot brittleness in steel, reduces the ductility and toughness of steel, and the content of Phosphorus in the present invention is determined to be ≤0.010%.

[0019] The production process of the steel used for the disc bearings of the above-mentioned intelligent precision seed drill is as follows: primary refining in the converter - refining outside the furnace - RH vacuum degassing - continuous casting - continuous rolling - finishing - quenching + tempering treatment - punching and warehousing.

[0020] Determination of the main inspection items and indicators of the present invention: In order to meet the requirement of a long service life of the disc bearing, the steel is required to have a high purity, so the present invention puts forward strict requirements on microscopic inclusions. Since Class B and Class D inclusions are brittle inclusions with high hardness, they will not deform under the action of stress. Therefore, during the use of the disc bearing, stress concentration is likely to occur near these brittle inclusions, thereby initiating cracks, causing the disc bearing to fail prematurely, and the larger the size of this type of inclusion, the greater the harm; since Class A and Class C inclusions are plastic inclusions with high ductility, they have less harm to the service life of the disc bearing. The present invention requires that microscopic non-metallic inclusions be inspected according to GB / T 10561 A method, and the specific requirements for the rating of microscopic non-metallic inclusions are shown in Table 1 below.

[0021] Table 1

[0022] The qualified medium carbon bearing steel produced by the present invention has fine microscopic brittle inclusions: B fine series ≤1.0 grade, B coarse series ≤0.5 grade, D fine series ≤1.0 grade, D coarse series ≤0.5 grade, DS series ≤1.0 grade, and the specific requirements are shown in Table 1 below. However, macroscopic inclusions significantly reduce the wear resistance of steel, causing serious stress concentration and easily causing early failure of bearings during use. The macroscopic defect requirements of the present invention are met by SEP 1927 water immersion high frequency flaw detection: the length of the inclusion does not exceed 5mm.

[0023] The present invention requires that the steel has a higher organizational uniformity, and therefore has strict requirements on the macrostructure. GB / T1979 is used to grade the macrostructure of the steel, meeting the following requirements: central porosity ≤1.0 level, general porosity ≤1.0 level, ingot segregation ≤1.0 level, central segregation ≤1.5 level, and shrinkage cavities, cracks and subcutaneous bubbles are not allowed.

[0024] In order to ensure the strength, toughness and impact resistance of the steel, the metallographic structure requirements of the medium carbon bearing steel product of the present invention are: after the steel is hot-rolled into bars, it is delivered by sub-temperature quenching heat treatment, that is, a heat treatment process of heating and quenching between AC1-AC3 temperatures, which can reduce the tendency of heat treatment deformation and cracking of parts and improve the comprehensive mechanical properties of the product and the qualified rate of the product. At the same time, the tensile strength of the steel in the delivery state is required to be ≥980MPa, the yield strength is ≥850MPa, the elongation after fracture is ≥12%, and the cross-sectional shrinkage is ≥55%. The austenite grain size of the bar is ≥6 grades.

[0025] Another object of the present application is to provide a method for producing the above-mentioned intelligent precision seed drill disc bearing steel, the main steps of which are as follows: (1) Molten steel smelting The smelting raw materials are sequentially subjected to molten iron pretreatment KR, converter smelting, LF refining and RH vacuum degassing to obtain pure molten steel that meets the chemical composition. Molten steel smelting must be preceded by molten iron pretreatment to obtain clean molten iron and reduce the content of harmful element P; during oxygen blowing smelting in the converter, the molten iron is converted into molten steel and the P content is further reduced, with the end point C ≥ 0.08%, P ≤ 0.025%, the quality of scrap steel is strictly controlled, the content of residual element Cu is reduced, and Cu brittleness of steel is avoided. Slag control technology is performed before tapping; the converter tapping temperature is controlled at 1620℃~1700℃ to ensure that the temperature entering the LF refining furnace is above 1500℃. Low Ti, low Ca alloys and high-quality refractory materials are added during the LF refining process to control the content of harmful elements Ti and Ca, and high-performance synthetic slag slag deoxidation technology is used. The LF refining time is controlled at more than 60 minutes to ensure that the ladle maintains a long-term inclusion removal process and allows non-metallic inclusions to fully float up; during RH vacuum degassing, the maximum vacuum degree is ≤1.33mbar, and the high vacuum time is ≥20 minutes to ensure that the furnace reaches a sufficient vacuum degree and maintains sufficient circulation processing time to remove harmful gas content in the steel. By controlling the [O] content, non-metallic inclusions are further removed to ensure the purity of the steel; (2) Continuous casting The whole process of casting is protected, and the tundish plug rod uses an argon-blown plug rod. The plug rod head must be well sealed to avoid secondary oxidation of molten steel. The tundish induction heating technology is used, the start temperature of continuous casting is ≥1500℃, and low superheat casting, superheat ≤25℃, effectively improves the macro segregation of continuous casting billets; the light reduction process combined with electromagnetic stirring technology is used to effectively improve the micro segregation of the continuous casting billet caused by high alloy content, so that the material meets high uniformity, and this technology can effectively inhibit the growth of columnar crystal area, increase the central equiaxed crystal area, and make the microstructure grains finer; the continuous casting speed is controlled at 0.40-0.55m / min, so that the continuous casting process is stable and the liquid level fluctuation is small; (3) Rolling The continuous casting billet is transferred to the heating furnace, and by controlling the residual oxygen and air-fuel ratio in the furnace, the furnace atmosphere is improved, the decarburization and burning of the billet surface are reduced, and the billet is heated and rolled into round bars. The specific rolling process is as follows: the continuous casting billet is first hoisted to the conveyor roller, and then enters the step-type heating furnace through the conveyor roller. The steel is heated to 1150℃~1200℃ in the heating furnace, and the insulation time is 4h~5h. The temperature of the continuous casting billet after leaving the furnace is 1100℃~1150℃, and the continuous casting billet is conveyed to high-pressure water for descaling through the roller. The final rolling temperature is controlled at 750-800℃. After rolling, the rolled material is slowly cooled in the pit, and the slow cooling time is ≥48h.

[0026] Finishing All products must undergo 100% non-destructive testing to ensure the surface and internal quality of the products. This includes finishing processes such as straightening and chamfering to ensure that indicators such as size and curvature meet the requirements. (5) Conventional heat treatment + sub-temperature quenching + tempering In order to ensure the mechanical properties of the steel, the steel with the above-mentioned refined quality needs to be quenched and tempered. The raw materials are first subjected to conventional heat treatment of 840±10℃×15min water quenching + 590±10℃×2h air cooling, which serves as a pretreatment for sub-temperature quenching. After pretreatment, the material is subjected to sub-temperature quenching heat treatment, 770±10℃×40min sub-temperature quenching water quenching, followed by tempering and air cooling at 550±10℃×2h. The final metallographic structure is tempered troostite + a small amount of undissolved fine-grained ferrite, thereby improving toughness.

[0027] Compared with the prior art, the advantages of the present invention are: (1) Pre-treat iron through molten iron, strictly control the quality of scrap steel, and select low-titanium alloys, deoxidizers and refractory materials; adopt slag blocking and post-furnace slag control technology to solve the problem of high content of harmful elements Ti, Ca, As, Sn, Pb and Sb in existing technologies; (2) RH vacuum cycle degassing is used to reduce the [O] and [H] contents in steel to extremely low levels, and the number and size of inclusions reach leading levels; (3) Continuous casting adopts tundish induction heating technology, the opening temperature of continuous casting is ≥1500℃, and low superheat pouring is adopted, the superheat is ≤25℃, which effectively improves the macro segregation of continuous casting billet; the continuous casting speed is controlled at 0.40-0.55m / min, so that the continuous casting process is stable and the liquid level fluctuation is small; (4) The present invention adopts a special rolling process and a special heat treatment process to ensure that the metallographic structure and mechanical properties of the product meet the design requirements.

[0028] The intelligent precision seed drill disc bearing steel produced by the present invention meets the following index requirements: The main technical indicators of the steel described in the present invention are as follows: After the steel is hot-rolled into a bar, the metallographic structure is in a sorbite state. The tensile strength of the steel in the delivery state is ≥980MPa, the yield strength is ≥850MPa, the elongation after fracture is ≥12%, and the cross-sectional shrinkage is ≥55%. The austenite grain size of the bar is ≥6. The non-metallic inclusions of the steel are tested according to the GB / T 10561 A method, wherein the brittle non-deformable inclusions B fine ≤1.0 grade, B coarse ≤0.5 grade, D fine ≤1.0 grade, D coarse ≤0.5 grade, and Ds ≤1.0 grade. The SEP1927 water immersion high-frequency flaw detection meets the following requirements: the length of the inclusion does not exceed 5mm. The GB / T 1979 is used to grade the macrostructure of the steel to meet the following requirements: central porosity ≤1.0 grade, general porosity ≤1.0 grade, ingot segregation ≤1.0 grade, and central segregation ≤1.5 grade. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an enlarged view of the typical metallographic structure (200×) of the final product (after conventional heat treatment + sub-temperature quenching + tempering) in the embodiment of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described in more detail in conjunction with the preferred embodiments of the present invention. However, these embodiments are only descriptions of the preferred implementation methods of the present invention and cannot impose any limitation on the scope of the present invention.

[0031] The manufacturing process of the steel for the disc bearing of the intelligent precision seed drill in the embodiment of the present invention is the process of producing steel by converter primary refining - refining outside the furnace - RH vacuum degassing - continuous casting - continuous rolling - finishing - quenching + tempering treatment - punching and warehousing. The specification of the continuous casting billet is 350mm×400mm, the specification of the finished steel is φ50mm-Φ120mm, and the compression ratio is ≥12.

[0032] Specifically, high-quality molten iron, scrap steel and raw and auxiliary materials are selected during smelting, and high-quality deoxidizers and refractory materials are selected. In the converter production process, the tapping end point C of the three embodiments is controlled at 0.08-0.12% respectively, the end point P is controlled at ≤0.025%, the tapping temperature is 1620℃-1700℃, Al iron is added during the tapping process for pre-deoxidation, slag removal is performed after tapping, and synthetic slag is added again, the superheat of the continuous casting tundish is controlled within ≤25℃, and the continuous casting speed is controlled at 0.40-0.55m / min. The above-mentioned continuous casting billet is sent to a heating furnace for heating and rolling into a product. The steel needs to be slowly cooled in the pit. After slow cooling for ≥48 hours, the steel is finished after being discharged from the pit, and then conventional heat treatment + sub-temperature quenching + tempering heat treatment is performed. Conventional heat treatment is 840±10℃×15min water quenching + 590±10℃×2h air cooling. After pretreatment, the material is subjected to sub-temperature quenching heat treatment, 770±10℃×40min sub-temperature quenching water quenching, and then tempering and air cooling at 550±10℃×2h.

[0033] The chemical compositions (wt %) of the various embodiments of the present invention are shown in Table 2.

[0034] Table 2

[0035] Table 2 (continued)

[0036] Table 3 Non-metallic inclusion detection results of various examples and comparative steels

[0037] From the detection of non-metallic inclusions, the present invention has better indicators and no large defect inclusions are found.

[0038] Table 4 Grain size, hardness and mechanical properties data of each embodiment

[0039] From the perspective of mechanical properties, the mechanical properties of the invention meet the requirements.

[0040] Table 5 Macro data of steel materials in various examples

[0041] From the low-magnification inspection, the low-magnification quality of the present invention is better.

[0042] Figure 1 This is a typical metallographic structure diagram of an embodiment of the present invention after conventional heat treatment + sub-temperature quenching + tempering. The metallographic structure of the embodiment in the sub-temperature quenching state is tempered troostite + a small amount of undissolved fine-grained ferrite.

[0043] The steel for the disc bearing of the intelligent precision seed drill in each embodiment of the present invention has the following advantages: 1. The vacuum degassing + continuous casting process is adopted, and the indicators of harmful elements [O], Ti, etc. are good.

[0044] 2. From the non-metallic inclusions and low-power inspection results, due to the careful selection of smelting raw and auxiliary materials and the optimization of smelting processing technology in the present invention, the non-metallic inclusion indicators are excellent; 3. From the comparison results of mechanical properties, since the structure of the present invention is more fine and uniform, the tensile and other mechanical properties meet the requirements, which is more conducive to improving the service life of the final disc bearing.

[0045] In summary, the present invention relates to an intelligent precision seed drill disc bearing steel and a production method thereof, which adopts a high-efficiency process route of vacuum degassing, continuous casting, and rolling, and optimizes and controls the key processes, so that the steel obtains high purity and high structural uniformity, and is more competitive in production efficiency, production cost, and product quality stability.

[0046] Although the preferred embodiments of the present invention are described in detail above, it should be clearly understood that various modifications and variations are possible for those skilled in the art. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A steel for disc bearing of intelligent precision seed drill, characterized by: The chemical composition of the steel is, by mass percentage, C: 0.36-0.48%, Si: 0.20-0.30%, Mn: 0.40-0.60%, Cr: 0.60-1.00%, Mo: 0.10-0.25%, Al: 0.01-0.05%, P≤0.020%, S≤0.010%, Cu≤0.20%, N: 0.005-0.015%, Ca≤0.0010%, Ti≤0.0020%, O≤0.0010%, and the balance is Fe and unavoidable impurities.

2. The steel for disc bearing of an intelligent precision seed drill according to claim 1 is characterized by: After the steel is hot-rolled into bars, it is delivered after quenching + tempering heat treatment, and the metallographic structure is in the sorbite state.

3. The steel for disc bearing of an intelligent precision seed drill according to claim 1 is characterized by: The tensile strength of the steel in the delivery state is ≥980MPa, the yield strength is ≥850MPa, the elongation after fracture is ≥12%, the section reduction rate is ≥55%, and the austenite grain size is ≥6 grades.

4. The steel for disc bearing of an intelligent precision seed drill according to claim 1 is characterized by: The non-metallic inclusions in steel are tested according to GB / T 10561 A method, among which the brittle non-deformable inclusions are B fine ≤ 1.0, B coarse ≤ 0.5, D fine ≤ 1.0, D coarse ≤ 0.5, Ds ≤ 1.0, and the SEP 1927 water immersion high frequency flaw detection meets the following requirements: the length of the inclusions does not exceed 5mm. The macrostructure rating of steel according to GB / T 1979 meets the following requirements: central porosity ≤ 1.0, general porosity ≤ 1.0, ingot segregation ≤ 1.0, and central segregation ≤ 1.

5.

5. A method for producing steel for disc bearings of intelligent precision seed drills as claimed in claim 1, characterized in that: The method comprises the following steps: (1) Molten steel smelting The smelting raw materials are sequentially subjected to molten iron pretreatment KR, converter smelting, LF refining and RH vacuum degassing to obtain pure molten steel with chemical composition; (2) Continuous casting The whole process of casting is protected, and the tundish plug rod uses argon blowing plug rod to avoid secondary oxidation of molten steel; the tundish induction heating technology is adopted, the opening temperature of continuous casting is ≥1500℃, and low superheat casting is performed, and the superheat is ≤25℃; the light pressure reduction process combined with electromagnetic stirring technology is used to effectively inhibit the growth of columnar crystal area, increase the central equiaxed crystal area, make the structure grains finer, and the continuous casting speed is controlled at 0.40-0.55m / min; (3) Rolling The continuous casting billet is first hoisted to the conveyor roller, and then enters the walking beam heating furnace through the conveyor roller. The steel is heated to 1150℃~1200℃ in the heating furnace, and the holding time is 4h~5h. The temperature of the continuous casting billet after leaving the furnace is 1100℃~1150℃. The continuous casting billet is conveyed to the high-pressure water descaling through the roller, and the final rolling temperature is controlled at 750-800℃. After rolling is completed, the rolled material is slowly cooled in the pit, and the slow cooling time is ≥48h; Finishing All products undergo non-destructive testing to ensure the surface and internal quality of the products; (5) Conventional heat treatment + sub-temperature quenching + tempering First, the raw materials are subjected to conventional heat treatment at 840±10℃×15min; water quenching +590±10℃×2h; air cooling as a pretreatment for sub-temperature quenching. After pretreatment, the material is subjected to sub-temperature quenching heat treatment, sub-temperature quenching and water quenching at 770±10℃×40min, followed by tempering and air cooling at 550±10℃×2h. The final metallographic structure is tempered troostite + a small amount of undissolved fine-grained ferrite.

6. The method for producing steel for disc bearings of intelligent precision seed drills according to claim 5, characterized in that: In step 1), when oxygen blowing smelting is carried out in the converter, molten iron is converted into molten steel and the P content is further reduced, the end point C ≥ 0.08%, P ≤ 0.025%, the quality of scrap steel is controlled, the content of residual element Cu is reduced, Cu brittleness of steel is avoided, and slag control process is carried out before tapping; the tapping temperature of the converter is controlled at 1620℃~1700℃ to ensure that the temperature entering the LF refining furnace is above 1500℃.

7. The method for producing steel for disc bearings of intelligent precision seed drills according to claim 5, characterized in that: In step 1), low Ti, low Ca alloy and high-quality refractory materials are added during the LF refining process to control the content of harmful elements Ti and Ca. The LF refining time is controlled at more than 60 minutes to ensure that the ladle maintains a long inclusion removal process and allows non-metallic inclusions to float fully.

8. The method for producing steel for disc bearings of intelligent precision seed drills according to claim 5, characterized in that: In step 1), during RH vacuum degassing, the maximum vacuum degree is ≤1.33mbar, and the high vacuum time is ≥20min, ensuring that the furnace reaches a sufficient vacuum degree and maintains sufficient circulation processing time to remove harmful gas content in the steel. By controlling the oxygen content, non-metallic inclusions are further removed to ensure the purity of the steel.

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