A rolling process for improving the surface quality of c70s6 non-adjusted steel

Abstract

The application relates to the technical field of steel metallurgy, and discloses a rolling process for improving the surface quality of C70S6 non-adjustable steel, which comprises the following steps: S1, a heating process; S2, a descaling process; S3, a rolling process; S4, a cooling process; and S5, a finishing process.The process can significantly reduce thermal stress cracks, the temperature uniformity of the casting blank from the surface to the core is improved through a three-stage heating mode and precise heat preservation control, the thermal stress is effectively released, the anti-collision and spacing control during charging are combined, local overheating or overcooling is avoided, the occurrence rate of surface micro-cracks and corner transverse cracks is reduced by more than 80%, and the surface integrity of the casting blank is greatly improved.The process can completely solve the iron oxide scale defects, the double high-pressure water descaling process after the furnace and before the medium rolling is adopted, the optimized combination of the descaling pressure and the water flow speed ensures that the residual area of the iron oxide scale is less than or equal to 3%, the iron oxide scale pressing-in defects are completely eliminated, and the surface cleanliness of the steel is significantly improved, thereby providing a high-quality base for subsequent processing.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a rolling process for improving the surface quality of C70S6 non-quenched steel. Background Technology

[0002] C70S6 non-adjustable steel, as the core material for fracture-resistant connecting rods, must meet stringent requirements such as high strength, low toughness, easy machinability, and brittle fracture during expansion. Its surface quality directly affects the machining accuracy and reliability of the connecting rod. Currently, the industry faces multiple surface quality challenges in the rolling production of this steel grade: during the billet heating stage, uneven temperature gradients and insufficient holding time can easily generate thermal stress, leading to micro-cracks on the surface and transverse cracks at the corners; if the iron oxide scale generated during heating is not completely removed, it can easily be pressed into the billet surface during rolling, forming inclusion-like defects; during the rolling stage, unreasonable reduction distribution and large temperature control fluctuations can lead to deviations in steel dimensional accuracy, scratches, or secondary oxidation defects on the surface; during the cooling process, excessively fast or uneven cooling rates can easily generate thermal stress cracks, and improper stacking timing can easily cause surface corrosion; and incomplete detection and treatment of minor defects in the finishing process can lead to residual cracks and oxide layers on the finished product surface. These defects not only reduce the product yield, but also affect the subsequent fracture processing performance, leading to problems such as slag shedding and uneven fracture surfaces when the connecting rod is fractured, which restricts the stable application of this steel grade in the field of high-end automotive parts. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a rolling process for improving the surface quality of C70S6 non-heat-treated steel, which has advantages such as a significant reduction in thermal stress cracks and solves the problems of surface micro-cracks and corner transverse cracks.

[0004] (II) Technical Solution To achieve the goal of significantly reducing thermal stress cracks, the present invention provides the following technical solution: a rolling process for improving the surface quality of C70S6 non-heat-treated steel, including an S1 heating process, an S2 descaling process, an S3 rolling process, an S4 cooling process, and an S5 finishing process. The S1 heating process includes an S101 heating curve, an S102 holding time, an S103 furnace gas control, and an S104 furnace loading requirements. The S2 descaling process includes S201 primary descaling (after the furnace), S202 secondary descaling (before intermediate rolling), and S203 verification of the descaling effect. The S3 rolling process includes the S301 roughing stage, the S302 intermediate rolling stage, the S303 finishing rolling stage, and the S304 roll management. The S4 cooling process includes S401 cooling bed cooling, S402 segmented cooling, S403 final cooling temperature, and S404 slow cooling supplementation. The S5 finishing process includes S501 peeling, S502 flaw detection, S503 grinding and cleaning, and S504 end treatment.

[0005] Preferably, the S101 heating curve adopts a "three-stage heating" mode, with the preheating stage temperature controlled at 850-950℃, the heating stage temperature at 1050-1150℃, and the soaking stage temperature at 1150-1200℃, to ensure uniform temperature of the billet from the surface to the core.

[0006] Preferably, the holding time of S102 is adjusted according to the cross-sectional size of the billet. For billets with a cross-section of 200-300mm, the total time in the furnace is controlled to be 250-400 minutes, of which the holding time in the soaking section accounts for no less than 40%, to ensure uniform growth of austenite grains.

[0007] Preferably, the S103 furnace gas control maintains the residual oxygen content of the furnace gas at 0.3%-3.0%, reducing oxidation loss on the surface of the cast billet, with the oxidation loss controlled to ≤0.5%. S104 Furnace Loading Requirements: Avoid collisions when loading billets into the furnace. The spacing between billets in the furnace should be ≥50mm to ensure uniform heating and prevent local overheating or undercooling.

[0008] Preferably, the S201 primary descaling (after furnace) adopts a high-pressure water descaling system, with the descaling pressure controlled at 25-30MPa and the water flow velocity ≥80m / s, to ensure full coverage of the billet surface and remove the primary iron oxide scale generated during the heating process; S202 Secondary Descaling (Before Intermediate Rolling): A secondary descaling device is installed before intermediate rolling, with a pressure of 20-25MPa, to perform secondary cleaning of newly formed iron oxide scale after rough rolling, so as to prevent it from being pressed into the surface during subsequent rolling. S203 Descaling Effect Verification: After descaling, the surface of the billet was inspected online, and the residual area of ​​iron oxide scale was ≤3%, with no obvious accumulation or omission of iron oxide scale.

[0009] Preferably, in the S301 roughing stage: the initial rolling temperature is 1050-1100℃, a large reduction process is adopted, the single-pass reduction rate is 30%-40%, and the cumulative reduction rate is ≥60%, which breaks down coarse grains and improves the uniformity of the structure; during the rolling process, slippage between the billet surface and the rolls is avoided to prevent scratches. S302 intermediate rolling stage: rolling temperature 980-1050℃, medium reduction, single pass reduction rate 20%-30%, control rolling rhythm, interval time between each pass ≤3 seconds, reduce surface secondary oxidation time; S303 finishing rolling stage: initial rolling temperature 900-980℃, finishing mill adopts controlled rolling and controlled cooling technology, final rolling temperature 800-850℃; dimensional tolerances are controlled by positive tolerances, large face +0.10-+0.70mm, small face +0.05-+0.30mm, out-of-roundness ≤0.50mm.

[0010] Preferably, the S304 roll management involves: inspecting the roll surface before rolling to ensure there are no cracks or steel sticking defects, controlling the roll surface roughness to 0.8-1.5μm, and performing online grinding and cleaning on the rolls once every 200 tons of steel billet rolled during the rolling process.

[0011] Preferably, the S401 cooling bed cooling: the rolled steel billet is cooled by a walking cooling bed, and the cooling rate of the cooling bed is controlled at 5-15℃ / min to avoid uneven local cooling rate; the steel billets are evenly distributed on the cooling bed with a spacing of ≥100mm to prevent them from colliding and scratching each other; S402 segmented cooling: After finishing rolling, water cooling pretreatment can be used as needed. The water cooling time is 3-8 seconds. After cooling, the surface temperature of the billet is controlled at 750-850℃. Then it enters the cooling bed for natural cooling, which refines the grains and reduces surface oxidation. S403 final cooling temperature: The billet is cooled to ≤300℃ on the cooling bed before being stacked. Moisture-proof pads are used for isolation during stacking to prevent moisture from causing surface corrosion. S404 Slow Cooling Supplement: For steel billets with larger cross sections (≥280mm), slow cooling treatment is carried out after stacking. The slow cooling time is ≥24h, and the ambient temperature of the slow cooling environment is not lower than 50℃ to reduce surface cracks caused by internal stress.

[0012] Preferably, the S501 peeling process is performed by using a centerless peeling machine, with the peeling amount on one side controlled at 0.3-0.8mm, to completely remove the surface oxide layer and microcrack defects generated during the rolling process; S502 Flaw Detection: After peeling, a "dual flaw detection" inspection is carried out, using a combination of magnetic flux leakage testing and ultrasonic testing, which meets the national standard Class A flaw detection standard, with a detection coverage of 100%. Surface and near-surface defects are marked immediately.

[0013] Preferably, the S503 grinding and cleaning process involves: grinding defects discovered during flaw detection using a grinding wheel, with a grinding depth ≥ defect depth + 0.2mm, resulting in a smooth surface transition without sharp edges; after grinding, a local flaw detection is performed again to ensure that the defects are completely removed. S504 end treatment: Use a grinding wheel to cut to length, and then chamfer the ends with a chamfer radius of 3-8mm to avoid surface scratches caused by end burrs and flash.

[0014] (III) Beneficial Effects Compared with the prior art, the present invention provides a rolling process for improving the surface quality of C70S6 non-quenched steel, which has the following beneficial effects: 1. The rolling process for improving the surface quality of C70S6 non-heat-treated steel significantly reduces thermal stress cracks: through a three-stage heating mode and precise heat preservation control, the temperature uniformity of the billet from the surface to the core is improved, and thermal stress is effectively released. Combined with anti-collision and spacing control during furnace loading, local overheating or undercooling is avoided, reducing the incidence of surface micro-cracks and corner transverse cracks by more than 80%, and greatly improving the surface integrity of the billet.

[0015] 2. The rolling process for improving the surface quality of C70S6 non-adjusted steel completely solves the iron oxide scale defect: the dual high-pressure water descaling process after the furnace and before the intermediate rolling is adopted. The optimized combination of descaling pressure and water flow rate ensures that the residual area of ​​iron oxide scale is ≤3%, completely eliminating the defect of iron oxide scale pressing in. The surface cleanliness of the steel is significantly improved, providing a high-quality base for subsequent processing.

[0016] 3. This rolling process improves the surface quality of C70S6 non-adjustable steel. This process achieves improved dimensional accuracy and microstructure uniformity: the large reduction rate in rough rolling breaks down coarse grains; precise temperature and rhythm control in intermediate rolling reduces secondary oxidation; and controlled rolling and cooling technology and refined roll management in finish rolling ensure that the dimensional tolerances of the steel are strictly controlled within the set range, with out-of-roundness ≤0.50mm, austenite grain size stabilized at level 7-9, avoiding mixed grain structure, and significantly enhancing the consistency of mechanical properties and processing performance.

[0017] 4. The rolling process for improving the surface quality of C70S6 non-cooled steel achieves effective control of cooling and corrosion defects: the stable cooling and segmented cooling process of the walking beam cooling bed ensures that the cooling rate is uniformly controlled at 5-15℃ / min, reducing the generation of thermal stress cracks; after the final cooling temperature is ≤300℃, the billets are stacked and moisture-proof isolation is adopted to completely avoid surface corrosion caused by moisture; the supplementary slow cooling of larger cross-section billets further reduces the risk of internal stress.

[0018] 5. The rolling process for improving the surface quality of C70S6 non-adjustable steel achieves a 100% surface defect detection and removal rate: centerless peeling removes the surface oxide layer and microcracks, and the combined magnetic flux leakage and ultrasonic dual flaw detection achieves full coverage of surface and near-surface defects. Combined with targeted grinding and secondary flaw detection, it ensures that the surface of the finished steel is free of cracks, scratches, and residual defects, fully meeting the national standard A-level flaw detection standard and satisfying the stringent processing and use requirements of the fracture-resistant connecting rod. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] This solution provides a technical approach, specifically a rolling process for improving the surface quality of C70S6 non-heat-treated steel, comprising the following steps: S1 heating process: Core objective: This achieves uniform heating of the billet, reduces thermal stress, lowers the risk of surface cracks, and lays the foundation for subsequent rolling. Key points of operation: S101 heating curve: The "three-stage heating" mode is adopted, with the preheating stage temperature controlled at 850-950℃, the heating stage temperature at 1050-1150℃, and the soaking stage temperature at 1150-1200℃, to ensure uniform temperature of the billet from the surface to the core. S102 holding time: Adjusted according to the cross-sectional size of the billet. For billets with a cross-section of 200-300mm, the total time in the furnace should be controlled at 250-400 minutes, of which the holding time in the soaking section should account for no less than 40% to ensure uniform growth of austenite grains. S103 Furnace Gas Control: The residual oxygen content of the furnace gas is maintained at 0.3%-3.0% to reduce oxidation loss on the surface of the cast billet, with the oxidation loss controlled at ≤0.5%; S104 Furnace Loading Requirements: Avoid collisions when loading billets into the furnace. The spacing between billets in the furnace should be ≥50mm to ensure uniform heating and prevent local overheating or undercooling. S2 descaling process: Core objective: Thoroughly remove the iron oxide scale from the surface of the billet to prevent the iron oxide scale from being pressed into the surface of the billet and forming defects; Key points of operation: S201 Primary Descaling (After Furnace): A high-pressure water descaling system is adopted, with the descaling pressure controlled at 25-30MPa and the water flow velocity ≥80m / s, to ensure full coverage of the billet surface and remove the primary iron oxide scale generated during the heating process. S202 Secondary Descaling (Before Intermediate Rolling): A secondary descaling device is installed before intermediate rolling, with a pressure of 20-25MPa, to perform secondary cleaning of newly formed iron oxide scale after rough rolling, so as to prevent it from being pressed into the surface during subsequent rolling. S203 Descaling Effect Verification: After descaling, the surface of the billet was inspected online, and the residual area of ​​iron oxide scale was ≤3%, with no obvious iron oxide scale accumulation or omission areas. S3 rolling process: Core objective: Controlling rolling temperature, reduction amount, and rhythm reduces surface oxidation and crack formation, ensuring dimensional accuracy; Key points of operation: S301 roughing stage: initial rolling temperature 1050-1100℃, using a large reduction process, single-pass reduction rate 30%-40%, cumulative reduction rate ≥60%, breaking up coarse grains and improving the uniformity of the structure; during the rolling process, avoid slippage between the billet surface and the rolls to prevent scratches; S302 intermediate rolling stage: rolling temperature 980-1050℃, medium reduction, single pass reduction rate 20%-30%, control rolling rhythm, interval time between each pass ≤3 seconds, reduce surface secondary oxidation time; S303 finishing rolling stage: initial rolling temperature 900-980℃, finishing mill adopts controlled rolling and controlled cooling technology, final rolling temperature 800-850℃; dimensional tolerances are controlled by positive tolerances, large face +0.10-+0.70mm, small face +0.05-+0.30mm, out-of-roundness ≤0.50mm; S304 Roll Management: Before rolling, inspect the roll surface to ensure there are no cracks or steel sticking defects. The surface roughness of the roll is controlled at 0.8-1.5μm. During the rolling process, the roll is cleaned and polished online once every 200 tons of steel billet rolled. S4 Cooling Process: Core objective: Smoothly control the cooling rate to avoid thermal stress cracks caused by rapid cooling and ensure stable surface quality; Key points of operation: S401 Cooling Bed: After rolling, the steel billet is cooled by a walking bed. The cooling rate of the cooling bed is controlled at 5-15℃ / min to avoid uneven local cooling. The steel billet is evenly distributed on the cooling bed with a spacing of ≥100mm to prevent mutual collision and scratches. S402 segmented cooling: After finishing rolling, water cooling pretreatment can be used as needed. The water cooling time is 3-8 seconds. After cooling, the surface temperature of the billet is controlled at 750-850℃. Then it enters the cooling bed for natural cooling, which refines the grains and reduces surface oxidation. S403 final cooling temperature: The billet is cooled to ≤300℃ on the cooling bed before being stacked. Moisture-proof pads are used for isolation during stacking to prevent moisture from causing surface corrosion. S404 slow cooling supplement: For steel billets with larger cross sections (≥280mm), slow cooling treatment is carried out after stacking. The slow cooling time is ≥24h and the ambient temperature of the slow cooling environment is not lower than 50℃ to reduce surface cracks caused by internal stress. S5 finishing process: Core objective: Remove surface defects to ensure that the finished steel surface is free of cracks, iron oxide scale, and scratches, meeting delivery requirements; Key points of operation: S501 peeling process: A centerless peeling machine is used for peeling, and the peeling amount on one side is controlled at 0.3-0.8mm to completely remove the surface oxide layer and micro-crack defects generated during the rolling process; S502 Flaw Detection: After peeling, a "dual flaw detection" inspection is carried out, using a combination of magnetic flux leakage flaw detection and ultrasonic flaw detection, which meets the national standard Class A flaw detection standard, with a detection coverage of 100%. Surface and near-surface defects are marked immediately. S503 Grinding and Cleaning: For defects found during flaw detection, use a grinding wheel to grind them to a depth ≥ defect depth + 0.2mm. After grinding, the surface should be smooth and free of sharp edges. After grinding, perform local flaw detection again to ensure that the defects are completely removed. S504 end treatment: Use a grinding wheel to cut to length, and then chamfer the ends with a chamfer radius of 3-8mm to avoid surface scratches caused by end burrs and flash; Furthermore, this process significantly reduces thermal stress cracks: through a three-stage heating mode and precise heat preservation control, the temperature uniformity of the billet from the surface to the core is improved, thermal stress is effectively released, and combined with anti-collision and spacing control during furnace loading, local overheating or undercooling is avoided, reducing the incidence of surface micro-cracks and corner transverse cracks by more than 80%, and greatly improving the surface integrity of the billet. Furthermore, this process completely solves the problem of iron oxide scale defects: it adopts a dual high-pressure water descaling process after the furnace and before the intermediate rolling, and the optimized combination of descaling pressure and water flow rate ensures that the residual area of ​​iron oxide scale is ≤3%, completely eliminating the defect of iron oxide scale pressing in, and significantly improving the cleanliness of the steel surface, providing a high-quality base for subsequent processing. Furthermore, this process achieves improved dimensional accuracy and microstructure uniformity: the large reduction rate in rough rolling breaks down coarse grains, precise temperature and rhythm control in intermediate rolling reduces secondary oxidation, and the controlled rolling and cooling technology and refined roll management in finishing rolling ensure that the dimensional tolerances of the steel are strictly controlled within the set range, with out-of-roundness ≤0.50mm, austenite grain size stabilized at level 7-9, avoiding mixed grain structure, and significantly enhancing the consistency of mechanical properties and processing performance; Furthermore, this process achieves effective control of cooling and corrosion defects: the stable cooling and segmented cooling process of the walking bed ensures that the cooling rate is uniformly controlled at 5-15℃ / min, reducing the generation of thermal stress cracks; after the final cooling temperature is ≤300℃, the billets are stacked and moisture-proof isolation is adopted to completely avoid surface corrosion caused by moisture; the supplementary slow cooling of large cross-section billets further reduces the risk of internal stress. Furthermore, this process achieves a 100% surface defect detection and removal rate: coreless peeling removes the surface oxide layer and microcracks, and the combined magnetic flux leakage and ultrasonic dual flaw detection achieves full coverage of surface and near-surface defects. Combined with targeted grinding and secondary flaw detection, it ensures that the surface of the finished steel is free of cracks, scratches, and residual defects, fully complying with the national standard Class A flaw detection standard and meeting the stringent processing and usage requirements of the fracture-resistant connecting rod.

[0021] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A rolling process for improving the surface quality of C70S6 non-heat-treated steel, comprising an S1 heating process, an S2 descaling process, an S3 rolling process, an S4 cooling process, and an S5 finishing process, characterized in that: The S1 heating process includes S101 heating curve, S102 heat preservation time, S103 furnace gas control, and S104 furnace loading requirements. The S2 descaling process includes S201 primary descaling (after the furnace), S202 secondary descaling (before intermediate rolling), and S203 verification of the descaling effect. The S3 rolling process includes the S301 roughing stage, the S302 intermediate rolling stage, the S303 finishing rolling stage, and the S304 roll management. Among them, the S4 cooling process includes S401 cooling bed cooling, S402 segmented cooling, S403 final cooling temperature and S404 slow cooling supplement; The S5 finishing process includes S501 peeling, S502 flaw detection, S503 grinding and cleaning, and S504 end treatment.

2. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S101 heating curve adopts a "three-stage heating" mode, with the preheating stage temperature controlled at 850-950℃, the heating stage temperature at 1050-1150℃, and the soaking stage temperature at 1150-1200℃, to ensure uniform temperature of the billet from the surface to the core.

3. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The holding time of S102 is adjusted according to the cross-sectional size of the billet. For billets with a cross-section of 200-300mm, the total time in the furnace is controlled to be 250-400 minutes, of which the holding time in the soaking section accounts for no less than 40%, to ensure uniform growth of austenite grains.

4. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S103 furnace gas control: the residual oxygen content of the furnace gas is maintained at 0.3%-3.0% to reduce oxidation loss on the surface of the cast billet, and the amount of oxidation loss is controlled to ≤0.5%; S104 Furnace Loading Requirements: Avoid collisions when loading billets into the furnace. The spacing between billets in the furnace should be ≥50mm to ensure uniform heating and prevent local overheating or undercooling.

5. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S201 primary descaling (after furnace): adopts a high-pressure water descaling system, with descaling pressure controlled at 25-30MPa and water flow velocity ≥80m / s, to ensure full coverage of the billet surface and remove primary iron oxide scale generated during heating. S202 Secondary Descaling (Before Intermediate Rolling): A secondary descaling device is installed before intermediate rolling, with a pressure of 20-25MPa, to perform secondary cleaning of newly formed iron oxide scale after rough rolling, so as to prevent it from being pressed into the surface during subsequent rolling. S203 Descaling Effect Verification: After descaling, the surface of the billet was inspected online, and the residual area of ​​iron oxide scale was ≤3%, with no obvious accumulation or omission of iron oxide scale.

6. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S301 roughing stage: the initial rolling temperature is 1050-1100℃, a large reduction process is adopted, the single-pass reduction rate is 30%-40%, the cumulative reduction rate is ≥60%, the coarse grains are broken up, and the uniformity of the structure is improved; during the rolling process, the surface of the billet is prevented from slipping on the rolls to prevent scratches. S302 intermediate rolling stage: rolling temperature 980-1050℃, medium reduction, single pass reduction rate 20%-30%, control rolling rhythm, interval time between each pass ≤3 seconds, reduce surface secondary oxidation time; S303 finishing rolling stage: initial rolling temperature 900-980℃, finishing mill adopts controlled rolling and controlled cooling technology, final rolling temperature 800-850℃; dimensional tolerances are controlled by positive tolerances, large face +0.10-+0.70mm, small face +0.05-+0.30mm, out-of-roundness ≤0.50mm.

7. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S304 roll management includes: inspecting the roll surface before rolling to ensure there are no cracks or steel sticking defects, controlling the roll surface roughness to 0.8-1.5μm, and performing online grinding and cleaning on the rolls every 200 tons of steel billet rolled during the rolling process.

8. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S401 cooling bed cooling: The rolled steel billet is cooled by a walking cooling bed, and the cooling rate of the cooling bed is controlled at 5-15℃ / min to avoid uneven local cooling rate; the steel billet is evenly distributed on the cooling bed with a spacing of ≥100mm to prevent mutual collision and scratches. S402 segmented cooling: After finishing rolling, water cooling pretreatment can be used as needed. The water cooling time is 3-8 seconds. After cooling, the surface temperature of the billet is controlled at 750-850℃. Then it enters the cooling bed for natural cooling, which refines the grains and reduces surface oxidation. S403 final cooling temperature: The billet is cooled to ≤300℃ on the cooling bed before being stacked. Moisture-proof pads are used for isolation during stacking to prevent moisture from causing surface corrosion. S404 slow cooling supplement: For steel billets with larger cross sections (≥280mm), slow cooling treatment is carried out after stacking. The slow cooling time is ≥24h, and the ambient temperature of the slow cooling environment is not lower than 50℃ to reduce surface cracks caused by internal stress.

9. The rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S501 peeling process: a centerless peeling machine is used for peeling, and the peeling amount on one side is controlled at 0.3-0.8mm to completely remove the surface oxide layer and micro-crack defects generated during the rolling process; S502 Flaw Detection: After peeling, a "dual flaw detection" inspection is carried out, using a combination of magnetic flux leakage testing and ultrasonic testing, which meets the national standard Class A flaw detection standard, with a detection coverage of 100%. Surface and near-surface defects are marked immediately.

10. A rolling process for improving the surface quality of C70S6 non-quenched steel according to claim 1, characterized in that: The S503 grinding and cleaning process involves grinding defects discovered during flaw detection using a grinding wheel. The grinding depth is ≥ defect depth + 0.2mm, resulting in a smooth surface transition without sharp edges. After grinding, a local flaw detection is performed again to ensure that the defects are completely removed. S504 end treatment: Use a grinding wheel to cut to length, and then chamfer the ends with a chamfer radius of 3-8mm to avoid surface scratches caused by end burrs and flash.