Rolling method for improving hardness of washing machine shaft steel

Abstract

The invention discloses a rolling method for improving hardness of steel for a washing machine shaft, and relates to the technical field of metal processing, and the rolling method comprises the following specific steps: firstly, cleaning 45 steel blanks, carrying out multi-stage heating and heat preservation, carrying out rough rolling after high-pressure water descaling, then carrying out temperature-controlled finish rolling, and carrying out water-through cooling through a water tank to control the temperature; after finish rolling, self-tempering is conducted on a cooling bed with a heat preservation cover, cooling is conducted to the room temperature, straightening is conducted, oxide skin is removed, finally segmented machining and detection are conducted, and it is guaranteed that the hardness, the tensile property, the size precision and the surface quality reach the standard; according to the method, the steel hardness is remarkably improved by accurately controlling multiple key links of blank pretreatment and heating, water penetration before rough rolling and controlled rolling and finish rolling and finish rolling temperature control, the uniformity of the internal structure of the blank is ensured through multi-stage heating and heat preservation treatment, and a good foundation is laid for follow-up rolling; the water penetration process before rough rolling and controlled rolling effectively reduces the temperature of the center part of the intermediate blank, and coarse grains are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, in particular to a rolling method for increasing the hardness of steel for a washing machine shaft. Background Art

[0002] In the modern home appliance manufacturing industry, washing machines are one of the important home appliances. The performance of their core components, such as shaft steel, directly affects the service life, stability and operating efficiency of washing machines. As the home appliance industry continues to increase its requirements for product quality and performance, washing machine shaft steel needs to have higher hardness, strength and wear resistance to meet the needs of long-term high-load operation. Traditional rolling processes often find it difficult to balance the improvement of steel hardness with the control of surface quality and dimensional accuracy when producing washing machine shaft steel, resulting in unstable product performance and difficulty in meeting the needs of the high-end market. Therefore, developing a rolling method that can significantly improve the hardness of washing machine shaft steel while ensuring surface quality and dimensional accuracy has become a technical problem that needs to be urgently solved in the home appliance manufacturing industry.

[0003] Traditional steel rolling technology for washing machine shafts usually adopts a single heating and rolling process, which makes it difficult to accurately control the temperature changes and structural evolution of the steel during the rolling process, resulting in limited improvement in the hardness of the steel, and it is difficult to ensure the surface quality and dimensional accuracy. Especially in the rough rolling and finishing rolling stages, due to the lack of effective temperature control and water cooling process, the internal structure of the steel is prone to unevenness and coarse grains, which in turn affects the hardness and mechanical properties of the steel. In addition, traditional technology also has shortcomings in straightening and surface treatment, and it is difficult to meet the strict requirements of washing machine shafts for steel straightness and surface roughness. These problems limit the application of traditional technology in the production of high-end washing machine shaft steel, prompting the industry to continuously explore new rolling processes.

[0004] Therefore, developing a rolling method to increase the hardness of steel for washing machine shafts will promote technological progress and industrial upgrading in the home appliance industry, and drive the industry towards higher quality and higher efficiency. Summary of the Invention

[0005] The purpose of the present invention is to make up for the shortcomings of the existing technology and provide a rolling method for improving the hardness of steel for washing machine shafts. By finely controlling the key steps of billet pretreatment and heating, water penetration before rough rolling and controlled rolling, temperature control of finishing and final rolling, cooling bed insulation and self-tempering, straightening and surface treatment, as well as segmented processing and quality inspection, the hardness of the steel is significantly improved and the performance is optimized. The method adopts multi-stage heating and precise temperature control technology to ensure the uniformity and density of the internal structure of the steel; through water penetration cooling and temperature control in the rough rolling and finishing rolling stages, the grains are further refined and the hardness and strength of the steel are improved. In addition, the cooling bed insulation and self-tempering process effectively improves the toughness of the steel, and straightening and surface treatment ensure the straightness and surface quality of the steel.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a rolling method for increasing the hardness of steel for washing machine shafts, wherein the specific steps of the rolling method are as follows:

[0007] S100, billet pretreatment and heating: 45 steel billets are selected, the billet surface is cleaned, and then loaded into a regenerative heating furnace for multi-stage heating and insulation for 1.5 hours;

[0008] S200, water piercing before rough rolling and controlled rolling: The heated billet is descaled with high-pressure water and then sent to the horizontal and vertical alternating short stress line rolling mill for rough rolling. After rough rolling, the intermediate billet is intermittently cooled with water piercing using three water tanks to reduce the core temperature of the intermediate billet to 790-840℃;

[0009] S300, finishing and final rolling temperature control: The intermediate billet enters the three-roll KOCKS mill for finishing rolling. After finishing rolling, it passes through two water tanks for strong water penetration, and the final rolling temperature is controlled at 630-660℃;

[0010] S400, cooling bed insulation and self-tempering: the steel after finish rolling is conveyed to the cooling bed with insulation cover, and the steel is controlled to move at a speed of 18-25 seconds / step for self-tempering;

[0011] S500, straightening and surface treatment of steel: After the steel is cooled to room temperature, it is straightened by a seven-roll straightening machine with a straightness of ≤1mm / m; a high-speed rotary peeling machine is used to remove the surface oxide scale with a peeling thickness of 0.5-1mm and a surface roughness of Ra ≤6.3μm;

[0012] S600, Segment Processing and Quality Inspection: According to the steel specifications for washing machine shafts, the straightened steel is segmented and processed. After completion, the hardness, tensile strength, yield strength mechanical properties at the 3mm position are tested, as well as the surface quality and dimensional accuracy.

[0013] Furthermore, in the S100 , during the pretreatment and heating of the blank, surface oxide scale and impurities are removed by mechanical grinding combined with high-pressure water washing at a pressure of ≥10 MPa, and the surface roughness Ra is ≤12.5 μm.

[0014] Furthermore, in the S100, in the pretreatment and heating of the blank, the multi-stage heating includes: heating to a temperature of ≤800°C in the preheating section; heating to a temperature of ≤950°C in the first heating section; heating to a temperature of 1040-1200°C in the second heating section; heating to a temperature of 1100-1220°C in the first soaking section; and heating to a temperature of 1100-1220°C in the second soaking section.

[0015] Furthermore, in the S200, during the water penetration before rough rolling and controlled rolling, the water pressure of high-pressure water descaling is 1520 MPa, and the descaling coverage rate is ≥95%.

[0016] Furthermore, in the S200, water is passed before rough rolling and controlled rolling, and the rough rolling is performed in 5 passes, with an initial pass reduction of 18% and a subsequent pass reduction of 2.5%, and the intermediate billet is rolled into 50-60 mm, with a rolling speed of 0.8 m / s.

[0017] Furthermore, in the S200, during the water penetration before rough rolling and controlled rolling, the valve opening degrees of the three water tanks are 80%, 45%, and 150% respectively, the water tank flow rates are 172m³ / h, 165m³ / h, and 80m³ / h respectively, and the water tank pressures are 7.3MPa, 6.8MPa, and 5.4MPa respectively.

[0018] Furthermore, in the S300, in the finishing and final rolling temperature control, the finishing rolling adjusts the rolling speed according to the finished product specifications: finished product specifications 30-33mm: rolling speed 4.5m / s; finished product specifications 34-38mm: rolling speed 4.2m / s; finished product specifications 39-42mm: rolling speed 3.8m / s; finished product specifications 43-45mm: rolling speed 3.2m / s; 4-pass rolling is adopted, with a reduction of 7%-10% in each pass and a dimensional tolerance of ±0.3mm.

[0019] Furthermore, in the S300, in the finishing and final rolling temperature control, the valve opening degrees of the two water tanks during strong water penetration are 80% and 60% respectively, the flow rate is 302m³ / h, and the pressures are 10.6MPa and 9.1MPa respectively.

[0020] Furthermore, in the S400, during the self-tempering in the cooling bed, the temperature drop rate in the cooling bed zone is 5-8°C / min, so that the temperature of the steel is maintained in the range of 200-250°C, and the temperature is kept for 30-40 minutes.

[0021] Furthermore, the S600 has a hardness requirement of 250-270 HBW during segmented processing and quality inspection; the tensile performance requirements of the steel are: tensile strength ≥ 680 MPa, yield strength ≥ 375 MPa, elongation ≥ 16%, and impact energy ≥ 35 J; size requirements: diameter tolerance ± 0.2 mm, ovality ≤ 0.3 mm; surface quality: no cracks or folds during visual inspection.

[0022] Compared with the prior art, this rolling method for increasing the hardness of washing machine shaft steel has the following beneficial effects:

[0023] 1. The present invention achieves a significant improvement in the hardness of steel by precisely controlling multiple key links, including billet pretreatment and heating, water penetration before rough rolling and controlled rolling, and temperature control during finishing and final rolling. Among them, multi-stage heating and insulation treatment ensures the uniformity of the internal structure of the billet, laying a good foundation for subsequent rolling; the water penetration process before rough rolling and controlled rolling effectively reduces the core temperature of the intermediate billet, avoiding coarse grains; the accuracy of temperature control during finishing and final rolling further optimizes the microstructure of the steel, thereby improving the hardness and mechanical properties of the steel. These aspects work together to enable the steel for washing machine shafts prepared by the present invention to achieve a hardness of 250-270 HBW, meeting the requirements of washing machine shafts for high hardness and high strength materials, and improving the service life and reliability of the product.

[0024] 2. The present invention uses a seven-roll straightening machine for straightening through straightening and surface treatment processes to ensure the straightness of the steel, and a high-speed rotary peeling machine to remove surface oxide scales, further improving the surface quality and surface roughness of the steel. In addition, the segmented processing and quality inspection links strictly control the dimensional accuracy and mechanical properties of the steel, ensuring that each batch of steel can meet the high standards required for washing machine shaft steel. These aspects not only improve the yield of steel, but also reduce subsequent processing costs, providing better quality and more efficient raw materials for the production of washing machine shafts.

[0025] Other advantages, objects and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be learned from the practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0027] Figure 1 The present invention is a flow chart of a rolling method for increasing the hardness of steel used in washing machine shafts. DETAILED DESCRIPTION

[0028] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0029] Example 1:

[0030] Rolling of 30mm specification steel for washing machine shafts.

[0031] S100, blank pretreatment and heating:

[0032] 45 steel billets were selected, and mechanical grinding combined with high-pressure water washing at a pressure of 10 MPa was used to remove the oxide scale and impurities on the billet surface. After treatment, the surface roughness Ra of the billet reached 12.5 μm.

[0033] The cleaned blank is loaded into a regenerative heating furnace for multi-stage heating, such as Figure 1 As shown:

[0034] The preheating section heats the blank to 750°C.

[0035] Heat for a period of time until the billet temperature reaches 900℃.

[0036] The second stage of heating raises the billet temperature to 1040°C.

[0037] Heat in the soaking stage to keep the billet temperature at 1100℃.

[0038] The billet temperature is maintained at 1100°C in the second stage of uniform heating, and then kept warm for 1.5 hours.

[0039] S200, water piercing before rough rolling and controlled rolling:

[0040] The heated blank is descaled by high-pressure water at a water pressure of 15 MPa, and the descaling coverage rate reaches 95%.

[0041] The descaled billet is sent to the horizontal and vertical alternating short stress line rolling mill for rough rolling, which is a 5-pass rolling process:

[0042] The initial pass reduction was 18%.

[0043] The reduction in each subsequent pass is reduced by 2.5%, and the intermediate billet is finally rolled into a 50mm thick intermediate billet at a rolling speed of 0.8m / s.

[0044] After rough rolling, three water tanks are used to intermittently cool the intermediate billet:

[0045] The first water tank valve is open to 80%, with a flow rate of 172m³ / h and a pressure of 7.3MPa.

[0046] The second water tank valve is open to 45%, with a flow rate of 165m³ / h and a pressure of 6.8MPa.

[0047] The third water tank valve is opened to 150%, with a flow rate of 80m³ / h and a pressure of 5.4MPa.

[0048] After cooling, the core temperature of the intermediate billet drops to 790℃.

[0049] S300, finishing and final rolling temperature control:

[0050] The intermediate billet enters the three-roll KOCKS rolling mill for finishing rolling. Since the finished product specification is 30mm, the rolling speed is adjusted to 4.5m / s. Four passes are used, and the reduction in each pass is between 7% and 10%. The final dimensional tolerance is controlled at ±0.3mm.

[0051] After finishing rolling, the steel is forced through two water tanks:

[0052] The first water tank valve is open to 80%, with a flow rate of 302 m³ / h and a pressure of 10.6 MPa.

[0053] The second water tank valve is open to 60%, with a flow rate of 302m³ / h and a pressure of 9.1MPa.

[0054] After strong water penetration, the final rolling temperature is controlled at 630℃.

[0055] S400, cooling bed insulation self-tempering:

[0056] The steel after finish rolling is transported to a cooling bed with an insulation cover, and the steel is controlled to move at a speed of 18 seconds per step for self-tempering.

[0057] The temperature drop rate in the cooling bed zone is 5°C / min, so that the steel temperature is maintained within the range of 200°C for 30 minutes.

[0058] S500, straightening and surface treatment steel:

[0059] After the steel is cooled to room temperature, it is straightened by a seven-roller straightening machine. The straightness after straightening is 0.8 mm / m.

[0060] A high-speed rotary peeling machine was used to remove the surface oxide scale. The peeling thickness was 0.5 mm and the surface roughness Ra after treatment was 6.0 μm.

[0061] S600, segmented processing and quality inspection:

[0062] According to the steel specifications for washing machine shafts, the straightened steel is processed in sections.

[0063] After completion, test:

[0064] The hardness at 3mm is 250HBW.

[0065] Tensile properties: tensile strength is 680MPa, yield strength is 375MPa, elongation is 16%, and impact energy is 35J.

[0066] Dimensions: Diameter tolerance is ±0.2mm, ovality is 0.2mm.

[0067] Surface quality: Visually inspect for cracks and folds.

[0068] In summary, the embodiment employs a specific rolling process for 30mm steel for washing machine shafts. After mechanical grinding and 10MPa high-pressure water cleaning, the billet is heated in a regenerative furnace in multiple stages: a preheating stage at 750°C, a second heating stage at 1040°C, and a 1.5-hour hold. Rough rolling is performed through five passes with an initial reduction of 18%, followed by a gradual reduction, to a 50mm intermediate bar. The bar undergoes intermittent water dredging through three water tanks, reducing the core temperature to 790°C. Finishing rolling is performed at a speed of 4.5m / s with four reduction passes. After two water tanks of forced water dredging, the final rolling temperature is 630°C. The cooling bed moves at an 18-second per-step rate, with a temperature drop of 5°C / min. The bar is then held for 30 minutes. After straightening, the bar achieves a straightness of 0.8mm / m and a peel thickness of 0.5mm. Testing reveals a hardness of 250 HBW, a tensile strength of 680 MPa, a dimensional tolerance of ±0.2mm, and no surface defects. This process effectively improves the hardness and overall performance of 30mm steel.

[0069] Example 2:

[0070] Rolling of 45mm specification steel for washing machine shafts.

[0071] S100, blank pretreatment and heating:

[0072] 45 steel billets were selected, and the surface oxide scale and impurities of the billets were removed by mechanical grinding combined with high-pressure water washing at a pressure of 12 MPa. After treatment, the surface roughness Ra of the billets was 12.0 μm.

[0073] The billet is loaded into the regenerative heating furnace for multi-stage heating:

[0074] The preheating section is heated to 780°C.

[0075] Heat to 930℃ in one stage.

[0076] The second heating stage is heated to 1100°C.

[0077] Heat to 1150℃ in the soaking stage.

[0078] Heat the second stage of soaking to 1150℃ and then keep it warm for 1.5h.

[0079] S200, water piercing before rough rolling and controlled rolling:

[0080] The heated blank was descaled by high-pressure water at a water pressure of 18 MPa, and the descaling coverage rate reached 96%.

[0081] The descaled billet is sent to the horizontal and vertical alternating short stress line rolling mill for rough rolling, which is a 5-pass rolling process:

[0082] The initial pass reduction is 18%.

[0083] The reduction in each subsequent pass is reduced by 2.5%, and the intermediate billet is finally rolled into a 60mm thick intermediate billet at a rolling speed of 0.8m / s.

[0084] After rough rolling, three water tanks are used to intermittently cool the intermediate billet:

[0085] The first water tank valve is open 80%, with a flow rate of 172m³ / h and a pressure of 7.3MPa.

[0086] The second water tank valve is open 45%, with a flow rate of 165m³ / h and a pressure of 6.8MPa.

[0087] The third water tank valve is opened to 150%, with a flow rate of 80 m³ / h and a pressure of 5.4 MPa.

[0088] After cooling, the core temperature of the intermediate billet drops to 820℃.

[0089] S300, finishing and final rolling temperature control:

[0090] The intermediate billet enters the three-roll KOCKS rolling mill for finishing rolling. Since the finished product specification is 45mm, the rolling speed is adjusted to 3.2m / s. Four rolling passes are used, with the reduction in each pass between 7% and 10%. The final dimensional tolerance is controlled at ±0.3mm.

[0091] After finishing rolling, the steel is forced through two water tanks:

[0092] The first water tank valve is open 80%, with a flow rate of 302 m³ / h and a pressure of 10.6 MPa.

[0093] The second water tank valve is open 60%, with a flow rate of 302m³ / h and a pressure of 9.1MPa.

[0094] After strong water penetration, the final rolling temperature is controlled at 650℃.

[0095] S400, cooling bed insulation self-tempering:

[0096] The steel after finish rolling is transported to a cooling bed with an insulation cover, and the steel is controlled to move at a speed of 25 seconds per step for self-tempering.

[0097] The temperature drop rate in the cooling bed zone is 7°C / min, so that the steel temperature is maintained within the range of 230°C for 35 minutes.

[0098] S500, straightening and surface treatment steel:

[0099] After the steel is cooled to room temperature, it is straightened by a seven-roll straightening machine. The straightness after straightening is 0.9 mm / m.

[0100] A high-speed rotary peeling machine was used to remove the surface oxide scale. The peeling thickness was 0.8 mm and the surface roughness Ra after treatment was 6.2 μm.

[0101] S600, segmented processing and quality inspection:

[0102] The straightened steel is processed in sections according to the steel specifications for washing machine shafts.

[0103] After completion, test:

[0104] The hardness at the 3mm position is 265HBW.

[0105] Tensile properties: tensile strength is 700MPa, yield strength is 380MPa, elongation is 17%, and impact energy is 36J.

[0106] Dimensions: Diameter tolerance is ±0.15mm, ovality is 0.25mm.

[0107] Surface quality: Visually inspect for cracks and folds.

[0108] In summary, in Example 2, for 45mm specification steel, the billet is cleaned with 12MPa high-pressure water, heated in multiple stages to 1150℃ in the soaking section, kept warm for 1.5h, the intermediate billet is 60mm after rough rolling, the core temperature after water penetration is 820℃, the finishing speed is 3.2m / s, 4 passes are rolled, the final rolling temperature is 650℃, the cooling bed moving speed is 25 seconds / step, the temperature drop is 7℃ / min, and the temperature is kept warm for 35min. The straightness after straightening is 0.9mm / m, the peeling thickness is 0.8mm, the hardness is 265HBW, the tensile strength is 700MPa, the dimensional tolerance is ±0.15mm, and the surface quality is good. The process achieves the performance requirements of 45mm specification steel by precisely controlling the parameters of each stage, indicating that this rolling method has good applicability for steel for washing machine shafts of different specifications, and can effectively improve the hardness and mechanical properties of steel.

[0109] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A rolling method for increasing the hardness of steel for washing machine shafts, characterized in that: The specific steps of the rolling method are: S100, billet pretreatment and heating: 45 steel billets are selected, the billet surface is cleaned, and then loaded into a regenerative heating furnace for multi-stage heating and insulation for 1.5 hours; S200, water piercing before rough rolling and controlled rolling: The heated billet is descaled with high-pressure water and then sent to the horizontal and vertical alternating short stress line rolling mill for rough rolling. After rough rolling, the intermediate billet is intermittently cooled with water piercing using three water tanks to reduce the core temperature of the intermediate billet to 790-840℃; S300, finishing and final rolling temperature control: The intermediate billet enters the three-roll KOCKS mill for finishing rolling. After finishing rolling, it passes through two water tanks for strong water penetration, and the final rolling temperature is controlled at 630-660℃; S400, cooling bed insulation and self-tempering: the steel after finish rolling is conveyed to the cooling bed with insulation cover, and the steel is controlled to move at a speed of 18-25 seconds / step for self-tempering; S500, straightening and surface treatment of steel: After the steel is cooled to room temperature, it is straightened by a seven-roll straightening machine with a straightness of ≤1mm / m; a high-speed rotary peeling machine is used to remove the surface oxide scale with a peeling thickness of 0.5-1mm and a surface roughness of Ra ≤6.3μm; S600, Segment Processing and Quality Inspection: According to the steel specifications for washing machine shafts, the straightened steel is segmented and processed. After completion, the hardness, tensile strength, yield strength mechanical properties at the 3mm position are tested, as well as the surface quality and dimensional accuracy.

2. The rolling method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the above S100, during the pretreatment and heating of the blank, surface oxide scale and impurities are removed by mechanical grinding combined with high-pressure water washing with a pressure of ≥10 MPa, and the surface roughness Ra is ≤12.5 μm.

3. The rolling method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the S100, the multi-stage heating in the pretreatment and heating of the blank includes: heating to a temperature of ≤800°C in the preheating stage; heating to a temperature of ≤950°C in the first heating stage; heating to a temperature of 1040-1200°C in the second heating stage; heating to a temperature of 1100-1220°C in the first soaking stage; and heating to a temperature of 1100-1220°C in the second soaking stage.

4. The method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the S200, during the water penetration before rough rolling and controlled rolling, the water pressure of high-pressure water descaling is 15-20 MPa, and the descaling coverage rate is ≥95%.

5. The rolling method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the S200, water is passed before rough rolling and controlled rolling. The rough rolling is performed in 5 passes, with an initial pass reduction of 18% and a subsequent pass reduction of 2.5%. The intermediate billet is rolled into a 50-60 mm intermediate billet at a rolling speed of 0.8 m / s.

6. The method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the S200, during the water penetration before rough rolling and controlled rolling, the valve opening degrees of the three water tanks are 80%, 45%, and 150% respectively, the water tank flow rates are 172m³ / h, 165m³ / h, and 80m³ / h respectively, and the water tank pressures are 7.3MPa, 6.8MPa, and 5.4MPa respectively.

7. The method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the S300, in the finishing and final rolling temperature control, the finishing rolling speed is adjusted according to the finished product specifications: finished product specifications 30-33mm: rolling speed 4.5m / s; finished product specifications 34-38mm: rolling speed 4.2m / s; finished product specifications 39-42mm: rolling speed 3.8m / s; finished product specifications 43-45mm: rolling speed 3.2m / s; 4-pass rolling is adopted, with a reduction of 7%-10% in each pass and a dimensional tolerance of ±0.3mm.

8. The method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the S300, in the finishing and final rolling temperature control, the valve opening degrees of the two water tanks during strong water penetration are 80% and 60% respectively, the flow rate is 302m³ / h, and the pressures are 10.6MPa and 9.1MPa respectively.

9. The rolling method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: In the S400, during the self-tempering in the cooling bed, the temperature drop rate in the cooling bed zone is 5-8°C / min, so that the temperature of the steel is maintained in the range of 200-250°C, and the temperature is kept for 30-40 minutes.

10. The rolling method for increasing the hardness of washing machine shaft steel according to claim 1, characterized in that: The S600 has a hardness requirement of 250-270 HBW during segmented processing and quality inspection; the tensile performance requirements of the steel are: tensile strength ≥ 680 MPa, yield strength ≥ 375 MPa, elongation ≥ 16%, and impact energy ≥ 35 J; dimensional requirements are: diameter tolerance ± 0.2 mm, ovality ≤ 0.3 mm; surface quality: visual inspection shows no cracks or folds.

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