Rolling process method for improving hardness of steel for pin shaft

Abstract

The invention discloses a rolling process method for improving the hardness of steel for a pin shaft, and relates to the technical field of metal processing, the process comprises the following steps: heating and blank preparation: homogenizing the structure of a steel billet by accurately controlling the heating temperature and time, and calculating the length of the blank according to the length of the required steel for the pin shaft and a rolling elongation coefficient, in the rolling process, the segmentation length of the segmentation shear is controlled, and it is guaranteed that the length of the segmented blank is matched with the machining requirement; by optimizing the heating process, accurately controlling parameters of each rolling link and adopting the processes of forced water cooling, cold bed heat preservation and slow cooling and the like, grains of the steel for the pin shaft are remarkably refined, the hardness of the steel is greatly improved, meanwhile, the comprehensive mechanical property is improved, and the steel can better adapt to the working conditions of high load and high abrasion; accurate calculation and segmentation of the blank length are matched with cooperative adjustment of the roller way and the rolling mill speed, so that the accident rate in the rolling process is effectively reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal processing, and in particular to a rolling process method for improving the hardness of pin steel. Background Art

[0002] In the field of metal processing, pins, as important mechanical components, are widely used in various types of mechanical equipment. Their performance is directly related to the reliability and stability of equipment operation. With the continuous development of industrial technology, higher requirements are placed on the hardness, strength and other comprehensive properties of pin steel. The rolling process, as a key link in the production of pin steel, plays a decisive role in the final performance of the steel. Therefore, the development of a rolling process method that can effectively improve the hardness of pin steel is of great significance to meeting market demand and improving product quality.

[0003] In the process of traditional bar rolling to produce pin steel, there are many shortcomings that restrict production efficiency and product performance improvement. First, the traditional process of segmented shearing of finished products has strict requirements on the final rolling temperature, and it is impossible to effectively shear the rolled materials with a final rolling temperature below 600°C. This leads to the fact that pin steel is often processed into pins by tempering treatment (quenching + tempering) of 40Cr bars after hot rolling. This production method has cumbersome procedures, which not only increases the production cycle but also increases production costs. Secondly, the secondary tempering and heating process consumes a lot of energy, which greatly increases carbon emissions. In addition, the traditional process does not accurately control key parameters such as billet length, rolling temperature, and reduction rate during the production process, which can easily lead to unstable product quality and high scrap rate, further increasing production costs. Moreover, the traditional process has limitations in improving the hardness and comprehensive performance of pin steel, and it is difficult to meet the growing demand for high performance. Summary of the Invention

[0004] The purpose of the present invention is to make up for the shortcomings of the existing technology and provide a rolling process method for improving the hardness of pin steel. It can break through the equipment's limitations on the final rolling temperature through a series of technical improvements such as heating process optimization, precise calculation of billet length, coordinated adjustment of rolling mill and roller speed, strong water cooling and cooling bed insulation and slow cooling. On the basis of reducing processes, reducing costs and carbon emissions, it significantly improves the hardness and comprehensive performance of pin steel. This process not only improves production efficiency and yield rate, stabilizes product quality, but also meets the development requirements of green manufacturing, and provides a new solution for the efficient and green production of pin steel.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a rolling process method for increasing the hardness of pin steel, the process comprising:

[0006] Heating and billet preparation: The billet structure is homogenized by precisely controlling the heating temperature and time. The billet length is calculated based on the required pin steel length and the rolling elongation coefficient. The segment length of the segmented shear is controlled during the rolling process to ensure that the segmented billet length meets the processing requirements.

[0007] Rough rolling and segment adjustment: adopt multi-pass variable temperature rolling process to complete the segmentation of the rolled piece in the appropriate temperature range, and coordinate the adjustment of the roller table and the rolling mill speed to ensure the reasonable multiple length spacing;

[0008] Finishing rolling and strong water-penetrating cooling: After the segmented rolled pieces are heated again, they are subjected to multiple passes of finishing rolling. Immediately after rolling, the water-penetrating cooling device is activated to perform strong water-penetrating cooling on the rolled pieces. The final rolling temperature is controlled so that the rolled pieces are cooled rapidly within this temperature range to achieve a quenching effect.

[0009] Cooling bed insulation and slow cooling: Control the cooling bed step speed under the insulation cover environment to slowly cool the rolled piece to eliminate stress and adjust the structure to optimize the hardness and toughness matching;

[0010] Tempering treatment: The cooled pin steel is tempered and cooled with the furnace to make the hardness and comprehensive performance of the pin steel meet the use requirements.

[0011] Furthermore, in the heating and blank preparation steps, the blank length is accurately calculated based on the required length of the pin steel and a rolling elongation coefficient of 1.8-2.5.

[0012] Furthermore, in the heating and blank preparation step, the blank is fed into a heating furnace, the soaking temperature is set to 1220°C, and the blank is kept at this temperature for 1.5-2.5 hours. During the heating process, the heating rate is strictly controlled within the range of 10-15°C / minute.

[0013] Furthermore, in the rough rolling and segmented adjustment steps, a multi-pass rough rolling process is adopted. The rolling temperature of the first pass is controlled at 1050-1100°C, and the reduction rate is set to 25-35%. The rolling temperature is lowered in subsequent passes, and the temperature is reduced by 30-50°C each time. The reduction rate is gradually adjusted to 15-25%. After the rough rolling is completed, when the temperature of the rolled piece drops to 750-850°C, the rolled piece is segmented using a segmented shear.

[0014] Furthermore, in the rough rolling and segment adjustment steps, the speed of each roller after segment shearing is increased by 15-25%, and the speed of the last stand rolling mill is reduced by 80-120 revolutions to ensure that each section of length is stretched at least 1.5 meters apart in the roller.

[0015] Furthermore, in the finishing rolling and strong water cooling steps, the rolled piece that has been segmented and adjusted in spacing is heated again to 880-920°C and subjected to multiple finishing rolling passes. The rolling temperature of each finishing rolling pass is within the range of 820-880°C, and the reduction rate is controlled at 10-18%.

[0016] Furthermore, in the finishing rolling and strong water cooling steps, the rolled piece is subjected to strong water cooling, the cooling water flow rate is controlled at 8-12 m / s, and the final rolling temperature is controlled between 480-520°C, so that the rolled piece is quickly cooled in this temperature range to achieve a quenching effect.

[0017] Furthermore, in the cooling bed insulation and slow cooling step, the cooling bed insulation cover is put into use in advance before the rolled piece enters the cooling bed. The steel moves on the cooling bed at a speed of 20-30 seconds per step, and the temperature inside the cooling bed insulation cover is maintained at 500-600°C, ensuring that the steel is slowly cooled on the cooling bed, eliminating internal stress, and adjusting the structure to optimize the hardness and toughness matching.

[0018] Furthermore, in the tempering step, the cooled pin shaft steel is tempered, the tempering temperature is set at 550-600° C., the holding time is controlled at 2-3 hours, and then the steel is cooled in the furnace.

[0019] Compared with the existing technology, this rolling process method for improving the hardness of pin steel has the following beneficial effects:

[0020] 1. The present invention significantly refines the grain size of the pin steel and greatly improves its hardness by optimizing the heating process, accurately controlling the parameters of each rolling link, and adopting processes such as strong water-penetrating cooling and cooling bed insulation and slow cooling. At the same time, it improves the comprehensive mechanical properties, enabling it to better adapt to high-load and high-wear working conditions. In addition, the precise calculation and segmentation of the billet length, combined with the coordinated adjustment of the roller table and rolling mill speed, effectively reduces the accident rate during the rolling process and improves production efficiency. Accurate billet length control also reduces material waste and improves the yield rate, bringing higher economic benefits to the enterprise.

[0021] 2. The present invention reduces energy consumption, equipment investment and labor costs by eliminating the quenching process, thereby significantly reducing production and processing costs. At the same time, it avoids the secondary tempering and heating process, effectively reduces carbon emissions, meets the development requirements of green manufacturing, and has good environmental benefits. In addition, due to the precise control of various process parameters, the present invention can ensure the consistency and stability of product hardness, reduce the scrap rate, improve the overall product quality, and enhance the product's competitiveness in the market.

[0022] 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

[0023] 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.

[0024] Figure 1 Schematic diagram of the martensitic structure of pin steel;

[0025] Figure 2 The present invention is a flow chart of a rolling process method for increasing the hardness of steel for pin shafts. DETAILED DESCRIPTION

[0026] 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.

[0027] The present invention provides a rolling process method for improving the hardness of steel for pin shafts. The method comprises the following steps: firstly, heating a blank to a specific temperature and keeping the temperature at a constant temperature to homogenize the structure; at the same time, accurately calculating the blank length according to the order length and the elongation coefficient and controlling the segment shear to segment the blank; then performing multiple rough rolling, and after segmenting at a suitable temperature, adjusting the roller speed and reducing the speed of the last stand rolling mill to widen the length spacing; then heating the rolled piece again and performing finish rolling, and after rolling, activating a water-penetrating cooling device to quickly cool the piece to achieve a quenching effect; then sending the piece to a cooling bed with an insulation cover put into use in advance, and slowly cooling the piece at a specific speed; finally, performing tempering treatment to eliminate stress and stabilize the structure, and effectively refining the grains by optimizing the processes of each link, thereby significantly improving the hardness and comprehensive mechanical properties of the steel for pin shafts; accurate blank calculation and process control reduce material waste and production accidents, and improve the yield rate and production efficiency; eliminating the traditional quenching process, reducing energy, equipment and labor costs; avoiding secondary tempering heating, greatly reducing carbon emissions, and meeting the requirements of green manufacturing; and strict parameter control ensuring stable product quality and reducing the scrap rate.

[0028] Example 1

[0029] Billets measuring 250mm × 300mm × 10,500mm are precisely hoisted onto the regenerative heating furnace's loading platform using an overhead crane. Before entering the furnace, operators carefully inspect their surface quality to ensure they are free of defects such as cracks and scars. Once in the furnace, the temperature is raised at a rate of 12°C / minute. During this process, three sets of thermocouples located in different areas of the furnace monitor the temperature distribution in real time. When the temperature reaches 1,220°C, the billet enters the soaking zone, where it is held for two hours to allow for full diffusion of the billet's internal components and eliminate segregation. Furthermore, based on the order's required pin specifications and an elongation coefficient of 2.0, professional rolling process calculation software is used to accurately calculate the required billet length. Before entering the rolling line, a high-precision laser rangefinder verifies the billet length and feeds this data back to the No. 2 flying shear control system. An encoder precisely controls the shear's cutting position, ensuring a segmentation error within ±3mm.

[0030] After the billet enters the roughing mill, the first rolling pass is carried out at 1080℃. The reduction rate is accurately set to 30% through the hydraulic reduction system, and the roll gap meter installed on the rolling mill is used to monitor the roll gap changes in real time to ensure that the roll gap accuracy reaches ±0.1mm. The temperature is lowered in each subsequent pass, with a temperature drop of 50℃ each time, and the reduction rate is adjusted to 25%, 20%, and 15% accordingly. During the rolling process, the temperature of the rolled piece is monitored in real time by an infrared thermometer installed at the exit of the rolling mill, and the temperature data is compared with the preset process parameters. If there is a deviation, the rolling mill speed or cooling water flow is automatically adjusted for correction. When the temperature of the rolled piece drops to 820℃, the high-temperature thermal imager installed on the rolling line detects the temperature signal, triggers the intermediate segment shearing action, and segments the rolled piece. Figure 1 As shown in the figure, after the segmentation is completed, the speed of each section of the roller after the 2# shear is immediately increased by 20%, and the speed of the last stand rolling mill is reduced by 100 revolutions. The photoelectric sensors installed at intervals on the rollers monitor the length spacing in real time. When the spacing reaches 2 meters, the system sends a stable signal to ensure that the rolled pieces will not collide during the subsequent transportation process.

[0031] The segmented pieces are conveyed via rollers to the heating device in front of the finishing mill for secondary heating to 920°C. During the finishing rolling process, the temperature is controlled in the range of 880-830°C, and the reduction rate of each pass is controlled at 10-15%. The mill is equipped with an automatic thickness control system (AGC) and pressure sensors, which can automatically adjust the rolling force and roll gap according to the real-time deformation of the piece to ensure that the thickness tolerance of the piece is controlled within ±0.05mm. After leaving the finishing mill, the pieces immediately enter the 6# and 7# water tanks for forced water cooling. The water tanks use specially designed nozzles to achieve uniform water spraying. The cooling water flow rate reaches 10m / s. When all the water tank valves are open, the flow rate reaches 302m³ / h and the pressure is 11.6MPa. The temperature of the piece is monitored in real time by temperature sensors installed before and after the water tanks, and the final rolling temperature is strictly controlled at 500°C±20°C, so that martensite structure is formed within 2-10mm of the edge of the piece, achieving the quenching effect. Figure 2 shown.

[0032] 30 minutes before the rolled piece enters the cooling bed, the operator starts the heating system of the cooling bed insulation cover, preheats the temperature inside the insulation cover to 550℃, and maintains the temperature stable through the temperature control system. After the rolled piece is transported to the cooling bed by the roller, the cooling bed moves in steps at a speed of 25 seconds per step. In different areas of the cooling bed, multiple thermocouples and infrared thermal imagers are evenly distributed to monitor the cooling rate and temperature distribution of the rolled piece in real time. Once a local temperature anomaly is found, the position of the insulation curtain or the air volume in the area is immediately adjusted to ensure that the rolled piece cools slowly, so that the internal stress can be evenly released to avoid defects such as cracks.

[0033] The cooled pin steel is hoisted into a trolley-type tempering furnace, and the tempering temperature is set at 550°C with a holding time of 2 hours. During the tempering process, the heating power is automatically adjusted according to the feedback data from the thermocouple in the furnace to ensure that the furnace temperature fluctuation range is controlled within ±5°C. After the holding period, the heating power is turned off and the rolled piece is allowed to cool to room temperature with the furnace. The treated pin steel is subjected to a comprehensive performance test, and the hardness is measured at different parts of the rolled piece using a Rockwell hardness tester, with an average value of 36-38HRC. The surface hardened layer is observed using a metallographic microscope with a depth of 10mm. The mechanical properties are tested using a tensile testing machine, and the yield strength and tensile strength meet the requirements of relevant standards. At the same time, a statistical analysis of the energy consumption, cost and carbon emission data of the production process shows that the process energy consumption is 18% lower than that of the traditional process.

[0034] Example 2

[0035] The billets to be processed are selected and their chemical composition analyzed using specialized testing equipment to ensure they meet process requirements. The billets are then hoisted to the loading area of ​​the heating furnace and fed into it via an automated conveyor. They are heated at a rate of 10°C / minute. During the heating process, the furnace's temperature control system precisely adjusts the heating power according to a preset heating curve to ensure uniform heating of the billets. Once the temperature reaches 1220°C, the furnace enters a holding phase for 2.5 hours. During this period, temperature uniformity is monitored in real time using multiple temperature monitoring devices installed within the furnace. A furnace temperature simulation system optimizes the heating curve to ensure a temperature difference of ≤±15°C across all parts of the billet. Based on the specified pin length and an elongation factor of 2.2, a specialized billet calculation model accurately calculates the initial billet length. Before entering the rolling process, the billet is measured using a high-precision length measuring instrument. The data is transmitted to the control system of the #2 flying shear. Advanced servo drives control the shear, ensuring a segmentation error of within ±4mm.

[0036] Before starting the rough rolling mill, the staff carried out a comprehensive inspection and debugging of the mechanical transmission components, lubrication system, hydraulic system, etc. of the rolling mill to ensure that the equipment is in good operating condition. After the billet enters the rough rolling mill, the initial rolling temperature is set to 1100℃, and the first pass reduction rate is set to 32%. During the rolling process, the automatic control system of the rolling mill adjusts the speed and reduction of the rolls in real time according to the preset process parameters to ensure that the rolling temperature and reduction rate of each pass meet the requirements. The temperature of the subsequent passes is reduced by 40℃ in turn, and the reduction rate is adjusted to 28%, 24%, and 20% accordingly. After each rolling pass, the pass The width and thickness of the rolled piece are detected by online width gauges and thickness gauges, and the data is fed back to the control system so that the rolling parameters of the next pass can be adjusted in time. When the temperature of the rolled piece drops to 830℃, the temperature sensor installed on the rolling line detects the signal and triggers the 2# flying shear to perform segmentation operation. After the segmentation is completed, the roller speed is automatically increased by 25%, and the last stand rolling mill is synchronously reduced by 100 revolutions. During the roller conveying process, the position and spacing of the double-length rolled pieces are monitored in real time through proximity switches installed on both sides of the roller table to ensure that the double-length spacing reaches 2.2 meters, thereby ensuring the safety and stability of the rolled pieces during transportation.

[0037] The segmented workpieces are conveyed to the heating equipment preceding the finishing mill, where they are heated to 930°C before entering the finishing rolling process. The finishing rolling process takes place within the temperature range of 890-840°C, with each pass maintaining a reduction ratio of 12-18%. The finishing mill is equipped with an advanced adaptive rolling force control system that automatically adjusts the rolling force and roll gap based on the material, temperature, and deformation of the workpiece, ensuring dimensional accuracy and surface quality. Immediately after leaving the finishing mill, the workpieces enter a through-water cooling unit for intensive through-water cooling. The cooling unit utilizes specially designed nozzles and a water circulation system for efficient and uniform cooling. By adjusting the flow and pressure of the cooling water pump to a flow rate of 11 m / s, the workpiece is rapidly cooled. During the cooling process, temperature sensors installed before and after the cooling unit monitor the workpiece temperature in real time, maintaining a stable final rolling temperature of 490°C and ensuring a martensite content of ≥95% within 10 mm of the workpiece edge, effectively improving the hardness and strength of the steel.

[0038] Before the rolled piece enters the cooling bed, the heating system of the cooling bed insulation cover is started 30 minutes in advance to raise the temperature inside the insulation cover to 580°C and maintain the temperature constant through the temperature automatic adjustment device. The cooling bed adopts variable frequency speed regulation technology, and the steel billet moves on the cooling bed at a speed of 22 seconds per step. Multiple thermocouples and temperature monitoring probes are arranged at different positions of the cooling bed to collect the temperature data of the steel billet in real time. According to the preset cooling curve, the moving speed of the cooling bed, the insulation effect of the insulation cover and the air volume of the ventilation system are automatically adjusted to ensure that the steel billet cools slowly, so that the internal structure is fully adjusted and optimized, and the grain size of the microstructure is ≤5μm.

[0039] The cooled rolled pieces are hoisted into a pit-type tempering furnace, and the tempering temperature is set at 580°C with a holding time of 2.5 hours. The tempering furnace uses temperature control technology, which can accurately control the uniformity and stability of the furnace temperature. During the tempering process, the temperature control system in the furnace automatically adjusts the power of the heating element according to the temperature data fed back by the thermocouple to ensure that the furnace temperature fluctuation range is controlled within a very small range. After the holding period, the heating power is turned off and the rolled pieces are allowed to cool to room temperature with the furnace. A comprehensive performance test is conducted on the tempered pin steel, and its hardness is measured using a Vickers hardness tester, with an average value of 38HRC. The depth of the quenching layer is observed through a metallographic microscope and reaches 10mm. Fatigue performance testing is performed on a fatigue testing machine, and its fatigue life is significantly improved. At the same time, cost accounting and carbon emission statistics are conducted on the entire production process. The results show that compared with traditional processes, this process reduces carbon emissions by 22% and processing costs by 20%, fully demonstrating the advantages of this process in green manufacturing and economic benefits.

[0040] 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 process for increasing the hardness of pin steel, characterized in that: The process includes: Heating and billet preparation: The billet structure is homogenized by precisely controlling the heating temperature and time. The billet length is calculated based on the required pin steel length and the rolling elongation coefficient. The segment length of the segmented shear is controlled during the rolling process to ensure that the segmented billet length meets the processing requirements. Rough rolling and segment adjustment: adopt multi-pass variable temperature rolling process to complete the segmentation of the rolled piece in the appropriate temperature range, and coordinate the adjustment of the roller table and the rolling mill speed to ensure the reasonable multiple length spacing; Finishing rolling and strong water-penetrating cooling: After the segmented rolled pieces are heated again, they are subjected to multiple passes of finishing rolling. Immediately after rolling, the water-penetrating cooling device is activated to perform strong water-penetrating cooling on the rolled pieces. The final rolling temperature is controlled so that the rolled pieces are cooled rapidly within this temperature range to achieve a quenching effect. Cooling bed insulation and slow cooling: Control the cooling bed step speed under the insulation cover environment to slowly cool the rolled piece to eliminate stress and adjust the structure to optimize the hardness and toughness matching; Tempering treatment: The cooled pin steel is tempered and cooled with the furnace to make the hardness and comprehensive performance of the pin steel meet the use requirements.

2. A rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the heating and blank preparation steps, the blank length is accurately calculated based on the required length of the pin steel and a rolling elongation coefficient of 1.8-2.

5.

3. The rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the heating and blank preparation step, the blank is fed into a heating furnace, the soaking temperature is set to 1220° C., and the blank is kept at this temperature for 1.5-2.5 hours. During the heating process, the heating rate is strictly controlled within the range of 10-15° C. / minute.

4. A rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the rough rolling and segmented adjustment steps, a multi-pass rough rolling process is adopted. The rolling temperature of the first pass is controlled at 1050-1100°C, and the reduction rate is set to 25-35%. The rolling temperature is lowered in subsequent passes, and the temperature is reduced by 30-50°C each time. The reduction rate is gradually adjusted to 15-25%. After the rough rolling is completed, when the temperature of the rolled piece drops to 750-850°C, the rolled piece is segmented using a segmented shear.

5. The rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the rough rolling and segment adjustment steps, the roller speed of each section after segment shearing is increased by 15-25%, and the final stand rolling mill is reduced by 80-120 revolutions to ensure that each section is stretched at least 1.5 meters apart in the roller.

6. The rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the finishing rolling and strong water cooling step, the rolled piece that has been segmented and adjusted in spacing is heated again to 880-920° C. and subjected to multiple passes of finishing rolling. The rolling temperature of each pass of the finishing rolling is within the range of 820-880° C., and the reduction rate is controlled at 10-18%.

7. The rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the finishing rolling and strong water cooling steps, the rolled piece is subjected to strong water cooling, the cooling water flow rate is controlled at 8-12 m / s, and the final rolling temperature is controlled between 480-520° C., so that the rolled piece is quickly cooled in this temperature range to achieve a quenching effect.

8. The rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the cooling bed insulation and slow cooling step, before the rolled piece enters the cooling bed, the cooling bed insulation cover is put into use in advance, and the temperature inside the cooling bed insulation cover is maintained at 500-600°C to ensure that the steel is slowly cooled on the cooling bed, eliminate internal stress, and adjust the structure to optimize the hardness and toughness matching.

9. The rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the cooling bed insulation and slow cooling step, the steel moves on the cooling bed at a speed of 20-30 seconds per step during the cooling bed insulation and slow cooling stage.

10. A rolling process for increasing the hardness of pin steel according to claim 1, characterized in that: In the tempering step, the cooled pin shaft steel is tempered, the tempering temperature is set at 550-600° C., the holding time is controlled at 2-3 hours, and then the steel is cooled in the furnace.

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