Quenching and tempering process for high-carbon chromium bearing steel for machine tool screw

Abstract

The application discloses a kind of high carbon chromium bearing steel quenching and tempering process for machine tool screw, belongs to material heat treatment technical field, comprising: high carbon chromium bearing steel is executed multi-section ladder type induction heating to reach austenitizing temperature;High carbon chromium bearing steel after heating is executed quenching cooling;High carbon chromium bearing steel after quenching cooling is executed multi-section ladder type induction tempering;High carbon chromium bearing steel after induction tempering is executed slow cooling treatment;The application is synergized by ladder type heating and tempering Control temperature, effectively regulate heat treatment stress and ensure straightness, solve the problem that high carbon chromium bearing steel induction quenching and tempering is easy to crack and deformation is out of tolerance, improve the comprehensive performance and production efficiency of machine tool screw.

Description

Technical Field

[0001] This invention relates to a quenching and tempering process, specifically a quenching and tempering process for high-carbon chromium bearing steel used in machine tool lead screws, belonging to the field of material heat treatment technology. Background Technology

[0002] As a core transmission component of CNC machine tools, the ball screw's technical characteristics directly determine the machine tool's positioning accuracy, repeatability, and dynamic response capability, providing crucial technical support for high-precision machining. During operation, ball screws typically withstand rolling contact loads and frictional wear, with failure modes primarily including fatigue spalling and localized pitting. Therefore, the screw material must possess high contact fatigue strength, high hardness, and good core toughness. Currently, domestically produced ball screws still lag behind their foreign counterparts in terms of precision retention and fatigue life, primarily due to the lack of core heat treatment technologies for long-life, high-reliability manufacturing.

[0003] Currently, domestic ball screw manufacturers generally use high-carbon chromium bearing steel as raw material. In the manufacturing process of slender shaft parts such as machine tool screws, heat treatment is a key process to obtain good comprehensive mechanical properties. In existing technologies, the heat treatment of such parts mainly adopts traditional heating methods such as box furnaces or pit furnaces. Although deformation can be controlled by long-term heat preservation and multiple stress-relief tempering, the production process requires multiple stress-relief tempering and straightening processes in box furnaces or pit furnaces. Generally, ordinary heat treatment methods require 6-8 stress-relief tempering processes to meet the production requirements of high-precision ball screws. It is also impossible to achieve independent control of "single quenching and single tempering". The cooling conditions of each workpiece are inconsistent during the quenching process, which further aggravates the inhomogeneity of microstructure and properties. Traditional uniform methods have problems such as long production cycle, high energy consumption, serious oxidation and decarburization, and large hardness differences. Moreover, it often requires multiple straightening processes to meet the accuracy requirements, resulting in low production efficiency.

[0004] Therefore, developing a heat treatment process for high-carbon chromium bearing steel used in machine tool lead screws that can overcome the above defects has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by this invention is that thermal stress and structural stress are easily generated during the induction tempering process of high carbon chromium bearing steel in the prior art, leading to cracking and deformation exceeding the tolerance. To overcome the shortcomings of the prior art, this invention provides a tempering process for high carbon chromium bearing steel for machine tool lead screws, which achieves precise control of heat treatment stress and effective guarantee of straightness.

[0006] To address the above technical problems, this invention provides a heat treatment process for high-carbon chromium bearing steel used in machine tool lead screws. The process includes multi-stage stepped induction heating of the high-carbon chromium bearing steel through multiple heating zones of a heat treatment furnace to achieve the austenitizing temperature. The controlled temperatures for each stage of the multi-stage stepped induction heating are as follows: Round steel undergoes a heating treatment in the first heating zone of the heat treatment furnace at 770-775℃; round steel undergoes a heating treatment in the second heating zone at 850-855℃; round steel undergoes a heat preservation treatment in the third heating zone at 915-920℃; round steel undergoes a heating treatment in the fourth heating zone at 915-920℃; and round steel undergoes isothermal treatment in the fifth heating zone, maintaining the temperature at 915-920℃ before immersion in water. The first heating zone is the preheating stage, the second heating zone is the phase transformation crossing stage, and the third to fifth heating zones are the austenitizing and holding stages. The controlled temperature of the preheating stage is below the lower critical temperature of the high-carbon chromium bearing steel; the controlled temperature of the phase transformation crossing stage crosses the lower critical temperature to the upper critical temperature; the controlled temperature of the austenitizing and holding stage is above the upper critical temperature, realizing gradient management of thermal stress. The preheating stage is carried out below Ac1, which makes the overall temperature of the steel uniform and reduces the radial temperature difference of subsequent heating; the phase transformation crossing stage controls the heating rate across the two-phase region to avoid local overheating or coarse microstructure caused by uneven absorption of latent heat of phase transformation; the austenitizing and holding stage ensures that carbides are fully dissolved and the composition is homogenized. This segmented temperature control technology inhibits the initiation of microcracks caused by excessively rapid heating from the source. The heated high-carbon chromium bearing steel is subjected to quenching and cooling. Specifically, the round steel is cooled through a C-shaped water spray box. The main water spray pressure is 0.28-0.32 MPa, and the auxiliary water spray pressure is 0.1-0.12 MPa. Before the round steel leaves the water spray zone and enters the tempering section, the high-pressure main water spray breaks the vapor film to ensure hardenability, while the low-pressure auxiliary water spray covers the surface to homogenize the cooling field. This differentiated spraying strategy effectively eliminates the bending moment caused by uneven circumferential cooling of the round steel, and ensures the basic straightness of the steel from the cooling end. Multi-stage stepped induction tempering is performed on high-carbon chromium bearing steel after quenching and cooling. Slow cooling treatment is performed on high-carbon chromium bearing steel after induction tempering.

[0007] This invention employs a complete process of multi-stage stepped induction heating + quenching and cooling + multi-stage stepped induction tempering + slow cooling. By utilizing stepped heating to avoid excessive thermal stress caused by rapid temperature rise, and by using stepped tempering to gradually release the stress in the quenched structure, combined with slow cooling to stabilize dimensions, this invention effectively solves the problems of cracking and deformation exceeding tolerances in high-carbon chromium bearing steel while ensuring high efficiency of induction tempering. As a result, it achieves excellent comprehensive mechanical properties and straightness.

[0008] The technical solution further defined in this invention is: Furthermore, in the aforementioned heat treatment process for high-carbon chromium bearing steel used in machine tool lead screws, the cooled round steel bars are sequentially fed into multiple tempering zones of a heat treatment furnace for multi-stage stepped induction tempering. Specifically, the round steel bars undergo a heating process in the first tempering zone of the heat treatment furnace at 545-550℃; the round steel bars undergo a heating process in the second tempering zone of the heat treatment furnace at 665-670℃; the round steel bars undergo a first-stage holding process in the third tempering zone of the heat treatment furnace at 715-720℃; the round steel bars undergo a second-stage holding process in the fourth tempering zone of the heat treatment furnace at 715-720℃; the round steel bars undergo a third-stage holding process in the fifth tempering zone of the heat treatment furnace at 715-720℃; and the round steel bars undergo a fourth-stage holding process in the sixth tempering zone of the heat treatment furnace at 715-720℃. During continuous production, the spacing between each round steel bar is less than 30mm. The tempering temperature can be seen to include a medium-temperature stress release stage and a high-temperature microstructure stabilization stage. The control temperature of the medium-temperature stress release stage is used to initially release quenching stress. The control temperature of the high-temperature microstructure stabilization stage is higher than that of the medium-temperature stress release stage, which is used to promote the tempering sorbite transformation. The two work together to prevent secondary cracking during tempering and ensure the stability and toughness matching of the final microstructure. The temperature setting of the heating section of this invention takes into account both the sufficiency of austenitization and the suppression of grain growth. The tempering section adopts a six-step precise temperature control, especially the low-temperature start tempering of 475℃~480℃, which accurately avoids the tempering brittleness sensitive area of ​​high carbon chromium bearing steel and safely releases the initial stress. Then, it gradually climbs to 720℃ to complete the microstructure transformation. This specific parameter combination is the key process guarantee for achieving crack-free, low-deformation induction tempering.

[0009] Furthermore, in the aforementioned heat treatment process of high-carbon chromium bearing steel for machine tool lead screws, the slow cooling treatment involves the round steel being fed into a ring cooling bed via a feeding and turning mechanism for cooling.

[0010] Furthermore, in the aforementioned heat treatment process for high-carbon chromium bearing steel used in machine tool lead screws, multi-stage stepped induction heating controls the austenitization temperature of the high-carbon chromium bearing steel to be 50°C above the material's critical temperature Ac3.

[0011] Furthermore, in the aforementioned heat treatment process of high carbon chromium bearing steel for machine tool lead screws, the quenching and cooling process uses water-based polymer quenching medium for spray cooling, with the concentration of the quenching medium ranging from 5% to 7%.

[0012] Technical effect: The water-based polymer quenching medium of the present invention is a polyalkylene glycol aqueous solution, and the concentration of the water-based polymer quenching medium is controlled within a preset concentration range so that the hardness of the high carbon chromium bearing steel after quenching reaches the preset lower limit of hardness. Water-based polymer quenching media is selected instead of pure water or oil. Its reverse solubility film-forming properties are utilized to regulate the cooling rate. A vapor film forms in the high-temperature zone to slow cooling and prevent quenching cracks; in the low-temperature zone, the film ruptures to accelerate cooling and ensure the depth of the hardened layer. By precisely matching the concentration to the C-curve characteristics of high-carbon chromium bearing steel, a quenching hardness of ≥50HRC is achieved while significantly reducing thermal shock and peak structural stress during the quenching process.

[0013] After cooling, the quenching hardness of the material is ≥50HRC.

[0014] Furthermore, in the aforementioned heat treatment process of high-carbon chromium bearing steel for machine tool lead screws, induction tempering is used to decompose the tempered sorbite that appears in the metallographic structure of the material during heat treatment, so that the material hardness reaches 24-26 HRC.

[0015] Furthermore, in the aforementioned heat treatment process for high-carbon chromium bearing steel used in machine tool lead screws, the high-carbon chromium bearing steel enters the heating zone, cooling zone, tempering zone, and annular cooling zone at a rotation speed of 5 m / min ± 0.5. This method ensures the high uniformity of the round steel cross-section temperature during induction heating and tempering. The rotation eliminates the inherent circumferential magnetic field distribution differences of the induction coil, and the axial movement enables continuous production. This dynamic heat treatment mode not only improves production efficiency but also avoids uneven microstructure and residual stress imbalance caused by local overheating or underheating.

[0016] This invention involves inspecting the incoming high-carbon chromium bearing steel round bars before heating. The ends of the round bars should be neatly sawn, free from horseshoe shapes, burrs, gas cutting marks, and any oblique cuts or flattening that would affect their use. They should also be free from defects such as cracks, scars, inclusions, and scratches. After passing the inspection, a crane is used to place the round bars on the loading platform of the heat treatment furnace. The existing turning mechanism then drops the round bars one by one into the furnace body drive rollers, allowing them to rotate into the heating zone, cooling zone, tempering zone, and annular cooling zone.

[0017] The beneficial effects of this invention are: This invention optimizes the heat treatment process parameters of high-carbon chromium bearing steel for machine tool lead screws, precisely adapting to the working conditions and performance requirements of machine tool lead screws. It effectively overcomes the technical bottlenecks and cost pain points in the existing machine tool lead screw manufacturing field. Compared with existing technologies, it has significant technical, economic, and industrial benefits, specifically: (1) Expand the application boundaries of high carbon chromium bearing steel, break its long-term limitation to the field of rolling bearings, promote the expansion of high carbon chromium bearing steel to the field of machine tool core components (screws), drive the technological upgrading of supporting industries such as high carbon chromium bearing steel smelting and heat treatment, promote the diversified development of the bearing steel industry chain, and enhance the market competitiveness of my country's bearing steel industry.

[0018] (2) Promote the independent control of the machine tool parts industry, reduce dependence on imported high-end alloy steel and imported machine tool lead screws, help my country's machine tool industry upgrade to high-end, enhance the international competitiveness of my country's machine tool products, and drive the growth of machine tool exports.

[0019] (3) In line with green manufacturing and the "dual carbon" goal, the optimized conditioning process has low energy consumption and low pollutant emissions, which can reduce energy consumption and environmental pollution in the production process. At the same time, the service life of the lead screw is extended, which can reduce the generation of waste lead screws, reduce resource waste and environmental treatment costs, and generate significant environmental benefits.

[0020] (4) Promote employment and industrial synergy. The large-scale promotion of this invention can drive the development of related industries such as screw production, supporting equipment manufacturing, and steel processing, create new jobs, promote the synergistic development of the bearing steel industry and the machine tool industry, and enhance the core competitiveness of my country's high-end manufacturing industry. This invention precisely aligns with the development trends of high-end, low-cost, and green machine tool industry. It addresses the core issues of insufficient performance of low-cost materials, excessively high cost of high-performance materials, and instability of traditional heat treatment processes in traditional machine tool lead screws. Leveraging the stability and controllability of the optimized high-carbon chromium bearing steel quenching and tempering process, along with the superior comprehensive performance and outstanding cost-effectiveness of the treated lead screw, this invention not only breaks through industry technical bottlenecks but also possesses clear and feasible application prospects. Simultaneously, it brings quantifiable and sustainable significant economic benefits to all links in the industrial chain, achieving multiple enhancements in technological, market, and social value. This further promotes the upgrading and iteration of the machine tool parts industry and helps high-carbon chromium bearing steel expand from the traditional bearing field to the core machine tool parts field, broadening its application boundaries.

[0021] (5) The induction tempering process for high-carbon chromium bearing steel of the present invention fundamentally solves the industry problem of easy cracking and large deformation of high-carbon chromium bearing steel by means of a coordinated temperature control strategy of multi-stage stepped induction heating and multi-stage stepped induction tempering. Specifically, the three-stage heating mode of preheating-phase transformation crossing-austenitization effectively suppresses the radial thermal stress gradient during rapid heating and avoids the initiation of micro-cracks; the multi-stage tempering path of medium-temperature stress release-high-temperature microstructure stability realizes the safe release of quenching stress and the full transformation of tempered sorbite, eliminating the internal force root cause of macroscopic deformation; combined with the two-stage spray cooling of water-based polymer quenching medium and natural slow cooling of industrial cooling bed, the uniformity of cross-section cooling and dimensional stability are further guaranteed. This process ensures suitable hardness (24HRC~26HRC) and excellent comprehensive mechanical properties while significantly improving the straightness of the heat-treated steel. It successfully replaces the cumbersome process of multiple tempering and straightening in traditional box furnaces, greatly shortens the production cycle, reduces energy consumption and manufacturing costs, and provides reliable technical support for the large-scale application of high-carbon chromium bearing steel in the field of precision machine tool lead screws. Attached Figure Description

[0022] Figure 1 This is a C-curve diagram of the isothermal transformation of supercooled austenite in the quenching and tempering process of high-carbon chromium bearing steel used in machine tool lead screws according to an embodiment of the present invention. Figure 2 This is a micrograph of the metallographic structure of 8mm steel after quenching and tempering in the quenching and tempering process of high carbon chromium bearing steel for machine tool lead screws according to an embodiment of the present invention. Figure 3 This is a micrograph of the metallographic structure of a 10mm diameter steel after quenching and tempering in the quenching and tempering process of high carbon chromium bearing steel for machine tool lead screws according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the C-type water spray box in the heat treatment process of high carbon chromium bearing steel for machine tool lead screws according to an embodiment of the present invention; In the diagram: 1-drain outlet, 2-spray box body, 3-connecting block, 4-inlet pipe, 5-spray hole. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without innovative effort are within the scope of protection of this application. Example 1

[0024] A quenching and tempering process for high-carbon chromium bearing steel used in machine tool lead screws is disclosed. This process establishes a complete closed-loop heat treatment process including heating, quenching, tempering, and slow cooling, aiming to solve the cracking and deformation problems caused by the superposition of thermal stress and structural stress in high-carbon chromium bearing steel during induction heat treatment. The specific steps include: S100. Upon arrival at the factory, the steel ends should be neatly sawn and free from horseshoe-shaped defects, burrs, gas cutting marks, and oblique cuts or flattening that affect use. There should be no cracks, scars, inclusions, scratches, or other defects. After passing inspection, the steel should be placed on the loading platform of the heat treatment furnace using an overhead crane. The steel should be dropped one by one into the furnace body drive rollers through the turning mechanism, rotating slowly at 5m / min ± 0.5m / min into the heating zone, water spray cooling zone, tempering zone, and annular cooling bed. S200: High carbon chromium bearing steel is subjected to multi-stage stepped induction heating in multiple heating zones of a heat treatment furnace to bring the high carbon chromium bearing steel to the austenitization temperature. The temperature control for each stage of the multi-stage stepped induction heating is as follows: Round steel undergoes initial heating in the first heating zone of the heat treatment furnace, with the temperature controlled at 770-775℃; in the second heating zone, the temperature is further increased to 850-855℃; in the third heating zone, the temperature is held at 915-920℃; in the fourth heating zone, the temperature is further increased to 915-920℃; and in the fifth heating zone, the temperature isothermally treated, maintaining the pre-immersion temperature at 915-920℃. This multi-stage stepped induction heating ensures that the austenitizing temperature of the high-carbon chromium bearing steel is controlled 50℃ above the material's critical temperature Ac3. Figure 1 As shown in the C-curve of the isothermal transformation of supercooled austenite in high-carbon chromium bearing steel, the preheating temperature of 770℃-775℃ is set above the Ac1 line, which ensures both temperature homogenization efficiency and avoids microstructure inhomogeneity caused by local overheating into the two-phase region. The phase transformation transition temperature of 850℃~855℃ is located above the nose of the C-curve. Within this temperature range, the austenite nucleation rate is high but the growth rate is controllable, effectively preventing grain coarsening. The austenitizing temperature of 915℃-920℃ balances the carbide dissolution kinetics and grain growth thermodynamics, ensuring sufficient solid solution of alloying elements without significantly increasing grain size. Through multi-stage step control, heat has sufficient time to conduct to the core, achieving overall temperature homogenization without overheating the surface layer. Ultimately, the steel smoothly transitions to a fully austenitized state, providing a microstructure basis with uniform composition and fine grains for subsequent phase transformation.

[0025] S300, the heated high-carbon chromium bearing steel is subjected to quenching and cooling, specifically: the round steel is cooled through a C-type water spray box, with the main water spray pressure being 0.28-0.32 MPa and the auxiliary water spray pressure being 0.1-0.12 MPa, before the round steel leaves the water spray zone and enters the tempering section; The structure of the C-type spray box is as follows: Figure 4 As shown, the two ends of the spray box are symmetrically reserved with gaps to form drainage outlets 1. The drainage outlets 1 divide the spray box into two symmetrically arranged spray box bodies 2. The drainage outlets 1 are equipped with connecting blocks 3 to connect the two spray box bodies 2. The spray box bodies 2 are hollow structures. The outer wall of the spray box bodies 2 is provided with several water inlet pipes 4. The inner wall of the spray box bodies 2 is a C-shaped structure covered with several spray holes 5. Water is released through the spray holes 5 on the inner wall by water pressure to form a circular water ring. The spray box forms a circular water ring, which has a better quenching and cooling effect. Moreover, when the water flow is large, the upper and lower openings are reserved with drainage outlets to drain water and ensure the cooling effect. Quenching and cooling are carried out by spraying with polyalkylene glycol aqueous solution, with the quenching medium concentration ranging from 5% to 7%, so that the hardness of the high carbon chromium bearing steel after quenching is ≥50HRC. The quenching and cooling step immediately follows austenitizing heating. Utilizing the residual heat from induction heating or the continuity of online heat transfer, the steel in the austenitic state is rapidly cooled below the martensitic transformation zone. The core function of this step is to suppress diffusion-type phase transformation and force the supercooled austenite to transform into a high-hardness martensite structure, thereby endowing the steel with the necessary strength and wear resistance reserves. Quenching and cooling is not only an independent physical cooling process, but also a sequential step closely coupled with the aforementioned multi-stage stepped heating. The temperature uniformity at the cooling initiation point directly determines the consistency of the final hardened layer depth and the symmetry of the residual stress field.

[0026] S400 employs a multi-stage stepped induction tempering process for high-carbon chromium bearing steel after quenching and cooling. Specifically: the round bars undergo a heating process in the first tempering zone of the heat treatment furnace at 545-550℃; in the second tempering zone at 665-670℃; in the third tempering zone at 715-720℃; in the fourth tempering zone at 715-720℃; in the fifth tempering zone at 715-720℃; and in the sixth tempering zone at 715-720℃. During continuous production, the spacing between each round bar is less than 30mm. Induction tempering decomposes the tempered sorbite that appears in the metallographic structure of the material during quenching and tempering, achieving a material hardness of 24-26 HRC. By adopting a multi-stage stepped tempering process and setting multiple temperature platforms from low to high, the quenching stress can be released in batches and gradually. At the same time, it drives the orderly precipitation and spheroidization of carbides in different temperature ranges. This graded control method not only avoids macroscopic deformation caused by stress concentration, but also ensures the full transformation and uniform distribution of the tempered sorbite structure, thus achieving a dual guarantee of mechanical properties and dimensional stability.

[0027] S500, after induction tempering, high carbon chromium bearing steel undergoes slow cooling treatment, and is cooled by falling into a ring cooling bed through an existing material feeding and turning mechanism.

[0028] The microstructure of bearing steel treated with the quenching and tempering process of this invention at 8mm and 10mm is as follows: Figure 2-3 As shown.

[0029] The properties of 1-11 heat-treated round steel bars were tested according to the process of this invention. The tensile properties are shown in Table 1 and the hardness is shown in Table 2. They meet the standard requirements.

[0030] Table 1 Tensile property testing

[0031] Table 2 Hardness Test

[0032] The hardness of the sample treated by the process of this invention falls within the target range at the edge, half radius, and core, while the yield strength reaches above 750 MPa and the elongation remains above 18%. This avoids the risk of premature wear and grinding cracks caused by excessively high hardness (>30 HRC), and also prevents tool sticking, tool deformation, and surface roughness deterioration caused by excessively low hardness (<22 HRC). In actual production verification, when using this quenched and tempered bar for lead screw grinding, the tool life is extended by about 30% compared to traditional box furnace quenching and tempering materials. Moreover, due to the excellent straightness after heat treatment (controllable bending along the entire length), most specifications can meet the precision grinding benchmark requirements without straightening or with only one fine calibration, significantly reducing auxiliary time. This solution can reduce the generation of waste machine tool lead screws, reduce resource waste and environmental treatment costs. At the same time, the optimized quenching and tempering process has low energy consumption and low pollutant emissions, shortens the production cycle, helps achieve the "dual carbon" target, and generates significant environmental and social benefits. It also promotes the coordinated development of the high-carbon chromium bearing steel industry and the machine tool industry, and enhances the core competitiveness of my country's high-end manufacturing industry.

[0033] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A quenching and tempering process for high-carbon chromium bearing steel used in machine tool lead screws, characterized in that: include High-carbon chromium bearing steel is subjected to multi-stage stepped induction heating in multiple heating zones of a heat treatment furnace to reach the austenitizing temperature. The controlled temperature for each stage of the multi-stage stepped induction heating is as follows: The round steel bars are heated in the first heating zone of the heat treatment furnace, with the temperature controlled at 770-775℃. The round steel bars are heated in the second heating zone of the heat treatment furnace, with the temperature controlled at 850-855℃. The round steel bars are heat-insulated in the third heating zone of the heat treatment furnace at a temperature of 915-920℃. The round steel bars are heated in the fourth heating zone of the heat treatment furnace, raising the temperature to 915-920℃. The round steel bars undergo isothermal treatment in the fifth heating zone of the heat treatment furnace, maintaining their temperature at 915-920℃ before immersion in water. The heated high-carbon chromium bearing steel is subjected to quenching and cooling, specifically as follows: The round steel bars are cooled by passing through a C-shaped water spray box. The main water spray pressure is 0.28-0.32 MPa, and the auxiliary water spray pressure is 0.1-0.12 MPa. The round steel bars are cooled before entering the tempering section after exiting the water spray zone. The high-carbon chromium bearing steel after quenching and cooling is subjected to multi-stage stepped induction tempering; The high-carbon chromium bearing steel was subjected to slow cooling treatment after induction tempering.

2. The heat treatment process for high-carbon chromium bearing steel for machine tool lead screws according to claim 1, characterized in that: The cooled round steel bars are sequentially fed into multiple tempering zones of the heat treatment furnace for multi-stage stepped induction tempering, specifically as follows: The round steel bars are heated in the first tempering zone of the heat treatment furnace at a temperature of 545-550℃. The round steel bars are heated in the second tempering zone of the heat treatment furnace at a temperature of 665-670℃. The round steel bars undergo a first-stage heat preservation treatment in the third tempering zone of the heat treatment furnace at a temperature of 715-720℃. The round steel bars undergo a two-stage heat preservation treatment in the fourth tempering zone of the heat treatment furnace at a temperature of 715-720℃. The round steel bars undergo a three-stage heat preservation treatment in the fifth tempering zone of the heat treatment furnace, at a temperature of 715-720℃. The round steel bars undergo a four-stage heat preservation treatment in the sixth tempering zone of the heat treatment furnace, at a temperature of 715-720℃. The spacing between each round steel bar produced continuously is less than 30mm.

3. The heat treatment process for high-carbon chromium bearing steel for machine tool lead screws according to claim 1, characterized in that: The slow cooling process involves the round steel bars being dropped into a ring cooling bed for cooling.

4. The heat treatment process for high-carbon chromium bearing steel for machine tool lead screws according to claim 1, characterized in that: Multi-stage stepped induction heating controls the austenitization temperature of high-carbon chromium bearing steel to be 50°C above the material's critical temperature Ac3.

5. The heat treatment process for high-carbon chromium bearing steel for machine tool lead screws according to claim 1, characterized in that: The quenching cooling is achieved by spraying a water-based polymer quenching medium with a concentration ranging from 5% to 7%.

6. The heat treatment process for high-carbon chromium bearing steel for machine tool lead screws according to claim 1, characterized in that: After cooling, the quenching hardness of the material is ≥50HRC.

7. The heat treatment process for high-carbon chromium bearing steel for machine tool lead screws according to claim 1, characterized in that: Induction tempering is used to decompose the tempered sorbite that appears in the metallographic structure of the material during tempering, so that the material hardness reaches 24-26 HRC.

8. The heat treatment process for high-carbon chromium bearing steel for machine tool lead screws according to claim 1, characterized in that: The high-carbon chromium bearing steel enters the heating zone, cooling zone, tempering zone, and annular cooling zone at a rotational speed of 5 m / min ± 0.5.

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