A double-frequency induction quenching heat treatment method for high-carbon chromium bearing steel ball screws

Abstract

The application discloses a kind of high-carbon chromium bearing steel ball screw double-frequency induction quenching heat treatment methods, comprising: the clamping positioning of workpiece;Cleaned high-carbon chromium bearing steel ball screw is placed on the driving device of induction heat treatment equipment, and clamping positioning is carried out;Workpiece induction quenching heat treatment processing: setting processing procedure, start induction heat treatment equipment, ball screw moves at uniform speed along its axial direction, and simultaneously keeps autorotation, in turn passes through preheating inductor, quenching inductor and quenching medium spray ring, to carry out induction quenching heat treatment to the surface of ball screw;After induction quenching heat treatment ends, the ball screw of processing completion is taken out.The induction quenching heat treatment process provided in the application can solve the problems of serious deformation of high-carbon chromium ball screw, poor consistency of hardened layer hardness, and can improve fatigue life and reliability, with low requirement for operator's knowledge level and experience, good repeatability and stable quality.

Description

Technical Field

[0001] This invention belongs to the technical field of induction heat treatment of metallic materials, and particularly relates to a dual-frequency induction quenching heat treatment method for high carbon chromium bearing steel ball screws. Background Technology

[0002] Ball screws are key core components of CNC machine tools. However, domestically produced ball screws currently suffer from problems such as uneven hardening layers, unstable quality, and low precision retention, failing to meet the requirements of high-end CNC machine tools and resulting in a heavy reliance on imports (approximately 80%). One major reason for this is the lack of core technologies for long-life, high-reliability induction hardening heat treatment. Therefore, it is urgent to develop key technologies for precision and efficient induction hardening heat treatment of ball screws to solve problems such as large deformation and uneven hardening layers, improve stability and precision retention, thereby enhancing reliability and fatigue life, strengthening the independent controllability of core functional components in high-end CNC machine tools, and contributing to the improvement of my country's manufacturing level of high-precision CNC machine tool ball screws.

[0003] Ball screws typically endure rolling contact loads and frictional wear during operation, with fatigue spalling and localized pitting being the main failure modes. Therefore, ball screws require high contact fatigue strength. Induction hardening can form a hardened layer with high hardness and appropriate hardness gradient on the surface of the ball screw. During quenching, the formation of martensite causes volume expansion and generates residual compressive stress, effectively improving its fatigue resistance. However, traditional induction hardening processes often fail to achieve a uniform and stable hardened layer on the ball screw surface, significantly reducing its service life.

[0004] To improve the induction hardening process of ball screws, researchers have made many efforts, mainly by coating with magnetic conductors, using multiple coils, tilting coils, and local hardening of the groove to improve the uniformity and depth of the hardened layer of the ball screw. For example, invention patent CN109423546A discloses a method for induction hardening of ball screws. The ball screw is preheated with medium-frequency current and then threaded. A mud-like magnetic conductor is then coated on the groove of the screw and left at room temperature for 2-4 hours until the mud-like magnetic conductor is completely dry. After that, a high-frequency heating inductor tilted at 30° is used to induction harden the ball screw coated with the magnetic conductor to obtain a conformal hardened layer. Invention patent CN115612791A discloses an energy-saving induction hardening equipment and method for hollow ball screws. It uses an induction coil that matches the shape and size of the ball screw thread, sets the ball screw rotation speed that matches the axial movement speed of the induction coil, and adds a magnetic conductor and a linkage water spray ring to the induction coil. By utilizing the strong driving effect of the magnetic conductor, the purpose of induction heating and hardening is achieved only on the thread part of the ball screw. Obviously, these methods involve coating the magnetic conductor and waiting for it to dry, tilting the coil, etc., which will undoubtedly increase the complexity of the process, the difficulty of operation, the process cycle and time cost, making it impossible to achieve continuous mass production. Moreover, the complex process and operation make it difficult to guarantee the uniformity and repeatability of the ball screw hardened layer. Summary of the Invention

[0005] Based on the shortcomings of the prior art, the technical problem solved by the present invention is to provide a dual-frequency induction quenching heat treatment method for high carbon chromium bearing steel ball screws. The dual-frequency induction heat treatment process, which combines a preheating inductor and a quenching inductor, prepares a certain depth of conformal hardening layer on the surface of the high carbon chromium bearing steel ball screw, while the core still maintains good toughness, thereby achieving the purpose of improving the wear resistance and fatigue life of the ball screw.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] The present invention provides a method for dual-frequency induction hardening heat treatment of high-carbon chromium bearing steel ball screws, comprising the following steps:

[0008] S1. Workpiece clamping and positioning: Place the cleaned high-carbon chromium bearing steel ball screw on the drive device of the induction heat treatment equipment and clamp and position it.

[0009] S2. Induction hardening heat treatment of the workpiece: According to the material, shape, size characteristics of the ball screw and the required hardened layer thickness, the processing program is set, the induction heat treatment equipment is started, the ball screw moves at a constant speed along its axial direction and rotates at the same time, passing through the preheating inductor, the quenching inductor and the quenching medium spray ring in sequence to perform induction hardening heat treatment on the surface of the ball screw.

[0010] S3. After the induction hardening heat treatment is completed, stop the induction heating and spray quenching medium, and take out the finished high carbon chromium bearing steel ball screw.

[0011] Furthermore, in step S2, the moving speed of the ball screw is 6-15 mm / s, and its rotational speed is equal to the axial moving speed of the ball screw and the lead of the ball screw.

[0012] Optionally, in step S2, the parameters of the preheating inductor are: rated power of 20–150 kW, voltage of 160–500 V, current of 20–300 A, and frequency of 1–20 kHz; the parameters of the quenching inductor are: rated power of 50–200 kW, voltage of 300–500 V, current of 50–400 A, and frequency of 20–100 kHz; the distance between the preheating inductor and the quenching inductor is 100–120 mm.

[0013] Furthermore, in step S2, the parameter range of the quenching medium spray ring is as follows: the flow rate of the quenching medium is 100–800 L / min, and the spray holes for spraying the quenching medium on the inner circumference of the quenching medium spray ring are evenly distributed in a 5mm × 5mm checkerboard pattern; wherein the size of the spray holes is selected according to the diameter of the ball screw. When the diameter of the ball screw is <15mm, the diameter of the spray hole is 1–1.5mm; when the diameter of the ball screw is in the range of 15–38mm, the diameter of the spray hole is 1.5–2.5mm; when the diameter of the ball screw is >38mm, the diameter of the spray hole is 3.5–4mm.

[0014] Optionally, in step S2, the setting of the processing program is obtained by simulating and optimizing the shape and size of the preheating inductor and the quenching inductor, the number of turns of the coil, the turn spacing, and the combination matching relationship between various parameters.

[0015] Furthermore, in step S3, the ball screw that has undergone induction hardening heat treatment has a surface hardened layer with a thickness of 0.8 to 9.6 mm, a tooth tip and groove hardness of 764 to 833 HV, a hardened layer hardness consistency of ≤1 HRC, a deformation of ≤0.15 mm / m, and good toughness in the core, resulting in significantly improved wear resistance and fatigue life.

[0016] Therefore, the dual-frequency induction hardening heat treatment method for high-carbon chromium bearing steel ball screws of the present invention has the following beneficial effects:

[0017] 1. A dual-frequency induction heat treatment process combining a preheating induction generator and a quenching induction generator is used to prepare a contour-hardened layer of the required thickness on the surface of a high-carbon chromium bearing steel ball screw, while maintaining good toughness in the core matrix. This improves the wear resistance and fatigue life of the ball screw. Contour-hardening of the ball screw can be achieved, with the thickness of the contour-hardened layer adjustable from 0.8 to 9.6 mm. The hardness of the tooth tip and raceway reaches 764–833 HV, the hardness consistency of the hardened layer is ≤1 HRC, and the deformation is ≤0.15 mm / m.

[0018] 2. The shape and dimensions of the preheating and quenching inductors, the number of coil turns, the spacing, and the combination and matching relationships between various parameters were simulated and optimized. The performance changes of ball screws of different materials and specifications after induction heat treatment experiments under multiple sets of different parameters were explored. Test results show that the dual-frequency induction quenching heat treatment method provided by this invention can solve the problems of severe deformation exceeding tolerances and poor hardness consistency of the hardened layer in high-carbon chromium bearing steel ball screws. It can also significantly improve their strength, toughness, wear resistance, and precision retention, thereby increasing their fatigue life and reliability. This method has low requirements for operator knowledge and experience, is technically reliable, has good repeatability, stable quality, and significant economic benefits.

[0019] 3. This invention eliminates the need to coat the ball screw's raceway with a magnetic material and is not limited to localized quenching of the raceway. By controlling the combination and matching relationship between the parameters of the preheating inductor and the quenching inductor, the tooth tip and raceway of the ball screw can be quenched simultaneously, resulting in a high-performance conformal hardened layer. The core retains good toughness, deformation is effectively controlled, and the uniformity, reliability, and fatigue life of the ball screw are significantly improved. This invention is a green, efficient, easy-to-operate, high-performance, stable, and repeatable induction hardening heat treatment process suitable for continuous mass production.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, the following detailed description is provided in conjunction with preferred embodiments and accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0022] Figure 1 This is a schematic diagram of the induction hardening process of the ball screw according to the present invention;

[0023] Figure 2 This is a schematic diagram of the conformal hardening layer after induction hardening of the ball screw according to the present invention.

[0024] Figure 3 This is a microstructure diagram of the hardened layer of the GCr15 ball screw in Example 1;

[0025] Figure 4 This is a microstructure diagram of the hardened layer of the GCr15SiMn ball screw in Example 2;

[0026] Figure 5 This is a microstructure diagram of the hardened layer of the GCr15SiMn ball screw in Example 3. Detailed Implementation

[0027] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this specification. These embodiments illustrate the principles of the invention, and other aspects, features, and advantages of the invention will become apparent from this detailed description. In the accompanying drawings, the same or similar parts in different figures are indicated by the same reference numerals.

[0028] like Figures 1 to 5 As shown, this invention provides a dual-frequency induction hardening heat treatment method for high-carbon chromium bearing steel ball screws. The method utilizes induction hardening heat treatment technology to prepare a contour-hardened layer of a certain thickness on the surface of the ball screw. Specifically, it includes the following steps:

[0029] First, the surface of the high carbon chromium bearing steel ball screw is cleaned, rusted, and free of organic residues to achieve the required cleanliness level. Then, it is placed on the drive unit of the induction heat treatment equipment and clamped and positioned.

[0030] Based on the material, shape, size characteristics, and required hardened layer thickness of the ball screw, a corresponding machining program is set. The induction heat treatment equipment is then started, and the ball screw moves at a constant speed along its axial direction while simultaneously rotating, sequentially passing through the preheating inductor 10, the quenching inductor 20, and the quenching medium spray ring 30 to perform induction hardening heat treatment on the surface of the ball screw. The machining program is set by simulating and optimizing the shape and size of the preheating inductor 10 and the quenching inductor 20, the number of coil turns, the turn spacing, and the combination and matching relationships between various parameters.

[0031] The preheating inductor 10 and quenching inductor 20 of this invention are mainly composed of a coil, a cooling system, and an insulation system. The magnetic force distribution is controlled by the coil, thereby affecting the temperature field distribution of the ball screw. The quenching medium spray ring 30 is used to spray the quenching medium. By adjusting the type and flow rate of the quenching medium, the cooling rate of the ball screw is adjusted, so that the heated ball screw is uniformly quenched and cooled.

[0032] The diameter of the ball screw that this invention can handle is The parameter range of the preheating inductor 10 is: rated power of 20-150kW, voltage of 160-500V, current of 20-300A, and frequency of 1-20kHz; the parameter range of the quenching inductor 20 is: rated power of 50-200kW, voltage of 300-500V, current of 50-400A, and frequency of 20-100kHz; the distance between the preheating inductor 10 and the quenching inductor 20 is 100-120mm.

[0033] The ball screw has a moving speed of 6-15 mm / s, and its rotational speed = axial moving speed of the ball screw / lead of the ball screw.

[0034] The parameter range of the quenching medium spray ring 30 is as follows: the flow rate of the quenching medium is 100-800 L / min, and the spray holes 31 on the inner circumference of the quenching medium spray ring 30 are evenly distributed in a 5mm×5mm checkerboard pattern; the size of the spray holes 31 is selected according to the diameter of the ball screw. When the diameter of the ball screw is <15mm, the diameter of the spray holes 31 is 1-1.5mm; when the diameter of the ball screw is in the range of 15-38mm, the diameter of the spray holes 31 is 1.5-2.5mm; when the diameter of the ball screw is >38mm, the diameter of the spray holes 31 is 3.5-4mm.

[0035] The machining program is set via the control panel to configure the movement mode, speed, and rotation speed of the preheating inductor 10, quenching inductor 20, and ball screw, ensuring continuous and precise heating and cooling of the ball screw. After the induction hardening heat treatment is completed, induction heating and spraying of the quenching medium are stopped, and the machined high-carbon chromium bearing steel ball screw is removed.

[0036] The dual-frequency induction hardening heat treatment process, combining the preheating inductor 10 and the quenching inductor 20 of this invention, prepares a contour-hardened layer of a certain thickness on the surface of a high-carbon chromium bearing steel ball screw, while maintaining good toughness in the core matrix of the ball screw, thereby improving the wear resistance and fatigue life of the ball screw. The core of the ball screw is the part inside the ball screw that has not undergone surface heat treatment; this part retains its original microstructure and performance characteristics, such as toughness and strength. During the induction heat treatment process, by controlling the process parameters and heating temperature, the formation of the surface hardened layer can be ensured without significantly affecting the toughness of the core. The thickness of the contour-hardened layer formed on the surface of the ball screw after induction hardening heat treatment is adjustable within the range of 0.8–9.6 mm, with a hardness of 764–833 HV at the tooth tip and raceway, a hardness consistency of ≤1 HRC, and a deformation of ≤0.15 mm / m. Simultaneously, the core maintains good toughness, significantly improving wear resistance and fatigue life. The uniformity of hardened layer hardness refers to the characteristic that the hardness is uniform and consistent at the same depth from the surface, without any local over-hardness or under-softness.

[0037] Example 1:

[0038] According to the size specifications For a GCr15 ball screw with a lead of 5mm, the required hardened layer thickness is 0.5-1.0mm. The corresponding machining program is set, mainly including the parameters of the preheating inductor 10, the parameters of the quenching inductor 20, the number of coil turns, and the screw's movement mode and speed. First, the surface of the GCr15 ball screw is cleaned of dirt, rust, and organic residue. Then, it is placed on the drive unit of the induction heat treatment equipment. After automatic clamping and positioning, the induction heat treatment equipment is started according to the pre-set machining program. The ball screw performs axial linear motion while maintaining its rotation, with a moving speed of 15 mm / s and a rotation speed of 3 r / s. The parameters of the preheating inductor 10 are: double turns, turn spacing of 2 mm, inner diameter of 21 mm, coil cross-sectional dimensions of 7 mm × 7 mm, coil wall thickness of 1.5 mm, rated power of 20 kW, voltage of 160 V, current of 20 A, and frequency of 20 kHz. The parameters of the quenching inductor 20 are: double turns, turn spacing of 2 mm, inner diameter of 21 mm, coil cross-sectional dimensions of 7 mm × 7 mm, coil wall thickness of 1.5 mm, rated power of 50 kW, voltage of 300 V, current of 50 A, and frequency of 100 kHz. The distance between the preheating inductor 10 and the quenching inductor 20 is 100 mm, the quenching medium flow rate is 100 L / min, and the quenching medium is a 10% PAG solution.

[0039] After the induction hardening heat treatment of the entire ball screw is completed, induction heating and spray quenching medium are stopped, and the finished high-carbon chromium bearing steel ball screw is removed. Testing and analysis show that the thickness of the conformal hardened layer on the surface of the ball screw is 0.8 mm, the hardness of the tooth tip and raceway reaches 764 HV, the hardness consistency of the hardened layer is ≤1 HRC, the deformation is 0.15 mm / m, and the hardness of the core matrix is ​​597.1 HV. It still maintains good toughness, and its wear resistance and fatigue life are significantly improved.

[0040] Example 2:

[0041] According to the size specifications For a GCr15SiMn ball screw with a lead of 16mm, requiring a hardened layer thickness of 4.7–5.5mm, the corresponding machining program is set, mainly including the parameters of the preheating inductor 10, the parameters of the quenching inductor 20, the inductor spacing, the number of coil turns, the screw's movement mode and speed, etc. First, the surface of the GCr15SiMn ball screw is cleaned of dirt, rust, and organic residue. Then, it is placed on the drive unit of the induction heat treatment equipment. After automatic clamping and positioning, the induction heat treatment equipment is started according to the pre-set machining program. The ball screw performs axial linear motion while maintaining its rotation, with a moving speed of 10 mm / s and a rotation speed of 0.625 r / s. The parameters of the preheating inductor 10 are: 3 turns of coil, 4 mm turn spacing, 83 mm inner diameter, 12 mm × 12 mm coil cross-sectional dimensions, 1.5 mm coil wall thickness, 100 kW rated power, 380 V voltage, 210 A current, and 10 kHz frequency. (Quenching) The parameters of inductor 20 are as follows: the coil has two turns, the turn spacing is 4mm, the inner diameter of quenching inductor 20 is 83mm, the cross-sectional dimensions of the coil are 12mm×12mm, the wall thickness of the coil is 1.5mm, the rated power is 150kW, the voltage is 470V, the current is 310A, and the frequency is 50kHz; the distance between preheating inductor 10 and quenching inductor 20 is 110mm, the flow rate of the quenching medium is 350L / min, and the quenching medium is 10% PAG solution.

[0042] After the induction hardening heat treatment of the entire ball screw is completed, induction heating and spray quenching medium are stopped, and the finished high-carbon chromium bearing steel ball screw is removed. Testing and analysis show that the thickness of the conformal hardened layer on the surface of the ball screw is 5.2 mm, the hardness of the tooth tip and raceway reaches 833 HV, the hardness consistency of the hardened layer is ≤1 HRC, the deformation is 0.1 mm / m, and the hardness of the core matrix is ​​631.3 HV, while maintaining good toughness, significantly improved wear resistance and fatigue life.

[0043] Example 3:

[0044] According to the size specifications For a GCr15SiMn ball screw with a lead of 20 mm that requires a hardened layer thickness of 8 to 10 mm, a corresponding machining program is set, which mainly includes the parameters of the preheating inductor 10, the parameters of the quenching inductor 20, the distance between the inductors, the number of turns of the coils, the motion mode and speed of the screw, etc. First, the surface of the GCr15SiMn ball screw is cleaned to remove contaminants, rust and organic residues, then the ball screw is placed on the driving device of the induction heat treatment equipment. After automatic clamping and positioning, the induction heat treatment equipment is started in accordance with the pre-set machining program. The ball screw performs axial linear motion while maintaining rotation, with a moving speed of 6 mm / s and a rotation speed of 0.3 r / s; the parameters of the preheating inductor 10 are: the number of coil turns is 3, the turn spacing is 5 mm, the inner diameter of the preheating inductor 10 is 120 mm, the cross-sectional size of the coil is 10 mm×12 mm, the wall thickness of the coil is 2 mm, the rated power is 150 kW, the voltage is 500 V, the current is 300 A, and the frequency is 1 kHz; the parameters of the quenching inductor 20 are: the number of coil turns is 4, the turn spacing is 5 mm, the inner diameter of the quenching inductor 20 is 120 mm, the cross-sectional size of the coil is 10 mm×12 mm, the wall thickness of the coil is 2 mm, the rated power is 200 kW, the voltage is 500 V, the current is 400 A, and the frequency is 20 kHz; the distance between the preheating inductor 10 and the quenching inductor 20 is 120 mm, the flow rate of the quenching medium is 800 L / min, and the quenching medium is a 10% PAG solution.

[0045] After the induction quenching heat treatment of the entire ball screw is completed, the induction heating and the spraying of the quenching medium are stopped, and the finished high-carbon chromium bearing steel ball screw is taken out. Through testing and analysis, the thickness of the contoured hardened layer obtained on the surface of the ball screw is 9.6 mm, the hardness of the tooth crest and the raceway is as high as 805.2 HV, the hardness consistency of the hardened layer is ≤ 1 HRC, the deformation is 0.10 mm / m, the hardness of the core matrix is 626.5 HV, which still maintains good toughness, and the wear resistance and fatigue life are significantly improved.

[0046] The above is only the preferred embodiment of the present invention, and it certainly should not be used to limit the scope of the rights of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and variations can be made without departing from the principle of the present invention, and these improvements and variations shall also be regarded as falling within the protection scope of the present invention.

Claims

1. A method for dual-frequency induction hardening heat treatment of high-carbon chromium bearing steel ball screws, characterized in that, Includes the following steps: S1. Workpiece clamping and positioning: Place the cleaned high-carbon chromium bearing steel ball screw on the drive device of the induction heat treatment equipment and clamp and position it. S2. Induction hardening heat treatment of the workpiece: According to the material, shape, size characteristics of the ball screw and the required hardened layer thickness, the processing program is set, the induction heat treatment equipment is started, the ball screw moves at a constant speed along its axial direction and rotates at the same time, passing through the preheating inductor, the quenching inductor and the quenching medium spray ring in sequence to perform induction hardening heat treatment on the surface of the ball screw. The parameter range of the preheating inductor is: rated power of 20-150kW, voltage of 160-500V, current of 20-300A, and frequency of 1-20kHz. The parameter range of the quenching inductor is: rated power of 50-200kW, voltage of 300-500V, current of 50-400A, and frequency of 20-100kHz; the distance between the preheating inductor and the quenching inductor is 100-120mm. The ball screw has a moving speed of 6-15 mm / s, and its rotation speed = axial moving speed of the ball screw / lead of the ball screw. S3. After the induction hardening heat treatment is completed, stop the induction heating and spray quenching medium, and take out the finished high carbon chromium bearing steel ball screw.

2. The dual-frequency induction hardening heat treatment method for high-carbon chromium bearing steel ball screws as described in claim 1, characterized in that, In step S2, the parameter range of the quenching medium spray ring is as follows: the flow rate of the quenching medium is 100-800 L / min, and the spray holes on the inner circumference of the quenching medium spray ring for spraying the quenching medium are evenly distributed in a 5mm×5mm checkerboard pattern; wherein the size of the spray holes is selected according to the diameter of the ball screw. When the diameter of the ball screw is <15mm, the diameter of the spray hole is 1-1.5mm; when the diameter of the ball screw is in the range of 15-38mm, the diameter of the spray hole is 1.5-2.5mm; when the diameter of the ball screw is >38mm, the diameter of the spray hole is 3.5-4mm.

3. The dual-frequency induction hardening heat treatment method for high-carbon chromium bearing steel ball screws as described in claim 1, characterized in that, In step S2, the processing program is obtained by simulating and optimizing the shape and size of the preheating inductor and the quenching inductor, the number of turns of the coil, the turn spacing, and the combination and matching relationship between various parameters.

4. The dual-frequency induction hardening heat treatment method for high-carbon chromium bearing steel ball screws as described in claim 1, characterized in that, In step S3, the ball screw that has undergone induction hardening heat treatment has a surface hardening layer with a thickness of 0.8 to 9.6 mm, a tooth tip and groove hardness of 764 to 833 HV, a hardness uniformity of ≤1 HRC, and a deformation of ≤0.15 mm / m.

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