Wide-temperature-range ball screw pair and heat treatment preparation process thereof

Abstract

The present application relates to a kind of wide temperature range ball screw pair and its heat treatment preparation process, ball screw pair includes ball screw, ball nut, return device and ball, ball screw, ball nut and ball are all made of high-nitrogen stainless steel material, wherein the heat treatment step of ball screw includes steps S1-S3, step S1 quenching and tempering heat treatment, step S2 induction quenching, step S3 subsequent processing is carried out, finally obtained the temperature range for normal use of wide temperature range ball screw is-70~400 ℃;In addition, the heat treatment step of ball nut includes steps S4-S6, step S4 quenching and tempering heat treatment, step S5 is carried out vacuum quenching again, step S6 subsequent processing is carried out, finally obtained the temperature range for normal use of wide temperature range ball nut is-70~400 ℃.The wide temperature range ball screw pair and its heat treatment preparation process of the present application, solve the problem of the narrow temperature range of ball screw pair in the prior art, improve the carrying capacity, toughness and corrosion resistance of ball screw pair.

Description

Technical Field

[0001] This invention relates to the field of ball screw pairs and their heat treatment preparation processes, specifically to a ball screw pair suitable for a wide temperature range and its heat treatment preparation process. Background Technology

[0002] With the increasing demands for high speed, high load, high temperature resistance, corrosion resistance, and weight reduction in aviation and aerospace transmission systems, ball screw pairs and other transmission components, as one of the most important structural components of mechanical equipment, operate in extremely complex environments. Besides enduring alternating cyclic stress, corrosion, and wear, operating temperature is particularly critical. Especially with increased transmitted energy and speed, or insufficient lubrication, the contact surface temperature rises rapidly. Furthermore, they must operate under conditions of salt spray, dust, mold, and humid heat. To avoid malfunctions due to high temperatures and corrosion during use, premature replacement of transmission components is often necessary, severely impacting operational performance.

[0003] The materials and properties of transmission components such as ball screw assemblies are crucial factors restricting the performance, service life, and reliability of transmission systems. Therefore, improving and stabilizing the performance and quality of bearing steel is of great significance for enhancing the overall performance of rolling components such as bearings and screws in transmission systems, including their service life and reliability. Both domestic and international researchers are continuously developing and researching new materials and processes to improve and stabilize the metallurgical quality and performance of stainless bearing steel to meet its service requirements. Currently, high-nitrogen stainless steel is used to manufacture ball screw assemblies, but the operating temperature range after manufacturing these assemblies is generally -45°C to 200°C. However, with the increasing demands of military applications for ball screw assemblies, these operating temperatures are no longer sufficient. Furthermore, the performance and load-bearing capacity of existing ball screw assemblies are relatively poor. Therefore, it is necessary to develop ball screw assemblies with a wide temperature range. Summary of the Invention

[0004] The main objective of this invention is to provide a wide-temperature-range ball screw assembly and its heat treatment preparation process, which solves the problem of the narrow operating temperature range of ball screw assemblies in the prior art, and improves the load-bearing capacity, toughness and corrosion resistance of ball screw assemblies in the range of -70 to 400℃.

[0005] To achieve the above objectives, the wide-temperature-range ball screw assembly heat treatment manufacturing process of the present invention includes a ball screw assembly comprising a ball screw, a ball nut, a reversing device, and balls. The ball screw, ball nut, and balls are made of high-nitrogen stainless steel (40Cr15Mo2VN). The heat treatment steps for the ball screw are as follows:

[0006] Step S1, quenching and tempering heat treatment, includes two sub-steps: vacuum quenching and high-temperature tempering, as detailed below:

[0007] a. Vacuum quenching: The ball screw made of high-nitrogen stainless steel is heated to 815-825℃ at room temperature and held for 65-75 minutes. Then, it is quenched again at 995-1005℃ and held for 45-55 minutes. Finally, it is oil cooled.

[0008] b. High-temperature tempering: heating from room temperature to 715-725℃, holding for 175-185 minutes, and air cooling to obtain the ball screw substrate;

[0009] Step S2, induction hardening, the ball screw substrate obtained in step S1 is subjected to medium frequency induction hardening treatment.

[0010] Step S3, subsequent processing: The ball screw obtained in step S2 undergoes cryogenic treatment and tempering, as detailed below:

[0011] a. One-time deep cooling: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes;

[0012] b. First tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool;

[0013] c. Secondary cryogenic treatment: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes;

[0014] d. Secondary tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool;

[0015] The final ball screw is a wide-temperature-range ball screw, with a normal operating temperature range of -70 to 400℃.

[0016] Furthermore, in step S2, the specific requirements are as follows: use a ring inductor with a diameter of φ20.5, a current of 61A, an inverter frequency of 130KHz, an initial preheating time of 1s, an induction coil moving speed of 135mm / min, a lead screw rotation speed of 220 rpm, and continuous heating as the coil moves; the induction quenching water pressure is 0.18~0.22MPa, the water temperature is 15~30℃, and the quenching cooling medium is water.

[0017] Furthermore, the result of the tempering heat treatment in step S1 is that the hardness of the obtained ball screw matrix is ​​in the range of 28 to 32 HRC, and the surface hardness of the wide temperature range ball screw finally obtained in step S3 is in the range of 55 to 59 HRC, with a hardened layer depth of 2.0 to 3.0 mm and a core hardness of 28 to 32 HRC.

[0018] Furthermore, in the vacuum quenching step S1, the ball screw made of high-nitrogen stainless steel is heated to 820°C at room temperature and held for 70 minutes. Then, it is quenched again at 1000°C and held for 50 minutes. Finally, it is oil cooled. In the high-temperature tempering step, the ball screw is heated to 720°C at room temperature and held for 180 minutes, followed by air cooling.

[0019] Furthermore, in step S3, the first cryogenic treatment involves lowering the room temperature to -80°C and holding it for 180 minutes; the first tempering involves heating the room temperature to 460°C and holding it for 180 minutes, followed by air cooling; the second cryogenic treatment involves lowering the room temperature to -80°C and holding it for 180 minutes; the second tempering involves heating the room temperature to 460°C and holding it for 180 minutes, followed by air cooling.

[0020] Furthermore, in step S2, the material of the annular inductor in the induction hardening process is copper. The annular inductor has a hollow structure in the middle and a water outlet hole on one side surface.

[0021] Furthermore, the heat treatment steps for the ball nuts are as follows:

[0022] Step S4, quenching and tempering heat treatment, includes two sub-steps: vacuum quenching and high-temperature tempering, as detailed below:

[0023] a. Vacuum quenching: Heat the ball nut made of high-nitrogen stainless steel to 815-825℃ at room temperature and hold for 105-115 minutes. Then, continue quenching at 995-1005℃ and hold for 75-85 minutes. Finally, oil cool.

[0024] b. High-temperature tempering: heat to 735-745℃ at room temperature, hold for 175-185 minutes, and then air cool;

[0025] Step S5: Perform vacuum quenching again on the ball nut obtained in step S4. Heat to 795-805℃ at room temperature and hold for 40-50 minutes. Continue quenching at 1035-1045℃ and hold for 55-65 minutes. Then, oil cool.

[0026] Step S6, subsequent processing: The ball nut obtained in step S5 undergoes cryogenic treatment and tempering, as detailed below:

[0027] a. One-time deep cooling: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes;

[0028] b. First tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool;

[0029] c. Secondary cryogenic treatment: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes;

[0030] d. Secondary tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool;

[0031] The final ball nut is a wide-temperature-range ball nut, with a normal operating temperature range of -70 to 400℃.

[0032] Furthermore, the quenching and tempering heat treatment in step S4 results in a ball nut matrix hardness in the range of 25 to 29 HRC, and the wide-temperature-range ball nut hardness obtained in step S6 is in the range of 55 to 59 HRC.

[0033] In addition, the present invention also provides a wide temperature range ball screw assembly, including a ball screw, a ball nut, a reversing device, and balls. The ball screw, ball nut, and balls are all made of high-nitrogen stainless steel (40Cr15Mo2VN). The ball screw is obtained through the preparation process of steps S1 to S3 above. The surface hardness of the ball screw is in the range of 55 to 59 HRC, the hardened layer depth is 2.0 to 3.0 mm, the core hardness is 28 to 32 HRC, and the operating temperature range is -70 to 400℃.

[0034] In addition, the present invention also provides a wide temperature range ball screw assembly, including a ball screw, a ball nut, a reversing device, and balls. The ball screw, ball nut, and balls are all made of high-nitrogen stainless steel (40Cr15Mo2VN). The ball nut is obtained through the preparation process of steps S4 to S6. The hardness of the ball nut is in the range of 55 to 59 HRC, and the working temperature range is -70 to 400℃.

[0035] Through the above technical solution, the beneficial effects of the present invention include: the wide-temperature-range ball screw assembly of the present invention includes a ball screw, a ball nut, a reversing device, and balls, wherein the ball screw, ball nut, and balls are all made of high-nitrogen stainless steel (40Cr15Mo2VN). Only when the hardness of the ball screw matrix formed after tempering heat treatment is within a suitable range, followed by induction hardening and subsequent treatment, and the hardness of the ball nut matrix formed after tempering heat treatment is within a suitable range, followed by vacuum quenching and subsequent treatment, can a wide-temperature-range ball screw assembly be obtained. This allows it to adapt to a wider range of working environments, improving the load-bearing capacity, wear resistance, and corrosion resistance of the ball screw assembly. Furthermore, the ball screw assembly of the present invention has high resistance to sliding wear and low austenite content; the low austenite content ensures dimensional stability. Attached Figure Description

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0037] Figure 1 This is a high-temperature load test curve of Embodiment 1 of the wide-temperature-range ball screw pair of the present invention.

[0038] Figure 2 This is a low-temperature load test curve of Embodiment 1 of the wide-temperature-range ball screw pair of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Example 1

[0041] In this embodiment, the ball screw assembly includes a ball screw, a ball nut, a reversing device, and balls. The ball screw, ball nut, and balls are all made of high-nitrogen stainless steel (40Cr15Mo2VN). The heat treatment steps for the ball screw are as follows: Step S1, tempering heat treatment, includes two sub-steps: vacuum quenching and high-temperature tempering, specifically: a. Vacuum quenching: The ball screw made of high-nitrogen stainless steel (40Cr15Mo2VN) is heated from room temperature to 820°C and held for 70 minutes, then further quenched at 1000°C for 50 minutes, and finally oil-cooled; b. High-temperature tempering: Heated from room temperature to 720°C and held for 180 minutes, then air-cooled to obtain the ball screw base. Step S2, induction hardening: The ball screw substrate obtained in step S1 is subjected to medium-frequency induction hardening. Specific requirements include using a ring inductor with a diameter of φ20.5, a current of 61A, an inverter frequency of 130kHz, initial preheating of 1s, an induction coil moving speed of 135mm / min, a screw rotation speed of 220 rpm, and continuous heating as the coil moves. The induction hardening water pressure is 0.18–0.22MPa, the water temperature is 15–30℃, and the quenching cooling medium is water. The ring inductor in this step is made of copper, has a hollow structure in the middle, and has a water outlet on one side. Step S3, subsequent processing: The ball screw obtained in step S2 undergoes cryogenic treatment and tempering, as detailed below:

[0042] a. One deep cryogenic treatment: The room temperature is lowered to -80°C, and the holding time is 180 minutes;

[0043] b. First tempering: Heat to 460℃ at room temperature, hold for 180 minutes, and air cool;

[0044] c. Secondary cryogenic treatment: The room temperature is lowered to -80℃, and the holding time is 180 minutes;

[0045] d. Secondary tempering: Heat to 460℃ at room temperature, hold for 180 minutes, and air cool;

[0046] The final high-nitrogen stainless steel (40Cr15Mo2VN) ball screw is a wide-temperature-range ball screw with a surface hardness of 55-59 HRC, a hardened layer depth of 2.0-3.0 mm, a core hardness of 28-32 HRC, and a normal operating temperature range of -70 to 400℃.

[0047] Comparative Example 1

[0048] In this comparative example, the ball screw assembly includes a ball screw, a ball nut, a reversing device, and balls. The processing steps of the ball screw are as follows: Step S1, tempering heat treatment, including two sub-steps: vacuum quenching and high-temperature tempering, specifically: a. Vacuum quenching: the ball screw made of high-nitrogen stainless steel is heated from room temperature to 1000℃, held for 70 minutes, and then oil-cooled; b. High-temperature tempering: the ball screw is heated from room temperature to 600℃, held for 120 minutes, and then air-cooled to obtain the ball screw base. It is then tempered again at room temperature of 580℃ for 120 minutes and then air-cooled; Step S2, induction hardening: the ball screw base obtained in Step S1 is subjected to medium-frequency induction hardening treatment, with the specific requirements being the same as in Example 1; Step S3, subsequent processing is also the same as the processing steps in Example 1. The ball screw obtained in the end has a normal operating temperature range of -55℃ to 300℃.

[0049] Comparative Example 2

[0050] In this comparative example, the ball screw assembly includes a ball screw, a ball nut, a reversing device, and balls. The heat treatment steps for the ball screw are as follows: Step S1, quenching and tempering heat treatment, the same as the process in Example 1; Step S2, medium-frequency induction hardening treatment: the high-nitrogen stainless steel ball screw treated in Step S1 is subjected to medium-frequency induction hardening treatment, the same as the process in Example 1; Step S3, subsequent treatment: the ball screw treated in Step S2 is subjected to low-temperature treatment and tempering treatment, the specific steps of which are as follows:

[0051] a. One deep cryogenic treatment: The room temperature is lowered to -80℃, and the holding time is 120 minutes;

[0052] b. First tempering: Heat to 200°C at room temperature, hold for 180 minutes, and air cool;

[0053] c. Secondary cryogenic treatment: The room temperature is lowered to -80℃, and the holding time is 120 minutes;

[0054] d. Secondary tempering: Heat to 200℃ at room temperature, hold for 180 minutes, and air cool; the normal operating temperature range of the ball screw obtained in this comparative example is -45 to 220℃.

[0055] Example 2

[0056] In this embodiment, the ball screw assembly includes a ball screw, a ball nut, a reversing device, and balls. The heat treatment steps for the ball nut made of high-nitrogen stainless steel (40Cr15Mo2VN) are as follows: Step S4, tempering heat treatment, including two sub-steps: vacuum quenching and high-temperature tempering, specifically as follows: a. Vacuum quenching: The ball nut made of high-nitrogen stainless steel is heated to 820°C at room temperature and held for 110 minutes. The quenching temperature is then increased to 1000°C and held for an additional time. a. Oil cooling for 80 minutes; b. High-temperature tempering: heat to 740℃ at room temperature, hold for 180 minutes, and air cool; Step S5: Vacuum quenching again: vacuum quench the ball nut obtained in Step S4, heat to 800℃ at room temperature, hold for 45 minutes, then continue quenching at 1040℃ for 60 minutes, and then oil cooling; Step S6: Subsequent processing: deep cryogenic treatment and tempering treatment are performed on the ball nut obtained in Step S5, as follows:

[0057] a. One deep cryogenic treatment: The room temperature is lowered to -80°C, and the holding time is 180 minutes;

[0058] b. First tempering: Heat to 460℃ at room temperature, hold for 180 minutes, and air cool;

[0059] c. Secondary cryogenic treatment: The room temperature is lowered to -80℃, and the holding time is 180 minutes;

[0060] d. Secondary tempering: Heat to 460℃ at room temperature, hold for 180 minutes, and air cool;

[0061] The high-nitrogen stainless steel (40Cr15Mo2VN) ball nuts obtained are wide-temperature-range ball nuts with a hardness in the range of 55 to 59 HRC and a normal operating temperature range of -70 to 400℃.

[0062] Comparative Example 3

[0063] In this comparative example, the ball screw assembly includes a ball screw, a ball nut, a reversing device, and balls. The heat treatment steps for the ball nut are as follows: Step S4, tempering heat treatment, including two sub-steps: vacuum quenching and high-temperature tempering, which is the same as the process in Example 2; Step S5, vacuum quenching is performed again on the ball screw substrate obtained in Step S4. The substrate is heated to 800°C at room temperature and held for 45 minutes. The quenching temperature is then increased to 1000°C and held for 60 minutes, followed by oil cooling; Step S6, subsequent processing is also the same as the processing steps in Example 2. The ball nut obtained at the end has a normal operating temperature range of -55°C to 300°C.

[0064] Comparative Example 4

[0065] In this comparative example, the ball screw assembly includes a ball screw, a ball nut, a reversing device, and balls. The heat treatment steps for the ball nut are as follows: Step S4, tempering heat treatment, including two sub-steps: vacuum quenching and high-temperature tempering, which is the same as the process in Example 2; Step S5, vacuum quenching treatment again: the ball nut treated in step S4 is subjected to vacuum quenching treatment, which is the same as the process in Example 2; Step S6, subsequent treatment: the ball nut treated in step S5 is subjected to low-temperature treatment and tempering treatment, the specific steps of which are as follows:

[0066] a. One deep cryogenic treatment: The room temperature is lowered to -80℃, and the holding time is 120 minutes;

[0067] b. First tempering: Heat to 200°C at room temperature, hold for 180 minutes, and air cool;

[0068] c. Secondary cryogenic treatment: The room temperature is lowered to -80℃, and the holding time is 120 minutes;

[0069] d. Secondary tempering: Heat to 200℃ at room temperature, hold for 180 minutes, and air cool; the normal operating temperature range of the ball nut obtained in this comparative example is -45 to 220℃.

[0070] Experimental testing:

[0071] The ball screw pairs obtained in the above embodiments and comparative examples were subjected to low-temperature and high-temperature axial static load tests. The static load testing equipment in this invention is a microcomputer-controlled electronic universal testing machine (manufactured by Zhongluchang Testing Machine Manufacturing Co., Ltd.). The specific steps are as follows:

[0072] The high-temperature static load test equipment is equipped with a special high-temperature test chamber. Through the high-temperature load test fixture, an axial static load is applied to the upper end face of the ball nut.

[0073] (1) High-temperature loading test method: The temperature was raised from room temperature to 400℃ and held for 120 minutes before starting the high-temperature loading test. The ball screw pair was placed vertically, and a load of 10KN was applied and held for 10 seconds. The load was then increased to 19.4KN and held for 10 seconds. The load was then increased to 25KN and held for 10 seconds before unloading. The load-bearing test curve of Example 1 is shown in [reference needed]. Figure 1 .

[0074] According to the process requirements of the high temperature loading test, the test piece was quickly removed from the high temperature chamber after the test. First, the smooth operation of the ball screw pair under high temperature conditions was checked. After the test piece temperature dropped to room temperature, the key interface dimensions and geometric tolerances of the ball screw pair were checked. After disassembly and cleaning, the surface quality of the raceway of the ball screw and ball nut was checked. The stroke accuracy of the screw was checked. After the original components were reassembled, the preload torque of the screw pair was checked.

[0075] The results of multiple high-temperature load tests on the various embodiments and comparative examples show that only the ball screws and ball nuts in Examples 1 and 2 have good smooth operation at 400℃, which meets the requirements. That is, the changes in external dimensions and form and position tolerances are very small, the stroke accuracy of the ball screw and the change in the preload torque of the screw pair are small, and the surface quality of the thread raceway of the screw and nut is good after the high-temperature load test. All the above indicators meet the design requirements, and their actual load capacity at 400℃ is ≥25KN, which is much higher than the theoretical calculation value of 19.4KN.

[0076] (2) Low-temperature loading test method:

[0077] The low-temperature static load test equipment is a microcomputer-controlled electronic universal testing machine. It is a modification of the aforementioned high-temperature test chamber, incorporating a liquid nitrogen cooling device to cool the temperature to -70°C. After holding at this temperature for 120 minutes, a low-temperature loading test is initiated. All other equipment remains unchanged. An axial static load is applied to the upper end face of the ball screw pair, and the test method is consistent with the high-temperature loading test. The load-bearing test curve obtained using the aforementioned low-temperature loading test method in Example 1 is shown below. Figure 2 .

[0078] According to the process requirements of the low temperature loading test, the test piece was quickly taken out of the low temperature chamber after the test. First, the smooth operation of the ball screw pair under low temperature conditions was checked. After the temperature of the test piece was raised to room temperature, the key interface dimensions and geometric tolerances of the ball screw pair were checked. After disassembly and cleaning, the surface quality of the screw and nut raceway was checked, the stroke accuracy of the screw was checked, and the preload torque of the screw pair was checked after the original components were reassembled.

[0079] The results of multiple low-temperature load tests on the embodiments and comparative examples show that only the ball screws and ball nuts in Examples 1 and 2 have good smooth operation at -70℃, which meets the requirements. That is, the changes in external dimensions and form and position tolerances are very small, the stroke accuracy of the ball screw and the change in the preload torque of the screw pair are small, and the surface quality of the thread raceway of the screw and nut is good after the low-temperature load test. All the above indicators meet the design requirements, and their actual load capacity at -70℃ is ≥25KN, which is much higher than the theoretical calculated value of 19.4KN.

[0080] High and low temperature load tests show that the theoretically calculated rated static load Coa of the high-nitrogen stainless steel (40Cr15Mo2VN) ball screw pairs in Examples 1 and 2 of this invention is 19.4KN. Under high temperature (400℃) and low temperature (-70℃) conditions, the load is ≥25KN, nearly 30% higher than the theoretical calculation value. This demonstrates that the wide-temperature-range ball screw pairs obtained through the heat treatment process of this invention can significantly improve load-bearing capacity while meeting the wide temperature range of -70 to 400℃. Under the same load requirements, the volume and weight of the screw product can be reduced, thereby reducing energy consumption and playing an important role in the spatial optimization of the entire servo mechanism.

[0081] In addition, the results of other performance tests on the ball screw pairs obtained after heat treatment in the above embodiments and comparative examples are analyzed as follows:

[0082] Table 1 Comparison of test results for each embodiment and comparative example

[0083]

[0084] Since the hardness test of ball screws or ball nuts is a test of the compressive strength of different parts and positions in the component structure, the hardness values ​​in the above test results are range values. This is hereby noted.

[0085] Firstly, analysis of the experimental results from Example 1, Comparative Examples 1 and 2 shows that in the heat treatment of ball screws, after tempering, the hardness of the ball screw matrix is ​​in the range of 28–32 HRC. After subsequent induction hardening and heat treatment, the hardness of the obtained ball screw is in the range of 55–59 HRC, and the hardened layer depth is in the range of 2.0–3.0 mm. The ball screw obtained at this time possesses a certain degree of toughness. However, changing the tempering heat treatment process in step S1 or the subsequent heat treatment process in step S3 will result in the final ball screw matrix hardness not being in the range of 28–32 HRC, or the final ball screw surface hardness not being in the range of 55–59 HRC, or the hardened layer depth not being in the hardness range of 2.0–3.0 mm. From an overall analysis, the normal operating time and suitable ambient temperature of the ball screw are significantly reduced, and the dimensional changes are quite noticeable. If the hardness is higher or lower than the specified range, the wide-temperature-range ball screw required by this application cannot be obtained. Furthermore, excessively high hardness of the screw matrix reduces the material's toughness, increasing the risk of screw breakage under impact and vibration. Therefore, the ball screw processed in Example 1, after tempering heat treatment, has a matrix hardness in the range of 28–32 HRC. After induction hardening and subsequent treatment, the hardness of the ball screw is in the range of 55–59 HRC, and the hardened layer depth is in the range of 2.0–3.0 mm. Under these conditions, the ball screw can meet the requirements for normal operation for over 120 minutes within a wide temperature range of -70 to 400℃, with minimal dimensional changes, fully satisfying the usage requirements of this component.

[0086] Secondly, referring to the experimental results of Example 2, Comparative Examples 3 and 4, it can also be seen that in the heat treatment process of ball nuts, after step S4 tempering heat treatment, step S5 vacuum quenching and step S6 subsequent treatment, only when the hardness of the ball nut obtained after tempering is in the range of 25 to 29 HRC, and the hardness of the final ball nut is in the range of 55 to 59 HRC, can it achieve a normal continuous working time of more than 120 minutes under temperature environment of -70 to 400℃ and with small dimensional changes, and the actual static load it bears exceeds the theoretical calculated load by about 30%, thus possessing high load-bearing capacity.

[0087] In summary, differences in heat treatment processes can lead to variations in the operating temperature, operating time, and dimensional changes of ball screws and ball nuts, affecting the overall performance of the product. The high-nitrogen stainless steel (40Cr15Mo2VN) ball screw assembly processed using the heat treatment process described in this invention can maintain normal operation and continuous use, especially in harsh environments of extremely low and high temperatures. This solves the usage requirements of military servo mechanisms in a wide temperature range of -70℃ to 400℃, while further improving the load-bearing capacity, contact fatigue life, toughness, and corrosion resistance of the ball screw assembly.

[0088] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A heat treatment process for a wide-temperature-range ball screw assembly, wherein the ball screw assembly includes a ball screw, a ball nut, a reversing device, and balls, and the ball screw, ball nut, and balls are made of high-nitrogen stainless steel, characterized in that, The heat treatment steps for the ball screw are as follows: Step S1, quenching and tempering heat treatment, includes two sub-steps: vacuum quenching and high-temperature tempering, as detailed below: a. Vacuum quenching: The ball screw made of high-nitrogen stainless steel is heated to 815-825℃ at room temperature and held for 65-75 minutes. Then, it is quenched again at 995-1005℃ and held for 45-55 minutes. Finally, it is oil cooled. b. High-temperature tempering: heating from room temperature to 715-725℃, holding for 175-185 minutes, and air cooling to obtain the ball screw substrate; Step S2, induction hardening, the ball screw substrate obtained in step S1 is subjected to medium frequency induction hardening treatment. Step S3, subsequent processing: The ball screw obtained in step S2 undergoes cryogenic treatment and tempering, as detailed below: a. One-time deep cooling: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes; b. First tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool; c. Secondary cryogenic treatment: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes; d. Secondary tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool; The final ball screw obtained is a wide temperature range ball screw, with a normal operating temperature range of -70 to 400℃; In step S2, the specific requirements are as follows: use a ring inductor with a diameter of φ20.5, a current of 61A, an inverter frequency of 130KHz, an initial preheating time of 1s, an induction coil moving speed of 135mm / min, a lead screw rotation speed of 220 rpm, and continuous heating as the coil moves; the induction quenching water pressure is 0.18~0.22MPa, the water temperature is 15~30℃, and the quenching cooling medium is water; The result of the quenching and tempering heat treatment in step S1 is that the hardness of the obtained ball screw matrix is ​​in the range of 28 to 32 HRC, and the surface hardness of the wide temperature range ball screw finally obtained in step S3 is in the range of 55 to 59 HRC, with a hardened layer depth of 2.0 to 3.0 mm and a core hardness of 28 to 32 HRC. In step S2, the material of the annular inductor in the induction hardening process is copper. The annular inductor has a hollow structure in the middle and a water outlet hole on one side surface.

2. The heat treatment preparation process for the wide-temperature-range ball screw pair according to claim 1, characterized in that, In the vacuum quenching step of step S1, the ball screw made of high-nitrogen stainless steel is heated to 820°C at room temperature and held for 70 minutes. Then, it is quenched again at 1000°C and held for 50 minutes. Finally, it is oil cooled. In the high-temperature tempering step, the ball screw is heated to 720°C at room temperature and held for 180 minutes. Then, it is air cooled.

3. The heat treatment preparation process for the wide-temperature-range ball screw pair according to claim 1, characterized in that, In step S3, the first cryogenic cooling involves lowering the room temperature to -80°C and holding it for 180 minutes; the first tempering involves heating the room temperature to 460°C and holding it for 180 minutes, followed by air cooling; the second cryogenic cooling involves lowering the room temperature to -80°C and holding it for 180 minutes; the second tempering involves heating the room temperature to 460°C and holding it for 180 minutes, followed by air cooling.

4. The heat treatment preparation process for wide-temperature-range ball screw pairs according to any one of claims 1 to 3, characterized in that, The heat treatment steps for the ball nut are as follows: Step S4, quenching and tempering heat treatment, includes two sub-steps: vacuum quenching and high-temperature tempering, as detailed below: a. Vacuum quenching: Heat the ball nut made of high-nitrogen stainless steel to 815-825℃ at room temperature and hold for 105-115 minutes. Then, continue quenching at 995-1005℃ and hold for 75-85 minutes. Finally, oil cool. b. High-temperature tempering: heat to 735-745℃ at room temperature, hold for 175-185 minutes, and then air cool; Step S5: Perform vacuum quenching again on the ball nut obtained in step S4. Heat to 795-805℃ at room temperature and hold for 40-50 minutes. Continue quenching at 1035-1045℃ and hold for 55-65 minutes. Then, oil cool. Step S6, subsequent processing: The ball nut obtained in step S5 undergoes cryogenic treatment and tempering, as detailed below: a. One-time deep cooling: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes; b. First tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool; c. Secondary cryogenic treatment: The room temperature is lowered to -85 to -75°C, and the holding time is 175 to 185 minutes; d. Secondary tempering: Heat to 455-465℃ at room temperature, hold for 175-185 minutes, and air cool; The final ball nut is a wide-temperature-range ball nut, with a normal operating temperature range of -70 to 400℃.

5. The heat treatment preparation process for the wide-temperature-range ball screw pair according to claim 4, characterized in that, The result of the tempering heat treatment in step S4 is that the hardness of the obtained ball nut matrix is ​​in the range of 25 to 29 HRC, and the hardness of the wide temperature range ball nut finally obtained in step S6 is in the range of 55 to 59 HRC.

6. A wide-temperature-range ball screw assembly, comprising a ball screw, a ball nut, a reversing device, and balls, wherein the ball screw, ball nut, and balls are all made of high-nitrogen stainless steel, characterized in that, The ball screw is obtained by the manufacturing process described in claim 1. The surface hardness of the ball screw is in the range of 55 to 59 HRC, the depth of its hardened layer is 2.0 to 3.0 mm, the core hardness is 28 to 32 HRC, and the operating temperature range is -70 to 400℃.

7. A wide-temperature-range ball screw assembly, comprising a ball screw, a ball nut, a reversing device, and balls, wherein the ball screw, ball nut, and balls are all made of high-nitrogen stainless steel, characterized in that, The ball nut is obtained by the manufacturing process described in claim 4, and the hardness of the ball nut is in the range of 55 to 59 HRC, and the working temperature range is -70 to 400℃.

Images