A type of round steel wire for wire thread inserts, quenching process, and wire thread insert.

Abstract

This invention discloses a round steel wire for wire thread inserts, a quenching process, and a preparation method. The chemical composition of the round steel wire, by weight percentage, includes: 0.10–0.22% C, 10.0–13.5% Cr, 0.50–0.60% Si, 0.30–0.35% Mn, 0.15–0.25% Ni, 0.01–0.03% Mo, 0.15–0.20% Cu, 0.005–0.007% Ti, 0.001–0.002% S, 0.025–0.035% P, 0.001–0.002% Al, 0.085–0.090% V, 0.008–0.012% Co, and 0.008–0.012% Nb, with the balance being Fe and unavoidable impurities. The quenching process involves pretreatment of the aforementioned round steel wire with hot-rolled wire rod, austenitization treatment, primary quenching, redistribution treatment, secondary quenching, and drawing. This invention improves the strength, wear resistance, and fatigue resistance of the round steel wire, and is suitable for the preparation of high-strength steel wire threaded inserts.

Description

Technical Field

[0001] This invention relates to the field of steel materials, specifically to a round steel wire for wire thread inserts, a quenching process, and a wire thread insert. Background Technology

[0002] Wire thread inserts, as high-performance fasteners, have significant application value in aerospace, automotive manufacturing, precision machinery, and electronic equipment, especially in high-strength connectors and vibration-resistant equipment, where their performance directly affects product reliability and service life. As the core material of wire thread inserts, round steel wire needs to possess excellent strength, wear resistance, and fatigue resistance to withstand high-intensity mechanical loads and long-term dynamic fatigue in complex environments. In aerospace, wire thread inserts are used for high-strength threaded connections in critical components, requiring the round steel wire to maintain stable performance under extreme temperatures and high vibration environments. In automotive manufacturing, wire thread inserts must withstand continuous vibration and stress cycles, necessitating high strength and excellent fatigue resistance to prevent failure. In precision machinery, wear resistance is crucial to ensure consistent performance during frequent assembly and disassembly. These applications place extremely high demands on the performance of round steel wire used in wire thread inserts, particularly the optimal balance between strength, wear resistance, and fatigue resistance, which directly impacts the overall performance and service life of the product. Meeting these performance requirements can not only significantly improve the reliability of wire thread inserts in high-end applications, but also broaden their application range in extreme environments, promote technological innovation and industry progress in fastener materials, and thus provide strong guarantees for the safety and service life of high-performance machinery and equipment.

[0003] Currently, research and development on round steel wire for wire thread inserts has made some progress, but there are still significant shortcomings in meeting the comprehensive requirements of high strength, wear resistance, and fatigue resistance. For example, Chinese patent CN201982456U discloses a wire thread insert, but the patent does not involve any measures to strengthen the microstructure of the material. However, in practical applications, it still faces the problem of balancing high strength and fatigue resistance, especially the tendency to fail under high stress cycling conditions, which limits its use in high-end equipment. The main reason for these shortcomings is that existing processes have limited ability to control the microstructure of materials, especially in terms of grain refinement, precipitate distribution, and interface characteristic optimization, making it difficult to achieve precise control and simultaneously meet the balance requirements of strength, wear resistance, and fatigue resistance. In addition, the existing processes have imperfect mechanisms for controlling residual stress and dislocation density during heat treatment, resulting in rapid performance degradation of the material under dynamic loads. Therefore, developing a quenching process for round steel wire used in wire thread inserts that can optimize the microstructure of materials and improve their overall performance through refined process design has become a key research direction for solving technical problems in the industry, improving product reliability, and expanding the scope of applications. Summary of the Invention

[0004] The purpose of this invention is to provide a round steel wire for wire thread inserts, a quenching process, and a wire thread insert, thereby solving the problems of insufficient strength, wear resistance, and fatigue resistance of the round steel wire used in wire thread inserts.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A round steel wire for wire thread inserts, wherein the chemical composition of the round steel wire comprises, by weight percentage: 0.10–0.22% C, 10.0–13.5% Cr, 0.50–0.60% Si, 0.30–0.35% Mn, 0.15–0.25% Ni, 0.01–0.03% Mo, 0.15–0.20% Cu, 0.005–0.007% Ti, 0.001–0.002% S, 0.025–0.035% P, 0.001–0.002% Al, 0.085–0.090% V, 0.008–0.012% Co, 0.008–0.012% Nb, with the balance being Fe and unavoidable impurities.

[0007] Furthermore, the round steel wire used for the steel wire threaded insert contains deformed twins with an average width of 30–65 nm and an average density of 1.1 × 10¹²–3.5 × 10¹² cm⁻².

[0008] The round steel wire used for the steel wire threaded sleeve contains a short rod-shaped Ni3(Ti,Al) precipitate phase, the average width of which is 5.0-15 nm and the average length is 50-145 nm.

[0009] Furthermore, the short rod-shaped Ni(Ti,Al) precipitate phase in the round steel wire used for the steel wire thread sleeve is dispersedly distributed within the matrix grains, with a spacing of 20–50 nm.

[0010] The interface between the Ni3(Ti,Al) precipitate and the α-Fe in the matrix is ​​a semi-coherent interface; the interface mismatch is 1.5% to 3.0%.

[0011] Furthermore, the dislocation density of the round steel wire used for the steel wire threaded insert is 5.0×10¹⁴~1.0×10¹⁵m⁻².

[0012] The matrix grains of the round steel wire used for the steel wire thread insert are refined to an average grain size of 1.5 to 3.0 μm after redistribution treatment, and the grains exhibit {111} texture characteristics.

[0013] In the round steel wire used for the steel wire threaded sleeve, the residual compressive stress distribution at the interface between the Ni(Ti,Al) precipitate phase and the α-Fe matrix ranges from 200 to 400 MPa.

[0014] Furthermore, the ratio of large-angle grain boundaries to small-angle grain boundaries in the round steel wire used for the wire thread insert is (55-70):(30-45).

[0015] This invention also provides a quenching process for round steel wire used in wire thread inserts, comprising the following steps:

[0016] S1: Pre-treat the hot-rolled wire rod of round steel to remove surface impurities;

[0017] S2: The round steel wire obtained after step S1 is subjected to austenitizing treatment to obtain austenitic wire rod.

[0018] S3: The austenitic wire rod is subjected to initial quenching treatment to obtain a martensitic wire rod.

[0019] S4: The martensitic wire rod is sequentially redistributed and quenched to obtain the finished round steel wire for wire thread sleeves.

[0020] S5: The finished round steel wire for the wire thread insert is drawn to obtain the round steel wire for the wire thread insert.

[0021] Further, the pretreatment process in step S1 is as follows: the hot-rolled wire rod of round steel wire is placed in a pickling tank, 10wt.% dilute nitric acid solution is added, and stirring is maintained for 5 to 10 minutes to remove the surface oxide scale by pickling. After pickling, the hot-rolled wire rod is rinsed 3 times with deionized water, and the rinsed hot-rolled wire rod is placed in a hot air drying oven at 70 to 80°C and dried for 30 to 60 minutes.

[0022] Further, the austenitizing process in step S2 is as follows: the pretreated hot-rolled wire rod is placed in a heating furnace and heated to 1100-1150°C at a heating rate of 5-10°C / min, and held for 3.0-5.0 min to complete the austenitizing process and obtain austenitic wire rod.

[0023] Furthermore, the initial quenching process in step S3 is as follows: the austenitic wire rod obtained in step S2 is placed in an oil bath at 180-200°C for quenching, and held in the oil bath for 60-70 seconds to obtain a martensitic wire rod.

[0024] Furthermore, the secondary quenching process of S4 is as follows: the martensitic wire rod is placed in a salt bath at 420-450°C and kept at that temperature for 30-60 minutes to complete the redistribution process, followed by room temperature water quenching to obtain the finished round steel wire for wire thread inserts.

[0025] Furthermore, the drawing process in step S5 is as follows: the surface of the finished round steel wire for wire thread insert is coated with lubricant, and then drawn through 3 to 5 passes, with a deformation of 5 to 10% in each pass, to finally obtain the round steel wire for wire thread insert.

[0026] This invention employs a multi-step quenching process primarily designed to enhance the strength, wear resistance, and fatigue resistance of round steel wire used in wire thread inserts. Through precise control of the quenching process, significant improvements in material properties are achieved. The core of the quenching process lies in the synergistic effect of austenitization, initial quenching, redistribution treatment, and secondary quenching to optimize the material's microstructure and phase structure. In the austenitization stage, the material is heated to 1100–1150℃ at a uniform heating rate of 5–10℃ / min, ensuring the complete dissolution of carbides and the formation of a uniform austenitic structure. This provides an ideal microstructure basis for subsequent quenching transformation. Simultaneously, short-term holding inhibits grain growth, thereby improving the material's toughness. In the initial quenching process, the austenitic wire rod is rapidly quenched into an oil bath at 180–200℃ and held for 60–70 seconds, transforming austenite into martensite. This significantly improves the material's hardness and strength. Simultaneously, precise control of the cooling rate reduces thermal stress and the formation of internal cracks. The redistribution treatment and secondary quenching involve placing the martensitic wire rod in a molten salt bath at 420–450°C for 30–60 minutes followed by rapid water quenching. This process refines the grains to further enhance strength and induces the formation of dispersed precipitates (such as Ni(Ti,Al)) within the matrix grains, significantly improving the material's wear resistance and fatigue resistance. Furthermore, this redistribution treatment stabilizes retained austenite, optimizes the material's toughness, and enhances its dynamic load-bearing capacity. The entire quenching process, through multi-stage cooling and phase transformation control, achieves a synergistic effect of grain refinement and precipitation strengthening. It also ensures the long-term stability and reliability of the material under high-strength and complex service conditions by releasing residual stress and improving microstructure uniformity. Finally, drawing further enhances the dislocation density and surface compactness of the material, optimizing wear resistance and fatigue resistance while meeting strength requirements, thus comprehensively meeting the performance requirements of wire thread inserts in high-load, high-vibration, and dynamic fatigue environments.

[0027] This invention employs a multi-component alloy design and a refined quenching process primarily to enhance the strength, wear resistance, and fatigue resistance of round steel wire for wire thread inserts. By controlling the material's microstructure, a multi-scale strengthening mechanism is constructed, achieving a comprehensive performance improvement. The chemical composition design of the round steel wire emphasizes the synergistic effects of elements such as C, Cr, Ni, and Ti. Precise control of the C content provides a basis for carbide precipitation while ensuring the stability of austenite during austenitization. The addition of Cr and Ni significantly improves the material's corrosion resistance and hardenability. Ti and Al, through the formation of short rod-shaped Ni(Ti,Al) precipitates with Ni, further enhance the precipitation strengthening effect. Through optimization of the quenching process, the matrix grains are refined to 1.5–3.0 μm, exhibiting a stable {111} texture. This texture optimization not only improves the material's strength and plasticity matching but also significantly enhances its fatigue resistance. Furthermore, the deformed twins formed during quenching are distributed with a width of 30–65 nm. Their high density provides an effective barrier to dislocation movement, thereby further strengthening the matrix. The increase in dislocation density to 5.0 × 10¹⁴–1.0 × 10¹⁵ m⁻² enhances the overall strength and durability of the material through a dislocation strengthening mechanism. Short rod-shaped Ni(Ti,Al) precipitates exist in a dispersed form within the matrix grains, with a spacing controlled at 20–50 nm. The semi-coherent interface formed between the precipitates and the α-Fe matrix has a mismatch degree of 1.5%–3.0%. This interface characteristic ensures the bonding strength between the precipitates and the matrix while effectively hindering dislocation movement, thus achieving a synergistic improvement in strength and plasticity. At the same time, the distribution of the Ni(Ti,Al) precipitates introduces residual compressive stress of 200–400 MPa. This compressive stress plays an important role in resisting fatigue crack propagation, providing a significant advantage in the material's fatigue resistance. Through redistribution treatment and secondary quenching, the grain boundary characteristics of the material are optimized, with the ratio of large-angle grain boundaries to small-angle grain boundaries controlled at (55–70):(30–45). This grain boundary distribution not only enhances the coordination of grain boundary slip but also improves the stress distribution capability of the material. Furthermore, the microstructure of the material, through the aforementioned processes, forms a multi-scale strengthening mechanism. The synergistic effect of deformation twins, precipitates, residual compressive stress, and dislocation density significantly improves the overall performance of the material, thereby meeting the application requirements of wire thread inserts in high-strength fastening, wear-resistant service, and fatigue-resistant scenarios, providing a solid guarantee for high-reliability applications under complex working conditions.

[0028] This invention also discloses a wire thread insert, the preparation method of which is as follows:

[0029] A1. Cut the round steel wire into short segments of predetermined length according to the specifications of the steel wire thread insert, and control the tolerance range of the cutting length to be ±0.05mm.

[0030] A2. The steel wire segments obtained in step A1 are formed using a spiral forming device; the forming process adopts a cold forming process, the forming temperature is controlled within the range of room temperature to 50℃, the axial pressure during forming is controlled at 100~300MPa, and the forming speed is controlled at 20~50mm / s; the pitch tolerance of the formed steel wire thread sleeve is ±0.02mm, and the outer diameter tolerance of the thread is ±0.05mm.

[0031] A3. Surface treatment of the formed wire thread insert in step A2 includes the following steps: First, the surface of the wire thread insert is cleaned using an ultrasonic cleaning device to remove residues and oil stains; then, a rust-preventive lubricant is uniformly coated onto the cleaned wire thread insert surface, and the thickness of the lubricant coating layer is controlled between 5 and 13 μm; finally, the coated wire thread insert is placed in a hot air drying oven at 120–150°C for curing treatment, and the curing time is 30–60 min to form a uniform lubricating protective layer.

[0032] This invention employs a combination of precision cold forming and surface treatment to enhance the dimensional accuracy, mechanical properties, and corrosion resistance of wire thread inserts. By optimizing the forming and subsequent processing, the overall quality and service performance of the wire thread insert are improved. In the manufacturing process, round steel wire is first cut into precisely sized segments according to the specifications of the wire thread insert, with the cutting length tolerance controlled within ±0.05mm to ensure dimensional consistency and precision during subsequent forming. Subsequently, the wire segments are spirally formed using a cold forming process at temperatures ranging from room temperature to 50°C. Precise control of axial pressure and forming speed maintains the tolerances of the pitch and thread outer diameter within ±0.02mm and ±0.05mm, respectively, significantly improving the forming accuracy and dimensional stability of the insert. Simultaneously, the dislocation strengthening effect introduced by the cold working process enhances its strength and fatigue resistance. After forming, the wire thread insert undergoes ultrasonic cleaning to remove surface residues and oil, effectively ensuring the uniformity and adhesion of subsequent coating processes. Next, a rust-inhibiting lubricant is uniformly applied, with the coating thickness controlled between 5 and 13 μm. This not only forms an effective protective barrier on the insert surface, significantly improving its corrosion resistance, but also reduces the coefficient of friction during assembly, thus minimizing wear. Finally, curing is performed in a hot air drying oven at 120–150℃ to ensure the uniformity and stability of the lubricant coating. Each step in the entire manufacturing process complements the others. The dimensional accuracy during the cutting stage provides a reliable guarantee for the forming process, the optimized process parameters during cold forming ensure the mechanical properties and forming quality of the insert, and the meticulous surface treatment further enhances the insert's corrosion resistance and service life. Through the synergy of these processes, the wire thread insert achieves excellent performance in high-precision, high-strength, and complex service environments, significantly meeting the demands of aerospace, automotive manufacturing, and precision machinery industries for high-performance fasteners.

[0033] Beneficial effects

[0034] 1. This invention, through the synergistic optimization of a multi-step quenching process, significantly outperforms existing technologies in enhancing the strength, wear resistance, and fatigue resistance of round steel wire for wire thread inserts. By precisely controlling austenitizing treatment, initial quenching, redistribution treatment, and secondary quenching, the invention effectively refines grains, generates dispersed Ni(Ti,Al) precipitates, and stabilizes residual austenite, achieving a synergistic improvement in strength, toughness, and wear resistance. Compared to traditional processes, this invention significantly improves the uniformity of the material's microstructure and the distribution of residual stress, effectively solving the problems of insufficient strength and fatigue failure under complex service environments, meeting the requirements of high-load dynamic operating conditions, and promoting the development of the high-performance fastener industry.

[0035] 2. This invention achieves a significant improvement in the strength, wear resistance, and fatigue resistance of round steel wire for wire thread inserts through the synergistic optimization of multi-component alloy design and refined quenching process. The precise proportions of elements such as C, Cr, Ni, and Ti, combined with the dispersed distribution of short rod-shaped Ni(Ti,Al) precipitates, construct a multi-scale strengthening mechanism. The synergistic effect of deformation twins, dislocation density, and residual compressive stress effectively enhances the balance between matrix strength and plasticity. Quenching refines the grains and optimizes the grain boundary structure, improving stress distribution capabilities and solving the problem of insufficient performance balance in existing technologies. This invention provides a reliable solution in the field of high-strength fasteners, particularly suitable for complex service environments such as aerospace and automotive manufacturing, driving technological progress in the industry and significantly enhancing application reliability and service life.

[0036] 3. This invention achieves significant improvements in the dimensional accuracy, mechanical properties, and corrosion resistance of wire thread inserts through the synergistic optimization of precision cold forming and surface treatment. Compared with existing technologies, it offers higher pitch and thread outer diameter accuracy, superior strength and fatigue resistance, and effectively reduces corrosion and wear problems. The cutting, cold forming, and surface treatment steps complement each other. Precise design of dimensional control, dislocation strengthening, and protective coatings ensures the high stability and long service life of the thread insert. Its innovative process provides a reliable solution for the high-performance fastener industry, meeting the stringent requirements of complex working conditions in fields such as aerospace and automotive manufacturing. Attached Figure Description

[0037] Figure 1 The backscattering results of the round steel wire prepared for Example 1 of the present invention show a stable {111} texture feature.

[0038] Figure 2 This is a transmission electron microscope image of the twinned morphology of the round steel wire prepared in Example 1 of the present invention.

[0039] Figure 3 The images show the large-angle and small-angle grain boundaries of the round steel wire prepared in Example 1 of this invention.

[0040] Figure 4 The interface between the Ni(Ti,Al) precipitate phase and α-Fe in the round steel wire prepared in Example 1 of this invention.

[0041] Figure 5 The distribution of the short rod-shaped Ni(Ti,Al) precipitate prepared in Example 1 of this invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0043] Example 1

[0044] This embodiment provides a round steel wire for wire thread inserts. The chemical composition of the round steel wire, by weight percentage, includes: 0.10% C, 10.0% Cr, 0.50% Si, 0.30% Mn, 0.15% Ni, 0.01% Mo, 0.15% Cu, 0.005% Ti, 0.001% S, 0.025% P, 0.001% Al, 0.085% V, 0.008% Co, and 0.008% Nb, with the balance being Fe and unavoidable impurities.

[0045] The round steel wire used for wire thread inserts contains deformed twins with an average width of 30 nm and an average density of 1.1 × 10¹² cm⁻². It also contains short rod-shaped Ni(Ti,Al) precipitates with an average width of 5.0 nm and an average length of 50 nm. These short rod-shaped Ni(Ti,Al) precipitates are dispersed within the matrix grains, with a spacing of 20 nm. The interface between the Ni(Ti,Al) precipitates and the α-Fe in the matrix is ​​a semi-coherent interface with a mismatch degree of 1.5%. The dislocation density of the round steel wire used for wire thread inserts is 5.0 × 10¹⁴ m⁻². After redistribution treatment, the matrix grains of the round steel wire used for wire thread inserts are refined to an average grain size of 1.5 μm, exhibiting a {111} texture. In the round steel wire used for wire thread inserts, the residual compressive stress at the interface between the Ni(Ti,Al) precipitate phase and the α-Fe matrix ranges from 400 MPa. The ratio of large-angle grain boundaries to small-angle grain boundaries in the round steel wire used for wire thread inserts is 55:45.

[0046] A quenching process for round steel wire used in wire thread inserts includes the following steps:

[0047] S1: The hot-rolled wire rod of steel thread insert is pretreated to remove surface impurities. The pretreatment process is as follows: the hot-rolled wire rod of steel thread insert is placed in a pickling tank, 10wt.% dilute nitric acid solution is added, and stirring is maintained for 5 minutes to remove the surface oxide scale. After pickling, the hot-rolled wire rod is rinsed 3 times with deionized water, and the rinsed hot-rolled wire rod is placed in a hot air drying oven at 70℃ and dried for 30 minutes.

[0048] S2: The round steel wire obtained in step S1 is subjected to austenitizing treatment to obtain austenitic wire rod; the austenitizing treatment process is as follows: the hot-rolled wire rod in step S1 is heated to 1100℃ in a heating furnace at a heating rate of 5℃ / min, and held for 3.0min to complete the austenitizing treatment and obtain austenitic wire rod.

[0049] S3: The austenitic wire rod obtained in step S2 is subjected to initial quenching to obtain martensitic wire rod; the initial quenching process is as follows: the austenitic wire rod obtained in step S2 is quenched in an oil bath at 180°C and held in the oil bath for 60 seconds to obtain martensitic wire rod.

[0050] S4: The martensitic wire rod obtained in step S3 is subjected to redistribution treatment and secondary quenching to obtain the finished round steel wire for wire thread inserts. The secondary quenching process is as follows: the martensitic wire rod obtained in step S3 is placed in a molten salt bath at 420℃ and kept at that temperature for 30 minutes to complete the redistribution treatment. After the redistribution treatment is completed, it is then subjected to room temperature water quenching to obtain the finished round steel wire for wire thread inserts.

[0051] S5: The round steel wire used for wire thread inserts from S4 is drawn to obtain the round steel wire for wire thread inserts. The drawing process is as follows: the surface of the round steel wire used for wire thread inserts is coated with lubricant, and then it is drawn in 5 passes, with a deformation of 5% in each pass, to finally obtain the round steel wire for wire thread inserts.

[0052] pass Figures 1 to 5 The results demonstrate that the round steel wire prepared in Example 1 of this invention has significant advantages in terms of microstructure and texture characteristics. Figure 1 The backscattering results show a stable {111} texture, indicating that the material achieved an ideal crystal orientation through process optimization during preparation, which helps to improve the material's mechanical and fatigue properties. Figure 2 The transmission electron microscopy (TEM) images of the twins further demonstrate that a large number of twin structures exist in the round steel wire. This structure can effectively improve the strength and plasticity of the material, while also helping to hinder crack propagation and enhance the overall mechanical properties of the material. Figure 3 The distribution of large-angle and small-angle grain boundaries shown indicates that the grain boundary structure in the material is significantly optimized. The presence of large-angle grain boundaries helps to improve the strength and toughness of the material, while small-angle grain boundaries can provide better dislocation strengthening effect. Figure 4 The interfacial structure between the Ni(Ti,Al) precipitate phase and the α-Fe matrix phase was revealed. The stability of this interfacial bonding plays an important role in the precipitation strengthening effect of the material, thereby significantly improving the fatigue resistance of the material. Figure 5 The distribution of short, rod-shaped Ni(Ti,Al) precipitates is shown, and their uniform and fine distribution further demonstrates the effectiveness of precipitate control during the process. This distribution can significantly improve the hardness and wear resistance of the material. In summary, the results shown above fully demonstrate that Example 1 of the present invention, through optimized process conditions, significantly improves the microstructure and performance of round steel wire, providing strong support for engineering applications requiring high strength, high fatigue life, and high wear resistance.

[0053] Example 2

[0054] This embodiment discloses a round steel wire for wire thread inserts. The chemical composition of the round steel wire, by weight percentage, includes: 0.13% C, 10.9% Cr, 0.53% Si, 0.32% Mn, 0.18% Ni, 0.01% Mo, 0.16% Cu, 0.006% Ti, 0.001% S, 0.028% P, 0.001% Al, 0.087% V, 0.009% Co, 0.009% Nb, with the balance being Fe and unavoidable impurities.

[0055] The round steel wire used for wire thread inserts contains deformed twins with an average width of 40 nm and an average density of 1.7 × 10¹² cm⁻². It also contains short rod-shaped Ni(Ti,Al) precipitates with an average width of 8.0 nm and an average length of 80 nm. These short rod-shaped Ni(Ti,Al) precipitates are dispersed within the matrix grains, with a spacing of 26 nm. The interface between the Ni(Ti,Al) precipitates and the α-Fe in the matrix is ​​a semi-coherent interface with a mismatch degree of 1.8%. The dislocation density of the round steel wire used for wire thread inserts is 6.5 × 10¹⁴ m⁻². After redistribution treatment, the matrix grains of the round steel wire used for wire thread inserts are refined to an average grain size of 1.8 μm, exhibiting a {111} texture. In the round steel wire used for wire thread inserts, the residual compressive stress distribution at the interface between the Ni(Ti,Al) precipitate phase and the α-Fe matrix ranges from 360 MPa. The ratio of large-angle grain boundaries to small-angle grain boundaries in the round steel wire used for wire thread inserts is 58:42.

[0056] A quenching process for round steel wire used in wire thread inserts includes the following steps:

[0057] S1: The hot-rolled wire rod of steel thread insert is pretreated to remove surface impurities. The pretreatment process is as follows: the hot-rolled wire rod of steel thread insert is placed in a pickling tank, 10wt.% dilute nitric acid solution is added, and stirring is maintained for 6 minutes to remove the surface oxide scale. After pickling, the hot-rolled wire rod is rinsed 3 times with deionized water, and the rinsed hot-rolled wire rod is placed in a hot air drying oven at 73℃ and dried for 39 minutes.

[0058] S2: The round steel wire obtained in step S1 is subjected to austenitizing treatment to obtain austenitic wire rod; the austenitizing treatment process is as follows: the hot-rolled wire rod in step S1 is heated to 1115℃ in a heating furnace at a heating rate of 6℃ / min, and held for 4.0min to complete the austenitizing treatment and obtain austenitic wire rod.

[0059] S3: The austenitic wire rod obtained in step S2 is subjected to initial quenching to obtain martensitic wire rod; the initial quenching process is as follows: the austenitic wire rod obtained in step S2 is quenched in an oil bath at 186°C and held in the oil bath for 62s to obtain martensitic wire rod.

[0060] S4: The martensitic wire rod obtained in step S3 is subjected to redistribution treatment and secondary quenching to obtain the finished round steel wire for wire thread inserts. The secondary quenching process is as follows: the martensitic wire rod obtained in step S3 is placed in a molten salt bath at 426℃ and kept at that temperature for 39 minutes to complete the redistribution treatment. After the redistribution treatment is completed, it is then subjected to room temperature water quenching to obtain the finished round steel wire for wire thread inserts.

[0061] S5: The round steel wire used for wire thread inserts from S4 is drawn to obtain the round steel wire for wire thread inserts. The drawing process is as follows: the surface of the round steel wire used for wire thread inserts is coated with lubricant, and then it is drawn in 4 passes, with a deformation of 8% in each pass, to finally obtain the round steel wire for wire thread inserts.

[0062] Example 3

[0063] This embodiment provides a round steel wire for wire thread inserts. The chemical composition of the round steel wire, by weight percentage, includes: 0.16% C, 11.1% Cr, 0.56% Si, 0.33% Mn, 0.21% Ni, 0.02% Mo, 0.18% Cu, 0.006% Ti, 0.001% S, 0.031% P, 0.001% Al, 0.088% V, 0.010% Co, and 0.010% Nb, with the balance being Fe and unavoidable impurities.

[0064] The round steel wire used for wire thread inserts contains deformed twins with an average width of 51 nm and an average density of 2.6 × 10¹² cm⁻². It also contains short rod-shaped Ni(Ti,Al) precipitates with an average width of 11 nm and an average length of 113 nm. These short rod-shaped Ni(Ti,Al) precipitates are dispersed within the matrix grains, with a spacing of 38 nm. The interface between the Ni(Ti,Al) precipitates and the α-Fe in the matrix is ​​a semi-coherent interface with a mismatch degree of 2.4%. The dislocation density of the round steel wire used for wire thread inserts is 8.0 × 10¹⁴ m⁻². After redistribution treatment, the matrix grains of the round steel wire used for wire thread inserts are refined to an average grain size of 2.4 μm, exhibiting a {111} texture. In the round steel wire used for wire thread inserts, the residual compressive stress distribution at the interface between the Ni(Ti,Al) precipitate phase and the α-Fe matrix ranges from 280 MPa. The ratio of large-angle grain boundaries to small-angle grain boundaries in the round steel wire used for wire thread inserts is 64:36.

[0065] A quenching process for round steel wire used in wire thread inserts includes the following steps:

[0066] S1: The hot-rolled wire rod of steel thread insert is pretreated to remove surface impurities. The pretreatment process is as follows: the hot-rolled wire rod of steel thread insert is placed in a pickling tank, 10wt.% dilute nitric acid solution is added, and stirring is maintained for 8 minutes to remove the surface oxide scale. After pickling, the hot-rolled wire rod is rinsed 3 times with deionized water, and the rinsed hot-rolled wire rod is placed in a hot air drying oven at 76℃ and dried for 45 minutes.

[0067] S2: The round steel wire obtained in step S1 is subjected to austenitizing treatment to obtain austenitic wire rod; the austenitizing treatment process is as follows: the hot-rolled wire rod in step S1 is heated to 1130℃ in a heating furnace at a heating rate of 8℃ / min, and held for 4.2min to complete the austenitizing treatment and obtain austenitic wire rod.

[0068] S3: The austenitic wire rod obtained in step S2 is subjected to initial quenching to obtain martensitic wire rod; the initial quenching process is as follows: the austenitic wire rod obtained in step S2 is quenched in an oil bath at 192°C and held in the oil bath for 66s to obtain martensitic wire rod.

[0069] S4: The martensitic wire rod obtained in step S3 is subjected to redistribution treatment and secondary quenching to obtain the finished round steel wire for wire thread inserts. The secondary quenching process is as follows: the martensitic wire rod obtained in step S3 is placed in a molten salt bath at 438℃ and kept at that temperature for 48 minutes to complete the redistribution treatment. After the redistribution treatment is completed, it is then subjected to room temperature water quenching to obtain the finished round steel wire for wire thread inserts.

[0070] S5: The round steel wire used for wire thread inserts from S4 is drawn to obtain the round steel wire for wire thread inserts. The drawing process is as follows: the surface of the round steel wire used for wire thread inserts is coated with lubricant, and then it is drawn in 4 passes, with a deformation of 8% in each pass, to finally obtain the round steel wire for wire thread inserts.

[0071] Example 4

[0072] This embodiment provides a round steel wire for wire thread inserts. The chemical composition of the round steel wire, by weight percentage, includes: 0.22% C, 13.5% Cr, 0.60% Si, 0.35% Mn, 0.25% Ni, 0.03% Mo, 0.20% Cu, 0.007% Ti, 0.002% S, 0.035% P, 0.002% Al, 0.090% V, 0.012% Co, and 0.012% Nb, with the balance being Fe and unavoidable impurities.

[0073] The round steel wire used for wire thread inserts contains deformed twins with an average width of 65 nm and an average density of 3.5 × 10¹² cm⁻². It also contains short rod-shaped Ni(Ti,Al) precipitates with an average width of 15 nm and an average length of 145 nm. These short rod-shaped Ni(Ti,Al) precipitates are dispersed within the matrix grains, with a spacing of 50 nm. The interface between the Ni(Ti,Al) precipitates and the α-Fe in the matrix is ​​a semi-coherent interface with a mismatch degree of 3.0%. The dislocation density of the round steel wire used for wire thread inserts is 1.0 × 10¹⁵ m⁻². After redistribution treatment, the matrix grains of the round steel wire used for wire thread inserts are refined to an average grain size of 3.0 μm, exhibiting a {111} texture. In the round steel wire for wire thread inserts, the residual compressive stress at the interface between the Ni(Ti,Al) precipitate phase and the α-Fe matrix ranges from 200 MPa. The ratio of large-angle grain boundaries to small-angle grain boundaries in the round steel wire for wire thread inserts is 70:30.

[0074] A quenching process for round steel wire used in wire thread inserts includes the following steps:

[0075] S1: The hot-rolled wire rod of steel thread insert is pretreated to remove surface impurities. The pretreatment process is as follows: the hot-rolled wire rod of steel thread insert is placed in a pickling tank, 10wt.% dilute nitric acid solution is added, and stirring is maintained for 10 minutes to remove the surface oxide scale. After pickling, the hot-rolled wire rod is rinsed 3 times with deionized water, and the rinsed hot-rolled wire rod is placed in an 80℃ hot air drying oven for 60 minutes to dry.

[0076] S2: The round steel wire obtained in step S1 is subjected to austenitizing treatment to obtain austenitic wire rod; the austenitizing treatment process is as follows: the hot-rolled wire rod in step S1 is heated to 1150℃ in a heating furnace at a heating rate of 10℃ / min and held for 5.0min to complete the austenitizing treatment and obtain austenitic wire rod.

[0077] S3: The austenitic wire rod obtained in step S2 is subjected to initial quenching to obtain martensitic wire rod; the initial quenching process is as follows: the austenitic wire rod obtained in step S2 is quenched in an oil bath at 200°C and kept in the oil bath for 70 seconds to obtain martensitic wire rod.

[0078] S4: The martensitic wire rod obtained in step S3 is subjected to redistribution treatment and secondary quenching to obtain the finished round steel wire for wire thread inserts. The secondary quenching process is as follows: the martensitic wire rod obtained in step S3 is placed in a molten salt bath at 450℃ and kept at that temperature for 60 minutes to complete the redistribution treatment. After the redistribution treatment is completed, it is then subjected to room temperature water quenching to obtain the finished round steel wire for wire thread inserts.

[0079] S5: The round steel wire used for wire thread inserts from S4 is drawn to obtain the round steel wire for wire thread inserts. The drawing process is as follows: the surface of the round steel wire used for wire thread inserts is coated with lubricant, and then it is drawn in 3 passes, with a deformation of 10% in each pass, to finally obtain the round steel wire for wire thread inserts.

[0080] Comparative Example 1

[0081] The process is basically the same as in Example 1, except that in the S2 austenitizing treatment, the austenitizing temperature is reduced to 1050°C, which is lower than the minimum range (1100°C).

[0082] Comparative Example 2

[0083] The process is basically the same as in Example 1, except that in the initial quenching process of S3, the oil bath temperature is increased to 220°C, which is higher than the maximum range (200°C).

[0084] Comparative Example 3

[0085] The process is basically the same as in Example 1, except that in the S4 secondary quenching process, the molten salt temperature of the salt bath is set to 400°C, which is lower than the minimum range (420°C).

[0086] Comparative Example 4

[0087] The process is basically the same as in Example 1, except that in the S5 drawing process, the amount of deformation per drawing pass is increased to 15%, which is higher than the maximum range (10%).

[0088] Comparative Example 5

[0089] It is basically the same as Example 1, except that in the initial quenching process of S3, the holding time is increased to 100 seconds, which is higher than the maximum range (70 seconds).

[0090] Comparative Example 6

[0091] The process is basically the same as in Example 1, except that in the S5 drawing process, the number of drawing passes is reduced to 2, which is lower than the minimum range (3 times).

[0092] Comparative Example 7

[0093] The process is basically the same as in Example 1, except that in the S4 redistribution process, the heat preservation time is shortened to 20 minutes, which is lower than the minimum range (30 minutes).

[0094] Comparative Example 8

[0095] The process is basically the same as in Example 1, except that in the S2 austenitizing treatment, the heating rate is increased to 15°C / min, which is higher than the maximum range (10°C / min).

[0096] Performance testing:

[0097] The test method for the tensile strength of round steel wire is as follows: First, select a round steel wire specimen that meets the standard requirements and ensure that its surface is free of obvious defects. The diameter and length of the specimen must meet the requirements of the testing equipment. Then, fix the specimen in the clamp of the tensile testing machine, ensuring that the clamp is tight and the specimen remains vertical to prevent slippage or uneven force during the test. Start the tensile testing machine and apply axial tensile loading to the specimen at a specified loading speed (usually 1-5 mm / min). During the tensile process, the testing machine will record the load and the elongation of the specimen in real time. When the specimen breaks, record the maximum load value. The ratio of this load value to the initial cross-sectional area of ​​the specimen is the tensile strength of the specimen. Finally, calculate the tensile strength according to the formula σ = Fmax / A, where σ is the tensile strength, Fmax is the maximum load before the specimen breaks, and A is the initial cross-sectional area of ​​the specimen. At the same time, perform multiple repeatable tests on the test results to verify the reliability of the data. Organize and analyze the data according to relevant standards to obtain the final tensile strength value.

[0098] Fatigue Strength: The test method for fatigue strength of round steel wire is as follows: First, select a round steel wire specimen that meets the test standard requirements. The length is typically 200mm. Ensure the specimen surface is smooth and free of obvious defects, and that its size and shape meet the requirements of the fatigue testing equipment. Then, install the specimen on the fatigue testing machine, fixing both ends of the specimen in the fixtures. The fixtures must ensure a coaxiality deviation of less than 1% to avoid eccentricity or uneven stress during the test. Start the fatigue testing machine, select tension-tension loading according to the test requirements, set the loading frequency (typically 50Hz), and set the initial load range (maximum stress is 50%–70% of the material's yield strength). During the test, the specimen is subjected to alternating... The test specimen is repeatedly cyclically loaded under load, and the stress level and number of cycles are recorded in real time by the testing machine until the specimen breaks or reaches the set upper limit of the number of cycles (usually 10 times). If the specimen does not break, the stress amplitude is gradually increased (usually in increments of 5 MPa), and the test is repeated until the maximum bearing stress amplitude of the specimen is determined. The SN curve (stress-life curve) is plotted based on the test results, and the fatigue strength is the maximum stress at the corresponding set cycle life (10 times). Finally, the test results are repeated at least 3 times to ensure the accuracy and reliability of the data, and the results are analyzed and reported in accordance with relevant standards, while the influence of environmental parameters on the test results is recorded.

[0099] Abrasion Resistance Test: The test method for the abrasion resistance of round steel wire is as follows: First, select a round steel wire sample that meets the test standard requirements. The length is usually 100mm to 200mm. Ensure that the sample surface is smooth and free of obvious defects, and remove surface oil and impurities. Then, install the sample on the abrasion testing machine. The clamps of the testing machine must ensure that the sample is firmly fixed and kept straight to avoid slippage or bending deformation during the test. Select the friction condition according to the test requirements, linear friction, and set the loading pressure of the testing machine to 5N, the sliding speed to 100mm / s, and the wear stroke to 50mm. At the same time, select a suitable friction mating material (such as hard steel plate or ceramic material), whose hardness is usually 60HRC, and ensure that the surface of the mating material is rough. The roughness is Ra 0.2 μm. During the test, parameters such as loading force, friction force, and sliding distance are recorded. The sample slides back and forth on the friction mating material for 30 minutes or a sliding distance of 100 m. After the test, the sample is removed, and the mass of the sample before and after the test is measured using a precision balance with an accuracy of 0.1 mg. The wear amount is calculated by mass loss. At the same time, the surface wear morphology of the sample and mating material is observed using a three-dimensional optical profilometer or scanning electron microscope (SEM), and the depth and width of the wear marks are measured. Finally, the test results are repeated at least three times to ensure the accuracy and reliability of the data. The wear resistance is analyzed according to relevant standards, and the influence of the test environment parameters is recorded.

[0100] The properties of the round steel wires from Examples 1-4 and Comparative Examples 1-8 are summarized in Table 2.

[0101] Table 1 Summary of the performance of round steel wires in Examples 1-4 and Comparative Examples 1-8

[0102]

[0103]

[0104] The main difference between Comparative Example 1 and Example 1 lies in the lower austenitizing temperature (1050°C), which leads to grain coarsening. As shown in Table 1, the tensile strength and fatigue strength of Comparative Example 1 are significantly lower than those of Example 1, while the wear resistance is slightly improved. The lower austenitizing temperature is insufficient to form uniform and fine austenite grains, resulting in a less refined martensite structure after quenching, which weakens the material's strength and toughness. However, the larger grains and softer structure can slow down the wear process, thus slightly improving the wear resistance of Comparative Example 1.

[0105] The main difference between Comparative Example 2 and Example 1 lies in the excessively high initial quenching temperature (220°C), resulting in insufficient martensite structure. As shown in Table 2, the tensile strength and fatigue strength of Comparative Example 2 are lower than those of Example 1, while the wear resistance is slightly improved. An excessively high initial quenching temperature prevents some austenite from fully transforming into high-hardness martensite, leading to a decrease in material strength. However, this incomplete quenching may result in a softer structure, reducing surface damage from wear and thus slightly improving wear resistance.

[0106] The main difference between Comparative Example 3 and Example 1 is the lower secondary quenching temperature (400°C), which resulted in insufficient formation of precipitated phases. As shown in Table 2, the tensile strength and fatigue strength of Comparative Example 3 are lower than those of Example 1, while its wear resistance is improved. The lower secondary quenching temperature leads to insufficient precipitation of strengthening phases, thereby weakening the material's strength and fatigue performance. However, the softer microstructure exhibits better friction adaptability, which slightly improves the wear resistance of Comparative Example 3.

[0107] The main difference between Comparative Example 4 and Example 1 is the excessively large drawing deformation (15%), resulting in an excessively high dislocation density. As shown in Table 2, the tensile strength and fatigue strength of Comparative Example 4 are lower than those of Example 1, while its wear resistance is improved. Excessive drawing deformation leads to dislocation accumulation and stress concentration within the crystal lattice, making the material more brittle and reducing its strength and fatigue performance. However, due to the enhanced surface hardening effect, the wear resistance of the material is improved to some extent.

[0108] The main difference between Comparative Example 5 and Example 1 is the excessively long initial quenching time (100 seconds), which leads to excessive transformation of the martensitic structure. As shown in Table 2, the tensile strength and fatigue strength of Comparative Example 5 are lower than those of Example 1, while the wear resistance is slightly reduced. Excessive quenching time causes coarsening of the internal structure, reducing the strength and toughness of the material, while also weakening the surface hardness, thus resulting in decreased wear resistance.

[0109] The main difference between Comparative Example 6 and Example 1 lies in the insufficient number of drawing passes (2 passes), resulting in insufficient work hardening. As shown in Table 2, the tensile strength and fatigue strength of Comparative Example 6 are significantly lower than those of Example 1, while the wear resistance is slightly improved. Insufficient drawing passes reduce the dislocation density of the material, leading to a significant decrease in strength and fatigue performance. However, due to insufficient work hardening, the material surface is softer, which helps with friction adaptability and improves wear resistance to some extent.

[0110] The main difference between Comparative Example 7 and Example 1 lies in the insufficient redistribution holding time (20 minutes), resulting in inadequate formation of the precipitated phase. As shown in Table 2, the tensile strength and fatigue strength of Comparative Example 7 are lower than those of Example 1, while the wear resistance is slightly improved. The shorter holding time leads to insufficient precipitation of the reinforcing phase, thus weakening the material's strength and fatigue properties. However, the softer microstructure provides better adaptability during friction, thereby slightly improving the wear resistance.

[0111] The main difference between Comparative Example 8 and Example 1 lies in the excessively high heating rate (15°C / min), which leads to grain coarsening and poor microstructure uniformity. As shown in Table 2, the tensile strength and fatigue strength of Comparative Example 8 are lower than those of Example 1, while the wear resistance is slightly improved. A higher heating rate causes rapid grain growth, thereby weakening the material's strength and toughness. However, the coarsened microstructure can mitigate wear to some extent, thus slightly improving wear resistance.

[0112] In summary, the performance comparison analysis of Examples 1-4 and Comparative Examples 1-8 shows that the Examples exhibit superior comprehensive performance in terms of tensile strength, fatigue strength, and wear resistance, while the Comparative Examples show varying degrees of performance degradation due to deviations in process parameters. Specifically, the Examples, by optimizing process parameters such as austenitizing temperature, quenching temperature and time, and drawing deformation, achieve significant grain refinement, sufficient formation of precipitated strengthening phases, and full utilization of the material's strength and toughness, demonstrating a high level within the industry. The Comparative Examples, due to grain coarsening, insufficient precipitates, excessive retained austenite, or stress concentration, generally experience a decline in strength and fatigue performance, making them unsuitable for high-end engineering applications. Regarding wear resistance, the Examples exhibit stable and excellent performance, with wear rates lower than the industry average, making them suitable for high-wear conditions. Some Comparative Examples (such as Comparative Examples 3 and 6), due to softer microstructures or surface hardening effects, show slightly improved wear resistance, but overall, the performance fluctuates significantly and is less stable, failing to reach the performance level of the Examples. The performance degradation of the Comparative Examples is mainly due to deviations from the optimal range of key process parameters. For example, an excessively low austenitizing temperature (Comparative Example 1) leads to grain coarsening; abnormal quenching temperature or time (Comparative Examples 2 and 5) affects martensitic transformation and microstructure uniformity; insufficient or excessive drawing process (Comparative Examples 4 and 6) results in abnormal dislocation density or insufficient hardening effect; and unreasonable heating rate and holding time (Comparative Examples 7 and 8) affect precipitate formation and microstructure uniformity. Overall, the optimized process parameters of the embodiments significantly improve material properties, achieving a balance in tensile strength, fatigue strength, and wear resistance, demonstrating comprehensive advantages. In contrast, the comparative examples show a declining trend in performance, especially in strength and fatigue performance, which are significantly lower than the embodiments. This is mainly due to deviations in process parameters leading to grain coarsening or microstructure inhomogeneity. In summary, the optimized process of the embodiments significantly improves the comprehensive performance of round steel wire, meeting the stringent requirements of high-end applications for strength, fatigue life, and wear resistance. The performance fluctuations of the comparative examples further verify the significant impact of process parameters on material properties.

[0113] Example 5

[0114] The method for preparing a wire thread insert in this embodiment is as follows:

[0115] A1. Cut the round steel wire into short segments of predetermined length according to the specifications of the steel wire thread insert, and control the tolerance range of the cutting length to be ±0.05mm.

[0116] A2. The steel wire segments obtained in step A1 are formed using a spiral forming device; the forming process adopts a cold forming process, the forming temperature is controlled within the room temperature range, the axial pressure during forming is controlled at 100MPa, and the forming speed is controlled at 20mm / s; the pitch tolerance of the formed steel wire thread sleeve is ±0.02mm, and the outer diameter tolerance of the thread is ±0.05mm.

[0117] A3. Perform surface treatment on the wire thread insert formed in step A2. The surface treatment includes the following steps: First, use an ultrasonic cleaning device to clean the surface of the wire thread insert to remove residues and oil stains; then, uniformly coat the cleaned wire thread insert surface with an anti-rust lubricant, and control the thickness of the lubricant coating layer to 5μm; finally, place the coated wire thread insert in a hot air drying oven at 120℃ for curing treatment, and the curing time is 30min to form a uniform lubricating protective layer.

[0118] Example 6

[0119] The method for preparing a wire thread insert in this embodiment is as follows:

[0120] A1. Cut the round steel wire into short segments of predetermined length according to the specifications of the steel wire thread insert, and control the tolerance range of the cutting length to be ±0.05mm.

[0121] A2. The steel wire segments obtained in step A1 are formed using a spiral forming device; the forming process adopts a cold forming process, the forming temperature is controlled within the range of room temperature to 15℃, the axial pressure during forming is controlled at 130MPa, and the forming speed is controlled at 26mm / s; the pitch tolerance of the formed steel wire thread sleeve is ±0.02mm, and the outer diameter tolerance of the thread is ±0.05mm.

[0122] A3. Surface treatment of the formed wire thread insert in step A2 includes the following steps: First, the surface of the wire thread insert is cleaned using an ultrasonic cleaning device to remove residues and oil stains; then, a rust-preventive lubricant is uniformly coated onto the cleaned wire thread insert surface, and the thickness of the lubricant coating layer is controlled at 7μm; finally, the coated wire thread insert is placed in a hot air drying oven at 135℃ for curing treatment, and the curing time is 39min to form a uniform lubricating protective layer.

[0123] Example 7

[0124] The method for preparing a wire thread insert in this embodiment is as follows:

[0125] A1. Cut the round steel wire into short segments of predetermined length according to the specifications of the steel wire thread insert, and control the tolerance range of the cutting length to be ±0.05mm.

[0126] A2. The steel wire segments obtained in step A1 are formed using a spiral forming device; the forming process adopts a cold forming process, the forming temperature is controlled within the range of room temperature to 40℃, the axial pressure during forming is controlled at 220MPa, and the forming speed is controlled at 38mm / s; the pitch tolerance of the formed steel wire thread sleeve is ±0.02mm, and the outer diameter tolerance of the thread is ±0.05mm.

[0127] A3. Perform surface treatment on the wire thread insert formed in step A2. The surface treatment includes the following steps: First, use an ultrasonic cleaning device to clean the surface of the wire thread insert to remove residues and oil stains; then, uniformly coat the cleaned wire thread insert surface with an anti-rust lubricant, and control the thickness of the lubricant coating layer to 11 μm; finally, place the coated wire thread insert in a hot air drying oven at 140℃ for curing treatment, and the curing time is 54 min to form a uniform lubricating protective layer.

[0128] Example 8

[0129] The method for preparing a wire thread insert in this embodiment is as follows:

[0130] A1. Cut the round steel wire into short segments of predetermined length according to the specifications of the steel wire thread insert, and control the tolerance range of the cutting length to be ±0.05mm.

[0131] A2. The steel wire segments obtained in step A1 are formed using a spiral forming device; the forming process adopts a cold forming process, the forming temperature is controlled within 50℃, the axial pressure during forming is controlled at 300MPa, and the forming speed is controlled at 50mm / s; the pitch tolerance of the formed steel wire thread sleeve is ±0.02mm, and the outer diameter tolerance of the thread is ±0.05mm.

[0132] A3. Surface treatment of the formed wire thread insert in step A2 includes the following steps: First, the surface of the wire thread insert is cleaned using an ultrasonic cleaning device to remove residues and oil stains; then, a rust-preventive lubricant is uniformly coated onto the cleaned wire thread insert surface, and the thickness of the lubricant coating layer is controlled at 13μm; finally, the coated wire thread insert is placed in a hot air drying oven at 150℃ for curing treatment, and the curing time is 60min to form a uniform lubricating protective layer.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A round steel wire for wire threaded inserts, characterized in that, The chemical composition of the round steel wire, by weight percentage, includes: 0.10–0.22% C, 10.0–13.5% Cr, 0.50–0.60% Si, 0.30–0.35% Mn, 0.15–0.25% Ni, 0.01–0.03% Mo, 0.15–0.20% Cu, 0.005–0.007% Ti, 0.001–0.002% S, 0.025–0.035% P, 0.001–0.002% Al, 0.085–0.090% V, 0.008–0.012% Co, 0.008–0.012% Nb, with the balance being Fe and unavoidable impurities; The round steel wire contains deformed twins with an average width of 30–65 nm and an average density of 1.1 × 10⁻⁶. 12 ~3.5×10 12 cm -2 ; The round steel wire contains a short rod-shaped Ni3(Ti,Al) precipitate phase, the average width of which is 5.0–15 nm and the average length is 50–145 nm. The short rod-shaped Ni3(Ti,Al) precipitate phase is dispersed within the matrix grains with a spacing of 20–50 nm. The dislocation density of the round steel wire is 5.0 × 10⁻⁶. 14 ~1.0×10 15 m -2 ; The matrix grains of the round steel wire are refined to an average grain size of 1.5 to 3.0 μm after redistribution treatment, and the grains exhibit {111} texture characteristics. In the round steel wire, the residual compressive stress at the interface between the Ni3(Ti,Al) precipitate phase and the α-Fe matrix ranges from 200 to 400 MPa. The ratio of large-angle grain boundaries to small-angle grain boundaries in the round steel wire is (55-70):(30-45); the interface between the Ni3(Ti,Al) precipitate phase and α-Fe in the matrix is ​​a semi-coherent interface; the interface mismatch is 1.5%-3.0%.

2. A quenching process for round steel wire used in wire thread inserts as described in claim 1, characterized in that, Includes the following steps: S1: Pre-treat the hot-rolled wire rod of round steel to remove surface impurities; S2: The round steel wire obtained after step S1 is subjected to austenitizing treatment to obtain austenitic wire rod. S3: The austenitic wire rod is subjected to initial quenching treatment to obtain a martensitic wire rod. S4: The martensitic wire rod is sequentially redistributed and quenched to obtain the finished round steel wire for wire thread sleeves. S5: The finished round steel wire for the wire thread insert is drawn to obtain the round steel wire for the wire thread insert; The pretreatment process in step S1 is as follows: the hot-rolled wire rod of round steel wire is placed in a pickling tank, 10wt.% dilute nitric acid solution is added, and stirring is maintained for 5 to 10 minutes to remove the surface oxide scale by pickling. After pickling, the hot-rolled wire rod is rinsed with deionized water 3 times, and the rinsed hot-rolled wire rod is placed in a hot air drying oven at 70 to 80°C and dried for 30 to 60 minutes. The austenitizing process in step S2 is as follows: the pretreated hot-rolled wire rod is placed in a heating furnace and heated to 1100-1150°C at a heating rate of 5-10°C / min, and held for 3.0-5.0 min to complete the austenitizing process and obtain austenitic wire rod. The initial quenching process in step S3 is as follows: the austenitic wire rod obtained in step S2 is placed in an oil bath at 180-200°C for quenching, and kept in the oil bath for 60-70 seconds to obtain a martensitic wire rod. The secondary quenching process of S4 is as follows: the martensitic wire rod is placed in a salt bath at 420-450°C and kept at that temperature for 30-60 minutes to complete the redistribution process. Then, it is quenched in water at room temperature to obtain the finished round steel wire for wire thread sleeve. The drawing process in step S5 is as follows: the surface of the finished round steel wire for wire thread insert is coated with lubricant, and then drawn through 3 to 5 passes, with a deformation of 5 to 10% in each pass, to finally obtain the round steel wire for wire thread insert.

3. A wire thread insert prepared using the round steel wire as described in claim 1, characterized in that, The method for preparing the wire thread insert is as follows: A1. Cut the round steel wire into short segments of predetermined length according to the specifications of the steel wire thread sleeve, and control the tolerance range of the cutting length to be ±0.05mm; A2. The steel wire segments obtained in step S1 are formed using a spiral forming device; the forming process adopts a cold forming process, the forming temperature is controlled within the range of room temperature to 50°C, the axial pressure during forming is controlled at 100 to 300 MPa, and the forming speed is controlled at 20 to 50 mm / s; the pitch tolerance of the formed steel wire thread sleeve is ±0.02 mm, and the outer diameter tolerance of the thread is ±0.05 mm; A3. Perform surface treatment on the formed wire thread insert from step S2, the surface treatment including the following steps: First, use ultrasonic cleaning equipment to clean the surface of the wire thread insert to remove residues and oil. Subsequently, a rust-preventive lubricant is uniformly coated onto the cleaned wire thread insert, with the thickness of the lubricant coating layer controlled between 5 and 13 μm. Finally, the coated wire thread insert is placed in a hot air drying oven at 120–150°C for curing treatment, with a curing time of 30–60 minutes, to form a uniform lubricating protective layer.

Images