High-strength low-residual-stress wire rod and preparation method thereof

Abstract

The invention discloses a high-strength low-residual-stress wire rod and a preparation method thereof, and belongs to the technical field of wire rod preparation, and the high-strength low-residual-stress wire rod is prepared by optimizing the following steel billet components: 0.01 to 0.022 percent of C, 0.235 to 0.528 percent of Mn, 0.035 to 0.064 percent of Si, 0.001 to 0.002 percent of Li, 0.005 to 0.011 percent of Zr, 0.001 to 0.006 percent of Sr, 0.008 to 0.021 percent of V, 0.006 to 0.013 percent of Nb, 0.01 to 0.025 percent of Ti, 0.02 to 0.1 percent of two or three of Re, Cr and Cu, less than or equal to 0.020 percent of S, less than or equal to 0.020 percent of P and the balance of Fe and inevitable impurities. The prepared wire rod has the characteristics of high strength and low residual stress.

Description

Technical Field

[0001] This invention relates to the field of wire rod manufacturing technology, specifically to a high-strength, low-residual-stress wire rod and its manufacturing method. Background Technology

[0002] As a basic raw material for deep processing of steel, wire rod is widely used in aerospace, high-end equipment manufacturing, automotive industry and other fields. Its strength, plasticity and residual stress level directly determine the service performance and service life of the end products. With the development of industry, the performance requirements of wire rod are getting higher and higher. It not only needs to have high strength and high plasticity, but also low residual stress, so as to avoid defects such as deformation and cracking during subsequent cold working and heat treatment.

[0003] Traditional solutions either achieve high strength by increasing carbon content or adding large amounts of expensive alloying elements such as Ni and Mo. For example, a steel wire rod for welding wire with a yield strength of 600MPa (CN111172460B) requires the addition of 1.70~1.95% Ni and 0.42~0.52% Mo, which significantly increases the cost of raw materials. Alternatively, they can only use a single microalloying element for strengthening, which makes it difficult to meet the requirements of high strength and low residual stress. The residual stress is usually higher than 150MPa, and subsequent processing is prone to deformation and cracking defects.

[0004] Based on this, the present invention designs a high-strength, low-residual-stress wire rod and its preparation method to solve the above problems. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the present invention provides a high-strength, low-residual-stress wire rod and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A high-strength, low-residual-stress wire rod comprises the following raw materials in weight percentages: C: 0.01~0.022%, Mn: 0.235~0.528%, Si: 0.035~0.064%, Li: 0.001~0.002%, Zr: 0.005~0.011%, Sr: 0.001~0.006%, V: 0.008~0.021%, Nb: 0.006~0.013%, Ti: 0.01~0.025%, two or three of Re, Cr, and Cu in 0.02~0.1wt%, S≤0.020%, P≤0.020%, and the balance being Fe and unavoidable impurities; And it satisfies the following relationship: 2.19≤ ≤4.62 The high-strength, low-residual-stress wire rod has a tensile strength ≥1235MPa, a yield strength ≥803MPa, a reduction of area ≥45%, and a residual stress ≤68MPa.

[0007] To better achieve the objectives of this invention, this invention also provides a method for preparing high-strength, low-residual-stress wire rod, comprising the following steps: S1. The raw materials are smelted and refined, and then continuously cast to obtain steel billets; S2. The steel billet is fed into a heating furnace for heating; S3. The steel billet is rolled at a rolling temperature of 840~860℃, a friction coefficient of 0.3~0.4, and a rolling speed of 16~18 m / s. S4. Use a wire spinneret to spin wire into wire rod; S5. The wire rod is subjected to cold drawing process. The cold drawing adopts multi-pass continuous drawing, with a deformation of 8~12% per pass and a cumulative deformation of 40~50%. During the drawing process, the drawing speed is controlled at 3~5 m / s and the drawing tension is 80~120N. Stress relief annealing is performed after every 3~4 passes of drawing. S6. Perform three-stage heat treatment on the wire rod: The first stage involves sorbite treatment, with the treatment temperature controlled at 450~500℃ and the holding time at 15~25min; inert gas is used for heating, with a heating rate of 5~8℃ / min. The second stage involves molten salt quenching and isothermal treatment; molten salt at 320~340℃ is used, and the isothermal time is 20~25min; the quenching cooling rate is controlled at 20~25℃ / s. The third stage involves low-temperature composite stress relief and aging strengthening treatment. First, the wire rod is placed at 200~220℃ for 1~1.2h, while intermittent ultrasonic impact is used to assist stress relief. The ultrasonic power is 1.5~2.0kw and the frequency is 20~30kHz. Every 30~40s of impact is followed by a 240~300s pause. Then, the temperature is raised to 295~320℃ and held for 1~1.2h for aging strengthening.

[0008] Furthermore, in step S1, the melting adopts vacuum induction melting, the melting temperature is 1620~1650℃, the holding time is 40~60min; the refining vacuum degree is ≤5Pa, the refining time is 60~90min; and the continuous casting speed is 0.8~1.2 m / min.

[0009] Furthermore, in step S2, the heating adopts a segmented heating method: the heating rate from room temperature to 500℃ is ≤100℃ / h, the heating rate from 500 to 800℃ is 120 to 150℃ / h, and the heating rate from 800 to 1200℃ is ≤100℃ / h; the final heating temperature is 1180 to 1210℃, and the holding time is 2.5 to 3.5h.

[0010] Furthermore, in step S3, multi-pass gradient reduction rolling is adopted, with a cumulative reduction rate of ≥70% in roughing, ≥60% in intermediate rolling, and ≥55% in finishing rolling, and the reduction rate of each finishing rolling pass is controlled at 10~15%; after rolling, water mist pre-cooling is adopted, with a cooling rate of 5~8 ℃ / s, to stabilize the billet temperature in the range of 845~852℃ before entering the wire drawing process.

[0011] Furthermore, in step S4, the wire drawing temperature is 830~840℃, and after wire drawing, air cooling is used at a rate of 3~5℃ / s to reduce the wire rod temperature to 320~350℃. The temperature is maintained for 4~6 hours, and then the wire rod is cooled to room temperature in the furnace.

[0012] Furthermore, in step S5, the surface of the wire rod is phosphated before drawing. The phosphated temperature is 50~60℃ and the phosphated time is 15~20min. Graphite lubricant is used for lubrication.

[0013] Furthermore, in step S6, the aging strengthening stage employs argon gas protection, with an argon gas flow rate of 0.3~0.5 m³ / h. 3 / h.

[0014] To better achieve the objectives of this invention, this invention also provides a high-strength, low-residual-stress wire rod prepared according to the preparation method described above.

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: This invention optimizes the composition of the steel billet: C: 0.01~0.022%, Mn: 0.235~0.528%, Si: 0.035~0.064%, Li: 0.001~0.002%, Zr: 0.005~0.011%, Sr: 0.001~0.006%, V: 0.008~0.021%, Nb: 0.006~0.013%, Ti: 0.01~0.025%, two or three of Re, Cr, and Cu are 0.02~0.1wt%, S≤0.020%, P≤0.020%, and the balance is Fe and unavoidable impurities; and limits the following relationship to be satisfied: 2.19≤ ≤4.62. The wire rod prepared by segmented heating of steel billet, multi-pass gradient rolling, wire drawing, cold drawing and three-stage heat treatment has the characteristics of high strength and low residual stress. The tensile strength of the high strength and low residual stress wire rod is ≥1235MPa; yield strength is ≥803MPa; reduction of area is ≥45% and residual stress is ≤68MPa. Detailed Implementation

[0016] 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 in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] Example 1: A method for preparing a high-strength, low-residual-stress wire rod, comprising the following steps: S1. The raw materials are smelted and refined, and steel billets are continuously cast to obtain steel billets; the steel billets contain the following components by weight percentage: C: 0.01%, Mn: 0.528%, Si: 0.035%, Li: 0.002%, Zr: 0.005%, Sr: 0.006%, V: 0.008%, Nb: 0.013%, Ti: 0.025%, two or three of Re, Cr and Cu at 0.1wt%, S≤0.020%, P≤0.020%, and the balance is Fe and unavoidable impurities; =2.46.

[0018] The smelting process employed vacuum induction melting at a temperature of 1620℃ for 60 minutes; refining utilized VD vacuum refining technology at a vacuum level of 5 Pa for 60 minutes; and continuous casting employed an arc-shaped continuous casting machine with a casting speed of 1.2 m / min and a cooling water flow rate of 30 m³ / min for the crystallizer. 3 / h.

[0019] S2. The steel billet is fed into a heating furnace for heating; The heating process employs a segmented heating method, with a heating rate of 100 ℃ / h for the stage from room temperature to 500℃, 120 ℃ / h for the stage from 500 to 800℃, and 100 ℃ / h for the stage from 800 to 1200℃; the final heating temperature is 1210℃, and the holding time is 2.5h.

[0020] S3. The steel billet is rolled at a rolling temperature of 840℃, a friction coefficient of 0.4, and a rolling speed of 16 m / s. The process employs multi-pass gradient reduction rolling, with a cumulative reduction rate of 70% in roughing, 60% in intermediate rolling, and 55% in finishing rolling. The reduction rate per finishing pass is controlled at 10% to avoid stress concentration caused by uneven deformation. After rolling, water mist pre-cooling is used at a cooling rate of 8 ℃ / s to stabilize the billet temperature in the range of 845~852℃ before entering the wire drawing process.

[0021] S4. Use a wire spinneret to spin wire into wire rod; The wire drawing temperature is 830℃. After wire drawing, air cooling is used at a rate of 5℃ / s to reduce the wire rod temperature to 320℃. The wire rod is then held at this temperature for 6 hours and then cooled to room temperature in the furnace to initially release the residual rolling stress.

[0022] S5. The wire rod is subjected to a cold drawing process. The cold drawing adopts a multi-pass continuous drawing, with a deformation of 8% per pass and a cumulative deformation of 50%. Before drawing, the surface of the wire rod is phosphated (phosphating temperature 50℃, phosphating time 20min) and lubricated with graphite lubricant. During the drawing process, the drawing speed is controlled at 3 m / s and the drawing tension is 120N. After every 3 passes of drawing, low-temperature stress relief annealing is performed (220℃, holding for 20min) to avoid the accumulation of drawing stress.

[0023] S6. Perform three-stage heat treatment on the wire rod: The first stage involves sorbite treatment at a temperature of 450℃ for 25 minutes, protected by an inert gas (argon) at a heating rate of 5℃ / min.

[0024] The second stage involves molten salt quenching and isothermal treatment; molten salt at 320℃ is used, and the isothermal time is 25 minutes; the quenching cooling rate is controlled at 20℃ / s.

[0025] The third stage involves low-temperature composite stress relief and aging strengthening treatment. First, the wire rod is held at 200℃ for 1.2 hours, while intermittent ultrasonic impact is used to assist stress relief (ultrasonic power 1.5 kW, frequency 30 kHz, impact for 30 seconds + pause for 300 seconds). Then, the temperature is raised to 295℃ and held for 1.2 hours for aging strengthening. Argon gas protection is used during the aging strengthening stage, with an argon gas flow rate of 0.3 m³ / h. 3 / h.

[0026] Performance of high-strength, low-residual-stress wire rod: tensile strength 1235MPa (GB / T 228.1-2021); yield strength 803MPa (GB / T 228.1-2021); reduction of area 45% (GB / T 228.1-2021); residual stress 68MPa (GB / T7704-2017).

[0027] Example 2: A method for preparing a high-strength, low-residual-stress wire rod, comprising the following steps: S1. The raw materials are smelted and refined, and steel billets are continuously cast to obtain steel billets; the steel billets contain the following components by weight percentage: C: 0.022%, Mn: 0.235%, Si: 0.064%, Li: 0.001%, Zr: 0.011%, Sr: 0.001%, V: 0.021%, Nb: 0.006%, Ti: 0.01%, two or three of Re, Cr and Cu are 0.02wt%, S≤0.020%, P≤0.020%, and the balance is Fe and unavoidable impurities; =4.62.

[0028] The smelting process employed vacuum induction melting at a temperature of 1650℃ for 40 minutes; refining utilized VD vacuum refining technology at a vacuum level of 4.5 Pa for 90 minutes; and continuous casting employed an arc-shaped continuous casting machine with a casting speed of 0.8 m / min and a cooling water flow rate of 40 m³ / min for the crystallizer. 3 / h.

[0029] S2. The steel billet is fed into a heating furnace for heating; The heating process employs a segmented heating method, with a heating rate of 90 ℃ / h from room temperature to 500℃, a heating rate of 150 ℃ / h from 500 to 800℃, and a heating rate of 90 ℃ / h from 800 to 1200℃; the final heating temperature is 1180℃, and the holding time is 3.5h.

[0030] S3. The steel billet is rolled at a rolling temperature of 860℃, a friction coefficient of 0.3, and a rolling speed of 18 m / s. The process employs multi-pass gradient reduction rolling, with a cumulative reduction rate of 72% in roughing, 63% in intermediate rolling, and 58% in finishing rolling. The reduction rate per finishing pass is controlled at 15% to avoid stress concentration caused by uneven deformation. After rolling, water mist pre-cooling is used at a cooling rate of 5 ℃ / s to stabilize the billet temperature in the range of 845~852℃ before entering the wire drawing process.

[0031] S4. Use a wire spinneret to spin wire into wire rod; The wire drawing temperature is 840℃. After wire drawing, air cooling is used at a rate of 3℃ / s to reduce the wire rod temperature to 350℃. The wire rod is then held at this temperature for 4 hours and then cooled to room temperature in the furnace to initially release the residual rolling stress.

[0032] S5. The wire rod is subjected to a cold drawing process. The cold drawing adopts a multi-pass continuous drawing, with a deformation of 12% per pass and a cumulative deformation of 40%. Before drawing, the surface of the wire rod is phosphated (phosphating temperature 60℃, phosphating time 15min) and lubricated with graphite lubricant. During the drawing process, the drawing speed is controlled at 5 m / s and the drawing tension is 80N. After every 4 passes of drawing, low-temperature stress-relieving annealing is performed (200℃, holding for 30min) to avoid the accumulation of drawing stress.

[0033] S6. Perform three-stage heat treatment on the wire rod: The first stage involves sorbite treatment at a temperature of 500℃ for 15 minutes, with inert gas (argon) used for heating at a rate of 8℃ / min.

[0034] The second stage involves molten salt quenching and isothermal treatment; molten salt at 340℃ is used, and the isothermal time is 20 minutes; the quenching cooling rate is controlled at 25℃ / s.

[0035] The third stage involves low-temperature composite stress relief and aging strengthening treatment. First, the wire rod is held at 220℃ for 1 hour, while intermittent ultrasonic impact is used for stress relief (ultrasonic power 2.0 kW, frequency 20 kHz, impact for 40 seconds + pause for 240 seconds). Then, the temperature is raised to 320℃ and held for 1 hour for aging strengthening. Argon gas is used for protection during the aging strengthening stage, with an argon gas flow rate of 0.5 m³ / h. 3 / h.

[0036] Performance of high-strength, low-residual-stress wire rod: tensile strength 1251 MPa; yield strength 823 MPa; reduction of area 47%; residual stress 59 MPa.

[0037] Example 3: A method for preparing a high-strength, low-residual-stress wire rod, comprising the following steps: S1. The raw materials are smelted and refined, and steel billets are continuously cast to obtain steel billets; the steel billets contain the following components by weight percentage: C: 0.020%, Mn: 0.315%, Si: 0.044%, Li: 0.0015%, Zr: 0.009%, Sr: 0.005%, V: 0.019%, Nb: 0.011%, Ti: 0.017%, two or three of Re, Cr and Cu are 0.08wt%, S≤0.020%, P≤0.020%, and the balance is Fe and unavoidable impurities; =2.19.

[0038] The smelting process employed vacuum induction melting at a temperature of 1635℃ for 50 minutes; refining utilized VD vacuum refining technology at a vacuum level of 5 Pa for 70 minutes; and continuous casting employed an arc-shaped continuous casting machine with a casting speed of 1.1 m / min and a crystallizer cooling water flow rate of 35 m³ / min. 3 / h.

[0039] S2. The steel billet is fed into a heating furnace for heating; The heating process employs a segmented heating method: a heating rate of 100 ℃ / h for the stage from room temperature to 500℃, a heating rate of 130 ℃ / h for the stage from 500 to 800℃, and a heating rate of 100 ℃ / h for the stage from 800 to 1200℃; the final heating temperature is 1200℃, and the holding time is 3 hours.

[0040] S3. The steel billet is rolled at a rolling temperature of 855℃, a friction coefficient of 0.3, and a rolling speed of 16.5 m / s. The process employs multi-pass gradient reduction rolling, with a cumulative reduction rate of 70% in roughing, 60% in intermediate rolling, and 55% in finishing rolling. The reduction rate per finishing pass is controlled at 12% to avoid stress concentration caused by uneven deformation. After rolling, water mist pre-cooling is used at a cooling rate of 6.5 ℃ / s to stabilize the billet temperature in the range of 845~852℃ before entering the wire drawing process.

[0041] S4. Use a wire spinneret to spin wire into wire rod; The wire drawing temperature is 835℃. After wire drawing, air cooling is used at a rate of 4℃ / s to reduce the wire rod temperature to 330℃. The wire rod is then held at this temperature for 5 hours and then cooled to room temperature in the furnace to initially release the residual rolling stress.

[0042] S5. The wire rod is subjected to a cold drawing process. The cold drawing adopts a multi-pass continuous drawing, with a deformation of 10% per pass and a cumulative deformation of 45%. Before drawing, the surface of the wire rod is phosphated (phosphating temperature 55℃, phosphating time 18min) and lubricated with graphite lubricant. During the drawing process, the drawing speed is controlled at 4 m / s and the drawing tension is 100N. After every 3 passes of drawing, low-temperature stress-relieving annealing is performed (210℃, holding for 25min) to avoid the accumulation of drawing stress.

[0043] S6. Perform three-stage heat treatment on the wire rod: The first stage involves sorbite treatment at a temperature of 480℃ for 20 minutes, protected by an inert gas (argon) at a heating rate of 6℃ / min.

[0044] The second stage involves molten salt quenching and isothermal treatment; molten salt at 330℃ is used, and the isothermal time is 22 minutes; the quenching cooling rate is controlled at 23℃ / s.

[0045] The third stage involves low-temperature composite stress relief and aging strengthening treatment. First, the wire rod is held at 210℃ for 1 hour, while intermittent ultrasonic impact is used to assist stress relief (ultrasonic power 1.8 kW, frequency 25 kHz, impact for 35 seconds + pause for 280 seconds). Then, the temperature is raised to 300℃ and held for 1 hour for aging strengthening. Argon gas is used for protection during the aging strengthening stage, with an argon gas flow rate of 0.4 m³ / h. 3 / h.

[0046] Performance of high-strength, low-residual-stress wire rod: tensile strength 1243 MPa; yield strength 816 MPa; reduction of area 46%; residual stress 63 MPa.

[0047] Comparative Example 1: Unlike Example 3, in S1, the raw materials were smelted and refined, and a steel billet was obtained by continuous casting; the steel billet contained the following components by weight percentage: C: 0.020%, Mn: 0.315%, Si: 0.044%, Li: 0.001%, Zr: 0.009%, Sr: 0.0055%, V: 0.019%, Nb: 0.018%, Ti: 0.01%, two or three of Re, Cr, and Cu were 0.08wt%, S≤0.020%, P≤0.020%, and the balance was Fe and unavoidable impurities; =2.0.

[0048] Tested wire rod performance: tensile strength 1180MPa; yield strength 755MPa; reduction of area 41%; residual stress 78MPa.

[0049] Comparative Example 2: Unlike Example 3, in S1, the raw materials were smelted and refined, and a steel billet was obtained by continuous casting; the steel billet contained the following components by weight percentage: C: 0.020%, Mn: 0.315%, Si: 0.044%, Li: 0.001%, Zr: 0.009%, Sr: 0.002%, V: 0.019%, Nb: 0.013%, Ti: 0.025%, two or three of Re, Cr, and Cu at 0.08wt%, S≤0.020%, P≤0.020%, and the balance being Fe and unavoidable impurities; =6.81.

[0050] Tested wire rod performance: tensile strength 1320MPa; yield strength 880MPa; reduction of area 32%; residual stress 85MPa.

[0051] Comparative Example 3: Unlike Example 3, S6 involves a three-stage heat treatment of the wire rod. The first stage involves sorbite treatment at a temperature of 480℃ for 20 minutes, protected by an inert gas (argon) at a heating rate of 6℃ / min.

[0052] The second stage involves molten salt quenching and isothermal treatment; molten salt at 330℃ is used, and the isothermal time is 22 minutes; the quenching cooling rate is controlled at 23℃ / s.

[0053] The third stage involves low-temperature composite stress relief and aging strengthening treatment. First, the wire rod is held at 210℃ for 1 hour; then the temperature is raised to 300℃ and held for 1 hour for aging strengthening. Argon gas is used for protection during the aging strengthening stage, with an argon gas flow rate of 0.4 m³ / h.3 / h.

[0054] Tested wire rod performance: tensile strength 1185MPa; yield strength 758MPa; reduction of area 40%; residual stress 92MPa.

[0055] Comparative Example 4: Unlike Example 3, step S5 is not performed.

[0056] The performance of the wire rod was tested as follows: tensile strength 1042 MPa; yield strength 675 MPa; reduction of area 53%; residual stress 51 MPa.

[0057] Comparative Example 5: Unlike Example 3, step S5 is omitted; and step S6 is as follows: The first stage involves sorbite treatment at a temperature of 480℃ for 20 minutes, protected by an inert gas (argon) at a heating rate of 6℃ / min.

[0058] The second stage involves molten salt quenching and isothermal treatment; molten salt at 330℃ is used, and the isothermal time is 22 minutes; the quenching cooling rate is controlled at 23℃ / s.

[0059] The third stage involves low-temperature composite stress relief and aging strengthening treatment. First, the wire rod is held at 210℃ for 1 hour; then the temperature is raised to 300℃ and held for 1 hour for aging strengthening. Argon gas is used for protection during the aging strengthening stage, with an argon gas flow rate of 0.4 m³ / h. 3 / h.

[0060] The performance of the wire rod was tested as follows: tensile strength 978 MPa; yield strength 618 MPa; reduction of area 47%; residual stress 86 MPa.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength, low-residual-stress wire rod, characterized in that, The raw materials include the following weight percentages: C: 0.01~0.022%, Mn: 0.235~0.528%, Si: 0.035~0.064%, Li: 0.001~0.002%, Zr: 0.005~0.011%, Sr: 0.001~0.006%, V: 0.008~0.021%, Nb: 0.006~0.013%, Ti: 0.01~0.025%, two or three of Re, Cr, and Cu at 0.02~0.1wt%, S≤0.020%, P≤0.020%, and the balance being Fe and unavoidable impurities; And it satisfies the following relationship: 2.19≤ ≤4.62 The high-strength, low-residual-stress wire rod has a tensile strength ≥1235MPa, a yield strength ≥803MPa, a reduction of area ≥45%, and a residual stress ≤68MPa.

2. A method for preparing high-strength, low-residual-stress wire rod according to claim 1, characterized in that, Includes the following steps: S1. The raw materials are smelted and refined, and then continuously cast to obtain steel billets; S2. The steel billet is fed into a heating furnace for heating; S3. The steel billet is rolled at a rolling temperature of 840~860℃, a friction coefficient of 0.3~0.4, and a rolling speed of 16~18 m / s. S4. Use a wire spinneret to spin wire into wire rod; S5. The wire rod is subjected to cold drawing process. The cold drawing adopts multi-pass continuous drawing, with a deformation of 8~12% per pass and a cumulative deformation of 40~50%. During the drawing process, the drawing speed is controlled at 3~5 m / s and the drawing tension is 80~120N. Stress relief annealing is performed after every 3~4 passes of drawing. S6. Perform three-stage heat treatment on the wire rod: The first stage involves sorbite treatment, with the treatment temperature controlled at 450~500℃ and the holding time at 15~25min. Inert gas is used for heating, with a heating rate of 5~8℃ / min; The second stage involves molten salt quenching and isothermal treatment; molten salt at 320~340℃ is used, and the isothermal time is 20~25min; the quenching cooling rate is controlled at 20~25℃ / s. The third stage involves low-temperature composite stress relief and aging strengthening treatment. First, the wire rod is placed at 200~220℃ for 1~1.2h, while intermittent ultrasonic impact is used to assist stress relief. The ultrasonic power is 1.5~2.0kw and the frequency is 20~30kHz. Every 30~40s of impact is followed by a 240~300s pause. Then, the temperature is raised to 295~320℃ and held for 1~1.2h for aging strengthening.

3. The method for preparing high-strength, low-residual-stress wire rod according to claim 2, characterized in that, In step S1, vacuum induction melting is used for smelting, with a smelting temperature of 1620~1650℃ and a holding time of 40~60min; the refining vacuum degree is ≤5Pa and the refining time is 60~90min; the continuous casting speed is 0.8~1.2 m / min.

4. The method for preparing high-strength, low-residual-stress wire rod according to claim 3, characterized in that, In step S2, the heating is carried out in stages: the heating rate from room temperature to 500℃ is ≤100℃ / h, the heating rate from 500 to 800℃ is 120 to 150℃ / h, and the heating rate from 800 to 1200℃ is ≤100℃ / h; the final heating temperature is 1180 to 1210℃, and the holding time is 2.5 to 3.5h.

5. The method for preparing high-strength, low-residual-stress wire rod according to claim 4, characterized in that, In step S3, multi-pass gradient reduction rolling is adopted, with a cumulative reduction rate of ≥70% in roughing, ≥60% in intermediate rolling, and ≥55% in finishing rolling. The reduction rate of each finishing rolling pass is controlled at 10~15%. After rolling, water mist pre-cooling is adopted with a cooling rate of 5~8 ℃ / s to stabilize the billet temperature in the range of 845~852℃ before entering the wire drawing process.

6. The method for preparing high-strength, low-residual-stress wire rod according to claim 5, characterized in that, In step S4, the wire drawing temperature is 830~840℃. After wire drawing, air cooling is used at a rate of 3~5℃ / s to reduce the wire rod temperature to 320~350℃. The temperature is maintained for 4~6 hours, and then the wire rod is cooled to room temperature in the furnace.

7. The method for preparing high-strength, low-residual-stress wire rod according to claim 6, characterized in that, In step S5, the surface of the wire rod is phosphated before drawing. The phosphated temperature is 50~60℃ and the phosphated time is 15~20min. Graphite lubricant is used for lubrication.

8. The method for preparing high-strength, low-residual-stress wire rod according to claim 7, characterized in that, In step S6, argon gas protection is used during the aging strengthening stage, with an argon gas flow rate of 0.3~0.5 m³ / h. 3 / h.

9. A high-strength, low-residual-stress wire rod prepared by the preparation method according to any one of claims 2 to 8.