Medical austenitic stainless steel straight wire and method of heat treating the same

Abstract

The present application relates to a kind of medical austenitic stainless steel straight state wire and its heat treatment method.It solves the defects such as unreasonable design of prior art.The present heat treatment method includes the following steps:S1, drawing austenitic stainless steel straight state wire is pretreated;S2, austenitic stainless steel straight state wire after S1 processing is placed in atmosphere continuous furnace, and austenitic stainless steel straight state wire is gradiently heated and is treated by multi-stage heating;S3, austenitic stainless steel straight state wire after heating in S2 is transferred to isothermal zone and is treated by heat preservation, and austenitic stainless steel straight state wire after heat preservation in isothermal zone is treated by gradiently multi-stage cooling;S4, austenitic stainless steel straight state wire after cooling in S3 is treated by low-temperature stress relieving tempering, and after tempering, post-processing is carried out, and austenitic stainless steel straight state wire product is obtained.The present application has the advantages that internal stress is completely eliminated: segmented heating and low-temperature tempering synergistic effect, internal stress elimination rate reaches 90% or more, and subsequent processing deformation amount is ≤0.3mm / m.

Description

Technical Field

[0001] This invention belongs to the field of medical materials technology, and particularly relates to a medical austenitic stainless steel straight wire and its heat treatment method. Background Technology

[0002] Austenitic stainless steel, due to its non-magnetic properties, excellent corrosion resistance, and high strength and toughness, is widely used in machinery manufacturing, construction, aerospace, and other fields. It is particularly prevalent in the medical field, used in implantable devices and medical sutures. Commonly used medical stainless steel wires are formed through drawing processes; however, drawing generates significant internal stress, leading to easy bending and deformation of the wire, poor dimensional stability, and a fibrous microstructure after drawing. This results in corrosion resistance and fatigue life that fail to meet the stringent requirements of medical implantable devices. Therefore, annealing heat treatment is often used to eliminate residual stress within the wire. However, existing heat treatment methods have the following shortcomings: 1. Incomplete elimination of internal stress: Traditional single-stage annealing processes often use a heat preservation temperature of 600-800℃, and the internal stress elimination rate is only 60-70%. After subsequent processing or implantation into the human body, the stress release can easily cause deformation, affecting the accuracy of the device.

[0003] 2. Insufficient corrosion resistance: Microcracks and oxide layers are easily formed on the surface during the drawing process. Existing processes have limited improvement on the surface condition. The wire is prone to pitting corrosion in the human body fluid environment, which reduces biocompatibility.

[0004] 3. Straightness is difficult to guarantee: Uneven heating and cooling during heat treatment can easily cause the wire to bend, requiring an additional straightening process, which not only increases costs but may also introduce new stress damage. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a medical austenitic stainless steel straight wire and its heat treatment method.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions: The heat treatment method for this medical austenitic stainless steel straight wire includes the following steps: S1. Pretreatment is performed on straight wires of drawn austenitic stainless steel. S2. The straight austenitic stainless steel wire after the treatment in S1 is placed in a continuous atmosphere furnace, and the straight austenitic stainless steel wire is subjected to a multi-stage heating treatment with gradient heating; the heating rate of the multi-stage heating treatment is decreasing, and the heating temperature of the multi-stage heating treatment is increasing. S3. The austenitic stainless steel straight wire heated in S2 is transferred to an isothermal zone for heat preservation treatment, and the austenitic stainless steel straight wire after heat preservation treatment in the isothermal zone is subjected to gradient multi-stage cooling treatment. S4. The cooled austenitic stainless steel straight wire described in S3 is subjected to low-temperature stress-relieving tempering treatment, and the tempering treatment is followed by post-treatment to obtain the finished austenitic stainless steel straight wire.

[0007] In the above-mentioned heat treatment method for straight austenitic stainless steel wire for medical use, in S2, the multi-stage heating treatment is a three-stage heating treatment, defined as a first stage, a second stage, and a third stage. The first stage heats up to 450-500 ℃ at a rate of 5-8 ℃ / min and holds for 30-40 min; the second stage heats up to 700-750 ℃ ​​at a rate of 3-5 ℃ / min and holds for 20-30 min; the third stage heats up to 900-950 ℃ at a rate of 2-3 ℃ / min and holds for 15-25 min.

[0008] In the above-mentioned heat treatment method for straight austenitic stainless steel wire for medical use, argon gas with a purity of ≥99.99% is introduced into the continuous atmosphere furnace as a protective gas, the gas flow rate is 0.8-1.2L / min, and the furnace pressure is maintained at 0.1-0.12Mpa.

[0009] In the above-mentioned heat treatment method for straight austenitic stainless steel wire for medical use, in step S3, the temperature of the isothermal zone is 800-850℃, and the holding time of the isothermal zone is 10-15 minutes.

[0010] In the above-mentioned heat treatment method for straight austenitic stainless steel wire for medical use, the gradient multi-stage cooling treatment is a three-stage gradient multi-stage cooling treatment, defined as a first-stage cooling, a second-stage cooling, and a third-stage cooling. The first-stage cooling is at a rate of 10-15℃ / min to 600℃; the second-stage cooling is at a rate of 5-8℃ / min to 300℃; and the third-stage cooling is a final furnace cooling to room temperature.

[0011] In the above-mentioned heat treatment method for medical austenitic stainless steel straight wire, in S4 above, the low-temperature stress-relieving tempering treatment includes: placing the cooled austenitic stainless steel straight wire into a tempering furnace, holding it at 200-250 ℃ for 40-60 min, and air-cooling it to room temperature after the holding period; argon gas is continuously introduced for protection during the tempering process.

[0012] In the above-described heat treatment method for straight austenitic stainless steel wire for medical use, in step S1, the pretreatment includes sequential ultrasonic cleaning and passivation.

[0013] In the above-mentioned heat treatment method for straight austenitic stainless steel wire for medical use, the ultrasonic cleaning uses a medical-grade alkaline cleaning agent with pH=8.5-9.5, an ultrasonic power of 300-400 W, and a cleaning time of 15-20 min; the passivation treatment uses a 5-8% nitric acid solution, soaks at room temperature for 20-30 s, then rinses with deionized water until neutral, and dries with nitrogen.

[0014] In the above-mentioned heat treatment method for straight austenitic stainless steel wire for medical use, in S4, the post-treatment includes surface finishing, and the surface finishing is performed by polishing the tempered wire with a centerless grinder. After polishing, the straightness of the wire is ≤0.5mm / m and the surface roughness Ra is ≤0.2μm.

[0015] This application also provides a straight austenitic stainless steel wire for medical use, which is prepared by the heat treatment method described above, and the straight austenitic stainless steel wire for medical use has a tensile strength ≥2600MPa and an elongation ≥2.0%.

[0016] Compared with existing technologies, the advantages of this application are: Thorough elimination of internal stress: The combined effect of segmented heating and low-temperature tempering results in an internal stress elimination rate of over 90%, significantly improving the dimensional stability of the wire and reducing subsequent processing deformation to ≤0.3mm / m.

[0017] Excellent overall performance: Three-stage heating refines austenite grains, gradient cooling ensures uniform microstructure, and the finished wire has a tensile strength of 2600MPa and an elongation of ≥2.0%; passivation and polishing treatments increase the surface pitting potential to over 1.2V, meeting the corrosion resistance requirements of medical implant materials.

[0018] Good straightness and low cost: Precise temperature control and gradient cooling avoid wire bending, eliminating the need for additional straightening processes. After surface finishing, the straightness is ≤0.5mm / m, increasing production efficiency by 25-30%. Attached Figure Description

[0019] Figure 1 This is a flowchart of the heat treatment method for straight austenitic stainless steel wire for medical use provided by the present invention.

[0020] Figure 2 This is a metallographic screenshot of the straight-state wire of medical austenitic stainless steel provided by the present invention.

[0021] Figure 3 These are X-ray diffraction comparison images of the straight-state medical austenitic stainless steel wire before and after heat treatment provided by this invention.

[0022] Figure 4 yes Figure 3 Figure (a) in the middle.

[0023] Figure 5 yes Figure 3 Figure (b) in the middle. Detailed Implementation

[0024] The following are specific embodiments of the invention, which are described in conjunction with the accompanying drawings. The technical solution of the invention will be further described, but the invention is not limited to these embodiments.

[0025] like Figures 1-2 As shown, this embodiment provides a heat treatment method for straight austenitic stainless steel wire for medical use, including the following steps: S1 pretreatment, S2 segmented heating treatment, S3 isothermal and gradient cooling treatment, and S4 low-temperature stress-relieving tempering treatment.

[0026] Specifically, S1, drawn austenitic stainless steel straight wire undergoes pretreatment; and the pretreatment includes sequential ultrasonic cleaning and passivation.

[0027] Furthermore, ultrasonic cleaning uses a medical-grade alkaline cleaning agent with a pH of 8.5-9.5, an ultrasonic power of 300-400 W, and a cleaning time of 15-20 min; Secondly, the passivation treatment uses a 5-8% nitric acid solution, soaking at room temperature for 20-30 seconds, followed by rinsing with deionized water until neutral, and then drying with nitrogen.

[0028] S2. The straight austenitic stainless steel wire after S1 treatment is placed in a continuous atmosphere furnace. Argon gas with a purity of ≥99.99% is introduced into the furnace as a protective gas with a flow rate of 0.8-1.2L / min and the furnace pressure is maintained at 0.1-0.12Mpa.

[0029] The heating rate of the multi-stage heating treatment is decreasing, and the heating temperature is increasing. Specifically, austenitic stainless steel straight wire is subjected to a gradient heating multi-stage heating treatment. The multi-stage heating treatment is a three-stage heating treatment, defined as the first stage, the second stage, and the third stage. The first stage heats up to 450-500 ℃ at a rate of 5-8 ℃ / min and holds for 30-40 min. The second stage heats up to 700-750 ℃ ​​at a rate of 3-5 ℃ / min and holds for 20-30 min. The third stage heats up to 900-950 ℃ at a rate of 2-3 ℃ / min and holds for 15-25 min.

[0030] S3. Transfer the heated austenitic stainless steel straight wire from S2 to an isothermal zone for heat preservation. In this embodiment, the temperature of the isothermal zone is 800-850℃, and the heat preservation time in the isothermal zone is 10-15 minutes.

[0031] Secondly, the straight austenitic stainless steel wires after isothermal heat preservation are subjected to gradient multi-stage cooling treatment. The gradient multi-stage cooling treatment is a three-stage gradient multi-stage cooling treatment, defined as the first stage cooling, the second stage cooling and the third stage cooling. The first stage cooling is cooled to 600℃ at a rate of 10-15℃ / min; the second stage cooling is cooled to 300℃ at a rate of 5-8℃ / min; and the third stage cooling is the final furnace cooling to room temperature.

[0032] S4. The cooled austenitic stainless steel straight wire from S3 is subjected to low-temperature stress-relief tempering treatment. The low-temperature stress-relief tempering treatment includes: placing the cooled austenitic stainless steel straight wire into a tempering furnace and holding it at 200-250 ℃ for 40-60 min. After the holding period, it is air-cooled to room temperature. Argon gas is continuously introduced for protection during the tempering process, and the finished austenitic stainless steel straight wire is obtained.

[0033] After tempering, post-treatment is carried out, including surface finishing. The surface finishing is performed by polishing the tempered wire with a centerless grinder. After polishing, the straightness of the wire is ≤0.5mm / m and the surface roughness Ra≤0.2μm.

[0034] The medical-grade austenitic stainless steel straight wire prepared using the above heat treatment method exhibits the following characteristics: three-stage heating refines the austenitic grains, gradient cooling ensures uniform microstructure, resulting in a tensile strength ≥2600MPa (finished wire) and elongation ≥2.0%. Furthermore, the synergistic effect of segmented heating and low-temperature tempering achieves an internal stress relief rate exceeding 90%, significantly improving the dimensional stability of the wire, with subsequent processing deformation ≤0.3mm / m. Passivation and polishing treatments raise the surface pitting potential to above 1.2V, meeting the corrosion resistance requirements for medical implant materials.

[0035] Good straightness and low cost: Precise temperature control and gradient cooling avoid wire bending, eliminating the need for additional straightening processes. After surface finishing, the straightness is ≤0.5mm / m, increasing production efficiency by 25-30%.

[0036] Example 1, as Figure 1 As shown, the heat treatment method for straight austenitic stainless steel wire in this embodiment includes the following steps: S1, Pretreatment ultrasonic cleaning: Prepare a medical-grade alkaline cleaning agent with pH=9.0 (composition: 0.5% sodium hydroxide + 0.3% sodium carbonate + deionized water), put the medical austenitic stainless steel straight wire into the cleaning tank, set the ultrasonic power to 350W, and the ultrasonic cleaning time to 18min to remove surface drawing oil and impurities.

[0037] S2, multi-stage heating treatment: The pretreated medical austenitic stainless steel straight wires are evenly arranged on the quartz carrier of the controlled atmosphere continuous furnace. The spacing between the medical austenitic stainless steel straight wires is ≥2mm to avoid stacking. First stage of heating: Heat to 480℃ at a rate of 5℃ / min, hold at the temperature for 35min after reaching the temperature, introduce argon gas with a purity of ≥99.99% into the furnace, and maintain the pressure in the furnace at 0.11MPa; The second stage of heating: the temperature is increased to 720℃ at a rate of 3℃ / min, and held for 25min, while the argon flow rate and furnace pressure remain unchanged; The third stage of heating: the temperature is increased to 920℃ at a rate of 2℃ / min, and held for 20min, while the argon flow rate and furnace pressure remain unchanged.

[0038] S3, Isothermal and Gradient Cooling Treatment: After heating, the straight wire of medical austenitic stainless steel is quickly transferred to the isothermal zone in the furnace along with the material carrier. The isothermal temperature is set to 820℃ and held for 12 minutes. Gradient cooling: First, cool to 600℃ at a rate of 12℃ / min, then cool to 300℃ at a rate of 6℃ / min, and finally turn off the heating device and cool to room temperature (≤25℃) with the furnace.

[0039] S4, Low-temperature stress-relief tempering treatment: S40 transfers the cooled wire into the tempering furnace, sets the tempering temperature to 220℃, and holds it for 50 minutes; Protective cooling: Argon gas with a purity of 99.99% is continuously introduced during the tempering process, and after the holding time is completed, the furnace door is opened and the material is air-cooled to room temperature.

[0040] S41 Surface Finishing and Coreless Polishing: The wire is polished using a coreless grinder with an 800# diamond wheel and a polishing rate of 1.5m / min. Precision Inspection: After polishing, the straightness of the wire is checked using a laser diameter gauge and the surface roughness is checked using a roughness tester to ensure that the straightness is ≤0.4mm / m and the surface roughness Ra≤0.18μm.

[0041] Example 2, as Figure 1 As shown, the heat treatment method for straight austenitic stainless steel wire in this embodiment includes the following steps: S1, Pretreatment ultrasonic cleaning: Prepare a medical-grade alkaline cleaning agent with pH=8.5 (composition: 0.6% sodium hydroxide + 0.4% sodium carbonate + deionized water), put the medical austenitic stainless steel straight wire into the cleaning tank, set the ultrasonic power to 400W, and the ultrasonic cleaning time to 20min to remove surface drawing oil and impurities.

[0042] S2, multi-stage heating treatment: The pretreated medical austenitic stainless steel straight wires are evenly arranged on the quartz carrier of the controlled atmosphere continuous furnace. The spacing between the medical austenitic stainless steel straight wires is ≥2mm to avoid stacking. First stage of heating: Heat to 450℃ at a rate of 8℃ / min, hold at the temperature for 40min, introduce argon gas with a purity of ≥99.99% into the furnace, and maintain the pressure inside the furnace at 0.12MPa; The second stage of heating: the temperature is increased to 700℃ at a rate of 5℃ / min, and held for 30min, while the argon flow rate and furnace pressure remain unchanged; The third stage of heating: the temperature is increased to 900℃ at a rate of 3℃ / min, and held for 25 minutes, while the argon flow rate and furnace pressure remain unchanged.

[0043] S3, Isothermal and Gradient Cooling Treatment: After heating, the straight wire of medical austenitic stainless steel is quickly transferred to the isothermal zone in the furnace along with the material carrier. The isothermal temperature is set to 800℃ and held for 15 minutes. Gradient cooling: First, cool to 600℃ at a rate of 15℃ / min, then cool to 300℃ at a rate of 8℃ / min, and finally turn off the heating device and cool to room temperature (≤25℃) with the furnace.

[0044] S4, Low-temperature stress-relief tempering treatment: S40 The cooled wire is transferred into the tempering furnace, the tempering temperature is set to 200℃, and the holding time is 60min; Protective cooling: Argon gas with a purity of 99.99% is continuously introduced during the tempering process, and after the holding time is completed, the furnace door is opened and the material is air-cooled to room temperature.

[0045] S41 Surface Finishing and Coreless Polishing: The wire is polished using a coreless grinder with an 800# diamond wheel and a polishing rate of 1.5m / min. Precision Inspection: After polishing, the straightness of the wire is checked using a laser diameter gauge and the surface roughness is checked using a roughness tester to ensure that the straightness is ≤0.4mm / m and the surface roughness Ra≤0.18μm.

[0046] Example 3, as Figure 1 As shown, the heat treatment method for straight austenitic stainless steel wire in this embodiment includes the following steps: S1, Pretreatment ultrasonic cleaning: Prepare a medical-grade alkaline cleaning agent with pH=9.5 (composition: 0.4% sodium hydroxide + 0.3% sodium carbonate + deionized water), put the medical austenitic stainless steel straight wire into the cleaning tank, set the ultrasonic power to 300W, and the ultrasonic cleaning time to 15min to remove surface drawing oil and impurities.

[0047] S2, multi-stage heating treatment: The pretreated medical austenitic stainless steel straight wires are evenly arranged on the quartz carrier of the controlled atmosphere continuous furnace. The spacing between the medical austenitic stainless steel straight wires is ≥2mm to avoid stacking. First stage of heating: Heat to 500℃ at a rate of 7℃ / min, hold at the temperature for 30min after reaching the temperature, introduce argon gas with a purity of ≥99.99% into the furnace, and maintain the pressure in the furnace at 0.10MPa; The second stage of heating: the temperature is increased to 750℃ at a rate of 4℃ / min, and held for 20min, while the argon flow rate and furnace pressure remain unchanged; The third stage of heating: the temperature is increased to 950℃ at a rate of 2.5℃ / min, and held for 15min, while the argon flow rate and furnace pressure remain unchanged.

[0048] S3, Isothermal and Gradient Cooling Treatment: After heating, the straight wire of medical austenitic stainless steel is quickly transferred to the isothermal zone in the furnace along with the material carrier. The isothermal temperature is set to 850℃ and held for 13 minutes. Gradient cooling: First, cool to 600℃ at a rate of 10℃ / min, then cool to 300℃ at a rate of 5℃ / min, and finally turn off the heating device and cool to room temperature (≤25℃) with the furnace.

[0049] S4, Low-temperature stress-relief tempering treatment: S40 transfers the cooled wire into the tempering furnace, sets the tempering temperature to 250℃, and holds it for 40 minutes; Protective cooling: Argon gas with a purity of 99.99% is continuously introduced during the tempering process, and after the holding time is completed, the furnace door is opened and the material is air-cooled to room temperature.

[0050] S41 Surface Finishing and Coreless Polishing: The wire is polished using a coreless grinder with an 800# diamond wheel and a polishing rate of 1.5m / min. Precision Inspection: After polishing, the straightness of the wire is checked using a laser diameter gauge and the surface roughness is checked using a roughness tester to ensure that the straightness is ≤0.4mm / m and the surface roughness Ra≤0.18μm.

[0051] Finally, the characterization of internal stress elimination in this embodiment is as follows: Figures 3-5 As shown, the material was tested using non-destructive X-ray diffraction (XRD) (compliant with GB / T 7704-2017 "Method for X-ray Stress Measurement"). Principle: Residual stress causes changes in lattice spacing. XRD detects the shift (macroscopic stress) and broadening (microscopic stress / lattice distortion) of diffraction peaks on specific crystal planes (such as the {220} plane of 316L).

[0052] The Bragg equation applies: 2dsinθ = nλ, where n is the diffraction order, d is the interplanar spacing (in Å or nm), θ is the angle between the incident X-ray and the crystal plane, and λ is the X-ray wavelength. Since stainless steel wire is formed through a drawing process, the wire rod is pulled out of the die through a drawing force, producing a small-section wire. Therefore, the stainless steel wire material is subjected to residual tensile stress, which increases the interplanar spacing (d increases) and shifts the peak position to a lower angle (2θ decreases).

[0053] According to the Scherrer equation: D = Kλ / (β cosθ), where D is the grain size, K is the Scherrer constant, λ is the X-ray wavelength, β is the full width at half maximum (FWHM) of the diffraction peak, and θ is the diffraction angle. As the grain size D decreases, the FWHM of the diffraction peak increases, resulting in a broader diffraction peak. Microscopic strain, dislocations, stacking faults, and other lattice distortions cause random changes in interplanar spacing, leading to broadening of the diffraction peak. Therefore, during the drawing process, the internal microstructure of the stainless steel wire deforms. External forces cause dislocation slip and grain boundary movement within the grains, elongating and breaking the original grains, thus forming a finer grain structure (decreasing D), increasing the FWHM of the diffraction peak, and broadening the diffraction peak.

[0054] Figure 4 - (a) is a comparison of X-ray diffraction patterns of the stainless steel wire used in this experiment before and after heat treatment. Figure 5 - (b) is a magnified view of the γ peak (200), where Intensity represents the intensity. For example... Figures 2-5 As shown, it can be observed that after the staged heat treatment method of this embodiment, the diffraction angle of the (200) γ peak shifts to a larger angle, the interplanar spacing decreases, and the full width at half maximum (FWHM) of the diffraction peak decreases. Therefore, the internal tensile stress is reduced to the point of elimination, the internal structural deformation of the material is reduced, and the structure is more uniform.

[0055] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A heat treatment method for straight austenitic stainless steel wire for medical use, characterized in that, The heat treatment method includes the following steps: S1. Pretreatment is performed on straight wires of drawn austenitic stainless steel. S2. The straight austenitic stainless steel wire after the treatment in S1 is placed in a continuous atmosphere furnace, and the straight austenitic stainless steel wire is subjected to a multi-stage heating treatment with gradient heating; the heating rate of the multi-stage heating treatment is decreasing, and the heating temperature of the multi-stage heating treatment is increasing. S3. The austenitic stainless steel straight wire heated in S2 is transferred to an isothermal zone for heat preservation treatment, and the austenitic stainless steel straight wire after heat preservation treatment in the isothermal zone is subjected to gradient multi-stage cooling treatment. S4. The cooled austenitic stainless steel straight wire described in S3 is subjected to low-temperature stress-relieving tempering treatment, and the tempering treatment is followed by post-treatment to obtain the finished austenitic stainless steel straight wire.

2. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 1, characterized in that, In S2 above, the multi-stage heating treatment is a three-stage heating treatment, defined as a first stage, a second stage, and a third stage. The first stage heats up to 450-500 ℃ at a rate of 5-8 ℃ / min and holds for 30-40 min. The second stage heats up to 700-750 ℃ ​​at a rate of 3-5 ℃ / min and holds for 20-30 min. The third stage heats up to 900-950 ℃ at a rate of 2-3 ℃ / min and holds for 15-25 min.

3. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 1, characterized in that, Argon gas with a purity of ≥99.99% is introduced into the continuous atmosphere furnace as a protective gas at a flow rate of 0.8-1.2 L / min, and the furnace pressure is maintained at 0.1-0.12 MPa.

4. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 1, characterized in that, In S3 above, the temperature of the isothermal zone is 800-850℃, and the holding time of the isothermal zone is 10-15 minutes.

5. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 4, characterized in that, The gradient multi-stage cooling process is a three-stage gradient multi-stage cooling process, defined as a first-stage cooling, a second-stage cooling, and a third-stage cooling. The first-stage cooling is at a rate of 10-15℃ / min to 600℃; the second-stage cooling is at a rate of 5-8℃ / min to 300℃; and the third-stage cooling is the final furnace cooling to room temperature.

6. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 1, characterized in that, In S4 above, the low-temperature stress-relieving tempering treatment includes: placing the cooled austenitic stainless steel straight wire into a tempering furnace, holding it at 200-250 ℃ for 40-60 min, and air-cooling it to room temperature after the holding period; argon gas is continuously introduced for protection during the tempering process.

7. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 1, characterized in that, In S1 above, the pretreatment includes ultrasonic cleaning and passivation treatment performed sequentially.

8. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 7, characterized in that, The ultrasonic cleaning uses a medical-grade alkaline cleaning agent with a pH of 8.5-9.5, an ultrasonic power of 300-400 W, and a cleaning time of 15-20 min; the passivation treatment uses a 5-8% nitric acid solution, soaks at room temperature for 20-30 s, then rinses with deionized water until neutral, and dries with nitrogen.

9. The heat treatment method for straight austenitic stainless steel wire for medical use according to claim 1, characterized in that, In S4 above, the post-processing includes surface finishing, and the surface finishing is performed by polishing the tempered wire with a centerless grinder. After polishing, the straightness of the wire is ≤0.5mm / m and the surface roughness Ra is ≤0.2μm.

10. A straight austenitic stainless steel wire for medical use, characterized in that, The medical austenitic stainless steel straight wire, prepared by the heat treatment method described in any one of claims 1-9, has a tensile strength ≥2600MPa and an elongation ≥2.0%.

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