Ion nitriding processing method for austenitic stainless steel medical suture needle

Abstract

The invention relates to the technical field of medical suture needle surface treatment, in particular to an austenitic stainless steel medical suture needle ion nitriding processing method, which comprises the following steps: placing a medical suture needle processed in S4 on a cathode plate of an ion nitriding furnace, covering a needle tip of the medical suture needle with an anode plate, the ion nitriding furnace sets the voltage of 550V and the air pressure of 300Pa for nitriding for 1 hour, the temperature is controlled between 350 DEG C and 430 DEG C according to the size of the medical suture needle, the process gas ratio is N2: H2 = 1: 9 or N2: H2 = 1: 3, and the surface hardness HV of the nitriding layer of the medical suture needle is 750-1200. The anode plate covers the needle point of the medical suture needle, and a plasma area is formed between the needle point of the medical suture needle and the anode plate, so that nitrogen ions bombard the surface of the needle point at a high speed under the action of an electric field to permeate, and the needle point part is rapidly nitrided to improve the hardness and puncture sharpness of the needle point; and the needle body and the needle tail have lower hardness and higher toughness.

Description

Technical Field

[0001] The present application relates to the field of surface treatment technology for medical suture needles, and in particular to a processing method for ion nitriding of austenitic stainless steel medical suture needles. Background Art

[0002] Medical stainless steel has become a widely used medical implant material and medical tool material in clinical practice due to its good biocompatibility, mechanical properties, resistance to body fluid corrosion, excellent processing and forming properties, and low cost. Among them, medical suture needles are very common and frequently used instruments in surgical operations. Medical suture needles are usually made of stainless steel by drilling or slotting the needle tail.

[0003] Stainless steel for medical suture needles mainly includes martensitic stainless steel and austenitic stainless steel. Austenitic stainless steel has an austenitic structure at room temperature. This type of structure and performance reacts little to temperature changes. It is non-magnetic, has excellent corrosion resistance, weldability, good toughness and biocompatibility. However, austenitic stainless steel cannot be strengthened by phase change, and the carbon content is less than 0.03%, and the solid solution strengthening effect is low. Therefore, the hardness (HV200~250) and strength (500~800MPa) of austenitic stainless steel in the solution treated state are low, which makes it difficult to meet the high strength, high hardness and high sharpness performance requirements of medical suture needles.

[0004] At present, the method to improve the hardness and sharpness of austenitic medical suture needles is mainly to harden the raw wire by cold drawing and large plastic deformation to increase the hardness to HV600 and the strength to 1500-1800MPa, which is beneficial to the high strength, high hardness and high sharpness required by medical suture needles; however, the excessive hardness of the medical suture needle (≥HV480) will cause difficulties in the subsequent mechanical processing of the medical suture needle, such as bending and needle hole processing, and the excessive hardness of the medical suture needle will cause its plasticity and toughness to decrease sharply, thereby increasing the tendency of the medical suture needle to brittle fracture. Summary of the invention

[0005] In order to improve the hardness and sharpness of medical suture needles, the present application provides a method for ion nitriding of austenitic stainless steel medical suture needles.

[0006] The present application provides a method for ion nitriding of austenitic stainless steel medical suture needles, which adopts the following technical solution: A method for ion nitriding of an austenitic stainless steel medical suture needle comprises the following steps: S1. Medical suture needle forming, austenitic stainless steel wire is first cold drawn to the required different diameter specifications and hardness of HV330-380, and then the austenitic stainless steel wire is formed into a medical suture needle through the processes of unwinding, straightening, cutting, needle hole processing and needle tip processing, and the medical suture needle is straight; S2. Needle tip fine-tuning: fine-tuning the needle tip of the medical suture needle processed in S1 to achieve a sharp needle tip without a false tip; S3. Polishing of medical suture needles, chemical or electrochemical surface polishing of the medical suture needles processed in S2; S4. Cleaning and drying of medical suture needles. The medical suture needles processed in S3 are cleaned and dried; S5. Ion nitriding of the needle tip. The medical suture needle processed in S4 is placed on the cathode plate of the ion nitriding furnace, and the anode plate is moved so that the anode plate covers the needle tip of the medical suture needle. The ion nitriding furnace is set to 550V and the air pressure is 300Pa for nitriding for 1 hour. The temperature is controlled between 350°C and 430°C according to the size of the medical suture needle. The process gas ratio is N2:H2=1:9 or N2:H2=1:3. After ion nitriding, the medical suture needle is taken out for air cooling, and the surface hardness of the nitrided layer of the medical suture needle is HV750~1200. S6. Cleaning and drying of medical suture needles. The medical suture needles processed in S5 are cleaned with water and then dried; S7. Bending the medical suture needle. The medical suture needle after S6 is bent as required to achieve the required 1 / 2 arc, 3 / 8 arc or 5 / 8 arc of the medical suture needle; S8. Cleaning and drying of medical suture needles: Clean the medical suture needles processed in S7 with water and then dry them.

[0007] By adopting the above technical scheme, firstly, the treatment temperature of the ion nitriding furnace in S5 is controlled between 350°C and 430°C according to the size of the medical suture needle, so as to avoid the hardness reduction caused by the processing strengthening effect of the austenitic stainless steel wire formed by cold drawing, and at the same time, the nitriding depth of the medical suture needle is controlled to avoid the complete nitriding of the needle tip of the medical suture needle. At the same time, the internal hardness of the medical suture needle after nitriding is maintained at HV330-380, which is conducive to maintaining the hardness, sharpness and toughness of the medical suture needle. After nitriding treatment, the hardness of the needle tip is increased from HV330-380 to above HV750, and even reaches HV1200. With the increase of the hardness of the needle tip of the medical suture needle, the required piercing force is also reduced. According to the provisions of the Medical Industry Standard of the People's Republic of China (YY / T 0043-2016), the required piercing force of a triangular suture needle with a diameter of 0.6 mm should be ≤0.58 N, while the medical suture needle of the same specification after ion nitriding only needs 0.18 N, which is far better than the industry standard; secondly, the core of the needle tip and the tail of the needle body still maintain a hardness of HV330-380 and high toughness, so that the tip of the medical suture needle can achieve high hardness and high sharpness, while the needle body and the needle tail of the medical suture needle maintain toughness and elasticity, thereby solving the contradiction between high hardness and high toughness of the medical suture needle; thirdly, the lower hardness and higher toughness of the needle body and the needle tail improve the machinability of the bending and needle hole forming of the austenitic stainless steel medical suture needle, and reduce the loss of processing equipment for high hardness austenitic stainless steel medical suture needles; finally, ion nitriding will mix a certain proportion of nitrogen into the stainless steel medical suture needle, forming a chromium nitride layer while preventing intergranular corrosion, and inhibiting excessive passivation and dissolution of elements such as chromium, making the stainless steel medical suture needle have stronger corrosion resistance.

[0008] Optionally, in step S5, the plate surface of the cathode plate facing the anode plate has a plurality of positioning holes for the medical suture needle tails to be embedded, the outer peripheral surface of the medical suture needle tails abuts against the inner wall of the positioning hole to form a limit, the inner wall of the positioning hole is flared in the direction close to the axis of the positioning hole, and the plate surface of the anode plate facing the cathode plate has a plurality of nitriding holes for the medical suture needle tips to be embedded, the inner wall of the nitriding hole is flared in the direction close to the axis of the nitriding hole, and the inner wall of the nitriding hole surrounds the outer peripheral surface of the needle tip.

[0009] By adopting the above technical solution, the tail of the medical suture needle is embedded in the positioning opening, and the outer peripheral surface of the medical suture needle abuts against the inner wall of the positioning hole to form a limit, so that the medical suture needle is positioned on the cathode plate. At the same time, the inner wall of the positioning hole is expanded in the direction close to the axis of the positioning hole, so that the cathode plate can meet the placement requirements of medical suture needles of different diameters. The anode plate is moved, and the needle tip of the medical suture needle is embedded in the nitriding hole. The inner wall of the nitriding hole surrounds the outer peripheral surface of the needle tip of the medical suture needle. When the nitriding furnace is running, a plasma zone is formed between the outer peripheral surface of the needle tip and the inner wall of the nitriding hole. The furnace body is used as the anode and the medical suture needle is used as the cathode. There is a DC voltage of hundreds of volts between the two. The hydrogen and nitrogen in the furnace body undergo glow discharge to form plasma. The nitrogen molecules are ionized under the bombardment of high-energy electrons to form nitrogen atoms and nitrogen ions. Under the action of the electric field, they move toward the tip of the medical suture needle at high speed and react chemically with the carbon atoms on the surface of the medical suture needle tip to form nitrides. These nitrides form a dense nitride layer on the surface of the medical suture needle tip, thereby improving the surface of the medical suture needle tip. In order to improve the hardness, wear resistance and corrosion resistance of the medical suture needle, during the plasma nitriding process, nitrogen ions and hydrogen ions bombard and sputter the surface of the medical suture needle tip at a high speed, which not only helps the diffusion and penetration of nitrogen atoms, but also removes impurities such as oil and oxides on the surface of the medical suture needle tip to achieve surface purification; at the same time, during the nitriding process, the medical suture needle tip will be bombarded by high-energy nitrogen ions, and these nitrogen ions are converted from kinetic energy to thermal energy, thereby heating the workpiece. This heating method is more uniform and efficient than traditional exogenous heating; in the process of bombarding the surface of the suture needle, cathode sputtering will also occur, and the sputtered iron ions will combine with nitrogen ions to form iron nitride. The compound will reattach to the surface of the workpiece and then decompose into Fe2N and Fe3N, and release nitrogen atoms to diffuse into the interior of the workpiece to achieve nitriding, which has higher efficiency and better treatment effect, and can not only significantly improve the surface hardness, wear resistance and fatigue resistance of austenitic stainless steel medical suture needles, but also keep the basic shape and size of the medical suture needles unchanged, thereby greatly extending their service life.

[0010] Optionally, the nitriding furnace treatment temperature in step S5 is set to 350°C, the process gas ratio is N2:H2=1:9, and the nitriding is taken out and air-cooled, so that the nitriding layer depth of the medical suture needle is 6±2μm and the surface hardness is HV780±30.

[0011] By adopting the above technical scheme, when the nitriding furnace treatment temperature is set to 350°C and the process gas ratio is N2:H2=1:9, the nitriding layer depth of the medical suture needle can be obtained to be 6±2μm, and the surface hardness is HV780±30, thereby improving the hardness and sharpness of the medical suture needle tip. At the same time, the needle body and needle tail of the medical suture needle still maintain a low hardness and high toughness, significantly improving the bending resistance of the medical suture needle body, reducing the problem of difficult processing of the needle hole of the medical suture needle, and reducing the requirements for processing equipment and the wear of processing molds.

[0012] Optionally, the nitriding furnace treatment temperature in step S5 is set to 370°C, the process gas ratio is N2:H2=1:9, and the nitriding is taken out and air-cooled, so that the nitriding layer depth of the medical suture needle is 9±2μm and the surface hardness is HV890±30.

[0013] By adopting the above technical solution, when the nitriding furnace treatment temperature is set to 370°C and the process gas ratio is N2:H2=1:9, the nitriding layer depth of the medical suture needle can be obtained to be 9±2μm and the surface hardness is HV890±30, thereby achieving precise processing of the medical suture needle.

[0014] Optionally, the nitriding furnace treatment temperature in step S5 is set to 400°C, the process gas ratio is N2:H2=1:9, and the medical suture needle is taken out for air cooling, so that the nitriding layer depth of the medical suture needle is 13±2μm and the surface hardness is HV1010±30.

[0015] By adopting the above technical solution, when the nitriding furnace treatment temperature is set to 400°C and the process gas ratio is N2:H2=1:9, the nitriding layer depth of the medical suture needle can be obtained to be 13±2μm and the surface hardness is HV1010±30, thereby achieving precise processing of the medical suture needle.

[0016] Optionally, the nitriding furnace treatment temperature in step S5 is set to 430°C, the process gas ratio is N2:H2=1:9, and the nitriding is taken out and air-cooled, so that the nitriding layer depth of the medical suture needle is 17±2μm and the surface hardness is HV1110±30.

[0017] By adopting the above technical solution, when the nitriding furnace treatment temperature is set to 430°C and the process gas ratio is N2:H2=1:9, the nitriding layer depth of the medical suture needle can be obtained to be 17±2μm and the surface hardness is HV1110±30, thereby achieving precise processing of the medical suture needle.

[0018] Optionally, the nitriding furnace treatment temperature in step S5 is set to 350°C, the process gas ratio is N2:H2=1:3, and the nitriding is taken out and air-cooled, so that the nitriding layer depth of the medical suture needle is 11±2μm and the surface hardness is HV830±30.

[0019] By adopting the above technical solution, when the nitriding furnace treatment temperature is set to 350°C and the process gas ratio is N2:H2=1:3, the nitriding layer depth of the medical suture needle can be obtained to be 11±2μm and the surface hardness is HV830±30, thereby achieving precise processing of the medical suture needle.

[0020] Optionally, the nitriding furnace treatment temperature in step S5 is set to 370°C, the process gas ratio is N2:H2=1:3, and the nitriding is taken out and air-cooled, so that the nitriding layer depth of the medical suture needle is 14±2μm and the surface hardness is HV950±30.

[0021] By adopting the above technical solution, when the nitriding furnace treatment temperature is set to 370°C and the process gas ratio is N2:H2=1:3, the nitriding layer depth of the medical suture needle can be obtained to be 14±2μm and the surface hardness is HV950±30, thereby achieving precise processing of the medical suture needle.

[0022] Optionally, the nitriding furnace treatment temperature in step S5 is set to 400°C, the process gas ratio is N2:H2=1:3, and the medical suture needle is taken out for air cooling, so that the nitriding layer depth of the medical suture needle is 19±2μm and the surface hardness is HV1080±30.

[0023] By adopting the above technical solution, when the nitriding furnace treatment temperature is set to 400°C and the process gas ratio is N2:H2=1:3, the nitriding layer depth of the medical suture needle can be obtained to be 19±2μm and the surface hardness is HV1080±30, thereby achieving precise processing of the medical suture needle.

[0024] Optionally, the nitriding furnace treatment temperature in step S5 is set to 430°C, the process gas ratio is N2:H2=1:3, and the nitriding is taken out and air-cooled, so that the nitriding layer depth of the medical suture needle is 23±2μm and the surface hardness is HV1190±30.

[0025] By adopting the above technical solution, when the nitriding furnace treatment temperature is set to 430°C and the process gas ratio is N2:H2=1:3, the nitriding layer depth of the medical suture needle can be obtained to be 23±2μm and the surface hardness is HV1190±30, thereby achieving precise processing of the medical suture needle.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: 1. The anode plate covers the tip of the medical suture needle, and a plasma zone is formed between the tip of the medical suture needle and the anode plate, so that nitrogen ions bombard the tip surface at high speed under the action of the electric field and penetrate into the tip, so as to achieve rapid nitriding of the tip to improve the hardness and puncture sharpness of the tip without reducing the lower hardness and higher toughness of the needle body and the needle tail; 2. The positioning holes and nitriding holes are set, and the direction of the positioning hole axis is expanded, so that the cathode plate can meet the placement requirements of medical suture needles of different diameters, significantly improve the surface hardness, wear resistance and fatigue resistance of austenitic stainless steel medical suture needles, and maintain the basic shape and size of the medical suture needles unchanged, thereby greatly extending their service life; 3. The nitriding furnace treatment temperature is set to 350°C and the process gas ratio is N2:H2=1:9, which improves the hardness and sharpness of the medical suture needle tip. At the same time, the medical suture needle body and needle tail still maintain a low hardness and high toughness, significantly improving the bending resistance of the medical suture needle body, reducing the problem of difficult processing of the medical suture needle hole, and reducing the requirements for processing equipment and the wear of processing molds. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure in Example 1 of the present application.

[0028] Figure 2 It is a partial cross-sectional view in Example 1 of the present application, mainly showing the positioning holes.

[0029] Figure 3 It is a partial cross-sectional view in Example 1 of the present application, mainly showing the nitriding holes.

[0030] Explanation of the reference numerals: 1. cathode plate; 11. positioning hole; 2. anode plate; 21. nitriding hole; 3. medical suture needle. DETAILED DESCRIPTION

[0031] The following is combined with Figure 1-3 This application is described in further detail.

[0032] The embodiment of the present application discloses a processing method for ion nitriding of an austenitic stainless steel medical suture needle. The present application is applicable to all austenitic stainless steels. The material of the austenitic stainless steel in the embodiment of the present application is 304 stainless steel. The hardness of the stainless steel can be divided into multiple levels according to its processing state and heat treatment process, such as soft state, 1 / 4 hard state, semi-hard state, 3 / 4 hard state and hard state, etc. The hardness of the raw steel wire of the austenitic stainless steel medical suture needle 3 in the embodiment of the present application is semi-hard (HV330~380), so that the medical suture needle 3 has good bending and needle hole machine processing properties.

[0033] Example 1 A processing method for ion nitriding of austenitic stainless steel medical suture needles comprises the following steps: S1. The medical suture needle 3 is formed. The austenitic stainless steel wire is first cold-drawn to different required diameters and hardnesses of HV330-380. In the embodiment of the present application, the austenitic stainless steel wire is cold-drawn to a hardness of HV360. The austenitic stainless steel wire is then formed into a medical suture needle 3 after sequentially undergoing unwinding, straightening, cutting, needle hole processing, and needle tip processing, and the medical suture needle 3 is straight; S2. Fine-tune the needle tip, fine-tune the needle tip of the medical suture needle 3 processed by S1, so that the needle tip is sharp and has no false tip; S3. Polishing of medical suture needle 3, chemical (ordinary pickling) or electrochemical surface polishing of S2; S4 medical suture needle 3 cleaning and drying, the S3 completed medical suture needle 3 cleaning and drying process; S5. Ion nitriding of the needle tip. The medical suture needle 3 processed in S4 is placed on the cathode plate 1 of the ion nitriding furnace, and the anode plate 2 is moved so that the anode plate 2 covers the needle tip of the medical suture needle 3. The parameters of the ion nitriding furnace are adjusted to a voltage of 550V, an air pressure of 300Pa, and an auxiliary temperature of 300°C for nitriding for 1 hour. The temperature is controlled between 350°C and 430°C according to the size of the medical suture needle 3. The process gas ratio is N2:H2=1:9 or N2:H2=1:3. After nitriding, the needle is taken out and air-cooled. The surface hardness of the medical suture needle 3 is HV750-1200. In the embodiment of the present application, the surface hardness of the medical suture needle 3 obtained when the processing temperature is 350°C and the process gas ratio is N2:H2=1:9 is tested to be HV780±30, and the depth of the nitriding layer of the medical suture needle 3 is 6±2μm. S6. Cleaning and drying of the medical suture needle 3. The medical suture needle 3 processed by S5 is cleaned with water and dried; S7. The medical suture needle 3 is bent, and the medical suture needle 3 after S6 is bent according to the needs to achieve the required 1 / 2 arc, 3 / 8 arc or 5 / 8 arc of the medical suture needle 3; S8. Cleaning and drying of the medical suture needle 3. The medical suture needle 3 processed by S7 is cleaned with water and dried; Reference Figure 1 and Figure 2 In step S5, the cathode plate 1 in the plate surface facing the anode plate 2 has a plurality of positioning holes 11 for the medical suture needle 3 to be embedded in the needle tail, and the inner wall of the positioning hole 11 abuts against the outer peripheral surface of the needle tail to form a limit, thereby realizing the positioning of the medical suture needle 3 on the cathode plate 1; at the same time, the inner wall of the positioning hole 11 is expanded in the direction close to the axis of the positioning hole 11, so that the cathode plate 1 can adapt to the limit of medical suture needles 3 of different diameters, thereby improving the versatility of use in the nitriding furnace.

[0034] Reference Figure 1 and Figure 3 In step S5, the plate surface of the anode plate 2 facing the cathode plate 1 has a plurality of nitriding holes 21 for the needle tips of the medical suture needles 3 to be embedded, the nitriding holes 21 correspond to the positioning holes 11 one by one, the inner wall of the nitriding hole 21 is expanded toward the direction close to the axis of the nitriding hole 21, and the inner wall of the nitriding hole 21 surrounds the outer peripheral surface of the needle tip. During the operation of the nitriding furnace, a plasma zone is formed between the outer peripheral surface of the needle tip and the inner wall of the nitriding hole 21, and nitrogen ions bombard the surface of the needle tip at a high speed under the action of the electric field, thereby achieving the purpose of local nitriding of the needle tip of the medical suture needle 3.

[0035] The implementation principle of the ion nitriding processing method of an austenitic stainless steel medical suture needle in Example 1 of the present application is as follows: the austenitic stainless steel suture needle is divided into three parts: a needle tip, a needle body and a needle tail, and the needle tip part of the medical suture needle 3 is nitrided by utilizing the characteristic that ion nitriding can perform local nitriding, thereby achieving the goal of improving the hardness of the needle tip while maintaining the elasticity and toughness of the needle body and the needle tail, thereby improving the machinability of the austenitic stainless steel medical suture needle 3 in bending and needle hole forming, and reducing the wear of the high-hardness austenitic stainless steel medical suture needle 3 on the processing equipment.

[0036] Example 2 The difference between Example 2 and Example 1 is that the processing temperature of the ion nitriding furnace in S5 is set to 370°C, the process gas ratio is N2:H2=1:9, and the medical suture needle 3 is taken out for air cooling after nitriding. The depth of the nitriding layer of the medical suture needle 3 is detected to be 9±2μm, and the surface hardness is HV890±30.

[0037] The implementation principle of the ion nitriding processing method for an austenitic stainless steel medical suture needle in Example 2 of the present application is as follows: by setting the nitriding furnace treatment temperature to 370°C and the process gas ratio to N2:H2=1:9, the nitriding layer depth of the medical suture needle 3 can be obtained to be 9±2μm, and the surface hardness is HV890±30, so that the medical suture needle 3 can be precisely processed according to actual usage requirements.

[0038] Example 3 The difference between Example 3 and Example 1 is that the processing temperature of the ion nitriding furnace in S5 is set to 400°C, the process gas ratio is N2:H2=1:9, and it is taken out for air cooling after nitriding. The depth of the nitriding layer of the medical suture needle 3 is detected to be 13±2μm, and the surface hardness is HV1010±30.

[0039] The implementation principle of the ion nitriding processing method for an austenitic stainless steel medical suture needle in Example 3 of the present application is as follows: by setting the nitriding furnace treatment temperature to 400°C and the process gas ratio to N2:H2=1:9, the nitriding layer depth of the medical suture needle 3 can be obtained to be 13±2μm, and the surface hardness is HV1010±30, so that the medical suture needle 3 can be precisely processed according to actual usage requirements.

[0040] Example 4 The difference between Example 4 and Example 1 is that the processing temperature of the ion nitriding furnace in S5 is set to 430°C, the process gas ratio is N2:H2=1:9, and it is taken out for air cooling after nitriding. The depth of the nitriding layer of the medical suture needle 3 is detected to be 17±2μm, and the surface hardness is HV1110±30.

[0041] The implementation principle of the ion nitriding processing method for an austenitic stainless steel medical suture needle in Example 4 of the present application is as follows: by setting the nitriding furnace treatment temperature to 430°C and the process gas ratio to N2:H2=1:9, the nitriding layer depth of the medical suture needle 3 can be obtained to be 17±2μm, and the surface hardness is HV1110±30, so that the medical suture needle 3 can be precisely processed according to actual usage requirements.

[0042] Example 5 The difference between Example 5 and Example 1 is that the processing temperature of the ion nitriding furnace in S5 is set to 350°C, the process gas ratio is N2:H2=1:3, and it is taken out for air cooling after nitriding. The depth of the nitriding layer of the medical suture needle 3 is detected to be 11±2μm, and the surface hardness is HV830±30.

[0043] The implementation principle of the ion nitriding processing method for an austenitic stainless steel medical suture needle in Example 5 of the present application is as follows: by setting the nitriding furnace treatment temperature to 350°C and the process gas ratio to N2:H2=1:3, the nitriding layer depth of the medical suture needle 3 can be obtained to be 11±2μm, and the surface hardness is HV830±30, so that the medical suture needle 3 can be precisely processed according to actual usage requirements.

[0044] Example 6 The difference between Example 6 and Example 1 is that the processing temperature of the ion nitriding furnace in S5 is set to 370°C, the process gas ratio is N2:H2=1:3, and it is taken out for air cooling after nitriding. The depth of the nitriding layer of the medical suture needle 3 is detected to be 14±2μm, and the surface hardness is HV950±30.

[0045] The implementation principle of the ion nitriding processing method for an austenitic stainless steel medical suture needle in Example 6 of the present application is as follows: by setting the nitriding furnace treatment temperature to 370°C and the process gas ratio to N2:H2=1:3, the nitriding layer depth of the medical suture needle 3 can be obtained to be 14±2μm, and the surface hardness can be HV950±30, so that the medical suture needle 3 can be precisely processed according to actual usage requirements.

[0046] Example 7 The difference between Example 7 and Example 1 is that the processing temperature of the ion nitriding furnace in S5 is set to 400°C, the process gas ratio is N2:H2=1:3, and it is taken out for air cooling after nitriding. The depth of the nitriding layer of the medical suture needle 3 is detected to be 19±2μm, and the surface hardness is HV1080±30.

[0047] The implementation principle of the ion nitriding processing method for an austenitic stainless steel medical suture needle in Example 7 of the present application is as follows: by setting the nitriding furnace treatment temperature to 400°C and the process gas ratio to N2:H2=1:3, the nitriding layer depth of the medical suture needle 3 can be obtained to be 19±2μm, and the surface hardness can be HV1080±30, so that the medical suture needle 3 can be precisely processed according to actual usage requirements.

[0048] Example 8 The difference between Example 8 and Example 1 is that the processing temperature of the ion nitriding furnace in S5 is set to 430°C, the process gas ratio is N2:H2=1:3, and it is taken out for air cooling after nitriding. The depth of the nitriding layer of the medical suture needle 3 is detected to be 23±2μm, and the surface hardness is HV1190±30.

[0049] The implementation principle of the ion nitriding processing method for an austenitic stainless steel medical suture needle in Example 8 of the present application is as follows: by setting the nitriding furnace treatment temperature to 430°C and the process gas ratio to N2:H2=1:3, the nitriding layer depth of the medical suture needle 3 can be obtained to be 23±2μm, and the surface hardness is HV1190±30, so that the medical suture needle 3 can be precisely processed according to actual usage requirements.

[0050] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for ion nitriding of austenitic stainless steel medical suture needles, characterized in that: The following steps are involved: S1. The medical suture needle (3) is formed by cold drawing the austenitic stainless steel wire to the required different diameter specifications and the hardness of HV330 to 380, and then the austenitic stainless steel wire is formed into the medical suture needle (3) by the processes of unwinding, straightening, cutting, needle hole processing and needle tip processing, and the medical suture needle (3) is straight; S2. Needle tip fine-tuning, the medical suture needle (3) processed by S1 is fine-tuned to achieve a sharp needle tip without a false tip; S3 medical suture needle (3) polishing, the S2 processed medical suture needle (3) is subjected to chemical or electrochemical surface polishing; S4 medical suture needle (3) cleaning and drying, the S3 processed medical suture needle (3) after cleaning and drying; S5. Ion nitriding of the needle tip, placing the medical suture needle (3) processed in S4 on the cathode plate (1) of the ion nitriding furnace, and moving the anode plate (2), so that the anode plate (2) covers the needle tip of the medical suture needle (3), nitriding for 1 hour at a voltage of 550V and an air pressure of 300Pa in the ion nitriding furnace, controlling the temperature between 350°C and 430°C according to the size of the medical suture needle (3), using a process gas ratio of N2:H2=1:9 or N2:H2=1:3, and taking out the ion nitriding and air cooling, and obtaining a surface hardness of the nitrided layer of the medical suture needle (3) of HV750-1200; S6 medical suture needle (3) cleaning and drying, the S5 processed medical suture needle (3) is washed with water and then dried; S7. The medical suture needle (3) is bent. The medical suture needle (3) after S6 is bent as required to achieve the desired 1 / 2 arc, 3 / 8 arc or 5 / 8 arc of the medical suture needle (3); S8. Cleaning and drying the medical suture needle (3). The medical suture needle (3) processed in S7 is cleaned with water and then dried.

2. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 1, characterized in that: In step S5, the plate surface of the cathode plate (1) facing the anode plate (2) has a plurality of positioning holes (11) for inserting the tail of the medical suture needle (3), the outer peripheral surface of the tail of the medical suture needle (3) abuts against the inner wall of the positioning hole (11) to form a limit, and the inner wall of the positioning hole (11) is expanded in the direction close to the axis of the positioning hole (11), and the plate surface of the anode plate (2) facing the cathode plate (1) has a plurality of nitriding holes (21) for inserting the needle tip of the medical suture needle (3), the inner wall of the nitriding hole (21) is expanded in the direction close to the axis of the nitriding hole (21), and the inner wall of the nitriding hole (21) surrounds the outer peripheral surface of the needle tip.

3. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 350°C, the process gas ratio is N2:H2=1:9, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 6±2μm and the surface hardness is HV780±30.

4. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 370°C, the process gas ratio is N2:H2=1:9, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 9±2μm and the surface hardness is HV890±30.

5. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 400°C, the process gas ratio is N2:H2=1:9, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 13±2μm and the surface hardness is HV1010±30.

6. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 430°C, the process gas ratio is N2:H2=1:9, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 17±2μm and the surface hardness is HV1110±30.

7. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 350°C, the process gas ratio is N2:H2=1:3, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 11±2μm and the surface hardness is HV830±30.

8. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 370°C, the process gas ratio is N2:H2=1:3, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 14±2μm and the surface hardness is HV950±30.

9. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 400°C, the process gas ratio is N2:H2=1:3, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 19±2μm and the surface hardness is HV1080±30.

10. The method for ion nitriding of austenitic stainless steel medical suture needles according to claim 2, characterized in that: The nitriding furnace treatment temperature in step S5 is set to 430°C, the process gas ratio is N2:H2=1:3, and the needle is taken out for air cooling after nitriding, so that the nitriding layer depth of the medical suture needle (3) is 23±2μm and the surface hardness is HV1190±30.

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