High-nitrogen austenitic stainless steel, preparation process thereof and wearable equipment

Abstract

The invention provides high-nitrogen austenitic stainless steel, a preparation process thereof and wearable equipment, and the preparation process comprises the following steps: S10, obtaining a high-purity metal raw material according to the composition proportion of the high-nitrogen austenitic stainless steel, and then sequentially carrying out vacuum ball milling and solid nitriding treatment to obtain mixed metal powder; s20, the mixed metal powder is sintered and formed, and a metal plate is obtained through continuous rolling; and S30, the metal plate is subjected to solution treatment, and the completely recrystallized high-nitrogen austenitic stainless steel of the single austenite structure is obtained. Wherein the high-nitrogen austenitic stainless steel comprises the following elements in percentage by mass: 0.75 to 1.0 percent of N, 17.5 to 19.0 percent of Cr, 16.0 to 18.5 percent of Mn, 2.5 to 4.0 percent of Mo, not more than 0.5 percent of Ni, not more than 0.5 percent of Si and not more than 0.08 percent of C; and the balance of Fe. The austenitic stainless steel with the high nitrogen content is obtained through powder solid nitriding treatment and sintering, the high-performance stainless steel is obtained through nitrogen element strengthening, and the performance in the aspects of obdurability, corrosion resistance, abrasion resistance, good biocompatibility and the like is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of stainless steel, and in particular to a high-nitrogen austenitic stainless steel and a preparation process and wearable equipment thereof. Background Art

[0002] With the intelligentization and popularization of wearable devices, stainless steel has gradually become the core material of high-end electronic equipment, medical equipment and sports equipment due to its high strength, corrosion resistance, excellent processing performance and aesthetic value. For example, austenitic stainless steel is widely used in smart watches, health monitoring equipment and other fields due to its low magnetic properties.

[0003] Due to the limitations of application scenarios, when stainless steel is used in wearable devices, new requirements are also put forward for stainless steel plates. For example, it needs to be as lightweight as possible to reduce the burden on the human body; it also needs to be non-magnetic to avoid interference of magnetic fields on sensors; in addition, since wearable devices may come into contact with sweat and body fluids, there are certain requirements for corrosion resistance.

[0004] Therefore, the present application proposes a preparation process of high nitrogen austenitic stainless steel, and nitriding and strengthening are used to obtain high performance stainless steel. Summary of the invention

[0005] In response to at least one of the above problems, the present invention provides a preparation process of high nitrogen austenitic stainless steel, comprising the following steps: S10: obtaining a high-purity metal raw material according to the composition ratio of the high nitrogen austenitic stainless steel, and then performing vacuum ball milling and solid-state nitriding treatment in sequence to obtain a mixed metal powder; S20: sintering the mixed metal powder into a shape, and continuously rolling to obtain a metal plate; S30: performing solid solution treatment on the metal plate to obtain a high nitrogen austenitic stainless steel with a fully recrystallized single austenite structure; wherein the high nitrogen austenitic stainless steel includes the following elements in terms of mass percentage: N 0.75-1.0%, Cr 17.5-19.0%, Mn16.0-18.5%, Mo 2.5-4.0%, Ni not more than 0.5%, Si not more than 0.5%, C not more than 0.08%; the balance is Fe.

[0006] Furthermore, the solid nitriding treatment is a nitriding treatment for 2-20 hours at a controlled temperature of 400-600° C. in a nitriding atmosphere; wherein the nitriding atmosphere is a mixed gas of ammonia and nitrogen, and the volume proportion of nitrogen in the mixed gas is 75-90%.

[0007] Furthermore, the sintering molding is to press the mixed metal powder into a shape, and then control the sintering temperature to 1200-1450°C in the sintering atmosphere for staged sintering; the staged sintering includes: controlling the pressure not to exceed 3MPa for the first stage sintering, and when the density is greater than 90%, controlling the pressure to 5-12MPa for the second stage sintering, and when the density is greater than 99%, quickly cooling to room temperature at a rate of 30-40°C / min.

[0008] Furthermore, the sintering atmosphere is argon or a mixture of argon and nitrogen.

[0009] Furthermore, the continuous rolling is to perform multiple passes of continuous rolling on the sintered material to obtain a metal sheet with a thickness of 1-5 mm.

[0010] Furthermore, the solution treatment is carried out at a temperature of 1050-1100° C. for 2-4 hours, and then the temperature is rapidly cooled to room temperature at a rate of 30-40° C. / min.

[0011] Furthermore, the high nitrogen austenitic stainless steel is subjected to surface strengthening treatment; the surface strengthening treatment includes passivation treatment.

[0012] The present invention also provides a high-nitrogen austenitic stainless steel, which is prepared by adopting the above preparation process.

[0013] The present invention also provides a wearable device, which is prepared using the above-mentioned austenitic stainless steel. DETAILED DESCRIPTION

[0014] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] The invention provides a preparation process of high nitrogen austenitic stainless steel, comprising the following steps: S10: obtaining a high-purity metal raw material according to the composition ratio of the high nitrogen austenitic stainless steel, and then sequentially performing vacuum ball milling and solid-state nitriding treatment to obtain a mixed metal powder; S20: sintering the mixed metal powder into a shape, and continuously rolling to obtain a metal plate; S30: performing a solid solution treatment on the metal plate to obtain the high nitrogen austenitic stainless steel with a fully recrystallized single austenite structure; wherein the high nitrogen austenitic stainless steel comprises the following elements in terms of mass percentage: N 0.75-1.0%, Cr 17.5-19.0%, Mn 16.0-18.5%, Mo 2.5-4.0%, Ni not more than 0.5%, Si not more than 0.5%, C not more than 0.08%; the remainder is Fe.

[0016] High nitrogen austenitic stainless steel is a special stainless steel with excellent performance, with many advantages, such as high strength, high toughness, corrosion resistance, good wear resistance, non-ferromagnetic and good biocompatibility, nitrogen can effectively enhance the mechanical properties of stainless steel, including its strength and toughness, while the addition of nitrogen helps to refine the grains, thereby improving the tensile strength and fatigue strength of stainless steel. The solid solution strengthening effect of nitrogen is the key to improving the performance of stainless steel. Nitrogen can change the crystal structure in austenite and increase its hardness and strength. Nitrogen also has a strong austenite stabilization effect, and the stabilization ability of nitrogen to austenite is 18 times that of nickel. Therefore, the stainless steel provided by the present invention reduces the nickel content (no more than 0.5%) in the composition design and increases the nitrogen content (0.75-1.0%). In addition, Cr has a solid solution strengthening effect, which can enhance the mechanical properties of steel, especially the stability at high temperatures, and prevent intergranular corrosion, and its mass ratio is preferably 17.5-19.0%. Mn can improve the plasticity and forgeability of steel, help steel maintain good deformation performance during processing, and have a certain enhancement effect on wear resistance and impact resistance. Its mass proportion is preferably 16.0-18.5%. Mo is an important element to prevent stress corrosion cracking and pitting corrosion caused by chlorides. It can enhance the corrosion resistance of steel in acidic and chloride environments. Its mass proportion is preferably 2.5-4.0%. Si plays a deoxidation role in the steel smelting process, reduces the impact of oxygen on steel, and improves the purity of steel. A moderate amount of silicon can increase the strength of steel, but too much silicon will make steel brittle, so its mass proportion does not exceed 0.5%.

[0017] In the preparation method of high nitrogen austenitic stainless steel, the traditional melting and casting method is prone to the following problems: under normal pressure, the solubility of nitrogen in molten steel is low, which makes it difficult to achieve the required high nitrogen content. This requires the application of high nitrogen partial pressure to ensure that nitrogen is fully dissolved in the molten steel. During the solidification process, the molten steel will experience the δ-Fe phase region with lower nitrogen solubility. At this time, the solubility of nitrogen is greatly reduced, resulting in nitrogen escape, and the nitrogen content cannot be maintained within the target range, thereby affecting the quality of the steel. Due to the escape of nitrogen, pores may appear during the solidification process, affecting the density and mechanical properties of the material. Therefore, the embodiment of the invention adopts a powder metallurgy method, firstly, the weight and mixing are carried out according to the pre-designed alloy composition; then a high-energy ball mill is used for ball milling treatment, and the powder is refined and the particles are deformed by collision, extrusion and friction between high-speed rotating grinding balls and powders. In the high-energy ball mill, the metal powder and the grinding balls are constantly collided and impacted, and cold welding occurs in this process, that is, the metal particles contact and fuse under high-energy collision to form larger particles. At the same time, the powder will also be broken to form smaller particles. These microstructural changes help to increase the specific surface area of ​​the metal powder, which is beneficial for the subsequent nitriding treatment.

[0018] Specifically, further, the solid-state nitriding treatment is a nitriding treatment for 2-20 hours at a controlled temperature of 400-600° C. in a nitriding atmosphere; wherein the nitriding atmosphere is a mixed gas of ammonia and nitrogen, and in the mixed gas, the volume proportion of nitrogen is 75-90%.

[0019] This embodiment adopts solid powder nitriding method, the key advantage of which is that the solubility of nitrogen in the solid austenite phase is greater than that in molten steel. This makes the nitriding process more efficient and can effectively increase the nitrogen content of the powder. At the same time, the powder maintains good particle morphology and uniformity during the nitriding process. Preferably, a fluidized bed nitriding method is adopted, using a fluidized bed device, and the solid powder is suspended in a nitriding atmosphere, thereby increasing the gas-solid phase contact area and promoting gas-solid reaction.

[0020] Furthermore, the sintering molding is to press the mixed metal powder into a mold, and then control the sintering temperature to 1200-1450°C in the sintering atmosphere for staged sintering; the staged sintering includes: controlling the pressure not to exceed 3MPa for one-stage sintering, and when the density is greater than 90%, controlling the pressure to 5-12MPa for two-stage sintering, and when the density is greater than 99%, quickly cooling to room temperature at a rate of 30-40°C / min.

[0021] Furthermore, the sintering atmosphere is argon or a mixture of argon and nitrogen.

[0022] In this embodiment, the metal powder is gradually combined during the sintering process by applying pressure in stages to improve the density, and the single-phase austenite structure is maintained by rapidly cooling the temperature.

[0023] Furthermore, the continuous rolling is to perform multiple passes of continuous rolling on the material obtained by sintering to obtain the metal sheet with a thickness of 1-5 mm.

[0024] Furthermore, the solution treatment is to keep the temperature at 1050-1100°C for 2-4 hours, and then quickly cool down to room temperature at a rate of 30-40°C / min. The solution treatment effectively improves the corrosion resistance and intergranular corrosion resistance of austenitic stainless steel by dissolving the carbides of alloy elements at high temperature and maintaining the single-phase austenite structure by rapid cooling.

[0025] Furthermore, the high nitrogen austenitic stainless steel is subjected to surface strengthening treatment; the surface strengthening treatment includes passivation treatment.

[0026] The present invention also provides a high-nitrogen austenitic stainless steel, which is prepared by adopting the above preparation process.

[0027] The present invention also provides a wearable device, which is prepared using the above-mentioned austenitic stainless steel.

[0028] The wearable device provided by the present invention uses austenitic stainless steel as a substrate, and the austenitic stainless steel can be processed differently according to the specific requirements of the wearable device.

[0029] For example, the austenitic stainless steel sheet is subjected to cold rolling, annealing and aging treatment to obtain a stainless steel sheet of a specified thickness. Specifically, the following steps are included:

[0030] A: obtaining an austenitic stainless steel substrate and pre-treating it to obtain a first steel plate;

[0031] B: The first steel plate is subjected to cold rolling, annealing and aging treatment to obtain the second steel plate.

[0032] Pretreatment includes mechanical cleaning and ultrasonic cleaning; mechanical cleaning includes: shot peening and polishing in sequence to remove oxides on the surface of the stainless steel substrate; ultrasonic cleaning includes: using acetone as the cleaning liquid, setting the ultrasonic frequency to 25-40kHz, and the ultrasonic power to 100-400W for 5-20 minutes. The combined pretreatment technology of shot peening and polishing + ultrasonic cleaning is used to clean the surface of the stainless steel substrate, which is beneficial to the subsequent rolling process.

[0033] Furthermore, the cold rolling process is performed for no less than 10 passes, the reduction rate of each pass is less than the reduction rate of the previous pass, and the total cold rolling reduction rate does not exceed 80%. Annealing is performed after every 2 rolling passes; the annealing process includes: -3 In a Pa environment, the temperature is raised to 950-980℃ at a heating rate of 5-8℃ / s and kept warm, and then cooled to room temperature with the furnace; the holding time of the annealing treatment is determined according to the thickness of the first steel plate, and the holding time is 2-3 minutes per millimeter. The aging treatment includes: after the last annealing treatment is finished, the temperature is lowered to 450-500℃ at a cooling rate of 20-50℃ / s for aging treatment for 1-3 hours.

[0034] In this embodiment, microstructure control is achieved by matching the parameters of cold rolling-annealing-aging. The precision cold rolling process reduces deformation energy storage and inhibits the occurrence of dynamic recrystallization through small reduction and gradient rolling. The vacuum annealing process can promote the complete recrystallization of austenite to a face-centered cubic structure at high temperature and eliminate the work hardening layer; the vacuum environment prevents oxidation, ensures uniform grain growth, and reduces the pinning sites of the magnetic domain wall. After annealing, the temperature is quickly cooled to the aging temperature to avoid phase change hysteresis and achieve a balance between strength and toughness. The aging stage further improves the strength and hardness of the material through rapid cooling and appropriate heat preservation, optimizes the microstructure of stainless steel, and reduces the coercivity.

[0035] Cold rolling treatment uses a multi-pass cold rolling technology with a decreasing reduction rate to achieve uniform deformation through a gradient change in the reduction rate (previous pass> subsequent pass) to avoid edge thinning. At the same time, the cumulative reduction rate does not exceed 80%. Combined with the subsequent annealing process, the grain orientation consistency is improved and the internal stress of the material is reduced. At the same time, the flatness of the stainless steel plate can be improved through gradient cold rolling.

[0036] In addition, due to the functional requirements of wearable devices, stainless steel plates are easily exposed to sweat and body fluids. Therefore, when corrosive ions are present, they react chemically with certain components in the stainless steel plate, which is prone to chemical corrosion and rust. In addition, the stainless steel plates in wearable devices are also prone to bumps and scratches due to human body movements. Therefore, the surface of the second steel plate can be further subjected to composite surface treatment, which specifically includes the following steps:

[0037] C: Electroplated nickel layer on the surface of the second steel plate;

[0038] D: Nano-modification using laser femtosecond technology;

[0039] E: A non-magnetic stainless steel plate is obtained by passivation with citric acid; the surface of the non-magnetic stainless steel plate comprises a three-phase composite coating of a nickel layer, a nano-modified structure and a passivation layer.

[0040] Of course, the most preferred method is to comprehensively improve the performance of the stainless steel plate through the three-phase composite of nickel plating layer-nano modification-passivation layer. Technical personnel in this field can also choose to perform only nickel plating treatment or only passivation treatment, or a composite treatment of the two according to actual needs.

[0041] In a specific embodiment, the thickness of the nickel layer is 5-10% of the thickness of the second steel plate; the thickness of the passivation layer is 1.5-3 times the thickness of the nickel layer. The thicker the passivation layer is, the more it can resist some mechanical impacts. Even if the passivation layer is damaged by scratches, the stainless steel is not easily corroded due to the design of the nickel-plated layer.

[0042] Further, step C includes: electroplating with a mixture of nickel sulfate and ammonium chloride as the electroplating solution, wherein the concentration of nickel ions in the electroplating solution is 200-400 g / L. The current density of the electroplating is set at 2-10 A / dm 2 Within the range, the electroplating time is 10-30 minutes and the temperature is controlled between 50-60℃.

[0043] Furthermore, two different femtosecond lasers are used for nano-modification. Specifically, step D includes: setting the laser wavelength to 800 nm, the pulse width to 50-60 fs, and the pulse energy density to 50-100 J / cm 2, spot diameter 6-12μm; perform a laser femtosecond treatment to obtain a nanowire modified structure; set the laser wavelength to 1030nm, the pulse width to 50-60fs, and the pulse energy density to 50-100J / cm 2 , spot diameter 15-18μm; secondary laser femtosecond treatment is performed to obtain a nanopore-modified structure.

[0044] The nanowire and nanopore structures generated by laser femtosecond technology can significantly increase the surface area of ​​the material, thereby forming a more uniformly mixed passivation layer during passivation treatment; and increasing the adhesion between the passivation layer and the nickel layer. Furthermore, step D is carried out in a nitrogen atmosphere. Nitrogen is deposited on the surface of the nickel layer under the action of laser femtosecond and forms a stable Ni 4 N is dispersed in the nanowire and nanopore structures, thereby improving the hardness of the entire coating.

[0045] Furthermore, step E includes: preparing two passivation solutions of different concentrations, wherein the mass of citric acid in the low-concentration passivation solution accounts for 10-15%; the mass of citric acid in the high-concentration passivation solution accounts for 20-25%; spraying the low-concentration passivation solution on the surface of the second steel plate, and keeping it warm at 40-50°C for 10-20 minutes; and then immersing the second steel plate in the high-concentration passivation solution at 50-60°C for 20-30 minutes.

[0046] Preferably, after the composite surface treatment is completed, annealing treatment is performed, including: in a vacuum degree of ≤1×10 -3 In the Pa environment, the temperature was raised to 950-980°C at a heating rate of 5-8°C / s and kept warm, and then cooled to room temperature with the furnace.

[0047] Example 1

[0048] This embodiment provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0049] S10: obtaining high-purity metal raw materials according to the composition ratio of high-nitrogen austenitic stainless steel, and then sequentially performing vacuum ball milling and solid-state nitriding treatment to obtain mixed metal powder; the solid-state nitriding treatment is to perform nitriding treatment for 12 hours at a controlled temperature of 500° C. under a nitriding atmosphere; wherein the nitriding atmosphere is a mixed gas of ammonia and nitrogen, and the volume proportion of nitrogen in the mixed gas is 80%.

[0050] S20: Sintering the mixed metal powder into a shape and continuously rolling the mixed metal powder into a metal sheet.

[0051] Among them, sintering molding is to press the mixed metal powder into a mold, and then control the sintering temperature to 1300℃ in the sintering atmosphere for staged sintering; staged sintering includes: controlling the pressure not to exceed 3MPa for stage one sintering, and when the density is greater than 90%, controlling the pressure to 8MPa for stage two sintering, and when the density is greater than 99%, quickly cooling to room temperature at a rate of 35℃ / min. The sintering atmosphere is argon or a mixture of argon and nitrogen.

[0052] The continuous rolling is to perform multiple continuous rolling on the sintered material to obtain a metal sheet with a thickness of 2 mm.

[0053] S30: The metal plate is kept at 1050°C for 3h, and then rapidly cooled to room temperature at a rate of 35°C / min to obtain a high nitrogen austenitic stainless steel with a completely recrystallized single austenite structure; the test results show that the high nitrogen austenitic stainless steel includes the following elements in terms of mass percentage: N 0.86%, Cr 18.23%, Mn 17.58%, Mo 3.66%, Ni not more than 0.5%, Si not more than 0.5%, C not more than 0.08%; the balance is Fe.

[0054] Example 2

[0055] This embodiment provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0056] S10: obtaining high-purity metal raw materials according to the composition ratio of high-nitrogen austenitic stainless steel, and then sequentially performing vacuum ball milling and solid-state nitriding treatment to obtain mixed metal powder; the solid-state nitriding treatment is to perform nitriding treatment for 20 hours at a controlled temperature of 400° C. under a nitriding atmosphere; wherein the nitriding atmosphere is a mixed gas of ammonia and nitrogen, and the volume proportion of nitrogen in the mixed gas is 75%.

[0057] S20: Sintering the mixed metal powder into a shape and continuously rolling the mixed metal powder into a metal sheet.

[0058] Among them, sintering molding is to press the mixed metal powder into a mold, and then control the sintering temperature to 1200℃ in the sintering atmosphere for staged sintering; staged sintering includes: controlling the pressure not to exceed 3MPa for stage one sintering, and when the density is greater than 90%, controlling the pressure to 5MPa for stage two sintering, and when the density is greater than 99%, rapidly cooling to room temperature at a rate of 30℃ / min. The sintering atmosphere is argon or a mixture of argon and nitrogen.

[0059] The continuous rolling is to perform multiple continuous rolling on the sintered material to obtain a metal sheet with a thickness of 1 mm.

[0060] S30: The metal plate is kept at 1050°C for 2h, and then rapidly cooled to room temperature at a rate of 30°C / min to obtain a high nitrogen austenitic stainless steel with a completely recrystallized single austenite structure; the test results show that the high nitrogen austenitic stainless steel includes the following elements in terms of mass percentage: N 0.78%, Cr 18.69%, Mn 16.03%, Mo 3.91%, Ni not more than 0.5%, Si not more than 0.5%, C not more than 0.08%; the balance is Fe.

[0061] Example 3

[0062] This embodiment provides a method for preparing high nitrogen austenitic stainless steel, comprising the following steps:

[0063] S10: obtaining high-purity metal raw materials according to the composition ratio of high-nitrogen austenitic stainless steel, and then sequentially performing vacuum ball milling and solid-state nitriding treatment to obtain mixed metal powder; the solid-state nitriding treatment is to control the temperature to 600° C. for nitriding treatment for 20 hours under a nitriding atmosphere; wherein the nitriding atmosphere is a mixed gas of ammonia and nitrogen, and the volume proportion of nitrogen in the mixed gas is 90%.

[0064] S20: Sintering the mixed metal powder into a shape and continuously rolling the mixed metal powder into a metal sheet.

[0065] Among them, sintering molding is to press the mixed metal powder into a mold, and then control the sintering temperature to 1450℃ in the sintering atmosphere for staged sintering; staged sintering includes: controlling the pressure not to exceed 3MPa for stage one sintering, and when the density is greater than 90%, controlling the pressure to 12MPa for stage two sintering, and when the density is greater than 99%, quickly cooling to room temperature at a rate of 40℃ / min. The sintering atmosphere is argon or a mixture of argon and nitrogen.

[0066] The continuous rolling is to perform multiple continuous rolling on the sintered material to obtain a metal sheet with a thickness of 5 mm.

[0067] S30: The metal plate is kept at 1100°C for 2h, and then quickly cooled to room temperature at a rate of 40°C / min to obtain a high nitrogen austenitic stainless steel with a completely recrystallized single austenite structure; the test results show that the high nitrogen austenitic stainless steel includes the following elements in terms of mass percentage: N 0.97%, Cr 17.53%, Mn 18.42%, Mo 2.55%, Ni not more than 0.5%, Si not more than 0.5%, C not more than 0.08%; the balance is Fe.

[0068] Example 4

[0069] This embodiment provides a stainless steel plate for a wearable device, using the stainless steel prepared in Example 1 as a substrate and performing the following treatments:

[0070] A: An austenitic stainless steel substrate is obtained, and shot peening and polishing are performed in sequence to remove oxides on the surface of the stainless steel substrate; acetone is used as a cleaning liquid, and the ultrasonic frequency is set to 25 kHz and the ultrasonic power is set to 100 W for cleaning for 5 minutes to obtain a first steel plate.

[0071] B: The first steel plate is subjected to cold rolling; the number of cold rolling passes is not less than 10, the reduction rate of each pass is less than the reduction rate of the previous pass, and the total cold rolling reduction rate does not exceed 80%.

[0072] Annealing treatment is carried out after every 2 rolling passes; annealing treatment includes: -3 In the Pa environment, the temperature is raised to 950°C at a heating rate of 5°C / s and maintained, and then cooled to room temperature with the furnace; wherein, the holding time of the annealing treatment is determined according to the thickness of the first steel plate, and is held for 2 minutes per millimeter.

[0073] After the last annealing treatment was completed, the temperature was lowered to 450° C. at a cooling rate of 20° C. / s and then subjected to aging treatment for 1 hour to obtain a second steel plate.

[0074] This embodiment also provides a wearable device, which adopts the above-mentioned second steel plate.

[0075] Example 5

[0076] This embodiment provides a stainless steel plate for a wearable device, using the stainless steel prepared in Example 1 as a substrate and performing the following treatments:

[0077] A: An austenitic stainless steel substrate is subjected to shot peening and polishing treatments in sequence to remove oxides on the surface of the stainless steel substrate; acetone is used as a cleaning liquid, the ultrasonic frequency is set to 40 kHz, and the ultrasonic power is set to 400 W for cleaning for 20 minutes to obtain a first steel plate.

[0078] B: The first steel plate is subjected to cold rolling; the number of cold rolling passes is not less than 10, the reduction rate of each pass is less than the reduction rate of the previous pass, and the total cold rolling reduction rate does not exceed 80%.

[0079] Annealing treatment is carried out after every 2 rolling passes; annealing treatment includes: -3 In the Pa environment, the temperature is raised to 980°C at a heating rate of 8°C / s and maintained, and then cooled to room temperature with the furnace; wherein, the holding time of the annealing treatment is determined according to the thickness of the first steel plate, and is 3 minutes per millimeter.

[0080] After the last annealing treatment was completed, the temperature was lowered to 500° C. at a cooling rate of 50° C. / s for aging treatment for 3 hours to obtain a second steel plate.

[0081] This embodiment also provides a wearable device, which adopts the above-mentioned second steel plate.

[0082] Example 6

[0083] This embodiment provides a stainless steel plate for a wearable device, using the stainless steel prepared in Example 1 as a substrate and performing the following treatments:

[0084] A: An austenitic stainless steel substrate was obtained, and shot peening and polishing were performed in sequence to remove oxides on the surface of the stainless steel substrate; acetone was used as a cleaning liquid, and the ultrasonic frequency was set to 30 kHz and the ultrasonic power was set to 300 W for 10 minutes to obtain a first steel plate.

[0085] B: The first steel plate is subjected to cold rolling; the number of cold rolling passes is not less than 10, the reduction rate of each pass is less than the reduction rate of the previous pass, and the total cold rolling reduction rate does not exceed 80%.

[0086] Annealing treatment is carried out after every 2 rolling passes; annealing treatment includes: -3 In the Pa environment, the temperature was raised to 970°C at a heating rate of 6°C / s and kept warm, and then cooled to room temperature with the furnace; wherein, the holding time of the annealing treatment was determined according to the thickness of the first steel plate, and was kept warm for 2 minutes per millimeter.

[0087] After the last annealing treatment is completed, the temperature is lowered to 480°C at a cooling rate of 40°C / s for aging treatment for 1-3 hours to obtain a second steel plate.

[0088] This embodiment also provides a wearable device, which adopts the above-mentioned second steel plate.

[0089] Example 7

[0090] This embodiment provides a stainless steel plate for a wearable device, and the second steel plate prepared in Example 4 is subjected to the following treatments:

[0091] C: Electroplating a nickel layer on the surface of the second steel plate; using a mixture of nickel sulfate and ammonium chloride as the electroplating solution, the concentration of nickel ions in the electroplating solution is 200g / L. The electroplating current density is set at 2A / dm 2 , electroplating time is 10 minutes, and the temperature is controlled at 50℃.

[0092] D: Use laser femtosecond technology for nano-modification; set the laser wavelength to 800nm, the pulse width to 50fs, and the pulse energy density to 50J / cm 2 , spot diameter 6μm; perform a laser femtosecond treatment to obtain a nanowire modified structure; set the laser wavelength to 1030nm, the pulse width to 50fs, and the pulse energy density to 50J / cm2 , spot diameter 15μm; secondary laser femtosecond treatment was performed to obtain a nanopore-modified structure.

[0093] E: Prepare two passivation solutions of different concentrations, wherein the mass of citric acid in the low-concentration passivation solution is 10%; the mass of citric acid in the high-concentration passivation solution is 20%; spray the low-concentration passivation solution on the surface of the second steel plate and keep it at 40°C for 10 minutes; then soak the second steel plate in the high-concentration passivation solution at 50°C for 20 minutes. Preferably, annealing treatment is performed to demagnetize the non-magnetic stainless steel plate.

[0094] The surface of the non-magnetic stainless steel plate comprises a three-phase composite coating of a nickel layer, a nano-modification layer and a passivation layer.

[0095] Example 8

[0096] This embodiment provides a stainless steel plate for a wearable device, and the second steel plate prepared in Example 5 is subjected to the following treatments:

[0097] C: Electroplating a nickel layer on the surface of the second steel plate; using a mixture of nickel sulfate and ammonium chloride as the electroplating solution, the concentration of nickel ions in the electroplating solution is 400g / L. The electroplating current density is set at 10A / dm 2 , electroplating time is 30 minutes, and the temperature is controlled at 60℃.

[0098] D: Nano-modification using laser femtosecond technology; set the laser wavelength to 800nm, the pulse width to 60fs, and the pulse energy density to 100J / cm 2 , spot diameter 12μm; perform a laser femtosecond treatment to obtain a nanowire modified structure; set the laser wavelength to 1030nm, the pulse width to 60fs, and the pulse energy density to 100J / cm 2 , spot diameter 18μm; secondary laser femtosecond treatment was performed to obtain a nanopore-modified structure.

[0099] E: Prepare two passivation solutions of different concentrations, the mass of citric acid in the low-concentration passivation solution is 15%; the mass of citric acid in the high-concentration passivation solution is 25%; spray the low-concentration passivation solution on the surface of the second steel plate and keep it warm at 50°C for 20 minutes; then soak the second steel plate in the high-concentration passivation solution at 60°C for 30 minutes to obtain a non-magnetic stainless steel plate.

[0100] The surface of the non-magnetic stainless steel plate comprises a three-phase composite coating of a nickel layer, a nano-modification layer and a passivation layer.

[0101] Example 9

[0102] This embodiment provides a stainless steel plate for a wearable device, and the second steel plate prepared in Example 6 is subjected to the following treatments:

[0103] C: Electroplating a nickel layer on the surface of the second steel plate; using a mixture of nickel sulfate and ammonium chloride as the electroplating solution, the concentration of nickel ions in the electroplating solution is 300g / L. The electroplating current density is set at 7A / dm 2 Within the range, the electroplating time is 20 minutes and the temperature is controlled between 56°C.

[0104] D: Nano-modification using laser femtosecond technology; set the laser wavelength to 800nm, the pulse width to 55fs, and the pulse energy density to 80J / cm 2 , spot diameter 10μm; perform a laser femtosecond treatment to obtain a nanowire modified structure; set the laser wavelength to 1030nm, the pulse width to 55fs, and the pulse energy density to 80J / cm 2 , spot diameter 16μm; secondary laser femtosecond treatment was performed to obtain a nanopore-modified structure.

[0105] E: Prepare two passivation solutions of different concentrations, the mass of citric acid in the low-concentration passivation solution is 12%; the mass of citric acid in the high-concentration passivation solution is 22%; spray the low-concentration passivation solution on the surface of the second steel plate and keep it warm at 45°C for 15 minutes; then soak the second steel plate in the high-concentration passivation solution at 55°C for 25 minutes to obtain a non-magnetic stainless steel plate.

[0106] The surface of the non-magnetic stainless steel plate comprises a three-phase composite coating of a nickel layer, a nano-modification layer and a passivation layer.

[0107] Example 10

[0108] This embodiment provides a method for preparing a wearable stainless steel plate. For details, see Example 7, except that in step D: the laser wavelength is set to 1030 nm, the pulse width is set to 60 fs, and the pulse energy density is set to 100 J / cm 2 , spot diameter 18μm; laser femtosecond treatment was performed to obtain a nanopore-modified structure.

[0109] Embodiment 11

[0110] This embodiment provides a method for preparing a wearable stainless steel plate, see Example 7 for details, except that: Step D is performed under a nitrogen atmosphere.

[0111] Example 12

[0112] This embodiment provides a method for preparing a wearable stainless steel plate, see Example 8 for details, except that: Step D is performed under a nitrogen atmosphere.

[0113] Embodiment 13

[0114] This embodiment provides a method for preparing a wearable stainless steel plate, see Example 9 for details, except that: Step D is performed under a nitrogen atmosphere.

[0115] Embodiment 14

[0116] This embodiment provides a method for preparing a wearable stainless steel plate, which is specifically referred to in Example 7, except that the nano-modification in step D is not performed to obtain a stainless steel plate modified with nickel plating and passivation dual phases.

[0117] Embodiment 15

[0118] This embodiment provides a method for preparing a wearable stainless steel plate. Specifically, the stainless steel obtained in Example 1 is passivated.

[0119] The passivation treatment is to prepare two passivation solutions of different concentrations, in which the mass of citric acid accounts for 10% in the low-concentration passivation solution; the mass of citric acid accounts for 20% in the high-concentration passivation solution; the low-concentration passivation solution is sprayed on the surface of the stainless steel plate and kept warm at 40°C for 10 minutes; then the stainless steel plate is immersed in the high-concentration passivation solution at 50°C for 20 minutes.

[0120] Example 16

[0121] This embodiment provides a method for preparing a wearable stainless steel plate. Specifically, the stainless steel obtained in Example 1 is subjected to nickel plating.

[0122] The nickel plating treatment includes electroplating a nickel layer on the surface of the stainless steel plate; the electroplating is carried out using a mixture of nickel sulfate and ammonium chloride as the electroplating solution, and the concentration of nickel ions in the electroplating solution is 200g / L. The current density of the electroplating is set at 2A / dm 2 , electroplating time is 10 minutes, and the temperature is controlled at 50℃.

[0123] Comparative Example 1

[0124] This embodiment provides a method for preparing a wearable stainless steel plate, which is specifically referred to in Embodiment 1, except that: the number of cold rolling passes in step S20 is not less than 10, the reduction rate of each pass is the same, and the total cold rolling reduction rate does not exceed 80%.

[0125] The stainless steel plates of Examples 1-16 and Comparative Example 1 were tested, and the data are shown in Table 1 below.

[0126] Table 1

[0127]

[0128]

[0129] Thickness deviation = (Dd) / D×100%, where D is the thickest thickness of the stainless steel plate, and d is the thinnest thickness of the stainless steel plate.

[0130] The salt spray tolerance time is carried out at a temperature of 35°C using a 5% sodium chloride solution to test the corrosion resistance of the material. The longer the time, the better the corrosion resistance.

[0131] The Vickers hardness can reflect the wear resistance of the stainless steel material to a certain extent. The wear resistance of the stainless steel provided in the embodiment of the present invention is improved to a certain extent compared with the comparative example.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for preparing high nitrogen austenitic stainless steel, characterized in that: The following steps are involved: S10: obtaining a high-purity metal raw material according to the composition ratio of the high-nitrogen austenitic stainless steel, and then sequentially performing vacuum ball milling and solid-state nitriding treatment to obtain a mixed metal powder; S20: Sintering the mixed metal powder into a shape and continuously rolling the mixed metal powder into a metal sheet; S30: performing a solution treatment on the metal sheet to obtain the high nitrogen austenitic stainless steel having a completely recrystallized single austenite structure; The high nitrogen austenitic stainless steel includes the following elements by mass percentage: N 0.75-1.0%, Cr 17.5-19.0%, Mn 16.0-18.5%, Mo 2.5-4.0%, Ni not more than 0.5%, Si not more than 0.5%, C not more than 0.08%; the balance is Fe.

2. The preparation process according to claim 1, characterized in that: The solid nitriding treatment is to carry out nitriding treatment for 2-20 hours at a controlled temperature of 400-600° C. in a nitriding atmosphere; The nitriding atmosphere is a mixed gas of ammonia and nitrogen, in which the volume proportion of nitrogen is 75-90%.

3. The preparation process according to claim 1, characterized in that: The sintering molding is to press the mixed metal powder into a mold, and then control the sintering temperature to be 1200-1450° C. in a sintering atmosphere for staged sintering; The staged sintering includes: controlling the pressure not to exceed 3MPa for the first stage sintering, when the density is greater than 90%, controlling the pressure to 5-12MPa for the second stage sintering, and when the density is greater than 99%, rapidly cooling to room temperature at a speed of 30-40°C / min.

4. The preparation process according to claim 1, characterized in that: The sintering atmosphere is argon or a mixture of argon and nitrogen.

5. The preparation process according to claim 1, characterized in that: The continuous rolling is to perform multiple passes of continuous rolling on the material obtained by sintering to obtain the metal sheet with a thickness of 1-5 mm.

6. The preparation process according to claim 1, characterized in that: The solution treatment is carried out at a temperature of 1050-1100° C. for 2-4 hours, and then the temperature is rapidly reduced to room temperature at a speed of 30-40° C. / min.

7. The preparation process according to claim 1, characterized in that: The high nitrogen austenitic stainless steel is subjected to surface strengthening treatment; the surface strengthening treatment includes passivation treatment.

8. A high nitrogen austenitic stainless steel, characterized in that: The method is prepared by the preparation process described in any one of claims 1 to 7.

9. A wearable device, characterized in that: The austenitic stainless steel is prepared according to claim 8.

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