Method for reducing magnetism of austenitic stainless steel, austenitic stainless steel and application thereof

Abstract

The invention relates to the field of stainless steel, in particular to a method for reducing magnetism of austenitic stainless steel, the austenitic stainless steel and application of the austenitic stainless steel. The method comprises the following steps: annealing austenitic stainless steel; the annealing treatment process comprises the steps that the austenitic stainless steel is heated to 920-980 DEG C, subjected to heat preservation for 2-4 h and then cooled. The method can reduce the magnetism of the austenitic stainless steel, so that the performance of an electronic product is not influenced.

Description

Technical Field

[0001] The invention relates to the field of stainless steel, and in particular to a method for reducing the magnetism of austenitic stainless steel, austenitic stainless steel and applications thereof. Background Art

[0002] Magnetism is a common problem in stainless steel parts used in electronic equipment. For example, in the production of electric vacuum devices, electron guns, microwave devices, etc. require that the materials used are non-magnetic, mainly because the magnetic field can interfere with electromagnetic waves. When electromagnetic waves pass through the magnetic field, the strength and direction of the magnetic field may affect the propagation of electromagnetic waves. This interference may cause changes in the phase, amplitude or propagation path of the electromagnetic waves. The superposition of magnetic fields refers to the combination of the magnetic field effects of two or more magnetic fields when they exist at the same time. This superposition may cause the magnetic field to become more complex, thereby affecting the propagation characteristics of electromagnetic waves. Therefore, the magnetism of the materials used must be limited.

[0003] When designing a device, the selection of non-magnetic or weakly magnetic materials must be considered. The materials must be cheap, easy to weld, easy to process, and suitable for use in electric vacuums. Although 316L austenitic stainless steel is conventionally classified as non-magnetic stainless steel or weakly magnetic stainless steel, it often retains or produces certain magnetism due to composition differences or processing effects. However, general austenitic stainless steel is limited by its composition, and the content of austenite stabilizing elements is insufficient. At room temperature, the steel generally contains about 5-10% delta ferrite, which is slightly magnetic. Also, because austenite is not stable enough, part of the austenite structure is transformed into a deformation martensite structure during the cold working process. Since both delta ferrite and martensite are strong magnetic structures, 316L stainless steel exhibits different magnetism during processing and use.

[0004] Therefore, based on the characteristics of 316L stainless steel, there is an urgent need to provide a method for reducing the magnetism of 316L stainless steel, so that when 316L stainless steel is used to prepare electronic equipment, its magnetic permeability and remanence can be controlled so that the product meets the use requirements. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that 316L stainless steel has magnetism when used to prepare electronic products, thereby affecting the performance of the electronic products, and to provide a method for reducing the magnetism of austenitic stainless steel, austenitic stainless steel and its application. The method can reduce the magnetism of austenitic stainless steel without affecting the performance of the electronic products.

[0006] In order to achieve the above object, the first aspect of the present invention provides a method for reducing the magnetism of austenitic stainless steel, comprising: annealing the austenitic stainless steel; the annealing process comprises: heating the austenitic stainless steel to 920-980°C, keeping the temperature for 2-4 hours and then cooling.

[0007] Preferably, the annealing process comprises: heating the austenitic stainless steel to 940-960° C., keeping the temperature for 2-4 hours and then cooling.

[0008] Preferably, the austenitic stainless steel is 316L stainless steel.

[0009] Preferably, the 316L stainless steel is a 316L stainless steel semi-finished product and / or a 316L stainless steel finished product.

[0010] Preferably, the annealing process is performed in a vacuum device.

[0011] Preferably, the conditions of the vacuum equipment include at least: a pressure of 10 -5 -10 -3 Pa.

[0012] Preferably, the annealing process further comprises: evacuating the vacuum equipment to a vacuum of 1×10 -3 The temperature starts to rise at Pa.

[0013] Preferably, the heating rate is 230-330° C. / h.

[0014] Preferably, the cooling method is furnace cooling.

[0015] The second aspect of the present invention provides austenitic stainless steel obtained by the method described in the first aspect.

[0016] Preferably, the magnetic permeability of the austenitic stainless steel is not higher than 1.05, and the remanence is not higher than 0.5 Gs.

[0017] The third aspect of the present invention provides the use of the austenitic stainless steel described in the second aspect in the preparation of electric vacuum devices.

[0018] Through the above technical scheme, the method provided by the present invention can control the magnetic permeability of austenitic stainless steel to be no higher than 1.05 and the remanence to be no higher than 0.5Gs by adopting an annealing treatment method of heating austenitic stainless steel to 920-980°C and keeping it for 2-4 hours and then cooling it, so that it can meet the use requirements of electronic products, and can also improve the strength, toughness and corrosion resistance of austenitic stainless steel, with significant economic benefits. Moreover, the method has a simple process, is easy to operate, and can avoid the waste of austenitic stainless steel in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 316L stainless steel product annealing treatment temperature and time diagram in Example 1. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] In a first aspect, the present invention provides a method for reducing the magnetism of austenitic stainless steel, comprising: annealing the austenitic stainless steel; the annealing process comprises: heating the austenitic stainless steel to 920-980°C, keeping it warm for 2-4 hours, and then cooling it, the keeping temperature can be 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, or any value between the above two values, and the keeping time can be 2h, 3h, 4h, or any value between the above two values.

[0022] During the research, the inventor unexpectedly found that by adopting an annealing treatment method of heating austenitic stainless steel to 910-980℃ and keeping it for 2-4h and then cooling it, the magnetic permeability of austenitic stainless steel can be controlled to be no higher than 1.05 and the remanence can be controlled to be no higher than 0.5Gs, so that it can meet the use requirements of electronic products, and the strength, toughness and corrosion resistance of austenitic stainless steel can be improved, which has significant economic benefits. Moreover, the method has a simple process, is easy to operate, and can avoid the waste of austenitic stainless steel in the production process.

[0023] According to the present invention, preferably, the annealing process includes: heating the austenitic stainless steel to 940-960°C, keeping the temperature for 2-4 hours, and then cooling. The inventors found that under this preferred embodiment, the mechanical properties and corrosion resistance of the austenitic stainless steel can be ensured while significantly reducing its magnetism, so that it can meet the magnetic requirements of electronic product production.

[0024] According to the present invention, the austenitic stainless steel is a conventionally selected austenitic stainless steel in the art, for example, 304L stainless steel, 306L stainless steel, 321 stainless steel, 347 stainless steel, etc. Preferably, the austenitic stainless steel is 316L stainless steel.

[0025] According to the present invention, when 316L stainless steel is used to prepare electronic products, it is necessary to detect the semi-finished products of the 316L stainless steel used, and select the semi-finished products of the 316L stainless steel with qualified magnetic permeability and residual magnetism for processing to obtain the finished products of the 316L stainless steel, wherein the qualified standards of the magnetic permeability and residual magnetism of the 316L stainless steel semi-finished products can be adjusted according to the different electronic products prepared by using them, for example, when the magnetic permeability and residual magnetism of the 316L stainless steel semi-finished products are not higher than 1.05 and the residual magnetism is not higher than 0.5Gs, it meets the qualified standards of magnetic permeability and residual magnetism. When the magnetic permeability and residual magnetism of the 316L stainless steel semi-finished products used meet the requirements, but after further processing them into parts (i.e., 316L stainless steel finished products), when the magnetic permeability and residual magnetism of the parts are detected, the magnetic permeability and residual magnetism of the parts may not meet the requirements.

[0026] According to the present invention, 316L stainless steel can be a blank, a semi-finished product or a finished product of 316L stainless steel. Preferably, the 316L stainless steel is a 316L stainless steel semi-finished product and / or a 316L stainless steel finished product. The inventors have found that, under this preferred embodiment, by annealing the 316L stainless steel semi-finished product and / or the 316L stainless steel finished product, its magnetism can be reduced, thereby avoiding the waste of raw materials due to unqualified magnetism and reducing production costs.

[0027] In the present invention, austenitic stainless steel generally contains elements such as C, Mn, Si, P, S, Cr, and Mo, and different types of austenitic stainless steel contain different types of elements and element contents. For example, 316L stainless steel contains C, Mn, Si, P, S, Cr, and Mo, and the corresponding element contents are: C≤0.030wt%, Mn≤2.00wt%, Si≤1.00wt%, P≤0.045wt%, S≤0.030wt%, 16.00wt%≤Cr≤18.00wt%, 2.00wt%≤Mo≤3.00wt%.

[0028] In the present invention, 316L stainless steel semi-finished products refer to products that have undergone preliminary processing of 316L stainless steel plates, bars, pipes, etc., and have the prototype of the product. These semi-finished products have undergone preliminary processing during the production process and have not yet completed the final product form, but have already possessed certain usage functions; 316L stainless steel finished products refer to products that have completed the entire production process, including all necessary processes and quality control, and can be directly used or sold.

[0029] According to the present invention, the annealing treatment can be carried out in a heat treatment furnace or in a vacuum device. For example, when the austenitic stainless steel is a 316L stainless steel semi-finished product, the 316L stainless steel semi-finished product can be placed in a heat treatment furnace for annealing treatment, or in a vacuum furnace for annealing treatment; when the austenitic stainless steel is a 316L stainless steel finished product, it is placed in a vacuum furnace for annealing treatment.

[0030] According to the present invention, the annealing treatment can be carried out in a vacuum device; or in an inert gas-filled device, for example, a heating device filled with nitrogen. Preferably, the annealing treatment is carried out in a vacuum device. The inventors have found that, under this preferred embodiment, by placing austenitic stainless steel in a vacuum device for annealing, oxidation of the austenitic stainless steel can be effectively avoided, and the effect of the annealing treatment can be improved, thereby further reducing the magnetism of the austenitic stainless steel.

[0031] According to the present invention, in order to further reduce the magnetism of austenitic stainless steel, preferably, the conditions of the vacuum equipment at least include: a pressure of 10 -5 -10 -3 Pa, specifically 1×10 -5 Pa, 5×10 -5 Pa, 1×10 -4 Pa, 5×10 -4 Pa, 1×10 -3 Pa, or any value between the above two values.

[0032] According to the present invention, in order to further reduce the magnetism of austenitic stainless steel, preferably, the annealing process further includes: evacuating the vacuum equipment to 1×10 -3 The temperature starts to rise at 0.0547°C Pa. The inventors have found that under this preferred embodiment, the oxidation of stainless steel can be further avoided, thereby further reducing the magnetism of austenitic stainless steel.

[0033] In the present invention, the vacuum equipment is evacuated to 1×10 -3 After the temperature starts to rise at 10 Pa, the vacuum is continuously drawn to make the pressure inside the vacuum equipment reach 10 -5 -10 -3 Pa.

[0034] According to the present invention, in order to further reduce the magnetism of austenitic stainless steel, preferably, the heating rate is 230-330°C / h, specifically 230°C / h, 250°C / h, 270°C / h, 290°C / h, 310°C / h, 330°C / h, or any value between the foregoing two values.

[0035] According to the present invention, the cooling method can be air cooling, furnace cooling or water cooling. Preferably, the cooling method is furnace cooling.

[0036] In the present invention, when the cooling is performed by furnace cooling, the austenitic stainless steel is taken out when the temperature in the vacuum equipment is lower than 60°C.

[0037] According to the present invention, after the austenitic stainless steel is subjected to an annealing treatment, the magnetic permeability and residual magnetism are tested. If it is found that the magnetic properties of the austenitic stainless steel do not meet the qualified standards of magnetic permeability and residual magnetism, the annealing treatment can be performed again. The test personnel can adjust the number of annealing treatments according to production needs.

[0038] According to a particularly preferred embodiment of the present invention, a method for reducing the magnetic properties of austenitic stainless steel is provided, comprising: heating the austenitic stainless steel in a vacuum device at a rate of 230-330°C / h to 940-960°C, maintaining the temperature for 2-4h, and then cooling the austenitic stainless steel with the furnace; the pressure of the vacuum device is 10 -5 -10 -3 Pa, evacuate the vacuum equipment to 1×10 -3 The temperature starts to rise at Pa;

[0039] Among them, the austenitic stainless steel is 316L stainless steel, and the 316L stainless steel is 316L stainless steel semi-finished product and / or 316L stainless steel finished product.

[0040] In the above preferred embodiment, through a specific annealing treatment method, the magnetic permeability of austenitic stainless steel can be controlled to be no higher than 1.05, and the remanence can be controlled to be no higher than 0.5Gs, so that it meets the use requirements of electronic products, and can also improve the strength, toughness and corrosion resistance of austenitic stainless steel, with significant economic benefits. Moreover, the method has a simple process, is easy to operate, and can avoid the waste of austenitic stainless steel in the production process.

[0041] In a second aspect, the present invention provides austenitic stainless steel obtained by the method described in the first aspect.

[0042] According to the present invention, preferably, the magnetic permeability of the austenitic stainless steel is not higher than 1.05, and the residual magnetism is not higher than 0.5Gs. Austenitic stainless steel that meets the above magnetic permeability and residual magnetism requirements has weaker magnetism and can meet its application in electronic products.

[0043] According to the present invention, the magnetic permeability of austenitic stainless steel can be measured by a magnetic permeability meter, and the residual magnetism can be measured by a Gauss meter.

[0044] In a third aspect, the present invention provides the use of the austenitic stainless steel described in the second aspect in the preparation of electric vacuum devices.

[0045] The present invention is described in detail below with reference to the embodiments, but the scope of the present invention is not limited thereby.

[0046] In the following examples, 316L stainless steel semi-finished products were purchased from Qingtuo Group Co., Ltd., with thicknesses of 60 mm and 80 mm. Unless otherwise specified, the remaining raw materials or reagents were conventional commercial products.

[0047] In the following examples, a magnetic permeability meter was used to test the magnetic permeability of austenitic stainless steel, and a gaussmeter was used to measure the remanence of austenitic stainless steel, and the measurements were performed according to the methods in the respective instructions.

[0048] Example 1

[0049] (1) Process the qualified parts of 316L stainless steel semi-finished products into 316L stainless steel finished products; 316L stainless steel semi-finished products meet the requirements of GB / T 24511-2017 Stainless steel and heat-resistant steel plates and strips for pressure equipment;

[0050] (2) The magnetic permeability and remanence of the 316L stainless steel products were measured, and the 316L stainless steel products with a magnetic permeability higher than 1.05 and a remanence higher than 0.5 Gs were annealed. The annealing process included: placing the 316L stainless steel products in a vacuum furnace and evacuating the vacuum to 1×10 -3 Pa, heating was started, and the temperature was raised to 950°C at a heating rate of 280°C / h, and the temperature was kept at 950°C for 2h, and then the furnace was cooled, and the 316L stainless steel product was taken out after cooling to the vacuum furnace temperature below 60°C;

[0051] (3) The magnetic permeability and remanence of the 316L stainless steel product after annealing were tested. The results are shown in Table 1.

[0052] The relationship between the temperature and time of the annealing treatment of the 316L stainless steel product in Example 1 is shown in Figure 1 .

[0053] Example 2

[0054] (1) Rough-process the qualified 316L stainless steel blank parts into 316L stainless steel semi-finished products; 316L stainless steel semi-finished products meet the requirements of GB / T 24511-2017 Stainless steel and heat-resistant steel plates and strips for pressure equipment;

[0055] (2) The magnetic permeability and remanence of 316L stainless steel semi-finished products were measured, and annealing treatment was performed on the 316L stainless steel semi-finished products with a magnetic permeability higher than 1.05 and a remanence higher than 0.5 Gs. The annealing process includes: placing the 316L stainless steel semi-finished products in a vacuum furnace and evacuating the vacuum to 1×10 -3Pa, heating was started, and the temperature was raised to 940°C at a heating rate of 230°C / h, and then kept at 940°C for 4h and then cooled with the furnace, and the 316L stainless steel product was taken out after cooling to the vacuum furnace temperature below 60°C;

[0056] (3) The magnetic permeability and remanence of the 316L stainless steel semi-finished product after annealing were tested. The results are shown in Table 1.

[0057] Example 3

[0058] (1) Process the qualified parts of 316L stainless steel semi-finished products into 316L stainless steel finished products; 316L stainless steel semi-finished products meet the requirements of GB / T 24511-2017 Stainless steel and heat-resistant steel plates and strips for pressure equipment;

[0059] (2) The magnetic permeability and remanence of the 316L stainless steel products were measured, and the 316L stainless steel products with a magnetic permeability higher than 1.05 and a remanence higher than 0.5 Gs were annealed. The annealing process included: placing the 316L stainless steel products in a vacuum furnace and evacuating the vacuum to 1×10 -3 Pa, heating was started, and the temperature was raised to 960°C at a heating rate of 330°C / h, and the temperature was kept at 960°C for 3h, and then cooled with the furnace, and the 316L stainless steel product was taken out after cooling to the vacuum furnace temperature below 60°C;

[0060] (3) The magnetic permeability and remanence of the 316L stainless steel product after annealing were tested. The results are shown in Table 1.

[0061] Example 4

[0062] (1) Process the qualified parts of 316L stainless steel semi-finished products into 316L stainless steel finished products; 316L stainless steel semi-finished products meet the requirements of GB / T 24511-2017 Stainless steel and heat-resistant steel plates and strips for pressure equipment;

[0063] (2) The magnetic permeability and remanence of the 316L stainless steel products were measured, and the 316L stainless steel products with a magnetic permeability higher than 1.05 and a remanence higher than 0.5 Gs were annealed. The annealing process included: placing the 316L stainless steel products in a vacuum furnace and evacuating the vacuum to 1×10 -3 Pa, heating was started, and the temperature was raised to 980°C at a heating rate of 300°C / h, and the temperature was kept at 980°C for 2h, and then cooled with the furnace, and the 316L stainless steel product was taken out after cooling to the vacuum furnace temperature below 60°C;

[0064] (3) The magnetic permeability and remanence of the 316L stainless steel product after annealing were tested. The results are shown in Table 1.

[0065] Example 5

[0066] (1) Process the qualified parts of 316L stainless steel semi-finished products into 316L stainless steel finished products; 316L stainless steel semi-finished products meet the requirements of GB / T 24511-2017 Stainless steel and heat-resistant steel plates and strips for pressure equipment;

[0067] (2) The magnetic permeability and remanence of the 316L stainless steel products were measured, and the 316L stainless steel products with a magnetic permeability higher than 1.05 and a remanence higher than 0.5 Gs were annealed. The annealing process included: placing the 316L stainless steel products in a vacuum furnace and evacuating the vacuum to 1×10 -3 Pa, heating was started, and the temperature was raised to 920°C at a heating rate of 250°C / h, and the temperature was kept at 920°C for 3h, and then cooled with the furnace, and the 316L stainless steel product was taken out after cooling to the vacuum furnace temperature below 60°C;

[0068] (3) The magnetic permeability and remanence of the 316L stainless steel product after annealing were tested. The results are shown in Table 1.

[0069] Example 6

[0070] The magnetic properties of 316L stainless steel are reduced according to the method of Example 1, except that in step (2), the annealing process includes: placing the 316L stainless steel product in a heat treatment furnace and starting heating, heating the temperature to 950°C at a heating rate of 280°C / h, and keeping the temperature at 950°C for 2h and then cooling with the furnace, cooling to the temperature of the heat treatment furnace below 60°C and taking out the 316L stainless steel product.

[0071] Example 7

[0072] The magnetic properties of 316L stainless steel are reduced according to the method of Example 1, except that in step (2), the annealing process includes: placing the 316L stainless steel product in a vacuum furnace, starting heating and evacuating the vacuum furnace, heating the temperature to 950°C at a heating rate of 280°C / h, and keeping the temperature at 950°C for 2h, then cooling with the furnace, cooling to the vacuum furnace temperature below 60°C, and taking out the 316L stainless steel product.

[0073] Example 8

[0074] The magnetic properties of 316L stainless steel were reduced according to the method of Example 1, except that step (2) was replaced by:

[0075] (2) The magnetic permeability and remanence of the 316L stainless steel products were measured, and the 316L stainless steel products with a magnetic permeability higher than 1.05 and a remanence higher than 0.5 Gs were annealed. The annealing process included: placing the 316L stainless steel products in a vacuum furnace and evacuating the vacuum to 1×10 -3 Pa, and the temperature was raised to 950°C at a heating rate of 280°C / h. After being kept at 950°C for 2h, the sample was taken out of the vacuum furnace and cooled in air.

[0076] Comparative Example 1

[0077] The magnetic properties of 316L stainless steel were reduced according to the method of Example 1, except that in step (2), the annealing process was replaced by: placing the 316L stainless steel product in a vacuum furnace and evacuating the vacuum to 1×10 -3 Pa started heating, the temperature was raised to 1050°C, and it was kept at 1050°C for 2h and then cooled with the furnace. The 316L stainless steel product was taken out after cooling to the vacuum furnace temperature below 60°C.

[0078] Comparative Example 2

[0079] The magnetic properties of 316L stainless steel were reduced according to the method of Example 1, except that in step (2), the annealing process was replaced by: placing the 316L stainless steel product in a vacuum furnace and evacuating the vacuum to 1×10 -3 Pa, and the temperature was raised to 800°C at a heating rate of 280°C / h, and then kept at 800°C for 2h and cooled with the furnace. The 316L stainless steel product was taken out after cooling to the vacuum furnace temperature below 60°C.

[0080] Table 1

[0081] serial number Magnetic Permeability Remanence(Gs) Example 1 1.03 0.32 Example 2 1.02 0.25 Example 3 1.03 0.35 Example 4 1.04 0.38 Example 5 1.05 0.40 Example 6 1.04 0.44 Example 7 1.04 0.46 Example 8 1.05 0.50 Comparative Example 1 1.08 0.60 Comparative Example 2 1.09 0.65

[0082] From the results in Table 1, it can be seen that compared with Comparative Examples 1-2, Examples 1-8 use the method provided by the present invention to reduce the magnetism of austenitic stainless steel, and adopt an annealing treatment method in which the austenitic stainless steel is heated to 920-980°C and kept for 2-4 hours and then cooled, so that the magnetic permeability of the austenitic stainless steel can be controlled to be no higher than 1.05 and the remanence can be controlled to be no higher than 0.5Gs, so that it meets the use requirements of electronic products and has significant economic benefits. Moreover, the method has a simple process, is easy to operate, and can avoid the waste of austenitic stainless steel in the production process.

[0083] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for reducing the magnetic properties of austenitic stainless steel, characterized in that: include: Annealing of austenitic stainless steel; The annealing process includes: heating the austenitic stainless steel to 920-980° C., keeping the temperature for 2-4 hours, and then cooling.

2. The method according to claim 1, characterized in that The annealing process includes: heating the austenitic stainless steel to 940-960° C., keeping the temperature for 2-4 hours, and then cooling.

3. The method according to claim 1, characterized in that The austenitic stainless steel is 316L stainless steel; Preferably, the 316L stainless steel is a 316L stainless steel semi-finished product and / or a 316L stainless steel finished product.

4. The method according to any one of claims 1 to 3, characterized in that The annealing process is performed in a vacuum device.

5. The method according to claim 4, characterized in that The conditions of the vacuum equipment include at least: a pressure of 10 -5 -10 -3 Pa; Preferably, the annealing process further comprises: evacuating the vacuum equipment to a vacuum of 1×10 - 3 Pa.

6. The method according to any one of claims 1 to 3, characterized in that: The heating rate is 230-330° C. / h.

7. The method according to any one of claims 1 to 3, characterized in that The cooling method is furnace cooling.

8. Austenitic stainless steel obtained by the method according to any one of claims 1 to 7.

9. The austenitic stainless steel according to claim 8, characterized in that: The magnetic permeability of the austenitic stainless steel is not higher than 1.05, and the residual magnetism is not higher than 0.5 Gs.

10. Use of the austenitic stainless steel according to claim 9 in the preparation of electric vacuum devices.

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