High-manganese non-magnetic stainless steel and its preparation process

Abstract

The present application relates to a kind of high manganese non-magnetic stainless steel and its preparation process, steel chemical composition includes by weight percentage:C:0.07~0.25%, Si:0.20~0.6%, Mn:11.5~22%, Cr:10~17%, Ni:0.95~6%, Cu:0.25~0.9%, N:0.15~0.26%, P≤0.05%, S≤0.005%, Mo:0.05~1.0%, Al:0.01~0.1%, Nb≤0.5%, Pb<0.0002%, Cd≤0.001%, the rest is Fe and inevitable impurities.The tensile strength of the non-magnetic stainless steel of the present application is ≥515MPa, yield strength is ≥205MPa, elongation is ≥35%, HRB≤99 or HV≤249, the non-magnetic stainless steel is mainly used for reprocessing production button, zipper, clothing accessories, mechanical hardware and deep drawing products, etc., the magnetic permeability after reprocessing is ≤1.01×10 ‑6 H / m.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical process, and in particular relates to high-manganese non-magnetic stainless steel and a preparation process thereof. Background Art

[0002] Austenitic stainless steel refers to stainless steel with an austenitic structure at room temperature. Austenitic stainless steel is non-magnetic, has good elongation, good formability, and also has excellent corrosion resistance and weldability, making it widely used.

[0003] However, ordinary austenitic stainless steel still has weak magnetism, especially after deep drawing and other mechanical processing, its weak magnetic characteristics are more obvious, and the magnetic permeability is usually greater than 1.01×10 -6 H / m, it is difficult to use in buttons, zippers, clothing accessories, mechanical hardware and deep-drawn products, which require absolute non-magnetic applications. Summary of the Invention

[0004] In order to solve the above technical problems existing in the prior art, the purpose of the present invention is to provide a high manganese non-magnetic stainless steel and its preparation process. The non-magnetic stainless steel of the present invention has a tensile strength of ≥515MPa, a yield strength of ≥205MPa, an elongation of ≥35%, an HRB of ≤99 or an HV of ≤249. The non-magnetic stainless steel is mainly used for reprocessing and producing buttons, zippers, clothing accessories, mechanical hardware and deep-drawn products, etc. The magnetic permeability after reprocessing is ≤1.01×10 -6 H / m.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A high manganese non-magnetic stainless steel is characterized in that the chemical components in the steel include, by weight percentage, C: 0.07%-0.25%, Si: 0.20%-0.6%, Mn: 11.5%-22%, Cr: 10%-17%, Ni: 0.95%-6%, Cu: 0.25%-0.9%, N: 0.15%-0.26%, P≤0.05%, S≤0.005%, Mo: 0.05%-1.0%, Al: 0.01%-0.1%, Nb≤0.5%, Pb<0.002%, Cd≤0.001%, and the remainder is Fe and unavoidable impurities.

[0007] At the same time, it is necessary to meet the requirements of P+S≤0.05% and the martensite temperature Md30=551-462 * (C%+N%)-92 * (Si%) -8.1 * (Mn%)-29 * (Ni%+Cu%)-13.7 *(Cr%) - 18.5 * (Mo%) ≤ 100.

[0008] The tensile strength of the stainless steel is ≥ 515 MPa, the yield strength is ≥ 205 MPa, the elongation is ≥ 35%, HRB is ≤ 99 or HV is ≤ 249, and the magnetic permeability after reprocessing is ≤ 1.01 x 10 -6 H / m.

[0009] The stainless steel is used for producing buttons, zippers, clothing accessories, mechanical hardware and deep-drawing products.

[0010] A production process of high-manganese non-magnetic stainless steel, specifically comprising:

[0011] 1) Chemical composition control: In addition to the conventional chemical composition control, in order to ensure that the magnetic permeability of the finished product is ≤ 1.01 x 10 - 6 H / m, the martensitic phase transformation during the cold working process of the product is reduced to cause the increase of the material magnetism, and the content of Al needs to be controlled in the range of 0.01% to 0.1% to improve the purity of the material.

[0012] Md30 = 551 - 462 * (C% + N%) - 92 * (Si%) - 8.1 * (Mn%) - 29 * (Ni% + Cu%) - 13.7 * (Cr%) - 18.5 * (Mo%) ≤ 100; in order to ensure the yield rate of the material after cold working, the content of Al needs to be controlled in the range of 0.01% to 0.1% to improve the purity of the material.

[0013] 2) Continuous casting process: the superheat of the continuous casting liquid steel is controlled in the range of 10 to 30℃, the continuous casting speed is 0.8 to 1.2 m / s, the continuous casting electromagnetic stirring current is controlled in the range of 1000 to 1600 A, and the two cooling zones of the continuous casting adopt weak cooling mode with specific water consumption ≤ 1.0 L / kg.

[0014] 3) Hot rolling production process: the billet enters the heating furnace to be heated to a temperature of 1250 to 1300℃, is heated for 180 to 280 minutes to be discharged, enters high-pressure dephosphorization to be rolled to a thickness of 30 to 50mm through 3 to 5 passes of back-and-forth rolling, and then enters 5 to 7 continuous rolling to be once formed to obtain a black skin steel coil with a thickness of 6.0 to 2.0mm and a width of 900 to 1600mm.

[0015] 4) The black skin steel coil is stored in a warehouse to be naturally cooled for 3 to 5 days, 1 to 2 coils are sampled for inspection, and whether there are peeling, cracks and the like is checked to be qualified to enter the next production process.

[0016] 5) Solution pickling production process: The black steel coil undergoes a high-temperature annealing heat treatment at 1100-1200°C before pickling. The acid composition ratio is 150-300 g / L sulfuric acid, 100-200 g / L nitric acid, and 5-15 g / L hydrofluoric acid. The TV value speed of the entire solution pickling line is 80-150 m / min. After that, the silvery white hot-rolled high-manganese stainless steel coil is obtained by coiling. The coil specifications are 6.0-2.0 mm and the width is 900-1600 mm.

[0017] 6) Cold rolling production process: The silvery-white high-manganese stainless steel coil is cut into different widths and sent to a large four-roll mill. After 6 to 15 reciprocating rolling passes, it becomes a semi-finished product; the semi-finished product with a thickness of 0.4 to 1.5 mm enters the annealing furnace for high-temperature heat treatment at 1080 to 1200 ° C. The steel coil runs at a speed of 5 to 20 m / min. Subsequently, it is trimmed and re-reeled, and enters the finishing rolling unit. It is finished by 3 to 7 passes to form a finished product, which is then subjected to high-temperature heat treatment at 1080 to 1200 ° C again. Finally, a bright silvery-white stainless steel finished strip with a thickness of 0.07 to 0.7 mm is formed, which is packaged and stored and delivered to the customer.

[0018] The present invention undergoes two high-temperature heat treatments at 1080-1200° C. during the rolling process, thereby ensuring the non-magnetic cold working performance of the austenitic stainless steel and improving the forming performance of the steel material, with an elongation of ≥35%.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention effectively avoids the formation of magnetic martensite after hot rolling and cold rolling by regulating the chemical composition and coordinating the heat treatment process, while achieving the softness, strong tensile strength and ductility of the steel. The non-magnetic stainless steel of the present invention has a tensile strength of ≥515MPa, a yield strength of ≥205MPa, an elongation of ≥35%, an HRB of ≤99 or an HV of ≤249, and a magnetic permeability of ≤1.01×10 -6 H / m, this non-magnetic stainless steel is mainly used for reprocessing and producing buttons, zippers, clothing accessories, mechanical hardware and deep-drawn products. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the specific implementation methods of the present invention are further described below in conjunction with examples. The following examples are used to specifically illustrate the contents of the present invention. These examples are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0022] The chemical composition of the embodiment of the present invention is shown in Table 1; the production process parameters of the embodiment are shown in Table 2; the pickling composition of the embodiment is shown in Table 3; and the properties of the steel plate of the embodiment are shown in Table 4.

[0023] Table 1 Chemical composition of Examples 1-10 (wt%)

[0024] Example C Si Mn Cr Ni Cu N P S Mo Al Nb Pb Cd P+S Md30 212W 0.13 0.25 11.8 13.3 1.0 0.41 0.17 0.046 0.0015 0.05 0.012 0.5 0.0018 0.001 0.0475 90.5 213W 0.17 0.2 15.5 13.2 1.0 0.48 0.22 0.045 0.0010 0.05 0.016 0.5 0.0008 0.001 0.090 18.75 216W 0.1 0.45 16.5 13.1 1.1 0.51 0.22 0.041 0.0021 0.05 0.23 0.05 0.0005 0.001 0.0431 38.29 217W 0.14 0.35 18.1 12.6 0.95 0.45 0.21 0.045 0.0007 0.055 0.013 0.5 0.0004 0.001 0.0457 25.23 226W 0.09 0.115 18 12.1 1.0 0.35 0.2 0.045 0.0005 0.05 0.057 0.5 0.0008 0.001 0.0455 64.32 XW214 0.12 0.33 14 17 4.2 0.50 0.21 0.035 0.0004 0.05 0.078 0.5 0.0007 0.001 0.0354 -88.02 XW216 0.09 0.31 15 16.5 5.0 0.8 0.16 0.028 0.0031 0.05 0.0.85 0.5 0.0005 0.001 0.0311 -98.43

[0025] Table 2 Production process parameters of Examples 1-10

[0026]

[0027]

[0028] Table 2 Production process parameters of Examples 1-10 (continued)

[0029]

[0030] Table 3 Acid wash ingredients for Examples 1-10

[0031] Example Sulfuric acid / g / L Nitric acid / g / L Hydrofluoric acid / g / L Pickling line TV value speed m / min 212w 300 200 15 85 213w 200 120 15 95 216w 200 120 8 100 217w 150 100 5 120 226w 150 100 5 130 Xw214 280 180 15 110 Xw216 280 180 15 110

[0032] Table 4 Properties of finished steel plates produced in Examples 1-10

[0033]

[0034]

Claims

1. A high manganese non-magnetic stainless steel, characterized in that: The chemical composition of the steel includes, by weight percentage: C: 0.07% to 0.25%, Si: 0.20% to 0.6%, Mn: 11.5% to 22%, Cr: 10% to 17%, Ni: 0.95% to 6%, Cu: 0.25% to 0.9%, N: 0.15% to 0.22%, P≤0.05%, S≤0.005%, Mo: 0.05% to 1.0%, Al: 0.01% to 0.1%, Nb: 0.05% to 0.5%, Pb<0.002%, Cd≤0.001%, and the rest is Fe and unavoidable impurities; The production process of the high manganese non-magnetic stainless steel specifically includes: 1) Hot rolling production process: The steel billet enters the heating furnace and is heated to 1250-1300℃ for 180-280 minutes before being taken out of the furnace. After high-pressure dephosphorization, it enters the rough rolling and continuous rolling to obtain black steel coil; 2) The black steel coil is cooled naturally for 3 to 5 days; 3) Solution pickling production process: After the black steel coil undergoes high-temperature annealing heat treatment at 1100-1200°C, it enters the pickling stage and is then coiled to obtain a silvery white hot-rolled high-manganese stainless steel coil; 4) Cold rolling production process: The semi-finished product is rolled in a four-high rolling mill, then enters the annealing furnace for high-temperature heat treatment at 1080-1200℃, with the coil running at a speed of 5-20m / min. The finished product then enters the finishing mill, where it undergoes another high-temperature heat treatment at 1080-1200℃, ultimately forming a bright silver-white stainless steel strip. The tensile strength of the stainless steel is ≥515MPa, the yield strength is ≥205MPa, the elongation is ≥35%, the hardness is ≤99HRB or HV ≤249, and the magnetic permeability after reprocessing is ≤1.01×10 -6 H / m.

2. The high manganese non-magnetic stainless steel according to claim 1, characterized in that: P+S≤0.05%, and martensite temperature Md30=551-462 * (C%+N%)-92 * (Si%) -8.1 * (Mn%)-29 * (Ni%+Cu%)-13.7 * (Cr%)-18.5 * (Mo%)≤100.

3. The high manganese non-magnetic stainless steel according to claim 1, characterized in that: The stainless steel is used for producing buttons, zippers, clothing accessories, mechanical hardware and deep-drawn products.

4. A production process for high manganese non-magnetic stainless steel according to any one of claims 1 to 3, characterized in that: Specifically include: 1) Hot rolling production process: The steel billet enters the heating furnace and is heated to 1250-1300℃ for 180-280 minutes before being taken out of the furnace. After high-pressure dephosphorization, it enters the rough rolling and continuous rolling to obtain black steel coil; 2) The black steel coil is cooled naturally for 3 to 5 days; 3) Solution pickling production process: After the black steel coil undergoes high-temperature annealing heat treatment at 1100-1200°C, it enters the pickling stage and is then coiled to obtain a silvery white hot-rolled high-manganese stainless steel coil; 4) Cold rolling production process: The semi-finished product is rolled on a four-high rolling mill and then enters the annealing furnace for high-temperature heat treatment at 1080-1200℃. The steel coil runs at a speed of 5-20m / min. It then enters the finishing rolling unit, where the finished product is again subjected to high-temperature heat treatment at 1080-1200℃ to form a bright silver-white stainless steel finished strip.

5. The production process of high manganese non-magnetic stainless steel according to claim 4, characterized in that: It also includes a continuous casting process, in which the superheat of the continuous casting molten steel is controlled at 10-30°C, and the continuous casting speed is 0.8-1.2m / s; the continuous casting electromagnetic stirring current is controlled at 1000-1600A, and the continuous casting secondary cooling zone adopts a weak cooling mode, with a specific water volume ≤1.0L / kg.

6. The production process of high manganese non-magnetic stainless steel according to claim 4, characterized in that: The rough rolling is repeated 3 to 5 times to roll the steel billet to a thickness of 30 to 50 mm, and then the steel billet is rolled into a black steel coil with a thickness of 6.0 to 2.0 mm and a width of 900 to 1600 mm through 5 to 7 continuous rolling processes.

7. The production process of high manganese non-magnetic stainless steel according to claim 4, characterized in that: The composition ratio of the acid in step 4) is: 150-300 g / L of sulfuric acid, 100-200 g / L of nitric acid, and 5-15 g / L of hydrofluoric acid. The TV value speed of the entire solution pickling line is 80-150 m / min.

8. The production process of high manganese non-magnetic stainless steel according to claim 4, characterized in that: In the step 5), the four-high rolling mill performs 6 to 15 reciprocating passes, and the finishing rolling is performed in 3 to 7 passes.

9. The production process of high manganese non-magnetic stainless steel according to claim 4, characterized in that: The thickness of the semi-finished product is 0.4-1.5 mm, and the thickness of the finished stainless steel strip is 0.07-0.7 mm.

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