Stainless steel suitable for reducing diameter treatment, production process thereof and superconducting coil armoring pipe

Abstract

The application discloses a stainless steel suitable for diameter reduction treatment, a production process thereof and a superconducting coil armoring pipe, and belongs to the technical field of stainless steel. The stainless steel is prepared by the following steps: after raw materials for smelting are added into a vacuum smelting furnace, vacuumizing treatment is carried out; after being heated to material melting, nitrogen is filled into the furnace to 0.02-0.1 MPa and kept; manganese-containing materials are added; after the manganese-containing materials are melted, Cr2N is added; after the Cr2N is melted and there is no bubble on the liquid surface of the molten steel, boron-containing materials are added; after being melted, the stainless steel is obtained by casting. The application limits 0.01%<=Nb<=0.08% and adds trace B. Nb mainly forms MX phase with N, can produce certain precipitation strengthening effect, but at the same time, can also affect the low-temperature plasticity and toughness of the product; and the B element can inhibit the grain boundary sensitization after aging. In order to ensure the strength of the stainless steel, diameter reduction cold working treatment is carried out on the pipe, and the Nb element content and the diameter reduction cold working process are controlled, so that excellent strength and plasticity matching after aging is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of stainless steel, in particular to a stainless steel suitable for diameter reduction treatment and a production process thereof and a superconducting coil armor pipe. BACKGROUND

[0002] In order to realize controllable nuclear fusion, the mainstream bearing equipment currently researched is a "Tokamak" ring device. The Tokamak contains a large number of superconducting coil structures. The superconducting coil structure is composed of an internal superconducting wire and an external armor pipe. The armor pipe provides sufficient strength support for the internal superconducting wire. In order to make the two fully fit, the superconducting wire needs to be inserted into the armor pipe, and then the pipe is subjected to cold extrusion treatment, that is, diameter reduction treatment. After the superconducting coil after cold extrusion is subjected to superconducting phase heat treatment, it can have low-temperature superconducting performance. However, the diameter reduction and heat treatment process greatly reduces the toughness and plasticity of the mainstream austenitic stainless steel in the industry. SUMMARY

[0003] The purpose of the present application is to provide a stainless steel suitable for diameter reduction treatment and a production process thereof and a superconducting coil armor pipe. The stainless steel still has excellent toughness and plasticity after diameter reduction and aging treatment, and can be made into a superconducting coil armor pipe.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0005] A production process of a stainless steel suitable for diameter reduction treatment, comprising the following steps (1)-(9):

[0006] (1) adding pure iron, molybdenum-containing material, vanadium-containing material, niobium-containing material, silicon-containing material, nickel-containing material and chromium-containing material in corresponding proportions according to the composition of the stainless steel in a melting furnace;

[0007] (2) vacuumizing the melting furnace;

[0008] (3) heating until the material is melted;

[0009] (4) controlling the temperature of the melting furnace to be 1500℃±20℃ after melting;

[0010] (5) filling nitrogen gas to make the pressure of the melting furnace reach 0.02-0.1MPa;

[0011] (6) adding manganese-containing material in the molten steel;

[0012] (7) adding Cr2N in batches (2-3 times) after the manganese-containing material is completely melted;

[0013] (8) after the Cr2N is completely melted and no gas bubble is emitted from the liquid surface of the molten steel, a boron-containing material is added;

[0014] (9) the stainless steel can be obtained by casting after the boron-containing material is melted.

[0015] In the step (1), the Nb element is added in an amount of 0.01≤Nb≤0.08wt.%;

[0016] In the step (8), the B element is added in an amount of 0.0015%≤B≤0.0050wt.%.

[0017] In the step (7), the Cr2N is added in an amount calculated according to the nitrogen yield of 50-70% in the stainless steel.

[0018] In the step (2), the vacuum degree in the smelting furnace after the vacuum treatment is 60Pa or more.

[0019] In the step (8), the boron-containing material is melted and stirred for 10s-60s before casting.

[0020] The present application also provides a stainless steel suitable for reducing processing, which is prepared by the above production process, and the chemical composition of the stainless steel is as follows in terms of percentage by weight:

[0021] C<0.015%, Cr 18-25%, Ni 10-15%, Mn 1-10%, Mo 1-3%, Si<1.0%, N 0.25-0.45%, Nb 0.01-0.08%, V 0.1%-0.3%, S<0.008%, P<0.02%, B 0.0010-0.0050%, and Fe is the balance.

[0022] The present application also provides a superconducting coil armoring pipe made of the stainless steel, and the processing process of the pipe comprises the following steps (A)-(F):

[0023] (A) electroslag remelting: electroslag remelting treatment is performed on the above-mentioned stainless steel ingot to obtain an electroslag ingot;

[0024] (B) forging: the electroslag ingot is forged into a forged bar;

[0025] (C) hot extrusion: the forged bar is hot extruded to be shaped into a corresponding pipe;

[0026] (D) cold drawing or cold rolling treatment: the hot extruded pipe is subjected to cold drawing or cold rolling treatment to obtain a corresponding pipe;

[0027] (E) solid solution treatment: the pipe is subjected to solid solution treatment; the temperature of the solid solution treatment is 1020℃-1150℃;

[0028] (F) reducing treatment: the pipe material after solution treatment is subjected to cold deformation treatment to obtain the pipe material after reducing treatment;

[0029] (G) aging treatment: the pipe material after reducing treatment is subjected to aging treatment.

[0030] The reducing treatment in the above step (F) reduces the inner hole diameter of the pipe material by 1.5-5 mm and increases the length by 2% to 8%.

[0031] The armoring pipe material is stretched at -269 DEG C, and the yield strength is greater than or equal to 1500 MPa; the tensile strength is greater than or equal to 1800 MPa, and the elongation is greater than or equal to 25%; the fracture toughness at -269 DEG C is greater than 130 MPa.m 1 / 2 .

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] 1. The present application limits the Nb content to 0.01≤Nb≤0.08wt.%, and the Nb element is a strong nitride-forming element, which will combine with the N element to form a dispersed NbN strengthening phase during the solution and aging stages, thereby improving the low-temperature strength to a certain extent. However, when Nb>0.08wt.%, it is found through research that, due to the strong segregation ability of the Nb element, excessive Nb will lead to the precipitation of large-size primary MX phase, the MX phase is a hard and brittle phase, which is prone to produce incoordination deformation with the matrix during the reducing treatment process, thereby producing micropores and reducing the low-temperature toughness and plasticity of the pipe material. Therefore, in order to ensure the toughness and plasticity of the stainless steel pipe material after reducing and aging treatment, the Nb content is strictly controlled.

[0034] 2. The pipe material must be subjected to aging treatment during the pipe material preparation process. It is found through research that, due to the introduction of a large number of dislocations into the material matrix during the reducing deformation process before aging, the strain-induced precipitation phenomenon during the aging process is accelerated, which leads to the precipitation of a large number of precipitates at dislocations or grain boundaries, thereby reducing the low-temperature toughness and plasticity of the material. In order to inhibit the precipitation of harmful phases (such as intergranular carbonitride), a trace amount of B element is added to the present application.

[0035] 3. The stainless steel of the present application has a high nitrogen content, and in the production process, the method of adding nitride and filling nitrogen gas at rated pressure is adopted to jointly improve the alloying degree of nitrogen element. At the same time, the relative proportion of the nitride content and the nitrogen partial pressure is controlled to ensure that the nitrogen content of the stainless steel is not less than 0.25wt%, thereby ensuring that nitrogen has sufficient solid solution strengthening effect at low temperature.

[0036] 4、Only through the precipitation hardening and solid solution strengthening of nitrogen element can not meet the strength requirements of the armor material, therefore the pipe material is subjected to a reducing treatment in the application, and it is found through research that the application steel suitable for reducing treatment should satisfy 0.01≤Nb≤0.08wt%, after the reducing treatment, under the condition of ultra-low temperature of-269℃, the yield strength is ≥1500MPa, the tensile strength is ≥1800MPa, and the elongation is ≥25%, and the fracture toughness is >130MPa·m 1 / 2 Performance. DETAILED DESCRIPTION

[0037] The experimental methods not specified in the following examples of the application are generally carried out under conventional conditions, or under the conditions recommended by the manufacturers. The various common chemical reagents used in the examples are commercially available products.

[0038] Unless otherwise defined, all technical and scientific terms used in the application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0039] The terms "comprising" and "having" and any variations thereof in the present application are intended to cover the non-exclusive inclusion of the elements specified. For example, a process, method, device, product or apparatus that comprises a list of steps or modules is not limited to the listed steps or modules, but can optionally further include other steps or modules not listed, or can optionally further include other steps inherent to such processes, methods, products or apparatus.

[0040] In the present application, "a plurality of" refers to two or more. "And / or", which describes the association relationship of associated objects, means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The character " / " generally represents that the associated objects before and after it are in an "or" relationship.

[0041] The present application provides a production process of stainless steel suitable for reducing treatment, which comprises the following steps (1)-(9):

[0042] (1) batching: adding pure iron, molybdenum-containing material, vanadium-containing material, niobium-containing material, silicon-containing material, nickel-containing material and chromium-containing material in a certain proportion according to the composition of stainless steel in a smelting furnace; the pure iron in the application is high-purity iron (the iron content is more than 99.99%), the molybdenum-containing material is metallic molybdenum or molybdenum-iron alloy; the vanadium-containing material is metallic vanadium or vanadium-iron alloy, the niobium-containing material is niobium-iron alloy, the silicon-containing material is industrial silicon, the nickel-containing material is metallic nickel, and the chromium-containing material is metallic chromium;

[0043] (2) vacuumizing treatment: vacuumizing treatment is performed on the smelting furnace; the smelting furnace is a vacuum smelting furnace; in this step, the vacuumizing treatment is performed until the pressure in the furnace is below 60 Pa;

[0044] (3) smelting: the smelting furnace is powered on, and the smelting furnace is controlled to start heating and melting the above-mentioned materials until the materials are completely melted;

[0045] (4) heating: after the materials are completely melted, the power of the smelting furnace is controlled to ensure that the temperature of the smelting furnace is 1500℃±20℃;

[0046] (5) filling nitrogen: nitrogen is filled to make the pressure of the smelting furnace reach 0.02-0.1 MPa;

[0047] (6) adding manganese element: manganese-containing materials are added into the molten steel; the manganese-containing materials in this step are metallic manganese;

[0048] (7) adding nitride: after the manganese-containing materials are completely melted, Cr2N is added in batches; the number of batches is calculated according to the total amount of Cr2N to be added, and the amount of Cr2N added each time is not more than 30% of the total amount; after each addition, the Cr2N needs to be stirred uniformly;

[0049] (8) adding boron element: after all the added Cr2N is completely melted, continue to stir for 2-5 minutes until no bubbles come out from the molten steel surface, then add less than 0.03% of pure Al or nickel-magnesium alloy based on the total weight of the molten steel for deoxidation, maintain the power for about 30s-1min, and then add boron-containing materials; the boron-containing materials in this step can be ferroboron;

[0050] (9) casting: after the boron-containing materials are melted, casting is performed to obtain the stainless steel. In this step, it is preferred that the casting is performed 5-20s after the boron-containing materials are added, and the casting temperature is about 1500℃.

[0051] Preferably, in step (1), the amount of niobium element added is less than 0.10wt.%, preferably 0.03wt.% to 0.08wt.%; in step (8), the amount of B element is calculated according to 1.5 to 2 times the target composition boron content.

[0052] Further, in step (7), the amount of Cr2N is calculated according to a nitrogen element yield of 50-70%.

[0053] Preferably, in step (2), the vacuum degree of the smelting furnace after vacuum treatment is above 60 Pa.

[0054] The application also provides a stainless steel prepared by the above process, wherein the component ratio of the stainless steel is as follows, in terms of mass percentage:

[0055] C < 0.015%, Cr 18 ~ 25%, Ni 10 ~ 15%, Mn 1 ~ 10%, Mo 1 ~ 3%, Si < 1.0%, N 0.25 ~ 0.45%, Nb 0.01 ~ 0.08%, V 0.1 ~ 0.3%, S < 0.008%, P < 0.02%, B 0.0010 ~ 0.0050%, and Fe as the balance.

[0056] The application also provides a processing technology of the superconducting coil armoured tube, which is processed by the above-mentioned stainless steel and comprises the following steps (A) to (F):

[0057] (A) electroslag remelting: electroslag remelting treatment is performed on the stainless steel ingot to obtain an electroslag ingot;

[0058] (B) forging: the electroslag ingot is forged into a forged rod;

[0059] (C) hot extrusion: the forged rod is subjected to hot extrusion to shape it into a corresponding tube;

[0060] (D) cold drawing or cold rolling treatment: the hot extruded tube is subjected to cold drawing or cold rolling treatment to obtain a corresponding tube;

[0061] (E) solid solution treatment: the tube is subjected to solid solution treatment; the temperature of the solid solution treatment is 1020°C to 1150°C;

[0062] (F) reducing treatment: the tube after the solid solution treatment is subjected to cold deformation treatment to obtain a reduced tube;

[0063] (G) aging treatment: the reduced tube is subjected to aging treatment.

[0064] Preferably, the reducing treatment in step (F) reduces the inner hole diameter of the tube by 1.5 to 5 mm and increases the length by 2% to 8%.

[0065] Example 1:

[0066] The present example is applicable to the predetermined stainless steel composition for the reducing treatment as shown in Table 1.

[0067] The production technology of the stainless steel applicable to the reducing treatment comprises the following steps:

[0068] (1) batching: a certain proportion of ultra-low carbon pure iron, molybdenum iron alloy, metallic vanadium iron alloy, metallic niobium iron alloy, industrial silicon, metallic nickel and metallic chromium are added into a crucible; the crucible is placed into a vacuum melting furnace; the addition amount of each raw material is calculated according to the predetermined stainless steel composition.

[0069] (2) vacuumizing treatment: vacuumizing treatment is performed on the melting furnace; in the present step, the vacuumizing treatment is performed to a pressure of below 60 Pa;

[0070] (3) Melting: the melting furnace is powered on, and the melting furnace is controlled to start heating and melting the above materials until the materials are completely melted;

[0071] (4) Temperature rising: after the materials are completely melted, the power of the melting furnace is controlled to ensure that the temperature of the melting furnace is 1500°C ± 20°C;

[0072] (5) Nitrogen filling: nitrogen is filled to make the pressure of the melting furnace reach 0.04 MPa;

[0073] (6) Manganese addition: 5% of the weight of the molten steel is added with metallic manganese;

[0074] (7) Nitride addition: after the metallic manganese is completely melted, a certain amount of Cr2N is added in batches. The total amount of Cr2N added is calculated according to the given nitrogen content in the product, and the nitrogen yield is calculated as 60%. (The calculation method of the following examples is the same.) The amount of each batch is calculated according to the amount of Cr2N added, and the amount of each batch is 25% of the total Cr2N. Each time after adding, it needs to be stirred uniformly;

[0075] (8) Boron iron alloy addition: after all the added Cr2N is completely melted, continue to stir for 2-5 minutes until no bubbles come out from the molten steel surface, then add 0.02% of the weight of the molten steel with pure Al for deoxidation, keep the power for about 30s-1min, then add 0.0055% of the weight of the molten steel with boron iron alloy (calculated according to the boron in the boron iron alloy);

[0076] (9) Casting: after the boron iron alloy is melted, stir for 15s and then cast. The casting temperature is about 1500°C.

[0077] Example 2:

[0078] This example is suitable for predetermined stainless steel for reducing diameter treatment, and the composition is as shown in Table 1.

[0079] This example is suitable for the production process of stainless steel for reducing diameter treatment, which includes the following steps:

[0080] (1) Material preparation: the calculated ultra-low carbon pure iron, molybdenum iron alloy, vanadium iron alloy, niobium iron alloy, industrial silicon, metallic nickel, and metallic chromium are added in the crucible; the crucible is placed in a vacuum melting furnace;

[0081] The amount of each raw material is calculated according to the composition of the predetermined stainless steel.

[0082] (2) Vacuum treatment: the melting furnace is subjected to vacuum treatment; in this step, the vacuum treatment is performed until the pressure is below 60 Pa;

[0083] (3) Melting: the melting furnace is powered on, and the melting furnace is controlled to start heating and melting the above materials until the materials are completely melted;

[0084] (4) Temperature rising: after the material is completely melted, the power of the smelting furnace is controlled to ensure that the temperature of the smelting furnace is 1500℃±20℃;

[0085] (5) Nitrogen pressure charging: nitrogen is charged to make the pressure of the smelting furnace reach 0.06MPa;

[0086] (6) Manganese addition: 5.5% of the weight of the molten steel is added with metallic manganese;

[0087] (7) Nitride addition: after the metallic manganese is completely melted, a certain amount of Cr2N is added in batches;

[0088] The amount of each batch is calculated according to the total amount of Cr2N, and the amount of each batch is 30% of the total amount of Cr2N; after each addition, the material is stirred uniformly,

[0089] (8) Boron addition: after all the added Cr2N is completely melted, continue to stir for 2-5 minutes until no bubbles are generated on the surface of the molten steel, then add 0.02% of the weight of the molten steel with Al for deoxidation, keep the power for about 30s-1min, and then add 0.0025% of the weight of the molten steel with ferroboron alloy (calculated according to the boron in the ferroboron alloy);

[0090] (9) Casting: after the ferroboron alloy is melted, stir for 10-20s for casting, and the casting temperature is about 1500℃.

[0091] Example 3:

[0092] The present embodiment is suitable for predetermined stainless steel components for reducing diameter treatment as shown in Table 1.

[0093] The production process of the stainless steel suitable for reducing diameter treatment comprises the following steps:

[0094] (1) Material preparation: a certain proportion of ultra-low carbon pure iron, molybdenum-iron alloy, vanadium-iron alloy, niobium-iron alloy, industrial silicon, metallic nickel and metallic chromium are added in a crucible; the crucible is placed in a vacuum smelting furnace;

[0095] The amount of each raw material is calculated according to the predetermined stainless steel components.

[0096] (2) Vacuum treatment: the smelting furnace is subjected to vacuum treatment; in this step, the vacuum treatment is performed until the pressure is below 60Pa;

[0097] (3) Melting: the smelting furnace is powered on, and the smelting furnace is controlled to start rising temperature and melting the above-mentioned materials until the materials are completely melted;

[0098] (4) Temperature rising: after the material is completely melted, the power of the smelting furnace is controlled to ensure that the temperature of the smelting furnace is 1500℃±20℃;

[0099] (5) nitrogen partial pressure charging: nitrogen is charged to make the pressure of the smelting furnace reach 0.06 MPa;

[0100] (6) manganese element addition: 6% of the weight of the molten steel is added with metallic manganese;

[0101] (7) nitride addition: after the metallic manganese is completely melted, a certain amount of Cr2N is added in batches;

[0102] The amount of each batch is calculated according to the amount of addition, and the amount of each addition is 25% of the total weight of Cr2N; each addition needs to be stirred uniformly;

[0103] (8) boron iron alloy addition: after all the added Cr2N is completely melted, continue to stir for 2-5 minutes until no bubbles come out from the molten steel surface, then add 0.025% of the weight of the molten steel with pure Al for deoxidation, and then add 0.008% of the weight of the molten steel with boron iron alloy (calculated according to the boron in the boron iron alloy) after maintaining the power for about 30 s-1 min;

[0104] (9) casting: after the metallic boron is melted, stir for 15 s and then cast, and the casting temperature is about 1500°C.

[0105] Example 4:

[0106] This embodiment is suitable for the predetermined stainless steel composition for diameter reduction treatment as shown in Table 1.

[0107] The production process of the stainless steel suitable for diameter reduction treatment comprises the following steps:

[0108] (10) batching: a certain proportion of ultra-low carbon pure iron, molybdenum iron alloy, vanadium iron alloy, niobium iron alloy, industrial silicon, metallic nickel and metallic chromium are added in a crucible; the crucible is placed in a vacuum smelting furnace;

[0109] The amount of each raw material is calculated according to the predetermined stainless steel composition.

[0110] (11) vacuum treatment: the smelting furnace is subjected to vacuum treatment; in this step, the vacuum treatment is performed until the pressure is below 60 Pa;

[0111] (12) smelting: the smelting furnace is powered on, and the smelting furnace is controlled to start heating and melting the above-mentioned materials until the materials are completely melted;

[0112] (13) temperature rising: after the materials are completely melted, the power of the smelting furnace is controlled to ensure that the temperature of the smelting furnace is 1500°C±20°C;

[0113] (14) nitrogen partial pressure charging: nitrogen is charged to make the pressure of the smelting furnace reach 0.03 MPa;

[0114] (15) manganese element addition: 5.5% of the weight of the molten steel is added with metallic manganese;

[0115] (16) Adding nitride: after the complete melting of the metal manganese, a certain amount of Cr2N is added in batches;

[0116] The amount of each batch is calculated according to the total amount of Cr2N, and the amount of each batch is 20% of the total weight of Cr2N; each batch needs to be stirred uniformly;

[0117] (17) Adding ferroboron: after the complete melting of all the added Cr2N, continue to stir for 2-5 minutes until no bubbles are emitted from the liquid surface of the steel liquid, then add 0.020% pure Al based on the weight of the steel liquid for deoxidation, maintain the power for about 30s-1min, and then add 0.0060% ferroboron based on the weight of the steel liquid (calculated according to the boron in ferroboron);

[0118] (18) Pouring: after the melting of the metal boron, stirring for 18s, and then pouring, the pouring temperature is about 1500°C.

[0119] Example 5:

[0120] This embodiment is suitable for the predetermined stainless steel composition for reducing diameter treatment as shown in Table 1.

[0121] The production process of the stainless steel suitable for reducing diameter treatment comprises the following steps:

[0122] (19) Blending: a certain proportion of ultra-low carbon pure iron, molybdenum iron alloy, vanadium iron alloy, niobium iron alloy, industrial silicon, metal nickel, and metal chromium are added in the crucible; the crucible is placed in a vacuum melting furnace;

[0123] The amount of each raw material is calculated according to the predetermined stainless steel composition.

[0124] (20) Vacuum treatment: vacuum treatment is performed on the melting furnace; in this step, the vacuum treatment is performed until the pressure is below 60Pa;

[0125] (21) Melting: the melting furnace is powered on, and the melting furnace is controlled to start heating and melting the above-mentioned materials until the materials are completely melted;

[0126] (22) Heating: after the materials are completely melted, the power of the melting furnace is controlled to ensure that the temperature of the melting furnace is 1500°C±20°C;

[0127] (23) Nitrogen partial pressure charging: nitrogen is charged to make the pressure of the melting furnace reach 0.08Mpa;

[0128] (24) Adding manganese element: adding 6.5% metal manganese based on the weight of the steel liquid;

[0129] (25) Adding nitride: after the complete melting of the metal manganese, a certain amount of Cr2N is added in batches;

[0130] The batch added is calculated according to the added amount, and the amount added each time is 25% of the total weight of Cr2N; uniform stirring is required after each addition;

[0131] (26) Adding boron-iron alloy: after all the added Cr2N is completely melted, continue stirring for 2-5 minutes until no bubbles are emitted from the liquid surface of the molten steel, then add 0.030% pure Al accounting for the weight of the molten steel for deoxidation, and then add 0.0040% boron-iron alloy accounting for the weight of the molten steel after maintaining the power for about 30s-1min

[0132] (calculated according to boron in boron-iron alloy);

[0133] (27) Casting: after the metallic boron is melted, stirring for 20s, then casting is carried out, and the casting temperature is about 1500°C.

[0134] Comparative Examples 1-3:

[0135] Comparative Examples 1-3 are only different in composition from Example 1, and other preparation processes are the same.

[0136] The content of each component (wt.%) in the stainless steel obtained in Example 1-5 and Comparative Examples 1-3 is shown in Table 1:

[0137] Table 1

[0138]

[0139] The superconducting coil is a main component of the fusion experimental reactor, and provides a high magnetic field environment of about 15T for the normal operation of the fusion experimental reactor. However, in the high magnetic field environment, a low-temperature austenitic structure steel with no magnetism and high strength and toughness must be used to ensure the safety and stability of the equipment. The traditional ITER 316LN austenitic stainless steel has low low-temperature strength and cannot meet the requirements, and the Fe-Cr-Mn-N austenitic stainless steel is difficult to obtain excellent toughness and plasticity matching after being processed by a sheath pipe material reducing and heat aging.

[0140] The stainless steel prepared in Example 1-5 and Comparative Examples 1-3 is further processed into a superconducting coil sheath pipe material, and the processing process of the superconducting coil sheath pipe material includes the following steps (A)-(F):

[0141] (A) Electroslag remelting: electroslag remelting treatment is performed on the stainless steel ingot to obtain an electroslag ingot;

[0142] (B) Forging: the electroslag ingot is forged into a Φ217mm forged rod;

[0143] (C) Hot extrusion: the forged rod is hot extruded to be shaped into a corresponding pipe material, and in this embodiment, the hot extrusion is shaped into an outer square and inner circle pipe with a specification of 52mm×52mm×Φ40mm;

[0144] (D) cold-drawing or cold-rolling treatment: the hot-extruded pipe is subjected to cold-drawing or cold-rolling treatment to obtain a corresponding pipe, and in this embodiment, the cold-rolling treatment is used to obtain an outer square and inner round pipe with a specification of 40mmx40mmxΦ34mm;

[0145] (E) solid solution treatment: the pipe is subjected to solid solution treatment, and the temperature of the solid solution treatment is 1065℃;

[0146] (F) reducing-diameter treatment: the pipe subjected to the solid solution treatment is subjected to reducing-diameter treatment, and in this embodiment, the reducing-diameter treatment is used to reduce the inner hole diameter of the pipe by 1.5-5mm and increase the length by 2%-8%.

[0147] (G) aging treatment: the pipe subjected to the reducing-diameter treatment is subjected to aging treatment at 650℃ for 200h.

[0148] The performance test results of the pipes obtained after the reducing-diameter and aging treatment of the stainless steels in Table 1 are shown in Table 2 below:

[0149] Table 2: Performance of pipes obtained after reducing-diameter and aging treatment of the stainless steels in the examples and the comparative examples at-269℃

[0150]

[0151] After the reducing-diameter and aging treatment of the stainless steels (Examples 1-3) of the present application, the performance of the pipes can reach a yield strength of ≥1500MPa, a tensile strength of ≥1800MPa, and an elongation of ≥25% at-269℃, and the fracture toughness at-269℃ is >130MPa·m 1 / 2 .

[0152] The technical features of the above-described embodiments can be combined in any manner, and for the sake of brevity, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not contradict each other, they should be considered as within the scope of the present disclosure.

[0153] The above-described embodiments only express several embodiments of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the present patent. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these are within the scope of the present application. Therefore, the scope of protection of the present patent should be subject to the appended claims.

Claims

1. A production process of a stainless steel suitable for a reducing process, characterized in that: the chemical composition of the stainless steel is as follows in terms of mass percentage: C < 0.015%, Cr 18-25%, Ni 10-15%, Mn 1-10%, Mo 1-3%, Si < 1.0%, N 0.25-0.45%, Nb 0.01-0.08%, V 0.1-0.3%, S < 0.008%, P < 0.02%, B 0.0010-0.0050%, and Fe is the balance; and the production process of the stainless steel comprises the following steps (1)-(9): (1) adding pure iron, molybdenum-containing material, vanadium-containing material, niobium-containing material, silicon-containing material, nickel-containing material, and chromium-containing material in a corresponding proportion according to the composition of the stainless steel in a smelting furnace; (2) performing vacuumizing treatment on the smelting furnace; (3) heating until the materials in the furnace are completely melted to obtain a molten steel; (4) controlling the temperature of the smelting furnace to be 1500℃±20℃ after complete melting; (5) filling nitrogen gas to make the pressure of the smelting furnace reach 0.02-0.1 MPa; (6) adding manganese-containing material to the molten steel; (7) after the manganese-containing material is completely melted, adding Cr2N in batches; (8) after the Cr2N is completely melted and no bubbles are emitted from the molten steel surface, adding boron-containing material; specifically, after all the added Cr2N is completely melted, continuing to stir for 2-5 minutes until no bubbles are emitted from the molten steel surface, then adding less than 0.03% of pure Al or nickel-magnesium alloy based on the total weight of the molten steel for deoxidization, the amount of pure Al or nickel-magnesium alloy is not 0, and after maintaining the power for 30s-1min, adding the boron-containing material; and (9) after the boron-containing material is melted, performing casting to obtain the stainless steel. In step (7), the amount of Cr2N is calculated according to the nitrogen yield of the stainless steel being 50-70%. In step (2), the vacuumizing treatment is performed until the pressure in the furnace is below 60 Pa. In step (8), after the boron-containing material is melted, stirring for 10-60s can be performed before casting.

5. A stainless steel suitable for a reducing process, which is produced by the process of any one of claims 1-4. The superconducting coil armoring pipe is processed from the stainless steel. The processing process of the superconducting coil armoring pipe comprises the following steps (A)-(F): (A) electroslag remelting: performing electroslag remelting treatment on the stainless steel ingot to obtain an electroslag ingot; (B) forging: forging the electroslag ingot into a forged bar; (C) hot extrusion: hot extruding the forged bar to shape it into a corresponding pipe; (D) cold drawing or cold rolling treatment: performing cold drawing or cold rolling treatment on the pipe obtained after hot extrusion to obtain a corresponding pipe; (E) solid solution treatment: performing solid solution treatment on the pipe; the temperature of the solid solution treatment is 1020℃-1150℃; (F) reducing process: performing cold deformation treatment on the pipe after the solid solution treatment to obtain a reduced pipe; 2. The production process of stainless steel suitable for undergauge treatment according to claim 1, characterized in that: (G) aging treatment: performing aging treatment on the reduced pipe.

3. The production process of stainless steel suitable for undergauge treatment according to claim 1, characterized in that: In step (F), the reducing process makes the inner hole diameter of the pipe decrease by 1.5-5mm, and the length of the pipe increases by 2-8%.

4. The production process of stainless steel suitable for undergauge treatment according to claim 1, characterized in that: ​ ​ 6. A superconducting coil armoured tube fabricated using the stainless steel of claim 5, characterised in that: ​ 7. The superconducting coil can armor tube of claim 6, wherein: ​ ​ ​ ​ ​ ​ ​ ​ 8. The superconducting coil can armor tube of claim 7, wherein: ​ 9. The superconducting coil can armor tube of claim 7, wherein: The said armoured pipe material is stretched at -269°C, with a yield strength of ≥ 1500 MPa, a tensile strength of ≥ 1800 MPa, and an elongation of ≥ 25%; and a fracture toughness at -269°C of > 130 MPa.m 1 / 2 .

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