High-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor and manufacturing method therefor

Abstract

A high-strength non-magnetic austenitic stainless steel bar suitable for a nuclear fusion armor and a manufacturing method therefor. High-temperature δ-ferrite and M23C6 are eliminated from the high-strength non-magnetic austenitic stainless steel bar, and therefore the steel bar achieves a good match between strength and toughness at a low temperature, and also has good resistance to intercrystalline corrosion. At a liquid helium temperature of 4.2 K, the high-strength non-magnetic austenitic stainless steel bar has a yield strength greater than or equal to 1250 MPa, a tensile strength greater than or equal to 1700 MPa, an elongation greater than or equal to 25%, and a magnetic conductivity smaller than or equal to 1.02. The high-strength non-magnetic austenitic stainless steel bar can be directly used in a structural member such as a conductor armor in a fusion reactor and other nuclear reaction devices, and can also be promoted and used in other related fields such as high-strength stainless parts required in cryogenic engineering.

Description

A high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor and its manufacturing method Technical Field

[0001] The present application relates to the technical field of high-strength stainless steel, and in particular to a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor and a manufacturing method thereof. Background Art

[0002] The engineering design of my country's large-scale superconducting fusion experimental device has significantly increased the magnetic field strength and current of the magnet system, increasing the electromagnetic load borne by its superconducting magnets by 60% compared to the International Thermonuclear Experimental Reactor (ITER) device. The superconducting magnet armor is a barrier to the safe operation of the superconducting magnets and the primary carrier of the superconducting magnets' resistance to periodic electromagnetic stress shocks exceeding hundreds of tons at liquid helium temperatures (4.2K). The ultra-low temperature structural materials used in the superconducting magnet armor have a yield strength of 1250 MPa at 4.2K, a tensile strength of 1700 MPa, and an elongation of 25%. Currently, the ultra-low temperature structural materials used in the ITER device cannot meet the load-bearing requirements of my country's fusion engineering test reactor. It is worth noting that the superconducting magnet armor in a nuclear fusion device not only needs to provide structural support but also serves as a protective shield for superconducting materials such as Nb3Sn, making it a core component of the nuclear fusion device. The superconducting magnet armor components used in nuclear fusion devices require tubing fabricated from cryogenic structural raw materials to support and protect the core superconducting material. This tubing also requires a 600-hour aging treatment at 250°C for the superconducting material. This places extremely stringent demands on the stability of the superconducting magnet armor components' structure and performance. Therefore, the development of a high-strength, non-magnetic austenitic stainless steel with excellent ultra-low-temperature strength and ductility for use in superconducting magnet armor components is urgent.

[0003] Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor and a manufacturing method thereof. The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in this application has excellent ultra-low temperature plasticity.

[0005] In order to achieve the above-mentioned invention objectives, this application provides the following technical solutions:

[0006] The present application provides a high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, comprising the following elements in percentage by mass:

[0007] C: ≤0.01%, N: 0.26~0.40%, O: ≤0.0020%, H: ≤0.0006%, P: ≤0.006%, S: ≤0.005%, Cr: 20.5~22.5%, Ni: 14.0~15.5%, Mo: 1.8~2.2%, Mn: 5.0~6.0%, Si: ≤0.20%, Nb: 0.04~0.16%, V: 0.10~0.20%, Cu: 0.08~0.18%, Al≤0.02%, the balance is Fe and unavoidable impurities;

[0008] Control Ni eq / Cr eq ≥1.1.

[0009] The present application also provides a method for manufacturing the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor as described in the above technical solution, comprising the following steps:

[0010] Weigh the raw materials, smelt and forge them in sequence to obtain bars;

[0011] The rod is subjected to a solid solution treatment to obtain the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor.

[0012] Preferably, the smelting comprises sequentially performing medium frequency induction smelting and electroslag remelting;

[0013] The deoxidizer of the medium frequency induction smelting includes Ca-Si, Ni-Mg alloy and Ce, and the temperature of the medium frequency induction smelting is 1510±10°C and the time is ≥40min;

[0014] The slag system of the electroslag remelting is a CaF2-Al2O3-CaO-MgO quaternary slag system, and the electroslag remelting is carried out under a protective atmosphere, which is dry air.

[0015] Preferably, the forging parameters include: high-temperature diffusion temperature before forging is 1180-1230°C, blanking forging temperature is 1050-1100°C, and final forging temperature is 850-900°C.

[0016] Preferably, the temperature of the solution treatment is 1120°C ± 60°C, and the time is 1 to 2 hours.

[0017] Preferably, after the solution treatment, water quenching to room temperature is also included.

[0018] The present application provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, comprising the following elements by mass percentage: C: ≤0.01%, N: 0.26-0.40%, O: ≤0.0020%, H: ≤0.0006%, P: ≤0.006%, S: ≤0.005%, Cr: 20.5-22.5%, Ni: 14.0-15.5%, Mo: 1.8-2.2%, Mn: 5.0-6.0%, Si: ≤0.20%, Nb: 0.04-0.16%, V: 0.10-0.20%, Cu: 0.08-0.18%, Al≤0.02%, and the balance being Fe and unavoidable impurities; controlling Ni eq / Cr eq ≥1.1. The high strength non-magnetic austenitic stainless steel bar of this application eliminates the high temperature δ-ferrite and M 23 C6, giving it excellent strength-toughness matching and intergranular corrosion resistance at low temperatures. The high-strength, non-magnetic austenitic stainless steel bar of this application has a yield strength of ≥1250MPa, a tensile strength of ≥1700MPa, an elongation of ≥25%, and a magnetic permeability of ≤1.02 at 4.2K liquid helium temperature. The high-strength, non-magnetic austenitic stainless steel bar of this application is austenitic, non-magnetic, high-strength stainless steel and can be directly used in structural components such as conductor armor in nuclear reactors such as fusion reactors. It can also be extended to other related fields such as high-strength stainless steel components required in cryogenic engineering, and has broad market prospects.

[0019] This application also provides a method for manufacturing the high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, as described in the above technical solution. The method comprises the following steps: weighing raw materials, smelting and forging them sequentially to obtain a bar; and solution treating the bar to obtain the high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor. The manufacturing method provided in this application is simple to operate and amenable to industrialization.

[0020] Furthermore, the smelting includes sequentially performing medium frequency induction smelting and electroslag remelting; and can accurately control ultra-low carbon (≤0.01%), ultra-low oxygen (≤0.0020%) and nitrogen content (0.26-0.40%). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a photograph of the forged rod and the solution-treated high-strength, non-magnetic austenitic stainless steel rod suitable for use in nuclear fusion armor in Example 1. The left image is a photograph of the forged rod, and the right image is a photograph of the solution-treated high-strength, non-magnetic austenitic stainless steel rod suitable for use in nuclear fusion armor.

[0022] FIG2 is a photograph of the grain size of a high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 2;

[0023] FIG3 is a fracture microstructure characterization diagram of a tensile specimen of a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 3;

[0024] FIG4 is the EBSD microstructure morphology of the tensile specimen of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 3. DETAILED DESCRIPTION

[0025] The present application provides a high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, comprising the following elements in percentage by mass:

[0026] C: ≤0.01%, N: 0.26~0.40%, O: ≤0.0020%, H: ≤0.0006%, P: ≤0.006%, S: ≤0.005%, Cr: 20.5~22.5%, Ni: 14.0~15.5%, Mo: 1.8~2.2%, Mn: 5.0~6.0%, Si: ≤0.20%, Nb: 0.04~0.16%, V: 0.10~0.20%, Cu: 0.08~0.18%, Al≤0.02%, the balance is Fe and unavoidable impurities;

[0027] Control Ni eq / Cr eq ≥1.1.

[0028] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in this application contains ≤0.01% carbon by mass. Carbon is an element that strongly forms and stabilizes austenite in stainless steel and expands the austenite region. It is also a material strengthening element, but while increasing strength, it also impairs the plasticity, toughness, and weldability of the steel. In addition, the presence of carbon in the steel causes the matrix to precipitate M during long-term aging at 650°C. 23 C6 carbides seriously deteriorate the low-temperature plasticity and corrosion resistance of steel, so the carbon content in the steel of this application needs to be controlled to be ultra-low. Taking all factors into consideration, the carbon content of the steel of this application is controlled within 0.01%.

[0029] The high-strength, non-magnetic austenitic stainless steel bar material suitable for nuclear fusion armor provided in this application includes 0.26% to 0.40% nitrogen by weight. Nitrogen has a similar effect to carbon, and nitriding using interstitial solid solution can significantly increase strength. However, for austenitic stainless steel, the advantage of using nitrogen atoms for interstitial solid solution strengthening is that it improves strength while not significantly affecting plasticity and toughness, and ensures that the matrix is ​​non-magnetic. Therefore, nitrogen atoms are used for solid solution strengthening in this application, with a nitrogen content of 0.26% to 0.40% by weight.

[0030] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in the present application includes oxygen with a mass percentage of ≤0.0020%.

[0031] The high-strength, non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor provided in this application include hydrogen with a mass percentage of ≤0.0006%. Dissolved oxygen in steel will exist in the form of various inclusions, which will seriously reduce the plasticity, toughness, fatigue properties, and hot and cold processing properties of the steel. Hydrogen will cause hydrogen embrittlement and white spots in the steel, seriously reducing the toughness of the steel. Taking the above into consideration, this application controls the mass percentages of oxygen and hydrogen to within 0.0020% (20ppm) and 0.0006% (6ppm), respectively.

[0032] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in the present application includes phosphorus with a mass percentage of ≤0.006%.

[0033] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in this application contains ≤0.005% sulfur by weight. Impurities such as phosphorus and sulfur in steel significantly reduce its plasticity, toughness, and weldability. Because this steel is smelted using a dual ultra-pure smelting process using a medium-frequency furnace and electroslag remelting process, along with pure metal materials, the phosphorus and sulfur content is controlled within 0.006% and 0.005% by weight, respectively.

[0034] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application includes 20.5-22.5% by mass of chromium. Chromium is an important alloying element for the corrosion resistance of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application. As the chromium content increases, the intergranular corrosion resistance is significantly improved. At the same time, the presence of chromium can also improve the tempering resistance to maintain the dislocation strengthening and solid solution strengthening effects. However, increasing the chromium content will promote the M 23 The formation of C6 and high-temperature Cr2N will seriously deteriorate the low-temperature toughness and high-temperature forgeability of the steel. Therefore, the mass percentage of chromium is controlled within the range of 20.5-22.5% in this application.

[0035] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in this application includes 14.0-15.5% nickel by weight. Nickel, as one of the most important alloying elements for austenite formation, can expand the austenite phase region while inhibiting the formation of high-temperature delta ferrite. In addition, nickel can improve the low-temperature performance of nickel-chromium-based austenitic stainless steel, and the low-temperature toughness is significantly improved with the increase of nickel. Taking all factors into consideration, this application controls the nickel content by weight to be within the range of 14.0-15.5%.

[0036] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in the present application includes 1.8 to 2.2% by mass of molybdenum. Molybdenum can improve the strength through solid solution strengthening and the formation of Laves phase precipitation strengthening, and can significantly improve the hardenability of steel and improve the corrosion resistance of steel. In addition, molybdenum can also form M2C type carbides with a hexagonal crystal structure during the aging process, thereby improving the tempering stability and secondary hardening effect of steel. However, too high a molybdenum content will promote the formation of ferrite, resulting in magnetic loss in fusion reactors. Taking all factors into consideration, the mass percentage of molybdenum controlled in the present application is 1.8 to 2.2%.

[0037] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by this application includes 5.0-6.0% manganese by mass. Manganese is also an austenite-forming element. At the same time, manganese can reduce the critical cooling rate during quenching, thereby improving the hardenability and thermoplasticity of steel more effectively than any other alloying element. In addition, manganese is also a deoxidizer and desulfurizer. Under low-carbon composition, it can reduce the oxygen content and combine with sulfur to form manganese sulfide, eliminating the harmful effects of residual sulfur in steel. Taking all factors into consideration, this application controls the mass percentage of manganese to 5.0-6.0%.

[0038] The high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor provided by the present application include silicon with a mass percentage of ≤0.20%. Silicon plays a major role in deoxidation in steel. Since the steel of the present application uses pure metal materials and adopts a dual ultra-pure smelting process of medium-frequency furnace + electroslag remelting, it is not necessary to add too much silicon for deoxidation. In addition, silicon is an element that promotes the formation of ferrite and will seriously damage the low-temperature plasticity and toughness of steel, so it needs to be strictly controlled. Taking all the above into consideration, the mass percentage of silicon in the present application is controlled within 0.20%.

[0039] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by this application includes 0.04-0.16% by mass of niobium. The role of the microalloying element niobium in steel is mainly manifested in inhibiting the deformation and recrystallization of austenite and preventing its grain growth during hot working, and the strain-induced precipitation of Nb(C,N) in steel has the strongest grain refining and strengthening effect. In addition, a small amount of strong carbide-forming element niobium can inhibit the coarse Cr when solution treating austenitic stainless steel. 23 The formation of C6 significantly improves intergranular corrosion. In summary, the mass percentage of niobium in the present application is 0.04-0.16%.

[0040] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in this application includes 0.10-0.20% by mass of vanadium. A small amount of vanadium can refine the structure and grains of the steel, increase the grain coarsening temperature, thereby reducing overheating sensitivity and improving the strength and toughness of the steel. Increasing the vanadium content will promote the precipitation of V (C, N) for strengthening, while at the same time reducing low-temperature toughness, so the content in most steels is not high. Taking all the above into consideration, this application controls the vanadium content by mass to 0.10-0.20%.

[0041] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application includes copper with a mass percentage of 0.08 to 0.18%. The addition of an appropriate amount of copper can generate ε-Cu, thereby improving the strength and yield ratio of the steel, without adversely affecting the welding performance. In addition, as the copper content increases, the strain hardening index will also decrease, reducing the cold work hardening tendency and cold work cracking sensitivity of the nickel-chromium-based austenitic stainless steel, and having a significant beneficial effect on the cold forming performance of the nickel-chromium-based austenitic stainless steel. In addition, the addition of copper can also improve the processing performance and atmospheric corrosion resistance of austenitic stainless steel. Therefore, the mass percentage range of the copper in the present application is controlled to be 0.08 to 0.18%.

[0042] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in this application includes aluminum at a mass percentage of 0.02% or less. During the steelmaking process, aluminum, as a strong deoxidizer, significantly reduces oxygen. Most steels are deoxidized using aluminum or aluminum-containing composite deoxidizers, creating inclusions to control the oxygen content in the molten steel. However, if Al2O3 and AlN inclusions remain in the steel, they can severely reduce low-temperature plasticity and toughness. Therefore, this application strictly controls the aluminum mass percentage to within 0.02%.

[0043] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided in the present application includes the balance of Fe and unavoidable impurities.

[0044] In this application, the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor is controlled by Ni eq / Cr eq ≥1.1, that is, the equivalent ratio of Ni to Cr is ≥1.1. In this application, Ni eq =Ni / %+30×C / %+25×N / %+0.5×Mn / %+Co / %+0.3×Cu / %, wherein Ni / %, C / %, N / %, Mn / %, Co / % and Cu / % represent the mass percentages of Ni, C, N, Mn, Co and Cu in the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, respectively. In this application, Cr eq=Cr / %+1.5×Mo / %+2×Si / %+1.75×Nb / %+1.5×Ti / %+5.5×Al / %+0.75×W / %+5×V / %, wherein Cr / %, Mo / %, Si / %, Nb / %, Ti / %, Al / %, W / % and Cu / % respectively represent the mass percentages of Cr, Mo, Si, Nb, Ti, Al, W and Cu in the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor; specifically in the present application, the mass percentages of Ti and W in the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor are 0.

[0045] The present application also provides a method for manufacturing the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor as described in the above technical solution, comprising the following steps:

[0046] Weigh the raw materials, smelt and forge them in sequence to obtain bars;

[0047] The rod is subjected to a solid solution treatment to obtain the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor.

[0048] In this application, unless otherwise specified, the raw materials used in this application are pre-selected as commercially available products.

[0049] The present application weighs raw materials, performs smelting and forging in sequence to obtain rods.

[0050] In the present application, the raw materials are preferably weighed according to the mass percentage of elements specified in the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor as described in the above technical solution.

[0051] In the present application, the smelting preferably includes sequentially performing medium frequency induction smelting and electroslag remelting.

[0052] In the present application, the deoxidizer for the medium frequency induction smelting preferably includes Ca-Si, Ni-Mg alloy, and Ce. The temperature of the medium frequency induction smelting is preferably 1510±10°C, and the time is preferably ≥40 minutes. In the present application, the medium frequency induction smelting is preferably carried out in a 5t / 10t medium frequency induction furnace. The specific operation of medium frequency induction smelting the raw materials in a 5t / 10t medium frequency induction furnace is not specifically limited in the present application, and those skilled in the art can use familiar technical means.

[0053] In the present application, the slag system used in the electroslag remelting is preferably a quaternary slag system of CaF2-Al2O3-CaO-MgO. In the present application, the electroslag remelting is preferably performed under a protective atmosphere, preferably dry air. In the present application, the raw materials used in the electroslag remelting are preferably medium-frequency electrodes obtained through medium-frequency induction smelting. In the present application, de-ingoting is preferably performed 6-8 hours after the completion of the electroslag remelting; the de-ingoting process is preferably protected by a heat shield.

[0054] In the present application, the forging parameters preferably include: the high-temperature diffusion temperature before forging is preferably 1180-1230°C, the blanking forging temperature is preferably 1050-1100°C, and the final forging temperature is preferably 850-900°C.

[0055] After obtaining the rod, the present application performs a solution treatment on the rod to obtain the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor.

[0056] In the present application, the temperature of the solution treatment is preferably 1120°C ± 60°C, more preferably 1120-1180°C; and the time is preferably 1-2 hours.

[0057] After the solution treatment, the present application preferably further includes water quenching to room temperature.

[0058] In the present application, the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor is preferably used as superconducting magnet armor in a nuclear fusion device.

[0059] The high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor provided by the present application, as well as their manufacturing methods and applications, are described in detail below in conjunction with the embodiments. However, they should not be construed as limiting the scope of protection of the present application.

[0060] According to the elemental composition of high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor shown in Table 1, raw materials were weighed and medium-frequency induction smelting was carried out in a 5t / 10t medium-frequency induction furnace. The parameters of the medium-frequency induction smelting included: Ca-Si, Ni-Mg alloy and Ce deoxidation were used in the alloying stage, refining for 40 minutes, and the final temperature was controlled at 1510±10℃ to obtain medium-frequency electrodes; the medium-frequency electrodes were used as raw materials for electroslag remelting and then electroslag remelting was carried out. The parameters of the electroslag remelting included: Multiple medium frequency electrodes are used for electroslag remelting to produce steel ingots of the required weight. The slag produced by the electroslag remelting is a quaternary slag system of CaF2-Al2O3-CaO-MgO. The electroslag remelting is carried out under a protective atmosphere of dry air. The ingots are removed 6 to 8 hours after the electroslag remelting is completed, during which time they are protected by a heat preservation cover to obtain steel ingots. Medium frequency induction smelting and electroslag remelting achieve precise control of ultra-low carbon (≤0.01%), ultra-low oxygen (≤0.0020%) and nitrogen content (0.26 to 0.40%).

[0061] Table 1 Chemical composition of high-strength non-magnetic austenitic stainless steel bars in the embodiment (wt.%)

[0062] The steel ingots were subjected to the forging temperature control process parameters shown in Table 2 to obtain bars.

[0063] Table 2 Forging temperature control process parameters of the embodiment

[0064] The resulting rods were solution treated according to the conditions shown in Table 3 and then water quenched to room temperature to obtain the final high-strength, non-magnetic austenitic stainless steel rods suitable for nuclear fusion armor. The mechanical property test results of the resulting high-strength, non-magnetic austenitic stainless steel rods suitable for nuclear fusion armor are also listed in Table 3.

[0065] Table 3 Mechanical properties of the examples after different solution treatments

[0066] It can be seen from Table 3 that both Example 2 and Example 3 have the best strength-plasticity matching at 1170-1180°C. Example 2 has a tensile strength of 1829MPa, a yield strength of 1273MPa, an elongation of 34%, and a cross-sectional reduction rate of 49% at a liquid helium temperature of 4.2K; Example 3 has a tensile strength of 1803MPa, a yield strength of 1401MPa, an elongation of 35%, and a cross-sectional reduction rate of 40% at a liquid helium temperature of 4.2K. With the increase of temperature, the strength of the steel of the present application increases and the plasticity decreases. After solid solution at 1200°C, Example 3 will generate a certain amount of high-temperature δ ferrite, which will damage its non-magnetic properties.

[0067] Figure 1 shows photographs of the forged rod and the solution-treated high-strength, non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor in Example 1. The left image shows the forged rod, while the right image shows the solution-treated high-strength, non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor. Figure 1 shows that the rods maintain excellent surface quality during and after forging, with no macroscopic defects such as cracks or microcracks.

[0068] Figure 2 is a grain size photograph of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 2. As can be seen from Figure 2, the grain size of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor is uniform and the size distribution is uniform. The microstructure is an austenite matrix with no M 23 C6 carbide and delta-ferrite.

[0069] Scanning electron microscopy (SEM) was used to characterize the fracture microstructure of the high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained through solution treatment in Example 3 after tensile testing at 4.2K liquid helium. The results are shown in Figure 3. As shown in Figure 3, numerous dimples were present in the cross-section of the specimens after the tensile test, indicating that all specimens exhibited ductile fracture.

[0070] In addition, the electron backscatter diffraction (EBSD) technique was used to characterize the microstructure of the tensile specimen of the high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 3 at 4.2K liquid helium temperature. The results are shown in FIG4 . As can be seen from FIG4 , a large amount of twin structure was generated in the specimen during the low-temperature tensile process, which is why the invented steel has excellent strength and plasticity at ultra-low temperatures.

[0071] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, characterized in that: Includes the following elements in percentage by mass: C: ≤0.01%, N: 0.26~0.40%, O: ≤0.0020%, H: ≤0.0006%, P: ≤0.006%, S: ≤0.005%, Cr: 20.5~22.5%, Ni: 14.0~15.5%, Mo: 1.8~2.2%, Mn: 5.0~6.0%, Si: ≤0.20%, Nb: 0.04~0.16%, V: 0.10~0.20%, Cu: 0.08~0.18%, Al≤0.02%, the balance is Fe and unavoidable impurities; Control Ni eq / Cr eq ≥1.

1.

2. The method for manufacturing high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor according to claim 1, characterized in that: The following steps are involved: Weigh the raw materials, smelt and forge them in sequence to obtain bars; The rod is subjected to a solid solution treatment to obtain the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor.

3. The manufacturing method according to claim 2, characterized in that: The smelting includes sequentially performing medium frequency induction smelting and electroslag remelting; The deoxidizer of the medium frequency induction smelting includes Ca-Si, Ni-Mg alloy and Ce, and the temperature of the medium frequency induction smelting is 1510±10°C and the time is ≥40min; The slag system of the electroslag remelting is a quaternary slag system of CaF2-Al2O3-CaO-MgO, and the electroslag remelting is carried out under a protective atmosphere, which is dry air.

4. The manufacturing method according to claim 2, characterized in that: The forging parameters include: high temperature diffusion temperature before forging is 1180-1230°C, blank forging temperature is 1050-1100°C, and final forging temperature is 850-900°C.

5. The manufacturing method according to claim 2, characterized in that: The temperature of the solution treatment is 1120°C ± 60°C, and the time is 1 to 2 hours.

6. The manufacturing method according to claim 2 or 5, characterized in that: After the solution treatment, the process further includes water quenching to room temperature.

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