High-strength non-magnetic austenitic stainless steel rod for nuclear fusion armors and method for manufacturing the same

Abstract

The application belongs to the technical field of high-strength stainless steel, and provides a high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor and a manufacturing method thereof.The high-strength non-magnetic austenitic stainless steel rod of the application eliminates high-temperature delta-ferrite and M23C6, so that it has excellent matching of strength and toughness and intergranular corrosion resistance at low temperature.The yield strength of the high-strength non-magnetic austenitic stainless steel rod of the application is greater than or equal to 1250 MPa at 4.2K liquid helium temperature, the tensile strength is greater than or equal to 1700 MPa, the elongation is greater than or equal to 25%, and the magnetic permeability is less than or equal to 1.02.The high-strength non-magnetic austenitic stainless steel rod of the application is an austenitic non-magnetic high-strength stainless steel, and can be directly applied to structural parts such as conductor armor of nuclear reactors and the like, and can also be popularly applied to high-strength stainless parts required in low-temperature engineering and other related fields, and has a broad market prospect.

Description

Technical Field

[0001] The present invention 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 ultra-low-temperature structural raw materials to support and protect the core superconducting material. This tubing also requires a 200-hour aging treatment at 650°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. Summary of the Invention

[0003] In view of this, the object of the present invention 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 by the present invention has excellent ultra-low temperature plasticity.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, comprising the following elements in percentage by mass:

[0006] 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;

[0007] Control Ni eq / Cr eq ≥1.1.

[0008] The present invention 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:

[0009] Weigh the raw materials, smelt and forge them in sequence to obtain bars;

[0010] 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.

[0011] Preferably, the smelting comprises sequentially performing medium frequency induction smelting and electroslag remelting;

[0012] 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;

[0013] 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.

[0014] 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.

[0015] Preferably, the temperature of the solution treatment is 1120°C ± 60°C, and the time is 1 to 2 hours.

[0016] Preferably, after the solution treatment, water quenching to room temperature is also included.

[0017] The invention provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, comprising 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%, 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 the present invention 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 the present invention has a yield strength of ≥1250 MPa, a tensile strength of ≥1700 MPa, an elongation of ≥25%, and a magnetic permeability of ≤1.02 at a liquid helium temperature of 4.2K. The high-strength, non-magnetic austenitic stainless steel bar of the present invention 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 widely applied to other related fields such as high-strength stainless steel components required in cryogenic engineering, and has broad market prospects.

[0018] The present invention 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 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 by the present invention is simple to operate and amenable to industrialization.

[0019] 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

[0020] Figure 1 Photos of the forged rods and the solution-treated high-strength, non-magnetic austenitic stainless steel rods suitable for use in nuclear fusion armor in Example 1. The left photo is a photo of the forged rods, and the right photo is a photo of the solution-treated high-strength, non-magnetic austenitic stainless steel rods suitable for use in nuclear fusion armor.

[0021] Figure 2This is a photo of the grain size of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 2;

[0022] Figure 3 This is a microstructure characterization diagram of the tensile specimen fracture surface of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 3;

[0023] Figure 4 This 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

[0024] The present invention provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, comprising the following elements in percentage by mass:

[0025] 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;

[0026] Control Ni eq / Cr eq ≥1.1.

[0027] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention contains ≤0.01% carbon by mass. Carbon is a strong austenite-forming and stabilizing element in stainless steel, expanding the austenite region, and is also a material strengthening element. However, while increasing strength, it also impairs the steel's plasticity, toughness, and weldability. Furthermore, the presence of carbon in the steel can cause 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 the present invention needs to be controlled to be ultra-low. Taking all factors into consideration, the carbon content of the steel of the present invention is controlled within 0.01%.

[0028] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention contains 0.26-0.40% nitrogen by weight. Nitrogen has similar effects to carbon, and interstitial solid solution nitriding can significantly improve 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 compromising ductility and toughness, while also ensuring the non-magnetic nature of the matrix. Therefore, in the present invention, nitrogen atoms are used for solid solution strengthening, with a nitrogen content of 0.26-0.40% by weight.

[0029] The high-strength non-magnetic austenitic stainless steel bar material suitable for nuclear fusion armor provided by the present invention comprises oxygen with a mass percentage of ≤0.0020%.

[0030] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention contains ≤0.0006% hydrogen by mass. Dissolved oxygen in steel can exist as various inclusions, severely reducing the steel's plasticity, toughness, fatigue properties, and hot and cold working properties. Hydrogen can also cause hydrogen embrittlement and white spots in steel, severely reducing its toughness. Taking all of the above into consideration, the present invention controls the oxygen and hydrogen content to within 0.0020% (20 ppm) and 0.0006% (6 ppm), respectively.

[0031] The high-strength non-magnetic austenitic stainless steel bar material suitable for nuclear fusion armor provided by the present invention comprises phosphorus with a mass percentage of ≤0.006%.

[0032] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by this invention contains ≤0.005% sulfur by weight. Impurities such as phosphorus and sulfur in steel significantly reduce its plasticity, toughness, and weldability. Because the steel is smelted using a dual ultra-pure smelting process involving a medium-frequency furnace and electroslag remelting, along with pure metal materials, the phosphorus and sulfur content is controlled within 0.006% and 0.005% by weight, respectively.

[0033] The high-strength, non-magnetic, austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention includes 20.5-22.5% by mass of chromium. Chromium is an important alloying element that provides corrosion resistance to the high-strength, non-magnetic, austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention. As the chromium content increases, the intergranular corrosion resistance is significantly improved. At the same time, the presence of chromium can also improve tempering resistance to maintain dislocation strengthening and solid solution strengthening effects. However, increasing the chromium content will promote 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 present invention controls the mass percentage of chromium to be within the range of 20.5-22.5%.

[0034] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention contains 14.0-15.5% nickel by weight. Nickel, one of the most important alloying elements for austenite formation, can expand the austenitic phase while inhibiting the formation of high-temperature delta ferrite. Furthermore, nickel enhances the low-temperature performance of nickel-chromium-based austenitic stainless steel, significantly improving low-temperature toughness with increasing nickel content. Taking all these factors into consideration, the present invention controls the nickel content by weight to be within the range of 14.0-15.5%.

[0035] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention includes 1.8 to 2.2% by mass of molybdenum. Molybdenum can improve strength through solid solution strengthening and the formation of Laves phase precipitation strengthening, while significantly improving the hardenability of steel and improving 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 the steel. However, an excessively high molybdenum content will promote the formation of ferrite, leading to magnetic loss in the fusion reactor. Taking all factors into consideration, the mass percentage of molybdenum controlled by the present invention is 1.8 to 2.2%.

[0036] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention contains 5.0-6.0% manganese by weight. Manganese is also an austenite-forming element and can reduce the critical cooling rate during quenching, thereby improving the hardenability and thermoplasticity of the steel more effectively than any other alloying element. Furthermore, manganese is a deoxidizer and desulfurizer. In a 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 the steel. Taking all these factors into consideration, the present invention controls the manganese content to 5.0-6.0% by weight.

[0037] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention includes silicon with a mass percentage of ≤0.20%. Silicon plays a major role in deoxidation in steel. Since the steel of the present invention uses pure metal materials and adopts a dual ultra-pure smelting process of medium-frequency furnace + electroslag remelting, it does not need to add too much silicon for deoxidation. In addition, silicon is an element that promotes ferrite formation 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 present invention controls the mass percentage of silicon to within 0.20%.

[0038] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention 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. The strain-induced precipitation of Nb(C,N) through its carbonitrides has the strongest grain refining and strengthening effect in steel. In addition, a small amount of strong carbide-forming element niobium can inhibit the growth of 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 invention is 0.04-0.16%.

[0039] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention contains 0.10-0.20% by weight of vanadium. A small amount of vanadium refines the steel's structure and grain size, raising the grain coarsening temperature, thereby reducing overheating sensitivity and improving the steel's strength and toughness. Increasing the vanadium content promotes the precipitation of V(C,N) and strengthens the steel, while also reducing low-temperature toughness. Therefore, its content is not high in most steels. Taking these considerations into account, the present invention controls the vanadium content to 0.10-0.20% by weight.

[0040] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention 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 present invention controls the mass percentage of copper to be in the range of 0.08 to 0.18%.

[0041] The high-strength, non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention contains aluminum at a mass percentage of 0.02% or less. During the steelmaking process, aluminum acts as a strong deoxidizer, significantly reducing oxygen. Most steels are deoxidized using aluminum or aluminum-containing composite deoxidizers, creating inclusions to control the oxygen content in the molten steel. However, the formation of Al2O3 and AlN inclusions, if left in the steel, can severely reduce low-temperature plasticity and toughness. Therefore, the present invention strictly controls the aluminum content to within 0.02% by mass.

[0042] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention comprises a balance of Fe and inevitable impurities.

[0043] In the present invention, 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 the present invention, 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 the present invention, 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 invention, the mass percentages of Ti and W in the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor are 0.

[0044] The present invention 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:

[0045] Weigh the raw materials, smelt and forge them in sequence to obtain bars;

[0046] 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.

[0047] In the present invention, unless otherwise specified, the raw materials used in the present invention are pre-selected as commercially available products.

[0048] The invention weighs raw materials, performs smelting and forging in sequence, and obtains rods.

[0049] In the present invention, the raw materials are preferably weighed according to the mass percentage of the elements specified in the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor as described in the above technical solution.

[0050] In the present invention, the smelting preferably includes sequentially performing medium frequency induction smelting and electroslag remelting.

[0051] In the present invention, the deoxidizer used in the medium-frequency induction smelting preferably includes Ca-Si, Ni-Mg alloy, and Ce. The medium-frequency induction smelting temperature is preferably 1510±10°C, and the duration is preferably ≥40 minutes. In the present invention, the medium-frequency induction smelting is preferably performed in a 5t / 10t medium-frequency induction furnace. The present invention does not specifically limit the specific operation of medium-frequency induction smelting of the raw materials in the 5t / 10t medium-frequency induction furnace, and those skilled in the art will suffice using familiar technical means.

[0052] In the present invention, the slag system used in the electroslag remelting is preferably a quaternary slag system of CaF2-Al2O3-CaO-MgO. In the present invention, the electroslag remelting is preferably performed under a protective atmosphere, preferably dry air. In the present invention, the raw materials used in the electroslag remelting are preferably medium-frequency electrodes obtained through medium-frequency induction smelting. In the present invention, stripping is preferably performed 6-8 hours after the completion of the electroslag remelting; the stripping process is preferably protected by a heat shield.

[0053] In the present invention, 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.

[0054] After obtaining the rod, the present invention performs a solid solution treatment on the rod to obtain the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor.

[0055] In the present invention, 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.

[0056] After the solution treatment, the present invention preferably further comprises water quenching to room temperature.

[0057] In the present invention, 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.

[0058] The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present invention, its manufacturing method and application are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0059] 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%).

[0060] Table 1 Chemical composition of high-strength non-magnetic austenitic stainless steel bars in the embodiment (wt.%)

[0061] C O N H Cr Ni Mo Mn Design value ≤0.01 ≤0.0020 0.26～0.40 ≤0.0006 20.5～22.5 14.0～15.5 1.8～2.2 5.0～6.0 Example 1 0.0058 0.0013 0.27 0.00057 21.67 14.47 1.92 6.0 Example 2 0.004 0.0018 0.24 0.00048 20.43 14.96 2.02 5.71 Example 3 0.008 0.0010 0.27 0.00035 19.82 14.53 1.90 5.69 Al Si P S V Nb Cu Fe Design value ≤0.02 ≤0.20 ≤0.005 ≤0.004 0.10～0.20 0.04～0.16 0.08～0.18 margin Example 1 0.008 0.13 0.0046 0.0036 0.13 0.07 0.15 margin Example 2 0.012 0.14 0.0043 0.0020 0.15 0.07 0.14 margin Example 3 0.005 0.14 0.0048 0.0014 0.14 0.04 0.12 margin

[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] High temperature diffusion temperature ℃ Forging temperature ℃ Final forging temperature ℃ Example 1 1210 1070 890 Example 2 1220 1080 880 Example 3 1200 1070 870

[0065] 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.

[0066] Table 3 Mechanical properties of the examples after different solution treatments

[0067]

[0068] It can be seen from Table 3 that both Example 2 and Example 3 have the best strength-plasticity match 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 invention 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.

[0069] Figure 1 The following are the actual photos of the bars obtained by forging and the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor obtained by solution treatment in Example 1. The left picture is the actual photo of the bars obtained by forging, and the right picture is the actual photo of the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor obtained by solution treatment. Figure 1 It can be seen that during and after the forging process, the surface quality of the bar is good, without macro defects such as cracks and micro cracks.

[0070] Figure 2 This is a photo of the grain size of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solution treatment in Example 2. Figure 2It can be seen that the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor has uniform grain size and uniform size distribution. 23 C6 carbide and delta-ferrite.

[0071] The microstructure of the fracture of the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor obtained by solid solution treatment in Example 3 after tensile test at 4.2K liquid helium temperature was characterized by using scanning electron microscope (SEM) technology, and the results are shown in FIG. 6. Figure 3 It can be seen that the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor has uniform grain size and uniform size distribution. Figure 3 It can be seen that the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor has uniform grain size and uniform size distribution.

[0072] In addition, the microstructure of the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor obtained by solid solution treatment in Example 3 after tensile test at 4.2K liquid helium temperature was characterized by using electron backscatter diffraction (EBSD) technology, and the results are shown in FIG. 7. Figure 4 It can be seen that the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor has uniform grain size and uniform size distribution. Figure 4 It can be seen that the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor has uniform grain size and uniform size distribution.

[0073] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope 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: 14.0~14.96%, 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 Nieq / Creq ≥ 1.1; The method for manufacturing high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor comprises the following steps: Weigh the raw materials, smelt and forge them in sequence to obtain bars; The rod is subjected to a solution treatment to obtain the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor; 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 CaF2-Al2O3-CaO-MgO quaternary slag system, and the electroslag remelting is carried out under a protective atmosphere, which is dry air; The temperature of the solution treatment is 1120°C to 1180°C, and the time is 1 to 2 hours; The microstructure of the high-strength non-magnetic austenitic stainless steel bar is an austenite matrix without M 23 C6 carbide and delta-ferrite.

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 solution treatment to obtain the high-strength non-magnetic austenitic stainless steel rod suitable for nuclear fusion armor; 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 CaF2-Al2O3-CaO-MgO quaternary slag system, and the electroslag remelting is carried out under a protective atmosphere, which is dry air; The temperature of the solution treatment is 1120° C. to 1180° C., and the time is 1 to 2 hours.

3. 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.

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

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