EP4696804A1 - High-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor and manufacturing method therefor - Google Patents

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

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Publication number
EP4696804A1
EP4696804A1 EP24862026.2A EP24862026A EP4696804A1 EP 4696804 A1 EP4696804 A1 EP 4696804A1 EP 24862026 A EP24862026 A EP 24862026A EP 4696804 A1 EP4696804 A1 EP 4696804A1
Authority
EP
European Patent Office
Prior art keywords
stainless steel
austenitic stainless
armor
strength
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24862026.2A
Other languages
German (de)
French (fr)
Inventor
Jianxiong Liang
Bin Zhao
Yu Liu
Weijun Wang
Changjun WANG
Jinggang QIN
Jin Hu
Zhenbao LIU
Jie Fan
Zhiyong Yang
Mengxing ZHANG
Yining WANG
Yongqing SUN
Jing Jin
Xiaohui Wang
Shuai TIAN
Weihan CHU
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Central Iron & Steel Research Institute Co Ltd
Pangang Group Jiangyou Changcheng Special Steel Co Ltd
China Iron and Steel Research Institute Group
Original Assignee
Central Iron & Steel Research Institute Co Ltd
Pangang Group Jiangyou Changcheng Special Steel Co Ltd
China Iron and Steel Research Institute Group
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Filing date
Publication date
Application filed by Central Iron & Steel Research Institute Co Ltd, Pangang Group Jiangyou Changcheng Special Steel Co Ltd, China Iron and Steel Research Institute Group filed Critical Central Iron & Steel Research Institute Co Ltd
Publication of EP4696804A1 publication Critical patent/EP4696804A1/en
Pending legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite

Definitions

  • 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 and its manufacturing method suitable for nuclear fusion armor.
  • the superconducting magnet armor is a barrier for the safe operation of the superconducting magnet and is the main carrier of the superconducting magnet to carry periodic and hundreds of tons of electromagnetic stress shocks under condition of liquid helium temperature (4.2K).
  • the ultra-low temperature structure material used in the superconducting magnet armor has a yield strength of 1250MPa, a tensile strength of 1700MPa, and an elongation after fracture of 25% at 4.2K, and the ultra-low temperature structural materials in the current ITER device cannot meet the load-bearing requirements of our country's fusion engineering experimental reactor. It is worth noting that the superconducting magnet armor in the nuclear fusion device not only needs to play a role of structural support, but also needs to serve as a protective cover for superconducting materials such as Nb 3 Sn, which makes it be the core component of the nuclear fusion device.
  • the superconducting magnet armor component in the nuclear fusion device needs to be prepared to be pipe from ultra-low temperature structural raw materials, because playing a role of support and protection for the core superconducting material, it also needs to be aged at a temperature of 250°C for 600h together with the superconducting material, which makes extremely strict requirements for the stability of the structure and performance of the superconducting magnet armor components. Therefore, it is urgent to develop a high-strength non-magnetic austenitic stainless steel with excellent ultra-low temperature strength and plasticity as the superconducting magnet armor component.
  • the present application aims to provide a high-strength non-magnetic austenitic stainless steel bar and its manufacturing method suitable for nuclear fusion armor.
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor of the present application has excellent ultra-low temperature plasticity.
  • the present application provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, which comprises 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%, the balance is Fe and inevitable impurities;
  • the present application also provides a method for manufacturing the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor described in the above technical solution, which comprises the following steps:
  • the smelting comprises sequentially performing medium frequency induction smelting and electroslag remelting.
  • the deoxidizer of the medium frequency induction smelting comprises Ca-Si, Ni-Mg alloy and Ce.
  • the medium frequency induction smelting has a temperature of 1510 ⁇ 10°C and a time of ⁇ 40min.
  • the slag system of the electroslag remelting is CaF 2 -Al 2 O 3 -CaO-MgO quaternary slag system, and the electroslag remelting is performed under a protective atmosphere, which is dry air.
  • parameters of the forging comprise: a temperature of a high temperature diffusion before the forging is 1180-1230°C, an initial forging temperature is 1050-1100°C, and a final forging temperature is 850-900°C.
  • the solution treatment has a temperature of 1120°C ⁇ 60°C and a time of 1 ⁇ 2 h.
  • the method also comprises water quenching the bar to room temperature.
  • the high-strength non-magnetic austenitic stainless steel bar of the present application eliminates high-temperature ⁇ -ferrite and M 23 C 6 , so that it has excellent strength and toughness matching and intergranular corrosion resistance at low temperatures.
  • the high-strength non-magnetic austenitic stainless steel bar of the present application has a yield strength of ⁇ 1250MPa, a tensile strength of ⁇ 1700MPa, 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 application is austenitic non-magnetic high-strength stainless steel, which can be directly used in structural parts such as conductor armor in nuclear reactors such as fusion reactors, can also be widely used in other related fields such as high-strength stainless parts required in low-temperature engineering, and have broad market prospects.
  • the smelting comprises sequentially performing medium frequency induction smelting and electroslag remelting, which precisely controls ultra-low carbon ( ⁇ 0.01%), ultra-low oxygen ( ⁇ 0.0020%) and nitrogen content (0.26-0.40%).
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor comprises carbon with a mass percentage of ⁇ 0.01%.
  • Carbon is an element in stainless steel that strongly forms and stabilizes austenite and expands the austenite zone and is also a material-strengthening element. However, it will damage the plasticity, toughness and weldability of the steel when making the strength of the steel be increased. In addition, the presence of the carbon element in the steel will cause the matrix to precipitate M 23 C 6 carbides during long aging at 650°C, which seriously deteriorates the low-temperature plasticity and toughness and corrosion resistance of the steel. Therefore, it needs to control ultra-low carbon content in the steel of the present application. All things considered, the carbon content of the steel of the present application is controlled within 0.01%.
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor comprises nitrogen with a mass percentage of 0.26 ⁇ 0.40%.
  • Nitrogen has a similar role to carbon, and adopting a way of interstitial solid solution to perform nitriding can significantly improve the strength of the steel.
  • the advantage of using nitrogen atoms for interstitial solid solution strengthening is that it improves strength without significantly damaging the plasticity and toughness, and it can ensure the non-magnetic nature of the matrix. Therefore, in the present application, adopting the nitrogen atom for solid solution strengthening, and the mass percentage of nitrogen is 0.26 ⁇ 0.40%.
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application include phosphorus with a mass percentage of ⁇ 0.006%.
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application include sulfur with a mass percentage of ⁇ 0.005%.
  • Impurity elements such as phosphorus and sulfur in steel significantly reduce the plasticity and toughness and welding performance. Since the steel of the present application adopts an intermediate frequency furnace + electroslag remelting double ultra-pure smelting process while using pure metal materials for smelting, the mass percentages of phosphorus and sulfur are controlled within 0.006% and 0.005% respectively.
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor comprises molybdenum with a mass percentage of 1.8 ⁇ 2.2%.
  • Molybdenum can increase the strength of steel through solid solution strengthening and the formation of Laves phase precipitation strengthening, and can significantly increase the hardenability of steel and improve the corrosion resistance of steel.
  • molybdenum can also form M 2 C carbide with a hexagonal crystal structure during the aging process, thereby improving the tempering stability and secondary hardening effect of steel.
  • the excessive content of molybdenum will promote the formation of ferrite, which leads to magnetic losses in the fusion reactor. All things considered, the present application controls the mass percentage of molybdenum to be1.8 ⁇ 2.2%.
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor comprises silicon with a mass percentage of ⁇ 0.20%.
  • Silicon mainly plays a deoxidizing role in steel. Since the steel of the present application uses pure metal materials and adopts an intermediate frequency furnace + electroslag remelting dual ultra-pure smelting process, there is no need to add too much silicon for deoxidation.
  • silicon is an element that promotes the formation of ferrite, which can seriously damage the low-temperature plasticity and toughness of steel, so it needs to strictly control the content of silicon. Based on the above considerations, the present application controls the mass percentage of silicon within 0.20%.
  • the present application also provides a method for manufacturing the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor described in the above technical solution, which includes the following steps:
  • the raw materials used in the present application are all pre-selected commercially available products.
  • the raw materials are preferably weighed according to the element mass percentages defined in the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor described in the above technical solution.
  • the smelting preferably comprises sequentially performing medium frequency induction smelting and electroslag remelting.
  • the deoxidizer of 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 min.
  • the medium frequency induction smelting is preferably carried out in a 5t/10t medium frequency induction furnace.
  • the present application does not specifically limit the specific operation of medium-frequency induction smelting of the raw materials in 5t/10t medium frequency induction furnace. Those skilled in the art can use well-known technical means.
  • the slag system of the electroslag remelting is preferably a CaF 2 -Al 2 O 3 -CaO-MgO quaternary slag system.
  • the electroslag remelting is preferably performed under a protective atmosphere, and the protective atmosphere is preferably dry air.
  • the raw material for electroslag remelting is preferably the intermediate frequency electrode obtained by the intermediate frequency induction smelting.
  • the ingot stripping process is preferably protected by a heat preservation cover.
  • the forging parameters preferably include: a temperature of the high temperature diffusion before forging is preferably 1180-1230°C, an initial forging temperature is preferably 1050-1100°C, and the final forging temperature is preferably 850-900°C.
  • the present application performs solid solution treatment of the obtained bar to obtain the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor.
  • the temperature of the solid solution treatment is preferably 1120°C ⁇ 60°C, and more preferably 1120-1180°C; the time is preferably 1-2 h.
  • the method of the present application preferably also includes water quenching to room temperature.
  • the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor is preferably used as the superconducting magnet armor in the nuclear fusion device.
  • Adopting the intermediate frequency electrode as the raw material for electroslag remelting and performing the electroslag remelting, and the parameters of the electroslag remelting include: electroslag remelting multiple intermediate frequency electrodes into steel ingots of required weight, the smelting slag of the electroslag remelting is CaF 2 -Al 2 O 3 -CaO-MgO quaternary slag system, performing the electroslag remelting under a protective atmosphere, which is dry air; performing the ingot stripping 6 ⁇ 8h after the electroslag remelting and using a thermal insulation cover to protect it during the period to obtain the steel ingot; the medium frequency induction smelting and the electroslag remelting achieve the accurately control of the ultra-low carbon ( ⁇ 0.01%), the ultra-low oxygen ( ⁇ 0.0020%) and the nitrogen content (0.26 ⁇ 0.40%).
  • Table 2 Forging temperature control process parameters of the embodiments Temperature of high-temperature diffusion /°C Initial forging temperature /°C Final forging Temperature /°C Embodiment 1 1210 1070 890 Embodiment 2 1220 1080 880 Embodiment 3 1200 1070 870

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
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  • Heat Treatment Of Steel (AREA)

Abstract

The present application belongs to the technical field of high-strength stainless steel, and provides a high-strength non-magnetic austenitic stainless steel bar and its manufacturing method suitable for nuclear fusion armor. The high-strength non-magnetic austenitic stainless steel bar of the present application eliminates high-temperature δ-ferrite and M23C6, which makes it have excellent strength and toughness matching and intergranular corrosion resistance at low temperature. The high-strength non-magnetic austenitic stainless steel bar of the present application has a yield strength of ≥1250MPa, a tensile strength of ≥1700MPa, a ductility of ≥25%, and a magnetic conductivity ≤1.02 at a liquid helium temperature of 4.2K; the high-strength non-magnetic austenitic stainless steel bar of the present application is austenitic non-magnetic high-strength stainless steel, which can be directly used in structural parts such as conductor armor in nuclear reactors such as fusion reactors, can also be widely used in other related fields such as high-strength stainless parts required in low-temperature engineering, and have broad market prospects.

Description

    TECHNICAL FIELD
  • 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 and its manufacturing method suitable for nuclear fusion armor.
    • BACKGROUND ART
  • In the engineering design of our country's large-scale superconducting fusion experimental device, the magnetic field strength and current of the magnet system have been significantly improved, which makes the electromagnetic load endured by the superconducting magnet increase by 60% compared with the International Thermonuclear Experimental Reactor (ITER) device. Wherein, the superconducting magnet armor is a barrier for the safe operation of the superconducting magnet and is the main carrier of the superconducting magnet to carry periodic and hundreds of tons of electromagnetic stress shocks under condition of liquid helium temperature (4.2K). The ultra-low temperature structure material used in the superconducting magnet armor has a yield strength of 1250MPa, a tensile strength of 1700MPa, and an elongation after fracture of 25% at 4.2K, and the ultra-low temperature structural materials in the current ITER device cannot meet the load-bearing requirements of our country's fusion engineering experimental reactor. It is worth noting that the superconducting magnet armor in the nuclear fusion device not only needs to play a role of structural support, but also needs to serve as a protective cover for superconducting materials such as Nb3Sn, which makes it be the core component of the nuclear fusion device. The superconducting magnet armor component in the nuclear fusion device needs to be prepared to be pipe from ultra-low temperature structural raw materials, because playing a role of support and protection for the core superconducting material, it also needs to be aged at a temperature of 250°C for 600h together with the superconducting material, which makes extremely strict requirements for the stability of the structure and performance of the superconducting magnet armor components. Therefore, it is urgent to develop a high-strength non-magnetic austenitic stainless steel with excellent ultra-low temperature strength and plasticity as the superconducting magnet armor component.
    • SUMMARY OF THE INVENTION
  • In view of this, the present application aims to provide a high-strength non-magnetic austenitic stainless steel bar and its manufacturing method suitable for nuclear fusion armor. The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor of the present application has excellent ultra-low temperature plasticity.
  • In order to achieve the above-mentioned object of the present application, the present application provides the following technical solutions:
  • The present application provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, which comprises 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%, the balance is Fe and inevitable impurities;
    • Controlling Nieq/Creq≥1.1.
  • The present application also provides a method for manufacturing the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor described in the above technical solution, which comprises the following steps:
    • Weighing raw materials, sequentially performing smelting and forging to obtain a bar;
    • Performing solid solution treatment of the bar to obtain the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor.
  • Preferably, the smelting comprises sequentially performing medium frequency induction smelting and electroslag remelting.
  • The deoxidizer of the medium frequency induction smelting comprises Ca-Si, Ni-Mg alloy and Ce. The medium frequency induction smelting has a temperature of 1510±10°C and a time of ≥40min.
  • The slag system of the electroslag remelting is CaF2-Al2O3-CaO-MgO quaternary slag system, and the electroslag remelting is performed under a protective atmosphere, which is dry air.
  • Preferably, parameters of the forging comprise: a temperature of a high temperature diffusion before the forging is 1180-1230°C, an initial forging temperature is 1050-1100°C, and a final forging temperature is 850-900°C.
  • Preferably, the solution treatment has a temperature of 1120°C ± 60°C and a time of 1~2 h.
  • Preferably, after the solid solution treatment, the method also comprises water quenching the bar to room temperature.
  • The present application provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, which comprises 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%, the rest is Fe and inevitable impurities; controlling Nieq/Creq≥1.1. The high-strength non-magnetic austenitic stainless steel bar of the present application eliminates high-temperature δ-ferrite and M23C6, so that it has excellent strength and toughness matching and intergranular corrosion resistance at low temperatures. The high-strength non-magnetic austenitic stainless steel bar of the present application has a yield strength of ≥1250MPa, a tensile strength of ≥1700MPa, 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 application is austenitic non-magnetic high-strength stainless steel, which can be directly used in structural parts such as conductor armor in nuclear reactors such as fusion reactors, can also be widely used in other related fields such as high-strength stainless parts required in low-temperature engineering, and have broad market prospects.
  • The present application also provides a manufacturing method for manufacturing the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor described in the above technical solution, which includes the following steps: weighing the raw materials, sequentially performing smelting and forging to obtain a bar; the bar is subjected to solid solution treatment to obtain the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor. The manufacturing method provided by the present application is simple to operate and easy to industrialize.
  • Further, the smelting comprises sequentially performing medium frequency induction smelting and electroslag remelting, which precisely controls ultra-low carbon (≤0.01%), ultra-low oxygen (≤0.0020%) and nitrogen content (0.26-0.40%).
    • A BRIEF DESCRIPTION OF DRAWINGS
    • Fig.1 is physical photos of the bar obtained by forging and the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 1, wherein, the left picture is the physical photo of the bar obtained by forging, the right picture is the physical photo of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment;
    • Fig. 2 is a photo of the grain size of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 2;
    • Fig. 3 is a characterization diagram of the fracture microstructure of the tensile specimen of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 3;
    • Figure 4 is the EBSD microstructure topography diagram of the tensile specimen of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 3.
    DETAILED DESCRIPTION OF THE INVENTION
  • The present application provides a high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, which comprises 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%, the rest is Fe and inevitable impurities;
    • Controlling Nieq/Creq≥1.1.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises carbon with a mass percentage of ≤0.01%. Carbon is an element in stainless steel that strongly forms and stabilizes austenite and expands the austenite zone and is also a material-strengthening element. However, it will damage the plasticity, toughness and weldability of the steel when making the strength of the steel be increased. In addition, the presence of the carbon element in the steel will cause the matrix to precipitate M23C6 carbides during long aging at 650°C, which seriously deteriorates the low-temperature plasticity and toughness and corrosion resistance of the steel. Therefore, it needs to control ultra-low carbon content in the steel of the present application. All things considered, the carbon content of the steel of the present application is controlled within 0.01%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises nitrogen with a mass percentage of 0.26~0.40%. Nitrogen has a similar role to carbon, and adopting a way of interstitial solid solution to perform nitriding can significantly improve the strength of the steel. For austenitic stainless steel, the advantage of using nitrogen atoms for interstitial solid solution strengthening is that it improves strength without significantly damaging the plasticity and toughness, and it can ensure the non-magnetic nature of the matrix. Therefore, in the present application, adopting the nitrogen atom for solid solution strengthening, and the mass percentage of nitrogen is 0.26~0.40%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application includes oxygen with a mass percentage of ≤0.0020%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises hydrogen with a mass percentage of ≤0.0006%. Oxygen dissolved in steel will exist in the form of various inclusions, which will seriously reduce the plasticity and toughness, fatigue performance and cold and hot processing properties of the steel. Hydrogen will cause hydrogen embrittlement and white spots in steel, which seriously reduces the toughness of steel. In summary, the present application controls the mass percentages of oxygen and hydrogen to be within 0.0020% (20ppm) and 0.0006% (6ppm) respectively.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application include phosphorus with a mass percentage of ≤0.006%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application include sulfur with a mass percentage of ≤0.005%. Impurity elements such as phosphorus and sulfur in steel significantly reduce the plasticity and toughness and welding performance. Since the steel of the present application adopts an intermediate frequency furnace + electroslag remelting double ultra-pure smelting process while using pure metal materials for smelting, the mass percentages of phosphorus and sulfur are controlled within 0.006% and 0.005% respectively.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises chromium with a mass percentage of 20.5~22.5%. Chromium is an important alloy element for the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor provided by the present application to have corrosion resistance. 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 formation of M23C6 and high-temperature Cr2N, which will seriously deteriorate the low-temperature toughness and high-temperature forgeability of the steel. Therefore, the present application controls the mass percentage content of chromium in the range of 20.5~22.5%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises nickel with a mass percentage of 14.0~15.5%. As one of the most important alloying elements for the formation of austenite, nickel can expand the austenite phase area and inhibit the formation of high-temperature δ ferrite. In addition, nickel can improve the low-temperature properties of nickel-chromium-based austenitic stainless steel, and the low-temperature toughness of the steel is significantly improved with the increase of nickel. All things considered, the present application controls the mass percentage content of nickel in the range of 14.0~15.5%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises molybdenum with a mass percentage of 1.8~2.2%. Molybdenum can increase the strength of steel through solid solution strengthening and the formation of Laves phase precipitation strengthening, and can significantly increase the hardenability of steel and improve the corrosion resistance of steel. In addition, molybdenum can also form M2C carbide with a hexagonal crystal structure during the aging process, thereby improving the tempering stability and secondary hardening effect of steel. However, the excessive content of molybdenum will promote the formation of ferrite, which leads to magnetic losses in the fusion reactor. All things considered, the present application controls the mass percentage of molybdenum to be1.8~2.2%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises manganese with a mass percentage of 5.0~6.0%. Manganese is also an austenite-forming element while it can reduce the critical cooling rate during quenching, which makes manganese improve the hardenability and thermoplasticity of the steel more effectively than any other alloying element. In addition, manganese is also a deoxidizer and desulfurizer. It can reduce the oxygen content in low-carbon components, and combine with sulfur to form manganese sulfide to eliminate the hazards of residual sulfur in steel. All things considered, the present application controls the mass percentage of manganese to be 5.0-6.0%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises silicon with a mass percentage of ≤0.20%. Silicon mainly plays a deoxidizing role in steel. Since the steel of the present application uses pure metal materials and adopts an intermediate frequency furnace + electroslag remelting dual ultra-pure smelting process, there is no need to add too much silicon for deoxidation. In addition, silicon is an element that promotes the formation of ferrite, which can seriously damage the low-temperature plasticity and toughness of steel, so it needs to strictly control the content of silicon. Based on the above considerations, the present application controls the mass percentage of silicon within 0.20%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises niobium with a mass percentage of 0.04~0.16%. The role of the micro-alloying element niobium in steel is mainly reflected that it inhibits the deformation recrystallization of austenite and prevents its grain growth in the thermal processing process, and induces the precipitation of Nb(C,N) by the strain of their carbon and nitrogen compounds, which has the strongest grain refinement and strengthening effect in steel. In addition, a small amount of strong carbide-forming element niobium can inhibit the formation of coarse Cr23C6 during the solid solution treatment of austenitic stainless steel, thereby significantly improving intergranular corrosion. Based on the above considerations, the mass percentage of niobium in the present application is 0.04~0.16%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises vanadium with a mass percentage of 0.10~0.20%. A small amount of vanadium can refine the structure and grains of steel and increase the grain coarsening temperature, thereby reducing overheating sensitivity and improving the strength and toughness of steel. Increasing the vanadium content will promote the precipitation of V(C,N) for strengthening while reducing the low-temperature toughness, so the content of vanadium in most steels is not high. Based on the above considerations, the present application controls the mass percentage content of vanadium to be 0.10-0.20%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises copper with a mass percentage of 0.08~0.18%. The addition of an appropriate amount of copper can generate ε-Cu to improve the strength and yield ratio of steel without adversely affecting the welding performance. In addition, as the content of copper increases, the strain hardening index will also decrease, which reduces the cold work hardening tendency and cold work cracking sensitivity of nickel-chromium-based austenitic stainless steel and has significant beneficial effects on the cold forming properties 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 the austenitic stainless steel. Therefore, the present application controls the mass percentage content of copper to be in the range of 0.08~0.18%.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application comprises aluminum with a mass percentage of ≤0.02%. During the steelmaking process, adopting aluminum as a strong deoxidizer can significantly deoxidize. Most steel is deoxidized by using aluminum or aluminum-containing composite deoxidizers to generate inclusions to control the oxygen content in the molten steel. However, if the generated Al2O3 and AlN inclusions remain in the steel, they will seriously reduce the low-temperature plasticity and toughness. Therefore, the present application strictly controls the mass percentage of aluminum within 0.02%.
  • The rest of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application is Fe and unavoidable impurities.
  • In the present application, in the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor, controlling Nieq/Creq to be ≥1.1, that is, the equivalent ratio of Ni and Cr is ≥1.1. In the present application, Nieq=Ni/%+30×C/%+25×N/%+0.5×Mn/%+Co/%+0.3×Cu/%, wherein, Ni/%, C/%, N/%, Mn/%, Co/% and Cu/% respectively 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. In the present application, Creq=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.
  • The present application also provides a method for manufacturing the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor described in the above technical solution, which includes the following steps:
    • Weighing the raw materials, sequentially performing smelting and forging to obtain a bar;
    • Performing solid solution treatment of the bar to obtain the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor.
  • In the present application, unless otherwise specified, the raw materials used in the present application are all pre-selected commercially available products.
  • In the present application, weighing the raw materials, sequentially performing smelting and forging to obtain a bar.
  • In the present application, the raw materials are preferably weighed according to the element mass percentages defined in the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor described in the above technical solution.
  • In the present application, the smelting preferably comprises sequentially performing medium frequency induction smelting and electroslag remelting.
  • In the present application, the deoxidizer of 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 min. In the present application, the medium frequency induction smelting is preferably carried out in a 5t/10t medium frequency induction furnace. The present application does not specifically limit the specific operation of medium-frequency induction smelting of the raw materials in 5t/10t medium frequency induction furnace. Those skilled in the art can use well-known technical means.
  • In the present application, the slag system of the electroslag remelting is preferably a CaF2-Al2O3-CaO-MgO quaternary slag system. In the present application, the electroslag remelting is preferably performed under a protective atmosphere, and the protective atmosphere is preferably dry air. In the present application, the raw material for electroslag remelting is preferably the intermediate frequency electrode obtained by the intermediate frequency induction smelting. In the present application, preferably performing ingot stripping 6-8 h after completing the electroslag remelting; the ingot stripping process is preferably protected by a heat preservation cover.
  • In the present application, the forging parameters preferably include: a temperature of the high temperature diffusion before forging is preferably 1180-1230°C, an initial forging temperature is preferably 1050-1100°C, and the final forging temperature is preferably 850-900°C.
  • The present application performs solid solution treatment of the obtained bar to obtain the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor.
  • In the present application, the temperature of the solid solution treatment is preferably 1120°C ± 60°C, and more preferably 1120-1180°C; the time is preferably 1-2 h.
  • After the solid solution treatment, the method of the present application preferably also includes water quenching to room temperature.
  • In the present application, the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor is preferably used as the superconducting magnet armor in the nuclear fusion device.
  • The high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor provided by the present application and its manufacturing method and application will be described in detail below with reference to embodiments. However, they should not be understood as limiting the scope of the present application.
  • Weighing the raw materials according to the element compositions of the high-strength non-magnetic austenitic stainless steel bars suitable for nuclear fusion armor as shown in Table 1, performing medium-frequency induction smelting in a 5t/10t medium-frequency induction furnace, and the parameters of the medium-frequency induction smelting include: adopting Ca-Si, Ni-Mg alloy and Ce for deoxidation in alloying stage, refining for 40min, and controlling the final temperature at 1510 ± 10°C to obtain an intermediate frequency electrode. Adopting the intermediate frequency electrode as the raw material for electroslag remelting and performing the electroslag remelting, and the parameters of the electroslag remelting include: electroslag remelting multiple intermediate frequency electrodes into steel ingots of required weight, the smelting slag of the electroslag remelting is CaF2-Al2O3-CaO-MgO quaternary slag system, performing the electroslag remelting under a protective atmosphere, which is dry air; performing the ingot stripping 6~8h after the electroslag remelting and using a thermal insulation cover to protect it during the period to obtain the steel ingot; the medium frequency induction smelting and the electroslag remelting achieve the accurately control of the ultra-low carbon (≤0.01%), the ultra-low oxygen (≤0.0020%) and the nitrogen content (0.26~0.40%). Table 1 Chemical components (wt.%) of the high-strength non-magnetic austenitic stainless steel bars in the embodiments
    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
    Embodiment 1 0.0058 0.0013 0.27 0.00057 21.67 14.47 1.92 6.0
    Embodiment 2 0.004 0.0018 0.24 0.00048 20.43 14.96 2.02 5.71
    Embodiment 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 balance
    Embodiment 1 0.008 0.13 0.0046 0.0036 0.13 0.07 0.15 balance
    Embodiment 2 0.012 0.14 0.0043 0.0020 0.15 0.07 0.14 balance
    Embodiment 3 0.005 0.14 0.0048 0.0014 0.14 0.04 0.12 balance
  • Forging the steel ingot according to the forging temperature control process parameters shown in Table 2 to obtain a bar. Table 2 Forging temperature control process parameters of the embodiments
    Temperature of high-temperature diffusion /°C Initial forging temperature /°C Final forging Temperature /°C
    Embodiment 1 1210 1070 890
    Embodiment 2 1220 1080 880
    Embodiment 3 1200 1070 870
  • Performing solid solution treatment of the obtained bar according to the conditions as shown in Table 3, and then water quenching to room temperature to obtain the final high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor. At the same time, listing the mechanical property test results of the obtained high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor in Table 3. Table 3 Mechanical properties of the steels in the embodiments after different solid solution treatments
    Solid solution heat treatment process Test temperature/K Tensile strength/MPa Yield strength/MPa Elongation after fracture /% Section shrinkage/%
    Embodiment 1 At 1120°C for 2h 4.2 1771 1420 29 27
    At 1170°C for 1h 4.2 1813 1334 28.5 29
    Embodiment 2 At 1120°C for 2h 4.2 1831 1332 28.5 44
    At 1170°C for 1h 4.2 1829 1273 34 49
    Embodiment 3 At 1150°C for 1.5h 4.2 1788 1404 33.5 40
    At 1180°C for 2h 4.2 1803 1401 35 40
  • It can be seen from Table 3 that the steels in both Embodiment 2 and Embodiment 3 have optimal strong plasticity matching at 1170-1180°C. The steel in Embodiment 2 has the tensile strength of 1829MPa, the yield strength of 1273MPa, the elongation after fracture of 34%, and the section shrinkage of 49% at the liquid helium temperature of 4.2K; the steel in Embodiment 3 has the tensile strength of 1803MPa, the yield strength of 1401MPa, the elongation after fracture of 35%, and the section shrinkage of 40% at the liquid helium temperature of 4.2K. As the temperature increases, the strength of the steel of the present application increases and the plasticity decreases. After the solid solution treatment at 1200°C in Embodiment 3, a certain content of high-temperature δ ferrite will be generated, which will damage its non-magnetic properties.
  • Fig.1 is physical photos of the bar obtained by forging and the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 1, wherein, the left picture is the physical photo of the bar obtained by forging, the right picture is the physical photo of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment. It can be seen from Fig.1: the surface quality of the bar is good and there are no macro defects such as cracks and microcracks during the forging process and after the forging process.
  • Fig.2 is a photo of the grain size of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 2. It can be seen from Fig.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 without containing M23C6 carbide and δ-ferrite.
  • Adopting scanning electron microscope SEM technology to characterize the microstructure of the fracture after being stretched at a liquid helium temperature of 4.2K of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 3. The results are shown in Fig.3. It can be seen from Fig.3 that: after the tensile test, there are a large number of dimples in the cross-section structure of the samples after different heat treatments, which indicates that the sample steels are all ductile fractures.
  • In addition, adopting electron backscatter diffraction EBSD technology to characterize the microstructure of the sample after being stretched at a liquid helium temperature of 4.2K of the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor obtained by solid solution treatment in Embodiment 3. The results are shown in Fig.4. It can be seen from Fig.4 that: the sample produces a large number of twin structures during the low-temperature stretching process, which is the reason why the steel of the present application has excellent strength and plasticity at ultra-low temperatures.
  • The above described are only preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present application. These improvements and modifications should be regarded as the protection scope of the present application.

Claims (6)

  1. A high-strength non-magnetic austenitic stainless steel bar suitable for a 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%, the rest is Fe and inevitable impurities;
    wherein controlling Nieq/Creq≥1.1.
  2. A manufacturing method of the high-strength non-magnetic austenitic stainless steel bar suitable for the nuclear fusion armor according to claim 1, comprising the following steps:
    weighing raw materials, sequentially performing smelting and forging to obtain a bar;
    performing solid solution treatment of the bar to obtain the high-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor.
  3. The manufacturing method according to claim 2, wherein, the smelting comprises sequentially performing medium frequency induction smelting and electroslag remelting;
    wherein a deoxidizer of the medium frequency induction smelting comprises Ca-Si, Ni-Mg alloy and Ce, the medium frequency induction smelting has a temperature of 1510±10°C and a time of ≥40min;
    wherein the electroslag remelting has a slag system of CaF2-Al2O3-CaO-MgO quaternary slag system and is performed under a protective atmosphere, and the protective atmosphere is dry air.
  4. The manufacturing method according to claim 2, wherein, parameters of the forging comprise: a temperature of a high temperature diffusion before the forging is 1180-1230°C, an initial forging temperature is 1050-1100°C, and a final forging temperature is 850-900°C.
  5. The manufacturing method according to claim 2, wherein, the solution treatment has a temperature of 1120°C ± 60°C and a time of 1~2 h.
  6. The manufacturing method according to claim 2 or 5, wherein, the method also comprises water quenching the bar to room temperature after the solid solution treatment.
EP24862026.2A 2023-09-06 2024-09-05 High-strength non-magnetic austenitic stainless steel bar suitable for nuclear fusion armor and manufacturing method therefor Pending EP4696804A1 (en)

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Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC ME MK MT NL NO PL PT RO RS SE SI SK SM TR