An austenitic stainless steel welding wire and its use

Abstract

The application discloses a high-strength and high-toughness austenitic stainless steel welding wire for ultra-low temperature and application thereof, and belongs to the technical field of metal materials (welding materials). The chemical composition of the welding wire is as follows (wt.%): C: ≤0.03%, Si ≤0.7%, V ≤0.3%, Cr: 17-20%, Mn: 10-20%, Ni: 15-20%, Nb ≤0.3%, Mo: 1.5-4.0%, N: 0.10-0.40%, and the balance is Fe and inevitable impurity elements. The welding wire is suitable for high-strength and high-toughness austenitic stainless steel for ultra-low temperature, the welding process is stable, and the weld forming shape is good. After high-temperature aging treatment after welding, the weld has excellent strength, plasticity and toughness at ultra-low temperature (-268.8 DEG C).

Description

Technical Field

[0001] This invention relates to the field of metal materials (welding materials), specifically to a high-strength and high-toughness austenitic stainless steel welding wire for cryogenic applications and its application. This welding wire is suitable for welding the armor of superconducting coils in fusion reactors. Background Technology

[0002] As a key component of fusion experimental reactors, superconducting coils provide a high magnetic field for the normal operation of the reactor. During the manufacturing process, the superconducting wire must undergo aging heat treatment, and the superconducting coil armor, as an integral structure, must also undergo high-temperature superconducting phase-forming aging heat treatment. This heat treatment process sensitizes conventional austenitic steel, significantly reducing its toughness, plasticity, and corrosion resistance. Therefore, the superconducting coil armor material must possess excellent strength and toughness even at ultra-low temperatures (-268.8℃) after aging heat treatment. The armor is a pipe structure that requires welding for connection; therefore, the welding material needs to possess excellent ultra-low temperature strength and toughness to ensure the weld meets service performance requirements. Traditional low-temperature austenitic steel welding materials, such as ER316L, have a yield strength below 1300 MPa at -268.8℃, and their toughness and plasticity decrease significantly after aging treatment. Therefore, a welding material that meets the strength and toughness requirements of the superconducting coil armor material and is resistant to aging is needed. Based on this, in order to meet the welding performance requirements of armor structures, the present invention provides a low-temperature austenitic steel welding material, which produces a weld with excellent strength and toughness after welding. Summary of the Invention

[0003] The purpose of this invention is to provide a high-strength and high-toughness austenitic stainless steel welding wire for cryogenic applications and its application. This welding wire is suitable for cryogenic stainless steel armor welding for fusion reactors.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A high-strength, high-toughness austenitic stainless steel welding wire for cryogenic applications has the following chemical composition by weight percentage:

[0006] C: ≤0.03%, Si ≤0.7%, V ≤0.3%, Cr: 17-20%, Mn: 10-20%, Ni: 15-20%, Nb ≤0.3%, Mo: 1.5-4.0%, N: 0.10-0.40%, with the balance being Fe and unavoidable impurity elements.

[0007] The chemical composition of this welding wire is: P≤0.01% (mass fraction); S≤0.01% (mass fraction).

[0008] The welding wire can be produced by vacuum induction furnace smelting or by electric furnace smelting and ladle refining. The final chemical composition of the welding wire should meet the requirements of the above range.

[0009] This welding wire is used for welding ultra-low temperature high-strength and high-toughness austenitic stainless steel in fusion reactors. The welding process is as follows: take a Φ2.0mm welding wire, use tungsten inert gas (TIG) welding, the joint type is butt joint, and the welding parameters are: welding current 150-200A, current type / polarity DCEN, welding speed 0.08-0.12m / min, arc protection uses high-purity argon gas with a purity ≥99.995%, and gas flow rate 15-20L / min.

[0010] The present invention has the following advantages:

[0011] 1. Experimental verification shows that the high-strength and high-toughness austenitic stainless steel welding wire for cryogenic applications of this invention is suitable for welding high-strength armor materials for fusion reactors.

[0012] 2. When using the ultra-low temperature high-strength and high-toughness austenitic stainless steel welding wire of the present invention for welding, the welding process is stable, with few defects, good weld formation, and good process performance.

[0013] 3. The high-strength and high-toughness austenitic stainless steel welding wire for ultra-low temperature applications of the present invention can produce weld metal with the required performance, especially with excellent strength and toughness at ultra-low temperature (-268.8℃).

[0014] 4. The weld obtained by welding with the ultra-low temperature high-strength and high-toughness austenitic stainless steel welding wire of the present invention, after aging treatment at 665℃ for 45-55h and 5% cold working, meets the following requirements:

[0015] Tensile strength at -268.8℃: yield strength not less than 1300MPa, tensile strength not less than 1600MPa, elongation after fracture not less than 20%;

[0016] Fracture toughness at -268.8℃ > 200 MPa·m 1 / 2 . Detailed implementation method:

[0017] In this invention, the high-strength and high-toughness austenitic stainless steel welding wire for ultra-low temperature applications is produced by vacuum induction furnace smelting; (or, it can also be produced by electric furnace smelting with ladle refining, as long as the final chemical composition of the welding wire meets the above requirements).

[0018] The following are preferred embodiments of the present invention:

[0019] Example 1

[0020] The raw materials used are chemical elements based on the target composition mass ratio of the welding wire in this embodiment, which are smelted in a vacuum induction furnace at a smelting temperature of 1580-1690℃.

[0021] The basic chemical composition (by weight) of this high-strength, high-toughness austenitic stainless steel welding wire for low-temperature applications is as follows:

[0022] C: 0.0079%, Si: 0.26%, V: 0.20%, Cr: 19.11%, Mn: 14.3%, Ni: 17.27%, Nb < 0.01%, Mo: 2.05%, P < 0.005%, S < 0.001%, N: 0.24%, balance being Fe and unavoidable impurity elements.

[0023] Example 2

[0024] The raw materials used are based on the target composition and chemical element ratio of the welding wire in this embodiment, and are smelted in a vacuum induction furnace at a smelting temperature of 1580-1690℃. The basic chemical composition (by weight) of this low-temperature high-strength, high-toughness austenitic stainless steel welding wire is as follows:

[0025] C: 0.0090%, Si: 0.24%, V: 0.21%, Cr: 19.11%, Mn: 14.3%, Ni: 17.31%, Nb < 0.01%, Mo: 2.05%, P < 0.005%, S < 0.001%, N: 0.29%, balance being Fe and unavoidable impurity elements.

[0026] Comparative Example 1

[0027] The raw materials used are based on the target composition and chemical element ratio of the welding wire in this comparative example, and are smelted in a vacuum induction furnace at a smelting temperature of 1580-1690℃. The basic chemical composition (by weight) of this low-temperature high-strength, high-toughness austenitic stainless steel welding wire is as follows:

[0028] C: 0.056%, Si: 0.25%, V: 0.21%, Cr: 18.97%, Mn: 5.2%, Ni: 17.9%, Nb: 0.11%, Mo: 3.53%, P < 0.005%; S < 0.0055%, N: 0.23%, balance being Fe and unavoidable impurity elements.

[0029] Comparative Example 2

[0030] The raw materials used are based on the target composition and chemical element ratio of the welding wire in this comparative example, and are smelted in a vacuum induction furnace at a smelting temperature of 1580-1690℃. The basic chemical composition (by weight) of this low-temperature high-strength, high-toughness austenitic stainless steel welding wire is as follows:

[0031] C: 0.054%, Si: 0.35%, V: 0.20%, Cr: 20.40%, Mn: 5.45%, Ni: 15.1%, Nb: 0.11%, Mo: 2.61%, P: 0.005%, S: 0.0055%, N: 0.18%, balance Fe and unavoidable impurity elements.

[0032] Comparative Example 3

[0033] The raw materials used are chemical elements based on the target composition of the welding wire in this comparative example, and are smelted in a vacuum induction furnace at a smelting temperature of 1580-1690℃.

[0034] The basic chemical composition (by weight) of this high-strength, high-toughness austenitic stainless steel welding wire for low-temperature applications is as follows:

[0035] C: 0.016%, Si: 0.26%, V: 0.21%, Cr: 18.95%, Mn: 5.25%, Ni: 18.8%, Nb: 0.22%, Mo: 3.51%, P: 0.004%, S: 0.0078%, N: 0.24%, balance Fe and unavoidable impurity elements.

[0036] The tensile properties of the welds in the above embodiments and comparative examples at -268.8℃ are shown in Table 1, and the fracture toughness is shown in Table 2.

[0037] Table 1. Tensile property test results of welds in the examples and comparative examples at -268.8℃.

[0038]

[0039] Table 2. Fracture toughness test results of welds in the examples and comparative examples at -268.8℃.

[0040]

[0041]

[0042] The welding test conditions for the above embodiments and comparative examples are as follows: The welding process of the welding wire is as follows: (The specified specification is missing from the original text.) Manual tungsten inert gas (TIG) welding was used for the butt joint of a square outer tube with a round inner tube. The tube wall thickness was 6-8 mm. The welding parameters were: welding current 160 A, DC positive polarity, welding speed 0.08-0.12 m / min, argon gas with a purity ≥99.995%, and a shielding gas flow rate of 18 L / min. The welding process was stable, the weld formation was good, and the process performance was excellent. X-ray non-destructive testing revealed no defects such as cracks or porosity.

[0043] All welds in the above embodiments and comparative examples underwent post-weld aging treatment at 665℃ for 50 hours before performance testing.

[0044] The performance design requirements for the weld of this low-temperature high-strength and high-toughness austenitic stainless steel welding wire are as follows: After post-weld aging treatment at 665℃ for 50h, the weld is roll-deformed along the length of the tube (deformation of the tube length is about 5%). At -268.8℃, the tensile strength is: yield strength not less than 1300MPa, tensile strength not less than 1600MPa, elongation after fracture not less than 20%; fracture toughness at -268.8℃ > 200MPa·m. 1 / 2 As can be seen from Examples 1 and 2 and Comparative Examples 1, 2 and 3, and Tables 1 and 2:

[0045] Examples 1 and 2 used the chemical composition of the welding wire designed according to the present invention, and its performance met the performance design requirements of the present invention. In Comparative Example 1, the C and Mn contents were not within the range of the technical solution of the present invention, and its weld yield strength, tensile strength, elongation after fracture, and fracture toughness at -268.8℃ did not meet the design requirements of the present invention. In Comparative Example 2, the C, Cr, and Mn contents were not within the range of the technical solution of the present invention, and its weld yield strength, tensile strength, elongation after fracture, and fracture toughness at -268.8℃ did not meet the design requirements of the present invention. In Comparative Example 3, the Mn content was not within the range of the technical solution of the present invention, and its weld yield strength, tensile strength, elongation after fracture, and fracture toughness at -268.8℃ did not meet the design requirements of the present invention.

[0046] The above embodiments merely illustrate several implementation methods of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. An application of an austenitic stainless steel welding wire, characterized in that: The chemical composition of this welding wire, by weight percentage, is as follows: C: ≤0.015%, Si: ≤0.4%, V: 0.2-0.3%, Cr: 18-20%, Mn: 14.3-20%, Ni: 16-19%, Nb≤0.3%, Mo: 1.5-3.0%, N: 0.20-0.40%, with the balance being Fe and other unavoidable impurity elements; The welding wire is used for fusion welding of the austenitic stainless steel armor of the superconducting coil in a fusion reactor. The operating temperature is the liquid helium temperature at atmospheric pressure, i.e., -268.8℃. After aging treatment at 665℃ for 45-55 hours and 5% cold working, the weld meets the following requirements at -268.8℃: yield strength ≥1300 MPa, tensile strength ≥1600 MPa, elongation after fracture ≥20%, and fracture toughness >200 MPa·m. 1 / 2 ; The welding process for this welding wire is as follows: manual tungsten inert gas welding is used, the joint type is butt welding, and the welding parameters are: welding current 150-200 A, current type is DC positive polarity, welding speed 0.08-0.12 m / min, arc shielding atmosphere is argon with purity ≥99.995%, and shielding gas flow rate during welding is 15-20 L / min.

2. The application of the austenitic stainless steel welding wire according to claim 1, characterized in that: The chemical composition of this welding wire also contains: P≤0.01%, S<0.01%.

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