Low-temperature high-toughness austenitic stainless steel welding wire and preparation method thereof

Abstract

The application relates to a low-temperature high-strength and high-toughness austenitic stainless steel welding wire and a preparation method thereof, and belongs to the technical field of welding materials, and specifically relates to a welding wire and a preparation method thereof, which can keep high-strength and high-toughness mechanical properties of a molten metal formed by the welding wire in a low-temperature environment; the welding wire is provided with Ti elements, and the amount relationship of Al elements and Ti elements is controlled, and the mass ratio of Al / Ti is kept as (5-10):1; the proper amount of Al elements can purify the molten pool during welding work, and the proper amount of Ti elements can effectively stabilize the austenitic phase, so that the welding wire has basic welding capacity, and after the welding wire is changed into the molten metal, the material properties of the molten metal can meet the use requirements in room temperature and super-low-temperature environments, that is, the molten metal has and keeps good tensile properties, impact properties and the like, so that pipes, containers and the like prepared from the molten metal can be used for transmitting or loading special low-temperature materials such as liquid hydrogen and liquid helium.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically to a welding wire whose cladding metal maintains high strength and toughness mechanical properties at low temperatures, and its preparation method. Background Technology

[0002] With the development of science and technology, green energy application materials are gradually being widely used. For example, stainless steel is increasingly used in ultra-low temperature environments. Currently, stainless steel is commonly used to store containers or transport liquid hydrogen (boiling point of -252.8℃, freezing point of -259.2℃, critical pressure of 1.3MPa at one standard atmosphere) and liquid helium (boiling point of -269℃ at one standard atmosphere).

[0003] In cryogenic environments, extremely high requirements are placed on materials' resistance to brittle fracture and structural stability. Many existing stainless steel materials already possess good mechanical properties in cryogenic environments. However, containers made of stainless steel often require the use of welding wire to weld together multiple materials. Therefore, in practical applications, the cladding metal formed by the welding wire must also possess sufficient mechanical properties in cryogenic environments, such as high low-temperature strength and toughness.

[0004] Patent application number 202410717390.8 discloses an ultra-low temperature high-strength and high-toughness austenitic stainless steel welding wire and its preparation method. The weld metal formed by this austenitic stainless steel welding wire meets the following mechanical properties at a liquid helium temperature of 4.2K (i.e., -269℃): yield strength ≥1200MPa, tensile strength ≥1550MPa, elongation ≥25%, and fracture toughness ≥150MPa·m. 1 / 2 .

[0005] However, with the further development of high-precision fields such as aerospace and nuclear engineering, the mechanical properties of the cladding metal formed by existing welding wires are no longer sufficient to meet the latest and higher application requirements. There is an urgent need for a welding wire whose cladding metal possesses better mechanical properties, thereby enabling welded containers, pipelines, and other equipment to have higher stability and durability. Summary of the Invention

[0006] This invention provides a low-temperature high-strength and high-toughness austenitic stainless steel welding wire that still has excellent mechanical properties in ultra-low temperature environments, so as to meet the material selection requirements for welding materials in ultra-low temperature environments.

[0007] This invention is achieved through the following technical solution: A low-temperature high-strength and high-toughness austenitic stainless steel welding wire, the components of which, by weight percentage, include: C≤0.03%, Si≤1.0%, Mn: 12.0~18.0%, Cr: 18.0~23.0%, Ni: 16.0~20.0%, Mo: 2.0~3.0%, N: 0.30~0.60%, total Nb and V: 0.1~0.4%, 0<Al≤0.05%, 0<Ti≤0.005%, unavoidable impurities, and the balance Fe, wherein the ratio of Al content to Ti content is Al:Ti = (5~10):1.

[0008] The welding wire of the present invention forms a cladding metal after welding. This cladding metal is mainly used in ultra-low temperature environments, such as -196℃ and -269℃. In such environments, it is necessary to ensure that the cladding metal has sufficient mechanical properties. However, compared with ordinary stainless steel, it is also necessary to ensure that the welding wire itself has the required welding performance. Therefore, the composition of the welding wire needs to be controlled and coordinated accordingly. Compared with the prior art, the present invention introduces Ti element and controls the relationship between the amount of Al and Ti.

[0009] Specifically, in this invention, Al is mainly used as a deoxidizer, which can combine with O to form Al2O3, reducing the presence of free O elements and thus purifying the molten pool during welding. Ti preferentially combines with C to form TiC, reducing the risk of Cr carburization and effectively stabilizing the austenite phase, preventing austenite from transforming into ferrite or other non-austenite phases at high temperatures or during cooling.

[0010] In this invention, the inventors control the ratio of Al content to Ti content because when the ratio of Al content to Ti content is too high (i.e., when the Al content is relatively high), the low-temperature toughness of the material will be lost. Specifically, excessive Al will promote the formation of ferrite. Therefore, when its content is much higher than that of Ti, the effect of Ti in stabilizing austenite will be difficult to compensate for the influence of Al. That is, Al will easily reduce the stability of austenite and increase the risk of martensite transformation. Moreover, the probability of this phenomenon occurring in ultra-low temperature environments will be greatly increased, resulting in a weakening of the material's performance in ultra-low temperature environments. When the ratio of Al to Ti content is too low (i.e., when the Ti content is too high), although Ti can improve the low-temperature toughness of the material and refine the grains to enhance the low-temperature impact toughness, Ti itself is chemically reactive. In the high-temperature environment involved in austenitic processing, it easily reacts with O to form brittle substances. When the ratio of Al to Ti content is lower than that in this invention, Al cannot exert a sufficient deoxidation effect, which leads to O reacting with a large amount of Ti, producing a large amount of brittle substances and ultimately causing a decline in material properties.

[0011] As a further improvement of the present invention, the unavoidable impurities in the components include O and H, with the O content controlled below 20 ppm and the H content controlled below 10 ppm. In this invention, on the one hand, the content of free O element is controlled by selecting raw materials, such as adding Al as a deoxidizer; on the other hand, impurities such as O and H elements carried from the processing environment are reduced by drying the materials during processing.

[0012] Controlling the oxygen (O) content can reduce the amount of oxide inclusions formed in the material, thereby reducing the total number of crack initiation sites. Controlling the hydrogen (H) content can reduce the possibility of hydrogen embrittlement caused by the diffusion and accumulation of H elements in the weld at grain boundaries or dislocations after the weld wire forms cladding metal. Especially under low-temperature conditions, it can also reduce the possibility of delayed crack initiation (such as under-weld cracks) and reduce the probability of reduced fracture toughness due to H element accumulation.

[0013] As a further improvement of the present invention, the unavoidable impurities in the components include P and S, with P ≤ 0.010% and S ≤ 0.005% by weight percentage.

[0014] As a further improvement of the present invention, the total weight percentage of Ni and Mn is >30%.

[0015] As a further improvement to the present invention, the chromium equivalent Cr eq and nickel equivalent Ni eq The relationship is as follows: 1.2≤Creq / Ni eq ≤2.0.

[0016] As a further improvement of the present invention, the austenitizing stability coefficient Δ≥0, and the formula for calculating the austenitizing stability coefficient Δ is as follows: The formula can be found in standard CGA G-5.6 (R2013) Hydrogen Pipeline Systems (EIGADoc. 121 / 04). Within this range, it indicates that the composition of the welding wire is designed to effectively maintain the stability of the austenitic structure and avoid the formation of harmful phases (such as ferrite, martensite, or intermetallic compounds).

[0017] As a further improvement of the present invention, the ferrite content in the welding wire is ≤0.5%.

[0018] Secondly, the present invention provides a method for preparing low-temperature high-strength and high-toughness austenitic stainless steel welding wire, which is used to prepare any of the above-mentioned low-temperature high-strength and high-toughness austenitic stainless steel welding wire, comprising at least the following steps: S1. Drying each alloy raw material, then mixing all raw materials in proportion and refining them into molten steel, and refining them by electroslag remelting to obtain an electroslag ingot; S2. Forging the electroslag ingot into a billet, and then hot-working it into a wire rod, wherein the forging temperature is 1100~1220℃, the final forging temperature is 1000~1100℃, the forging ratio of the ingot is ≥4.0, the hot rolling temperature is 1150~1220℃, and the final rolling temperature is 1100~1150℃; S3. Performing solution heat treatment on the wire rod, and then drawing it, wherein the heat treatment temperature is 1080~1180℃, and the heat treatment time is ≥20 minutes. min; S4: Repeat the processing steps in S3 until the size of the processed welding wire is φ1.0~2.4mm; S5: Perform solution heat treatment on the welding wire, wherein the final heat treatment temperature is 1060~1140℃ and the heat treatment time is ≥10 min.

[0019] Preferably, in S1, the drying temperature of each alloy raw material is 250~400℃, and the drying time is ≥48 h.

[0020] Preferably, in S4, when the cold drawing deformation is ≥20%, the heat treatment temperature is 1100~1180℃ and the heat treatment time is ≥20 min; when the cold drawing deformation is ≤20%, the heat treatment temperature is 1050~1140℃ and the heat treatment time is 10~20 min.

[0021] The beneficial effects of this invention are as follows: (1) In this invention, the risk of Cr carbonization in the material is reduced by introducing Ti element, thereby effectively stabilizing the austenitic phase in the material and preventing the austenitic phase from transforming into ferrite or other non-austenitic phases under conditions such as high temperature or cooling process after welding; secondly, by controlling the ratio of Al content to Ti content in the material, it is ensured that an appropriate amount of Al element can play a role in purifying the molten pool during welding, and an appropriate amount of Ti element can effectively stabilize the austenitic phase, thereby ensuring that the welding wire has basic welding capabilities. At the same time, after the welding wire is transformed into cladding metal after welding, its own material properties can meet the requirements for use at room temperature and in ultra-low temperature environments, that is, it has and maintains good tensile properties, impact properties, etc., so that the pipes and containers prepared by it can be used to transport or load special low temperature materials such as liquid hydrogen and liquid helium.

[0022] (2) The present invention also provides a method for preparing welding wire. In the preparation method, by controlling the processing parameters such as temperature and duration, the required welding wire can be prepared efficiently. The surface quality of the prepared welding wire is good and the microstructure is stable. This ensures that welding wire that meets the requirements for use is prepared efficiently, which is conducive to the promotion and production of this type of welding wire.

[0023] (3) Under preferred conditions, the alloy raw materials in the welding wire preparation method of the present invention are dried. This step can reduce the water content carried by the raw materials during the processing, that is, minimize the content of H and O elements carried by the raw materials. At the same time, the use of deoxidizers such as Al is used to reduce the content of H and O elements in the finished product, thereby ensuring that the mechanical properties of the cladding metal formed by the welding wire can meet higher application requirements in the ultra-low temperature environment, such as tensile strength and yield strength. Attached Figure Description

[0024] The accompanying drawings are provided below to illustrate the preferred embodiments of the invention and to aid in understanding the objectives and advantages of the invention, wherein: Figure 1 This is a microscopic image of the surface of a low-temperature, high-strength, and high-toughness austenitic stainless steel welding wire. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0027] Example 1: This embodiment provides a low-temperature high-strength and high-toughness austenitic stainless steel welding wire, the components of which are shown in Table 1. Except for O and H elements, all other elements are expressed as weight percentage (wt%), and the content of O and H elements is in ppm. In addition to the components marked in the table, the other components are Fe and unavoidable impurities.

[0028] Table 1 Summary of component content in Example 1 serial number C Si Mn Cr Ni Mo N Nb+V Al Ti O H P S Example 1 0.025 1.0 14.0 20.0 17.0 2.3 0.40 0.25 0.08 0.016 18 8 0.008 0.005 The welding wire in this embodiment is obtained through the following steps: S1. Dry each alloy raw material to reduce the water content in the metal raw material. The drying temperature is 300℃ and the duration is 50 h. Mix all raw materials according to the ratio, melt the raw materials into molten steel by vacuum induction smelting, and then refine them by electroslag remelting to obtain electroslag ingots. S2. The electroslag ingot is forged at 1150 ℃ to form a blank, and then forged at 1050 ℃ to form a final forging. The forging ratio of the steel ingot reaches 5.0, and the final processing yields wire rod with a size of φ5.5 mm. S3. The wire rod is subjected to solution heat treatment and then drawn. The heat treatment temperature is 1080 ℃ and the heat treatment duration is 25 min. The hot rolling temperature is 1200 ℃ and the final rolling temperature is 1150 ℃. S4. Repeat steps in S3 until the processed welding wire reaches φ2.0 mm. When the cold drawing deformation is ≥20%, the heat treatment temperature is 1150 ℃ and the heat treatment time is 25 min; when the cold drawing deformation is ≤20%, the heat treatment temperature is 1100 ℃ and the heat treatment time is 15 min. S5. Perform solution heat treatment on the welding wire, wherein the final heat treatment temperature is 1130 ℃ and the heat treatment time is 20 min.

[0029] Example 2: The difference between this embodiment and Embodiment 1 is that the components of the low-temperature high-strength and high-toughness austenitic stainless steel welding wire in this embodiment are shown in Table 2.

[0030] Table 2 Summary of component content in Example 2 serial number C Si Mn Cr Ni Mo N Nb+V Al Ti O H P S Example 2 0.028 0.93 16.0 22.0 19.0 2.1 0.43 0.33 0.10 0.01 16 9 0.008 0.003 Example 3: The difference between this embodiment and Embodiment 1 is that the components of the low-temperature high-strength and high-toughness austenitic stainless steel welding wire in this embodiment are shown in Table 3.

[0031] Table 3 Summary of component content in Example 3 serial number C Si Mn Cr Ni Mo N Nb+V Al Ti O H P S Example 3 0.03 0.85 15.5 19.0 18.5 2.6 0.52 0.18 0.16 0.02 16 7 0.006 0.004 Example 4: The difference between this embodiment and Embodiment 1 is that the components of the low-temperature high-strength and high-toughness austenitic stainless steel welding wire in this embodiment are shown in Table 4.

[0032] Table 4 Summary of component content in Example 4 serial number C Si Mn Cr Ni Mo N Nb+V Al Ti O H P S Example 4 0.019 0.76 17.5 22.0 16.5 2.9 0.38 0.28 0.24 0.04 18 6 0.009 0.003 Performance testing: In this embodiment, the performance of the welding wires prepared in Examples 1-4 is tested, or the performance of the cladding metal formed after welding the welding wires is tested. For experimental methods where specific conditions are not specified, they are generally determined according to national standards. If there is no corresponding national standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0033] by Figure 1 As shown in the figure, the inclusion content in each group of welding wires was automatically statistically analyzed under a 100X microscope. The detection results of Examples 1 to 4 are shown in Table 5.

[0034] Table 5. Statistical table of inclusion content of welding wires in Examples 1-4 under a 100X magnification microscope Serial Number <![CDATA[Average inclusion content (number / mm 2 )]]> Percentage of inclusions smaller than 3.0 μm Percentage of inclusions smaller than 5.0 μm Percentage of inclusions larger than 15.0 μm Example 1 29 91 96 0.8 Example 2 26 95 98 0.8 Example 3 28 94 95 0.9 Example 4 25 93 95 1.0 The welding wires in Examples 1 to 4 were first welded to form cladding metal. The cladding metal was then processed into a sample with a size of 10×10×55mm, and the mechanical properties of impact absorption energy and lateral expansion value were tested. The test results are shown in Table 6.

[0035] Table 6 Statistical table of mechanical property test results of welding wire in Examples 1-4 Serial Number -196℃, impact absorbed energy (J) -196℃, lateral expansion value (mm) -269℃, impact absorbed energy (J) -269℃, lateral expansion value (mm) Example 1 110 1.2 88 1.1 Example 2 100 1.3 82 1.5 Example 3 125 1.2 85 1.3 Example 4 115 1.4 86 1.2 The welding wires in Examples 1 to 4 were welded to form deposited metals, and the mechanical properties and ferrite number of the deposited metals were tested. The test results are shown in Table 7.

[0036] Table 7 Statistical table of mechanical property test results of welding wire after cladding metal formation in Examples 1-4 Serial Number Ferrite content (%) Tensile strength (MPa) at room temperature Yield strength (MPa) at room temperature Room temperature, elongation (%) -196℃, tensile strength (MPa) -196℃, yield strength (MPa) -196℃, elongation (%) -269℃, tensile strength (MPa) -269℃, yield strength (MPa) -269℃, elongation (%) Example 1 0.45 720 351 42 1230 840 31 1850 1230 26 Example 2 0.44 715 356 44 1240 820 36 1820 1240 28 Example 3 0.43 708 354 43 1320 815 38 1830 1220 29 Example 4 0.48 703 361 45 1280 830 39 1800 1210 29 As can be seen from the test results in Table 5, under the preparation method of this invention, the non-metallic inclusion index of the prepared welding wire sample observed under a 100X magnification microscope can meet the following requirements: average inclusion content ≤30 inclusions / mm². 2The inclusion size is less than 3.0 μm, accounting for ≥90%; the inclusion size is less than 5.0 μm, accounting for ≥95%; and the inclusion size is greater than 15.0 μm, accounting for ≤1%. Controlling the number of non-metallic inclusions can improve the low-temperature performance of the material and simultaneously improve the low-temperature performance of the cladding metal formed by the welding wire, thus proving that the preparation method in this invention can produce qualified welding wire products.

[0037] As can be seen from the test results in Tables 6 and 7, the ferrite content of the welding wire prepared in this invention can be maintained at ≤0.5% after the formation of the cladding metal. At -269℃, the mechanical properties of the cladding metal can achieve tensile strength ≥1800MPa, yield strength ≥1200MPa, and elongation ≥25%; at -196℃, the mechanical properties can achieve tensile strength ≥1200MPa, yield strength ≥800MPa, and elongation ≥30%; at room temperature, the mechanical properties can achieve tensile strength ≥700MPa, yield strength ≥350MPa, and elongation ≥40%. Simultaneously, the impact performance of the cladding metal formed by the welding wire at -269℃ can achieve: impact absorption energy KV2 ≥80J, lateral expansion value LE ≥1.0mm; at -196℃, the impact absorption energy KV2 ≥100J, and lateral expansion value LE ≥1.0mm.

[0038] Compared to the mechanical property test results of the cladding metal of the welding wire disclosed in the prior art patent application number 202410717390.8, the cladding metal formed by the welding wire in this invention does not weaken at -269℃, and on this basis, the tensile strength is significantly improved. At the same time, the test results of this invention show that the cladding metal formed by the welding wire can maintain good mechanical properties at room temperature and in other low-temperature environments (such as -196℃), thus meeting the requirements for use with different materials such as liquid nitrogen and liquid helium.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-temperature, high-strength, high-toughness austenitic stainless steel welding wire, characterized in that, Its components, by weight percentage, include: C≤0.03%, Si≤1.0%, Mn: 12.0~18.0%, Cr: 18.0~23.0%, Ni: 16.0~20.0%, Mo: 2.0~3.0%, N: 0.30~0.60%, Total Nb and V: 0.1~0.4%, 0<Al≤0.05%, 0<Ti≤0.005%, unavoidable impurities and Fe balance, wherein the ratio of Al content to Ti content is Al:Ti = (5~10):1; The total weight percentage of Ni and Mn is greater than 30%; Chromium equivalent Cr eq and nickel equivalent Ni eq The relationship is as follows: 1.2≤Cr eq / Ni eq ≤2.0; The austenitizing stability coefficient Δ≥0, and the formula for calculating the austenitizing stability coefficient Δ is as follows: .

2. The low-temperature high-strength and high-toughness austenitic stainless steel welding wire according to claim 1, characterized in that, The unavoidable impurities mentioned in the composition include O and H, with the O content controlled to be less than 20 ppm and the H content controlled to be less than 10 ppm.

3. The low-temperature high-strength and high-toughness austenitic stainless steel welding wire according to claim 1, characterized in that, The unavoidable impurities mentioned in the composition include P and S, with P ≤ 0.010% and S ≤ 0.005% by weight.

4. The low-temperature high-strength and high-toughness austenitic stainless steel welding wire according to claim 1, characterized in that, The ferrite content in the welding wire is ≤0.5%.

5. A method for preparing low-temperature high-strength and high-toughness austenitic stainless steel welding wire, characterized in that, The method for preparing a low-temperature high-strength and high-toughness austenitic stainless steel welding wire according to any one of claims 1 to 4 comprises at least the following steps: S1. Dry all alloy raw materials, then mix all raw materials in proportion and refine them into molten steel. Refine the steel using the electroslag remelting method to prepare electroslag ingots. S2: The electroslag ingot is forged into a billet and then hot-worked into wire rod, wherein the forging temperature is 1100~1220℃, the final forging temperature is 1000~1100℃, the forging ratio of the steel ingot is ≥4.0, the hot rolling temperature is 1150~1220℃, and the final rolling temperature is 1100~1150℃. S3: The wire rod is subjected to solution heat treatment and then drawn, wherein the heat treatment temperature is 1080~1180℃ and the heat treatment time is ≥20 min; S4: Repeat the processing steps in S3 until the size of the welding wire obtained is φ1.0~2.4mm; S5: Perform solution heat treatment on the welding wire, wherein the final heat treatment temperature is 1060~1140℃ and the heat treatment time is ≥10 min.

6. The method for preparing low-temperature high-strength and high-toughness austenitic stainless steel welding wire according to claim 5, characterized in that, In S1, the drying temperature of each alloy raw material is 250~400℃, and the drying time is ≥48 h.

7. A method for preparing low-temperature high-strength and high-toughness austenitic stainless steel welding wire according to claim 5, characterized in that, In S4, when the cold drawing deformation is ≥20%, the heat treatment temperature is 1100~1180℃ and the heat treatment time is ≥20 min; when the cold drawing deformation is <20%, the heat treatment temperature is 1050~1140℃ and the heat treatment time is 10~20 min.

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