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

Abstract

The invention discloses a low-temperature high-toughness austenitic stainless steel welding wire and a preparation method thereof, and relates to the technical field of welding materials, in particular to a welding wire with high-toughness mechanical properties of formed cladding metal in a low-temperature environment and a preparation method of the welding wire. The Ti element is introduced into the welding wire, the dosage relation of the Al element and the Ti element is controlled, and the mass ratio of Al to Ti is kept to be (5-10): 1; a proper amount of Al element can play a role in purifying a molten pool during welding work, a proper amount of Ti element can effectively stabilize an austenite phase, and therefore it is guaranteed that the welding wire has the basic welding capacity, and meanwhile after the welding wire is converted into cladding metal, the welding wire is not prone to deformation. The material characteristics and the like of the material can meet the use requirements at room temperature and ultralow temperature environment, that is, the material has and keeps good tensile property, impact property and the like, so that pipelines, containers and the like prepared from the material can be used for transmitting or loading special low-temperature materials such as liquid hydrogen, liquid helium and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of welding materials, and in particular to a welding wire in which a cladding metal maintains high strength and toughness mechanical properties under a low-temperature environment and a preparation method thereof. Background Art

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

[0003] Ultra-low temperature environments place extremely high demands on the material's resistance to brittle fracture and structural stability. While many existing stainless steel materials already possess good mechanical properties in ultra-low temperature environments, containers made of stainless steel often require welding wire to join multiple pieces of material together. Therefore, in actual use, the cladding metal formed by the welding wire must also possess sufficient mechanical properties in ultra-low temperature environments, such as high low-temperature strength and toughness.

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

[0005] However, with the continued development of cutting-edge fields such as aerospace and nuclear engineering, the mechanical properties of the cladding metal formed by existing welding wires are no longer able to meet the latest and higher requirements. There is an urgent need for welding wires that can produce cladding metals with improved mechanical properties, thereby ensuring greater stability and durability in welded vessels, pipelines, and other equipment. Summary of the Invention

[0006] The present invention provides a low-temperature, high-strength and tough austenitic stainless steel welding wire, which still has excellent mechanical properties under ultra-low temperature use environment, so as to meet the material selection requirements when welding materials in ultra-low temperature environment.

[0007] The present invention is achieved through the following technical solutions: A low-temperature, high-strength and tough austenitic stainless steel welding wire, comprising, by weight percentage, the following components: 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%, the total amount of Nb and V: 0.1-0.4%, 0 < Al ≤ 0.05%, 0 < Ti ≤ 0.005%, unavoidable impurities and a balance of Fe, wherein the ratio of Al content to Ti content is Al:Ti = (5-10):1.

[0008] The welding wire of the present invention will form a cladding metal after welding. The cladding metal is mainly used in ultra-low temperature environments, such as -196°C, -269°C, etc. In such environments, it is necessary to ensure that the cladding metal has sufficient mechanical properties, but at the same time, compared with ordinary stainless steel materials, it is also necessary to ensure that the welding wire itself has the required welding performance, etc. Therefore, the component ratio of the welding wire needs to be controlled and coordinated accordingly. Compared with the existing technology, the present invention introduces the Ti element and controls the dosage relationship between Al and Ti.

[0009] Specifically, in the present invention, Al can be primarily used as a deoxidizer, combining with O to form Al2O3, reducing the presence of free O and thus purifying the weld pool during welding. Ti, on the other hand, preferentially combines with C to form TiC, reducing the risk of Cr carburization and effectively stabilizing the austenite phase, preventing it from transforming into ferrite or other non-austenitic phases at high temperatures or during cooling.

[0010] In the present invention, the inventors control the ratio of Al content to Ti content. This is because when the ratio of Al content to Ti content is too high (that is, when the Al content is relatively too high), the low-temperature toughness of the material will be lost. Specifically, excessive Al elements will promote the formation of ferrite. Therefore, when its content is significantly higher than the Ti content, the effect of Ti elements in stabilizing austenite will be difficult to compensate for the impact of Al elements. That is, Al elements are likely to reduce the stability of austenite and increase the risk of martensitic transformation. Moreover, the probability of this phenomenon occurring in ultra-low temperature environments will be greatly increased, resulting in a weakening of the material performance in ultra-low temperature environments. When the ratio of Al content to Ti content is too low (i.e., when the Ti content is too high), although the Ti element can improve the low-temperature toughness of the material, refine the grains, and enhance the low-temperature impact toughness of the material, the Ti element itself has active chemical properties. Under the high-temperature environment involved in the austenitic processing process, it easily reacts with the O element to form a brittle substance. When the Al content to Ti content ratio is lower than that in the present invention, Al is unable to exert a sufficient deoxidation effect, which causes O to react with a large amount of Ti element, producing a large amount of brittle substance and ultimately causing a degradation of material properties.

[0011] As a further improvement of the present invention, the inevitable impurities in the components include O and H, with the O content controlled within 20 ppm and the H content within 10 ppm. The present invention achieves control of the free O content through the selection of raw materials, such as the addition of Al as a deoxidizer. Furthermore, by drying the materials during processing, impurities such as O and H carried over from the processing environment are reduced.

[0012] Controlling the O content can reduce the amount of oxide inclusions in the material, thereby reducing the total number of crack initiation points. Controlling the H content can reduce the possibility of hydrogen embrittlement, which can occur after the wire forms a cladding metal and then diffuse into the weld and accumulate at grain boundaries or dislocations. This can also reduce the likelihood of delayed cracking (such as sub-bead cracking), especially under low-temperature conditions, while also reducing the probability of H accumulation leading to a decrease in the material's fracture toughness.

[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.

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

[0015] As a further improvement of 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 austenitization stability coefficient Δ is ≥ 0, and the calculation formula of the austenitization stability coefficient Δ is as follows: This formula is derived from the standard CGA G-5.6 (R2013) Hydrogen Pipeline Systems (EIGA Doc. 121 / 04). Within this numerical range, the welding wire component dosage design effectively maintains the stability of the austenitic structure and avoids 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] In the second aspect, the present invention provides a method for preparing a low-temperature, high-strength and tough austenitic stainless steel welding wire, which is used to prepare any of the above-mentioned low-temperature, high-strength and tough austenitic stainless steel welding wires, which at least includes the following steps: S1. Drying each alloy raw material, then mixing all the raw materials in proportion and smelting them into molten steel, and refining them by electroslag remelting to prepare an electroslag ingot; S2: Forging the electroslag ingot into a blank, and then hot-processing it into a wire rod, wherein the forging blanking 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: Solution heat treating the wire rod, and then drawing it, 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 processed welding wire is φ1.0~2.4mm; S5: perform solid 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° C., 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 the present invention are: (1) In the present invention, firstly, the risk of carbonization of Cr in the material is reduced by introducing Ti element, thereby effectively stabilizing the austenite phase in the material and preventing the austenite from transforming into ferrite or other non-austenite phases under high temperature or in the 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 purify the molten pool during welding, and an appropriate amount of Ti element can effectively stabilize the austenite 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 use requirements at room temperature and ultra-low temperature environment, that is, it has and maintains good tensile properties, impact properties, etc., thereby enabling the pipes, containers, etc. prepared by it to be used for transporting or loading 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 processing parameters such as temperature and duration, the required welding wire can be efficiently prepared, and the prepared welding wire has good surface quality and stable structural properties, thereby ensuring that welding wire that meets the use requirements is efficiently prepared, which is conducive to the promotion and production of this type of welding wire.

[0023] (3) Under preferred conditions, the welding wire preparation method of the present invention performs a drying treatment on each alloy raw material. 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 can achieve a reduction in the content of H and O elements in the finished product, thereby ensuring that the mechanical properties of the cladding metal formed by the prepared welding wire in an ultra-low temperature environment, such as tensile strength and yield strength, can meet higher use requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following drawings are provided for use in conjunction with preferred embodiments of the present invention to help understand the objects and advantages of the present invention, wherein: Figure 1 This is a surface image of low-temperature, high-strength and tough austenitic stainless steel welding wire under a microscope. DETAILED DESCRIPTION

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

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present invention, rather than to represent all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0027] Example 1: In this embodiment, a low-temperature, high-strength and tough austenitic stainless steel welding wire is provided. The components of the wire are shown in Table 1. Except for the elements O and H, the remaining elements are expressed in weight percentage (wt%), and the contents of the elements O and H are expressed in ppm. Except for the components marked in the table, the remaining components are Fe and unavoidable impurities.

[0028] Table 1 Summary of component contents 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 by processing: S1. Drying the raw materials to reduce the water content of the metal materials at a temperature of 300°C for 50 hours; mixing all the raw materials according to the proportions, smelting the raw materials into molten steel by vacuum induction smelting, and then refining them by electroslag remelting to obtain electroslag ingots; S2. The electroslag ingot was forged at 1150°C and then final forged at 1050°C to achieve a forging ratio of 5.0. The final processed product was a wire rod with a size of φ5.5 mm. S3. The wire rod is solution heat treated and drawn at a temperature of 1080°C for 25 min. The wire rod is hot rolled at a temperature of 1200°C and a finishing temperature of 1150°C. S4. Repeat the steps in S3 until the processed welding wire size reaches φ2.0 mm. When the cold drawing deformation is ≥20%, the heat treatment temperature is 1150°C and the heat treatment time is 25 min. When the cold drawing deformation is ≤20%, the heat treatment temperature is 1100°C 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°C and the heat treatment time is 20 minutes.

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

[0030] Table 2 Summary of component contents 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 tough austenitic stainless steel welding wire in this embodiment are as shown in Table 3.

[0031] Table 3 Summary of component contents 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 tough austenitic stainless steel welding wire in this embodiment are as shown in Table 4.

[0032] Table 4 Summary of component contents 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 example, the welding wires prepared in Examples 1-4 were subjected to performance testing, or the performance testing was conducted on the cladding metal formed after welding the wires. For experimental methods where specific conditions are not specified, the testing is generally conducted in accordance with national standards. If no corresponding national standards exist, the testing is conducted in accordance with general international standards, conventional conditions, or conditions recommended by the manufacturer.

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

[0034] Table 5 Statistics of inclusion content of welding wires in Examples 1 to 4 under a 100X microscope Serial number <![CDATA[Average inclusion content (number / mm 2 )]]> Inclusions smaller than 3.0 μm (%) Inclusions less than 5.0 μm in size (%) 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 each group in Examples 1 to 4 were first welded to form cladding metals, which were then processed into specimens with a size of 10×10×55 mm. The mechanical properties of the specimens, such as impact absorption energy and lateral expansion value, were tested. The test results are shown in Table 6.

[0035] Table 6 Statistics of the mechanical properties test results of welding wires in Examples 1 to 4 Serial number -196℃, impact absorption energy (J) -196℃, lateral expansion value (mm) -269℃, impact absorption 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 content of the deposited metals were tested. The test results are shown in Table 7.

[0036] Table 7 Statistical table of mechanical properties test results after the welding wire forms cladding metal in Examples 1 to 4 Serial number Ferrite content (%) Room temperature, tensile strength (MPa) Room temperature, yield strength (MPa) 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 The test results in Table 5 show that, under the preparation method of the present invention, when the non-metallic inclusions of the welding wire sample are observed under a 100X microscope, the non-metallic inclusion index can meet the following requirements: average inclusion content ≤ 30 / mm 2Inclusions smaller than 3.0 μm accounted for ≥90% of the total, inclusions smaller than 5.0 μm accounted for ≥95% of the total, and inclusions larger than 15.0 μm accounted for ≤1%. Controlling the number of non-metallic inclusions improves the low-temperature performance of the material and the cladding metal formed by the welding wire, demonstrating that the preparation method of the present invention can produce qualified welding wire products.

[0037] The test results in Tables 6 and 7 show that the ferrite content of the welding wire produced by the present invention can be maintained at ≤0.5% after the cladding metal is formed. At a temperature of -269°C, the cladding metal exhibits mechanical properties of ≥1800 MPa tensile strength, ≥1200 MPa yield strength, and ≥25% elongation. At a temperature of -196°C, the cladding metal exhibits mechanical properties of ≥1200 MPa tensile strength, such as ≥800 MPa yield strength, and ≥30% elongation. At room temperature, the cladding metal exhibits mechanical properties of ≥700 MPa tensile strength, ≥350 MPa yield strength, and ≥40% elongation. Furthermore, the impact properties of the cladding metal formed by the welding wire at a low temperature of -269°C can achieve: impact absorption energy KV2 ≥80 J, lateral expansion value LE ≥1.0 mm; and at a low temperature of -196°C, the cladding metal exhibits impact absorption energy KV2 ≥100 J, lateral expansion value LE ≥1.0 mm.

[0038] Compared with the mechanical property test results of the cladding metal of the welding wire disclosed in the patent application number 202410717390.8 in the prior art, the yield strength of the cladding metal formed by the welding wire in the present invention is not weakened at -269°C, and on this basis, a significant improvement in tensile strength is achieved; at the same time, it can be seen from the test results in the present invention that the cladding metal formed by the welding wire can maintain good mechanical properties at room temperature and other more different low-temperature environments (such as a temperature environment of -196°C), thereby meeting the use requirements of different materials such as liquid nitrogen and liquid helium.

[0039] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above implementation cases, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the above implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

Claims

1. A low-temperature, high-strength, and tough austenitic stainless steel welding wire, characterized in that: Its components include by weight percentage: 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 amount of Nb and V: 0.1~0.4%, 0<Al≤0.05%, 0<Ti≤0.005%, unavoidable impurities and Fe balance, among which the ratio of Al content to Ti content is Al:Ti=(5~10):

1.

2. The low-temperature, high-strength, and tough austenitic stainless steel welding wire according to claim 1, characterized in that: The inevitable impurities in the components include O and H, with the O content controlled within 20 ppm and the H content controlled within 10 ppm.

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

4. The low-temperature, high-strength, and tough austenitic stainless steel welding wire according to claim 1, characterized in that: The total weight percentage of Ni and Mn is greater than 30%.

5. The low-temperature, high-strength, and tough austenitic stainless steel welding wire according to claim 1, characterized in that: Chromium equivalent Cr eq and nickel equivalent Ni eq The relationship is as follows: 1.2≤Cr eq / Ni eq ≤2.

0.

6. The low-temperature, high-strength, and tough austenitic stainless steel welding wire according to claim 1, characterized in that: The austenitization stability coefficient Δ is ≥ 0. The calculation formula of the austenitization stability coefficient Δ is as follows: .

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

8. A method for preparing a low-temperature, high-strength and tough austenitic stainless steel welding wire, characterized in that: The method for preparing a low-temperature, high-strength and tough austenitic stainless steel welding wire according to any one of claims 1 to 7 comprises at least the following steps: S1. The alloy raw materials are dried, all raw materials are mixed in proportion to form molten steel, and refined by electroslag remelting to prepare electroslag ingots; S2: forging the electroslag ingot into a blank, and then hot-working it into a wire rod, wherein the forging blanking temperature is 1100-1220° C., the final forging temperature is 1000-1100° C., the forging ratio of the steel ingot is ≥4.0, the hot rolling temperature is 1150-1220° C., and the final rolling temperature is 1100-1150° C.; S3: performing solution heat treatment on the wire rod, followed by drawing, wherein the heat treatment temperature is 1080-1180° C. and the heat treatment time is ≥20 min; S4: Repeat the processing steps in S3 until the size of the processed welding wire is φ1.0~2.4mm; S5: performing solution heat treatment on the welding wire, wherein the final heat treatment temperature is 1060-1140° C. and the heat treatment time is ≥10 min.

9. The method for preparing a low-temperature, high-strength and tough austenitic stainless steel welding wire according to claim 8, characterized in that: In S1, the drying temperature of each alloy raw material is 250~400℃, and the duration is ≥48 h.

10. The method for preparing a low-temperature, high-strength and tough austenitic stainless steel welding wire according to claim 8, 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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