High-strength expansion alloy welding wire and preparation method thereof

Abstract

The invention relates to a high-strength expansion alloy welding wire and a preparation method thereof, belongs to the technical field of welding materials, and solves the problems that in the prior art, the strength of a welding position is insufficient, cracks are likely to be generated, and the service life is short. The invention provides a high-strength expansion alloy welding wire. The alloy welding wire comprises, by mass, 0.20-0.30% of C, 0.60-1.00% of Mn, 0 < Si < = 0.10%, 0 < P < = 0.01%, 0 < S < = 0.01%, 0 < Al < = 0.05%, 35.50-37.50% of Ni, 0.20-0.40% of Ti, 1.40-1.60% of Nb, < = 0.002% of N, < = 0.002% of O, < = 0.001% of H and the balance Fe and inevitable impurities. A welding joint formed by the welding wire is high in strength, the tensile strength ranges from 520 MPa to 535 MPa, the yield strength ranges from 390 MPa to 410 MPa, cracks and other defects are not prone to being generated, and the welding wire can be widely applied to metal material welding in special scenes such as aerospace and the like.

Description

Technical Field

[0001] The invention relates to the technical field of welding materials, and in particular to a high-strength expansion alloy welding wire and a preparation method thereof. Background Art

[0002] Expansion alloy welding wire is a type of alloy that has some alloy elements added during the smelting process to obtain a higher cladding strength. Expansion alloy welding wire is widely used in aerospace engines and gas turbine hot end components, petroleum and chemical industry, ships and other fields. It is mainly used in extreme environments of high temperature, high pressure and corrosion resistance, and is an important high-end material.

[0003] The commonly used expansion alloy welding wire for aerospace is FeNi36. The tensile strength of the weld formed by the above welding wire is 401-432MPa, the yield strength is 251-277MPa, and it is easy to produce welding defects such as cracks, and the service life is short. With the development of industrial society, the use environment of expansion alloy welding wire materials for aerospace has put forward higher strength requirements and structural stability requirements. The welding strength and welding performance of ordinary FeNi36 welding wire can no longer meet the needs of related application scenarios. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a high-strength expansion alloy welding wire and a preparation method thereof, so as to solve at least one of the problems of insufficient strength at the welding point, easy cracking, and short service life.

[0005] The invention provides a high-strength expansion alloy welding wire. The composition of the alloy welding wire is calculated by mass percentage: C 0.20-0.30%, Mn 0.60-1.00%, 0<Si≤0.10%, P≤0.01%, S≤0.01%, 0<Al≤0.05%, Ni 35.50-37.50%, Ti 0.20-0.40%, Nb 1.40-1.60%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

[0006] Preferably, the composition of the alloy welding wire is as follows by mass percentage: C 0.22-0.28%, Mn 0.60-0.80%, 0.05%<Si≤0.10%, P≤0.01%, S≤0.01%, 0.01%<Al≤0.05%, Ni 36.00-37.50%, Ti 0.25-0.35%, Nb 1.45-1.55%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

[0007] More preferably, the composition of the alloy welding wire is, by mass percentage, C 0.25%, Mn 0.80%, Si 0.05%, P 0.007%, S 0.005%, Al 0.01%, Ni 36.50%, Ti 0.30%, Nb 1.50%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

[0008] Specifically, the tensile strength of the weld formed by welding the alloy welding wire is 520-535 MPa, and the yield strength is 390-410 MPa.

[0009] Specifically, the microstructure of the weld metal formed by welding the alloy welding wire includes austenite, Ni3Ti precipitation phase and Ni3Nb precipitation phase; wherein austenite is the matrix, and the Ni3Ti precipitation phase and Ni3Nb precipitation phase are located at the grain boundaries and in the grains of the austenite matrix.

[0010] The present invention also provides a method for preparing the alloy welding wire, which specifically comprises the following steps:

[0011] S1: Weighing and mixing according to the preset alloy welding wire formula;

[0012] S2: Put the raw materials into a vacuum induction furnace for melting, and obtain alloy metal liquid after vacuum refining;

[0013] S3: pouring the alloy metal liquid into an electrode rod in an inert gas atmosphere, and then subjecting the electrode rod to vacuum consumables to obtain a consumable ingot of the alloy;

[0014] S4: The consumable ingot is forged, rolled and cold drawn to obtain a high-strength expansion alloy welding wire product.

[0015] Furthermore, the specific operation of step S2 is: charging the raw materials into a vacuum induction furnace and melting them at 1500-1550° C., and then refining them at 1580-1610° C. and a vacuum degree of 1-3 Pa for 25-40 minutes to obtain alloy metal liquid.

[0016] Furthermore, the specific operation of the pouring process in step S3 is: pouring the alloy metal liquid into the electrode rod at 1560-1610° C. and a pouring speed of 100-200 kg / min, and the pouring process is carried out in an argon atmosphere with an argon pressure of 4000-6000 Pa.

[0017] Furthermore, the specific operation and parameters of the vacuum self-consumption link in step S3 are:

[0018] The electrode rod surface is treated to remove oxide scale and then vacuum self-consumed. In the initial stage, the current is 2.5-4.7KA, the voltage is 22.0-24.5V, and the melting rate is 2-9 drops / s; the melting rate in the smelting stage is 2.0-3.0kg / min, and the melting drop rate is 2-4 drops / s; the current in the hot capping stage is 1.5-2.0KA, and the melting rate is 1-4 drops / s.

[0019] Furthermore, the specific operations and parameters of step S4 are:

[0020] In the forging process, the starting forging temperature is 1120-1160° C., and the final forging temperature is 800-950° C.; after forging, the steel is air-cooled to room temperature to obtain an alloy rolled steel billet;

[0021] In the rolling process, the starting rolling temperature is 1100-1130°C, and the final rolling temperature is 850-950°C; air cooling is performed after rolling to obtain a cold drawn billet of the alloy;

[0022] In the cold drawing step, the cold drawing blank is cold drawn at a speed of 3 to 10 m / s to obtain a finished high-strength expansion alloy welding wire.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. The high-strength expansion alloy welding wire provided by the present invention has excellent welding performance, and the weld / weld formed has excellent mechanical properties, with a tensile strength of 520-535 MPa and a yield strength of 390-410 MPa.

[0025] Compared with the commonly used alloy welding wire, the welding wire of the present invention has a proper amount of Nb and Ti added to the alloy, so a large amount of fine Ni3Al and Ni3Nb are formed at the grain boundaries and in the grains of the alloy, which produces a pinning effect at the grain boundaries, thereby significantly improving the strength of the alloy. However, when the alloy contains more Nb and Ti, the number and size of Ni3Al and Ni3Nb are significantly increased, resulting in a weakening of the pinning effect of Ni3Al and Ni3Nb on the alloy, and a weakening of the strengthening effect on the alloy. In addition, if the size of the precipitated phase is too large, it will have an adverse effect on the hot forging plasticity of the alloy. Therefore, the Nb and Ti in the alloy must be controlled within a certain alloy range, so that the strength of the alloy can be significantly improved.

[0026] 2. The preparation method provided by the present invention is simple and easy to implement, and the existing equipment can meet the implementation requirements, and can better exert the performance of the alloy welding wire; it is not easy to produce cracks at the weld during the welding process, and the service life is improved.

[0027] The present invention uses vacuum ultra-pure smelting, vacuum self-consumption and other steps to accurately control the composition of alloy elements and reduce the impurity content in the alloy as much as possible. The reduction of impurity content in the alloy is conducive to reducing the generation of cracks at the weld, and the generation of precipitated phases during welding can greatly improve the strength of the welding wire at the weld.

[0028] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0030] Figure 1 This is a photo of the weld in Example 1. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0032] The invention provides a high-strength expansion alloy welding wire. The composition of the alloy welding wire is calculated by mass percentage: C 0.20-0.30%, Mn 0.60-1.00%, 0<Si≤0.10%, P≤0.01%, S≤0.01%, 0<Al≤0.05%, Ni 35.50-37.50%, Ti 0.20-0.40%, Nb 1.40-1.60%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

[0033] The role / synergy and content of each component are determined based on the following:

[0034] C: As a strong austenite forming and austenite diffusion element, the austenite forming ability of C is about 30 times that of metal Ni. As an interstitial element, C can significantly improve the strength of the alloy through solid solution strengthening, and the addition of C can also improve the stress corrosion resistance of the alloy in a high concentration chloride environment. However, too high C content will greatly reduce the toughness of the alloy, and too high C content will cause excessive stress in the alloy after hot working, and annealing is required in time, otherwise the alloy will crack due to excessive thermal stress. Therefore, the C content of the present invention is 0.20-0.30%.

[0035] Mn: As a stabilizing element of austenite, adding appropriate Mn elements to the alloy can appropriately improve the thermoplasticity of the alloy, and Mn combines with S in the alloy to form MnS, which further reduces the S content in the alloy, thereby removing the harmful effects of S in the alloy. However, if the Mn content in the alloy is too high, the MnS content will cause the alloy's resistance to chloride pitting corrosion and crevice corrosion to decrease. Therefore, the Mn content of the present invention is 0.60-1.00%.

[0036] Si: As a substitution strengthening element, adding a small amount of Si to the alloy can improve the strength of the alloy. Moreover, as a deoxidizing element, a small amount of Si in the alloy can effectively reduce the oxygen content in the alloy. Appropriate Si can form a layer of Si-containing oxide film on the surface of the alloy, which can make the alloy have excellent nitric acid corrosion resistance. However, if the Si content in the alloy is too high, the thermoplasticity of the alloy will be deteriorated, and the cracking risk of the alloy during hot working will be increased. Therefore, the Si content of the present invention is 0<Si≤0.10%.

[0037] P: As an impurity element, excessive P content in the alloy significantly reduces the toughness and plasticity of the alloy, especially at low temperatures, causing cold brittleness. Moreover, P will significantly reduce the alloy's resistance to various concentrated nitric acid corrosion, increase the sensitivity of the solid solution alloy to intergranular corrosion in concentrated nitric acid and chloride ion environments, thereby reducing the corrosion resistance of the alloy under these conditions. Therefore, if production costs and technology allow, the P content in the alloy is reduced as much as possible, so the P content of the present invention is P≤0.01%.

[0038] S: As an impurity element, S element will reduce the plasticity of the alloy, because S has very low solubility in solid Fe and can hardly be dissolved. It exists in the alloy in the form of FeS, and FeS and Fe easily form a eutectic with a low melting point (only 985°C). When the steel is hot-worked at 1100-1200°C, the low-melting-point eutectic distributed at the grain boundary melts and causes cracking, which is the so-called "hot brittleness" phenomenon of S, which seriously affects the hot working performance of the alloy. Therefore, the P content of the present invention is S≤0.01%.

[0039] Al: As a strong deoxidizing element, the addition of Al in the alloy can effectively remove oxygen in the alloy and improve the purity of the alloy. However, adding too much Al in the alloy will cause a large amount of residual Al2O3, which will cause cracking during the hot working process of the alloy. Therefore, the Al content of the present invention is 0<Al≤0.05%;

[0040] Ni: As a core element of the alloy, it reduces the expansion coefficient of the alloy. Too much or too little Ni content in the alloy has an adverse effect on the expansion coefficient of the alloy. Therefore, the Ni content of the present invention is 35.50% to 37.50%;

[0041] Nb, Ti: as strengthening elements, adding appropriate amount of Nb and Ti to the alloy will form a large number of fine Ni3Al and Ni3Nb at the grain boundary of the alloy, producing a pinning effect at the grain boundary, thereby significantly improving the strength of the alloy. However, when the alloy contains more Nb and Ti, the number and volume of Ni3Al and Ni3Nb are significantly increased, resulting in the weakening of the pinning effect of Ni3Al and Ni3Nb on the alloy, weakening the strengthening effect of the alloy, and the excessive size of the precipitated phase will have an adverse effect on the hot forging plasticity of the alloy. Therefore, the Nb content of the present invention is 1.40% to 1.60%, and the Ti content is 0.20% to 0.40%;

[0042] O, N, H: As impurity gas elements, O and N elements in the alloy are easy to form oxides and nitrides with the metal elements in the alloy, which reduces the purity of the alloy. The higher the content of oxides and nitrides in the alloy, the more unfavorable the processing thermoplasticity of the alloy. Excessive H elements in the alloy, H atoms penetrate into the metal and recombined into hydrogen molecules inside the metal, causing stress concentration. When this stress exceeds the strength limit of the metal, fine cracks will form inside the metal, causing embrittlement or even cracking of the metal material. Therefore, the lower the gas elements in the alloy, the better. Under the condition of comprehensive production cost, the invention's O content is ≤0.002%, N content is ≤0.002%, and H content is ≤0.001%;

[0043] The reasonable combination of the above elements can ensure the low expansion, high strength, good hot workability and purity of the alloy. The chemical composition of this alloy design, a small amount of Si and Al in the alloy can effectively reduce the gas content in the alloy. The low gas content in the alloy ensures the purity of the alloy, and with the appropriate amount of Mn content, it doubles to ensure the excellent thermoplasticity of the alloy. P and S in the alloy as impurity elements should be reduced as much as possible. The appropriate Ni content in the alloy can ensure its low expansion. By adding a certain amount of Nb and Ti, a certain amount of Ni3Ti and Ni is generated in the alloy. x Nb causes these two fine precipitates to be generated in large quantities at the grain boundaries of the alloy, which have a strong pinning effect on the alloy crystals, thereby improving the strength of the alloy. However, when the Nb and Ti contents increase to a certain level, the number and size of the precipitates at the grain boundaries in the alloy will increase significantly, significantly reducing their pinning effect. Therefore, through the above chemical composition design, the low expansion and high strength of the weld of the alloy welding wire can be effectively guaranteed, thereby meeting the high requirements of related application fields.

[0044] Preferably, the composition of the alloy welding wire is as follows by mass percentage: C 0.22-0.28%, Mn 0.60-0.80%, 0.05%<Si≤0.10%, P≤0.01%, S≤0.01%, 0.01%<Al≤0.05%, Ni 36.00-37.50%, Ti 0.25-0.35%, Nb 1.45-1.55%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

[0045] More preferably, the composition of the alloy welding wire is, by mass percentage, C 0.25%, Mn 0.80%, Si 0.05%, P 0.007%, S 0.005%, Al 0.01%, Ni 36.50%, Ti 0.30%, Nb 1.50%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

[0046] Specifically, the tensile strength of the weld formed by welding the alloy welding wire is 520-535 MPa, and the yield strength is 390-410 MPa.

[0047] Specifically, the microstructure of the weld metal formed by welding the alloy welding wire includes austenite, Ni3Ti precipitation phase and Ni3Nb precipitation phase; wherein austenite is the matrix, and the Ni3Ti precipitation phase and Ni3Nb precipitation phase are located at the grain boundaries and in the grains of the austenite matrix.

[0048] It is worth noting that the main organizational structure of the weld metal is face-centered cubic austenite. Since the welding wire contains a certain amount of Ti and Nb, precipitation phases such as Ni3Ti and Ni3Nb will be generated in the austenite organizational structure, which will strengthen the weld metal organization by precipitation phases and improve its cladding strength.

[0049] The present invention also provides a method for preparing the alloy welding wire, which specifically comprises the following steps:

[0050] S1: Weighing and mixing according to the preset alloy welding wire formula;

[0051] S2: Put the raw materials into a vacuum induction furnace for melting, and obtain alloy metal liquid after vacuum refining;

[0052] S3: pouring the alloy metal liquid into an electrode rod in an inert gas atmosphere, and then subjecting the electrode rod to vacuum consumables to obtain a consumable ingot of the alloy;

[0053] S4: The consumable ingot is forged, rolled and cold drawn to obtain a high-strength expansion alloy welding wire product.

[0054] Specifically, during the vacuum induction process, properly controlling the refining time can effectively remove the impurity content of the alloy, promote the uniform distribution of each chemical component, avoid component segregation, and make the performance of the alloy consistent without too much deviation; vacuum self-consumption is to further remove the gas in the alloy and improve the purity of the alloy.

[0055] Further, the specific operation of step S2 is: each raw material is loaded into a vacuum induction furnace and melted at 1500-1550°C, and then refined for 25-40 minutes at 1580-1610°C and a vacuum degree of 1-3Pa to obtain alloy metal liquid. Generally, the vacuum degree of the vacuum induction refining period is as low as possible under the condition that the equipment allows, but 1-3Pa is appropriate considering the production cost; the refining time and refining temperature should not be too high (too long) or too low (too short), because the refining time and refining temperature are also too high (too long) will cause the gas and impurities in the crucible to enter the alloy, while too low (too short) will cause the alloy to remove impurities and gases insufficiently, which will affect the purity of the alloy and further affect the subsequent weld performance.

[0056] Furthermore, the specific operation of the pouring link in step S3 is: pouring the alloy metal liquid into the electrode rod at 1560-1610°C and a pouring speed of 100-200kg / min, and the pouring process is carried out in an argon atmosphere with an argon pressure of 4000-6000 Pa. The pouring temperature needs to be controlled within a certain range. If the pouring temperature is too high, the mold will be burned, and if it is too low, the fluidity of the molten steel will be reduced; if the argon filling pressure during the pouring process is too low, it cannot fully play the role of protecting the pouring, and if the pressure is too high, it will cause a waste of argon and increase production costs.

[0057] Furthermore, the specific operation and parameters of the vacuum self-consumption link in step S3 are:

[0058] After the surface of the electrode rod is descaled, vacuum consumable is performed. The current in the initial stage is 2.5-4.7KA, the voltage is 22.0-24.5V, and the melting rate is 2-9 drops / s; the melting rate in the smelting stage is 2.0-3.0kg / min, and the melting drop rate is 2-4 drops / s; the current in the hot capping stage is 1.5-2.0KA, and the melting rate is 1-4 drops / s. The melting rate in the smelting and melting stage cannot be too fast or too slow. A too fast melting rate will cause a deeper molten pool and aggravate the component segregation. A too slow melting rate will cause a shallow molten pool and reduce the surface quality of the consumable ingot.

[0059] Furthermore, the specific operations and parameters of step S4 are:

[0060] In the forging process, the starting forging temperature is 1120-1160° C., and the final forging temperature is 800-950° C.; after forging, the alloy is air-cooled to room temperature to obtain a rolled steel billet of the alloy; if the starting forging temperature is too high, the alloy will be overheated and prone to cracking during forging, while if the starting forging temperature is too low, the alloy will have poor forging plasticity; if the final forging temperature is too high, heat will be wasted, while if the final forging temperature is too low, the alloy will not be able to fully recover and recrystallize, affecting the microstructure and properties of the alloy.

[0061] In the rolling process, the starting rolling temperature is 1100-1130°C, and the final rolling temperature is 850-950°C; air cooling is performed after rolling to obtain a cold-drawn billet of the alloy; if the starting rolling temperature is too high, the alloy will be overheated and prone to cracking, while if the starting rolling temperature is too low, the alloy will have poor plasticity; if the final rolling temperature is too high, heat will be wasted, while if the final rolling temperature is too low, the alloy will not be able to fully recover and recrystallize, affecting the microstructure and properties of the alloy.

[0062] In the cold drawing step, the cold drawing blank is cold drawn at a speed of 3 to 10 m / s to obtain a finished high-strength expansion alloy welding wire.

[0063] Examples and Comparative Examples

[0064] The welding wire formulas of various embodiments and comparative examples are shown in Table 1.

[0065] Table 1 Welding wire formulas of various embodiments and comparative examples

[0066] element C Mn Si S P Al Ni Ti Nb O N H Example 1 0.23 0.62 0.052 0.004 0.001 0.03 36.1 0.25 1.46 0.0008 0.0007 0.0002 Example 2 0.23 0.63 0.05 0.003 0.001 0.03 36.3 0.26 1.48 0.0006 0.0006 0.0003 Example 3 0.25 0.65 0.06 0.003 0.001 0.01 36.5 0.28 1.47 0.0006 0.0006 0.0003 Example 4 0.26 0.71 0.05 0.002 0.002 0.02 36.8 0.29 1.49 0.00055 0.0005 0.00035 Example 5 0.27 0.73 0.07 0.003 0.002 0.02 37.1 0.32 1.51 0.0005 0.0005 0.00025 Example 6 0.28 0.74 0.07 0.003 0.0015 0.01 37.4 0.33 1.52 0.0004 0.00055 0.0003 Example 7 0.28 0.79 0.09 0.002 0.0016 0.015 37.4 0.34 1.53 0.0004 0.0005 0.0003 Comparative Example 1 0.01 0.43 0.12 0.003 0.002 / 36.2 / / 0.0006 0.0006 0.0003 Comparative Example 2 0.01 0.45 0.15 0.003 0.0024 / 36.4 / / 0.0005 0.0007 0.0004 Comparative Example 3 0.01 0.49 0.26 0.002 0.0019 / 36.6 / / 0.00055 0.0005 0.00035 Comparative Example 4 0.01 0.51 0.23 0.002 0.0014 / 36.5 0.56 1.89 0.00055 0.0006 0.0003 Comparative Example 5 0.23 0.63 0.05 0.003 0.001 0.03 36.6 0.61 1.78 0.00065 0.0005 0.0004

[0067] It is worth noting that the performance improvement of the welding wire provided by the present invention is mainly based on the composition design, and the role of the preparation process and supporting parameters is mainly to ensure the purity of the welding wire and accurately control the composition. In other words, if the welding wire composition ratio can be guaranteed to be accurate and the purity is high, other technologies can also be used to prepare the welding wire, and it is not limited to the preparation method provided by the present invention; but it is worth noting that the preparation method provided by the present invention is one of the best solutions that can give full play to the performance of the welding wire, and the value within the above range can obtain a welding wire with better purity.

[0068] The specific preparation process of each embodiment and comparative example is as follows:

[0069] S1: Weighing and mixing according to the preset alloy welding wire formula;

[0070] S2: The raw materials are placed in a vacuum induction furnace and melted at 1550° C., and then refined at 1580° C. and a vacuum degree of 1 to 3 Pa for 30 min to obtain a molten alloy;

[0071] S3: pouring the alloy metal liquid into an electrode rod at 1580° C. and a pouring speed of 150 kg / min, the pouring process is carried out in an argon atmosphere with an argon pressure of 5000 Pa;

[0072] The electrode rod surface is treated to remove oxide scale and then subjected to vacuum consumable treatment. The current in the initial stage is 3.5KA, the voltage is 23.0V, and the melting rate is 5 drops / s; the melting rate in the smelting stage is 2.5kg / min, and the melting drop rate is 3 drops / s; the current in the hot capping stage is 1.8KA, and the melting rate is 2 drops / s, to obtain a consumable ingot of the alloy;

[0073] S4: Forging stage, starting forging temperature is 1140℃, final forging temperature is 850℃; after forging, air cooling to room temperature is performed to obtain the alloy rolled steel billet; rolling stage, starting rolling temperature is 1120℃, final rolling temperature is 900℃; after rolling, air cooling is performed to obtain the alloy cold drawn billet; in the cold drawing stage, the cold drawn billet is cold drawn at a cold drawing speed of 5m / s to obtain a high-strength expansion alloy welding wire product.

[0074] The alloy welding wire in the embodiment and the comparative example was used to weld a 3 mm thick FeNi36 alloy steel plate. The welding process and parameters are as follows: the welding wire was tested and compared using argon arc welding: the shielding gas was 100% pure argon, the gas flow rate was 25 L / min, the welding current was 100 A, the welding voltage was 28 V, and the welding speed was 100 mm / min. The mechanical properties of the weld were then tested, and the test results are shown in Table 2.

[0075] Table 2 Mechanical properties characterization results of welding points of various embodiments and comparative examples

[0076] Rm / MPa <![CDATA[Rp 0.2 / MPa]]> Example 1 520 390 Example 2 523 393 Example 3 524 395 Example 4 523 396 Example 5 529 396 Example 6 532 402 Example 7 535 410 Comparative Example 1 401 251 Comparative Example 2 415 267 Comparative Example 3 432 277 Comparative Example 4 454 310 Comparative Example 5 542 313

[0077] In summary: the tensile strength of the welding wire of the present invention is generally maintained at about 525MPa, tensile strength ≥ 520MPa), and the yield strength is about 395MPa, yield strength ≥ 390MPa. The tensile strength of the conventional welding wire is about 420MPa, and the yield strength is about 267MPa. Among them, in Comparative Examples 4 and 5, due to the excessive addition of Ti and Nb, although the tensile strength is improved compared with the conventional welding wire, the yield strength is significantly lower than that of the embodiment.

[0078] The welding wire cladding strength (strength at the weld) of the present invention is significantly higher than the cladding strength of the conventional alloy welding wire. Appropriate Nb and Ti elements are added to the alloy of the present invention, and a large number of fine Ni3Ti and Ni3Nb precipitates can be generated in the alloy, thereby fully exerting their pinning effect; however, when the number and size of precipitates such as Ni3Ti and Ni3Nb increase to a certain extent, their pinning effect will be weakened, because as the size of the precipitates increases, the bypass mechanism of the precipitates will be triggered (such as Comparative Examples 4 and 5), so the content of Nb and Ti elements needs to be controlled within a certain range.

[0079] It is worth emphasizing that, although Comparative Examples 4 and 5 (especially Comparative Example 5) focus on the effects of Nb and Ti additions, the performance of the welding wire provided by the present invention is determined by the synergistic effect of the components and is not limited to the addition and content adjustment of Nb and Ti.

[0080] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-strength expansion alloy welding wire, characterized in that: The composition of the alloy welding wire is calculated by mass percentage: C 0.20-0.30%, Mn 0.60-1.00%, 0<Si≤0.10%, P≤0.01%, S≤0.01%, 0<Al≤0.05%, Ni 35.50-37.50%, Ti 0.20-0.40%, Nb 1.40-1.60%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

2. The alloy welding wire according to claim 1, characterized in that: The composition of the alloy welding wire is calculated by mass percentage: C 0.22-0.28%, Mn 0.60-0.80%, 0.05%<Si≤0.10%, P≤0.01%, S≤0.01%, 0.01%<Al≤0.05%, Ni 36.00-37.50%, Ti 0.25-0.35%, Nb 1.45-1.55%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

3. The alloy welding wire according to claim 1, characterized in that: The composition of the alloy welding wire is as follows by mass percentage: C 0.25%, Mn 0.80%, Si 0.05%, P 0.007%, S 0.005%, Al 0.01%, Ni 36.50%, Ti0.30%, Nb 1.50%, N≤0.002%, O≤0.002%, H≤0.001%, and the rest is Fe and unavoidable impurities.

4. The alloy welding wire according to claim 1, characterized in that: The tensile strength of the weld formed by welding the alloy welding wire is 520-535 MPa, and the yield strength is 390-410 MPa.

5. The alloy welding wire according to claim 1, characterized in that: The microstructure of the weld metal formed by welding the alloy welding wire includes austenite, Ni3Ti precipitation phase and Ni3Nb precipitation phase; wherein austenite is the matrix, and the Ni3Ti precipitation phase and Ni3Nb precipitation phase are located at the grain boundaries and in the grains of the austenite matrix.

6. A method for preparing the alloy welding wire according to any one of claims 1 to 5, characterized in that: The specific steps include: S1: Weighing and batching according to the preset alloy welding wire formula; S2: Put the raw materials into a vacuum induction furnace for melting, and obtain alloy metal liquid after vacuum refining; S3: pouring the alloy metal liquid into an electrode rod in an inert gas atmosphere, and then subjecting the electrode rod to vacuum consumables to obtain a consumable ingot of the alloy; S4: The consumable ingot is forged, rolled and cold drawn to obtain a high-strength expansion alloy welding wire product.

7. The preparation method according to claim 6, characterized in that: The specific operation of step S2 is: loading the raw materials into a vacuum induction furnace and melting them at 1500-1550° C., and then refining them at 1580-1610° C. and a vacuum degree of 1-3 Pa for 25-40 minutes to obtain alloy metal liquid.

8. The preparation method according to claim 6, characterized in that: The specific operation of the pouring link in step S3 is: pouring the alloy metal liquid into the electrode rod at 1560-1610° C. and a pouring speed of 100-200 kg / min, and the pouring process is carried out in an argon atmosphere with an argon pressure of 4000-6000 Pa.

9. The preparation method according to claim 6, characterized in that: The specific operation and parameters of the vacuum self-consumption link in step S3 are: The electrode rod surface is treated to remove oxide scale and then vacuum self-consumed. In the initial stage, the current is 2.5-4.7KA, the voltage is 22.0-24.5V, and the melting rate is 2-9 drops / s; the melting rate in the smelting stage is 2.0-3.0kg / min, and the melting drop rate is 2-4 drops / s; the current in the hot capping stage is 1.5-2.0KA, and the melting rate is 1-4 drops / s.

10. The preparation method according to claim 6, characterized in that: The specific operations and parameters of step S4 are: In the forging, the starting forging temperature is 1120-1160° C., and the final forging temperature is 800-950° C.; after forging, the steel is air-cooled to room temperature to obtain an alloy rolled steel billet; In the rolling, the starting rolling temperature is 1100-1130°C, and the final rolling temperature is 850-950°C; air cooling is performed after rolling to obtain a cold drawn billet of the alloy; In the cold drawing, the cold-drawn blank is cold-drawn at a speed of 3 to 10 m / s to obtain a finished high-strength expansion alloy welding wire.

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