Iron-nickel alloy welding wire for liquefied gas equipment welding and manufacturing method thereof

Abstract

The application discloses an iron-nickel alloy welding wire for liquefied gas equipment welding and a manufacturing method thereof, and the chemical components of the iron-nickel alloy welding wire are as follows in percentage by weight: 34.5%<=Ni<=37.5%, 0.040%<=C<=0.080%, 0.01%<=Si<=0.30%, 0.1%<=Mn<=0.6%, P<=0.0030%, S<=0.0015%, O<=0.0030%, N<=0.0020%, 0.0010%<=Mg<=0.0040%, 0.0005%<=Al<=0.0040%, 0.0001%<=V<=0.0020%, 0.0001%<=Ti<=0.0020%, 0.0001%<=Nb<=0.0020%, 0.0001%<=Ca<=0.0020%, B<=0.0010%, and the balance is Fe and inevitable impurities, and the iron-nickel alloy welding wire has excellent low-temperature use performance.

Description

Technical Field

[0001] This invention relates to iron-nickel alloy welding wire technology, and more specifically, to an iron-nickel alloy welding wire for welding liquefied gas equipment and its manufacturing method, which has excellent low-temperature performance. Background Technology

[0002] Currently, the main liquefied gases used in cryogenic gas transport equipment include liquefied ammonia, liquefied carbon dioxide, liquefied ethane, liquefied hydrogen, and liquefied methane. To ensure the safety of filling and transporting liquefied gases, transport components typically need to possess suitable cryogenic expansion properties and excellent cryogenic impact toughness. To meet the structural performance requirements after welding, traditional welding wires require special design.

[0003] Chinese Patent Publication No. CN103084753A discloses a nickel-iron precision alloy welding wire with the following chemical composition by mass percentage: C 0.1~0.18%, Mn 0.4~0.5%, Si 0.2~0.3%, Ni 35~37%, Ti 0.4~0.5%, Nb 1.12~1.2%, S≤0.005%, P≤0.01%, with the remainder being Fe and unavoidable impurities; wherein, C / (Nb+Ti)<0.2; and the performance indicators of the deposited metal are: tensile strength (Rm)≥480MPa, and impact toughness AKV2 at 20℃≥50J / cm. 2 The coefficient of linear expansion at 20~100℃ is ≤1.2×10⁻⁶. -6 / ℃, for the use of weld metal at room temperature, Ti and Nb are used to strengthen the weld metal, thereby improving the strength and toughness of the weld metal; however, the nickel-iron precision alloy welding wire studied in this technology is more focused on the performance at room temperature, and the performance of the weld under low temperature conditions (such as the thermal expansion performance at -180℃~0℃ and the impact performance at -198℃) has not been studied.

[0004] Chinese Patent Publication No. CN107866647A discloses an Fe-Ni Invar alloy welding wire and its manufacturing method. The chemical composition by weight ratio is: C: 0.04~0.10%, Si≤0.25%, Mn: 0.2~0.4%, P≤0.08%, S≤0.003%, Ni: 35~38%, Cr: 0.2~0.5%, V: 0.08~0.15%, with the remainder being Fe and unavoidable impurities. This technology improves the strength and toughness of the weld metal by increasing the C content and appropriately adding elements such as Cr and V, relying on carbide strengthening and solid solution strengthening, while ensuring low expansion performance. This technology mainly strengthens grain boundaries through Cr and V carbides and focuses only on room temperature performance. However, the presence of a large number of coarse carbides deteriorates the low-temperature impact performance of the material, becoming a crack initiation point. Therefore, this Fe-Ni Invar alloy welding wire is not suitable for welding in cryogenic liquefied gas equipment.

[0005] In summary, current techniques for designing low-expansion alloy welding wires involve adding strong carbide-forming elements to create dispersed carbides in the matrix. This strengthens the wire through precipitation and improves toughness by refining the grain size. However, this approach is limited to enhancing the strength and toughness of the welding wire itself, and its effect on improving the low-temperature toughness of the weld cladding metal is very limited. This is because after welding and cladding, the welding wire first melts into a liquid metal and then cools into a cast structure, characterized by coarse dendrites. These dispersed carbides cannot effectively refine the grain size to improve toughness. On the contrary, excessive carbide precipitation at grain boundaries can reduce grain boundary bonding and decrease low-temperature impact toughness.

[0006] In view of the above, it is necessary to study a welding wire with excellent low-temperature performance that can meet the high comprehensive performance requirements of cryogenic liquefied gas transport components. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an iron-nickel alloy welding wire for welding liquefied gas equipment and its manufacturing method. By increasing the carbon content in the welding wire, appropriately adding Mg, reducing the Al content, and controlling the S, P, O, and N content within a low range, the low-temperature expansion performance of the iron-nickel alloy welding wire is ensured, and the low-temperature impact performance of the weld cladding metal after welding is improved, thus meeting the high comprehensive performance requirements of cryogenic liquefied gas transportation components.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] The first aspect of the present invention provides an iron-nickel alloy welding wire for welding liquefied gas equipment, the chemical composition of which, by weight percentage, is as follows: 34.5%≤Ni≤37.5%, 0.040%≤C≤0.080%, 0.01%≤Si≤0.30%, 0.1%≤Mn≤0.6%, P≤0.0030%, S≤0.0015%, O≤0.0030%, N≤0.0020%, 0.0010%≤Mg≤0.0040%, 0.0005%≤Al≤0.0040%, 0.0001%≤V≤0.0020%, 0.0001%≤Ti≤0.0020%, 0.0001%≤Nb≤0.0020%, 0.0001%≤Ca≤0.0020%, B≤0.0010%, with the balance including Fe and unavoidable impurities;

[0010] The weight percentage of the chemical composition of the iron-nickel alloy welding wire also satisfies the following formula:

[0011] -0.005%≤S1≤0.005%

[0012] S1=C / 20+Al / 3×2+Mg×2+Ca+V / 3+Ti / 6+Nb / 6-O×3-N×3.

[0013] Preferably, 0.003%≤S1≤0.004%.

[0014] Preferably, the chemical composition of the iron-nickel alloy welding wire also satisfies the following: 0.2%≤Mn≤0.5%, 0.001%≤Al≤0.004%, 0.0002%≤V≤0.0020%, 0.0002%≤Ti≤0.0020%, and 0.0002%≤Nb≤0.0020%.

[0015] Preferably, the coefficient of thermal expansion of the iron-nickel alloy welding wire between -180℃ and 0℃ is (1.0~2.0)×10⁻¹⁰. -6 m / m / ℃.

[0016] Preferably, the coefficient of thermal expansion of the iron-nickel alloy welding wire between -180℃ and 0℃ is (1.2~1.8)×10⁻¹⁰. -6 m / m / ℃.

[0017] Preferably, the weld cladding metal after welding with the iron-nickel alloy welding wire exhibits a V-shaped impact toughness ≥150 J / cm² at -196°C. -2 .

[0018] Preferably, the weld cladding metal after welding with the iron-nickel alloy welding wire exhibits a V-shaped impact toughness of 155~178 J / cm² at -196°C. -2 .

[0019] The composition design principle of the iron-nickel alloy welding wire of the present invention is as follows:

[0020] C plays a crucial role in this invention. First, increasing the C content significantly increases the solid-liquid phase line spacing, expanding the material's solidification temperature range, thereby reducing the solute equilibrium distribution coefficient K0 and increasing the material's supercooling, which is beneficial for the rapid solidification of the liquid film in the final stage of welding. This also prevents microcracks from forming under welding thermal stress due to the presence of the liquid film, thus improving the material's low-temperature impact toughness. Second, as a strong oxidizing element, C can produce a strong deoxidizing effect during welding, and the deoxidation product is gaseous CO2, which can be eliminated during the welding process. Compared to elements such as Al, Mg, and Ca, it does not produce oxide inclusions during deoxidation, achieving both deoxidation and purification simultaneously. Research in this invention has shown that when the C content is ≥0.04%, the expansion of the material's solidification temperature range and the deoxidation effect are particularly significant. This can significantly improve the weld solidification structure, reduce the O content in the weld cladding metal, and reduce the level of inclusions in the weld cladding metal, thereby improving the quality of the weld cladding metal and significantly enhancing its low-temperature impact performance. When the C content is higher than 0.08%, it significantly increases the material's coefficient of thermal expansion, worsening its expansion performance. Therefore, the present invention controls the C content to be between 0.04% and 0.08%.

[0021] Ni is an important alloying element that ensures the alloy has low expansion properties. Therefore, the present invention controls the Ni content to be between 34.5% and 37.5%.

[0022] Mn: Ensures the weld metal has a certain strength after welding. At the same time, Mn can react with S and O to form MnS and MnO, which have the functions of desulfurization and deoxidation, reducing hot cracking caused by S. However, too high Mn content will cause the weld to become brittle and the toughness to deteriorate. Therefore, the present invention controls the Mn content to be 0.1%~0.6%, preferably 0.2%~0.5%.

[0023] Si is the deoxidizing element in welding wire. Since deoxidation with Mn alone produces MnO, which has a high density and is difficult to float from the molten pool, a certain amount of Si must be added to the welding wire to jointly deoxidize with Mn, forming SiO and MnO composite silicates (MnO•SiO). These silicates can agglomerate into large slag masses in the molten pool and float to the surface, achieving a good deoxidation effect. However, as the Si content increases, low-melting-point eutectics are easily formed, leading to welding hot cracks. Simultaneously, higher Si content can form silicate inclusions, reducing the impact toughness of the weld. Therefore, this invention controls the Si content to be between 0.01% and 0.30%.

[0024] Al is an important deoxidizing element. Too low an Al content results in poor deoxidation during alloy smelting, deteriorating the material's thermoplasticity and leading to welding hot cracks. Simultaneously, too low an Al content worsens the deoxidation reaction in the molten pool during welding, resulting in excessively high O content in the weld metal and deteriorating the weld's impact toughness. Too high an Al content leads to the formation of Al oxides, negatively impacting the alloy's purity and causing hot cracks in the weld metal area during welding, further deteriorating the weld's impact toughness. AlO inclusions significantly reduce the material's impact performance, especially under low-temperature impact. Therefore, while ensuring effective deoxidation, it is crucial to minimize Al content and AlO inclusions. This invention has found that, while increasing C content to improve deoxidation strength, appropriately reducing Al content can also guarantee effective deoxidation of the molten metal during smelting and welding. Therefore, this invention controls the Al content to be between 0.0005% and 0.0040%, preferably between 0.001% and 0.0018%.

[0025] Mg is an important deoxidizing element. Too low a Mg content results in poor deoxidation during alloy smelting, deteriorating the material's thermoplasticity and leading to welding hot cracks. Simultaneously, too low a Mg content worsens the deoxidation reaction in the molten pool during welding, resulting in excessively high O content in the weld metal and deteriorating the weld's impact toughness. Too high a Mg content leads to the formation of Mg oxides, negatively impacting the alloy's purity and causing hot cracks in the weld metal area during welding, further deteriorating the weld's impact toughness. Mg and Al are both strong oxide-forming elements and have similar effects. However, this invention has found that when using Mg for deoxidation, the size of the deoxidation product MgO is approximately 1 / 10 to 1 / 5 the size of AlO inclusions. By increasing the Mg content and decreasing the Al content, the size of the deoxidation product can be significantly refined, reducing the sensitivity of the weld metal to welding thermal stress and significantly reducing the generation of welding hot cracks, thereby improving the low-temperature impact toughness of the weld metal. Therefore, this invention controls the Mg content to be between 0.0010% and 0.0040%.

[0026] Ca (Ca) is an important deoxidizing and desulfurizing element. If the Ca content is too low, the deoxidation effect in the alloy will be poor, deteriorating the material's thermoplasticity and leading to welding hot cracks. Simultaneously, a low Ca content will worsen the deoxidation reaction in the molten pool during welding, resulting in excessively high O content in the weld metal and deteriorating the weld's impact toughness. If the Ca content is too high, Ca oxides will form, adversely affecting the alloy's purity and causing hot cracks in the weld metal area during welding, further deteriorating the weld's impact toughness. Furthermore, a low Ca content will result in poor desulfurization. Therefore, this invention controls the Ca content to be between 0.0001% and 0.0020%.

[0027] O: O in the alloy can form alumina inclusions, silicate inclusions, and spherical oxide inclusions with Mg, Al, Ca, Ti, and Si, which deteriorates the alloy purity and leads to hot cracking in the cladding metal during welding, adversely affecting the low-temperature impact toughness of the weld. Therefore, this invention controls the O content to ≤0.0030%.

[0028] Nitrogen (N) in the alloy can form nitrides with B, Al, Ti, and V, resulting in precipitates within the grains or at grain boundaries. This deteriorates the alloy's purity, leading to hot cracking in the cladding metal during welding and worsening the low-temperature impact toughness of the weld. Therefore, this invention controls the N content to ≤0.0020%.

[0029] V, Ti, and Nb are strong carbide-forming elements. Excessive V, Ti, and Nb will form carbides with C, reducing the deoxidation effect of C during welding. Therefore, this invention controls the V content to be 0.0001%~0.0020%, the Ti content to be 0.0001%~0.0020%, and the Nb content to be 0.0001%~0.0020%; preferably, the V content to be 0.0002%~0.0020%, the Ti content to be 0.0002%~0.0020%, and the Nb content to be 0.0002%~0.0020%.

[0030] B: In this invention, it is a harmful impurity that can combine with nitrogen (N) in the alloy to form BN inclusions, which have a very adverse effect on the low-temperature impact performance of the weld. Therefore, the B content is controlled to be ≤0.0010% in this invention.

[0031] P: In this invention, P is a harmful impurity that reduces the strength and toughness at the interface, leading to hot cracking in the cladding metal during welding and thus reducing the low-temperature impact toughness of the alloy weld. Therefore, this invention controls the P content to ≤0.0030%.

[0032] S: In this invention, S is a harmful impurity that reduces the strength and toughness at the interface, leading to hot cracking in the cladding metal during welding and thus reducing the low-temperature impact toughness of the alloy weld. Therefore, this invention controls the S content to ≤0.0015%.

[0033] Due to the specific nature of welding wire, traditional methods to improve the impact toughness of the cladding metal after welding often involve reducing harmful sulfur (S) and phosphorus (P) elements, and adding a certain amount of manganese (Mn) to reduce the formation of low-melting-point substances at grain boundaries, thereby improving grain boundary strength and impact performance. Alternatively, vacuum degassing or the addition of deoxidizing elements can reduce the O and N gas content in the welding wire to improve the impact toughness of the cladding metal after welding. However, welding wires that reduce O and N gas content through vacuum degassing only reduce the O and N content in the base material; this is a preparatory measure for increasing the O and N content of the cladding metal after welding. It cannot prevent the addition of O during the welding process, leading to an increase in the gas content of the cladding metal after welding. This invention reveals that while adding deoxidizing elements such as Al, Mg, and Ca can effectively reduce the gas content in metals during smelting and welding, it cannot prevent the formation of deoxidation products such as AlO, MgO, and CaO during the deoxidation process. These deoxidation products, especially coarse AlO, have poor ability to coordinate deformation with the matrix and are prone to generating welding hot cracks at the interface under welding thermal stress, which adversely affects the low-temperature impact performance of the welded cladding metal.

[0034] The present invention has found that simply reducing the content of S, P, O and N elements through the smelting process, even if the content of the welding wire base material itself is very low, cannot guarantee that the cladding metal after welding will achieve the high impact toughness expected by the present invention. Avoiding the increase of gas content after welding is the ultimate means to improve the impact toughness of the cladding metal after welding.

[0035] Therefore, this invention, building upon previous methods that improved the purity of the welding wire and reduced harmful elements like sulfur (S) and phosphorus (P), primarily increases the carbon (C) content in the welding wire. This increases the material's supercooling, accelerates solidification during welding, and prevents the formation of a liquid film, thereby avoiding microcracks under welding thermal stress. Simultaneously, increasing the C content, as the primary deoxidizing element, prevents the formation of deoxidation products. Appropriate addition of magnesium (Mg) and a reduction in the al (Al) content ensure effective deoxidation while forming fine Mg deoxidation products, reducing coarse AlO deoxidation products, minimizing stress concentration during welding, and effectively preventing welding hot cracks.

[0036] While avoiding the formation of oxide and nitride inclusions, and to ensure the degassing effect of the material, this invention further controls the weight percentage of the chemical composition of the iron-nickel alloy welding wire to meet -0.005%≤S1≤0.005%, where S1=C / 20+Al / 3×2+Mg×2+Ca+V / 3+Ti / 6+Nb / 6-O×3-N×3. This ensures that the welding wire composition contains a certain amount of C, Al, Mg, Ca, V, Ti, and Nb elements, thereby forming a good degassing reaction in the molten pool during the welding cladding process. This avoids gas accumulation in the cladding metal during welding, thereby improving the low-temperature impact toughness of the weld cladding metal after welding.

[0037] A second aspect of the present invention provides a method for manufacturing an iron-nickel alloy welding wire for welding liquefied gas equipment as described in the first aspect of the present invention, comprising the following steps:

[0038] Smelting;

[0039] Forging involves heating the smelted ingot to 1000~1200℃ and holding it for 60~180 minutes, then forging it into a forging billet.

[0040] Hot rolling involves heating the forged billet before rolling, controlling the heating temperature at 1000~1200℃, holding the temperature for 60~180min, and then hot rolling it into a coil.

[0041] Wire drawing involves drawing coiled wire into iron-nickel alloy welding wire.

[0042] This invention strictly controls the heating temperature and holding time before forging and hot rolling in the manufacturing process of iron-nickel alloy welding wire. The heating temperature before forging and hot rolling is controlled at 1000~1200℃. Excessively high or low heating temperatures will lead to deterioration of deformation plasticity, resulting in processing cracks. Simultaneously, the heating and holding time is controlled at 60~180 minutes. Too short a heating time will result in uneven heating; too long a heating time will lead to material over-oxidation and reduced surface plasticity.

[0043] Preferably, the smelting adopts an electric furnace, an electric furnace + electroslag remelting, a vacuum induction + electroslag remelting, a vacuum induction + vacuum self-consumption smelting, or a vacuum induction + electroslag remelting + vacuum self-consumption smelting method.

[0044] The present invention provides an iron-nickel alloy welding wire for welding liquefied gas equipment and its manufacturing method, which has the following beneficial effects:

[0045] 1) Traditional welding wires improve the toughness of the welded cladding metal by controlling the content of impurity elements such as P, S, O, and N, but cannot meet the requirement of a V-shaped impact toughness of ≥150 Jcm at -196℃ for the welded cladding metal. -2 The requirement is that welding wire has its own unique characteristics. Compared with traditional materials, welding wire does not use its own properties directly, but needs to be used after cladding. Therefore, in the material composition design, this invention must not only consider the performance of the welding wire itself, but also the performance of the cladding metal after the welding wire is clad.

[0046] 2) This invention, through research, discovered that repeated heating of the welding wire during the cladding process generates significant thermal stress within the cladding metal, leading to microscopic thermal cracks at interfaces (such as dendrite interfaces and inclusion interfaces), resulting in deterioration of the cladding metal's low-temperature impact performance. Therefore, this invention addresses this issue by controlling the content of S, P, O, and N within a low range, and by increasing the C content in the welding wire to increase material supercooling, accelerating solidification during welding, and preventing the formation of a liquid film. This avoids microcracks at dendrite interfaces under welding thermal stress. Simultaneously, increasing the C content, as the primary deoxidizing element, prevents the formation of deoxidation products during deoxidation. Appropriate addition of Mg and reduction of Al content ensure effective deoxidation while forming fine Mg deoxidation products, reducing coarse AlO deoxidation products, minimizing stress concentration during welding, and effectively preventing welding thermal cracks at inclusion interfaces.

[0047] 3) Based on the composition design, the iron-nickel alloy welding wire of the present invention also ensures the plasticity of the welding wire during the preparation process and prevents cracking during the thermal process by controlling the heating temperature and heating time during forging and rolling.

[0048] 4) The coefficient of thermal expansion of the iron-nickel alloy welding wire prepared by this invention is (1.0~2.0)×10⁻¹⁰ between -180℃ and 0℃. -6 m / m / ℃, the V-shaped impact test result of the weld cladding metal after welding using this iron-nickel alloy welding wire at -196℃ is ≥150Jcm. -2 This invention ensures the low expansion performance of the iron-nickel alloy welding wire and improves the low-temperature impact performance of the weld cladding metal after welding, meeting the high comprehensive performance requirements of cryogenic liquefied gas transport components, and is particularly suitable for the manufacture of cryogenic liquefied gas transport components. Detailed Implementation

[0049] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with embodiments.

[0050] The main components of the iron-nickel alloy welding wires in Examples 1-6 are shown in Table 1, with the balance being Fe and unavoidable impurities.

[0051] Based on the process parameters shown in Table 2, the manufacturing method of the iron-nickel alloy welding wire in Examples 1-6 includes the following steps:

[0052] Smelting; smelting according to the above-mentioned composition of iron-nickel alloy welding wire;

[0053] Forging involves heating the smelted ingot to 1000~1200℃ and holding it for 60~180 minutes, then forging it into a forging billet.

[0054] Hot rolling involves heating the forged billet before rolling, controlling the heating temperature at 1000~1200℃, holding the temperature for 60~180min, and then hot rolling it into a coil.

[0055] Wire drawing involves drawing coiled wire into iron-nickel alloy welding wire. The product performance is shown in Table 3.

[0056] The main components of the iron-nickel alloy welding wires in Comparative Examples 1-4 are shown in Table 1, with the balance being Fe and unavoidable impurities;

[0057] Comparative Examples 1-4 adopted the manufacturing method in the examples, and the process parameters are shown in Table 2. The performance of the final iron-nickel alloy welding wire is shown in Table 3.

[0058] Table 1 Chemical composition (wt%) of iron-nickel alloy welding wire

[0059]

[0060] Table 2 Manufacturing process parameters

[0061]

[0062] Table 3 Performance of Iron-Nickel Alloy Welding Wire

[0063]

[0064] As shown in Tables 1, 2, and 3, the iron-nickel alloy welding wires obtained using the manufacturing method of this invention in Examples 1-6 have a coefficient of thermal expansion of 1.2 × 10⁻⁶ between -180°C and 0°C. -6 ~1.7×10 -6 m / m / ℃, the V-notch impact toughness of the cladding metal after welding with iron-nickel alloy welding wire at -196℃ is 170~180 J / cm. 2 Compared with the iron-nickel alloy welding wires of Comparative Examples 1-4, the present invention, through composition design and improved manufacturing method, can ensure the thermal expansion performance of the iron-nickel alloy welding wire and greatly improve the low-temperature impact performance of the cladding metal after welding at -196℃.

[0065] In Comparative Example 1, the iron-nickel alloy had excessively high Al and B content, low Mg content, and excessively high Si content. Furthermore, the heating temperature before hot rolling was controlled too low during manufacturing. This resulted in poor V-shaped impact toughness of the weld metal after welding at -196℃, reaching only 71 J / cm². 2 The low-temperature impact performance of the cladding metal after welding with the iron-nickel alloy welding wire in the example is far lower than that of the example, and it does not meet the requirements of the cryogenic liquefied gas transport component.

[0066] In Comparative Example 2, the iron-nickel alloy had a low carbon content, excessively high Al and Mg content, and an excessively high Si value. Furthermore, the forging heating temperature was controlled too high during manufacturing, resulting in poor V-shaped impact toughness of the weld metal after welding at -196℃, reaching only 69 J / cm². 2 The low-temperature impact performance of the cladding metal after welding with the iron-nickel alloy welding wire in the example is far lower than that of the example, and it does not meet the requirements of the cryogenic liquefied gas transport component.

[0067] In Comparative Example 3, the iron-nickel alloy had low C and Mg content, excessive P, S, and Al content, and an excessively low S1 value. Furthermore, the heating temperature before hot rolling was controlled too low during manufacturing. This resulted in poor V-shaped impact toughness of the weld metal after welding at -196℃, reaching only 76 J / cm². 2 The low-temperature impact performance of the cladding metal after welding with the iron-nickel alloy welding wire in the example is far lower than that of the example, and it does not meet the requirements of the cryogenic liquefied gas transport component.

[0068] In Comparative Example 4, the iron-nickel alloy had an excessively low carbon content, no added Mg, and an excessively low Si value. Furthermore, the forging heating temperature was controlled too low during manufacturing. This resulted in poor V-shaped impact toughness of the weld metal after welding at -196℃, reaching only 59 J / cm². 2 The low-temperature impact performance of the cladding metal after welding with the iron-nickel alloy welding wire in the example is far lower than that of the example, and it does not meet the requirements of the cryogenic liquefied gas transport component.

[0069] In summary, the iron-nickel alloy welding wire manufactured by the method of the present invention has a coefficient of thermal expansion of (1.0~2.0)×10⁻¹⁰ between -180℃ and 0℃. -6 m / m / ℃, the V-shaped impact test result of the weld cladding metal after welding using this iron-nickel alloy welding wire at -196℃ is ≥150Jcm. -2 This invention ensures the low expansion performance of the iron-nickel alloy welding wire and improves the low-temperature impact performance of the weld cladding metal after welding, meeting the high comprehensive performance requirements of cryogenic liquefied gas transport components, and is particularly suitable for the manufacture of cryogenic liquefied gas transport components.

[0070] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A nickel-iron alloy welding wire for welding liquefied gas equipment, characterized in that: Its chemical composition by weight percentage is as follows: 34.5%≤Ni≤37.5%, 0.040%≤C≤0.080%, 0.01%≤Si≤0.30%, 0.1%≤Mn≤0.6%, P≤0.0030%, S≤0.0015%, O≤0.0030%, N≤0.0020%, 0.0010%≤Mg≤0.0040%, 0.0005%≤Al≤0.0040%, 0.0001%≤V≤0.0020%, 0.0001%≤Ti≤0.0020%, 0.0001%≤Nb≤0.0020%, 0.0001%≤Ca≤0.0020%, B≤0.0010%, with the balance being Fe and unavoidable impurities; The weight percentage of the chemical composition of the iron-nickel alloy welding wire also satisfies the following formula: -0.005%≤S1≤0.005% S1=C / 20+Al / 3×2+Mg×2+Ca+V / 3+Ti / 6+Nb / 6-O×3-N×3.

2. The iron-nickel alloy welding wire for welding liquefied gas equipment according to claim 1, characterized in that: 0.003%≤S1≤0.004%。 3. The iron-nickel alloy welding wire for welding liquefied gas equipment according to claim 1, characterized in that: The chemical composition of the iron-nickel alloy welding wire also satisfies the following conditions: 0.2%≤Mn≤0.5%, 0.001%≤Al≤0.004%, 0.0002%≤V≤0.0020%, 0.0002%≤Ti≤0.0020%, and 0.0002%≤Nb≤0.0020%.

4. The iron-nickel alloy welding wire for welding liquefied gas equipment according to claim 1, characterized in that: The coefficient of thermal expansion of the iron-nickel alloy welding wire between -180℃ and 0℃ is (1.0~2.0)×10⁻¹⁰. -6 m / m / ℃.

5. The iron-nickel alloy welding wire for welding liquefied gas equipment according to claim 4, characterized in that: The coefficient of thermal expansion of the iron-nickel alloy welding wire between -180℃ and 0℃ is (1.2~1.8)×10⁻¹⁰. -6 m / m / ℃.

6. The iron-nickel alloy welding wire for welding liquefied gas equipment according to claim 1, characterized in that: The weld cladding metal after welding with the iron-nickel alloy welding wire exhibits a V-shaped impact toughness ≥150 J / cm² at -196℃. -2 .

7. The iron-nickel alloy welding wire for welding liquefied gas equipment according to claim 6, characterized in that: The weld cladding metal after welding with the iron-nickel alloy welding wire exhibits a V-shaped impact toughness of 155~178 J / cm² at -196℃. -2 .

8. A method for manufacturing an iron-nickel alloy welding wire for welding liquefied gas equipment as described in any one of claims 1 to 7, characterized in that: Includes the following steps: Smelting; Forging involves heating the smelted ingot to 1000~1200℃ and holding it for 60~180 minutes, then forging it into a forging billet. Hot rolling involves heating the forged billet before rolling, controlling the heating temperature at 1000~1200℃, holding the temperature for 60~180min, and then hot rolling it into a coil. Wire drawing involves drawing coiled wire into iron-nickel alloy welding wire.

9. The method for manufacturing the iron-nickel alloy welding wire for welding liquefied gas equipment according to claim 8, characterized in that: The smelting process employs electric furnace, electric furnace + electroslag remelting, vacuum induction + electroslag remelting, vacuum induction + vacuum self-consumption smelting, or vacuum induction + electroslag remelting + vacuum self-consumption smelting methods.

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