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

Abstract

The invention discloses an iron-nickel alloy welding wire for welding liquefied gas equipment and a manufacturing method of the iron-nickel alloy welding wire. The iron-nickel alloy welding wire comprises, by weight, 34.5% < = Ni < = 37.5%, 0.020% < = C < = 0.050%, 0.01% < = Si < = 0.30%, 0.1% < = Mn < = 0.6%, 0.0030% < = P, 0.0015% < = S, 0.0030% < = O, 0.0020% < = N, trace < = Mg < = 0.0020%, trace < = Al < = 0.0060%, 0.0020% < = V, 0.0020% < = Ti, 0.0020% < = Nb, trace < = Ca < = 0.0020%, 0.0010% < = B and the balance Fe and inevitable impurities. And the elements also need to simultaneously meet the following conditions: 0.0030% < = S1 < = 0.0060%, and-0.005% < = S2 < = 0. The welding wire has low expansibility, and an obtained welding seam has good low-temperature impact toughness. The thermal expansion coefficient of the alloy welding wire between-180 DEG C and 0 DEG C is (1.0-2.0) * 10 <-6 > m / m / DEG C, the V-shaped impact test result of welding cladding metal of the alloy welding wire at the temperature of-196 DEG C is larger than or equal to 150 Jcm <-2 >, and the alloy welding wire is particularly suitable for manufacturing low-temperature liquefied gas transportation assemblies.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of low-expansion alloy welding wire processing, and particularly relates to an iron-nickel alloy welding wire for welding liquefied gas equipment and a manufacturing method thereof. BACKGROUND

[0002] The global energy transformation is in full swing, and the demand for low-temperature gas transportation equipment is rising with the water level. Due to the low density of gas, in order to reduce transportation costs, the current mainstream transportation method is to cool the gas to below the boiling point to change it into a liquid, thereby improving transportation efficiency.

[0003] The main liquefied gases transported at present are liquefied ammonia, liquefied carbon dioxide, liquefied ethane, liquefied hydrogen, liquefied methane, etc. In order to ensure the safety of the tanked and transported liquefied gas, the transportation assembly usually needs to have suitable low-temperature expansion performance and excellent low-temperature impact toughness. In order to meet the requirements of the structural performance after welding, special design is needed for the traditional welding wire.

[0004] Chinese patent CN103084753A discloses a nickel-iron precision alloy welding wire, the chemical composition of which is as follows: 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%, and the rest is Fe and unavoidable impurities; wherein, C / (Nb+Ti) <0.2; the performance index of the deposited metal is: tensile strength (Rm) ≥480 MPa, 20℃ impact toughness AKV2 ≥50 J / cm 2 , 20-100℃ linear expansion coefficient ≤1.2×10 -6 / ℃. Ti and Nb are used to strengthen the weld metal, so as to improve the strength and toughness of the weld metal. However, the optimization of the impact performance of the weld at low temperature is not studied.

[0005] Chinese patent CN107866647A discloses an Fe-Ni invar alloy welding wire and a manufacturing method thereof, the chemical composition of which is as follows: 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%, and the rest is Fe and unavoidable impurities. By increasing the C content and appropriately adding Cr, V and other elements, the strength and toughness of the deposited metal are improved through carbide strengthening and solid solution strengthening, and a lower expansion performance is ensured. This patent mainly strengthens the grain boundary through the carbide of Cr and V, and only studies the room temperature performance. However, a large amount of coarse carbide exists, which will deteriorate the low-temperature impact performance of the material and become a crack source of cracking.

[0006] In summary, at present, in the low expansion alloy welding wire component design, by adding strong carbide forming elements, forming dispersed carbides on the matrix, while improving the strength by precipitation strengthening, at the same time, through grain refinement, the purpose of improving toughness is achieved. This technical means is limited to improve the strength and toughness of the welding wire itself, and has very limited effect on improving the low temperature toughness of the weld bead after welding. Because after the welding wire is welded and melted, it is cooled into a cast structure, which shows coarse dendrites. These dispersed carbides cannot effectively refine the grains, so as to improve the toughness. On the contrary, too much carbide precipitates at the grain boundary, which reduces the grain boundary bonding force and the low temperature impact toughness. SUMMARY

[0007] The purpose of the present application is to provide an iron-nickel alloy welding wire for liquefied gas equipment welding and a manufacturing method thereof, the welding wire has low expansion, and the obtained weld bead has good low temperature impact toughness; the thermal expansion coefficient of the alloy welding wire between-180℃ and 0℃ is (1.0-2.0)×10 -6 m / m / ℃, the V-shaped impact test result of the welding bead at-196℃ temperature is ≥150Jcm -2 , which is suitable for manufacturing low temperature gas transportation components.

[0008] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0009] The iron-nickel alloy welding wire for liquefied gas equipment welding has the following chemical components by weight percentage: 34.5%≤Ni≤37.5%, 0.020≤C≤0.050%, 0.01≤Si≤0.30%, 0.1≤Mn≤0.6%, P≤0.0030%, S≤0.0015%, O≤0.0030%, N≤0.0020%, trace≤Mg≤0.0020%, trace≤Al≤0.0060%, V≤0.0020%, Ti≤0.0020%, Nb≤0.0020%, trace≤Ca≤0.0020%, B≤0.0010%, the balance including Fe and unavoidable impurities; and the above elements also need to meet:

[0010] 0.0030%≤S1≤0.0060%, S1=Ca+Mg+Al+V / 5+Ti / 5+Nb / 5;

[0011] -0.005%≤S2≤0, S2=Al+Mg*2+Ca+V / 3+Ti / 6+Nb / 6-O*3-N*3.

[0012] Preferably, the balance is Fe and unavoidable impurities.

[0013] Preferably, the thermal expansion coefficient of the welding wire is (1.0-2.0) x 10 -6 m / m / ℃.

[0014] Preferably, the V-shaped impact test result of the weld bead of the welding wire after welding is ≥ 150 Jcm -2 at -196℃.

[0015] In the component design of the welding wire of the present application:

[0016] C: increasing the C content can improve the toughness of the weld bead and improve the flowability and wettability of the metal during welding. However, too high C content can also reduce the toughness of the metal, and at the same time cause the expansion coefficient to increase. Therefore, the C content is controlled to be 0.02-0.05% in the present application.

[0017] Ni: is an important alloying element to ensure the low expansion performance of the alloy, therefore, the Ni content is controlled to be 34.5-37.5% in the present application.

[0018] Mn: ensures that the weld metal has a certain strength, at the same time, Mn can generate MnS and MnO with desulfurization and deoxidation effect, reducing the hot cracking phenomenon caused by S. However, too high Mn content will cause the weld bead to become brittle and the toughness to become poor, therefore, the Mn content is controlled to be 0.1-0.6% in the present application.

[0019] Si: is a deoxidizing element in the welding wire. Since Mn alone deoxidizes, the generated MnO has a large density and is not easy to float out of the molten pool, therefore, a certain amount of Si element must be added to the welding wire to deoxidize together with Mn to generate SiO and MnO complex silicate (MnO·SiO), which can condense into large pieces of slag and float out in the molten pool, achieving good deoxidation effect. However, with the increase of Si content, low-melting-point inclusions are easily generated, leading to the generation of welding hot cracks, and at the same time, high Si can form silicate inclusions, reducing the impact toughness of the weld bead. Therefore, the Si content is controlled to be 0.01-0.30% in the present application.

[0020] Al: is an important deoxidizing element. Too low Al content will result in poor deoxidization effect in the alloy, deteriorating the thermal plasticity of the material and leading to the generation of welding hot cracks; at the same time, too low Al content will deteriorate the deoxidation reaction of the molten pool during welding, leading to too high O content in the weld bead after welding and deteriorating the impact toughness of the weld bead. Too high Al content will form Al oxide, which has adverse effects on the purity of the alloy, leading to the generation of hot cracks in the weld bead during welding and deteriorating the impact toughness of the weld bead. Therefore, the Al content is controlled to be trace-0.0060% in the present application.

[0021] Mg: is an important deoxidizing element. If the content of Mg is too low, the deoxidizing effect in the alloy is not good, the hot plasticity of the material is deteriorated, and the welding hot crack is caused. Meanwhile, the content of Mg being too low will deteriorate the deoxidizing reaction of the molten pool in the welding process of the welding wire, and the content of O in the cladding metal after welding is too high, which deteriorates the impact toughness of the weld. If the content of Mg is too high, the oxides of Mg are formed, which has a bad influence on the purity of the alloy, and the hot crack is caused in the cladding metal area in the welding process, which deteriorates the impact toughness of the weld. Therefore, the content of Mg is controlled to be trace amount ~ 0.0020% in the present application.

[0022] Ca: is an important deoxidizing and desulfurizing element. If the content of Ca is too low, the deoxidizing effect in the alloy is not good, the hot plasticity of the material is deteriorated, and the welding hot crack is caused. Meanwhile, the content of Ca being too low will deteriorate the deoxidizing reaction of the molten pool in the welding process of the welding wire, and the content of O in the cladding metal after welding is too high, which deteriorates the impact toughness of the weld. If the content of Ca is too high, the oxides of Ca are formed, which has a bad influence on the purity of the alloy, and the hot crack is caused in the cladding metal area in the welding process, which deteriorates the impact toughness of the weld. And the desulfurizing effect is not good if the content of Ca is too low. Therefore, the content of Ca is controlled to be trace amount ~ 0.0020% in the present application.

[0023] O: O in the alloy will form alumina inclusions, silicate inclusions and spherical oxide inclusions with Mg, Al, Ca, Ti and Si, which deteriorates the purity of the alloy, causes the hot crack in the cladding metal in the welding process and has a bad influence on the low temperature impact toughness of the weld. Therefore, the content of O is controlled to be ≤0.0030% in the present application.

[0024] N: N in the alloy will form nitrides with B, Al, Ti and V, which forms precipitated phases in the grain or the grain boundary, deteriorates the purity of the alloy, causes the hot crack in the cladding metal in the welding process and deteriorates the low temperature impact toughness of the weld. Therefore, the content of N is controlled to be ≤0.0020% in the present application.

[0025] V, Ti, Nb: V, Ti and Nb have strong binding force with N and O, and the content being too high forms the second phase in the alloy, which deteriorates the purity of the material, causes the hot crack in the cladding metal in the welding process and reduces the low temperature impact toughness of the alloy weld. Meanwhile, V, Ti and Nb also have a certain degassing effect. Therefore, the content of V is controlled to be ≤0.0020%, the content of Ti is controlled to be ≤0.0020% and the content of Nb is controlled to be ≤0.0020% in the present application.

[0026] B: B is a harmful impurity in the present application, which forms BN inclusions with N in the alloy and has a very bad influence on the low temperature impact performance of the weld. Therefore, the content of B is controlled to be ≤0.0010% in the present application.

[0027] P: in the present invention is a harmful impurity, can reduce the strength and toughness at the interface, lead to the generation of heat cracks in the weld overlay metal during welding, thereby reducing the low temperature impact toughness of the alloy weld. Therefore, the present invention controls the P content ≤0.0030%.

[0028] S: in the present invention is a harmful impurity, can reduce the strength and toughness at the interface, lead to the generation of heat cracks in the weld overlay metal during welding, thereby reducing the low temperature impact toughness of the alloy weld. Therefore, the present invention controls the S content 0.0010%.

[0029] Due to the particularity of the welding wire, in order to improve the impact toughness of the weld overlay metal after welding, the traditional way is to reduce the harmful S, P elements, and add a certain amount of Mn element, reduce the formation of low melting point substances at the grain boundary, thereby improving the grain boundary strength and impact performance. In addition, by reducing the O, N gas content in the welding wire, the impact toughness of the weld overlay metal after welding is improved, but the welding wire with lower O, N gas content is only a preliminary means to reduce the O, N content of the weld overlay metal after welding, and cannot avoid the increase of the gas content in the weld overlay metal after welding.

[0030] The present invention has found that only by reducing the content of S, P, O, N elements, even if the content of the welding wire itself is very low, the weld overlay metal cannot reach the desired high impact toughness of the present invention.

[0031] But the present invention has found that even if the content is controlled to be lower, the weld overlay metal after welding cannot reach the desired high low temperature impact toughness of the present invention. Avoiding the increase of the gas content after welding is the ultimate means to improve the impact toughness of the weld overlay metal after welding.

[0032] Therefore, the present invention improves the purity of the welding wire, reduces the content of S, P, V, Ti, Nb, O, N in the welding wire, reduces the precipitation of low strength and toughness phase at the grain boundary; at the same time, the welding wire composition contains a certain amount of Al, Mg, Ca, V, Ti, Nb elements, so that a good degassing reaction is formed in the weld pool during the welding process, avoiding the increase of the gas content in the weld overlay metal during the welding process, thereby improving the low temperature toughness of the weld overlay metal.

[0033] Ca, Mg, Al, V, Ti, Nb are degassing elements in the welding wire, Ca, Mg, Al are strong oxide forming elements, and all can form oxide inclusions, and have strong deoxidizing ability, and the effect has certain replaceability. V, Ti, Nb not only have strong binding force with gas, but also have strong binding force with C element, form carbide, weaken the deoxidizing effect, and at the same time, have adverse effect on low temperature impact. Therefore, in the application, Ca, Mg, Al elements are used as the main deoxidizing additive elements, the content of S1 is controlled to be 0.0030%≤S1≤0.0060%, S1=Ca+Mg+Al+V / 5+Ti / 5+Nb / 5, so as to avoid the formation of oxide inclusions and nitride inclusions, thereby improving the low temperature impact toughness of the weld. If the content of S1 is too low, the deoxidizing and denitrifying effect of the welding wire in the smelting and welding process is poor, the content of O and N is too high, and the hot plasticity of the cladding metal is deteriorated. If the content of S1 is too high, oxide inclusions and nitride inclusions are formed in the cladding metal, the strength and toughness at the interface are reduced, the cladding metal produces hot cracks in the welding process, and thus the low temperature impact toughness of the alloy weld is reduced.

[0034] While avoiding the formation of oxide inclusions and nitride inclusions, in order to ensure the degassing effect of the material, the application controls-0.005%≤S2≤0, S2=Al+Mg*2+Ca+V / 3+Ti / 6+Nb / 6-O*3-N*3, ensures that the welding wire contains a certain amount of Al, Mg, Ca, V, Ti and Nb elements, so that a good degassing reaction is formed in the molten pool during the welding cladding process, the cladding metal is not gasified during the welding process, and thus the low temperature impact toughness of the post-welding weld cladding metal is improved.

[0035] The manufacturing method of the iron-nickel alloy welding wire for liquefied gas equipment welding comprises the following steps:

[0036] 1) smelting

[0037] Smelting is carried out according to the above-mentioned composition;

[0038] 2) forging

[0039] The ingot is heated to a temperature of 1000-1200 DEG C, and the heating holding time is 60-180 minutes, and the forging is formed into a forged blank;

[0040] 3) hot rolling

[0041] The obtained forged blank is heated before rolling, the heating temperature is 1000-1200 DEG C, and the heating holding time is 60-180 minutes, and the hot rolling is formed into a disc round;

[0042] 4) wire drawing

[0043] The disc round is drawn into a welding wire.

[0044] Preferably, the smelting is carried out by using an electric furnace, an electric furnace + electroslag, vacuum induction + electroslag remelting, vacuum induction + vacuum consumable or vacuum induction + electroslag remelting + vacuum consumable.

[0045] The forging heating temperature is controlled at 1000-1200 DEG C, and excessively high or low heating temperature can cause deterioration of deformation plasticity and cracking in processing.

[0046] The forging heating temperature is controlled at 1000-1200 DEG C, and excessively high or low heating temperature can cause deterioration of deformation plasticity and cracking in processing.

[0047] Compared with the prior art, the present application has the following beneficial effects:

[0048] The conventional welding wire only controls the content of impurity elements such as P, S, O and N to improve the toughness of the cladding metal after welding, and cannot meet the requirement that the V-shaped impact toughness of the cladding metal is greater than or equal to 150 Jcm -2 at -196 DEG C.

[0049] The present application finds that, during the cladding process, the welding wire is repeatedly heated, which generates a large thermal stress in the cladding metal, thereby causing micro thermal cracks at the grain boundary of the cladding metal and deteriorating the low-temperature impact performance of the cladding metal.

[0050] In the component design, on the one hand, the content of S, P, O and N is controlled in a lower range; on the other hand, 0.0030%≤S1≤0.0060% and -0.005%≤S2≤0% are controlled to reduce the precipitation of oxides and nitrides at the grain boundary, improve the purity of the cladding metal after welding, increase the strength and toughness of the cladding metal at the grain boundary, reduce thermal cracks in the welding process, thereby improving the low-temperature impact toughness of the cladding metal.

[0051] On the basis of component design, the application controls heating temperature and heating time in the forging and rolling process, ensures plasticity of the welding wire in the preparation process, and prevents cracking in the thermal process.

[0052] The thermal expansion coefficient of the welding wire obtained by the application is (1.0-2.0) x 10 -6 m / m / ℃, and the V-shaped impact test result of the weld cladding metal at-196℃ is greater than or equal to 150 Jcm -2 after welding using the welding wire. The low expansion performance of the welding wire is ensured, the low-temperature impact performance of the weld cladding metal is improved, the high comprehensive performance requirement of the low-temperature liquefied gas transportation assembly is met, and the welding wire is particularly suitable for manufacturing of the low-temperature liquefied gas transportation assembly. DETAILED DESCRIPTION

[0053] The application will be further described below in combination with examples.

[0054] The component of the welding wire in the examples and the comparative examples is shown in Table 1, and the balance is iron and inevitable impurities.

[0055] The process parameters in the examples and the comparative examples are shown in Table 2. The properties obtained by the examples and the comparative examples are shown in Table 3.

[0056] In the comparative example 1, the Al content is too high, the S1 and S2 values are too high, the heating temperature before rolling is too low in the process control, and finally the V-shaped impact test result of the cladding metal at-196℃ is poor.

[0057] In the comparative example 2, the S1 and S2 values are too high, the heating temperature before rolling is too low in the process control, and finally the V-shaped impact test result of the cladding metal at-196℃ is poor.

[0058] In the comparative example 3, the Al content is too high, the S1 value is too high, the S2 value is too low, the heating temperature before forging is too low in the process control, and finally the V-shaped impact test result of the cladding metal at-196℃ is poor.

[0059] In the comparative example 4, the Mg element is not added, the S1 value is too high, the S2 value is too low, the heating temperature before forging is too low in the process control, and finally the V-shaped impact test result of the cladding metal at-196℃ is poor.

[0060]

[0061]

[0062]

[0063]

Claims

1. The iron-nickel alloy welding wire used for welding liquefied gas equipment has the following chemical composition by weight percentage: 34.5%≤Ni≤37.5%, 0.020%≤C≤0.050%, 0.01%≤Si≤0.30%, 0.1%≤Mn≤0.6%, P≤0.0030%, S≤0.0015%, O≤0.0030%, N≤0.0020%, trace ≤Mg≤0.0020%, trace ≤Al≤0.0060%, V≤0.0020%, Ti≤0.0020%, Nb≤0.0020%, trace ≤Ca≤0.0020%, B≤0.0010%, with the balance including Fe and unavoidable impurities; and the above elements must also simultaneously satisfy the following: 0.0030%≤S1≤0.0060%, S1=Ca+Mg+Al+V / 5+Ti / 5+Nb / 5; -0.005%≤S2≤0, S2=Al+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 as described in claim 1, characterized in that, The balance is Fe and unavoidable impurities.

3. The iron-nickel alloy welding wire for welding liquefied gas equipment as described in claim 1 or 2, characterized in that, The coefficient of thermal expansion of the welding wire between -180℃ and 0℃ is (1.0~2.0)×10⁻¹⁰. -6 m / m / ℃.

4. The iron-nickel alloy welding wire for welding liquefied gas equipment as described in claim 1 or 2, characterized in that, The weld cladding metal after welding with the welding wire has a V-shaped impact toughness ≥150 J / cm² at -196℃. -2 .

5. The method for manufacturing the iron-nickel alloy welding wire for welding liquefied gas equipment as described in any one of claims 1 to 4, characterized in that, Includes the following steps: 1) Smelting Smelting is carried out according to the composition described in claim 1 or 2; 2) Forging The ingot is heated to 1000-1200℃ and held for 60-180 minutes, then forged into a forging billet. 3) Hot rolling The obtained forging billet is heated before rolling at a temperature of 1000-1200℃ and held for 60-180 minutes, and then hot rolled into a coil. 4) Wire drawing The coiled wire is drawn into welding wire.

6. The manufacturing method as described in claim 5, characterized in that, The smelting process employs electric furnace, electric furnace + electroslag remelting, vacuum induction + electroslag remelting, vacuum induction + vacuum self-consumption, or vacuum induction + electroslag remelting + vacuum self-consumption.

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