Welding process of 500mpa grade weathering steel and application in low temperature service environment

Abstract

The present application relates to a kind of 500MPa grade weathering steel welding process and application in low temperature service environment.The welding method of prior art 500MPa grade weathering steel has the defect that cannot meet the requirement of low temperature service, the present application provides a kind of based on flux-cored wire and cold metal transition welding process, the composition of flux-cored wire is optimized, the nucleation rate of weld metal acicular ferrite is increased, the low temperature impact toughness of joint is guaranteed;On the other hand, cold metal transition welding process is used, short-circuit current is controlled, welding heat input is reduced, and the burning loss of alloy element is reduced.Weathering steel welded joint prepared based on the process of the present application has good low temperature impact toughness, and can meet the use demand of low temperature service environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-strength weathering steel welding process, and particularly relates to a welding process for a 500MPa-grade weathering steel and application of the welding process in a low-temperature service environment. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission by the patent applicant or the like that the information forms part of the prior art that is already known in this field.

[0003] The 500MPa-grade weathering steel, as one of low-alloy high-strength steels, has high strength, good plasticity and toughness, and good atmospheric corrosion resistance, and is obviously superior to ordinary structural steel in performance, and has been widely used in structures exposed to air, such as trains, bridges, high-voltage transmission towers and other structures susceptible to atmospheric corrosion.

[0004] The 500MPa-grade weathering steel contains many alloying elements such as Mn, Cr, Ni and Cu, and the strength is improved through solid solution strengthening, fine-grain strengthening and precipitation strengthening mechanisms. Controlling the content of alloying elements to form acicular ferrite structure in the weld is the key to ensuring the strength and toughness of the weathering steel welded joint. The commonly used welding methods include laser-arc composite solid wire welding and CO2 gas shielded flux-cored wire welding process. The laser-arc composite solid wire welding has small welding heat input, and the obtained weld structure is mainly fine acicular ferrite, which can ensure the sufficient strength and toughness of the joint, but the joint assembly requirement is strict, and the use of laser increases the equipment cost. The CO2 gas shielded flux-cored wire welding process can obtain high welding efficiency, but due to the large welding heat input, coarse proeutectoid ferrite structure often appears in the weld, which reduces the low-temperature impact toughness of the joint, and is not suitable for welding structures serving at low temperature.

[0005] In order to meet the application requirements of the 500MPa-grade weathering steel in low-temperature occasions, a welding process with small heat input and high welding efficiency needs to be developed, the alloy element burnout amount is reduced through the filling material and process control, and a 500MPa-grade weathering steel welding structure with low cost and good low-temperature impact performance is obtained. SUMMARY

[0006] The present application aims to provide a welding process for a 500MPa-grade weathering steel, and solve the problem that the existing weathering steel welding structure is not suitable for low-temperature application environment. In order to achieve the above technical purpose, the present application provides a process combining flux-cored wire and cold metal transfer welding, which not only solves the low-temperature service performance of the weathering steel welding structure, but also significantly improves the low-temperature impact performance of the welded joint, and has the characteristics of low cost, simple equipment and easy popularization and application.

[0007] The first object of the present application is to provide a flux-cored wire cold metal transfer welding process for 500MPa grade weathering steel, which on one hand adopts flux-cored wire, increases the nucleation rate of acicular ferrite in weld metal by optimizing the chemical composition of the flux-cored wire, and ensures the low-temperature impact toughness of the joint; on the other hand adopts cold metal transfer welding process, reduces the welding heat input by controlling the short-circuit current, reduces the burning loss of alloying elements, and prevents the formation of coarse proeutectoid ferrite in weld metal. The two effects simultaneously improve the low-temperature impact toughness of the weathering steel welded joint, and ensure the safety of the joint in low-temperature environment.

[0008] The components of the flux-cored wire optimized by the present application are as follows: C 0.05-0.1%, Mn 0.6-1.5%, Si 0.4-0.8%, Ni 0.6-0.9%, Cr 0.5-0.8%, Cu 0.5-0.9%, Ti 0.6-1.0%, S<0.005%, P<0.008%, and the balance is Fe. The present application adds a small amount of Ti element to the flux-cored wire, and the Ti element forms TiC particles with the base material during the solidification process of the weld metal, which promotes the nucleation of acicular ferrite and promotes the formation of acicular ferrite in the grain, thereby improving the strength and toughness of the 500MPa grade weathering steel welded joint.

[0009] In addition, the present application adopts cold metal transfer welding process. This welding process digitizes the coordination between wire feeding and droplet transfer, realizes the intermittent wire feeding process, and when the droplet transfer is performed, the power supply controls the current to be very low. By monitoring the wire feeding process, the "cold" and "hot" alternating welding is realized, and the welding heat input is reduced.

[0010] The strength and low-temperature performance of the weathering steel joint prepared by the above welding method are investigated, and the results show that the joint strength can reach more than 680MPa, which is higher than the strength of the base material, and the impact energy of the weld at-60℃ can reach more than 140J, reaching high toughness level.

[0011] Based on the high strength and low-temperature performance of the above welding joint, the welding method provided by the present application and the weathering steel welded part using the method are very suitable for steel structures in low-temperature service environment, such as vehicle chassis, power towers, etc., which provides a low-cost welding method for the above complex working conditions.

[0012] The beneficial effects of one or more of the above technical solutions are:

[0013] 1. Compared with the existing welding process, the process provided by the present application has the characteristics of small welding heat input, convenient process control, and low joint assembly requirement.

[0014] 2、The application adds alloy element Ti to the flux-cored wire, and TiC particles can be formed with the base material during the solidification of the weld metal, which can act as the nucleation of acicular ferrite and promote the formation of more acicular ferrite structure, thereby improving the strength and toughness of the 500MPa-grade weathering steel welded joint. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The embodiments of the application, and their

[0016] Figure 1 The microstructure feature map (200x magnification) of the base welding weld metal obtained by the cold metal welding of the 500MPa-grade weathering steel flux-cored wire obtained in Example 1; wherein: 1 is proeutectoid ferrite structure, and 2 is acicular ferrite structure.

[0017] Figure 2 The microstructure feature map (200x magnification) of the base welding weld metal obtained by the cold metal welding of the 500MPa-grade weathering steel flux-cored wire obtained in Example 1; wherein: 1 is proeutectoid ferrite structure, and 2 is acicular ferrite structure.

[0018] Figure 3 The microstructure feature map (200x magnification) of the base welding weld metal obtained by the cold metal welding of the 500MPa-grade weathering steel flux-cored wire obtained in Example 1; wherein: 1 is proeutectoid ferrite structure, and 2 is acicular ferrite structure. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed description is merely exemplary and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0021] As introduced in the background, the welding of the 500MPa-grade weathering steel in the prior art still has the defects of high welding cost and inability to meet the low-temperature service requirements. In order to solve the above technical problems, the present application proposes a 500MPa-grade weathering steel welding method based on flux-cored wire and cold metal transition welding process.

[0022] In a first aspect, a welding method for a 500MPa-grade weather-resistant steel is provided. The method uses a flux-cored wire to perform multi-layer and multi-pass welding on the butt joint of a weather-resistant steel welding piece under the protection of an argon-rich gas. The welding is a cold metal transfer welding process.

[0023] The flux-cored wire comprises the following components: C 0.05-0.1%, Mn 0.6-1.5%, Si 0.4-0.8%, Ni 0.6-0.9%, Cr 0.5-0.8%, Cu 0.5-0.9%, Ti 0.6-1.0%, S <0.005%, P <0.008%, and the balance being Fe.

[0024] The welding method comprises the following steps:

[0025] (1) Surface cleaning of the welding piece: remove the oxidation scale, rust, and impurities around the surface of the weather-resistant steel to be welded;

[0026] (2) Groove processing: process the end face of the weather-resistant steel to be welded into a V-shaped groove with a groove angle of 60°, a gap of 0.5-2mm, and a root face of 1-2mm;

[0027] (3) Welding: perform three-layer welding on the assembled butt joint of the weather-resistant steel welding piece using the flux-cored wire, in the order of a backing pass, a fill pass, and a cover pass. The welding current for the backing pass is 240-250A, the welding voltage is 25-26V, and the welding speed is 32-35cm / min. The welding current for the fill pass is 250-260A, the welding voltage is 26-27V, and the welding speed is 35-40cm / min. The welding current for the cover pass is 240-250A, the welding voltage is 25-26V, and the welding speed is 32-35cm / min. The frequency of the wire feeding and retraction motion is 70-90Hz.

[0028] In step (1) above:

[0029] The surface cleaning of the welding piece can be performed using a steel wire brush or sandpaper. In one specific embodiment, the surface of the weather-resistant steel to be welded and the surrounding area are first brushed with a steel wire brush until the metal luster is exposed, and then polished flat with a metallographic coarse sandpaper.

[0030] In step (2) above:

[0031] The gap and root face of the groove are adjusted according to the thickness of the weather-resistant steel, in the following manner:

[0032] For a weather-resistant steel plate with a thickness of 10-15mm, the gap is 0.4-0.6mm, and the root face is 0.8-1.2mm.

[0033] For a weather-resistant steel plate with a thickness of 15mm or more to 25mm, the gap is 0.8-1.2mm, and the root face is 0.8-1.2mm.

[0034] The weathering steel plate has a thickness of 25mm to 35mm, a gap of 1.8mm to 2.2mm, and a root face of 1.8mm to 2.2mm.

[0035] In addition, the shape of the groove is a single V-shaped groove.

[0036] In the step (3) above:

[0037] The welding process is protected by an argon-rich gas atmosphere, which is a mixture of argon (Ar) and carbon dioxide (CO2) with a mixing ratio of 85-95:5-15. In specific examples, it is 90% Ar+10% CO2, or 95% Ar+5% CO2, or 85% Ar+15% CO2, and the gas flow rate is 15-18mL / min.

[0038] In a second aspect, the weathering steel welded part prepared by the welding method of the first aspect is provided.

[0039] In a third aspect, the welding method of the first aspect and the weathering steel welded part of the third aspect are applied in the field of metals used in low-temperature service environments.

[0040] The low-temperature service environment mentioned above is, for example, a marine, aviation environment or an extremely cold region. The possible application methods are, for example, used to prepare train bodies, bridge structures, ships, containers, high-voltage transmission towers, oil pipelines, etc. In particular, the structures such as the underframe of a rail vehicle and a power tower are exposed to the air and are easily affected by atmospheric corrosion and low temperature, etc.

[0041] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with specific examples.

[0042] In the following examples, the type of weathering steel base material is Q500NH;

[0043] In the following examples, the preparation method of the flux-cored wire is as follows: the mixed powder (the weight parts of the components are: 3%-10% rutile, 2%-2.5% metal chromium powder, 3%-10% metal manganese, 1%-1.5% metal nickel powder, 0.8%-1.2% metal titanium powder, 3%-10% silicon iron, 2%-6% marble, 3%-8% arc stabilizing agent, 8%-10% anti-porosity agent, and the rest is iron powder) is uniformly placed on a carbon steel strip (size 0.4*10mm), then rolled into an O-shaped tube, and then continuously drawn to reduce the diameter, to prepare a metal powder type flux-cored wire with a diameter of 1.2mm.

[0044] Example 1

[0045] A cold metal transfer welding process of a weathering steel flux-cored wire with a thickness of 12 mm and a strength of 500 MPa, comprising the following steps:

[0046] First step: the surface to be welded of the weathering steel and its surrounding are first brushed with a steel wire brush to expose the metal luster, and then polished flat with a metallographic coarse sandpaper, so as to remove the oxide scale, rust and impurities;

[0047] Second step: the end face of the weathering steel to be welded is processed into a V-shaped groove with a groove angle of 60 ° , a gap of 0.5 mm and a root face of 1 mm;

[0048] Third step: the abovementioned assembled weathering steel welding piece is butt-jointed and welded by filling three layers of welds with the flux-cored wire; the chemical composition of the flux-cored wire (mass fraction) is: C 0.08%, Mn 1.5%, Si 0.6%, Ni 0.9%, Cr 0.6%, Cu 0.5%, Ti 0.6%, S 0.004%, P 0.007%, and the balance is Fe; the welding current of the backing weld is 240 A, the welding voltage is 25 V, and the welding speed is 32 cm / min; the welding current of the fill weld is 250 A, the welding voltage is 26 V, and the welding speed is 38 cm / min; the welding current of the cap weld is 240 A, the welding voltage is 25 V, and the welding speed is 35 cm / min; the frequency of the wire feeding and retraction movement is 70 Hz. The welding process is protected by 90% Ar+10% CO2 mixed gas, and the gas flow is 15 L / min.

[0049] For the cold metal transfer welding process of the weathering steel flux-cored wire with a thickness of 12 mm and a strength of 500 MPa, the welding heat input is 10-11 kJ / cm, so that the microstructure of the backing weld metal is mostly acicular ferrite, and the proeutectoid ferrite is less (see Figure 1 ); the microstructure of the fill weld metal is almost acicular ferrite (see Figure 2 ); the microstructure of the cap weld metal is all acicular ferrite (see Figure 3 ), the tensile strength of the joint is 682 MPa, and the impact energy of the weld at-60℃ is 155 J.

[0050] Example 2

[0051] A cold metal transfer welding process of a weathering steel flux-cored wire with a thickness of 20 mm and a strength of 500 MPa, comprising the following steps:

[0052] First step: the surface to be welded of the weathering steel and its surrounding are first brushed with a steel wire brush to expose the metal luster, and then polished flat with a metallographic coarse sandpaper, so as to remove the oxide scale, rust and impurities;

[0053] Second step: the end face of the weathering steel to be welded is processed into a V-shaped groove with a groove angle of 60°, a gap of 1 mm, and a root face of 1.5 mm;

[0054] Third step: the abovementioned assembled weathering steel welding piece is butt-jointed and welded by filling five layers of welding beads with flux-cored wire; the chemical composition (mass fraction) of the flux-cored wire is: C 0.1%, Mn 0.6%, Si 0.8%, Ni 0.7%, Cr 0.8%, Cu 0.7%, Ti 0.8%, S 0.004%, P 0.006%, and the balance is Fe; the welding current for the backing welding is 250 A, the welding voltage is 26 V, and the welding speed is 35 cm / min; the welding current for the filler welding is 260 A, the welding voltage is 27 V, and the welding speed is 40 cm / min; the welding current for the cap welding is 240 A, the welding voltage is 25 V, and the welding speed is 32 cm / min, and the frequency of the wire feeding and retraction movement is 80 Hz; the welding process is protected by 90% Ar + 10% CO2 mixed gas, and the gas flow is 18 L / min.

[0055] For the cold metal transfer welding process of the flux-cored wire for the weathering steel with a strength of 500 MPa and a thickness of 20 mm, the welding heat input is about 11 kJ / cm, and thus the tensile strength of the welded joint obtained is 690 MPa, and the impact energy of the weld at -60°C is 148 J.

[0056] Example 3

[0057] A cold metal transfer welding process for a weathering steel with a strength of 500 MPa and a thickness of 30 mm includes the following steps:

[0058] First step: the surface to be welded of the weathering steel and the surrounding area thereof are first brushed to expose the metal luster by using a steel wire brush, and then polished flat by using a metallographic coarse sandpaper, so as to clean the oxide skin, rust and impurities;

[0059] Second step: the end face of the weathering steel to be welded is processed into a V-shaped groove with a groove angle of 60°, a gap of 2 mm, and a root face of 2 mm;

[0060] Third step: butt joint of the assembled weathering steel welding piece is filled with three-layer welding by using the flux-cored wire; the chemical composition (mass fraction) of the flux-cored wire is: C 0.05%, Mn 0.8%, Si 0.4%, Ni 0.6%, Cr 0.5%, Cu 0.9%, Ti 1.0%, S 0.005%, P 0.008%, and the balance is Fe; the welding current of the backing welding is 250 A, the welding voltage is 26 V, and the welding speed is 35 cm / min; the welding current of the filling welding is 260 A, the welding voltage is 27 V, and the welding speed is 35 cm / min; the welding current of the cover welding is 250 A, the welding voltage is 26 V, and the welding speed is 32 cm / min; the frequency of the welding wire feeding and retraction movement is 90 Hz; the welding process is protected by using 90% Ar+10% CO2 mixed gas, and the gas flow is 18 L / min.

[0061] For the flux-cored wire cold metal transfer welding process of the weathering steel with a thickness of 30 mm and a strength of 500 MPa, the welding heat input is 10-11 kJ / cm, so that the tensile strength of the welding joint obtained is 702 MPa, and the impact energy of the weld at-60 ℃ is 142 J.

[0062] Comparative example 1

[0063] A flux-cored wire mixed gas protection welding process for a weathering steel with a thickness of 12 mm and a strength of 500 MPa, comprising the following steps:

[0064] First step: the surface to be welded of the weathering steel and the surrounding thereof are first brushed to expose the metal luster by using a steel wire brush, and then polished flat by using a metallographic coarse sandpaper, so as to clean the oxide skin, rust and impurities;

[0065] Second step: the end face of the weathering steel to be welded is processed into a V-shaped groove with a groove angle of 60°, a gap of 0.5 mm and a blunt edge of 1 mm;

[0066] Third step: butt joint of the assembled weathering steel welding piece is filled with three-layer welding by using the flux-cored wire; the chemical composition (mass fraction) of the flux-cored wire is: C 0.05%, Mn 0.8%, Si 0.4%, Ni 0.6%, Cr 0.5%, Cu 0.9%, Ti 1.0%, S 0.005%, P 0.008%, and the balance is Fe; the welding current of the backing welding is 250 A, the welding voltage is 26 V, and the welding speed is 35 cm / min; the welding current of the filling welding is 260 A, the welding voltage is 27 V, and the welding speed is 35 cm / min; the welding current of the cover welding is 250 A, the welding voltage is 26 V, and the welding speed is 32 cm / min; the frequency of the welding wire feeding and retraction movement is 90 Hz; the welding process is protected by using 90% Ar+10% CO2 mixed gas, and the gas flow is 18 L / min.

[0067] For the thickness of 12mm 500MPa grade weathering steel strength of flux-cored wire mixed gas welding process, the wire is always sent in, no back process, welding heat input is 15-16kJ / cm, the joint tensile strength of 660MPa, -60 ℃ weld impact energy is 139J.

[0068] Comparative example 2

[0069] A thickness of 20mm 500MPa grade weathering steel strength of flux-cored wire mixed gas welding process, including the following steps:

[0070] First step: the weathering steel surface to be welded and its surroundings are first brushed to expose the metal luster, and then polished flat with metallographic coarse sandpaper, the purpose is to remove the oxide skin, rust and impurities clean;

[0071] Second step: the weathering steel to be welded end face is processed into V-shaped groove, the groove angle is 60°, the gap is 1mm, the blunt edge is 1.5mm;

[0072] Third step: the above assembled weathering steel welding piece is butt jointed for five-layer welding of flux-cored wire; the chemical composition of the flux-cored wire (mass fraction) is: C 0.1%, Mn 0.6%, Si 0.8%, Ni 0.3%, Cr 0.8%, Cu 0.7%, Ti 0.08%, S 0.004%, P 0.006%, the balance is Fe; the welding current of the backing welding is 260A, the welding voltage is 27V, and the welding speed is 35cm / min; the welding current of the filler welding is 280A, the welding voltage is 27V, and the welding speed is 40cm / min; the welding current of the cover welding is 250A, the welding voltage is 26V, and the welding speed is 33cm / min; the welding process is protected by 90% Ar+10% CO2 mixed gas, and the gas flow is 18L / min.

[0073] For the thickness of 20mm 500MPa grade weathering steel strength of mixed gas welding process, the wire is always sent in, no back process, welding heat input is about 17kJ / cm, so the tensile strength of the welded joint is 650MPa, and the impact energy of the weld at -60 ℃ is 136J.

[0074] Comparative example 3

[0075] A thickness of 30mm 500MPa grade weathering steel strength of flux-cored wire mixed gas welding process, including the following steps:

[0076] First step: the weathering steel surface to be welded and its surroundings are first brushed to expose the metal luster, and then polished flat with metallographic coarse sandpaper, the purpose is to remove the oxide skin, rust and impurities clean;

[0077] Second step: the end face of the weathering steel to be welded is processed into a V-shaped groove with a groove angle of 60°, a gap of 2mm and a root face of 2mm;

[0078] Third step: the butt joint of the assembled weathering steel welding piece is filled with three layers of welding bead by using the flux-cored wire; the chemical composition (mass fraction) of the flux-cored wire is: C 0.05%, Mn 0.8%, Si 0.4%, Ni 0.3%, Cr 0.5%, Cu 0.9%, Ti 0.006%, S 0.005%, P 0.008%, and the balance is Fe; the welding current of the backing welding is 260A, the welding voltage is 27V, and the welding speed is 35cm / min; the welding current of the filling welding is 270A, the welding voltage is 27V, and the welding speed is 35cm / min; the welding current of the cap welding is 260A, the welding voltage is 27V, and the welding speed is 33cm / min; the welding process is protected by using 90% Ar+10% CO2 mixed gas, and the gas flow is 18L / min.

[0079] For the mixed gas welding process of the flux-cored wire for the weathering steel with a thickness of 30mm and a strength of 500MPa, the welding wire is continuously fed without a back-pulling process, the welding heat input is 15-17kJ / cm, and therefore the tensile strength of the welding joint obtained is 660MPa, and the impact energy of the weld at-60℃ is 130J.

[0080] As can be seen from the results in the above examples and comparative examples, by optimizing the components of the flux-cored wire and reducing the heat input at the weld at the same time, the present application effectively reduces the growth of ferrite in the welding joint, and effectively improves the tensile strength and low-temperature resistance of the weld.

[0081] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A welding method for weathering steel with a strength of 500 MPa, characterized in that, Multi-layer, multi-pass welding of weathering steel weldments is performed at the joints using flux-cored welding wire under argon-rich gas protection. The welding process is a cold metal transition welding process. The welding heat input is 10~11 kJ / cm. The composition of the flux-cored welding wire is as follows: C 0.05~0.1%, Mn 0.6~1.5%, Si 0.4~0.8%, Ni 0.6~0.9%, Cr 0.5~0.8%, Cu 0.5~0.9%, Ti 0.6~1.0%, S<0.005%, P<0.008%, with the balance being Fe; The thickness of the weathering steel is 10~35mm; the type of the weathering steel base material is Q500NH; The specific steps of the welding method are as follows: (1) Surface cleaning of the weldment: Clean the oxide scale, rust and impurities from the surface of the weathering steel to be welded and its surrounding area; (2) Beveling: The end face of the weathering steel to be welded is machined into a V-shaped bevel with a bevel angle of 60º, a gap of 0.5~2mm, and a blunt edge of 1~2mm; (3) Welding: The assembled weathering steel weldment is welded with flux-cored wire in three layers, namely root pass, fill pass and cover pass; the welding current for root pass is 240~250A, welding voltage is 25~26V and welding speed is 32~35cm / min; the welding current for fill pass is 250~260A, welding voltage is 26~27V and welding speed is 35~40cm / min; the welding current for cover pass is 240~250A, welding voltage is 25~26V and welding speed is 32~35cm / min; the frequency of wire feeding and retraction is 70~90Hz.

2. The welding method as described in claim 1, characterized in that, In step (1): the surface cleaning method of the weldment is as follows: first use a wire brush to brush the surface of the weathering steel to be welded and its surroundings until the metal luster is exposed, and then use metallographic coarse sandpaper to polish it smooth.

3. The welding method as described in claim 1, characterized in that, In step (3), the welding process is protected by an argon-rich gas atmosphere, which is a mixture of argon and carbon dioxide with a mixing ratio of 85~95:5~15 and a gas flow rate of 15-18 mL / min.

4. The welding method as described in claim 3, characterized in that, The mixed gas is 95%Ar + 5%CO2 or 85%Ar + 15%CO2.

5. The welding method as described in claim 3, characterized in that, The mixed gas is 90% Ar + 10% CO2.

6. Weathering steel weldment prepared by the welding method according to any one of claims 1-5.

7. The application of the welding method according to any one of claims 1-5 and the weathering steel weldment according to claim 6 in the field of metals for low-temperature service environments.

8. The application as described in claim 7, characterized in that, The applications include manufacturing train bodies, bridge structures, ships, containers, high-voltage transmission towers, or oil pipelines.

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