An austenitic welding wire and a welding method suitable for high-strength steel structures

Abstract

The application provides an austenitic welding wire suitable for high-strength steel structure and a welding method, and belongs to the technical field of welding.The application adopts a multi-element protective gas, wherein the multi-element protective gas comprises Ar 43-50%, He 43-50%, N2 2-7% and O2 0-2% in terms of volume content, and Ar+He is greater than or equal to 93%; wherein Ar can effectively isolate air, He can shrink the electric arc, improve the electric arc temperature, N2 can improve the electric arc stiffness, supplement the N element loss of the weld, ensure the strength and toughness of the weld, and O2 can improve the electric arc stability. The multi-element protective gas can improve the forming condition of the austenitic welding material in the gas shielded arc welding, reduce welding defects and improve the strength and toughness of the weld by mixing in different proportions. The application can improve the proportion and size of the strengthening phase by controlling the composition of the welding wire, and further improve the strength and toughness of the weld.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a method for improving the welding quality of gas shielded welding of high-strength steel. Background Technology

[0002] When welding medium-thick plates (greater than 25mm) of high-strength steel, to avoid cold cracking, traditional methods generally use austenitic stainless steel welding materials and employ manual arc welding or argon arc welding. However, the traditional gas-shielded welding technology using austenitic welding wire is prone to problems such as poor molten pool fluidity and severe arc blow due to the composition of the shielding gas, resulting in poor weld formation and other welding defects. This reduces the strength and toughness of the weld metal and affects the joint performance. Summary of the Invention

[0003] The purpose of this invention is to provide a method for improving the welding quality of gas shielded welding of high-strength steel. The method of this invention can ensure good weld formation, reduce welding defects, and improve the strength and toughness of the weld.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for improving the welding quality of gas shielded welding of high-strength steel, comprising the following steps: using austenitic stainless steel welding wire as welding material, performing gas metal arc welding on high-strength steel under a protective atmosphere;

[0006] The protective atmosphere is provided by a multi-component protective gas; by volume percentage, the multi-component protective gas comprises 43-50% Ar, 43-50% He, 22-7% N, and 0-2% O, with Ar+He ≥ 93%.

[0007] Preferably, the austenitic stainless steel welding wire, by mass percentage, comprises: C 0.005%–0.08%, Cr 14%–23%, Mo 8%–17%, Nb 0.001%–5%, W 0.001%–5%, Si ≤0.5%, Mn 0.1%–0.9%, S ≤0.01%, P ≤0.01%, with the balance being Ni.

[0008] Preferably, the ratio of C / (Nb+W) in the austenitic stainless steel welding wire is 0.002 to 0.005.

[0009] Preferably, the multi-component protective gas comprises 50% Ar, 47% He, and 23% N.

[0010] This invention provides a method for improving the welding quality of gas-shielded high-strength steel, comprising the following steps: using austenitic stainless steel welding wire as welding material, performing gas metal arc welding on high-strength steel under a protective atmosphere; the protective atmosphere is provided by a multi-component protective gas; the multi-component protective gas comprises, by volume percentage, 43-50% Ar, 43-50% He, 22-7% N, and 0-2% O, and Ar+He≥93%.

[0011] This invention employs a multi-component protective gas, comprising, by volume, 43-50% Ar, 43-50% He, 2-7% N2, and 0-2% O2, with Ar+He ≥ 93%. Ar effectively isolates the weld from air, He contracts the arc and increases the arc temperature, N2 improves arc stiffness, compensates for the lack of nitrogen in the weld, ensuring weld strength and toughness, and O2 enhances arc stability. By mixing these multi-component protective gases in different proportions, the forming of austenitic welding materials in gas metal arc welding can be improved, welding defects reduced, and weld strength and toughness enhanced.

[0012] Furthermore, this invention controls the chemical elements of the welding wire within the following ranges: C 0.005%–0.08%, Cr 14%–23%, Mo 8%–17%, Nb 0.001%–5%, W 0.001%–5%, Si ≤0.5%, Mn 0.1%–0.9%, S ≤0.01%, P ≤0.01%, with the balance being Ni. This controls the composition of precipitated phases in the weld, reduces the precipitation of TCP (topologically close-packed) phases, and increases the NbC and Mn content. 23 The proportion of strengthening phases such as C6 is increased, thereby improving the strength of the weld. Simultaneously, the ratio of C to Nb+W in the weld metal is controlled within the range of 0.002 to 0.005. Within this range, smaller strengthening phases can be obtained, thus improving the toughness of the weld. Attached Figure Description

[0013] Figure 1 Macroscopic photograph of the weld seam using welding wire #1;

[0014] Figure 2 Macroscopic photograph of the weld seam using welding wire #2;

[0015] Figure 3 This is a macroscopic photograph of the weld seam of welding wire #3. Detailed Implementation

[0016] This invention provides a method for improving the welding quality of gas shielded welding of high-strength steel, comprising the following steps: using austenitic stainless steel welding wire as welding material, performing gas metal arc welding on high-strength steel under a protective atmosphere;

[0017] The protective atmosphere is provided by a multi-component protective gas; by volume percentage, the multi-component protective gas comprises 43-50% Ar, 43-50% He, 22-7% N, and 0-2% O, with Ar+He ≥ 93%.

[0018] In this invention, the high-strength steel refers to steel with a tensile strength > 360 MPa.

[0019] This invention does not specify the exact composition of the high-strength steel; any high-strength steel well-known in the art can be used. In the embodiments of this invention, the high-strength steel is specifically 800 MPa grade high-strength steel.

[0020] In this invention, the thickness of the high-strength steel is preferably >25mm, and in the embodiments of this invention, it is specifically 20mm.

[0021] In this invention, the austenitic stainless steel welding wire preferably comprises, by mass percentage: C 0.005%–0.08%, Cr 14%–23%, Mo 8%–17%, Nb 0.001%–5%, W 0.001%–5%, Si ≤0.5%, Mn 0.1%–0.9%, S ≤0.01%, P ≤0.01%, with the balance being Ni.

[0022] As a further preferred embodiment, the C is more preferably 0.01-0.07%, more preferably 0.02-0.05%; the Cr is more preferably 16-20%, more preferably 17-18%; the Mo is more preferably 10-15%, more preferably 12-13%; the Nb is more preferably 0.01-4.5%, more preferably 0.1-4%, and most preferably 1-3%; the W is more preferably 0.01-4.5%, more preferably 0.1-4%, and most preferably 1-3%; the Si is more preferably ≤0.4%; and the Mn is more preferably 0.2%-0.8%, more preferably 0.3-0.7%.

[0023] This invention controls the composition of precipitated phases in the weld by controlling the composition of the austenitic welding wire, thereby reducing the precipitation of TCP (topologically close-packed) phases and increasing the NbC and M content. 23 The proportion of strengthening phases such as C6 increases the strength of the weld.

[0024] In this invention, the C / (Nb+W) ratio in the austenitic stainless steel welding wire is preferably 0.002 to 0.005, more preferably 0.003 to 0.004. By controlling the C to Nb+W ratio in the weld metal, this invention can obtain a smaller strengthening phase, thereby improving the toughness of the weld.

[0025] This invention does not have special requirements for the specifications of the welding wire; any welding wire of specifications well known in the art can be used. In an embodiment of this invention, the diameter of the welding wire is 1.2 mm.

[0026] In this invention, the multi-component protective gas preferably comprises 50% Ar, 47% He, and 23% N. By employing the above-mentioned protective gas, Ar effectively isolates the weld from air, He contracts the arc and increases the arc temperature, N2 increases arc stiffness, compensates for the lack of nitrogen in the weld, ensuring weld strength and toughness, and O2 improves arc stability. By mixing the multi-component protective gas in different proportions, the forming of austenitic welding materials in gas metal arc welding can be improved, welding defects reduced, and weld strength and toughness increased.

[0027] This invention does not impose special requirements on the specific conditions for gas metal arc welding; welding conditions well-known in the art can be used. In the embodiments of this invention, for a base material of 20mm thick 800MPa grade high-strength steel, the multi-element shielding gas flow rate is 20L / min, the current is 180~210A, and the heat input is <10KJ / cm.

[0028] The following detailed description of the method for improving the welding quality of gas shielded welding of high-strength steel provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0029] Example 1

[0030] #1 austenitic welding wire, with a composition of 0.02% C, 23% Cr, 8.2% Mo, 4% Nb, 0.01% W, 0.2% Si, 0.48% Mn, 0.005% S, and 0.007% P, with the balance being Ni. The wire diameter is 1.2mm. The welding method is gas metal arc welding (MIG); the shielding gas is Ar + 47% He + 3% N2, with a gas flow rate of 20L / min, a current of 180-210A, and a heat input <10KJ / cm. The base metal is 40mm thick 800MPa grade high-strength steel, with a single-sided 30° V-groove, and an interpass temperature below 120℃. Weld observation revealed good weld formation quality, with no hot cracks, obvious spatter, voids, undercut, or other poor forming defects (such as…). Figure 1(As shown). The welded plate was cut and prepared to obtain one tensile specimen, conforming to GB / T2652-2008 standard. Nine impact specimens were prepared for side A (surface A being the pre-welded surface, side B the post-welded surface), with notches located at the weld center, fusion line, and heat-affected zone (three specimens each), and the average value was measured. Six impact specimens were prepared for side B, with notches located at the weld center and fusion line (three specimens each), and the average value was measured. The standard for these specimens was GB / T2650-2008. The side bending specimen conformed to GB / T2653-2008 standard, with an indenter diameter D (mm) = 120 mm and a bending angle of 180°. The test results showed that the tensile strength of the welded joint using #1 austenitic welding wire was 877 MPa. The average impact energy in each region was: side A weld average 134 J, fusion line 129 J, heat-affected zone 188 J; side B weld average 127 J, fusion line 129 J. The side bending test was successful.

[0031] Example 2

[0032] The No. 2 austenitic welding wire has the following composition: C 0.01%, Cr 14.3%, Mn 0.8%, Mo 17%, W 4%, Nb 1%, and all other elements meet the composition requirements. The wire diameter is 1.2 mm, and the welding method is gas metal arc welding (MIG). The shielding gas is Ar + 47% He + 3% N2, with a gas flow rate of 20 L / min, a current of 180–210 A, and a heat input of <10 KJ / cm. The base metal is 40 mm thick 800 MPa grade high-strength steel. A 30° V-groove is used on one side, and the interpass temperature is below 120℃. Observation of the weld revealed good weld formation quality, with no hot cracks, obvious spatter, voids, undercut, or other poor forming defects (such as…). Figure 2 (As shown). The welded plate was cut and prepared to obtain one tensile specimen, conforming to GB / T2652-2008 standard. Nine impact specimens were prepared for side A (side A being the pre-welded surface, side B the post-welded surface), with three specimens each having notches at the weld center, fusion line, and heat-affected zone; the average value was measured. Six impact specimens were prepared for side B, with three specimens each having notches at the weld center and fusion line; the average value was measured. The standard for these specimens was GB / T2650-2008. The side bending specimen conformed to GB / T2653-2008 standard, with an indenter diameter D (mm) = 120 mm and a bending angle of 180°. The test results showed that the tensile strength of the welded joint using #2 austenitic welding wire was 858 MPa. The average impact energy in each region was: side A weld average 96 J, fusion line 124 J, heat-affected zone 129 J; side B weld average 113 J, fusion line 106 J. The side bending test was successful.

[0033] Comparative Example 1

[0034] #3 austenitic welding wire, with the same composition as #1 welding wire, 1.2mm diameter, was used for welding with gas metal arc welding (MIG), employing 80% Ar + 20% CO2. The base metal was 40mm thick 800MPa grade high-strength steel. The gas flow rate was 20L / min, the current was 180-210A, and the heat input was <10KJ / cm. Welding tests showed significant spatter, severe arc blow, poor weld formation, and inability to form an effective weld (e.g., ...). Figure 3 (As shown).

[0035] Comparative Example 2

[0036] Compared to austenitic welding wire #4, the wire composition is 0.1% C, 0.65% Si, 25% Cr, 2.0% Mn, 5.5% Mo, 26% Ni, with the remainder being Fe. The wire diameter is 1.2 mm, and the welding method is gas metal arc welding (MIG). The shielding gas is Ar + 47% He + 3% N2, with a gas flow rate of 20 L / min, a current of 180–210 A, and a heat input of <10 KJ / cm. The base material is 40 mm thick 800 MPa high-strength steel, with a single-sided 30° V-groove and an interpass temperature below 120 °C. The welded plate was cut and a tensile test specimen was prepared, conforming to GB / T2652-2008. Nine impact test specimens were prepared on side A (side A being the first welded side, and side B being the second welded side), with three notches each located at the weld center, fusion line, and heat-affected zone. The average value was measured. Six samples were tested on side B, with three notches located at the weld center and three at the fusion line; the average value was measured. The standard for the samples was GB / T2650-2008. The standard for the side bending samples was GB / T2653-2008, with a pressure head diameter D (mm) = 120mm and a bending angle of 180°. The test results showed that the tensile strength of the welded joint of the comparison welding wire was 653 MPa, and the average impact energy of each region was: 76J for the weld on side A and 82J for the weld on side B, with side bending cracking occurring. The mechanical properties of the welded joint of the comparison welding wire #4 were inferior to those of the invented welding wire.

[0037] As can be seen from the above embodiments and comparative examples, the present invention can improve the weld formation quality by controlling the type of protective gas; and can further improve the strength and toughness of the weld by controlling the composition of the welding wire.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the welding quality of gas-shielded welding of high-strength steel, characterized in that, Includes the following steps: High-strength steel was subjected to gas metal arc welding under a protective atmosphere using austenitic welding wire as the welding material. The protective atmosphere is provided by a multi-component protective gas; by volume percentage, the multi-component protective gas comprises 50% Ar, 47% He, and 23% N; The austenitic welding wire comprises, by mass percentage: C 0.005%–0.08%, Cr 14%–23%, Mo 8%–17%, Nb 0.001%–5%, W 0.001%–5%, Si ≤0.5%, Mn 0.1%–0.9%, S ≤0.01%, P ≤0.01%, with the balance being Ni; the ratio of C / (Nb+W) in the austenitic welding wire is 0.002–0.005.

Images