A 500MPa solid welding wire to solve the problem of galvanized sheet welding porosity in the automotive industry

Abstract

The present invention provides a 500MPa solid welding wire for solving the welding porosity of galvanized sheet in the automobile industry. The weight percentage of the components of the solid welding wire is: C: 0.07-0.11%, Si: 0.30-0.70%, Mn: 1.00-1.35%, Cr≤0.30%, P<0.010%, S<0.005%, Ti: 0.03-0.08%, O≤0.004%, N≤0.002%, and the balance is iron and inevitable impurities. The 500MPa solid welding wire for solving the welding porosity of galvanized sheet in the automobile industry of the present invention determines the element composition range of C, Si, Mn, S, P and the like. The welding wire of the invention is used to weld 500MPa galvanized sheet, improve the welding porosity of galvanized sheet, the weld metal has excellent low-temperature impact toughness, the process performance of all-position welding is good, the weld surface is smooth and uniform, the weld bead morphology is beautiful, and it is suitable for welding 500MPa galvanized sheet.

Description

Technical Field

[0001] The invention belongs to the field of welding materials, and in particular relates to a 500MPa-level solid welding wire for solving welding pores of galvanized plates in the automobile industry. Background Art

[0002] Zinc is easily soluble in acid and alkali, so it is called an amphoteric metal. Zinc hardly changes in the air under normal conditions. Galvanizing refers to a surface treatment technology that coats a layer of zinc on the surface of metals, alloys or other materials to achieve aesthetic and rust-proof effects. Zinc is used as an isolation layer because the electrode potential of zinc is lower than that of iron, which is -0.762V and -0.44V respectively. Even if part of the zinc layer on the surface of steel is damaged, the intact zinc layer of other parts can still play a protective role as an electrochemical anode, and thus has been widely used. With the development of the automotive industry, there are increasingly higher requirements for lightweight and corrosion resistance of automobiles. Galvanized sheets can provide sufficient corrosion resistance while reducing weight. At present, galvanized steel sheets are widely used in automobile body-in-white, with a general overall application ratio of more than 60%. The main application parts are outer coverings, wheel arch inner panels, floor parts, engine compartments and other parts.

[0003] There are always problems with the welding quality of galvanized sheets. Since the boiling point of zinc (906℃) is much lower than the melting point of steel (about 1500℃), and the arc temperature of GMAW welding can usually reach more than 3000℃, galvanized sheets are prone to porosity, spatter and arc instability during welding. There are two feasible ways to solve the welding problem of galvanized sheets: 1. Develop more advanced arc welding technology, such as CMT (cold metal transition technology), which realizes droplet transition under 0 voltage state. When the short-circuit current is generated, the welding wire stops moving forward and automatically withdraws, the droplet enters the molten pool, the arc is extinguished, the voltage is 0, and the current decreases. In this way, the arc itself inputs heat in a very short process. When a short circuit occurs, the arc is extinguished, the heat input is rapidly reduced, and the alternation of hot and cold is realized, which further reduces the volatilization of zinc and avoids the risk of welding through the thin plate; 2. Another method uses GMAW (metal arc gas shielded welding) to adjust the welding process parameters, the proportion of shielding gas and the composition of the welding wire to improve the welding quality.

[0004] The main reason for the porosity defects of galvanized sheet when using gas shielded welding is that the heat input is too large, which causes the zinc layer on the surface of the galvanized sheet to evaporate, thereby forming zinc vapor, which continuously swallows and grows in the process of escaping from the molten pool. If it cannot be released from the molten pool in time, it will form porosity defects of varying sizes, affecting the welding quality. The problem can be solved from the perspective of the welding wire composition, reducing the S content to increase the surface tension of the molten pool, controlling the flow of the molten pool, and then reducing the Mn content to reduce the resistance of the welding wire, thereby increasing the welding current and improving the arc force. The zinc vapor is completely released and will not continue to remain until the molten pool is solidified. Summary of the invention

[0005] In view of this, the present invention aims to overcome the defects in the prior art and proposes a 500MPa-grade solid welding wire for solving the welding porosity of galvanized sheets in the automotive industry.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A 500MPa solid welding wire for solving the problem of galvanized sheet welding porosity in the automotive industry, wherein the weight percentage of the components of the solid welding wire is:

[0008] C: 0.07-0.11%,

[0009] Si: 0.30-0.70%,

[0010] Mn: 1.00-1.35%,

[0011] Cr≤0.30%,

[0012] P<0.010%,

[0013] S<0.005%,

[0014] Ti: 0.03-0.08%,

[0015] O≤0.004%,

[0016] N≤0.002%,

[0017] The balance is iron and inevitable impurities.

[0018] Preferably, the weight percentage of the components of the solid welding wire is:

[0019] C: 0.075%,

[0020] Si: 0.65%,

[0021] Mn: 1.35%,

[0022] Cr: 0.08%,

[0023] P: 0.010%,

[0024] S: 0.005%,

[0025] Ti: 0.05%,

[0026] O: 0.0027%,

[0027] N: 0.0012%,

[0028] The balance is iron and inevitable impurities.

[0029] Preferably, the weight percentage of the components of the solid welding wire is:

[0030] C: 0.074%,

[0031] Si: 0.42%,

[0032] Mn: 1.15%,

[0033] Cr: 0.15%,

[0034] P: 0.010%,

[0035] S: 0.004%,

[0036] Ti: 0.05%,

[0037] O: 0.0025%,

[0038] N: 0.0015%,

[0039] The balance is iron and inevitable impurities.

[0040] Furthermore, the solid welding wire is welded using 80% Ar+20% CO2 argon-rich mixed gas.

[0041] Furthermore, the yield strength Rel of the deposited metal of the solid welding wire is ≥500MPa, the tensile strength Rm is ≥400MPa, the elongation is ≥19%, and the impact energy at -40°C is ≥27J.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] The 500MPa solid welding wire for solving the welding porosity of galvanized sheets in the automotive industry of the present invention determines the composition ranges of elements such as C, Si, Mn, S, and P. The welding wire of the invention is used to weld 500MPa galvanized sheets, thereby improving the welding porosity of the galvanized sheets. The weld metal has excellent low-temperature impact toughness, good technical performance for all-position welding, a smooth and uniform weld surface, and beautiful weld bead morphology. The invention is suitable for welding 500MPa galvanized sheets.

[0044] The 500MPa-level solid welding wire for solving welding porosity of galvanized sheet in automobile industry is smelted by industrial converter, rolled by high-speed twist-free rolling mill, and drawn into finished welding wire, which is easy to realize in production.

[0045] The 500MPa solid welding wire for solving the welding porosity of galvanized sheet in the automobile industry of the present invention adopts 80% Ar+20% CO2 argon-rich mixed gas for welding, has small welding spatter, good arc stability and all-position operability, improves the welding porosity of galvanized sheet, has beautiful weld formation, and has excellent welding process performance of the welding wire.

[0046] The 500MPa-grade solid welding wire for solving welding porosity of galvanized sheet in the automobile industry is welded by 80% Ar+20% CO2 argon-rich mixed gas. The yield strength Rel of the deposited metal is ≥500MPa, the tensile strength Rm is ≥400MPa, the elongation is ≥19%, and the impact energy at -40°C is ≥27J.

[0047] The 500MPa-level solid welding wire for solving welding porosity of galvanized sheets in the automobile industry can replace imported welding wire, can significantly improve the welding quality of galvanized sheets, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the weld formation of the solid welding wire according to Example 1 of the present invention;

[0049] Figure 2 This is an X-ray flaw detection image of the solid welding wire described in Example 1 of the present invention;

[0050] Figure 3 This is a schematic diagram of the weld formation of the solid welding wire according to Example 2 of the present invention;

[0051] Figure 4 This is an X-ray flaw detection image of the solid welding wire described in Example 2 of the present invention. DETAILED DESCRIPTION

[0052] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0053] The solid welding wire of the present invention adopts desulfurized molten iron, controls the sulfur content of the molten iron entering the furnace, adopts converter steelmaking, selects raw materials with low S and P content, adopts top and bottom composite blowing process, controls C, S, P, O and N at the end of smelting at a relatively low level, and after deoxidation and alloying, adopts LF furnace and other furnace refining processes to smelt molten steel with components meeting the requirements, and the molten steel is cast into continuous casting billets through full protection of variety casting machine, and the continuous casting billets are rolled into Φ5.5mm wire rods through high-speed twist-free rolling mills. The wire rods are peeled, pickled, coated with borax, roughly drawn, finely drawn and copper-plated to make Φ1.2mm finished welding wires.

[0054] The present invention will be described in detail below with reference to the embodiments.

[0055] Example 1

[0056] A 500MPa-grade solid welding wire for solving welding porosity of galvanized sheets in the automotive industry. The components of the solid welding wire are as follows by weight: C: 0.075%, Si: 0.65%, Mn: 1.35%, Cr: 0.08%, P: 0.010%, S: 0.005%, Ti: 0.05%, O: 0.0027%, N: 0.0012%, and the balance is iron and unavoidable impurities.

[0057] The solid welding wire adopts 80% Ar+20% CO2 argon-rich mixed gas to weld galvanized steel plates. The test plate used in the test is a hot-dip galvanized steel plate with a size of 40mm×30mm×2mm and a grade of HC340LAD+Z for automobiles. The coating is double-sided galvanized with a galvanizing amount of 60g / m 2 The welding process parameters were determined as follows: the welding gun travel angle was tilted back by 10°, the welding shielding gas composition was Ar80%+CO220%, the welding current and voltage were 160A; 17V, the welding speed was 7mm / s, and the pulse was 10HZ, and the lap welding experiment was carried out.

[0058] like Figure 1-2 As shown, the welding wire has good forming effect, the surface oxide slag is moderate, the pore type is mostly pores within 1mm, and there are also 4 large pores larger than 1mm. According to the relevant requirements of GB / T 8110, the mechanical properties test of the deposited metal is carried out. The yield strength σs of the deposited metal is 465Mpa, the tensile strength σb is 556Mpa, the elongation of the deposited metal is 28%, and the impact energy AkV of the deposited metal at -40℃ is 120J.

[0059] Example 2

[0060] A 500MPa solid welding wire for solving welding porosity of galvanized sheet in the automobile industry. The components of the solid welding wire are as follows by weight: C: 0.074%, Si 0.42%, Mn: 1.15%, Cr: 0.15%, P: 0.010%, S: 0.004%, Ti: 0.05%, O: 0.0025%, N: 0.0015%, and the balance is iron and unavoidable impurities.

[0061] The welding wire adopts 80% Ar+20% CO2 argon-rich mixed gas for deposited metal welding. The material, specification, groove angle and welding process parameters of the test plate are the same as those in Example 1.

[0062] like Figure 3-4 As shown, the weld formation effect is good, there is less slag on the surface, and no pores are generated. According to the relevant requirements of GB / T8110, the mechanical properties test of the deposited metal is carried out, the yield strength of the deposited metal σs = 414Mpa, the tensile strength σb = 513Mpa, the elongation = 28%, and the impact energy of the deposited metal at -40℃ AkV = 146J.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A 500MPa solid welding wire for solving the problem of galvanized sheet welding porosity in the automotive industry, characterized by: The composition weight percentage of the solid welding wire is: C: 0.074%, Si: 0.42%, Mn: 1.15%, Cr: 0.15%, P: 0.010%, S: 0.004%, Ti: 0.05%, O: 0.0025%, N: 0.0015%, the balance is iron and inevitable impurities.

2. The 500MPa solid welding wire for solving welding porosity of galvanized sheet in the automotive industry according to claim 1 is characterized in that: The solid welding wire is welded by using 80% Ar+20% CO2 argon-rich mixed gas.

3. The 500MPa solid welding wire for solving welding porosity of galvanized sheet in the automotive industry according to claim 1 is characterized in that: The yield strength Rel of the deposited metal of the solid welding wire is ≥400MPa, the tensile strength Rm is ≥500MPa, the elongation is ≥19%, and the impact energy at -40°C is ≥27J.

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