A flux-cored welding wire for mixed gas shielded welding and a method of using the same

Abstract

The invention belongs to the technical field of welding materials, and specifically provides a flux-cored welding wire for mixed gas shielded welding, comprising an outer skin and a flux core filled in the outer skin, wherein the outer skin is a steel strip; the flux core comprises, by mass percentage, 38-42% of rutile, 8-12% of calcium feldspar, 3-4% of magnesium powder, 8-10% of metallic manganese, 15-16% of ferrosilicon, 5-7% of ferrotitanium, 0.1-0.3% of ferroboron, 3-4.5% of nickel powder, 3-5% of fluorite, and the remainder is iron powder and inevitable impurities. The flux-cored welding wire for mixed gas shielded welding provided by the present invention has good low-temperature toughness, and the yield strength of the deposited metal is ≥460MPa; the tensile strength is ≥550MPa; the elongation is ≥22%; under the condition of -60°C, KV2 is ≥54J, the deposited metal has good resistance to sulfide stress corrosion cracking, uses argon-rich mixed gas for protection, has slag protection during the welding process, has good all-position welding processability, and has good weld formation, and can be used for low-temperature high-strength steel welding that requires resistance to sulfide stress corrosion cracking.

Description

Technical Field

[0001] The invention belongs to the technical field of welding materials, and in particular relates to a flux-cored welding wire for mixed gas shielded welding and a use method thereof. Background Art

[0002] In the oil extraction industry such as offshore oil engineering, pipelines that transport oil and gas often suffer from stress corrosion cracking due to H2S in the oil and gas. In order to prevent similar accidents, performance requirements for resistance to sulfide stress corrosion cracking have been proposed, and the strength grade of pipeline steel has been continuously improved. For example, the strength grade of steel grades that resist sulfide stress corrosion cracking has been increased from a yield strength of 345MPa to more than 450MPa. In order to eliminate the risk of increased weld brittleness caused by increased thickness and increased strength grade, higher requirements have been put forward for weld low-temperature toughness.

[0003] The prior art also provides some solutions for welding materials, such as CN201910568603.4 provides a low sulfur and phosphorus steel welding rod for hydrogen sulfide corrosion resistance and preparation method, but it discloses a welding rod with a yield strength of only 402MPa, and only describes the impact absorption work at -30°C, which cannot meet the actual needs. CN201310015784.0 provides a metal powder type flux-cored welding wire and preparation method with high toughness and resistance to hydrogen-induced and sulfide stress corrosion cracking, and describes a metal powder type flux-cored welding wire, which "effectively reduces the amount of slag after welding in terms of process", that is, there is only a small amount of slag, so the welding process performance in all positions is poor, and only describes the impact at -30°C reaching 60J, and the yield strength ≥400MPa. CN202011217167.5 provides a gas shielded welding wire and welding method for improving the performance of the air cooler pipe head weld, and the welding wire described is a gas shielded welding wire, that is, a solid welding wire, which is not the same type of product as the flux-cored welding wire. Summary of the invention

[0004] The purpose of the present invention is to provide a titanium type slag system mixed gas shielded welding flux cored wire, which has good all-position welding process performance and can meet the performance requirements of resistance to sulfide stress corrosion cracking.

[0005] To this end, the present invention provides a flux-cored welding wire for mixed gas shielded welding, comprising an outer skin and a flux core filled in the outer skin, wherein the outer skin is a steel strip; in terms of mass percentage, the flux core comprises 38-42% of rutile, 8-12% of calcium feldspar, 3-4% of magnesium powder, 8-10% of metallic manganese, 15-16% of ferrosilicon, 5-7% of ferrotitanium, 0.1-0.3% of ferroboron, 3-4.5% of nickel powder, 3-5% of fluorite, and the remainder is iron powder and inevitable impurities.

[0006] Specifically, in the above steel strip, S≤0.007%, and P≤0.009%.

[0007] Specifically, the flux core accounts for 16-17% of the mass of the flux cored welding wire.

[0008] Specifically, the above-mentioned core includes 38% rutile, 11% calcium feldspar, 4% magnesium powder, 8% metallic manganese, 15.2% ferrosilicon, 7% ferrotitanium, 0.2% ferroboron, 4.3% nickel powder, 5% fluorite, and the rest is iron powder and inevitable impurities.

[0009] Specifically, the above-mentioned core includes 42% rutile, 9% calcium feldspar, 3.5% magnesium powder, 9.5% metallic manganese, 16% ferrosilicon, 5% ferrotitanium, 0.1% ferroboron, 3.0% nickel powder, 3.5% fluorite, and the rest is iron powder and inevitable impurities.

[0010] Specifically, the above-mentioned core includes 39% rutile, 12% calcium feldspar, 4% magnesium powder, 10% metallic manganese, 15.3% ferrosilicon, 6% ferrotitanium, 0.3% ferroboron, 4.5% nickel powder, 4% fluorite, and the rest is iron powder and inevitable impurities.

[0011] The present invention also provides a method for using the above-mentioned flux-cored welding wire for mixed gas shielded welding: the flux-cored welding wire for mixed gas shielded welding uses 80% Ar+20% CO2 argon-rich mixed gas as shielding gas, welding current 250-260A; welding voltage 26-28V; welding speed 30mm / min.

[0012] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0013] The flux-cored welding wire for mixed gas shielded welding provided by the present invention has good low-temperature toughness, yield strength of deposited metal ≥460MPa; tensile strength ≥550MPa; elongation ≥22%; KV2 ≥54J under -60°C, and the deposited metal has good resistance to sulfide stress corrosion cracking. The flux-cored welding wire for mixed gas shielded welding provided by the present invention uses argon-rich mixed gas for protection, has slag protection during welding, has good all-position welding processability, and has good weld formation, and can be used for low-temperature high-strength steel welding that requires resistance to sulfide stress corrosion cracking. DETAILED DESCRIPTION

[0014] The technical scheme in the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Although the representative embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be limited by the attached claims and their equivalents.

[0015] The invention provides a flux-cored welding wire for mixed gas shielded welding, comprising an outer skin and a flux core filled in the outer skin, wherein the outer skin is a steel strip, S≤0.007% and P≤0.009% in the steel strip; in terms of mass percentage, the flux core comprises 38-42% of rutile, 8-12% of calcium feldspar, 3-4% of magnesium powder, 8-10% of metallic manganese, 15-16% of ferrosilicon, 5-7% of ferrotitanium, 0.1-0.3% of ferroboron, 3-4.5% of nickel powder, 3-5% of fluorite, and the remainder is iron powder and unavoidable impurities. The flux core accounts for 16-17% of the mass of the flux-cored welding wire.

[0016] Among them, the main component of rutile used is TiO2, containing more than 95% TiO2, the main function is slag formation, can improve slag removal, and significantly affect vertical welding forming. When rutile is less than 38%, the amount of slag is too small and the melting point of slag is too low, the weld pool "molten iron" is easy to flow, the forming is not good, and the vertical welding operation is difficult; when rutile is more than 42%, the material cost increases, and due to excessive TiO2 content, the melting point will increase, and the weld forming will deteriorate.

[0017] The composition of calcium feldspar is CaO·Al2O3·2SiO2, of which CaO is about 20.1%, Al2O3 is about 36.7%, and SiO2 is about 43.2%. Calcium feldspar has the advantages of small dielectric constant, low thermal expansion coefficient, small bulk density, high specific strength, and low sintering temperature. It can promote the formation of calcium sulfide complexes in welding metallurgical reactions, avoid or reduce the formation of manganese sulfide, and thus improve the resistance of weld metal to sulfide stress corrosion cracking.

[0018] The main function of magnesium powder is deoxidation and reducing the oxygen content of the weld. The generated magnesium oxide can increase the basicity of the slag and reduce the acid inclusions of the weld metal. However, when the magnesium powder is less than 3%, the purifying effect on the molten pool is not obvious and the low-temperature toughness is poor; when it is higher than 4%, it will significantly affect the melting point of the slag, resulting in poor performance of the vertical welding process.

[0019] The main function of metallic manganese is alloying. Too much Mn will reduce the ability of the weld metal to resist sulfide stress corrosion cracking.

[0020] Ferrosilicon contains a large amount of Si, which can improve the strength of the weld as the main alloying element of the weld metal. It can also be used as a deoxidizer to form composite silicates with CaO\MgO in the slag. When there is too much ferrosilicon, the Si content of the weld metal will be too high, and the low-temperature impact toughness of the weld will be significantly reduced.

[0021] Ferro-titanium contains a large amount of Ti, which mainly participates in deoxidation. Under a suitable oxygen content environment, it can be oxidized to form TiO, which can serve as a crystal nucleation point, and at the same time can inhibit the oxidation of B and improve the low-temperature impact toughness of the weld. When its content is less than 5%, the Ti content in the weld is insufficient and the low-temperature impact toughness is low; when it is greater than 7%, the Ti content in the weld is too much, the weld strength is too high, and the low-temperature impact toughness will also be significantly reduced.

[0022] Ferroboron contains about 19% B. By infiltrating B into the weld, the grains are refined and the low-temperature toughness is improved.

[0023] The main function of nickel powder is to alloy the weld metal and reduce the toughness-brittle transition temperature of the weld metal. When the nickel powder is less than 3%, the weld toughness is insufficient; but adding too much nickel powder will significantly increase the cost of raw materials.

[0024] Fluorite contains a large amount of CaF2, which can reduce the hydrogen content of the weld metal in the welding metallurgical reaction, promote the formation of calcium sulfide complexes, reduce the formation of manganese sulfide, and improve the weld metal's resistance to sulfide stress corrosion. However, too much fluorite will cause unstable welding arc and deteriorate welding process performance.

[0025] The flux-cored welding wire for mixed gas shielded welding provided by the invention adopts 80% Ar+20% CO2 argon-rich mixed gas as shielding gas, with a welding current of 250-260A, a welding voltage of 26-28V and a welding speed of 30mm / min.

[0026] The effects of the flux-cored welding wire for mixed gas shielded welding and the method for using the same of the present invention are studied below through specific examples.

[0027] Embodiment 1:

[0028] This embodiment provides a flux-cored welding wire for mixed gas shielded welding, the outer skin of which is a SPCC steel strip, and the chemical composition thereof includes: S content 0.0062%, P content 0.008% (mass percentage). The distribution ratio of each component of the flux core and the filling rate of the flux core in the flux core welding wire are shown in Table 1.

[0029] The flux-cored wire for mixed gas shielded welding uses 80% Ar+20% CO2 argon-rich mixed gas as shielding gas, welding current 250-260A; welding voltage 26-28V; welding speed 30mm / min. The chemical composition and mechanical properties of the deposited metal were tested, and the results are shown in Table 2.

[0030] Embodiment 2:

[0031] This embodiment provides a flux-cored welding wire for mixed gas shielded welding, the outer skin of which is a SPCC steel strip, and the chemical composition thereof includes: S content 0.0062%, P content 0.008% (mass percentage). The proportions of each component of the flux core are shown in Table 1.

[0032] The flux-cored wire for mixed gas shielded welding uses 80% Ar+20% CO2 argon-rich mixed gas as shielding gas, welding current 250-260A; welding voltage 26-28V; welding speed 30mm / min. The chemical composition and mechanical properties of the deposited metal were tested, and the results are shown in Table 2.

[0033] Embodiment 3:

[0034] This embodiment provides a flux-cored welding wire for mixed gas shielded welding, the outer skin of which is a SPCC steel strip, and the chemical composition thereof includes: S content 0.0062%, P content 0.008% (mass percentage). The proportions of each component of the flux core are shown in Table 1.

[0035] The flux-cored wire for mixed gas shielded welding uses 80% Ar+20% CO2 argon-rich mixed gas as shielding gas, welding current 250-260A; welding voltage 26-28V; welding speed 30mm / min. The chemical composition and mechanical properties of the deposited metal were tested, and the results are shown in Table 2.

[0036] Table 1 Drug core ratio and filling rate (mass percentage) in each embodiment

[0037]

[0038]

[0039] Table 2 Chemical composition and mechanical properties of deposited metal in each embodiment

[0040]

[0041] As can be seen from Table 1 and Table 2, the flux-cored welding wire for mixed gas shielded welding provided by the present invention has good low-temperature toughness, the yield strength of the deposited metal is ≥460MPa; the tensile strength is ≥550MPa; the elongation is ≥22%; under the condition of -60°C, KV2 is ≥54J, and the deposited metal has good resistance to sulfide stress corrosion cracking. The flux-cored welding wire for mixed gas shielded welding provided by the present invention uses argon-rich mixed gas for protection, and the welding process is protected by slag, has good all-position welding processability, and has good weld formation, and can be used for low-temperature high-strength steel welding that requires resistance to sulfide stress corrosion cracking.

[0042] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A flux-cored welding wire for mixed gas shielded welding, comprising an outer sheath and a flux core filled in the outer sheath, Features: The outer skin is a steel strip; in terms of mass percentage, the core comprises 38-42% rutile, 8-12% calcium feldspar, 3-4% magnesium powder, 8-10% metallic manganese, 15-16% ferrosilicon, 5-7% ferrotitanium, 0.1-0.3% ferroboron, 3-4.5% nickel powder, 3-5% fluorite, and the remainder is iron powder and inevitable impurities.

2. The flux-cored welding wire for mixed gas shielded welding according to claim 1, Features: In the steel strip, S≤0.007%, and P≤0.009%.

3. The flux-cored welding wire for mixed gas shielded welding according to claim 1, Features: The flux core accounts for 16-17% of the mass of the flux cored welding wire.

4. The flux-cored welding wire for mixed gas shielded welding according to claim 1, Features: The core comprises 38% rutile, 11% calcium feldspar, 4% magnesium powder, 8% metallic manganese, 15.2% ferrosilicon, 7% ferrotitanium, 0.2% ferroboron, 4.3% nickel powder, 5% fluorite, and the rest is iron powder and inevitable impurities.

5. The flux-cored welding wire for mixed gas shielded welding according to claim 1, Features: The core comprises 42% rutile, 9% calcium feldspar, 3.5% magnesium powder, 9.5% metallic manganese, 16% ferrosilicon, 5% ferrotitanium, 0.1% ferroboron, 3.0% nickel powder, 3.5% fluorite, and the rest is iron powder and inevitable impurities.

6. The flux-cored welding wire for mixed gas shielded welding according to claim 1, Features: The core comprises 39% rutile, 12% calcium feldspar, 4% magnesium powder, 10% metallic manganese, 15.3% ferrosilicon, 6% ferrotitanium, 0.3% ferroboron, 4.5% nickel powder, 4% fluorite, and the rest is iron powder and inevitable impurities.

7. A method for using a flux-cored welding wire for mixed gas shielded welding according to any one of claims 1 to 6, Features: The flux-cored welding wire for mixed gas shielded welding adopts 80% Ar+20% CO 2 The argon-rich mixed gas is used as the shielding gas, the welding current is 250-260A; the welding voltage is 26-28V; the welding speed is 30mm / min.

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