A flux-cored wire for high-manganese low-temperature steel and a laser-arc hybrid welding method

Abstract

This invention provides a flux-cored welding wire for high-manganese low-temperature steel and a laser-arc composite welding method. The flux-cored welding wire comprises a steel strip sheath and a metal powder core filled within the sheath. The components and their percentages by mass of the metal powder core are as follows: lithium silicate 3-6%, electrolytic manganese 65-70%, molybdenum powder 2-4%, nickel powder 1-3%, chromium carbide 7-10%, and the balance being iron powder. This flux-cored welding wire for high-manganese low-temperature steel exhibits excellent comprehensive mechanical and welding process properties. The weld metal has the following mechanical properties: tensile strength ≥700MPa, yield strength ≥400MPa, elongation ≥40%, Akv ≥80J at -196℃, and the weld CTOD test characteristic value meets the standard requirements (≥0.2mm). It also demonstrates excellent crack resistance.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a flux-cored welding wire for high-manganese low-temperature steel and a laser-arc composite welding method. Background Technology

[0002] In recent years, due to the steady growth in market demand for liquefied natural gas (LNG) carriers and LNG-powered vessels, high-manganese cryogenic steel, a new type of LNG storage tank manufacturing material with lower costs, is becoming a market hotspot. High-manganese cryogenic steel possesses excellent low-temperature performance, exhibiting good impact toughness at -196°C, and can replace currently widely used cryogenic metals such as 9-nickel steel, 5-nickel steel, stainless steel, and aluminum alloys. Furthermore, due to the abundant availability of manganese on Earth, the cost of high-manganese cryogenic steel is significantly lower than other cryogenic metals, offering clear advantages for large-scale applications. However, the large-scale application of high-manganese cryogenic steel still requires addressing many issues, such as the difficulty of welding and the environmental pollution caused by welding fumes. Of particular concern is the health hazards of manganese vapor.

[0003] Laser-arc hybrid welding, as a novel welding technology, utilizes both laser and electric arc as dual heat sources, acting simultaneously on the same molten pool. This forms a laser-guided and stabilized arc, while the arc enhances the metal's absorption of the laser, strengthening the bridging ability of the molten droplets. This welding method boasts numerous advantages, including high welding efficiency, good weld quality, minimal welding fumes, and minimal welding deformation. Chinese patent CN114289930A discloses a solid welding wire and welding process for laser-arc hybrid welding of high-manganese austenitic low-temperature steel. It develops a solid welding wire specifically for high-manganese austenitic low-temperature steel, which, when used with a suitable laser-arc hybrid welding process, can be applied to the welding of this steel. However, using the solid welding wire during welding presents defects such as excessive spatter, affecting weld formation, increasing surface cleaning workload, and reducing production efficiency.

[0004] Flux-cored welding wire effectively reduces or avoids problems such as spatter, poor weld formation, and excessively hard arc. It offers advantages such as high deposition efficiency, minimal spatter, excellent weld joint quality, aesthetically pleasing weld formation, low overall cost, and suitability for all-position automated welding. Furthermore, its composition is highly adjustable; the flux core composition can be easily designed and proportioned according to different performance requirements, making it more flexible. Currently, no flux-cored welding wire suitable for laser-arc hybrid welding of high-manganese cryogenic steel has been found, which will be one of the bottlenecks in achieving large-scale application of high-manganese cryogenic steel in the shipbuilding industry. Summary of the Invention

[0005] The purpose of this invention is to provide a flux-cored welding wire for high-manganese low-temperature steel, which improves the defects of solid welding wire such as large spatter, and obtains a welded joint with good forming and mechanical properties that meet the performance requirements of high-manganese low-temperature steel.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A flux-cored welding wire for high-manganese low-temperature steel includes a steel strip outer sheath and a metal powder core filled inside the steel strip outer sheath. The components of the metal powder core and their contents as a percentage of the metal powder core by mass are as follows: lithium silicate 3-6%, electrolytic manganese 65-70%, molybdenum powder 2-4%, nickel powder 1-3%, chromium carbide 7-10%, and the balance being iron powder.

[0008] Furthermore, the mass of the metal powder core is 25-30% of the total mass of the flux-cored wire.

[0009] Furthermore, the mass percentage of C in the chromium carbide is 12-14%, and the mass percentage of Cr is 82-86%.

[0010] Furthermore, the outer sheath of the steel strip is made of SPCC steel strip.

[0011] Specifically, the components of the metal powder core and their percentage by mass are as follows: lithium silicate 5%, electrolytic manganese 70%, molybdenum powder 2%, nickel powder 1%, chromium carbide 7%, and the remainder is iron powder.

[0012] Specifically, the components of the metal powder core and their percentage content relative to the mass of the metal powder core are as follows: lithium silicate 3%, electrolytic manganese 68%, molybdenum powder 4%, nickel powder 2%, chromium carbide 10%, and the balance being iron powder.

[0013] Specifically, the components of the metal powder core and their percentage content relative to the mass of the metal powder core are as follows: lithium silicate 6%, electrolytic manganese 65%, molybdenum powder 3%, nickel powder 3%, chromium carbide 9%, and the balance being iron powder.

[0014] In addition, the present invention also provides a laser-arc hybrid welding method for high-manganese low-temperature steel, which uses the above-mentioned flux-cored welding wire for high-manganese low-temperature steel. The welding process conditions are as follows: laser power of 3-8kW, defocusing amount of ±10mm, and wire spacing of 4-8mm; arc voltage of 23-28V, welding current of 150-200A, welding speed of 0.8-2.0m / min, and wire extension of 15mm-20mm; shielding gas flow rate of 15-20L / min.

[0015] Furthermore, the protective gas is a mixture of argon and carbon dioxide, with CO2 accounting for 15-20% of the volume and the remainder being Ar.

[0016] The design principle of the flux-cored welding wire for high-manganese low-temperature steel provided by this invention is as follows:

[0017] Lithium silicate is mainly composed of SiO2 and Li2O. SiO2 is also the main component of slag, and it can adjust the melting point and viscosity of the slag, increase the arc voltage, refine the molten droplets, reduce welding spatter, and improve weld formation. Li2O contains Li... + It can improve arc stability, reduce spatter, significantly improve welding process, replace substances containing K and Na elements, and significantly reduce dust generation. In this invention, when the amount of lithium silicate added is greater than 6%, the low-temperature toughness of the weld gradually decreases with the increase of SiO2 content, while when the amount of lithium silicate added is less than 3%, the welding process performance deteriorates. Therefore, in this invention, the amount of lithium silicate added is controlled to be 3-6%.

[0018] Mn in electrolytic manganese is an element that expands the austenite region and stabilizes the austenite structure. When the Mn content in the weld metal is greater than 20%, a fully austenitic structure can be formed, the low-temperature brittle transition temperature disappears, and the low-temperature impact toughness of the weld metal is improved. At the same time, electrolytic manganese can also participate in deoxidation to reduce the oxygen content of the weld metal and increase the strength and crack resistance of the weld metal. In this invention, the optimal addition amount of electrolytic manganese is controlled to be 65-70%.

[0019] In molybdenum powder, Mo is dissolved in austenite or exists in the form of strong carbides in the weld, thereby improving the weld strength. Mo can also reduce the solid-liquid coexistence range, which can effectively inhibit the occurrence of hot cracks.

[0020] Ni in nickel powder can lower the low-temperature brittle transition temperature and has a solid solution strengthening effect, which can improve the strength and low-temperature impact toughness of weld metal; at the same time, adding an appropriate amount of Ni can improve its corrosion resistance in saline atmospheres.

[0021] In chromium carbide, carbon (C) is an austenitizing element that can form carbides with chromium (Cr) and molybdenum (Mo) to improve the strength of austenitic weld metal. Cr can form a dense oxide film on the surface of steel, increasing the electrode potential and producing a passivation effect. Because Cr can partially replace Fe to form ferrochromium hydroxyl oxides, the rust layer has cation selectivity, inhibiting the growth of chloride ions (Cl). - SO4 2- It penetrates into the substrate surface, thus providing a protective layer of rust.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The flux-cored welding wire for high manganese low temperature steel provided by the present invention adopts a metal powder core transition alloy, which has a simple alloy composition system and high deposition efficiency; and when selecting raw materials for the metal powder core, substances containing K and Na elements that are prone to generating dust are avoided as much as possible, thereby significantly reducing dust.

[0024] (2) The flux-cored welding wire for high manganese low temperature steel provided by the present invention has excellent comprehensive mechanical properties and welding process properties. The mechanical properties of its weld metal are tensile strength ≥700MPa; yield strength ≥400MPa; elongation ≥40%; Akv ≥80J under -196℃ conditions, the characteristic value of the weld CTOD test meets the standard requirements (≥0.2mm), and has excellent crack resistance.

[0025] (3) The laser-arc composite welding method for high-manganese low-temperature steel provided by this invention can give full play to the advantages of laser welding and arc welding, while avoiding their own shortcomings. Moreover, the synergistic effect of the two heat sources makes the laser-arc composite welding achieve a 1+1>2 effect, which improves the deposition efficiency, thereby improving the production efficiency, and also reduces welding deformation, improves weld formation, and improves welding quality. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the following embodiments, the thickness of the high-manganese low-temperature steel welded is less than 20mm, without beveling, and directly butt welded, with a butt gap of 0-2mm.

[0028] Example 1:

[0029] This embodiment provides a flux-cored welding wire for high-manganese low-temperature steel, comprising a steel strip outer sheath and a metal powder core filled within the steel strip outer sheath. The steel strip outer sheath is made of SPCC steel strip. The components and their percentages by mass of the metal powder core are as follows: lithium silicate 5%, electrolytic manganese 70%, molybdenum powder 2%, nickel powder 1%, chromium carbide 7%, and the balance being iron powder. The mass of the metal powder core is 25% of the total mass of the flux-cored welding wire. In this embodiment, the flux-cored welding wire for high-manganese low-temperature steel is manufactured using a conventional flux-cored welding wire manufacturing process, the specific manufacturing process of which will not be detailed here.

[0030] Laser-arc hybrid welding was performed on high-manganese low-temperature steel using the flux-cored welding wire prepared in this embodiment. The welding process conditions were as follows: laser power of 3kW, defocusing distance of +10mm, and wire spacing of 8mm; arc voltage of 23V, welding current of 150A, welding speed of 2.0m / min, and wire extension of 20mm; the shielding gas flow rate was 15L / min, and the shielding gas was a mixture of Ar and CO2, with CO2 accounting for 20% by volume and the balance being Ar. The high-manganese low-temperature steel plate being welded was 8mm thick, and butt welding was performed without beveling or leaving a butt joint gap.

[0031] The mechanical properties of the weld metal after laser-arc hybrid welding using the flux-cored welding wire for high-manganese low-temperature steel in this embodiment were tested. The mechanical properties of the weld metal were as follows: tensile strength of 718 MPa, yield strength of 510 MPa, elongation of 42%, average Akv value of 104 J at -196℃, and CTOD characteristic value of 0.48 mm at -165℃.

[0032] Example 2:

[0033] This embodiment provides a flux-cored welding wire for high-manganese low-temperature steel, comprising a steel strip sheath and a metal powder core filled within the steel strip sheath. The steel strip sheath is made of SPCC steel strip. The components and their percentages by mass of the metal powder core are as follows: lithium silicate 3%, electrolytic manganese 68%, molybdenum powder 4%, nickel powder 2%, chromium carbide 10%, and the balance being iron powder. The mass of the metal powder core is 30% of the total mass of the flux-cored welding wire. In this embodiment, the flux-cored welding wire for high-manganese low-temperature steel is manufactured using a conventional flux-cored welding wire manufacturing process, the specific manufacturing process of which will not be detailed here.

[0034] Laser-arc hybrid welding was performed on high-manganese low-temperature steel using the flux-cored welding wire prepared in this embodiment. The welding process conditions were as follows: laser power of 8kW, defocusing amount of -10mm, and wire spacing of 4mm; arc voltage of 28V, welding current of 200A, welding speed of 0.8m / min, and wire extension of 15mm; the shielding gas flow rate was 20L / min, and the shielding gas was a mixture of Ar and CO2, with CO2 accounting for 15% by volume and the balance being Ar. The high-manganese low-temperature steel plate being welded was 20mm thick, and butt welding was performed without beveling, with a butt gap of 2mm.

[0035] The mechanical properties of the weld metal after laser-arc hybrid welding using the flux-cored welding wire for high-manganese low-temperature steel in this embodiment were tested. The mechanical properties of the weld metal were as follows: tensile strength of 708 MPa, yield strength of 521 MPa, elongation of 40.5%, average Akv value of 93 J at -196℃, and CTOD characteristic value of 0.52 mm at -165℃.

[0036] Example 3:

[0037] This embodiment provides a flux-cored welding wire for high-manganese low-temperature steel, comprising a steel strip sheath and a metal powder core filled within the steel strip sheath. The steel strip sheath is made of SPCC steel strip. The components and their percentages by mass of the metal powder core are as follows: lithium silicate 6%, electrolytic manganese 65%, molybdenum powder 3%, nickel powder 3%, chromium carbide 9%, with the balance being iron powder. The mass of the metal powder core is 28% of the total mass of the flux-cored welding wire. In this embodiment, the flux-cored welding wire for high-manganese low-temperature steel is manufactured using a conventional flux-cored welding wire manufacturing process, the specific manufacturing process of which will not be detailed here.

[0038] Laser-arc hybrid welding was performed on high-manganese low-temperature steel using the flux-cored welding wire prepared in this embodiment. The welding process conditions were as follows: laser power of 6kW, defocusing amount of 0mm, and wire spacing of 6mm; arc voltage of 26V, welding current of 180A, welding speed of 1.4m / min, and wire extension of 17mm; the shielding gas flow rate was 18L / min, and the shielding gas was a mixture of Ar and CO2, with CO2 accounting for 16% by volume and the balance being Ar. The high-manganese low-temperature steel plate being welded was 14mm thick, and butt welding was performed without beveling, with a butt gap of 1mm.

[0039] The mechanical properties of the weld metal after laser-arc hybrid welding using the flux-cored welding wire for high-manganese low-temperature steel in this embodiment were tested. The mechanical properties of the weld metal were as follows: tensile strength of 712 MPa, yield strength of 513 MPa, elongation of 41%, average Akv value of 106 J at -196℃, and CTOD characteristic value of 0.53 mm at -165℃.

[0040] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A flux-cored welding wire for high-manganese low-temperature steel, characterized in that, The device includes a steel strip outer sheath and a metal powder core filled within the steel strip outer sheath. The components and their contents as a percentage of the metal powder core's mass are as follows: lithium silicate 3-6%, electrolytic manganese 65-70%, molybdenum powder 2-4%, nickel powder 1-3%, chromium carbide 7-10%, and the balance being iron powder. This flux-cored welding wire is used in conjunction with laser-arc composite welding of high-manganese low-temperature steel, a material used in the manufacture of LNG storage tanks.

2. The flux-cored welding wire for high-manganese low-temperature steel as described in claim 1, characterized in that: The mass of the metal powder core is 25-30% of the total mass of the flux-cored welding wire.

3. The flux-cored welding wire for high-manganese low-temperature steel as described in claim 1, characterized in that: The chromium carbide contains 12-14% C by mass and 82-86% Cr by mass.

4. The flux-cored welding wire for high-manganese low-temperature steel as described in claim 1, characterized in that: The outer sheath of the steel strip is made of SPCC steel strip.

5. The flux-cored welding wire for high-manganese low-temperature steel as described in any one of claims 1 to 4, characterized in that: The components of the metal powder core and their percentage by mass are as follows: lithium silicate 5%, electrolytic manganese 70%, molybdenum powder 2%, nickel powder 1%, chromium carbide 7%, and the remainder is iron powder.

6. The flux-cored welding wire for high-manganese low-temperature steel as described in any one of claims 1 to 4, characterized in that: The components of the metal powder core and their percentage by mass are as follows: lithium silicate 3%, electrolytic manganese 68%, molybdenum powder 4%, nickel powder 2%, chromium carbide 10%, and the remainder is iron powder.

7. The flux-cored welding wire for high-manganese low-temperature steel as described in any one of claims 1 to 4, characterized in that: The components of the metal powder core and their percentage content relative to the mass of the metal powder core are as follows: lithium silicate 6%, electrolytic manganese 65%, molybdenum powder 3%, nickel powder 3%, chromium carbide 9%, and the balance being iron powder.

8. A method for laser-arc hybrid welding of high-manganese low-temperature steel, characterized in that, Welding is performed using the flux-cored welding wire for high-manganese low-temperature steel as described in any one of claims 1 to 7. The welding process conditions are as follows: laser power is 3 to 8 kW, defocusing amount is ±10 mm, and wire spacing is 4 to 8 mm; arc voltage is 23 to 28 V, welding current is 150 to 200 A, welding speed is 0.8 to 2.0 m / min, and wire extension is 15 mm to 20 mm; shielding gas flow rate is 15 to 20 L / min.

9. The laser-arc hybrid welding method for high-manganese low-temperature steel as described in claim 8, characterized in that, The protective gas is a mixture of argon and carbon dioxide, with CO2 accounting for 15-20% of the volume and the remainder being Ar.