A flux-cored wire for high-speed flat and fillet welding and use thereof

Abstract

This invention provides a flux-cored welding wire for high-speed flat welding and fillet welding and its application. The flux-cored welding wire includes a carbon steel outer sheath and a flux core. The flux core includes the following components by mass percentage: barium fluoride 0.5-1%, rutile 10-20%, aluminum oxide 2-4%, magnesia 2-3%, ferrotitanium 1-2%, ferroboron 2-4%, ferroaluminum 1-2%, quartz 1-2%, bismuth oxide 0.1-0.3%, with the balance being Fe and unavoidable impurities. This invention addresses the shortcomings of existing welding wires, such as inability to meet the requirements of high-speed flat welding, easy porosity in zinc-rich primer welding, poor low-temperature toughness, and high diffusible hydrogen content. By constructing a synergistic metallurgical system of "barium fluoride dehydrogenation + titanium-silicon-aluminum-magnesium composite thin slag system + titanium-boron-aluminum composite deoxidation and grain refinement + trace bismuth oxide deslag removal", no porosity is generated when welding on zinc-rich primer plates at a welding speed of 1000-1200 mm / min, and the weld formation is beautiful; the deposited metal at -20℃ KV₂≥80J, elongation≥26%, and diffusible hydrogen<5.0mL / 100g.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a flux-cored welding wire for high-speed flat welding and fillet welding and its application. Background Technology

[0002] With the widespread application of automated welding technology in shipbuilding, bridge engineering, and heavy steel structures, high-speed flat welding and fillet welding have become key processes for improving production efficiency. Unlike general position welding, high-speed fillet welding (welding speed typically ≥1000mm / min) faces the following unique challenges: 1) The welding speed is extremely fast, the molten pool exists for a very short time, and the gas escape window is significantly compressed. If the slag system has excessively high viscosity or insufficient permeability, porosity defects are easily formed in the weld; especially when a zinc-rich primer (such as inorganic zinc primer) is pre-coated on the base material surface, the gas released by the thermal decomposition of the primer further exacerbates the porosity tendency; 2) During fillet welding, the molten metal in the pool tends to flow downwards under gravity, and the welding... Slag tends to accumulate at corners. If slag removal is poor, it will not only affect the appearance of the weld but also increase the cost of subsequent cleaning processes. 3) Under high-speed welding conditions, the arc travels rapidly, requiring high arc stability and less spatter. Otherwise, uneven droplet transfer will lead to poor weld formation, resulting in defects such as undercut, weld beads, or abrupt transition with the base metal. 4) Flat fillet welds cool very quickly and are prone to hardening. Therefore, the weld metal is required to have excellent low-temperature impact toughness, plasticity, and extremely low diffusible hydrogen content to avoid cold brittle fracture and delayed cracking.

[0003] Currently, among the existing flux-cored welding wire products in China, while all-position welding wires have wide applicability, their anti-porosity performance is insufficient under high-speed fillet welding conditions; while some high-speed fillet welding-specific welding wires are not good in weld formation and low-temperature mechanical properties. Therefore, there is an urgent need to design a flux-cored welding wire specifically designed for the characteristics of high-speed fillet welding and flat welding processes, which can balance anti-porosity, slag removal, weld formation quality, and low-temperature mechanical properties at ultra-high welding speeds. Summary of the Invention

[0004] The purpose of this invention is to provide a flux-cored welding wire for high-speed flat welding and fillet welding, which can at least solve some of the defects existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A flux-cored welding wire for high-speed flat welding and fillet welding includes a carbon steel outer sheath and a flux core, wherein the flux core comprises the following components by mass percentage: barium fluoride 0.5-1%, rutile 10-20%, aluminum oxide 2-4%, magnesia 2-3%, ferrotitanium 1-2%, ferroboron 2-4%, ferroaluminum 1-2%, quartz 1-2%, bismuth oxide 0.1-0.3%, with the balance being Fe and unavoidable impurities.

[0007] Furthermore, the carbon steel outer sheath is made of low S and P carbon steel strip, the chemical composition and mass percentage of which are: C 0.02%~0.040%, Si 0.5%~0.6%, Mn 1.5%~1.7%, S≤0.010%, P≤0.010%, with the balance being iron.

[0008] Furthermore, the carbon steel outer sheath accounts for 80-82% of the total mass of the flux-cored welding wire.

[0009] Furthermore, the mass percentage of boron in the ferroboron is 1%.

[0010] Furthermore, the core comprises the following components by mass percentage: 1% barium fluoride, 20% rutile, 4% aluminum oxide, 3% magnesia, 2% ferrotitanium, 4% ferroboron, 2% ferroaluminum, 2% quartz, 0.3% bismuth oxide, with the balance being Fe and unavoidable impurities.

[0011] Furthermore, the core comprises the following components by mass percentage: 0.7% barium fluoride, 15% rutile, 3% aluminum oxide, 2.5% magnesia, 1.5% ferrotitanium, 3% ferroboron, 1.5% ferroaluminum, 1.5% quartz, 0.2% bismuth oxide, with the balance being Fe and unavoidable impurities.

[0012] Furthermore, the core comprises the following components by mass percentage: 0.5% barium fluoride, 10% rutile, 2% aluminum oxide, 2% magnesia, 1% ferrotitanium, 2% ferroboron, 1% ferroaluminum, 1% quartz, 0.1% bismuth oxide, with the balance being Fe and unavoidable impurities.

[0013] Furthermore, the flux-cored welding wire has an average KV2 impact energy of -20℃ ≥80J, an elongation of ≥26%, and a diffusible hydrogen content of <5.0mL / 100g.

[0014] In addition, the present invention also provides the application of the above-mentioned flux-cored welding wire, which is used for flat welding and / or fillet welding.

[0015] Furthermore, CO2 gas protection is used, and the flux-cored welding wire is used to weld fillet welds on a zinc-rich primer plate. The welding current and voltage are 320A and 34V, respectively, and the welding speed is 1000-1200mm / min.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The flux-cored welding wire provided by this invention has a weld metal KV2 average value of ≥80J at -20℃, a weld elongation of ≥26%, and a diffusible hydrogen content of <5.0mL / 100g as determined by mercury method. With CO2 gas protection, the welding arc is stable, the melting is uniform, the slag has good fluidity, and the weld formation is beautiful. The welding speed on zinc-rich primer plates can reach 1000-1200mm / min without porosity. Detailed Implementation

[0018] 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.

[0019] This invention provides a flux-cored welding wire for high-speed flat welding and fillet welding, comprising a carbon steel outer sheath and a flux core. The flux core comprises the following components by mass percentage: barium fluoride 0.5-1%, rutile 10-20%, aluminum oxide 2-4%, magnesia 2-3%, ferrotitanium 1-2%, ferroboron 2-4%, ferroaluminum 1-2%, quartz 1-2%, bismuth oxide 0.1-0.3%, with the balance being Fe and unavoidable impurities. Preferably, the ferroboron contains 1% boron by mass.

[0020] The design principles of each component of the herbal core in this invention are as follows:

[0021] Barium fluoride (BaF2) has the unique effect of reducing the surface tension and viscosity of molten slag. It can significantly improve the fluidity of molten slag during high-speed welding, allowing gas to rise and escape quickly. At the same time, its dehydrogenation function can effectively suppress the moisture and hydrogen sources generated by the decomposition of zinc-rich primer. When the barium fluoride content is below 0.5%, the effect is not obvious, and when it is above 1%, the slag system is too thin and easily lost. This invention controls the barium fluoride content to be 0.5% to 1%.

[0022] The main component of rutile, TiO2, is a major structural element of welding slag. The addition of TiO2 can stabilize the arc, reduce welding spatter, and improve slag coverage and removal. Under high-speed flat welding conditions, when the rutile content is below 10%, the slag coverage is incomplete, and the weld is prone to oxidation; when it is above 20%, the slag is too thick, making it difficult for gas to penetrate and escape during the extremely short molten pool period, thus increasing the risk of porosity. This invention controls the rutile content to 10-20%, ensuring slag integrity while maintaining permeability to adapt to the high-speed solidification rhythm.

[0023] The main component of quartz is SiO2, which is also the main component of slag. It can finely adjust the melting point and viscosity of slag, improve weld formation, and make the edge of the high-speed moving weld bead smoothly transition with the base material, avoiding step-like protrusions. The present invention controls the quartz content to be 1-2%.

[0024] Aluminum oxide (Al₂O₃) and magnesia (mainly MgO) are both high-melting-point oxides, together forming the high-temperature skeleton of the slag. In high-speed fillet welding, they work synergistically to raise the melting point of the slag to a suitable range, ensuring that the slag maintains sufficient viscosity at high temperatures to support the molten pool metal and prevent the molten pool from flowing down due to gravity, thus avoiding undercut or weld beads. This invention controls the aluminum oxide content to 2-4% and the magnesia content to 2-3%, avoiding excessive amounts that would result in rough finish.

[0025] Titanium iron and aluminum iron, as composite strong deoxidizers, quickly remove oxygen from the molten pool during high-speed welding, preventing CO pores caused by air entrapment or primer decomposition products. Titanium iron (content of 1-2%) is used in combination with 1% boron iron (content of 2-4%) to form TiN and BN dispersed particles during solidification, refining the grains and significantly improving the impact toughness at -20℃. When the boron iron content is less than 2%, the refining effect is insufficient, and when the content is more than 4%, the crack resistance is reduced.

[0026] Bismuth oxide (Bi2O3) is a key slag removal aid. A content of 0.1-0.3% can significantly improve the automatic peeling of slag in fillet welds and solve the problem of slag accumulation and difficulty in removing slag in flat fillet welds. The slag removal effect is not obvious below 0.1%, and it is detrimental to crack resistance above 0.3%.

[0027] The carbon steel outer skin uses carbon steel strip with ultra-low S and P content (both ≤0.010%). S and P are impurity elements that have a serious impact on the weld metal's resistance to hydrogen sulfide and reduce its low-temperature impact toughness. S forms sulfide inclusions with elements such as Fe, which can induce pitting corrosion and stress corrosion cracking. P has a strong segregation effect, causing unevenness in the weld metal, especially increasing cold brittleness. Therefore, the lower the S and P content, the better, as it reduces the damage of harmful impurities to low-temperature toughness from the source and ensures that the impact performance at -20℃ is stable and meets the design target.

[0028] Fe, or iron powder, can improve the state of the electric arc and adjust the melting point and viscosity of molten iron. The remainder is added.

[0029] As can be seen from the above analysis, the formulation system of this invention is specifically designed for high-speed flat welding and fillet welding conditions, constructing a synergistic metallurgical system of "barium fluoride dehydrogenation + titanium-silicon-aluminum-magnesium composite thin slag system + titanium-boron-aluminum composite deoxidation and grain refinement + trace bismuth oxide deslag removal":

[0030] Barium fluoride has a triple function of slag formation, adjusting slag fluidity, and dehydrogenation, reducing diffuse hydrogen at the source and making it suitable for high-speed welding, rapid solidification, and preventing cold cracking.

[0031] Rutile, quartz, alumina, and magnesia are combined to form a thin and breathable slag. Even at welding speeds of 1000-1200 mm / min, the slag can still ensure sufficient protection of the molten pool and smooth gas escape. No porosity is generated when welding on zinc-rich primer plates. Strict control of the upper limit of rutile prevents excessive slag from blocking gas channels, thus solving the core pain point of porosity in high-speed flat welding.

[0032] The combination of ferro-titanium and ferro-aluminum deoxidation, along with 1% ferroboron, refines the weld grains, significantly improving the low-temperature impact toughness of the weld at -20℃ under high-speed welding. This results in an average KV2 value of ≥80J and an elongation of ≥26% for the deposited metal at -20℃, meeting the low-temperature service requirements of load-bearing structures. The alloy composition ranges are precisely matched to the microstructure transformation law of rapid cooling of the high-speed molten pool.

[0033] Trace amounts of bismuth oxide improve automatic slag removal in high-speed continuous welding, making it suitable for uninterrupted flat welding operations in automated production lines.

[0034] Low S and P carbon steel strips avoid impurity segregation and sulfide inclusions, and combined with a low hydrogen flux core system, further improve the cold crack resistance and corrosion resistance of high-speed welds.

[0035] Specifically, the carbon steel outer sheath accounts for 80-82% of the total mass of the flux-cored welding wire.

[0036] Furthermore, the carbon steel outer sheath is made of low S and P carbon steel strip, the chemical composition and mass percentage of which are: C 0.02%~0.040%, Si 0.5%~0.6%, Mn 1.5%~1.7%, S≤0.010%, P≤0.010%, with the balance being iron.

[0037] The following specific embodiments illustrate the effectiveness of the flux-cored welding wire for high-speed flat welding and fillet welding according to the present invention. In the embodiments of the present invention, the flux-cored welding wire is prepared using conventional flux-cored welding wire preparation processes in the art, and the mass percentage of boron in the ferroboron is 1%.

[0038] Example 1:

[0039] This embodiment provides a flux-cored welding wire for high-speed flat welding and fillet welding, comprising a carbon steel outer sheath and a flux core, wherein the flux core accounts for 18% of the total mass of the flux-cored welding wire, and the flux core comprises the following components by mass percentage: barium fluoride 1%, rutile 20%, aluminum oxide 4%, magnesia 3%, ferrotitanium 2%, ferroboron 4%, ferroaluminum 2%, quartz 2%, bismuth oxide 0.3%, with the balance being Fe and unavoidable impurities.

[0040] The carbon steel outer skin is made of low S and P carbon steel strip. The chemical composition of the carbon steel strip is C: 0.040%, Si: 0.6%, Mn: 1.7%, S: 0.010%, P: 0.010%, with the balance being iron.

[0041] The chemical composition of the deposited metal of the flux-cored wire prepared in this embodiment was tested, and the results are shown in Table 1.

[0042] The mechanical properties of the flux-cored wire prepared in this embodiment were tested, and the results are shown in Table 2.

[0043] The diffusion hydrogen test (mercury method) of the flux-cored wire prepared in this embodiment is shown in Table 3.

[0044] Example 2:

[0045] This embodiment provides a flux-cored welding wire for high-speed flat welding and fillet welding, comprising a carbon steel outer sheath and a flux core, wherein the flux core accounts for 19% of the total mass of the flux-cored welding wire, and the flux core comprises the following components by mass percentage: barium fluoride 0.7%, rutile 15%, aluminum oxide 3%, magnesia 2.5%, ferrotitanium 1.5%, ferroboron 3%, ferroaluminum 1.5%, quartz 1.5%, bismuth oxide 0.2%, with the balance being Fe and unavoidable impurities.

[0046] The carbon steel outer skin is made of low S and P carbon steel strip. The chemical composition of the carbon steel strip is C: 0.03%, Si: 0.55%, Mn: 1.6%, S: 0.06%, P: 0.07%, with the balance being iron.

[0047] The chemical composition of the deposited metal of the flux-cored wire prepared in this embodiment was tested, and the results are shown in Table 1.

[0048] The mechanical properties of the flux-cored wire prepared in this embodiment were tested, and the results are shown in Table 2.

[0049] The diffusion hydrogen test (mercury method) of the flux-cored wire prepared in this embodiment is shown in Table 3.

[0050] Example 3:

[0051] This embodiment provides a flux-cored welding wire for high-speed flat welding and fillet welding, comprising a carbon steel outer sheath and a flux core, wherein the flux core accounts for 20% of the total mass of the flux-cored welding wire, and the flux core comprises the following components by mass percentage: barium fluoride 0.5%, rutile 10%, aluminum oxide 2%, magnesia 2%, ferrotitanium 1%, ferroboron 2%, ferroaluminum 1%, quartz 1%, bismuth oxide 0.1%, with the balance being Fe and unavoidable impurities.

[0052] The carbon steel outer skin is made of low S and P carbon steel strip. The chemical composition of the carbon steel strip is C: 0.02%, Si: 0.5%, Mn: 1.5%, S: 0.050%, P: 0.050%, with the balance being iron.

[0053] The chemical composition of the deposited metal of the flux-cored wire prepared in this embodiment was tested, and the results are shown in Table 1.

[0054] The mechanical properties of the flux-cored wire prepared in this embodiment were tested, and the results are shown in Table 2.

[0055] The diffusion hydrogen test (mercury method) of the flux-cored wire prepared in this embodiment is shown in Table 3.

[0056] Table 1: Chemical composition of flux-cored wire deposited metal (%)

[0057]

[0058] Table 2: Mechanical Properties of Flux-Cored Welding Wires

[0059]

[0060] Table 3: Test of diffusible hydrogen content in flux-cored wires

[0061]

[0062] The 1.4mm flux-cored welding wire prepared in Examples 1-3 was used to weld fillet welds on zinc-rich primer plates. The welding current was 320A, the welding voltage was 34V, and the welding speed was set to 1000-1200mm / min. After welding, the welds were subjected to macroscopic and fracture tests, and no porosity or defects were found.

[0063] 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-speed flat welding and fillet welding, comprising a carbon steel outer sheath and a flux core, characterized in that, The core comprises the following components by mass percentage: 0.5-1% barium fluoride, 10-20% rutile, 2-4% aluminum oxide, 2-3% magnesia, 1-2% ferrotitanium, 2-4% ferroboron, 1-2% ferroaluminum, 1-2% quartz, 0.1-0.3% bismuth oxide, with the balance being Fe and unavoidable impurities.

2. The flux-cored welding wire as described in claim 1, characterized in that, The carbon steel outer sheath is made of low S and P carbon steel strip. The chemical composition and mass percentage of the carbon steel strip are as follows: C 0.02%~0.040%, Si 0.5%~0.6%, Mn 1.5%~1.7%, S≤0.010%, P≤0.010%, and the balance is iron.

3. The flux-cored welding wire as described in claim 1, characterized in that, The carbon steel outer sheath accounts for 80-82% of the total mass of the flux-cored welding wire.

4. The flux-cored welding wire as described in claim 1, characterized in that, The mass percentage of boron in the ferroboron is 1%.

5. The flux-cored welding wire as described in claim 1, characterized in that, The core comprises the following components by mass percentage: 1% barium fluoride, 20% rutile, 4% aluminum oxide, 3% magnesia, 2% ferrotitanium, 4% ferroboron, 2% ferroaluminum, 2% quartz, 0.3% bismuth oxide, with the balance being Fe and unavoidable impurities.

6. The flux-cored welding wire as described in claim 1, characterized in that, The core comprises the following components by mass percentage: 0.7% barium fluoride, 15% rutile, 3% aluminum oxide, 2.5% magnesia, 1.5% ferrotitanium, 3% ferroboron, 1.5% ferroaluminum, 1.5% quartz, 0.2% bismuth oxide, with the balance being Fe and unavoidable impurities.

7. The flux-cored welding wire as described in claim 1, characterized in that, The core comprises the following components by mass percentage: 0.5% barium fluoride, 10% rutile, 2% aluminum oxide, 2% magnesia, 1% ferrotitanium, 2% ferroboron, 1% ferroaluminum, 1% quartz, 0.1% bismuth oxide, with the balance being Fe and unavoidable impurities.

8. The flux-cored welding wire according to any one of claims 1-7, characterized in that, The flux-cored welding wire has an average KV2 impact energy of -20℃ ≥80J, an elongation of ≥26%, and a diffusible hydrogen content of <5.0mL / 100g.

9. The application of the flux-cored welding wire as described in any one of claims 1-8, characterized in that, The flux-cored wire is used for flat welding and / or fillet welding.

10. The application as described in claim 9, characterized in that, Using CO2 gas protection, the flux-cored welding wire is used to weld fillet welds on a zinc-rich primer plate. The welding current and voltage are 320A and 34V, respectively, and the welding speed is 1000-1200mm / min.

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