High-strength and high-toughness weather-resistant bridge steel welding flux-cored wire and preparation method thereof

Abstract

The present application relates to a high-strength and high-toughness weathering bridge steel welding flux-cored wire for highlands and a preparation method thereof. Specifically, the flux-cored wire is prepared from a flux powder and a carbon steel sheath for wrapping the flux powder; the flux powder comprises rutile, zirconite, quartz, aluminum oxide, fluorite, sodium fluoride, magnesia, copper powder, nickel powder, nano nickel powder, manganese iron, titanium iron, electrolytic manganese, chromium iron, aluminum-magnesium alloy, silicon-calcium alloy, silicon-manganese alloy, and iron powder. The present application aims at the severe requirements for the comprehensive performance of weathering bridge steel welding in the complex service environment of highlands, and solves the problems of low mechanical properties of high-strength weathering bridge steel welding, especially poor low-temperature toughness and lower corrosion resistance than the base material. The welding flux-cored wire has stable mechanical properties of the deposited metal, excellent low-temperature impact performance, and excellent corrosion resistance, and is suitable for the welding manufacturing of weathering bridges under the service conditions of highlands, high coldness, and large temperature difference.

Description

Technical Field

[0001] This invention belongs to the technical field of welding materials and welding material manufacturing processes, specifically relating to a flux-cored welding wire for welding high-strength, tough, and weather-resistant bridge steel in complex high-altitude environments at 550MPa and its preparation method. Background Technology

[0002] High-performance bridge steels, such as weathering-resistant bridge steel and stainless steel composite plates, have broad application prospects in plateau regions. Currently, research and engineering applications of high-performance bridge steels for plateau environments are insufficient to meet the needs of transportation construction in my country's plateau regions. Breakthroughs are urgently needed in key technologies for the development, preparation, and application of high-performance bridge steel plates suitable for complex plateau environments.

[0003] Weathering steel, commonly used in bridge construction in complex high-altitude environments, is a low-alloy steel that falls between ordinary carbon steel and stainless steel. The Cr, Ni, and Cu alloying elements in weathering steel form a protective film on the steel matrix surface, reducing the conductivity of the rust layer and thus improving its resistance to atmospheric corrosion. Ni, as a stabilizing element, shifts the steel's self-corrosion potential in a positive direction, increasing its stability; the addition of Ni also improves its low-temperature impact toughness. Cr forms a dense oxide film on the steel surface, enhancing its passivation ability and slowing down rust growth. Cu is an alloying element that improves the corrosion resistance of steel.

[0004] Chinese Patent Application No. 202311060501.4 discloses a 550MPa grade bridge steel plate for complex high-altitude environments. The chemical composition of the steel plate, by weight percentage, is: C: 0.08-0.10%, Si: 0.25-0.35%, Mn: 1.35-1.50%, P≤0.015%, S≤0.005%, Nb: 0.045-0.055%, V: 0.045-0.055%, Ti: 0.010-0.020%, Cr: 0.50-0.60%, Ni: 0.35-0.45%, Cu: 0.35-0.45%, Mo: 0.15-0.25%, rare earth Ce: 0.0005-0.0020%, and Als: 0.20-0.025%.

[0005] Chinese Patent Application No. 202210552777.3 discloses a method for producing weather-resistant bridge steel with a yield strength greater than 550 MPa suitable for high-altitude environments, which is easy to form and requires no coating. The steel's chemical composition (mass percentage) is: C = 0.03–0.05, Si = 0.40–0.50, Mn = 1.00–1.10, Cr = 0.60–0.70, Ni = 0.50–0.60, Cu = 0.50–0.55, P = <0.010, S <0.001, Nb = 0.040–0.045, Ti = 0.02–0.03, Al = 0.010–0.02. 0, N 0.005~0.007, B≤0.0005, H≤0.0002, balance being Fe and unavoidable impurities; it is believed that the 10~40mm thick Q550Mpa grade weathering bridge steel produced by this invention has a composite structure of ferrite + lath bainite + a small amount of M / A components, yield strength 570~635Mpa, tensile strength 690~760Mpa, yield ratio 0.81~0.84, impact value at -40℃ 240~320J, impact value at -40℃ of welded joint heat-affected zone 120~180J, corrosion thinning over 100-year lifespan <1mm, cutting deformation <3mm.

[0006] Chinese Patent Application No. 201811494831.3 discloses a weathering bridge steel plate with a yield strength of 550MPa and its production method. Its chemical composition and mass percentage are as follows: C = 0.03%~0.07%, Mn = 1.35%~1.45%, S ≤ 0.005%, P = 0.012%~0.018%, Si = 0.25%~0.35%, Als = 0.020%~0.050%, Nb = 0.025%~0.034%, Ti = 0.010%~0.025%, Cr = 0.50%~0.70%, Ni = 0.35%~0.45%, Cu = 0.30%~0.45%, Mo = 0.10%~0.30%, with the balance being Fe and unavoidable impurities. The invented steel plate is believed to have excellent performance, good weldability, excellent low-temperature impact toughness, and strong weather resistance. Its production method is simple and does not require tempering (quenching + high-temperature tempering), resulting in low production costs. It is currently the weather-resistant bridge steel with the highest yield strength grade among bridge steel standards. The product has good weather resistance, with a weather resistance index I ≥ 6.5; excellent weldability, with a weld crack sensitivity index Pcm ≤ 0.24; excellent notched impact toughness, with a V-notch impact energy ≥ 200 J at -40℃; tensile strength ≥ 670 MPa, yield strength ≥ 550 MPa, and elongation A ≥ 16%.

[0007] Chinese Patent Application No. 202110856460.4 discloses a 550MPa grade weathering bridge steel, which, in addition to Fe and unavoidable impurities, contains the following chemical elements: C: 0.025-0.055%, Si: 0.50-1.00%, Mn: 1.45-1.65%, V: 0.025-0.045%, Mo: 0.20-0.40%, Ni: 0.40-0.60%, Cu: 0.20-0.40%, Cr: 0.25-0.45%, Sb: 0.20-0.50%, Ca: 0.0030-0.006%; the microstructure is a single bainitic structure. The invention also discloses a method for manufacturing the above-mentioned steel, which does not include a post-rolling heat treatment step, and includes the following steps: (1) desulfurization of molten iron, smelting in a converter, refining in an LF furnace and vacuum treatment in an RH furnace (2) continuous casting with protective pouring (3) billet heating (4) two-stage rolling: the rolling temperature is controlled at 1040~1180℃ in the first stage, and the reduction rate of each of the first three passes is ≥18%; the rolling temperature is controlled at 850~930℃ in the second stage, the rolling temperature is controlled at 820~860℃, the reduction rate of each of the first three passes is ≥16%, and the cumulative reduction rate of the last three passes is ≥30% (5) cooling: the cooling start temperature is 800~830℃, the cooling rate is 15~40℃ / s, and the reddening temperature is 300~500℃ (6) tempering.

[0008] Chinese Patent Application No. 202311060501.4 discloses a 550MPa grade bridge steel plate for complex high-altitude environments. The chemical composition of the steel plate, by weight percentage, is: C: 0.08-0.10%, Si: 0.25-0.35%, Mn: 1.35-1.50%, P≤0.015%, S≤0.005%, Nb: 0.045-0.055%, V: 0.045-0.055%, Ti: 0.010-0.020%, Cr: 0.50-0.60%, Ni: 0.35-0.45%, Cu: 0.35-0.45%, Mo: 0.15-0.25%, rare earth Ce: 0.0005-0.0020%, Als: 0.20-0.025%. The preparation method is also disclosed. It is believed that the invention obtains a multiphase composite structure of fine-grained ferrite, bainitic ferrite, and precipitates through composition and process design.

[0009] Chinese Patent Application No. 202111355787.X relates to a high-performance bridge steel with a yield strength of not less than 550 MPa, its preparation method, and its applications. The preparation method includes smelting, slow cooling, heating, controlled rolling and controlled cooling, and stacking cooling steps; the chemical composition of the cast billet by weight percentage conforms to the following: C: 0.08%–0.11%, Si: 0.10%–0.25%, Mn: 1.40%–1.50%, P≤0.015%, S≤0.003%, Als: 0.010%–0.040%, Cr: 0.50%–0.60%, Cu: 0.15%–0.20%, Ni: 0.30%–0.40%, Nb: 0.025%–0.040%, Ti: 0.010%–0.040%; the high-performance bridge steel prepared by this method can be used to manufacture structural components for unpainted buildings. It is believed that the invention uses a lower carbon content and microalloying elements to ensure mechanical properties, while also improving the weldability of the steel plate and ensuring its weather resistance. The resulting high-performance bridge steel plate has a lower yield strength ratio, carbon equivalent and welding sensitivity coefficient, and its yield strength can stably reach more than 550 MPa, and its impact energy at -60℃ can stably reach more than 200 J.

[0010] Chinese Patent Application No. 201510339460.1 discloses a TMCP+tempered 550MPa grade corrosion-resistant bridge steel and its production method, which is composed of the following chemical composition by weight percentage: C: 0.05~0.10%, Si: 0.05~0.20%, Mn: 0.95~1.65%, P≤0.030%, S≤0.005%, Cu≤0.80%, V: 0.040~0.10%, Nb: 0.020~0.040%, Al: 0.020~0.050%, W: 0.10~0.50%, Sn≤0.005%, Cev≤0.53%, with the balance being Fe and unavoidable impurities, wherein Cev=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15. The production method includes converter smelting, LF refining, vacuum refining, casting, heating, rolling, slow cooling, and heat treatment. It is believed that the mechanical properties of this invented steel fully meet the standard requirements for TMCP+ tempered 550MPa grade corrosion-resistant bridge steel with a considerable margin; furthermore, the content of added precious metals is low, resulting in lower production costs.

[0011] Chinese Patent Application No. 202110162143.2 discloses a high-toughness alkaline all-position flux-cored welding wire adaptable to high-altitude climates. The flux core comprises the following components by mass fraction: barium fluoride 10%-20%, barium carbonate 1%-4%, lithium fluoride 1%-4%, magnesia 3%-8%, zirconium oxide 3%-9%, iron tetroxide 8%-12%, electrolytic manganese 5%-12%, nickel powder 3%-6%, aluminum powder 6%-10%, high-carbon ferromanganese 5%-9%, rare earth fluorides 1%-3%, and the balance being iron powder; the sum of the mass fractions of all components is 100%. It is believed that this invention uses an alkaline all-position flux-cored welding wire protected by carbon dioxide gas, exhibiting excellent welding process, good all-position weldability, minimal spatter, and no porosity observed during welding at an altitude of 5200 meters. The X-ray flaw detection pass rate reaches over 95%, and it is adaptable to semi-automatic and fully automatic welding. The low-temperature impact toughness of the deposited metal is above 180J at -40℃ and above 150J at -50℃, exhibiting excellent resistance to cold cracking.

[0012] Chinese patent CN109175775B (201811238837.4) discloses a flux-cored welding wire for welding Q550NHQ weathering steel, wherein Ni: 0.12-0.65%; Cr: 0.30-1.25%; Cu: 0.20-0.55%. This flux-cored welding wire for Q550NH weathering steel is made by coating low-carbon cold-rolled steel strip with flux powder. The flux composition and dosage, by mass percentage, are: Ni 2.2%-3.0%, chromium nitride... The composition is as follows: iron 3.0%–4.0%, Cu 2.0%–3.0%, ferrosilicon 2.0%–4.0%, ferromanganese 3.0%–5.0%, ferroniobium 1.5%–3.0%, titanium dioxide 5.0%–8.0%, 80-mesh straw powder 5.0%–10.0%, with the balance being FHT100·25 reduced iron powder. The Ni% / Cr% ratio is controlled between 0.9 and 1.8. The flux core accounts for 15%–18% of the total mass of the flux-cored welding wire, and the wire diameter is 1.2–2.0 mm.

[0013] However, in the welding process of high-strength, toughness and weather-resistant bridge steel in complex plateau environments, problems such as insufficient weld strength, low and unstable low-temperature impact toughness, and insufficient corrosion resistance in some welds often occur. Those skilled in the art still expect to provide welding wires that can overcome these problems, such as providing flux-cored welding wires for welding high-strength, toughness and weather-resistant bridge steel in complex plateau environments with a 550MPa rating. Summary of the Invention

[0014] The purpose of this invention is to overcome the problems of insufficient weld strength, low and unstable low-temperature impact toughness, and insufficient corrosion resistance in some welds during the welding of high-strength, toughness and weather-resistant bridge steel in complex high-altitude environments. To this end, this invention provides a 550MPa grade flux-cored welding wire for welding high-strength, toughness and weather-resistant bridge steel in complex high-altitude environments, and also provides a method for preparing the 550MPa grade flux-cored welding wire for welding high-strength, toughness and weather-resistant bridge steel in complex high-altitude environments.

[0015] Therefore, in a first aspect of the present invention, a flux-cored welding wire for welding high-strength, tough, and weather-resistant bridge steel in complex high-altitude environments (550 MPa grade) is provided. This wire is prepared from flux-cored powder and a carbon steel outer sheath for encapsulating the flux-cored powder. The flux-cored powder, by mass percentage, is composed of the following components: rutile 29%–31%, zircon sand 3.2%–3.6%, quartz 2.0%–2.4%, alumina 3.2%–3.6%, fluorite 2.8%–3.2%, and sodium fluoride 2.0%–2%. 0.4%, magnesia 2.6%–3.0%, copper powder 1.6%–2.0%, nickel powder 3.8%–6.5%, nano nickel powder 1.3%–1.7%, ferromanganese 1.6%–2.0%, ferrotitanium 1.8%–2.4%, electrolytic manganese 1.6%–2.0%, ferrochrome 2.3%–2.7%, aluminum-magnesium alloy 3.2%–3.6%, silicon-calcium alloy 0.8%–1.2%, silicon-manganese alloy 7.8%–8.2%, potassium titanate 3.8%–4.2%, and iron powder up to 100%.

[0016] According to the first aspect of the present invention, the flux-cored wire has flux powder particles that can pass through a 60-80 mesh sieve.

[0017] According to the first aspect of the invention, the flux-cored wire has a flux powder filling rate of 14.0-18.0%, for example 14.0-17.0%, for example 14.0-16.0%.

[0018] According to the flux-cored welding wire of the first aspect of the present invention, the carbon steel outer sheath is HS1 carbon steel strip, wherein the impurity elements and their mass content are P≤0.010% and S≤0.006%.

[0019] According to the first aspect of the present invention, the flux-cored wire has a diameter of 0.5 to 3 mm, for example 1 to 2 mm, for example 1 to 1.5 mm, for example 1.1 to 1.3 mm, for example 1.2 mm.

[0020] According to the first aspect of the present invention, the chemical composition of the deposited metal obtained after welding is C: 0.02% to 0.06%, Si: 0.2% to 0.5%, Mn: 0.6% to 1.0%, Cr: 0.1% to 0.3%, Ni: 0.7% to 1.3%, Cu: 0.2% to 0.5%, P ≤ 0.02%, O: 0.02% to 0.05%, and the balance being iron and unavoidable impurities.

[0021] According to the first aspect of the invention, the chemical composition of the deposited metal obtained after welding is as follows: C: 0.04% to 0.06%, for example 0.05% to 0.06%; Si: 0.2% to 0.4%, for example 0.2% to 0.3%; Mn: 0.7% to 0.9%, for example 0.7% to 0.85%; Cr: 0.15% to 0.3%, for example 0.2% to 0.3%; Ni: 0.75% to 1.25%, for example 0.8% to 1.2%; Cu: 0.2% to 0.4%, for example 0.2% to 0.35%; P ≤ 0.015%, for example ≤ 0.012%; O: 0.02% to 0.045%, for example 0.02% to 0.04%; and the balance being iron and unavoidable impurities.

[0022] According to the first aspect of the present invention, the flux-cored welding wire is prepared by a method comprising the following steps:

[0023] (1) Bake rutile and zircon sand at high temperature and set aside;

[0024] (2) Bake quartz, aluminum oxide, fluorite, sodium fluoride, and magnesia at medium temperature for later use;

[0025] (3) Bake copper powder, nickel powder, nano nickel powder, ferromanganese, ferrotitanium, electrolytic manganese, ferrochrome, silicon-calcium alloy, and silicon-manganese alloy at low temperature, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain core powder.

[0026] (4) Roll the HS1 steel strip into a U-shape, add flux-cored powder into the U-shaped groove and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain the welding wire. Mechanically clean the surface of the welding wire to obtain the flux-cored welding wire.

[0027] According to the flux-cored wire of the first aspect of the present invention, in step (1), the parameters for high-temperature baking are: temperature of 800-1000℃, for example 850-950℃, and time of 3h-5h, for example 3.5-4.5h.

[0028] According to the flux-cored wire of the first aspect of the present invention, in step (2), the parameters for medium-temperature baking are: temperature of 300-500°C, for example 350-450°C, and time of 2-4h, for example 2.5-3.5h.

[0029] According to the flux-cored wire of the first aspect of the present invention, in step (3), the parameters for low-temperature baking are: temperature of 110-130°C, for example 115-125°C, and time of 4-6h, for example 4.5-5.5h.

[0030] According to the flux-cored wire of the first aspect of the present invention, in step (4), the filling rate of the flux-cored powder is 14.0 to 18.0%, for example 14.0 to 17.0%, for example 14.0 to 16.0%.

[0031] According to the flux-cored wire of the first aspect of the present invention, in step (4), the wire is continuously drawn and reduced in diameter until the wire diameter is 0.5-3 mm, for example 1-2 mm, for example 1-1.5 mm, for example 1.1-1.3 mm, for example 1.2 mm.

[0032] According to the flux-cored wire of the first aspect of the present invention, the nano-nickel powder is nickel powder with a particle size of 300-600 nm.

[0033] According to the flux-cored wire of the first aspect of the present invention, each of the various materials (except for nano-nickel powder) used to prepare the flux-cored powder is pre-crushed and sieved to prepare a powder with a particle size of 60 to 80 mesh.

[0034] Furthermore, in a second aspect of the present invention, a method for preparing the flux-cored welding wire according to any one of the first aspects of the present invention is provided, comprising the following steps:

[0035] (1) Bake rutile and zircon sand at high temperature and set aside;

[0036] (2) Bake quartz, aluminum oxide, fluorite, sodium fluoride, and magnesia at medium temperature for later use;

[0037] (3) Bake copper powder, nickel powder, nano nickel powder, ferromanganese, ferrotitanium, electrolytic manganese, ferrochrome, silicon-calcium alloy, and silicon-manganese alloy at low temperature, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain core powder.

[0038] (4) Roll the HS1 steel strip into a U-shape, add flux-cored powder into the U-shaped groove and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain the welding wire. Mechanically clean the surface of the welding wire to obtain the flux-cored welding wire.

[0039] According to the method of the second aspect of the present invention, in step (1), the parameters of high-temperature baking are: temperature of 800-1000℃, for example 850-950℃, and time of 3h-5h, for example 3.5-4.5h.

[0040] According to the method of the second aspect of the present invention, in step (2), the parameters of medium-temperature baking are: temperature of 300-500°C, for example 350-450°C, and time of 2-4h, for example 2.5-3.5h.

[0041] According to the method of the second aspect of the present invention, in step (3), the parameters of low-temperature baking are: temperature of 110-130°C, for example 115-125°C, and time of 4-6h, for example 4.5-5.5h.

[0042] According to the method of the second aspect of the present invention, in step (4), the filling rate of the core powder is 14.0 to 18.0%, for example 14.0 to 17.0%, for example 14.0 to 16.0%.

[0043] According to the method of the second aspect of the present invention, in step (4), the wire diameter is continuously drawn and reduced until the diameter of the welding wire is 0.5-3 mm, for example 1-2 mm, for example 1-1.5 mm, for example 1.1-1.3 mm, for example 1.2 mm.

[0044] According to the method of the second aspect of the present invention, each of the various materials for preparing the core powder is pre-crushed and sieved to prepare a powder with a particle size of 60 to 80 mesh.

[0045] According to the method of the second aspect of the present invention, the nano-nickel powder is nickel powder with a particle size of 300-600 nm.

[0046] According to the method of the second aspect of the present invention, each of the various materials (except for nano-nickel powder) used to prepare the core powder is pre-crushed and sieved to prepare a powder with a particle size of 60 to 80 mesh.

[0047] According to any aspect of the invention, the core powder is prepared by mixing the following components by mass percentage: rutile 30%, zircon sand 3.4%, quartz 2.2%, aluminum oxide 3.4%, fluorite 3.0%, sodium fluoride 2.2%, magnesia 2.8%, copper powder 1.7%, nickel powder 4.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, and silicon-calcium alloy. 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, iron powder to make up to 100%; for example, the filling rate of flux-cored wire is 15%; for example, the deposited metal after welding includes the following percentages of chemical composition and the balance iron and unavoidable impurities: C: 0.045, Si: 0.30, Mn: 0.80, Cr: 0.25, Ni: 0.83, Cu: 0.255, P: 0.010, O: 0.033.

[0048] According to any aspect of the invention, the core powder is prepared by mixing the following components by mass percentage: rutile 30%, zircon sand 3.4%, quartz 2.2%, aluminum oxide 3.4%, fluorite 3.0%, sodium fluoride 2.2%, magnesia 2.8%, copper powder 1.7%, nickel powder 5.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, and silicon-calcium alloy. 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, iron powder to make up to 100%; for example, the filling rate of flux-cored wire is 15%; for example, the deposited metal after welding includes the following percentages of chemical composition and the balance iron and unavoidable impurities: C: 0.046, Si: 0.29, Mn: 0.82, Cr: 0.26, Ni: 0.97, Cu: 0.253, P: 0.009, O: 0.028.

[0049] According to any aspect of the invention, the core powder is prepared by mixing the following components by mass percentage: rutile 30%, zircon sand 3.4%, quartz 2.2%, aluminum oxide 3.4%, fluorite 3.0%, sodium fluoride 2.2%, magnesia 2.8%, copper powder 1.6%, nickel powder 6.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, and silicon-calcium alloy. 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, iron powder to make up to 100%; for example, the filling rate of flux-cored wire is 15%; for example, the deposited metal after welding includes the following percentages of chemical composition and the balance iron and unavoidable impurities: C: 0.046, Si: 0.28, Mn: 0.78, Cr: 0.22, Ni: 1.13, Cu: 0.245, P: 0.010, O: 0.025.

[0050] According to any aspect of the invention, the core powder is prepared by mixing the following components by mass percentage: rutile 31%, zircon sand 3.2%, quartz 2.0%, aluminum oxide 3.6%, fluorite 2.8%, sodium fluoride 2.4%, magnesia 2.6%, copper powder 2.0%, nickel powder 4.0%, nano nickel powder 1.7%, ferromanganese 2.0%, ferrotitanium 2.4%, electrolytic manganese 2.0%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, and silicon-calcium alloy. 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, iron powder to make up to 100%; for example, the filling rate of flux-cored wire is 16%; for example, the deposited metal after welding includes the following percentages of chemical composition and the balance iron and unavoidable impurities: C: 0.043, Si: 0.25, Mn: 0.74, Cr: 0.24, Ni: 0.84, Cu: 0.30, P: 0.010, O: 0.031.

[0051] According to any aspect of the invention, the core powder is prepared by mixing the following components by mass percentage: rutile 29%, zircon sand 3.6%, quartz 2.4%, alumina 3.2%, fluorite 3.2%, sodium fluoride 2.0%, magnesia 3.0%, copper powder 1.9%, nickel powder 5.0%, nano nickel powder 1.6%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.6%, ferrochrome 2.7%, aluminum-magnesium alloy 3.2%, and silicon-calcium alloy. 0.8%, silicon-manganese alloy 8.2%, potassium titanate 3.8%, iron powder to make up to 100%; for example, the filling rate of flux-cored wire is 14%; for example, the deposited metal after welding includes the following percentages of chemical composition and the balance iron and unavoidable impurities: C: 0.048, Si: 0.24, Mn: 0.80, Cr: 0.24, Ni: 0.98, Cu: 0.290, P: 0.010, O: 0.029.

[0052] According to any aspect of the invention, the core powder is prepared by mixing the following components by mass percentage: rutile 30%, zircon sand 3.4%, quartz 2.2%, aluminum oxide 3.4%, fluorite 3.0%, sodium fluoride 2.2%, magnesia 2.8%, copper powder 1.9%, nickel powder 6.0%, nano nickel powder 1.3%, ferromanganese 1.6%, ferrotitanium 1.8%, electrolytic manganese 1.8%, ferrochrome 2.3%, aluminum-magnesium alloy 3.6%, and silicon-calcium alloy. 1.2%, silicon-manganese alloy 7.8%, potassium titanate 4.2%, iron powder to make up to 100%; for example, the filling rate of flux-cored wire is 18%; for example, the deposited metal after welding includes the following percentages of chemical composition and the balance iron and unavoidable impurities: C: 0.044, Si: 0.28, Mn: 0.78, Cr: 0.23, Ni: 1.12, Cu: 0.294, P: 0.010, O: 0.027.

[0053] Any embodiment of any aspect of the present invention can be combined with other embodiments, as long as they do not contradict each other. Furthermore, any technical feature in any embodiment of any aspect of the present invention can be applied to the same technical feature in other embodiments, as long as they do not contradict each other. The present invention will now be further described.

[0054] All references cited in this invention are incorporated herein by reference in their entirety, and in the event of any inconsistency between the meanings expressed in these references and those expressed herein, the meanings expressed herein shall prevail. Furthermore, the various terms and phrases used in this invention have their general meanings known to those skilled in the art; however, this invention still seeks to provide a more detailed explanation and interpretation of these terms and phrases, and in the event of any inconsistency between the mentioned terms and their known meanings and those expressed herein, the meanings expressed herein shall prevail.

[0055] The various terms and phrases used in this invention have their general meanings known to those skilled in the art. Nevertheless, this invention still intends to provide a more detailed description and explanation of these terms and phrases. In the event of any inconsistency between the terms and phrases mentioned and their known meanings, the meanings expressed in this invention shall prevail.

[0056] In this invention, the term "parts by weight" refers to the relative amounts of the components in the flux coating of the welding wire of this invention. "Parts by weight" can be an absolute weight (e.g., mg, g, or kg) or a weight percentage (e.g., weight % or wt%). Of course, when expressed as a weight percentage (e.g., weight % or wt%), a preferred embodiment is that the sum of the components is 100%.

[0057] In preparing the core powder according to this invention, various materials are pre-crushed and sieved to obtain powder with a particle size of 60-80 mesh. The particles are already very fine. From the perspective of removing moisture from the materials, in fact, all materials can have all kinds of moisture removed after baking at 115℃ for 4.5 hours, including adsorbed water and crystal water. The specific investigation method is to determine the loss on drying by means of the loss on drying method. After baking at 115℃ for 4.5 hours and at 1000℃ for 5 hours, the loss on drying measured under the two baking conditions is basically the same. For example, the loss on drying of the same batch of rutile after baking at 115℃ for 4.5 hours was 1.174% (5.143g before drying, 5.0832g after drying), and the loss on drying after baking at 1000℃ for 5 hours was 1.172% (5.0832g before drying, 5.143g after drying). 2317g (5.1704g after drying), the moisture content of the above batch of rutile was determined to be 1.177% by coulometric titration. The difference between the two drying loss methods was 0.002%, and the maximum difference between the three methods was 0.005%. The drying loss of other various crushed and sieved materials before being used to prepare core powder was measured by drying loss determination. The difference between drying loss at 115℃ for 4.5h and drying at 1000℃ for 5h was less than 0.011%. These results indicate that, from the perspective of removing moisture, all materials can be dried under the baking conditions of step (3). However, the inventors unexpectedly discovered that if rutile and zircon sand are pre-baked at a high temperature of about 900℃, and quartz and the other five materials are pre-baked at a medium temperature of about 400℃, the resulting welding wire has excellent low-temperature impact energy at -40℃; however, if the above two materials are not treated at high temperature, the -40℃ impact energy of the resulting weld metal is significantly worse.Specifically, in an example called Supplementary Example a, the formulations, preparation methods, and welding wire testing methods of Examples 1 to 6 were used respectively, except that step (1) was not performed, and rutile and zircon sand were treated together with the materials in step (2) to obtain 6 types of welding wires for welding. The impact energy of the deposited metal at -40°C was measured to be in the range of 61 to 63 KV² / J. For example, when referring to Example 1, the impact energy of the deposited metal at -40°C was measured to be 62.7 KV² / J. In an example called Supplementary Example b, the formulations, preparation methods, and welding wire testing methods of Examples 1 to 6 were used respectively, except that step (1) was not performed, and rutile and zircon sand were treated together with the materials in step (3) to obtain 6 types of welding wires for welding. The impact energy of the deposited metal at -40°C was measured to be in the range of 61 to 63 KV² / J. The impact energy of the weld metal at -40°C is in the range of 53 to 56 KV² / J. For example, when referring to Example 1, the impact energy of the weld metal at -40°C is measured to be 55.4 KV² / J. In an example called Supplementary Example c, the formulations and preparation methods of Examples 1 to 6 and the welding wire testing methods are used respectively. The only difference is that the rutile in step (1) is disposed of together with the materials in step (3), while the other operations remain unchanged. Six types of welding wires are obtained for welding, and the impact energy of the weld metal at -40°C is measured to be in the range of 58 to 60 KV² / J. For example, when referring to Example 1, the impact energy of the weld metal at -40°C is measured to be 59.8 KV² / J. In an example called Supplementary Example d, the formulations and preparation methods of Examples 1 to 6 and the welding wire testing methods are used respectively. The only difference in the wire testing method is that the zircon sand in step (1) is treated together with the materials in step (3), while the rest of the operation remains the same, resulting in 6 types of welding wires for welding. The impact energy of the weld metal at -40°C is measured to be in the range of 65 to 67 KV2 / J. For example, when referring to Example 1, the impact energy of the weld metal at -40°C is measured to be 65.3 KV2 / J. In an example called Supplementary Example e, the formulation and preparation method and the wire testing method of Examples 1 to 6 are referred to respectively. The only difference is that steps (1) to (3) are combined and the mixed powder is baked at the corresponding temperature and time in step (1) of each example, while the rest of the operation remains the same, resulting in 6 types of welding wires for welding. The impact energy of the weld metal at -40°C is measured to be in the range of 80 to 84 KV2 / J. Within the range, for example, referring to Example 1, the impact energy of the weld metal at -40°C was measured to be 81.6 KV² / J. This result indicates that the impact energy effect of all materials being treated at high temperature is basically no different from that of Examples 1 to 6, but it will significantly increase production energy consumption. In an example called Supplementary Example f, the formulation and preparation method and the welding wire testing method of Examples 1 to 6 were respectively referred to. The only difference was that steps (1) to (3) were combined to bake the mixed powder at the corresponding temperature and time of step (3) of each example, while the other operations remained unchanged, resulting in 6 types of welding wires for welding. The impact energy of the weld metal at -40°C was measured to be in the range of 50 to 53 KV² / J. For example, referring to Example 1, the impact energy of the weld metal at -40°C was measured to be 52.2 KV² / J.As can be seen from the results of the above supplementary embodiments, welding wires prepared by baking different materials under different conditions have significantly different properties. In particular, the welding wires prepared by high-temperature baking of rutile and zircon sand alone have significantly better performance than those prepared by other conditions. This discovery was completely unforeseen by the prior art. In addition, it has been found in this invention that using an appropriate amount of nano-sized nickel powder can significantly reduce the O content and diffusible hydrogen [H] content in the deposited metal. Specifically, in an example called Supplementary Example g, the formulations, preparation methods, and welding wire testing methods of Examples 1 to 6 were used respectively, except that all the nano-nickel powder used was replaced with an equal mass of 60-80 mesh ordinary nickel powder. Six types of welding wires were obtained and welded. The O content of the deposited metal was measured to be in the range of 0.084-0.098%, and the diffusible hydrogen [H] content was measured to be 9.3-9.7 cm. 3 Within a 100g range, for example, referring to Example 1, the O content of the deposited metal was measured to be 0.091% and the diffusible hydrogen [H] content was 9.54 cm³. 3 / 100g; Specifically, in an example called Supplementary Example h, the formulations, preparation methods, and welding wire testing methods of Examples 1-6 were used respectively, except that half of the nano-nickel powder used was replaced with an equal mass of 60-80 mesh ordinary nickel powder, while the other half was still made of nano-nickel powder. Six types of welding wires were obtained and welded. The O content of the deposited metal was measured to be in the range of 0.056-0.067%, and the diffusible hydrogen [H] content was in the range of 7.1-7.6 cm. 3 Within a 100g range, for example, referring to Example 1, the O content of the deposited metal was measured to be 0.062% and the diffusible hydrogen [H] content was 7.46 cm³. 3 / 100g. Given that the O and [H] contents in Table 1 are already very satisfactory results in the field and that the cost of nano-nickel powder is significantly higher than that of ordinary nickel powder, it is beneficial to use a portion of nano-nickel powder.

[0058] In summary, through performance comparison with some existing flux-cored welding wires, it has been found that the flux-cored welding wire obtained by the present invention exhibits one or more of the following advantages:

[0059] 1) The flux-cored welding wire for welding high-strength, tough, and weather-resistant bridge steel in complex high-altitude environments of the present invention uses the optimal alloy element ratio and high-quality welding raw materials and auxiliary materials to ensure that the chemical composition and mechanical properties of the deposited metal meet the manufacturing process requirements of high-strength and tough bridges in complex high-altitude environments.

[0060] 2) The flux-cored welding wire for high-strength, tough, and weather-resistant bridge steel welding in complex high-altitude environments of the present invention adds the optimal proportion of nickel powder to the flux powder and selects raw and auxiliary materials with ultra-low impurity content. This improves the low-temperature impact toughness of the weld metal while ensuring the stability of the performance. The impact energy at -40℃ is increased from 50J of conventional flux-cored welding wire to more than 70J.

[0061] 3) 100% CO2 gas protection is used to protect the weld pool and droplet transfer, ensuring excellent weldability during the welding process;

[0062] 4) The flux-cored welding wire for welding high-strength, tough, and weather-resistant bridge steel in complex high-altitude environments of the present invention has an atmospheric corrosion resistance index I of ≥6.5 after welding, ensuring that its weld has excellent atmospheric corrosion resistance.

[0063] 5) The potassium titanate contained in the flux-cored welding wire for high-strength, tough, and weather-resistant bridge steel welding in the complex environment of 550MPa plateau of the present invention plays a role in stabilizing the arc and optimizing the droplet morphology, thereby improving the welding process performance and welding transition stability, and serving as a basic guarantee for improving weld performance.

[0064] 6) The flux-cored welding wire for high-strength, tough, and weather-resistant bridge steel welding in complex high-altitude environments of the present invention contains a specific amount of nano-grade nickel powder. After physical mixing, it can be well combined with other flux-cored powders, and the O content in the weld metal after welding is reduced, thereby improving the weld strength, especially the stability of low-temperature impact performance, and ensuring the overall performance of the weld.

[0065] 7) The flux-cored welding wire for high-strength, tough, and weather-resistant bridge steel welding in the complex environment of 550MPa plateau of the present invention contains a specific amount of nano-grade nickel powder. H can be completely dissolved in Ni element to form unstable hydrides. During the welding crystallization process, the hydrogen absorbed by Ni liquid metal can be smoothly released, which can reduce the content of diffusible hydrogen [H] in the weld metal, reduce the probability of hydrogen-induced cracking in the weld, and ensure the stability of the mechanical properties of the weld metal in the harsh plateau environment.

[0066] This invention develops welding materials suitable for welding 550MPa grade high-strength, high-toughness, and weather-resistant bridge steel. Due to the unique and complex welding conditions at high altitudes, flux-cored welding wire with superior welding processability, minimal spatter, and aesthetically pleasing weld formation was selected to adapt to the complex welding conditions at high altitudes and improve welding efficiency. The welding materials developed in this invention for welding high-strength, high-toughness, and weather-resistant bridge steel in complex high-altitude environments overcome the challenge of stabilizing weld quality and are of great significance for advancing special bridge projects in high-altitude environments.

[0067] In summary, the flux-cored welding wire obtained by the present invention has excellent technical effects as described in the context of this invention. Detailed Implementation

[0068] The invention can be further described through the following embodiments; however, the scope of the invention is not limited to the following embodiments. Those skilled in the art will understand that various changes and modifications can be made to the invention without departing from its spirit and scope. The materials and methods used in the experiments are described generally and / or specifically. Although many materials and methods of operation used to achieve the objectives of the invention are well known in the art, the invention is still described in as much detail as possible herein.

[0069] In the following examples, unless otherwise specified, all values ​​representing the chemical composition of the welding wire or the deposited metal are percentages. In the following examples, unless otherwise specified, the various materials used to prepare the core powder (except for nano-nickel powder) are each pre-crushed and sieved to a particle size of 60-80 mesh, wherein the nano-nickel powder is nickel powder with a particle size of 300-600 nm.

[0070] Example 1: Preparation of flux-cored welding wire for high-strength, tough, and weather-resistant bridge steel welding under complex high-altitude environments (550 MPa)

[0071] 1. The steel strip used to prepare the flux-cored welding wire in this embodiment is: HS1 carbon steel strip, 0.8 mm thick and 12 mm wide, with P ≤ 0.010% and S ≤ 0.006% as impurity elements.

[0072] 2. Composition of the core powder (by mass percentage):

[0073] Rutile 30%, Zircon sand 3.4%,

[0074] Quartz 2.2%, Alumina 3.4%, Fluorite 3.0%, Sodium fluoride 2.2%, Magnesia 2.8%,

[0075] Copper powder 1.7%, nickel powder 4.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, silicon-calcium alloy 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, and iron powder to bring the total to 100%.

[0076] 3. Filling scheme: The filling rate of flux-cored wire is 15%.

[0077] 4. Preparation steps:

[0078] (1) Mix rutile and zircon sand and bake at 900℃ for 4 hours for later use;

[0079] (2) Mix quartz, aluminum oxide, fluorite, sodium fluoride and magnesia and bake at 400℃ for 3 hours for later use;

[0080] (3) After mixing the remaining materials, bake them at 120°C for 5 hours, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain the core powder;

[0081] (4) Roll the steel strip into a U-shape, add flux-cored powder into the U-shaped groove according to the specified filling rate and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain a welding wire with a diameter of 1.2 mm. Mechanically clean the surface of the welding wire to obtain a flux-cored welding wire.

[0082] 5. Performance evaluation of flux-cored welding wire:

[0083] The flux-cored welding wire of this embodiment was used to weld high-strength, high-toughness, and weather-resistant bridge steel in a complex high-altitude environment (550MPa grade) for wire and welding performance testing. The welding process parameters were: 100% CO2 gas shielded welding, DC reverse polarity, welding current I = 210A, welding voltage = 24V, gas flow rate 20L / min, welding speed 250mm / min, and interpass temperature less than 150℃. Results:

[0084] The resulting weld has an aesthetically pleasing shape and excellent weldability.

[0085] The deposited metal after welding wire application includes the following percentages of chemical composition and the balance of iron and unavoidable impurities: C: 0.045, Si: 0.30, Mn: 0.80, Cr: 0.25, Ni: 0.83, Cu: 0.255, P: 0.010, O: 0.033;

[0086] Diffusible hydrogen content [H]: 5.03 cm 3 / 100g;

[0087] The weld metal exhibits excellent mechanical properties, good and stable low-temperature impact resistance, and meets the atmospheric corrosion resistance index.

[0088] Example 2:

[0089] 1. The steel strip used to prepare the flux-cored welding wire in this embodiment is: HS1 carbon steel strip, 0.8 mm thick and 12 mm wide, with P ≤ 0.010% and S ≤ 0.006% as impurity elements.

[0090] 2. Composition of the core powder (by mass percentage):

[0091] Rutile 30%, Zircon sand 3.4%,

[0092] Quartz 2.2%, Alumina 3.4%, Fluorite 3.0%, Sodium fluoride 2.2%, Magnesia 2.8%,

[0093] Copper powder 1.7%, nickel powder 5.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, silicon-calcium alloy 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, and iron powder to bring the total to 100%.

[0094] 3. Filling scheme: The filling rate of flux-cored wire is 15%.

[0095] 4. Preparation steps:

[0096] (1) Mix rutile and zircon sand and bake at 900℃ for 4 hours for later use;

[0097] (2) Mix quartz, aluminum oxide, fluorite, sodium fluoride and magnesia and bake at 400℃ for 3 hours for later use;

[0098] (3) After mixing the remaining materials, bake them at 120°C for 5 hours, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain the core powder;

[0099] (4) Roll the steel strip into a U-shape, add flux-cored powder into the U-shaped groove according to the specified filling rate and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain a welding wire with a diameter of 1.2 mm. Mechanically clean the surface of the welding wire to obtain a flux-cored welding wire.

[0100] 5. Performance evaluation of flux-cored welding wire:

[0101] The flux-cored welding wire of this embodiment was used to weld high-strength, high-toughness, and weather-resistant bridge steel in a complex high-altitude environment (550MPa grade) for wire and welding performance testing. The welding process parameters were: 100% CO2 gas shielded welding, DC reverse polarity, welding current I = 210A, welding voltage = 24V, gas flow rate 20L / min, welding speed 250mm / min, and interpass temperature less than 150℃. Results:

[0102] The resulting weld has an aesthetically pleasing shape and excellent weldability.

[0103] The deposited metal after welding wire application includes the following percentages of chemical composition and the balance of iron and unavoidable impurities: C: 0.046, Si: 0.29, Mn: 0.82, Cr: 0.26, Ni: 0.97, Cu: 0.253, P: 0.009, O: 0.028;

[0104] Diffusible hydrogen content [H]: 4.96 cm 3 / 100g;

[0105] The weld metal exhibits excellent mechanical properties, good and stable low-temperature impact resistance, and meets the atmospheric corrosion resistance index.

[0106] Example 3:

[0107] 1. The steel strip used to prepare the flux-cored welding wire in this embodiment is: HS1 carbon steel strip, 0.8 mm thick and 12 mm wide, with P ≤ 0.010% and S ≤ 0.006% as impurity elements.

[0108] 2. Composition of the core powder (by mass percentage):

[0109] Rutile 30%, Zircon sand 3.4%,

[0110] Quartz 2.2%, Alumina 3.4%, Fluorite 3.0%, Sodium fluoride 2.2%, Magnesia 2.8%,

[0111] Copper powder 1.6%, nickel powder 6.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, silicon-calcium alloy 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, and iron powder to bring the total to 100%.

[0112] 3. Filling scheme: The filling rate of flux-cored wire is 15%.

[0113] 4. Preparation steps:

[0114] (1) Mix rutile and zircon sand and bake at 900℃ for 4 hours for later use;

[0115] (2) Mix quartz, aluminum oxide, fluorite, sodium fluoride and magnesia and bake at 400℃ for 3 hours for later use;

[0116] (3) After mixing the remaining materials, bake them at 120°C for 5 hours, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain the core powder;

[0117] (4) Roll the steel strip into a U-shape, add flux-cored powder into the U-shaped groove according to the specified filling rate and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain a welding wire with a diameter of 1.2 mm. Mechanically clean the surface of the welding wire to obtain a flux-cored welding wire.

[0118] 5. Performance evaluation of flux-cored welding wire:

[0119] The flux-cored welding wire of this embodiment was used to weld high-strength, high-toughness, and weather-resistant bridge steel in a complex high-altitude environment (550MPa grade) for wire and welding performance testing. The welding process parameters were: 100% CO2 gas shielded welding, DC reverse polarity, welding current I = 210A, welding voltage = 24V, gas flow rate 20L / min, welding speed 250mm / min, and interpass temperature less than 150℃. Results:

[0120] The resulting weld has an aesthetically pleasing shape and excellent weldability.

[0121] The deposited metal after welding wire application includes the following percentages of chemical composition and the balance of iron and unavoidable impurities: C: 0.046, Si: 0.28, Mn: 0.78, Cr: 0.22, Ni: 1.13, Cu: 0.245, P: 0.010, O: 0.025;

[0122] Diffusible hydrogen content [H]: 4.78 cm 3 / 100g;

[0123] The weld metal exhibits excellent mechanical properties, good and stable low-temperature impact resistance, and meets the atmospheric corrosion resistance index.

[0124] Example 4:

[0125] 1. The steel strip used to prepare the flux-cored welding wire in this embodiment is: HS1 carbon steel strip, 0.8 mm thick and 12 mm wide, with P ≤ 0.010% and S ≤ 0.006% as impurity elements.

[0126] 2. Composition of the core powder (by mass percentage):

[0127] Rutile 31%, Zircon sand 3.2%,

[0128] Quartz 2.0%, Alumina 3.6%, Fluorite 2.8%, Sodium fluoride 2.4%, Magnesia 2.6%,

[0129] Copper powder 2.0%, nickel powder 4.0%, nano nickel powder 1.7%, ferromanganese 2.0%, ferrotitanium 2.4%, electrolytic manganese 2.0%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, silicon-calcium alloy 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, and iron powder to bring the total to 100%.

[0130] 3. Filling scheme: The filling rate of flux-cored wire is 16%.

[0131] 4. Preparation steps:

[0132] (1) Mix rutile and zircon sand and bake at 950℃ for 3.5h for later use;

[0133] (2) Mix quartz, aluminum oxide, fluorite, sodium fluoride and magnesia and bake at 350℃ for 3.5 hours for later use;

[0134] (3) After mixing the remaining materials, bake them at 125°C for 4.5 hours, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain the core powder.

[0135] (4) Roll the steel strip into a U-shape, add flux-cored powder into the U-shaped groove according to the specified filling rate and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain a welding wire with a diameter of 1.2 mm. Mechanically clean the surface of the welding wire to obtain a flux-cored welding wire.

[0136] 5. Performance evaluation of flux-cored welding wire:

[0137] The flux-cored welding wire of this embodiment was used to weld high-strength, high-toughness, and weather-resistant bridge steel in a complex high-altitude environment (550MPa grade) for wire and welding performance testing. The welding process parameters were: 100% CO2 gas shielded welding, DC reverse polarity, welding current I = 210A, welding voltage = 24V, gas flow rate 20L / min, welding speed 250mm / min, and interpass temperature less than 150℃. Results:

[0138] The resulting weld has an aesthetically pleasing shape and excellent weldability.

[0139] The deposited metal after welding wire application includes the following percentages of chemical composition and the balance of iron and unavoidable impurities: C: 0.043, Si: 0.25, Mn: 0.74, Cr: 0.24, Ni: 0.84, Cu: 0.30, P: 0.010, O: 0.031;

[0140] Diffusible hydrogen content [H]: 5.08 cm 3 / 100g;

[0141] The weld metal exhibits excellent mechanical properties, good and stable low-temperature impact resistance, and meets the atmospheric corrosion resistance index.

[0142] Example 5:

[0143] 1. The steel strip used to prepare the flux-cored welding wire in this embodiment is: HS1 carbon steel strip, 0.8 mm thick and 12 mm wide, with P ≤ 0.010% and S ≤ 0.006% as impurity elements.

[0144] 2. Composition of the core powder (by mass percentage):

[0145] Rutile 29%, Zircon sand 3.6%,

[0146] Quartz 2.4%, Alumina 3.2%, Fluorite 3.2%, Sodium fluoride 2.0%, Magnesia 3.0%,

[0147] Copper powder 1.9%, nickel powder 5.0%, nano nickel powder 1.6%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.6%, ferrochrome 2.7%, aluminum-magnesium alloy 3.2%, silicon-calcium alloy 0.8%, silicon-manganese alloy 8.2%, potassium titanate 3.8%, and iron powder to bring the total to 100%.

[0148] 3. Filling scheme: The filling rate of flux-cored wire is 14%.

[0149] 4. Preparation steps:

[0150] (1) Mix rutile and zircon sand and bake at 850℃ for 4.5h for later use;

[0151] (2) Mix quartz, aluminum oxide, fluorite, sodium fluoride and magnesia and bake at 450℃ for 2.5 hours for later use;

[0152] (3) After mixing the remaining materials, bake them at 115°C for 5.5 hours, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain the core powder.

[0153] (4) Roll the steel strip into a U-shape, add flux-cored powder into the U-shaped groove according to the specified filling rate and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain a welding wire with a diameter of 1.3 mm. Mechanically clean the surface of the welding wire to obtain a flux-cored welding wire.

[0154] 5. Performance evaluation of flux-cored welding wire:

[0155] The flux-cored welding wire of this embodiment was used to weld high-strength, high-toughness, and weather-resistant bridge steel in a complex high-altitude environment (550MPa grade) for wire and welding performance testing. The welding process parameters were: 100% CO2 gas shielded welding, DC reverse polarity, welding current I = 210A, welding voltage = 24V, gas flow rate 20L / min, welding speed 250mm / min, and interpass temperature less than 150℃. Results:

[0156] The resulting weld has an aesthetically pleasing shape and excellent weldability.

[0157] The deposited metal after welding wire application includes the following percentages of chemical composition and the balance of iron and unavoidable impurities: C: 0.048, Si: 0.24, Mn: 0.80, Cr: 0.24, Ni: 0.98, Cu: 0.290, P: 0.010, O: 0.029;

[0158] Diffusible hydrogen content [H]: 4.84 cm 3 / 100g;

[0159] The weld metal exhibits excellent mechanical properties, good and stable low-temperature impact resistance, and meets the atmospheric corrosion resistance index.

[0160] Example 6:

[0161] 1. The steel strip used to prepare the flux-cored welding wire in this embodiment is: HS1 carbon steel strip, 0.8 mm thick and 12 mm wide, with P ≤ 0.010% and S ≤ 0.006% as impurity elements.

[0162] 2. Composition of the core powder (by mass percentage):

[0163] Rutile 30%, Zircon sand 3.4%,

[0164] Quartz 2.2%, Alumina 3.4%, Fluorite 3.0%, Sodium fluoride 2.2%, Magnesia 2.8%,

[0165] Copper powder 1.9%, nickel powder 6.0%, nano nickel powder 1.3%, ferromanganese 1.6%, ferrotitanium 1.8%, electrolytic manganese 1.8%, ferrochrome 2.3%, aluminum-magnesium alloy 3.6%, silicon-calcium alloy 1.2%, silicon-manganese alloy 7.8%, potassium titanate 4.2%, and iron powder to make up to 100%.

[0166] 3. Filling scheme: The filling rate of flux-cored wire is 18%.

[0167] 4. Preparation steps:

[0168] (1) Mix rutile and zircon sand and bake at 900℃ for 4 hours for later use;

[0169] (2) Mix quartz, aluminum oxide, fluorite, sodium fluoride and magnesia and bake at 400℃ for 3 hours for later use;

[0170] (3) After mixing the remaining materials, bake them at 120°C for 5 hours, and then mix them evenly with the mineral powder baked in steps (1) and (2) to obtain the core powder;

[0171] (4) Roll the steel strip into a U-shape, add flux-cored powder into the U-shaped groove according to the specified filling rate and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain a welding wire with a diameter of 1.1 mm. Mechanically clean the surface of the welding wire to obtain a flux-cored welding wire.

[0172] 5. Performance evaluation of flux-cored welding wire:

[0173] The flux-cored welding wire of this embodiment was used to weld high-strength, high-toughness, and weather-resistant bridge steel in a complex high-altitude environment (550MPa grade) for wire and welding performance testing. The welding process parameters were: 100% CO2 gas shielded welding, DC reverse polarity, welding current I = 210A, welding voltage = 24V, gas flow rate 20L / min, welding speed 250mm / min, and interpass temperature less than 150℃. Results:

[0174] The resulting weld has an aesthetically pleasing shape and excellent weldability.

[0175] The deposited metal after welding wire application includes the following percentages of chemical composition and the balance of iron and unavoidable impurities: C: 0.044, Si: 0.28, Mn: 0.78, Cr: 0.23, Ni: 1.12, Cu: 0.294, P: 0.010, O: 0.027;

[0176] Diffusible hydrogen content [H]: 4.66 cm 3 / 100g;

[0177] The weld metal exhibits excellent mechanical properties, good and stable low-temperature impact resistance, and meets the atmospheric corrosion resistance index.

[0178] In this invention, the atmospheric corrosion resistance value I can be calculated using the following formula: I = 26.01 (% Cu) + 3.88 (% Ni) + 1.20 (% Cr) + 1.49 (% Si) + 17.28 (% P) - 7.29 (% Cu)(% Ni) - 9.1 (% Ni)(% P) - 33.39 (% Cu) 2 .

[0179] Welding tests were conducted on the welding wires of Examples 1 to 6. The results of the weld metal composition are summarized in Table 1, and the results of the weld metal tensile properties and low-temperature impact properties are summarized in Table 2. The measured values ​​in the table are the average of 5 results.

[0180] Table 1: Chemical composition of deposited metal (mass fraction / wt%)

[0181] Example Si (%) Cr(％) Ni (%) Cu (%) P(％) C(％) Mn(%) O(％) <![CDATA[[H] / (cm 3 / 100g)]]> standard 0.2-0.5 0.1-0.3 0.7-1.3 0.2-0.5 ≤0.02 0.02-0.06 0.6-1.0 -- -- 1 0.30 0.25 0.83 0.255 0.010 0.045 0.80 0.033 5.03 2 0.29 0.26 0.97 0.253 0.009 0.046 0.82 0.028 4.96 3 0.28 0.22 1.13 0.245 0.010 0.046 0.78 0.025 4.78 4 0.25 0.24 0.84 0.300 0.010 0.043 0.74 0.031 5.08 5 0.24 0.24 0.98 0.290 0.010 0.048 0.80 0.029 4.84 6 0.28 0.23 1.12 0.294 0.010 0.044 0.78 0.027 4.66

[0182] Table 2: Mechanical and Corrosion Resistance Properties of Deposited Metal

[0183]

[0184]

[0185] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A flux-cored wire prepared from a flux powder and a carbon steel sheath for wrapping the flux powder; the flux powder is prepared by mixing the following ingredients in mass percentage: 29-31% of rutile, 3.2-3.6% of zirconite, 2.0-2.4% of quartz, 3.2-3.6% of aluminum oxide, 2.8-3.2% of fluorite, 2.0-2.4% of sodium fluoride, 2.6-3.0% of magnesia, 1.6-2.0% of copper powder, 3.8-6.5% of nickel powder, 1.3-1.7% of nano nickel powder, 1.6-2.0% of manganese iron, 1.8-2.4% of titanium iron, 1.6-2.0% of electrolytic manganese, 2.3-2.7% of chromium iron, 3.2-3.6% of aluminum-magnesium alloy, 0.8-1.2% of silicon-calcium alloy, 7.8-8.2% of silicon-manganese alloy, 3.8-4.2% of potassium silicate, and iron powder is added to 100%.

2. The flux-cored wire according to claim 1, wherein the particle size of the flux powder is 60-80 mesh; the nano nickel powder is a nickel powder with a particle size of 300-600 nm; each of the materials for preparing the flux powder, except the nano nickel powder, is previously crushed and sieved to a powder with a particle size of 60-80 mesh; and the flux-cored wire is a 550 MPa grade high-strength and high-toughness weather-resistant bridge steel welding flux-cored wire for use in high-altitude complex environments.

3. The flux cored wire of claim 1, wherein: The filling rate of the flux powder is 14.0-18.0%; the carbon steel sheath is an HS1 carbon steel strip, wherein the impurity elements and their mass percentages are P≤0.010% and S≤0.006%; and the diameter of the flux-cored wire is 0.5-3 mm.

4. The flux-cored wire according to claim 1, wherein the chemical composition of the deposited metal obtained after welding is C: 0.02-0.06%, Si: 0.2-0.5%, Mn: 0.6-1.0%, Cr: 0.1-0.3%, Ni: 0.7-1.3%, Cu: 0.2-0.5%, P≤0.02%, O: 0.02-0.05%, the balance of iron and inevitable impurities.

5. The flux-cored wire according to claim 1, wherein the chemical composition of the deposited metal obtained after welding is C: 0.04-0.06%, Si: 0.2-0.4%, Mn: 0.7-0.9%, Cr: 0.15-0.3%, Ni: 0.75-1.25%, Cu: 0.2-0.4%, P≤0.015%, O: 0.02-0.045%, the balance of iron and inevitable impurities.

6. The flux-cored wire according to claim 1, which is prepared by a method comprising the following steps: (1) high-temperature roasting of rutile and zirconite for standby; (2) medium-temperature roasting of quartz, aluminum oxide, fluorite, sodium fluoride, and magnesia for standby; (3) Copper powder, nickel powder, nano nickel powder, ferromanganese, ferrotitanium, electrolytic manganese, ferrochrome, aluminum-magnesium alloy, silicon-calcium alloy, silicon-manganese alloy, potassium titanate, and iron powder are baked at low temperature and then mixed evenly with the mineral powder baked in steps (1) and (2) to obtain core powder. (4) Roll the HS1 steel strip into a U-shape, add flux-cored powder into the U-shaped groove and close the joint, then roll it into shape and continuously draw it to reduce the diameter to obtain the welding wire. Mechanically clean the surface of the welding wire to obtain the flux-cored welding wire.

7. The flux-cored welding wire according to claim 6, wherein, In step (1), the parameters for high-temperature baking are: temperature 800~1000℃, time 3h~5h; In step (2), the parameters for medium-temperature baking are: temperature 300~500℃, time 2h~4h; In step (3), the parameters for low-temperature baking are: temperature 110~130℃, time 4h~6h; In step (4), the filling rate of the core powder is 14.0~18.0%; In step (4), the wire diameter is continuously reduced by drawing until it is 0.5~3mm.

8. The flux-cored welding wire according to claim 1, wherein the flux powder, by mass percentage, is a mixture of the following components: rutile 30%, zircon sand 3.4%, quartz 2.2%, alumina 3.4%, fluorite 3.0%, sodium fluoride 2.2%, magnesia 2.8%, copper powder 1.7%, nickel powder 4.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, and silicon-calcium alloy. 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, iron powder to make up to 100%; the filling rate of flux-cored wire is 15%; the deposited metal after welding includes the following chemical composition by mass percentage and the balance iron and unavoidable impurities: C: 0.045%, Si: 0.30%, Mn: 0.80%, Cr: 0.25%, Ni: 0.83%, Cu: 0.255%, P: 0.010%, O: 0.033%.

9. The flux-cored welding wire according to claim 1, wherein the flux powder, by mass percentage, is a mixture of the following components: rutile 30%, zircon sand 3.4%, quartz 2.2%, alumina 3.4%, fluorite 3.0%, sodium fluoride 2.2%, magnesia 2.8%, copper powder 1.7%, nickel powder 5.0%, nano nickel powder 1.5%, ferromanganese 1.8%, ferrotitanium 2.0%, electrolytic manganese 1.8%, ferrochrome 2.5%, aluminum-magnesium alloy 3.4%, and silicon-calcium alloy. 1.0%, silicon-manganese alloy 8.0%, potassium titanate 4.0%, iron powder to make up to 100%; the filling rate of flux-cored wire is 15%; the deposited metal after welding includes the following chemical composition by mass percentage and the balance iron and unavoidable impurities: C: 0.046%, Si: 0.29%, Mn: 0.82%, Cr: 0.26%, Ni: 0.97%, Cu: 0.253%, P: 0.009%, O: 0.028%.

10. The flux-cored wire according to claim 1, wherein the flux powder is made by mixing the following ingredients in mass percentage: rutile 30%, zircon 3.4%, quartz 2.2%, alumina 3.4%, fluorite 3.0%, sodium fluoride 2.2%, magnesia 2.8%, copper powder 1.6%, nickel powder 6.0%, nano-nickel powder 1.5%, manganese iron 1.8%, titanium iron 2.0%, electrolytic manganese 1.8%, chromium iron 2.5%, aluminum-magnesium alloy 3.4%, silicon-calcium alloy 1.0%, silicon-manganese alloy 8.0%, potassium silicate titanate 4.0%, and iron powder to make up to 100%; the filling rate of the flux powder in the flux-cored wire is 15%; and the deposited metal after welding of the wire comprises the following chemical components in mass percentage and the balance of iron and inevitable impurities: C: 0.046%, Si: 0.28%, Mn: 0.78%, Cr: 0.22%, Ni: 1.13%, Cu: 0.245%, P: 0.010%, and O: 0.025%.

11. The flux-cored wire according to claim 1, wherein the flux powder is made by mixing the following ingredients in mass percentage: rutile 31%, zircon 3.2%, quartz 2.0%, alumina 3.6%, fluorite 2.8%, sodium fluoride 2.4%, magnesia 2.6%, copper powder 2.0%, nickel powder 4.0%, nano-nickel powder 1.7%, manganese iron 2.0%, titanium iron 2.4%, electrolytic manganese 2.0%, chromium iron 2.5%, aluminum-magnesium alloy 3.4%, silicon-calcium alloy 1.0%, silicon-manganese alloy 8.0%, potassium silicate titanate 4.0%, and iron powder to make up to 100%; the filling rate of the flux powder in the flux-cored wire is 16%; and the deposited metal after welding of the wire comprises the following chemical components in mass percentage and the balance of iron and inevitable impurities: C: 0.043%, Si: 0.25%, Mn: 0.74%, Cr: 0.24%, Ni: 0.84%, Cu: 0.30%, P: 0.010%, and O: 0.031%.

12. The flux-cored wire according to claim 1, wherein the flux powder is made by mixing the following ingredients in mass percentage: rutile 29%, zircon 3.6%, quartz 2.4%, alumina 3.2%, fluorite 3.2%, sodium fluoride 2.0%, magnesia 3.0%, copper powder 1.9%, nickel powder 5.0%, nano-nickel powder 1.6%, manganese iron 1.8%, titanium iron 2.0%, electrolytic manganese 1.6%, chromium iron 2.7%, aluminum-magnesium alloy 3.2%, silicon-calcium alloy 0.8%, silicon-manganese alloy 8.2%, potassium silicate titanate 3.8%, and iron powder to make up to 100%; the filling rate of the flux powder in the flux-cored wire is 14%; and the deposited metal after welding of the wire comprises the following chemical components in mass percentage and the balance of iron and inevitable impurities: C: 0.048%, Si: 0.24%, Mn: 0.80%, Cr: 0.24%, Ni: 0.98%, Cu: 0.290%, P: 0.010%, and O: 0.029%.

13. The flux-cored wire according to claim 1, wherein the flux powder is made by mixing, in mass percentage, 30% of rutile, 3.4% of zirconite, 2.2% of quartz, 3.4% of aluminum oxide, 3.0% of fluorite, 2.2% of sodium fluoride, 2.8% of magnesia, 1.9% of copper powder, 6.0% of nickel powder, 1.3% of nano nickel powder, 1.6% of manganese iron, 1.8% of titanium iron, 1.8% of electrolytic manganese, 2.3% of chromium iron, 3.6% of aluminum-magnesium alloy, 1.2% of silicon-calcium alloy, 7.8% of silicon-manganese alloy, 4.2% of potassium silicon titanate, and iron powder to make up to 100%; the filling rate of the flux powder in the flux-cored wire is 18%; and the deposited metal after welding of the wire comprises the following chemical components in mass percentage and the balance of iron and inevitable impurities: C: 0.044%, Si: 0.28%, Mn: 0.78%, Cr: 0.23%, Ni: 1.12%, Cu: 0.294%, P: 0.010%, and O: 0.027%.

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