A welding material and a welding method for welding alloy steel

Abstract

The application provides a welding material and a welding method for welding alloy steel, and belongs to the technical field of welding materials. The welding material provided by the application replaces high-proportion Ni and Cr with Mn, N and Cu in cooperation, refines deoxidation by compounding Ti, V and Al, and greatly reduces the cost of noble metal raw materials; the base material adopts low-Si, a narrow impurity range and a Ti-Nb micro-alloy optimized component to inhibit the liquid metal embrittlement of the coating welding from the source; the welding process sets laser low-temperature micro-preheating, stage-differentiated protective gas and post-welding gradient slow cooling in cooperation with low-temperature tempering, does not damage the original mechanical properties of the base material throughout the process, solves the problems of high cost, many welding defects, poor fatigue and poor corrosion resistance of traditional high-chromium nickel welding wires, and is suitable for large-batch laser wire filling welding of automobile body high-strength steel.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to a welding material and welding method for welding alloy steel. Background Technology

[0002] Traditional resistance spot welding of galvanized / aluminum-silicon coated ultra-high-strength steel is prone to liquid metal embrittlement (LME), resulting in numerous porosities and microcracks in the weld, and a significant reduction in joint strength. Arc welding produces poor weld formation, unevenness, and inadequate fusion transition. Existing high-Cr-Ni stainless steel welding wires have extremely high nickel and chromium content, leading to high raw material costs and poor economic viability for mass production of automotive parts. The welding wires also suffer from severe work hardening, poor feeding stability with ultra-fine / coarse wires, and are prone to blockage and vibration at high speeds. The significant difference in thermal expansion coefficients between traditional high-nickel-chromium welding wires and low-Cr ultra-high-strength base materials results in high residual tensile stress at the weld interface after laser rapid melting and high-temperature heat treatment, making them susceptible to fatigue microcracks under alternating loads. Furthermore, the high carbon content of the welding wires facilitates Cr precipitation after post-weld heat treatment at 880-950℃. 23 C6 welds have a high risk of intergranular corrosion. Conventional welding wires lack grain refinement and strong deoxidizing components, causing the Al and Zn coatings to melt into the weld and form brittle intermetallic compounds. After long-term high and low temperature cycling, the mechanical properties of the joint continue to deteriorate. The process window is narrow, and the yield rate drops significantly when the plate thickness and coating thickness fluctuate.

[0003] Furthermore, existing welding wires are only compatible with pure laser filler wire processes and cannot be used with low-cost auxiliary processes; post-weld processing requires high-temperature hot stamping and quenching, with no simplified heat treatment route, resulting in significant investment in production line equipment. Directly reducing the Ni and Cr content of the welding wire will cause instability in the austenitic structure of the weld, leading to the formation of δ-ferrite, and the tensile strength and yield strength will not match those of the ultra-high strength base material; the deoxidation and degassing capabilities of the weld will decrease, and the porosity defects in the coated sheet will increase dramatically. Currently, there is a lack of a set of low-cost, low-precious-metal welding materials and matching welding processes that combine excellent welding metallurgical properties and stable joint mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a welding material and welding method for welding alloy steel. The welding material provided by this invention has a low precious metal content, which reduces costs, and also has excellent welding metallurgical properties and stable mechanical properties of the joint.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a welding material for welding alloy steel, wherein the alloy steel is an ultra-high strength steel with a surface anti-corrosion coating, and the welding material is a solid welding wire, comprising the following components by weight percentage: C 0.08~0.14%, Si 0.30~0.65%, Mn 2.5~4.0%, Cr 21.0~24.5%; Mo 0.05~0.15%, Ni 12.0~22.0%, N 0.10~0.16%, Cu 0.8~3.5%, Al 0.15~0.40%, Ti 0.02~0.10%, V 0.04~0.15%, balance Fe and unavoidable impurities.

[0006] Preferably, the diameter of the welding material is 1.2~1.3mm.

[0007] Preferably, the ultra-high strength steel comprises the following components by weight percentage: C 0.12~0.25%, Si 0.05~0.6%, Mn 1.80~3.20%, P≤0.018%, S≤0.008%, Al 0.06~0.20%, Ti 0.04~0.12%, Nb 0.02~0.08%, B 0.0020~0.0045%, Cr 0.10~1.80%, with the balance being Fe.

[0008] The present invention also provides a welding method for alloy steel using the welding material described in the above technical solution, comprising the following steps: Two ultra-high strength steel plates to be welded are joined together, the area to be welded is preheated, laser filler wire welding is used, and then gradient cooling and low temperature tempering are performed to complete the alloy steel welding.

[0009] Preferably, during the docking process, hydraulic precision tooling is used for clamping, with a bilateral positioning and clamping force of 3~5MPa, controlling the docking gap to ≤0.15mm and the misalignment to ≤0.08mm.

[0010] Preferably, the preheating treatment is performed using laser scanning, the power of which is 0.8~1.2kW and the walking speed of which is 8~10m / min.

[0011] Preferably, during the laser wire filler welding process, the main weld pool section uses a mixed gas consisting of 94v / v%Ar and 6v / v%N2 as the first protective gas, and the flow rate of the first protective gas is 16~25L / min.

[0012] Preferably, the conditions for laser wire filler welding include: laser power of 3.0~6.0kW, laser travel speed of 2~6m / min, wire feed speed of 0.5~2.2m / min, and laser spot size larger than the diameter of the welding material.

[0013] Preferably, the gradient cooling step includes: the weld area formed by welding is first cooled to 450-550°C at a rate of 8-12°C / s and held at that temperature for 10s, and then naturally cooled to 300°C with the second protective gas.

[0014] Preferably, the low-temperature tempering step includes: heating the welded alloy steel as a whole to 600~630℃, holding it at a constant temperature for 15~18 minutes, then slowly cooling it in the furnace to 300℃, and finally air cooling it to room temperature.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) Significantly reduce raw material costs. The amount of Ni and Cr used is reduced, and it is replaced by cheap Mn, N and Cu, which reduces the raw material cost of welding wire and is suitable for mass production of automobiles. (2) Strong ability to suppress welding defects. Adding a certain amount of Ti, Al and Mn can achieve multiple deoxidation. The coated plate is free of porosity, sand holes and microcracks during welding, which improves the welding yield, and the weld formation is regular and the fusion transition is smooth. (3) The mechanical properties match the base material, the tensile strength after welding is ≥1500MPa, Rp0.2≥1080MPa, the fracture location is mostly in the base material, the grain is refined, the impact toughness of the weld is improved, and the fatigue life under alternating load is significantly improved. (4) Improved corrosion resistance and high temperature stability; N and Cu enhance salt spray resistance; Ti fixes carbon; Cr-free after 900℃ heat treatment. 23 C6 precipitation eliminates the risk of intergranular corrosion, reduces residual stress in the weld and base material, and prevents the initiation of microcracks due to long-term vibration. (5) The process is highly versatile. Preheating treatment solves the problems of severe vaporization and micropores in the coating without damaging the base material. Gradient cooling releases the instantaneous welding stress without changing the structure of the base material. Low-temperature tempering completely releases the residual welding stress without precipitating carbides or softening the martensite of the base material. The mechanical properties of the base material do not decrease. The process window is wide and the plate thickness and coating thickness are highly adaptable. The wire feeding is stable and compatible with high-speed automated production lines. Attached Figure Description

[0016] Figure 1 This is a statistical chart of the tensile strength of the alloy steel welded parts prepared in Examples 1-3 and Comparative Examples 1-3 of this invention; Figure 2 This is a statistical chart showing the number of fatigue cycles (in ten thousand times) of the alloy steel welded parts prepared in Examples 1-3 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0017] This invention provides a welding material for welding alloy steel, wherein the alloy steel is an ultra-high strength steel with a surface anti-corrosion coating, and the welding material is a solid welding wire, comprising the following components by weight percentage: C 0.08~0.14%, Si 0.30~0.65%, Mn 2.5~4.0%, Cr 21.0~24.5%, Mo 0.05~0.15%, Ni 12.0~22.0%, N 0.10~0.16%, Cu 0.8~3.5%, Al 0.15~0.40%, Ti 0.02~0.10%, V 0.04~0.15%, balance Fe and unavoidable impurities.

[0018] In this invention, the welding material preferably comprises the following components by weight percentage: C 0.09~0.13%, Si 0.40~0.55%, Mn 3.0~3.8%, Cr 22.0~24.0%, Mo 0.07~0.13%, Ni 16.0~20.0%, N 0.10~0.16%, Cu 1.5~2.5%, Al 0.20~0.30%, Ti 0.04~0.08%, V 0.06~0.12%, with the balance being Fe and unavoidable impurities.

[0019] This invention utilizes the inexpensive austenite stabilizing element Mn to replace part of Ni, maintaining a single-phase austenitic structure in the weld and avoiding cracks caused by high-temperature ferrite. Mn strengthens solid solution, compensating for the loss of yield and tensile strength caused by the reduction of Ni, ensuring Rp0.2≥1100MPa and tensile strength≥1500MPa. Mn provides strong deoxidation to the molten pool, inhibiting the formation of porosity from O and N generated by Al / Zn coating vaporization, thus improving the welding yield of coated ultra-high-strength steel. It also enhances the fluidity of the molten pool, adapting to high-speed laser movement and reducing fusion defects caused by wire feeding fluctuations. It avoids the formation of MnS inclusions when Mn > 4%, which can induce intergranular microcracks after high-temperature heat treatment; the upper limit is strictly controlled at 4.0%, and it is combined with trace amounts of S to match the original base material system. N is a strong austenite stabilizing element; 0.01% N can replace 1% of the original austenite. Ni (Ni) significantly enhances the weld yield strength through solid solution strengthening, offsetting the strength decline caused by Ni reduction. Ni also refines austenite grains, improving weld impact toughness and addressing the issue of coarse grains in the original high-temperature heat-treated welding wire. Furthermore, it improves resistance to pitting and intergranular corrosion, compensating for the corrosion shortcomings caused by low Mo content and reduced Cr content. Ni inhibits the formation of brittle phases (Al-Fe, Zn-Ni) in the molten pool, improving the fatigue performance of dissimilar steel interfaces. It prevents porosity caused by smelting with Ni > 0.2%, which can lead to delamination and cracking during wire drawing. Matching a high-Mn system, Mn+N synergistically stabilizes austenite, preventing δ-ferrite formation. Cu, with a much lower price than Ni and also providing austenite stabilization, can replace 2-3% of Ni when added at 1.0-3.0%. Ni and Cu are weak solid solution strengthening elements, which will not excessively increase hardness or worsen the workability of welding wire. They can improve austenitic plasticity, making the welding wire less prone to breakage during drawing, and solving the problems of work hardening and wire feeding vibration in the original high-nickel welding wire. Cu can also improve the salt spray corrosion resistance of the weld, making it suitable for long-term service on galvanized and aluminum-silicon coated plates, reducing the surface tension of the molten pool, reducing spatter caused by coating vaporization, and making the weld formation more regular. Avoiding copper embrittlement caused by high-temperature heat treatment at 880~950℃ when Cu > 3.0% weakens grain boundaries and reduces fatigue life under alternating loads. Appropriately reducing Cr and combining it with Al provides inexpensive antioxidant compensation and reduces Ferrochrome consumption; simultaneously adding 0.15~0.35% Al to compensate for high-temperature oxidation resistance. Al preferentially combines with O to form Al2O3, protecting the Cr in the molten pool from oxidation and avoiding chromium depletion in the weld; eliminating oxygen impurities in the molten pool caused by partial metal vaporization in the coating, eliminating microporosity, refining the solidification structure of the molten pool, and improving the interfacial bonding strength between the weld and the base metal; reducing the addition of Cr and synergistically setting the Al content to reduce the cost of ferrochrome raw materials. Al preferentially oxidizes and protects the Cr in the molten pool, avoiding chromium depletion during high-temperature heat treatment and eliminating the risk of intergranular corrosion; trace amounts of Ti and V are added: Ti fixes free carbon to form TiC, inhibiting Cr... 23 C6 precipitation and V precipitation of nano-VC precipitate phase strengthen the matrix. Together, they refine the austenite grains and improve the impact toughness and fatigue life of the weld. The basic component C ensures the matrix strength, Si assists in deoxidation, and Mo maintains the basic pitting corrosion resistance.

[0020] In this invention, the ultra-high strength steel preferably comprises the following components by weight percentage: C 0.12~0.25%, Si 0.05~0.6%, Mn 1.80~3.20%, P≤0.018%, S≤0.008%, Al 0.06~0.20%, Ti 0.04~0.12%, Nb 0.02~0.08%, B 0.0020~0.0045%, Cr 0.10~1.80%, with the balance being Fe.

[0021] This invention employs a low-Si base material in ultra-high-strength steel to suppress Zn intergranular penetration, reducing weld microcrack length by over 70% while simultaneously reducing refractory SiO2 inclusions in the molten pool and eliminating micropores. The high-Mn base material dilutes the Al element in the weld coating, inhibiting the formation of soft δ-ferrite, ensuring a weld martensite content of ≥92% and preventing weld strength from falling below that of the base material. The strong Mn deoxidation, synergistic with the Mn+N system in the welding wire, doubles the deoxidation capacity of the molten pool. It significantly reduces low-melting-point P and S grain boundary films, preventing grain boundary cracking during rapid laser melting and solidification, eliminating MnS and FeP inclusions, and resulting in no micro-point defects in the metallographic structure. This invention improves welding yield by precisely micro-alloying a narrow range of ultra-high strength steel base material. While maintaining the hot stamping strength and toughness of the ultra-high strength steel base material, it fundamentally suppresses three major defects—coating welding porosity, LME cracks, and soft phase in the weld—from the base material side. Nitrogen (Nb), as a trace refining element, reduces the hardness difference between the base material and the weld. The base material itself contains trace amounts of Al for pre-deoxidation, resulting in a thinner oxide layer on the plate surface, eliminating the need for pretreatment during welding. Al preferentially combines with O in the molten pool, protecting the Cr in the welding wire from oxidation and reducing chromium depletion in the weld. Ti in the base material combines with the coating to form stable compounds, preventing the continuous precipitation of brittle intermetallic compounds. Simultaneously, N in the molten pool is fixed, eliminating nitrogen porosity. Trace amounts of Nb refine the grains in the heat-affected zone of the base material, reducing the hardness gradient between the base material and the weld, coordinating deformation, and ensuring that tensile fracture occurs stably in the base material, preventing weld failure from occurring first. This invention, through precise narrow-range micro-alloying of the ultra-high strength steel base material, suppresses three major defects from the base material side: welding porosity, LME cracks, and soft phase in the weld, while maintaining the hot stamping strength and toughness of the ultra-high strength steel base material. It also forms a two-way metallurgical match with the welding wire, significantly improving welding performance.

[0022] In this invention, the material of the anti-corrosion coating is preferably at least one selected from aluminum-silicon, zinc, nickel, and chromium; the thickness of the anti-corrosion coating is preferably 5-80 μm. In this invention, the thickness of the ultra-high strength steel plate is preferably 0.8-4 mm. In this invention, the diameter of the welding material is preferably 1.2-1.3 mm.

[0023] The present invention also provides a welding method for alloy steel using the welding material described in the above technical solution, comprising the following steps: Two ultra-high strength steel plates to be welded are joined together, the area to be welded is preheated, laser filler wire welding is used, and then gradient cooling and low temperature tempering are performed to complete the alloy steel welding.

[0024] In this invention, during the docking process, hydraulic precision tooling is preferably used for clamping, with a bilateral positioning and clamping force of 3~5MPa, controlling the docking gap to ≤0.15mm and the misalignment to ≤0.08mm. In this invention, after the docking is completed, the process preferably includes: using compressed air to blow away surface dust from the area to be welded for 3~5 seconds.

[0025] In this invention, the preheating treatment preferably employs laser scanning, with a preferred laser scanning power of 0.8~1.2kW and a preferred laser scanning travel speed of 8~10m / min. In this invention, the preheating treatment preferably uses Ar gas with a flow rate of 12L / min as a protective gas. This invention uses Ar gas as a protective gas in the preheating treatment to isolate it from air and prevent oxidation.

[0026] In this invention, the main weld pool section during laser wire-filled welding preferably uses a mixture of 94% Ar and 6% N2 as the first shielding gas. The flow rate of the first shielding gas is preferably 16-25 L / min. This invention uses the above-mentioned flow rate and composition of the first shielding gas to utilize nitrogen to help stabilize austenite and improve the corrosion resistance of the weld.

[0027] In this invention, the preferred conditions for laser wire filler welding include: laser power of 3.0~6.0kW, laser travel speed of 2~6m / min, wire feed speed of 0.5~2.2m / min, and laser spot size larger than the diameter of the welding material. By controlling the laser wire filler welding conditions within the above ranges, this invention achieves stable welding without fusion defects.

[0028] In this invention, the gradient cooling step preferably includes: the weld area formed by welding is first cooled to 450-550°C at a rate of 8-12°C / s and held at that temperature for 10s, and then naturally cooled to 300°C with a second protective gas. This invention utilizes gradient cooling to avoid the rapid contraction of the high-temperature molten pool, which generates huge residual tensile stress. The temperature throughout the process is below the hot stamping quenching temperature of the base material (900°C), thus not altering the martensitic matrix of the base material, and fully preserving its tensile and yield strength.

[0029] In this invention, the low-temperature tempering step preferably includes: heating the welded alloy steel as a whole to 600~630℃, holding it at that temperature for 15~18 minutes, then slowly cooling it in the furnace to 300℃, and finally air-cooling it to room temperature. This invention utilizes low-temperature tempering to completely release residual welding stress, preventing carbide precipitation, softening of the base metal martensite, and maintaining the mechanical properties of the base metal.

[0030] The welding material provided by this invention uses Mn, N, and Cu to synergistically replace the high proportion of Ni and Cr, and is compounded with Ti, V, and Al for refined deoxidation, significantly reducing the cost of precious metal raw materials. The base material adopts a low-Si, narrow-impurity range, and Ti-Nb microalloyed optimized composition to inhibit the embrittlement of the liquid metal in the weld coating from the source. The welding process is designed with laser low-temperature micro-preheating, staged differentiated shielding gas, and post-weld gradient slow cooling, combined with low-temperature tempering, without damaging the original mechanical properties of the base material throughout the process. Tests show that the welded joint has a tensile strength ≥1520MPa and an Rp0.2 ≥1080MPa, with fractures occurring entirely in the base material. The weld is free of porosity and cracks. There is no significant corrosion after 500 hours of neutral salt spray testing, and the fatigue life is improved by more than 20% compared to existing welding wires. This solves the problems of high cost, numerous weld defects, and poor fatigue and corrosion resistance of traditional high-chromium nickel welding wires, and is suitable for mass laser filler wire welding of high-strength steel for automotive bodies.

[0031] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0032] Unless otherwise specified, all experiments were repeated three times, and the results are expressed as averages.

[0033] Example 1 A welding material for welding alloy steel, wherein the alloy steel is an ultra-high strength steel with a surface anti-corrosion coating, and the welding material is a solid welding wire, comprising, by weight percentage: The composition of the welding material is as follows: C 0.11%, Si 0.48%, Mn 3.5%, Cr 23.0%, Mo 0.10%, Ni 18.0%, N 0.13%, Cu 2.0%, Al 0.25%, Ti 0.06%, V 0.09%, balance Fe; the diameter of the welding wire used in the welding material is 1.2 mm. The ultra-high strength steel composition, by weight percentage, is: C 0.18%, Si 0.4%, Mn 2.4%, P 0.012%, S 0.005%, Al 0.12%, Ti 0.07%, Nb 0.04%, B 0.0030%, Cr 0.80%, with the balance being Fe; The anti-corrosion coating is a single-sided aluminum-silicon coating with a thickness of 10μm; the ultra-high strength steel base material has a plate thickness of 1.2mm, and the thick dumbbell-shaped sample is 240mm×20mm; The mechanical properties of the base material were verified and tested according to the standard GB / T 228.1-202. The results showed that the basic properties of the base material after hot stamping were: tensile strength 1535MPa, Rp0.2=1112MPa. The welding method for alloy steel using the aforementioned welding material comprises the following steps: The two ultra-high strength steel plates to be welded were joined together, and the surface dust of the area to be welded was blown away with compressed air for 3 seconds. The area to be welded was preheated, and laser filler wire welding was used. Then, gradient cooling and low temperature tempering were performed to complete the alloy steel welding. During the docking process, hydraulic precision tooling is used for clamping, with a double-sided positioning and clamping force of 4MPa, controlling the docking gap to be 0.12mm and the misalignment to be 0.06mm; The preheating process employs laser scanning with a power of 1.0 kW and a travel speed of 9 m / min; the preheating process uses Ar gas with a flow rate of 12 L / min as a protective gas. The main molten pool welding section in the laser wire filler welding process uses a mixed gas consisting of 94v / v%Ar and 6v / v%N2 as the first shielding gas; the flow rate of the first shielding gas is 20L / min; the conditions for laser wire filler welding are: laser power of 4.5kW, laser travel speed of 4m / min, wire feed speed of 1.2m / min, and laser spot size larger than the diameter of the welding material. The gradient cooling step is as follows: the weld area formed by welding is first cooled to 500℃ at a rate of 10℃ / s and held at that temperature for 10s, and then naturally cooled to 300℃ with the second protective gas; the low-temperature tempering step is as follows: the welded alloy steel is heated to 620℃, held at that temperature for 16min, then slowly cooled to 300℃ with the furnace, and finally air-cooled to room temperature.

[0034] Example 2 The difference from Example 1 is that, by weight percentage, the welding material composition is: C 0.09%, Si 0.40%, Mn 3.8%, Cr 22.0%, Mo 0.07%, Ni 16.0%, N 0.16%, Cu 2.5%, Al 0.30%, Ti 0.08%, V 0.12%, with the balance being Fe.

[0035] Example 3 The difference from Example 1 is that, by weight percentage, the welding material composition is: C 0.13%, Si 0.55%, Mn 3.0%, Cr 24.0%, Mo 0.13%, Ni 20.0%, N 0.10%, Cu 1.5%, Al 0.20%, Ti 0.04%, V 0.06%, with the balance being Fe.

[0036] Comparative Example 1 The difference from Example 1 is that, by weight percentage, the welding material composition is: C 0.1%, Si 0.5%, Mn 2.0%, Cr 28.0%, Mo 0.11%, Ni 24.3%, with the balance being Fe.

[0037] Comparative Example 2 The difference from Example 1 is that, by weight percentage, the welding material composition is: C 0.11%, Si 0.48%, Mn 2.0%, Cr 23.0%, Mo 0.10%, Ni 18.0%, with the balance being Fe.

[0038] Comparative Example 3 The difference from Example 1 is as follows: Two ultra-high strength steel plates to be welded are butted together, and welding material is placed between the welding areas of the two workpieces to be welded. The welding material is melted by laser wire filling welding, and the molten welding material covers at least a portion of the welding area. The molten welding material cools and solidifies, so that the two workpieces to be welded are connected into one piece. The laser wire filling welding power is 5950W, and the laser moving speed is 5m / min. The welded sample is heat-treated at a temperature of 950℃ for 5 minutes. Then it is quickly transferred to a mold with cooling water circulating inside for compaction, pressure held and cooled for 15 seconds. The nominal force of the press is 1000KN, and the cooling rate is greater than 30℃ / s.

[0039] The properties of the alloy steel welded parts prepared in Examples 1-3 and Comparative Examples 1-3 were tested according to the following method, and the results are shown in Table 1.

[0040] Tensile mechanical property testing, standard: GB / T 228.1-2021; Weld metallographic defect testing, standard: GB / T 15125-2009; Neutral salt spray corrosion resistance testing, standard: GB / T 10125-2021; Alternating fatigue performance testing, standard: GB / T 3075-2023. Figure 1 This is a statistical chart of the tensile strength of the alloy steel welded parts prepared in Examples 1-3 and Comparative Examples 1-3 of this invention; Figure 2 This is a statistical chart showing the number of fatigue cycles (in ten thousand times) of the alloy steel welded parts prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0041] Table 1. Performance statistics of alloy steel welded parts prepared in Examples 1-3 and Comparative Examples 1-3

[0042] In summary, this invention optimizes the narrow range of microalloyed base material, utilizes low-cost multi-element synergistic modified welding wire, and employs a segmented gradient laser filler welding process. While fully preserving the original high plasticity and hardenability of the ultra-high-strength alloy steel base material, it significantly reduces the cost of precious metal raw materials for the welding wire. Simultaneously, it thoroughly solves multiple industry problems related to high-strength steel with anti-corrosion coatings, such as porosity, LME grain boundary cracks, insufficient weld strength, intergranular corrosion, and low fatigue life. The joint's mechanical, corrosion-resistant, and fatigue properties are comprehensively superior to existing technologies, making it suitable for large-scale automated laser welding production of high-strength steel for hot stamping in automotive bodies. It possesses outstanding economic benefits and industrial application value.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A welding material for welding alloy steel, wherein the alloy steel is an ultra-high strength steel with a surface-coated anti-corrosion coating, characterized in that, The welding material is a solid welding wire, and by weight percentage, it contains the following components: C 0.08~0.14%, Si 0.30~0.65%, Mn 2.5~4.0%, Cr 21.0~24.5%, Mo 0.05~0.15%, Ni 12.0~22.0%, N 0.10~0.16%, Cu 0.8~3.5%, Al 0.15~0.40%, Ti 0.02~0.10%, V 0.04~0.15%, balance Fe and unavoidable impurities.

2. The welding material according to claim 1, characterized in that, The diameter of the welding material is 1.2~1.3mm.

3. The welding material according to claim 1, characterized in that, The ultra-high strength steel comprises the following components by weight percentage: C 0.12~0.25%, Si 0.05~0.6%, Mn 1.80~3.20%, P≤0.018%, S≤0.008%, Al 0.06~0.20%, Ti 0.04~0.12%, Nb 0.02~0.08%, B 0.0020~0.0045%, Cr 0.10~1.80%, with the balance being Fe.

4. A welding method for alloy steel using the welding material described in any one of claims 1 to 3, characterized in that, Includes the following steps: Two ultra-high strength steel plates to be welded are joined together, the area to be welded is preheated, laser filler wire welding is used, and then gradient cooling and low temperature tempering are performed to complete the alloy steel welding.

5. The welding method according to claim 4, characterized in that, During the docking process, hydraulic precision tooling is used for clamping, with a double-sided positioning and clamping force of 3~5MPa, controlling the docking gap to ≤0.15mm and the misalignment to ≤0.08mm.

6. The welding method according to claim 4, characterized in that, The preheating process employs laser scanning, with a power of 0.8~1.2kW and a travel speed of 8~10m / min.

7. The welding method according to claim 4, characterized in that, During the laser wire filler welding process, the main molten pool welding section uses a mixed gas consisting of 94v / v%Ar and 6v / v%N2 as the first protective gas, and the flow rate of the first protective gas is 16~25L / min.

8. The welding method according to claim 4, characterized in that, The conditions for laser wire filler welding include: laser power of 3.0~6.0kW, laser travel speed of 2~6m / min, wire feed speed of 0.5~2.2m / min, and laser spot size larger than the diameter of the welding material.

9. The welding method according to claim 4, characterized in that, The gradient cooling step includes: the weld area formed by welding is first cooled to 450-550°C at a rate of 8-12°C / s and held at that temperature for 10s, and then naturally cooled to 300°C with the second protective gas.

10. The welding method according to claim 4, characterized in that, The low-temperature tempering step includes: heating the welded alloy steel as a whole to 600~630℃, holding it at a constant temperature for 15~18 minutes, then slowly cooling it in the furnace to 300℃, and finally air cooling it to room temperature.

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