Tailor-welded component, and manufacturing method therefor and welding wire applied thereto

Abstract

A tailor-welded component, and a manufacturing method therefor and a welding wire applied thereto. The tailor-welded component comprises a welded joint. A weld seam of the welded joint comprises acicular ferrite and martensite. The acicular ferrite has an average length of not greater than 80 μm and an average diameter of not greater than 15 μm, and the volume percentage of the ferrite in the weld seam is 0.1-10%. The tailor-welded component is a hot-stamped component, the welded joint has an elongation of greater than 4%, the weld seam structure comprises the martensite and the acicular ferrite, a fracture position is located at a base material during a quasi-static tensile test, and the weld seam has a good strength and ductility.

Description

A welded component and its manufacturing method, and a welding wire used in the welded component. Technical Field

[0001] This invention belongs to the field of hot stamping component preparation technology, specifically relating to a welded component and its manufacturing method, and a welding wire applied to the welded component. Background Technology

[0002] Lightweight and high-strength automotive steel sheets have become a growing goal in the automotive industry in recent years. Hot stamping technology, compared to cold stamping, offers significant advantages such as weight reduction, better formability, and higher dimensional accuracy, playing a crucial role in achieving high strength in automotive steel sheets. As consumer demands for automotive safety, reliability, and comfort increase, many automakers are improving product quality by refining vehicle structural design and adopting new manufacturing processes. Welded sheets are made by welding several steel sheets of the same or different materials, thicknesses, and coatings together to meet the varying material performance requirements of different components. Laser-welded hot stamping technology can reduce vehicle weight, improve assembly accuracy, and simplify assembly steps, while also leveraging the advantages of hot stamping to further enhance the formability of the steel sheet. Hot-stamped products formed using laser-welded sheets are characterized by high strength, complex shapes, good formability, high dimensional accuracy, and low springback.

[0003] Hot-stamping steel can be divided into bare steel sheets and coated steel sheets according to their surface condition. In the actual hot-stamping process, the surface of bare steel sheets is prone to oxidation at high temperatures, forming oxide scale. During the stamping process, the oxide scale is squeezed into the steel, forming surface defects and greatly affecting its performance. Coated hot-stamping steel sheets, compared to bare steel sheets, can protect the steel sheet from oxidation while eliminating the need for shot peening or pickling after hot stamping. Therefore, coated hot-stamping steel sheets are receiving increasing attention. Currently, aluminum or aluminum alloy coated hot-stamping steel is commonly used. However, when welding this type of steel, the coating melts into the molten pool, forming brittle and hard intermetallic compounds (Fe3Al, Fe2Al5, FeAl3) and ferrite, which reduces the strength and ductility of the weld joint, rendering it unusable. Summary of the Invention

[0004] Therefore, the technical problem to be solved by this invention is to overcome the problem that when steel plates with aluminum or aluminum alloy coatings are made into welded plates, the coating melts into the molten pool, forming brittle and hard intermetallic compounds and ferrite, which leads to poor weld performance and affects the strength and elongation of the welded joint. This invention provides a welded component, its manufacturing method, and a welding wire for use in hot-stamped welded components. The welded component described in this invention is a welded component obtained after hot stamping.

[0005] To this end, the present invention provides the following technical solution.

[0006] The present invention provides a welded component, the welded component including a welded joint, wherein the microstructure of the weld seam of the welded joint includes acicular ferrite and martensite, wherein the average length of the acicular ferrite is not greater than 80 μm and the average diameter is not greater than 15 μm, and the volume percentage of acicular ferrite in the weld seam is 0.1-10%.

[0007] In one alternative embodiment, the weld, by weight percentage, comprises 0.08% ≤ C ≤ 0.45%, 0.05% ≤ Si ≤ 1.1%, 0.5% ≤ Mn ≤ 4.4%, P ≤ 0.015%, S ≤ 0.01%, 0.01% ≤ Al ≤ 1.5%, 0.5% ≤ Ni ≤ 3.5%, Cr ≤ 1.4%, Co ≤ 1.6%, Nb ≤ 3.4%, Ti ≤ 0.95%, V ≤ 0.85%, Cu ≤ 0.8%, Mo ≤ 2.1%, Zr ≤ 0.45%, B ≤ 0.25%, with the balance being Fe and unavoidable impurities.

[0008] In one alternative embodiment, the weld comprises 0.08% ≤ C ≤ 0.37%, and / or 0.6% ≤ Mn ≤ 2.8%, and / or 0.6% ≤ Ni < 2.0%.

[0009] In one alternative embodiment, the average diameter of the acicular ferrite is not greater than 10 μm; and / or, the average length of the acicular ferrite is not greater than 50 μm.

[0010] In one alternative embodiment, the width of the weld is 0.7-2.0 mm.

[0011] In one alternative embodiment, the welded component includes at least two steel plates welded together via the weld joint, wherein the steel plates include a steel plate substrate and an aluminum-containing or aluminum alloy coating disposed on at least one surface of the steel plate substrate.

[0012] In one optional embodiment, the tensile strength of the steel plate matrix after hot stamping of each steel plate is 500-2100 MPa, preferably 1700-2100 MPa.

[0013] In one alternative embodiment, the thickness of the steel plate substrate of each steel plate is 0.5-4 mm.

[0014] In one alternative embodiment, the coating of each steel sheet comprises, by weight percentage, 5 wt% ≤ Si ≤ 11 wt%, 0 ≤ Fe ≤ 4 wt%, with the balance being aluminum and unavoidable impurities.

[0015] In one alternative embodiment, the single-sided weight of each steel plate coating is 5-140 g / m². 2 Preferably, it is 30-100 g / m2 .

[0016] In one alternative embodiment, the composition of the steel plate matrix of each steel plate includes: 0.06% ≤ C ≤ 0.50%, 0.01% ≤ Si ≤ 1.0%, 0.5% ≤ Mn ≤ 5.0%, P ≤ 0.015%, S ≤ 0.01%, 0.01% ≤ Al ≤ 0.3%, Cr ≤ 1.0%, Nb ≤ 0.2%, V ≤ 0.1%, Ti ≤ 0.2%, Mo ≤ 0.5%, Ni ≤ 0.5%, B ≤ 0.08%, N ≤ 0.006%, with the balance being Fe and unavoidable impurities.

[0017] In one alternative embodiment, the composition of the steel plate matrix of each steel plate includes: 0.20% ≤ C ≤ 0.45%, 0.05% ≤ Si ≤ 1.0%, 0.5% ≤ Mn ≤ 3.0%, P ≤ 0.015%, S ≤ 0.01%, 0.01% ≤ Al ≤ 0.3%, Cr ≤ 1.0%, Nb ≤ 0.2%, V ≤ 0.1%, Ti ≤ 0.2%, Mo ≤ 0.5%, Ni ≤ 0.5%, B ≤ 0.08%, N ≤ 0.006%, with the balance being Fe and unavoidable impurities.

[0018] In one alternative embodiment, the composition of the steel plate matrix of each steel plate includes: 0.30% ≤ C ≤ 0.40%, 0.05% ≤ Si ≤ 1.0%, 0.5% ≤ Mn ≤ 2.0%, P ≤ 0.015%, S ≤ 0.01%, 0.01% ≤ Al ≤ 0.3%, Cr ≤ 1.0%, Nb ≤ 0.2%, V ≤ 0.1%, Ti ≤ 0.2%, Mo ≤ 0.5%, Ni ≤ 0.5%, B ≤ 0.08%, N ≤ 0.006%, with the balance being Fe and unavoidable impurities.

[0019] The present invention also provides a welding wire for preparing the above-mentioned welded components, comprising, by weight percentage: 0.16% <C≤0.39%,0.2%≤Si≤1.4%,0.8%≤Mn≤2.0%,3.0%<Ni≤8.0%,0.06%<Al≤1.5%,P≤0.015%,S≤0.008%。

[0020] In one optional embodiment, the welding wire further includes at least one of Co, Cu, Cr, Ti, V, Mo, Nb, Zr, and B;

[0021] Preferably, Cu≤2.0%, Cr≤2.0%, Ti≤2.0%, V≤2.0%, Zr≤1.0%, B≤0.5%, Co+Cu≤6.0%, Cr+Mo+B≤5.0%, Ti+Zr+Nb+V≤8.0%;

[0022] Preferably, the welding wire further includes Mo and Cr.

[0023] In one optional embodiment, the welding wire comprises 0.161 wt% ≤ C ≤ 0.25 wt%; and / or 1.0% ≤ Mn ≤ 1.95%; and / or 3.05% ≤ Ni ≤ 4.95%.

[0024] The present invention provides a method for manufacturing the above-mentioned welded component, comprising the step of welding at least two steel plates to be welded together by laser filler wire welding or laser MAG composite welding using the welding wire described in any embodiment of the present invention.

[0025] In one optional embodiment, the parameters for laser wire filler welding are: linear energy of 20-250 J / mm and wire feed speed of 2-18 m / min; or,

[0026] The parameters for the laser-MAG hybrid welding are: laser heat source linear energy of 5-40 J / mm, arc heat source linear energy of 8-27 J / mm, and wire feed speed of 2.5-30 m / min; and / or,

[0027] The steel plate to be welded includes a steel plate substrate, wherein the tensile strength of the steel plate substrate after hot stamping is 500-2100 MPa; preferably, the tensile strength of the steel plate substrate after hot stamping is 1700-2100 MPa; and / or,

[0028] The thickness of the steel plate substrate is 0.5-4 mm.

[0029] In one optional embodiment, the steel plate to be welded further includes an aluminum-containing or aluminum alloy coating disposed on at least one surface of the steel plate substrate.

[0030] Preferably, the coating composition, by weight percentage, includes 5wt% ≤ Si ≤ 11wt%, 0 ≤ Fe ≤ 4wt%, with the balance being aluminum and unavoidable impurities.

[0031] In one alternative embodiment, the composition of the steel plate matrix, by weight percentage, comprises: 0.06% ≤ C ≤ 0.50%, 0.01% ≤ Si ≤ 1.0%, 0.5% ≤ Mn ≤ 5.0%, P ≤ 0.015%, S ≤ 0.01%, 0.01% ≤ Al ≤ 0.3%, Cr ≤ 1.0%, Nb ≤ 0.2%, V ≤ 0.1%, Ti ≤ 0.2%, Mo ≤ 0.5%, Ni ≤ 0.5%, B ≤ 0.08%, N ≤ 0.006%, with the balance being Fe and unavoidable impurities;

[0032] Preferably, the composition of the steel plate matrix includes: 0.20%≤C≤0.45%, 0.05%≤Si≤1.0%, 0.5%≤Mn≤3.0%, P≤0.015%, S≤0.01%, 0.01%≤Al≤0.3%, Cr≤1.0%, Nb≤0.2%, V≤0.1%, Ti≤0.2%, Mo≤0.5%, Ni≤0.5%, B≤0.08%, N≤0.006%, with the balance being Fe and unavoidable impurities;

[0033] Preferably, the composition of the steel plate matrix includes: 0.30%≤C≤0.40%, 0.05%≤Si≤1.0%, 0.5%≤Mn≤2.0%, P≤0.015%, S≤0.01%, 0.01%≤Al≤0.3%, Cr≤1.0%, Nb≤0.2%, V≤0.1%, Ti≤0.2%, Mo≤0.5%, Ni≤0.5%, B≤0.08%, N≤0.006%, with the balance being Fe and unavoidable impurities.

[0034] In some embodiments, the tensile strength of the steel plate matrix is ​​in the range of 400-650 MPa.

[0035] The technical solution of this invention has the following advantages:

[0036] 1. The welded component provided by this invention includes a welded joint, the weld of which comprises acicular ferrite and martensite. The average length of the acicular ferrite is not greater than 80 μm, the average diameter is not greater than 15 μm, and the volume percentage of ferrite in the weld is 0.1-10%. The welded component of this invention is a component after hot stamping treatment. The joint elongation of the welded component is greater than 4%, the weld microstructure is martensite and ferrite, and the fracture location is located in the base material during quasi-static tensile testing. The weld exhibits good strength and ductility. This invention, on the one hand, avoids the formation of excessive ferrite in the weld, ensuring the strength and ductility of the weld; on the other hand, it avoids the formation of iron-aluminum intermetallic compounds in the weld and retains an appropriate amount of ferrite in the weld. This invention controls the aluminum content in the weld seam of the welded plate, making it dispersed and reducing the agglomeration of aluminum, ensuring uniform weld composition, and making the weld performance more stable; it avoids the formation of intermetallic compounds and excessive ferrite in the weld, especially preventing the formation of large blocky ferrite due to aluminum agglomeration, thereby ensuring the strength and ductility of the weld and meeting the performance requirements of automotive welded components.

[0037] Furthermore, the weld of the welded component of this invention includes dispersed acicular ferrite and martensite. The average length of the ferrite is no greater than 80 μm, the average diameter is no greater than 15 μm, and the volume percentage of dispersed ferrite in the weld is 0.1-10%. Martensite is characterized by high strength and hardness, but poor deformation capacity; ferrite is characterized by good plasticity and toughness, and strong deformation capacity. The weld microstructure, including martensite and dispersed acicular ferrite, provides more opportunities for coordinated deformation of martensite compared to a weld joint with a single martensite microstructure, under external force. The substructure of martensite is mainly dislocations, and dislocation accumulation easily forms microcracks. The ferrite in the weld significantly reduces the dislocation density formed by the martensite transformation in that region compared to a weld microstructure of single martensite, thus significantly reducing the risk of microcrack formation. Even if microcracks do form, the dispersed ferrite hinders their further growth and propagation. Welded joints with a weld microstructure consisting of martensite and dispersed acicular ferrite exhibit better deformation capacity and thus better weld ductility than welded joints with a single martensite microstructure.

[0038] 2. The welding wire provided by the present invention for preparing welded components includes elements such as C, Mn, Ni, Al, P and S. This welding wire ensures the control of the chemical composition of the weld, improves the weld strength, and guarantees the formation of an appropriate amount of ferrite and the conversion rate of martensite.

[0039] Introducing molybdenum, chromium, and nickel into welding wire can improve the fatigue performance of the joint, achieve a high martensite conversion rate in the weld microstructure, and enhance the mechanical properties of the welded joint; the effect is even better when molybdenum, chromium, and nickel are introduced simultaneously. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 is a quasi-static tensile curve of the welded joint of the welded component in Embodiment 1 of the present invention;

[0042] Figure 2 shows a sample after tensile fracture of the welded joint of the welded component in Embodiment 1 of the present invention;

[0043] Figure 3 is a metallographic image of the welded joint of the welded component in Embodiment 1 of the present invention;

[0044] Figure 4 is a metallographic image of the weld seam of the welded component in Embodiment 1 of the present invention;

[0045] Figure 5 is a hardness distribution diagram of the welded joint of the welded component in Embodiment 1 of the present invention;

[0046] Figure 6 is a metallographic image of the weld seam of the welded component of Comparative Example 3 of the present invention. Detailed Implementation

[0047] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0048] Where specific experimental steps or conditions are not specified in the examples, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagents or instruments.

[0049] A first aspect of this invention provides a welded component, comprising a welded joint, wherein the microstructure of the weld seam comprises acicular ferrite and martensite, the average length of the acicular ferrite being no greater than 80 μm and the average diameter being no greater than 15 μm, and the volume fraction of the acicular ferrite in the weld seam is 0.1-10%. It should be noted that the acicular ferrite is dispersedly distributed in the weld seam. In some embodiments, the microstructure of the weld seam consists of martensite and acicular ferrite.

[0050] In some embodiments, the average diameter of the acicular ferrite is ≤10 μm. In some embodiments, the average diameter of the acicular ferrite is 1-15 μm. In some embodiments, the average diameter of the acicular ferrite is 1-10 μm.

[0051] In some embodiments, the average length of the acicular ferrite is ≤50 μm. In some embodiments, the average length of the acicular ferrite is 10-80 μm. In some embodiments, the average length of the acicular ferrite is 10-50 μm. In some embodiments, the average length of the acicular ferrite is 20-50 μm.

[0052] In some embodiments, the volume percentage of acicular ferrite in the weld is 1.5-10%. In some embodiments, the volume percentage of acicular ferrite in the weld is 3.0-9.0%.

[0053] The composition and content of the weld, by weight percentage, include: 0.08%≤C≤0.45%, 0.05%≤Si≤1.1%, 0.5%≤Mn≤4.4%, P≤0.015%, S≤0.01%, 0.01%≤Al≤1.5%, 0.5%≤Ni≤3.5%, Cr≤1.4%, Co≤1.6%, Nb≤3.4%, Ti≤0.95%, V≤0.85%, Cu≤0.8%, Mo≤2.1%, Zr≤0.45%, B≤0.25%, with the balance being Fe and unavoidable impurities.

[0054] Preferably, the weld seam comprises 0.08% ≤ C ≤ 0.37%, and / or 0.6% ≤ Mn ≤ 2.8%, and / or 0.6% ≤ Ni < 2.0%.

[0055] The carbon content in the weld should be 0.08% ≤ C ≤ 0.45% to ensure the weld's plasticity and toughness. Under the same conditions, a higher carbon content can prolong the incubation period before the austenite-to-martensite transformation, lower the Ms temperature, and improve the weld's hardenability and hardenability. Excessive carbon content reduces the weld's plasticity and toughness. The preferred carbon content in the weld is 0.08% ≤ C ≤ 0.37%.

[0056] Silicon is a deoxidizing element that prevents iron from combining with oxygen and can reduce iron oxide. The silicon content in the weld should be 0.05% ≤ Si ≤ 1.1%. Excessive silicon content results in fine oxide particles that are difficult to float from the molten pool, causing slag inclusions in the weld. In some embodiments, the silicon content in the weld is preferably 0.20-1.1%. In other embodiments, the silicon content in the weld is preferably 0.50-1.1%.

[0057] Manganese is an element that infinitely expands the austenite region and promotes austenite grain growth, but it is also a carbide-forming element. Increasing the manganese content improves the strength and low-temperature impact toughness of the steel, but weakens its corrosion resistance and reduces its weldability. Therefore, the manganese content in the weld of this invention is 0.5% ≤ Mn ≤ 4.4%, preferably 0.6% ≤ Mn ≤ 2.8%.

[0058] Nickel is an element that infinitely expands the austenite region, is a non-carbide-forming element, and improves the hardenability and strength of steel while maintaining good plasticity and toughness. Nickel also improves corrosion resistance and low-temperature impact toughness. However, the inventors discovered in their research that higher nickel content in the weld is not always better; reaching a certain value increases the risk of weld fracture in the assembled components. Furthermore, due to the high price of nickel, cost is also a significant factor. Therefore, the nickel content in the weld of this invention is 0.5% ≤ Ni ≤ 3.5%, preferably 0.6% ≤ Ni < 2.0%.

[0059] The inventors discovered that an aluminum content of no more than 1.5 wt% in the weld can promote the formation of an appropriate amount of ferrite, improve the ductility of the weld, and reduce the risk of weld cracking. However, when the aluminum content exceeds 1.5 wt%, the ferrite in the weld significantly reduces the strength and ductility of the joint. Therefore, the aluminum content in the weld is controlled at 0.01% ≤ Al ≤ 1.5%. In some embodiments, the Al content in the weld is 0.3-1.5%. In some embodiments, the Al content in the weld is 0.6-1.3%.

[0060] Sulfur readily forms iron sulfide in the molten pool, which is distributed in a network at the grain boundaries, significantly reducing the toughness of the weld. The lower the content, the better. Considering the smelting technology and smelting cost, the S content in the weld should be controlled to be ≤0.01%.

[0061] Phosphorus plays a strengthening role in steel second only to carbon, increasing the strength and hardness of steel. Phosphorus can improve the corrosion resistance of steel, but it significantly reduces plasticity and toughness, especially at low temperatures. Therefore, phosphorus in welds is harmful and its content must be strictly controlled to P≤0.015%.

[0062] The weld also includes at least one of Co, Cu, Cr, Ti, V, Mo, Nb, Zr, and B. Cobalt and copper, as elements that expand the austenite phase region, improve the strength and corrosion resistance of steel and are interchangeable within a certain composition range. However, the inventors found that the content of these two elements in the weld is not necessarily better the higher it is; it should be controlled to Cu ≤ 0.8% and Co ≤ 1.6%. In some embodiments, the Cu content in the weld is controlled to ≤ 0.5%. In some embodiments, the Co content in the weld is controlled to ≤ 1.0%.

[0063] Chromium increases the hardenability, hardness, and wear resistance of steel; molybdenum improves the hardenability and hot strength of steel; boron improves the hardenability of steel. These three elements are beneficial for improving the hardenability of welds, but they are all elements that shrink the austenite phase region, and their content in the weld should be strictly controlled: Cr ≤ 1.4%, B ≤ 0.25%, and Mo ≤ 2.1%. In some embodiments, the Cr content in the weld is ≤ 1.1%. In some embodiments, the Cr content in the weld is ≤ 0.8%. In some embodiments, the Cr content in the weld is not less than 0.05%, such as 0.05-1.4%. In some embodiments, the B content in the weld is ≤ 0.15%. In some embodiments, the B content in the weld is not less than 0.001%, such as 0.001-0.25%. In some embodiments, the Mo content in the weld is ≤ 1.5%. In some embodiments, the Mo content in the weld is not less than 0.05%, such as 0.05-2.1%.

[0064] Titanium, zirconium, niobium, and vanadium are all carbide-forming elements. Titanium is one of the strong ferrite-forming elements, narrowing the austenite phase region; solid-solution titanium can improve the hardenability of steel, while the presence of TiC particles reduces the hardenability of steel; zirconium is a rare metal that acts as a purifier in the molten pool, removing oxygen, nitrogen, sulfur, and phosphorus, and can refine austenite grains in steel; niobium can refine the microstructure, improving the formability and fracture resistance of steel; vanadium improves the strength, toughness, and plasticity of steel. According to the inventors' research, if the weld contains titanium, zirconium, niobium, and vanadium, the weight percentage of each element should be controlled as follows: Ti ≤ 0.95%, V ≤ 0.85%, Zr ≤ 0.45%, and Nb ≤ 3.4%. In some embodiments, the Ti content in the weld is 0.01-0.95%. In some embodiments, the V content in the weld is 0.01-0.85%. In some embodiments, the Zr content in the weld is ≤ 0.20%. In some embodiments, the Nb content in the weld is ≤1.5%. In some embodiments, the Nb content in the weld is ≤1.0%. In some embodiments, the Nb content in the weld is ≤0.50%. In some embodiments, the Nb content in the weld is ≥0.01%, such as 0.01-3.4%.

[0065] The width of the weld is 0.7-2.0 mm.

[0066] A second aspect of the present invention provides a welding wire for preparing the above-mentioned welded components, comprising, by weight percentage: 0.16% <C≤0.39%,0.2%≤Si≤1.4%,0.8%≤Mn≤2.0%,3.0%<Ni≤8.0%,0.06%<Al≤1.5%,P≤0.015%,S≤0.008%。

[0067] In some embodiments, the welding wire further includes at least one of Co, Cu, Cr, Ti, V, Mo, Nb, Zr, and B; Cu ≤ 2.0%, Cr ≤ 2.0%, Ti ≤ 2.0%, V ≤ 2.0%, Zr ≤ 1.0%, B ≤ 0.5%, Co + Cu ≤ 6.0%, Cr + Mo + B ≤ 5.0%, and Ti + Zr + Nb + V ≤ 8.0%. In some embodiments, the Co content in the welding wire is ≤ 5.0%. In some embodiments, the Mo content in the welding wire is ≤ 3.3%. In some embodiments, the Nb content in the welding wire is ≤ 5.65%.

[0068] In some embodiments, the welding wire also includes Mo and Cr.

[0069] Preferably, the welding wire composition contains 0.161 wt% ≤ C ≤ 0.25 wt%; and / or 1.0% ≤ Mn ≤ 1.95%; and / or 3.05% ≤ Ni ≤ 4.95%.

[0070] In some implementations, the Si content in the welding wire is 0.2-0.6% or 0.6-1.4%.

[0071] In some embodiments, the Al content in the welding wire is 0.07-1.5%. In some embodiments, the Al content in the welding wire is 0.12-1.5%. In some embodiments, the Al content in the welding wire is 0.20-1.20%.

[0072] It should be noted that the welding wire contains iron and unavoidable impurities.

[0073] Optionally, the diameter of the welding wire is 0.8-1.6 mm.

[0074] A third aspect of the present invention provides a method for manufacturing a welded component, comprising: using the welding wire of the present invention, welding at least two steel plates to be welded together by laser filler wire welding or laser MAG composite welding.

[0075] In the preparation of welded components, this invention, on the one hand, expands the elements in the austenite phase region to compress the high-temperature ferrite region, preventing excessive ferrite precipitation in the weld before the hot stamping die closes, thereby improving the weld strength; on the other hand, by controlling the hardenability of the weld composition, the conversion rate of martensite is ensured, ensuring that the weld microstructure of the hot stamping component is composed of martensite and diffusely distributed acicular ferrite, with the weld ferrite having an average diameter of no more than 15 μm and an average length of no more than 80 μm.

[0076] In some embodiments, the parameters for laser wire feed welding include: a welding heat input of 20-250 J / mm and a wire feed speed of 2-18 m / min. In some embodiments, the wire feed speed is 2-12 m / min.

[0077] In some implementations, the diameter of the welding wire is 0.8-1.6 mm.

[0078] In some implementations, the parameters of the laser MAG composite welding include: laser heat source line energy of 5-40 J / mm, arc heat source line energy of 8-27 J / mm, and wire feed speed of 2.5-30 m / min.

[0079] The linear energy of the laser heat source is calculated according to Equation 1; the linear energy of the electric arc heat source is calculated according to Equation 2.

[0080] Where q is the linear energy, in J / mm; η is the power efficiency coefficient, which is 0.8 in this invention; P is the actual output power of the heat source, in J; U is the voltage, in V; I is the current, in A; and v is the welding speed, in mm / s.

[0081] It should be noted that during welding, the shielding gas is a mixture of argon and carbon dioxide, with carbon dioxide accounting for 10-50 vol.% by volume; preferably, the volume percentage of carbon dioxide in the shielding gas is 10-30 vol%. The flow rate of the shielding gas is 10-25 L / min. Using argon and carbon dioxide as shielding gases during welding enhances the activity of the shielding gas in the welding zone, which is beneficial for increasing the penetration rate of the base metal and the fluidity of the molten metal in the weld pool, improving the compositional uniformity of the weld pool, preventing aluminum segregation, ensuring uniform weld composition, and avoiding banded structures caused by compositional inhomogeneity.

[0082] Before and during welding, the coating of the steel plates to be welded shall not be thinned or removed; the butt joint gap between the two steel plates to be welded shall be 0.2-0.6 mm.

[0083] The steel plate to be welded includes a steel plate substrate, the tensile strength of which after hot stamping is 500-2100 MPa. It should be noted that the hot stamping process involves: first heating at 940-960℃ for 2-10 minutes, then transferring to a water-cooled mold for hot stamping. This process takes no more than 10 seconds, the cooling rate within the water-cooled mold is no less than 35℃ / s, and the holding time is at least 10 seconds. In some embodiments, the furnace heating time for the welded parts is 4-6 minutes. In some embodiments, the substrate and coating of the steel plate to be welded are as described in any of the preceding embodiments.

[0084] After welding, a hot stamping step is included before obtaining the welded component. Specifically, the welded component is first heated in a furnace at 940-960°C for 2-10 minutes, then rapidly transferred to a water-cooled mold for hot stamping. The time from leaving the furnace to the complete closure of the stamping mold is no more than 10 seconds, the cooling rate inside the mold is no less than 35°C / s, and the pressure is held for at least 10 seconds. In some embodiments, the furnace heating time is 4-6 minutes. In some embodiments, the cooling rate inside the mold is 35-50°C / s. In some embodiments, the pressure holding time inside the mold is 10-15 seconds.

[0085] Example 1

[0086] This embodiment provides a method for manufacturing welded components, including the following steps:

[0087] (1) Prepare steel plates 1 and 2 to be welded; steel plate 1 has a strength grade of 2000MPa and a thickness of 1.4mm. Steel plate 1 includes a steel plate substrate and a coating on the upper and lower surfaces of the steel plate substrate. The components and contents of the steel plate substrate are shown in Table 1, and the nominal coating weight of the steel plate to be welded is shown in Table 4. Steel plate 2 has a strength grade of 2000MPa and a thickness of 1.4mm. Steel plate 2 includes a steel plate substrate and a coating on the upper and lower surfaces of the steel plate substrate. The components and contents of the steel plate substrate are shown in Table 2, and the nominal coating weight of the steel plate to be welded is shown in Table 4. Clean the surfaces of steel plates 1 and 2 to remove oil stains, water stains, and other contaminants. The coatings of steel plates 1 and 2 include 9.1wt% Si, 2.3wt% Fe, and the balance being aluminum and unavoidable impurities.

[0088] (2) The butt gap between the two steel plates to be welded is set to 0.43 mm. Laser filler wire welding is used for welding. The composition of the welding wire is shown in Table 3. The welding line energy is 85 J / mm, the wire feeding speed is 5 m / min, the welding wire diameter is 1.2 mm, the shielding gas is 60 vol.% Ar + 40 vol.% CO2, and the gas flow rate is 20 L / min.

[0089] (3) Hot stamping after welding: The welded parts obtained in step (2) are hot stamped and quenched. They are placed in a heating furnace at a temperature of 940℃ and heated for 5 minutes. Then, the welded parts are quickly transferred to a water-cooled mold for hot stamping. The time from when the welded parts leave the heating furnace to when the stamping mold is completely closed is 10 seconds. The cooling rate of the welded parts inside the mold is 35℃ / s. The pressure is held for 10 seconds to obtain the welded parts. The composition of the weld seam of the welded parts is shown in Table 5.

[0090] Figure 1 shows the quasi-static tensile curve of the welded joint of the welded component in this embodiment, including three parallel specimens, denoted as specimens 1 to 3. Figure 1 shows that the elongation of the joint is greater than 4%, and the joint strength meets the requirements of the automotive industry. Figure 2 shows the specimen after tensile fracture of the welded joint of the welded component in this embodiment. The fracture location is in the base material. Figure 3 is the metallographic image of the welded joint of the welded component; no banded structure is observed. Figure 4 is the metallographic image of the weld seam of the welded component; the weld seam structure consists of martensite and a small amount of dispersed acicular ferrite. Figure 5 shows the hardness distribution of the welded joint; the weld seam hardness is well consistent with the base material hardness. During the preparation of the welded component, the welded part is first austenitized, and the atoms in the coating and the substrate expand into each other, forming a thicker intermetallic compound layer. This layer has high melting point and high hardness, preventing the steel substrate from being oxidized and decarburized during the heating and pressure holding stages.

[0091] Example 2-18

[0092] Examples 2-18 provide welded components and their manufacturing methods. The steps are similar to those in Example 1, except that the parameters of the steel plate to be welded, the welding wire parameters, the welding parameters, and the weld composition are different, as shown in Tables 1-5.

[0093] Examples 19-20

[0094] Examples 19-20 provide welded components and their manufacturing methods. The steps are similar to those in Example 1, except that laser MAG composite welding is used. The parameters of the steel plate to be welded, the welding wire parameters, the welding parameters, and the weld composition are different, as shown in Tables 1-5.

[0095] Comparative Examples 1-5

[0096] Comparative Examples 1-5 provide welded components and their manufacturing methods. The steps are similar to those in Example 1, except that the parameters of the steel plate to be welded, the welding wire parameters, the welding parameters, and the weld composition are different, as shown in Tables 1-5.

[0097] Figure 6 is a metallographic image of the weld of the welded component in Comparative Example 3. The average length of the ferrite in the image is 83.5 μm, the average diameter is 16.43 μm, and the volume percentage of ferrite in the weld is 15.5%. The corresponding quasi-static tensile strength of the welded joint is 1593 MPa, the elongation is 1.9%, and the fracture location is the weld.

[0098] Test Results

[0099] The carbon and sulfur content in the weld was determined by infrared absorption method, according to the standard GB / T 20123-2006, "Determination of Total Carbon and Sulfur Content in Steels - Infrared Absorption Method after Combustion in a High-Frequency Induction Furnace" (conventional method). The content of other components in the weld was measured using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0100] Table 6 shows the weld width, average ferrite diameter, average ferrite length, ferrite volume percentage in the weld, tensile strength, elongation, and fracture location of the welded components in Examples 1-20 and Comparative Examples 1-5. The test method for the ferrite volume percentage in the weld was performed according to the standard "GB T 18876.1-2002 Standard Test Methods for Determination of Metallographic Structure, Inclusion Content and Grade in Steel and Other Metals by Automated Image Analysis Part 1 Steel and Other Metals".

[0101] Method for measuring the average length and average diameter of ferrite in the weld: On the metallographic section of the same weld joint perpendicular to the welding direction, under a metallographic microscope with a magnification of 500x, six non-overlapping metallographic fields of view of the weld are randomly selected and metallographic images are taken. Then, the length and width of all ferrite in each metallographic image are actually measured and recorded. Finally, the average value of the ferrite length and width in the measurement results is calculated. This average value is the average length and average diameter of ferrite in the weld.

[0102] Test methods for tensile strength and elongation: Standard tensile specimens are used, with a nominal width of 12.5 mm and an original gauge length of 50 mm; refer to the standard "GB / T228.1-2010 Metallic materials, tensile testing - Part 1: Test method at room temperature".

[0103] According to the experimental results in Table 6, when the weld joint includes acicular ferrite and martensite, with the average length of the acicular ferrite not exceeding 80 μm and the average diameter not exceeding 15 μm, and the volume fraction of ferrite in the weld being 0.1-10%, the fracture location of the welded component is in the base material, not at the weld joint. Referring to Examples 11-13, when the average diameter of the ferrite is not greater than 10 μm and the average length of the acicular ferrite is not greater than 50 μm, the elongation of the joint can be further improved. This invention, by controlling the length and diameter of the ferrite in the weld joint, helps to improve the strength and elongation of the welded component joint.

[0104] In conjunction with Examples 11-13, it can also be shown that when the weld composition satisfies 0.08%≤C≤0.37%, 0.6%≤Mn≤2.8%, and 0.6%≤Ni<2.0%, the diameter and length of ferrite can be further optimized to improve the elongation of the joint.

[0105] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A welded component, characterized in that, The welded component includes a welded joint, and the microstructure of the weld seam of the welded joint includes acicular ferrite and martensite. The average length of the acicular ferrite is not greater than 80 μm and the average diameter is not greater than 15 μm. The volume percentage of acicular ferrite in the weld seam is 0.1-10%.

2. The welded component according to claim 1, characterized in that, The weld, by weight percentage, comprises 0.08% ≤ C ≤ 0.45%, 0.05% ≤ Si ≤ 1.1%, 0.5% ≤ Mn ≤ 4.4%, P ≤ 0.015%, S ≤ 0.01%, 0.01% ≤ Al ≤ 1.5%, 0.5% ≤ Ni ≤ 3.5%, Cr ≤ 1.4%, Co ≤ 1.6%, Nb ≤ 3.4%, Ti ≤ 0.95%, V ≤ 0.85%, Cu ≤ 0.8%, Mo ≤ 2.1%, Zr ≤ 0.45%, B ≤ 0.25%, with the balance being Fe and unavoidable impurities.

3. The welded component according to claim 2, characterized in that, The weld seam comprises 0.08% ≤ C ≤ 0.37%, and / or 0.6% ≤ Mn ≤ 2.8%, and / or 0.6% ≤ Ni < 2.0%.

4. The welded component according to claim 2 or 3, characterized in that, The elemental composition of the weld seam satisfies any one or more of the following: The Si content is 0.20-1.1% or 0.50-1.1%; The Al content is 0.3-1.5% or 0.6-1.3%; The Cu content is ≤0.5%; The content of Co is ≤1.0%; The Cr content is ≤1.1%, or the Cr content is ≤0.8%; The Cr content is not less than 0.05%; The content of B is ≤0.15%; The content of B is not less than 0.001%; The content of Mo is ≤1.5%; The content of Mo is not less than 0.05%; The Ti content is 0.01-0.95%; The content of V is 0.01-0.85%; The Zr content is ≤0.20%; The Nb content is ≤1.5%, or ≤1.0%, or ≤0.50%; The Nb content is above 0.01%.

5. The welded component according to claim 1, characterized in that: The average diameter of the acicular ferrite is not greater than 10 μm; and / or the average length of the acicular ferrite is not greater than 50 μm.

6. The welded component according to claim 1, characterized in that, The width of the weld is 0.7-2.0 mm.

7. The welded component according to claim 1, characterized in that, The welded component includes at least two steel plates welded together via the weld joint, wherein the steel plate includes a steel plate substrate and an aluminum-containing or aluminum alloy coating disposed on at least one surface of the steel plate substrate; Preferably, the tensile strength of the steel plate matrix after hot stamping is 500-2100 MPa, and more preferably 1700-2100 MPa; Preferably, the thickness of the steel plate substrate of each steel plate is 0.5-4 mm; Preferably, by weight percentage, the coating composition of each steel plate includes 5wt%≤Si≤11wt%, 0≤Fe≤4wt%, with the balance being aluminum and unavoidable impurities; Preferably, the weight of each plating layer is 5-140 g / m 2 , preferably 30-100 g / m 2 ; Preferably, the composition of the steel plate matrix of each steel plate includes: 0.06%≤C≤0.50%, 0.01%≤Si≤1.0%, 0.5%≤Mn≤5.0%, P≤0.015%, S≤0.01%, 0.01%≤Al≤0.3%, Cr≤1.0%, Nb≤0.2%, V≤0.1%, Ti≤0.2%, Mo≤0.5%, Ni≤0.5%, B≤0.08%, N≤0.006%, with the balance being Fe and unavoidable impurities; Preferably, the composition of the steel plate matrix of each steel plate includes: 0.20%≤C≤0.45%, 0.05%≤Si≤1.0%, 0.5%≤Mn≤3.0%, P≤0.015%, S≤0.01%, 0.01%≤Al≤0.3%, Cr≤1.0%, Nb≤0.2%, V≤0.1%, Ti≤0.2%, Mo≤0.5%, Ni≤0.5%, B≤0.08%, N≤0.006%, with the balance being Fe and unavoidable impurities; Preferably, the composition of the steel plate matrix of each steel plate includes: 0.30%≤C≤0.40%, 0.05%≤Si≤1.0%, 0.5%≤Mn≤2.0%, P≤0.015%, S≤0.01%, 0.01%≤Al≤0.3%, Cr≤1.0%, Nb≤0.2%, V≤0.1%, Ti≤0.2%, Mo≤0.5%, Ni≤0.5%, B≤0.08%, N≤0.006%, with the balance being Fe and unavoidable impurities.

8. A welding wire for preparing the welded components according to any one of claims 1-7, characterized in that, By weight percentage, including: 0.16% <C≤0.39%,0.2%≤Si≤1.4%,0.8%≤Mn≤2.0%,3.0%<Ni≤8.0%,0.06%<Al≤1.5%,P≤0.015%,S≤0.008%; Preferably, the welding wire further comprises at least one of Co, Cu, Cr, Ti, V, Mo, Nb, Zr, and B; preferably, Cu≤2.0%, Cr≤2.0%, Ti≤2.0%, V≤2.0%, Zr≤1.0%, B≤0.5%, Co+Cu≤6.0%, Cr+Mo+B≤5.0%, Ti+Zr+Nb+V≤8.0%; preferably, the Mo content is ≤3.3%, and the Nb content is ≤5.65%. Preferably, the welding wire further includes Mo and Cr.

9. The welding wire according to claim 8, characterized in that, The welding wire comprises 0.161wt% ≤ C ≤ 0.25wt%; and / or 1.0% ≤ Mn ≤ 1.95%; and / or 3.05% ≤ Ni ≤ 4.95%.

10. The welding wire according to any one of claims 8-9, characterized in that, The welding wire includes one or more of the following characteristics: The Si content is 0.2-0.6% or 0.6-1.4%. The Al content is 0.07-1.5%, 0.12-1.5%, or 0.20-1.20%; The balance consists of iron and unavoidable impurities.

11. A method for manufacturing a welded component according to any one of claims 1-7, characterized in that, include: Using the welding wire described in any one of claims 8-10, at least two steel plates to be welded are welded together by laser filler wire welding or laser MAG composite welding.

12. The manufacturing method according to claim 11, characterized in that: The parameters for laser wire filler welding are: linear energy of 20-250 J / mm, and wire feed speed of 2-18 m / min; or The parameters for the laser-MAG composite welding are as follows: the linear energy of the laser heat source is 5-40 J / mm, the linear energy of the arc heat source is 8-27 J / mm, and the wire feed speed is 2.5-30 m / min.

13. The manufacturing method according to any one of claims 11-12, characterized in that: The diameter of the welding wire is 0.8-1.6mm; Before and during welding, the coating on the steel plate to be welded shall not be thinned or removed; and / or The butt joint gap between the two steel plates to be welded is 0.2-0.6mm.

14. The manufacturing method according to claim 11, characterized in that, During welding, the shielding gas is a mixture of argon and carbon dioxide, wherein the volume percentage of carbon dioxide is 10-50 vol.%; preferably, the volume percentage of carbon dioxide in the shielding gas is 10-30 vol%.; preferably, the flow rate of the shielding gas is 10-25 L / min.

15. The manufacturing method according to claim 11, characterized in that, Before obtaining the welded parts, a hot stamping step is also included, specifically: the welded parts are first heated in a heating furnace at 940-960℃ for 2-10 minutes, and then quickly transferred to a water-cooled mold for hot stamping; wherein, the time from leaving the heating furnace to the complete closure of the stamping mold is no more than 10 seconds, the cooling rate inside the mold is no less than 35℃ / s, and the pressure is held for at least 10 seconds.

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