Hot stamped component and laser tailor-welded pre-coated steel plate

Abstract

The present invention relates to a hot stamped component formed by hot stamping a laser tailor-welded component. The present invention further relates to a laser tailor-welded component obtained by performing laser tailor-welding on a pre-coated steel plate, a method for forming the laser tailor-welded component, and a welding wire suitable for laser tailor-welding.

Description

Hot stamping components and laser welded pre-coated steel plates Technical Field

[0001] The present invention relates to a laser-welded component obtained by laser welding pre-plated steel sheets, wherein the pre-plated steel sheets are pre-plated steel sheets for hot stamping and have an aluminum or aluminum alloy pre-plated layer, and a hot stamped component made therefrom. The present invention also relates to a method for forming the laser-welded component. Background Art

[0002] In recent years, with the urgent need for energy conservation and environmental protection and the improvement of safety requirements, automobile lightweighting and safety have become the general pursuit of the automotive manufacturing industry, and high-strength steel has received more and more attention in the field. As the material category with the highest strength among automotive steels, the proportion of hot stamping steel used in automotive materials has increased year by year. If bare plates are used for hot stamping, surface oxidation of the steel plates will inevitably occur, which will affect the surface quality of the mold, the quality of parts, and the subsequent automobile assembly and painting processes. The use of hot stamping steel plates with pre-plating can effectively avoid oxidation and decarburization of the steel plate surface, while improving the corrosion resistance of the steel plate. Among the pre-plated hot stamping steel products developed at home and abroad, aluminum silicon (Al-Si) pre-plated hot stamping steel is the most widely used.

[0003] In automotive manufacturing, laser welding can join steel plates of varying thicknesses, materials, and even surface finishes. This method places the required material where it's needed, optimizing cost, weight, and safety. Hot stamping the laser-welded sheets can reduce weight while reducing the number of body parts, improving manufacturing precision while also enhancing crashworthiness, further enhancing the lightweighting effect.

[0004] To achieve maximum lightweighting while meeting increasingly stringent crash requirements, various tailor-welded components have emerged. These components can be welded not only from materials of uniform strength and thickness (e.g., steel plates), but also from a combination of materials with varying strengths (e.g., tensile strengths of 500 MPa, 1000 MPa, 1500 MPa, and 2000 MPa, for example) and thicknesses. However, existing laser welding of pre-coated aluminum or aluminum alloy plates of varying strength levels to create tailor-welded components presents the following challenges.

[0005] Question 1: The initial pre-plating layer on the surface of aluminum or aluminum alloy pre-plated steel plates may have an adverse effect on the quality of the weld. This is because the pre-plating layer (especially the Al-Si pre-plating layer) will melt into the weld during the welding process, causing the following defects in the weld: intermetallic compound areas will form in areas with relatively high aluminum content, which have high brittleness after hot stamping, and therefore easily induce cracks during the service of the weld, accelerating the failure of the weld; ferrite will form in areas with relatively low aluminum content, making it impossible for the weld structure to be completely austenitized during the hot stamping process, and then a dual-phase structure of martensite and ferrite will be produced after the hot stamping process. Therefore, areas of different mechanical strength will be formed in the weld, affecting the mechanical properties of the weld.

[0006] Problem 2: When welding materials of different strength levels or thicknesses together, the weld is prone to failure during service. This is because the materials of different strength levels have varying compositions. The weld formed after laser welding is a blend of the different materials on either side, resulting in different physical properties. This makes the weld the weakest area and, after hot stamping, the first to fail during service.

[0007] Problem 3: Existing welding wires are difficult to weld with a variety of material combinations. In actual engineering applications, gaps between the welded surfaces can be formed by using filler wire welding to ensure weld formation. Existing welding wires are generally only suitable for a specific material combination and cannot achieve good results in laser welding of steel plates with multiple strength levels and thickness specifications.

[0008] Problem 4: High-strength welds often lack toughness, presenting a greater risk of hydrogen-induced delayed cracking. For example, 2000MPa-grade materials, due to the high carbon content in the base material, produce a high hardenability martensite after hot forming, resulting in a more significant risk of delayed cracking. Therefore, when laser welding 2000MPa-grade materials, attention should be paid to minimizing the risk of delayed cracking while ensuring weld strength.

[0009] In order to solve some of the above problems, there have been certain attempts in the prior art. For example, one method proposes to strip the pre-plating layer near the welding area before welding to reduce the content of Al entering the weld and ensure that the ferrite content in the weld is as low as possible. However, this method requires an additional stripping step, which has certain disadvantages in production cost and product stability, and is not helpful in improving the toughness of the weld. Another method uses laser wire welding to improve the weld characteristics by melting a welding wire of a specific composition into the weld. However, existing laser wire welding methods and products have many shortcomings.

[0010] For example, CN104023899A is concerned that the aluminum in the pre-plating layer may enter the welding area during laser welding, thereby causing the physical properties of the welding area to deteriorate. It proposes to neutralize the effect of the aluminum in the pre-plating layer by adding high-carbon, high-manganese welding wire, thereby ensuring that the weld area can obtain a fully austenitic structure during the hot stamping heating process. However, it was found in production and use that high-carbon, high-manganese welding wire is difficult to produce and difficult to draw. At the same time, when welding high-strength hot stamping steel with a high carbon content (for example, greater than 0.3wt.%), the addition of high-carbon, high-manganese welding wire will result in poor toughness of the final weld and a greater risk of delayed cracking.

[0011] CN111215751A provides a steel differential strength welded component with an aluminum or aluminum alloy pre-plated layer, which is formed by butt-welding a high-strength steel plate with a tensile strength of 1300MPa-1700MPa after hot stamping and a low-strength steel plate with a tensile strength of 400MPa-700MPa after hot stamping. During welding, the weld butt gap between the two steel plates to be welded needs to be maintained at 0.2-0.5mm, which places high demands on the sheet material processing accuracy and positioning accuracy. On the other hand, the technology of this document can only solve the problem of butt-welding two specific levels of hot stamping steel (i.e., 400-700MPa and 1300-1700MPa), while actual industrial production often involves welding a variety of steel plates of different thicknesses and strengths. The technical solution provided by this document cannot meet production needs.

[0012] Similarly, CN111230301A provides a method for manufacturing equal-strength components by welding steel sheets with aluminum or aluminum alloy pre-plating, in which equal-strength steel plates with aluminum or aluminum alloy pre-plating are welded by a process of reserving a gap and adding a filler wire welding. However, this technology requires that the butt gap between the two steel plates to be welded be preset to 0.2-0.5mm, which places high demands on the sheet material processing accuracy and positioning accuracy. On the other hand, the technology of this document can only solve the problem of welding equal-strength components, while actual industrial production often involves welding a variety of combinations of steel plates with different thicknesses and strengths. The technical solution provided by this document cannot meet production needs.

[0013] CN111432975A provides a laser wire welding method for coated plates with aluminum or aluminum alloy pre-plating. It introduces the concept of a weld joint quenching factor and obtains a weld joint with high hardenability by adding high-alloy welding wire, thereby ensuring the strength of the weld joint. However, although this technology improves the hardenability of the weld joint by adding a certain amount of Ni to the weld, and can ensure that the weld obtains a fully martensitic structure after hot stamping, it does not take into account the hardenability of the weld joint. For some special welding combinations (such as welding of differentially thick plates, where the yield strength of the substrate on the thick plate side is lower after hot stamping and the yield strength of the substrate on the thin plate side is higher after hot stamping), in order to ensure that the weld joint performance of the final hot stamped component is better than that of the substrate, it is necessary to ensure that the hardenability of some areas of the weld joint is higher than that of the substrate. The technology in this document cannot achieve this.

[0014] Therefore, there is a need in this field to achieve high-quality laser welding of various combinations of 1000-2000 MPa grade hot stamping steels commonly used on the market (including equal strength, unequal strength, equal thickness, and unequal thickness combinations) at a relatively low cost, with high weld strength, good toughness, and strong resistance to hydrogen-induced delayed cracking.

[0015] Summary of the Invention

[0016] The present invention aims to provide an improved hot stamping component, which is formed by hot stamping a laser-welded component, and can overcome the problems described above. The present invention aims to provide a laser-welded component suitable for hot stamping, which can overcome the problems described above and meet industrial needs.

[0017] The present invention also aims to provide an advantageous manufacturing method of the improved laser-welded component and an advantageous welding wire composition.

[0018] One of the focuses of the present invention is to achieve high-quality laser tailor welding of various combinations of hot stamping steel materials with aluminum or aluminum alloy pre-plating layers (involving various tensile strength levels and various thickness specifications).

[0019] Another focus of the present invention is to achieve the above-mentioned high-quality laser welding with low cost and simplified process.

[0020] Another focus of the present invention is to provide an improved laser welding wire that can achieve good weld quality across a wide range of strength and thickness combinations for the steel plates being welded. Furthermore, the wire is highly adaptable to a wide range of variations in the gap between the steel plates, demonstrating its versatility.

[0021] To achieve excellent performance in hot-stamped components, or to meet the requirements for high-quality laser welding, welds (also known as welded joints) must possess both excellent strength and excellent resistance to hydrogen-induced delayed cracking: under tension, fracture occurs in the base material (i.e., the welded steel sheet) rather than the weld; and the weld's resistance to hydrogen-induced delayed cracking must be at least as strong as that of the base material. To achieve such high-quality welds, the inventors of the present invention, through intensive research, have made the following discoveries regarding laser welding of hot-stamped steel sheets pre-coated with aluminum or aluminum alloys (particularly aluminum-silicon pre-coatings).

[0022] First, in order to meet the high strength requirements of the weld, the weld and the base material must meet a specific relationship.

[0023] For welding substrates with the same tensile strength level, in order to prevent fracture in the weld during stretching, it is necessary to ensure that the average hardness of the weld after hot stamping is not lower than the average hardness of the substrate, that is, HV 焊缝 ≥HV 基材 .

[0024] For welding two substrates with different tensile strength levels, the inventors found that the deformation resistance of the weld and the work hardening capacity of the substrates on both sides can be comprehensively considered in the following two situations:

[0025] Case 1: The welded base materials satisfy: T1×YS1≥0.9×T2×YS2, where YS1<YS2, where YS1 and YS2 are the yield strengths of the first base material and the second base material after hot stamping, respectively, and T1 and T2 are the thicknesses of the first base material and the second base material, respectively.

[0026] In the absence of filler wire, even if the influence of aluminum is eliminated in the weld, the weld is still a weak point in this welding combination. This is because the two materials with different yield strengths have certain differences in composition, the most obvious of which is the difference in C content. The weld composition is a mixture of the two base materials. Theoretically, the yield strength of the weld YS w Greater than YS1 and less than YS2. Since the weld is a gradual transition from the thick side to the thin side of the plate, there must be a part of the weld edge near the second base material that meets T w ×YS w <T2×YS2(T w is the thickness of the weld area), if the deformation resistance of the weld area (T w ×YS w ) is at its lowest, that is: T w ×YS w<T2×YS2<T1×YS1, the weld will first undergo plastic deformation and then fail. But in fact, the final fracture position is also related to the work hardening ability of the material. Research has found that due to the different work hardening abilities of the substrates on both sides, the risk of weld fracture does not only exist when T2×YS2<T1×YS1 is met. When 0.9T2×YS2≤T1×YS1 (the deformation resistance of the first substrate is slightly lower than that of the second substrate), during the tensile process, the area within 0.2mm from the weld edge on the side of the substrate with higher yield strength in the weld is prone to plastic deformation first, causing the weld to fail first. Therefore, it is necessary to fill the weld with a certain amount of welding wire containing C and Mn to improve the strength of the weld, and ensure that at least the average hardness of the weld within 0.2mm from the weld edge on the side with high yield strength material is greater than the average hardness of the material with high yield strength. That is, in this case, it is necessary to ensure the weld hardness characteristics: HV 焊缝0.2 ≥HV 高强度基材 , where HV 焊缝0.2 It refers to the hardness value within 0.2mm from the weld fusion line on the side of the high yield strength substrate after hot stamping.

[0027] Case 2: The base materials to be welded meet the following conditions: T1×YS1<0.9×T2×YS2, where YS1<YS2, YS1 and YS2 are the yield strengths of the first and second base materials after hot stamping, respectively, and T1 and T2 are the thicknesses of the first and second base materials, respectively. In this case, HV 焊缝 ≥HV 低强度基材 That is, after hot stamping, the average hardness of the weld is not less than the average hardness of the low yield strength substrate, which can ensure that it breaks from the substrate during stretching.

[0028] Secondly, the prior art generally believes that the aluminum from the pre-plating layer of the aluminum-silicon pre-plated steel sheet will have an adverse effect on the performance of the weld. Therefore, either the aluminum content entering the weld is reduced as much as possible (for example, by partially stripping the pre-plating layer to achieve this), or, if the weld has a high aluminum content, the adverse consequences of the high aluminum content on the weld strength are alleviated by using high-alloy welding wire. Unlike the prior art, the inventors of the present invention have discovered that, if the weld alloy composition is appropriate, the presence of a small amount of aluminum (0.3wt.%≤Al≤1.0wt.%) in the weld not only does not have a significant negative impact on the strength of the weld, but also helps to improve the weld's resistance to hydrogen-induced delayed cracking, thereby achieving a balance between weld strength and weld toughness and resistance to hydrogen-induced delayed cracking.

[0029] Specifically, to improve weld strength, carbon and manganese can be added to the weld. However, increased carbon and manganese content can easily lead to weld hardness and brittleness, increasing the risk of hydrogen-induced delayed cracking. The inventors of the present invention have discovered that the inclusion of an appropriate amount of aluminum in the weld can reduce the weld hardness and brittleness caused by high carbon and manganese content and improve the weld's resistance to hydrogen-induced delayed cracking. A detailed analysis is provided below.

[0030] Martensite is produced by austenite through shear deformation. That is, austenite based on a face-centered cubic structure directly transforms into martensite with a body-centered cubic structure through shear deformation. There are two common deformation mechanisms for metallic materials: dislocation slip and twinning. The actual martensitic phase transformation mechanism that occurs is related to the strength of the austenite during the phase transformation (the difficulty of plastic deformation). If the austenite strength is low, plastic deformation is easy to occur, and the phase transformation is achieved by deformation through dislocation slip. If the austenite strength is high, plastic deformation is difficult to occur, and the phase transformation can only be achieved by deformation through twinning. Dislocation martensite has a higher dislocation density and less crystal structure distortion (it still maintains a BCC structure because more carbon atoms can be accommodated along the dislocation lines). Therefore, dislocation martensite has good work hardening ability and thus high toughness. Twinned martensite, on the other hand, has a lower dislocation density and a more distorted crystal structure (its low dislocation density allows carbon atoms to be supersaturated and dissolved in the BCC structure, which can only dissolve a higher amount of carbon atoms by distorting into the BCT structure). This low dislocation density is not conducive to work hardening, and dislocations in the non-three-dimensionally symmetrical BCT crystal structure cannot slip, so twinned martensite reduces martensite toughness. The overall toughness of martensite is primarily determined by the content of twinned martensite.

[0031] To meet the weld strength requirements for tailor-welding 2000MPa-grade aluminum or aluminum alloy pre-coated steel sheets (as mentioned above, the weld strength must be greater than that of the base material), the C and Mn contents in the weld martensite can be increased to ensure a fully martensitic structure after hot stamping, thereby improving martensite strength. However, increasing the C and Mn contents significantly exacerbates the formation of twinned martensite, which tends to increase weld strength while decreasing weld toughness and resistance to hydrogen-induced cracking.

[0032] According to the present invention, weld toughening can be achieved by including a small amount of Al in the weld alloy composition. In the body-centered cubic crystal structure of martensite, Al atoms can serve as replacement atoms to occupy the positions of the original Fe atoms. Due to the large volume of Al atoms (the Al atomic radius is approximately 0.1434nm, and the Fe atomic radius is approximately 0.1241nm), Al replacing Fe in the solid solution will cause the body-centered cubic lattice to expand, increasing the original atomic interstices, allowing more interstitial solid solution carbon atoms to be accommodated in the BCC. This reduces the BCC squareness caused by carbon atom supersaturation and elongates it to BCT, resulting in limited dislocation slip. The Al element increases the martensitic phase transition temperature, and due to lattice expansion, the interstitial solid solution strengthening effect of carbon atoms is reduced. Both of these factors lead to a decrease in austenite strength during phase transition, thereby promoting the formation of dislocation martensite and inhibiting or reducing the formation of twinned martensite. In this way, the weld toughness can be improved.

[0033] The inventors have found through research that when the Al content in the weld is greater than 0.3wt.%, the resistance of the weld to hydrogen-induced delayed cracking is significantly improved.

[0034] Therefore, while appropriately increasing the C content and Mn content to achieve micro-strengthening of the weld, the weld can be toughened by introducing an appropriate Al content to improve resistance to hydrogen-induced delayed cracking. This can resolve the contradiction between the strength and toughness of the weld and obtain a weld with both excellent strength and toughness.

[0035] Building on this understanding, the present invention proposes incorporating appropriate carbon and manganese content into the weld alloy, along with appropriate aluminum content, to achieve a synergistic effect and achieve stable, excellent weld performance. In other words, the present invention innovatively proposes achieving both "micro-strengthening and weld toughening" through specific carbon, manganese, and aluminum content in the weld.

[0036] Accordingly, the present invention proposes an evaluation factor FA to assist in determining whether the weld alloy composition is conducive to achieving excellent weld performance. The evaluation factor FA can be obtained by calculating the average content of manganese, carbon, and aluminum in the weld in terms of weight percentage. 焊缝 、C 焊缝 、Al 焊缝 It is concluded that FA = 10Mn 焊缝 +77C 焊缝 -1900Al 焊缝 2 -12Al 焊缝 This evaluation factor can reflect the impact of the multiple effects of manganese, carbon, and aluminum on weld performance, particularly its resistance to hydrogen-induced delayed cracking. For different welding scenarios, the evaluation factor FA needs to be controlled within the corresponding range proposed by this invention.

[0037] The optimal alloy composition of the weld seam is related to the carbon content or the tensile strength grade of the steel to be welded. As is well known, there is usually a rough corresponding relationship between the carbon content of steel and its tensile strength grade as follows:

[0038] A carbon content of 0.27 wt.% < C ≤ 0.38 wt.% (especially 0.28 - 0.38 wt.%) usually corresponds to steel of 2000 MPa grade, and the tensile strength of the steel ≥ 1800 MPa;

[0039] A carbon content of 0.15 wt.% < C ≤ 0.27 wt.% (especially 0.18 - 0.26 wt.%) usually corresponds to steel of 1500 MPa grade, and the tensile strength of the steel ≥ 1350 MPa;

[0040] A carbon content of 0.05 wt.% < C ≤ 0.15 wt.% (especially 0.05 - 0.12 wt.%) usually corresponds to steel of 1000 MPa grade, and the tensile strength of the steel ≥ 950 MPa.

[0041] In the context of the present invention, the content or hardness of the components in the weld seam or the base material refers to the average content or hardness, unless otherwise clearly specified. wt.% means by weight percentage.

[0042] In order to ensure that the weld seam has sufficient strength, according to the present invention, the carbon content C in the weld seam 焊缝 should be higher than the carbon content C in the base material 基材 , satisfying C 基材 +0.01 wt.% ≤ C 焊缝 . At the same time, for the cases where the lower of the tensile strength grades of the welded steel plates belongs to 2000 MPa grade, 1500 MPa grade, and 1000 MPa grade respectively, the carbon content C in the weld seam 焊缝 should be not less than 0.32 wt.%, 0.19 wt.%, and 0.05 wt.% respectively. On the other hand, in order to ensure the toughness of the weld seam, the carbon content of the weld seam should not be too high. When C 基材 does not exceed 0.27 wt.%, C 焊缝 should not exceed 0.32 wt.%. For the 2000 MPa grade steel with a higher C 基材 , in order to ensure strength, C 焊缝 can be appropriately increased, but still should not exceed 0.4 wt.%.

[0043] The weld evaluation factor FA should be greater than 10% to ensure that the weld seam has sufficient strength. In order to ensure the toughness of the weld seam and the ability to resist hydrogen-induced delayed cracking, the weld evaluation factor FA should not be too high. For the cases where the welded steel plates have various tensile strength grades, the present invention finds that the upper limits of FA that can achieve good weld seam toughness and the ability to resist hydrogen-induced delayed cracking are different, and corresponding ranges are given for different cases respectively.

[0044] Taking all factors into consideration, the present invention proposes the following solutions for laser welding of pre-plated steel plates with various tensile strength levels:

[0045] A laser-welded component comprising:

[0046] a first pre-plated steel plate having a first pre-plated layer of aluminum or an aluminum alloy;

[0047] a second pre-plated steel plate having a second pre-plated layer of aluminum or an aluminum alloy provided thereon; and

[0048] a weld connecting the first pre-plated steel sheet to the second pre-plated steel sheet,

[0049] Wherein, the weld has a weld evaluation factor FA=10Mn 焊缝 +77C 焊缝 -1900Al 焊 缝 2 -12Al 焊缝 , where Mn 焊缝 、C 焊缝 、Al 焊缝 are the manganese, carbon and aluminum contents in the weld in percentage by weight,

[0050] The alloy composition of the weld and the weld evaluation factor FA satisfy the following conditions:

[0051] 1.0wt.%≤Mn 焊缝 ≤3.0wt.%

[0052] 0.3wt.%≤Al 焊缝 ≤1.0wt.%, and

[0053] (a) at 0.27 wt.% <C 基材 When ≤0.38wt.%, the following conditions are met:

[0054] 0.32wt.%≤C 焊缝 ≤0.4wt.%

[0055] C 基材 +0.01wt.%≤C 焊缝 ;and

[0056] 10%≤FA≤32%;

[0057] (b) at 0.15 wt.% <C 基材 When ≤0.27wt.%, the following conditions are met:

[0058] 0.19wt.%≤C 焊缝 ≤0.32wt.%

[0059] C 基材 +0.01wt.%≤C 焊缝 ,and

[0060] 10% ≤ FA ≤ 30%; or

[0061] (c) 0.05 wt.% <C 基材 When ≤0.15wt.%, the following conditions are met:

[0062] 0.05wt.%≤C 焊缝 ≤0.32wt.%

[0063] C 基材 +0.01wt.%≤C 焊缝 ,and

[0064] 10%≤FA≤25%;

[0065] Wherein, when the tensile strength of the first pre-plated steel sheet is different from that of the second pre-plated steel sheet, C 基材 represents the carbon content of the first pre-plated steel sheet and the second pre-plated steel sheet with a relatively lower tensile strength; when the tensile strength of the first pre-plated steel sheet is the same as that of the second pre-plated steel sheet, C 基材 It represents the carbon content of either the first pre-plated steel sheet or the second pre-plated steel sheet.

[0066] That is, the present invention proposes corresponding weld alloy compositions for different combinations of steel plates to be welded. Research has found that when the weld alloy composition meets the conditions of the present invention, due to the realization of "weld micro-strengthening + weld toughening", even if the weld is formed between steel plates of different strength levels or different thicknesses, it can ensure that the weld has both excellent strength and excellent toughness and resistance to hydrogen-induced delayed cracking. In this way, on the one hand, the present invention solves the problem of providing reliable welding between steel plates of different strength levels and different thickness specifications, and overcomes the limitations of the existing technology that is only applicable to steel plates of specific strength levels or specific thickness relationships; on the other hand, the present invention overcomes the contradiction between weld strength and toughness and resistance to hydrogen-induced delayed cracking, and achieves a balance of various performance properties.

[0067] It is worth noting that the present invention can also achieve good results in welding 2000MPa-grade steel plates to 2000MPa-grade steel plates. In fact, from the perspective of ensuring weld strength and toughness, welding two 2000MPa-grade steel plates is very challenging. This is because the 2000MPa material itself already has a relatively high carbon content (usually between 0.28wt.% and 0.38wt.%), and in order to ensure that the weld strength of the 2000MPa / 2000MPa-grade steel plate is higher than the base material strength of the 2000MPa-grade steel plate, in theory, the weld needs to contain a higher C and Mn content than the 2000MPa base material. The increase in the C and Mn content in the weld (to about 0.4wt.% or more) will easily lead to the generation of hard and brittle twin martensite in the weld, which has poor toughness and weaker ability to resist the risk of delayed cracking. Therefore, achieving high-quality welds between 2000 / 2000 MPa-grade steel plates presents a dilemma: balancing the need to ensure high weld strength with high C and Mn contents, while also minimizing the negative impact of these contents on weld toughness and resistance to hydrogen-induced delayed cracking. Existing technologies offer no solution to this dilemma. Indeed, 2000 MPa-grade steel plates themselves are cutting-edge and emerging products, and related research and development is still in its early stages. The present invention addresses this challenge by including an appropriate amount of aluminum in the weld alloy, mitigating the negative effects of increased C and Mn contents on weld toughness and resistance to hydrogen-induced delayed cracking.

[0068] Furthermore, for martensitic steel, the main strengthening mechanism is the interaction between solute atoms C and high-density dislocations. The toughest martensite is dislocation martensite (also known as lath martensite). The martensitic phase transformation relies on shear deformation caused by dislocation slip. Carbon can stabilize and strengthen austenite. As the carbon content increases, the difficulty of austenite to martensite transformation increases during cooling, and the martensitic phase transformation temperature also decreases. A higher dislocation density will be generated in the martensite, and these high-density dislocations in the martensite are pinned by carbon atoms. Therefore, the interaction between the higher dislocation density and the higher content of carbon atoms further increases the strength of martensitic steel. However, the interaction between the high content of carbon atoms and the higher density of dislocations will significantly reduce the ability of martensite to multiply during plastic deformation. Therefore, the increase in carbon content leads to a decrease in its martensitic toughness. More importantly, dislocations act as hydrogen traps, making it easier for martensite to absorb more hydrogen, and dislocations act as line defects to promote hydrogen diffusion. Therefore, high C content increases the risk of hydrogen-induced delayed cracking of martensite. The present invention aims to overcome the risk of hydrogen-induced delayed cracking caused by weld strengthening. First, the addition of Al element is beneficial to improving the risk of hydrogen-induced delayed cracking of martensite. On the basis of using Al to improve hydrogen-induced cracking performance, it is necessary to further determine the upper limit of the carbon content of the weld. In particular, this is especially important for welding 2000MPa grade steel and 2000MPa grade steel.

[0069] After careful research, the inventors found that for 2000MPa grade steel, the carbon content in the weld should not be greater than 0.4wt.%, otherwise the weld will have a greater risk of delayed cracking; and when the carbon content of the weld increases by about 0.06wt.% compared to the base material, the weld strength is significantly increased compared to the base material strength, which will lead to stress concentration at the weld / base material interface during deformation. Especially for the tailor welding of 2000MPa grade steel, the base material toughness is relatively low, and stress concentration is likely to lead to the risk of delayed cracking in the weld. Therefore, it is preferred that the carbon content C of the one with the relatively lower tensile strength of the two pre-plated steel plates be greater than 0.4wt.%. 基材 Comply with 0.27wt.% <C 基材 ≤0.38wt.%, in order to ensure the weld quality, C 焊缝 ≤C 基材 +0.06wt.%.

[0070] Similarly, for the carbon content C of the first pre-plated steel sheet and the second pre-plated steel sheet with relatively lower tensile strength, 基材 Comply with 0.15wt.% <C 基材 ≤0.27wt.%, preferably, in order to further ensure the toughness of the weld and to avoid excessive stress concentration at the weld / base material interface due to excessive difference in weld / base material strength, C 焊缝 ≤C 基材 +0.11wt.%.

[0071] Similarly, the carbon content C of the first pre-plated steel sheet and the second pre-plated steel sheet having a relatively lower intermediate tensile strength is 基材 Comply with 0.05wt.% <C 基材 ≤0.15wt.%, preferably, in order to further ensure the toughness of the weld, it is necessary to meet C 焊缝 ≤C 基材 +0.30wt.%.

[0072] Therefore, according to some embodiments, the laser-welded component further satisfies the following conditions:

[0073] (a) at 0.27 wt.% <C 基材 When ≤0.38wt.%, the following conditions are met:

[0074] C 焊缝 ≤C 基材 +0.06wt.%;

[0075] (b) at 0.15 wt.% <C 基材 When ≤0.27wt.%, the following conditions are met:

[0076] C 焊缝 ≤C 基材 +0.11 wt.%, preferably C 焊缝 ≤C 基材 +0.1wt.%;

[0077] (c) 0.05 wt.% <C 基材 When ≤0.15wt.%, the following conditions are met:

[0078] C 焊缝 ≤C 基材 +0.30wt.%;

[0079] Wherein, when the tensile strength of the first pre-plated steel sheet is different from that of the second pre-plated steel sheet, C 基材 represents the carbon content of the first pre-plated steel sheet and the second pre-plated steel sheet with a relatively lower tensile strength; when the tensile strength of the first pre-plated steel sheet is the same as that of the second pre-plated steel sheet, C 基材 It represents the carbon content of either the first pre-plated steel sheet or the second pre-plated steel sheet.

[0080] Preferably, the Mn content in the weld alloy composition may be 1.0-2.5 wt.%.

[0081] Preferably, the Al content in the weld alloy composition may be 0.4 to 0.8 wt.%.

[0082] Preferably, the solder alloy composition satisfies:

[0083] (a) The carbon content C of the first pre-plated steel sheet or the second pre-plated steel sheet with the relatively lower tensile strength (if the tensile strengths of the two are the same, either one of them) 基材 Comply with 0.27wt.% <C 基材 When ≤0.38wt.%, the weld evaluation factor is 10%≤FA≤30%;

[0084] (b) The carbon content C of the first pre-plated steel sheet or the second pre-plated steel sheet with the relatively lower tensile strength (if the tensile strengths of the two are the same, either one of them) 基材 Comply with 0.15wt.% <C 基材 When ≤0.27wt.%, the weld evaluation factor is 10%≤FA≤26%;

[0085] (c) The carbon content C of the first pre-plated steel sheet or the second pre-plated steel sheet with the relatively lower tensile strength (if the tensile strengths of the two are the same, either one of them) 基材 Comply with 0.05wt.% <C 基材When ≤0.15wt.%, the weld evaluation factor is 10%≤FA≤22%.

[0086] The Al content in the aluminum or aluminum alloy pre-plating layer of the present invention is preferably not less than 85 wt.%. The pre-plating layer is, for example, an aluminum-silicon pre-plating layer commonly used in the art, which preferably includes 88-95 wt.% Al and 5-12 wt.% Si.

[0087] The Al content in the resulting weld is related to the thickness of the aluminum or aluminum alloy pre-plating layer and the thickness of the steel plates being welded. Since the aluminum content in the steel plate is lower than that in the aluminum or aluminum alloy pre-plating layer, the Al content in the weld generally tends to increase as the thickness of the aluminum or aluminum alloy pre-plating layer increases or the thickness of the steel plates decreases.

[0088] The inventors of the present invention have found that if the average thickness of the aluminum or aluminum alloy pre-plating layer (especially the aluminum-silicon pre-plating layer) on one side of the steel plate is controlled at 6μm to 19μm, then since the pre-plating layer itself is relatively thin, even if the pre-plating layer is not peeled off before welding, the aluminum content melted into the weld is also low, but not too low to cause poor weld toughness. Without peeling off the pre-plating layer, laser filler welding with a welding wire with appropriate C and Mn content can be performed to achieve an appropriate alloy weld composition. In this way, the present invention is particularly suitable for use with steel plates with a pre-plating layer thickness of 6μm to 19μm, thereby further simplifying the process and reducing costs. Preferably, the thickness of the aluminum or aluminum alloy pre-plating layer is 8μm to 16μm. Preferably, the thickness of the aluminum or aluminum alloy pre-plating layer is 10μm to 16μm.

[0089] In some embodiments, the thickness of the first pre-plated steel sheet and / or the second pre-plated steel sheet is 0.8 to 3.0 mm, preferably 1.0 to 2.5 mm.

[0090] The present invention also provides an improved welding wire, comprising, by weight percentage, the following components: C: 0.30-0.45 wt.%, preferably 0.35-0.45 wt.%. C primarily functions as solid solution strengthening, effectively meeting weld strength requirements; Mn: 1.0-3.0 wt.%. Mn primarily functions as ensuring weld hardenability, thereby better ensuring a fully martensitic weld structure, preferably 1.5-2.5 wt.%. According to a particularly advantageous embodiment, in addition to the aforementioned C and Mn components, the remainder of the welding wire consists of Fe and unavoidable impurities, meaning that no other alloying elements are required.

[0091] In some embodiments, in addition to C and Mn, the welding wire may also contain less than 0.035 wt.% of Al. Al is a strong deoxidizer, so in order to achieve the deoxidation effect during the welding wire smelting process, the Al content is required to be above about 0.010 wt.%. The welding wire may also contain less than 0.022 wt.% of Si to play a role in solid solution strengthening and thus improve the strength of the weld.

[0092] The present invention innovatively discovered that the aforementioned welding wire can achieve high-quality laser tailor welding of aluminum or aluminum alloy pre-coated (particularly aluminum-silicon pre-coated) steel plates with any strength grade and thickness combination between 1000 and 2000 MPa, improving weld toughness and stability. On the one hand, this overcomes the shortcomings of existing technologies, such as uneven weld composition distribution and poor weld performance stability when welding steel plates of different strengths or thicknesses. On the other hand, it is a "universal" welding wire suitable for various steel plate strength and thickness combinations, greatly facilitating production.

[0093] In particular, when this type of welding wire is used for laser welding of steel plates with an aluminum-silicon pre-coating layer of 6μm to 19μm thick, without pre-treatment such as stripping the pre-coating layer on the steel plates, it is possible to obtain excellent welding joints for combinations of steel plates of different strength grades and thickness specifications.

[0094] Furthermore, the welding wire can have a relatively low hardness, making it easier to draw and manufacture. Furthermore, while a harder welding wire can be prone to unstable feeding due to its tortuous path through the wire guide tube, a welding wire with a hardness below 300 HV can achieve smoother wire feeding.

[0095] Furthermore, when using this welding wire, the gap requirement between the welded steel plates is relaxed, allowing for a gap range of up to 0.5 mm (allowing for uncontrolled gaps caused by cutting or other factors), further improving efficiency and reducing costs. Furthermore, this welding wire does not contain a large amount of expensive alloying elements, making it very cost-effective.

[0096] In the context of the present invention, "wire filling amount" refers to the volume ratio of the material from the welding wire in the formed weld, which is closely related to the gap between the welding surfaces of the welded materials during tailor welding.

[0097] As a preferred embodiment, the weld alloy composition required by the present invention can be achieved using the improved welding wire described above. To facilitate obtaining appropriate C and Mn contents in the weld, the welding wire filling amount can be 5-30%, preferably 10-25%.

[0098] It should be noted that while the aforementioned welding wire compositions and filler amounts are particularly advantageous and constitute the preferred embodiment of the present invention, the present invention is not limited to the aforementioned welding wire compositions and filler amounts. In fact, any weld alloy composition resulting from tailored welding satisfies the conditions defined by the present invention. Using other welding wire compositions or filler amounts may also achieve the weld alloy composition required by the present invention, thereby meeting the weld performance requirements.

[0099] Similarly, while the present invention is particularly suitable for use with steel sheets having a pre-plated layer thickness of 6 μm to 19 μm, the present invention is not limited to use with steel sheets having such a pre-plated layer thickness. For example, in the case of a thicker pre-plated layer, the aluminum content in the weld can be brought within the required range of the present invention by removing a small amount of aluminum from the pre-plated layer before welding.

[0100] The present invention also relates to a laser welding method for forming the aforementioned laser-welded component, wherein a welding wire comprising the following composition is used during laser welding: C: 0.30-0.45 wt.%, Mn: 1.0-3.0 wt.%; and the welding wire filling amount is 5-30%.

[0101] The present invention also provides an advantageous hot stamping formed component, comprising:

[0102] a first coated steel plate having a first coating layer thereon;

[0103] a second coated steel plate having a second coating layer thereon; and

[0104] a weld connecting the first coated steel sheet to the second coated steel sheet,

[0105] Wherein, the weld has a weld evaluation factor FA=10Mn 焊缝 +77C 焊缝 -1900Al 焊 缝 2 -12Al 焊缝 , where Mn 焊缝 、C 焊缝 、Al 焊缝 are the manganese, carbon and aluminum contents in the weld in percentage by weight,

[0106] The alloy composition of the weld and the weld evaluation factor FA satisfy the following conditions:

[0107] 1.0wt.%≤Mn 焊缝 ≤3.0wt.%

[0108] 0.3wt.%≤Al 焊缝 ≤1.0wt.%, and

[0109] (a) at 0.27 wt.% <C 基材 When ≤0.38wt.%, the following conditions are met:

[0110] 0.32wt.%≤C 焊缝 ≤0.4wt.%

[0111] C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.06wt.%; and

[0112] 10%≤FA≤32%, preferably 10%≤FA≤30%;

[0113] (b) at 0.15 wt.% <C 基材 When ≤0.27wt.%, the following conditions are met:

[0114] 0.19wt.%≤C 焊缝 ≤0.32wt.%, preferably 0.19wt.%≤C 焊缝 ≤0.29wt.%

[0115] C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.11wt.%, preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.1wt.%, and

[0116] 10%≤FA≤30%, preferably 10%≤FA≤26%; or

[0117] (c) 0.05 wt.% <C 基材 When ≤0.15wt.%, the following conditions are met:

[0118] 0.05wt.%≤C 焊缝 ≤0.32wt.%, preferably 0.05wt.%≤C 焊缝 ≤0.27wt.%

[0119] C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.30wt.%, and

[0120] 10%≤FA≤25%, preferably 10%≤FA≤22%;

[0121] Wherein, when the tensile strength of the first coated steel plate is different from that of the second coated steel plate, C 基材 represents the carbon content of the first coated steel plate and the second coated steel plate with a relatively lower tensile strength; when the tensile strength of the first coated steel plate and the second coated steel plate are the same, C 基材 Indicates the carbon content of either the first plated steel sheet or the second plated steel sheet.

[0122] The first and second coating layers on the first and second coated steel plates of the hot stamping formed component are respectively formed by hot stamping a first pre-coating layer and a second pre-coating layer consisting of aluminum or aluminum alloy on the steel plate. Preferably, the thickness of the first pre-coating layer and / or the second pre-coating layer is 6μm to 19μm, preferably 8μm to 18μm.

[0123] According to the present invention, the ferrite content in the weld of the hot stamped component is not more than 5% by volume, preferably not more than 2% by volume.

[0124] In this hot stamping forming structure, the hardness of the weld meets the following conditions:

[0125] (a) When the tensile strength level of the first coated steel sheet and the second coated steel sheet is the same, HV 焊缝 ≥HV 基材 ;

[0126] (b) When T1×YS1≥0.9×T2×YS2, HV 焊缝0.2 ≥HV 高 强度基材 ;

[0127] (c) When T1×YS1<0.9×T2×YS2, HV 焊缝 ≥HV 低强度基材 ;

[0128] Wherein, YS1 is the yield strength of the first coated steel plate or the second coated steel plate with the lower yield strength, T1 is the thickness of the first coated steel plate or the second coated steel plate with the lower yield strength, YS2 is the yield strength of the first coated steel plate or the second coated steel plate with the higher yield strength, T2 is the thickness of the first coated steel plate or the second coated steel plate with the higher yield strength, HV 基材 HV is the hardness of the first coated steel sheet or the second coated steel sheet after hot stamping. 高强度基材HV is the hardness of the first coated steel sheet and the second coated steel sheet with higher yield strength after hot stamping, 焊缝0.2 HV is the hardness value within 0.2 mm from the weld fusion line on the side of the first coated steel sheet and the second coated steel sheet with higher yield strength after hot stamping. 低强度基材 The hardness of the first coated steel sheet or the second coated steel sheet having a lower yield strength after hot stamping.

[0129] Preferably, the hot stamped component of the present invention can be manufactured by hot stamping the above-mentioned laser-welded component according to the present invention.

[0130] The present invention also relates to a method for producing a hot stamping formed component, comprising the following steps:

[0131] A) providing a laser-welded component according to the present invention;

[0132] B) Complete austenitization treatment: heating the laser welded component in step A) to above 900° C. and maintaining the temperature;

[0133] C) Hot stamping process: After completing step B), the heated laser-welded component is transferred to a press for hot deformation and cooled to below 300° C. in a die to obtain a hot stamped component.

[0134] In some embodiments, the average cooling rate of the hot stamped component from 700° C. to the Ms temperature is not less than 40° C. / s in regions not thermally deformed, and is cooled at a higher average cooling rate in regions thermally deformed.

[0135] Leveraging this novel concept, the present invention enables high-quality laser welding of various combinations of hot stamping steels with aluminum or aluminum alloy pre-plating, across a wide range of tensile strength levels and thicknesses. This method is well-suited for welding steels of equal strength, varying strengths, and varying thicknesses, resulting in high-quality welds with excellent strength, toughness, and resistance to hydrogen-induced delayed cracking. This overcomes the limitations of existing technologies, which struggled to accommodate a wide range of welding material combinations and balance weld strength and toughness.

[0136] In addition, the solution of the present invention does not impose strict requirements on the size of the weld butt gap, and can be implemented without additional steps such as stripping the pre-plating layer in advance, and can be achieved at a low cost.

[0137] In addition, the welding wire proposed by the present invention does not need to contain a large amount of expensive alloy components, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0138] Figure 1 schematically shows the weld hardness measurement position;

[0139] Figure 2 schematically shows the hardness value HV within 0.2 mm from the weld fusion line on the side of the substrate with high yield strength. 焊缝0.2 The measurement location for the test. DETAILED DESCRIPTION

[0140] The present invention will be described in more detail below with reference to exemplary embodiments. The main components of the solder joint alloy of the present invention are introduced as follows.

[0141] C: Carbon content in the weld 焊缝 Related to the carbon content or strength level of the pre-coated steel plate being welded:

[0142] (a) The carbon content C of the first pre-plated steel sheet or the second pre-plated steel sheet with the relatively lower tensile strength (if the tensile strengths of the two are the same, either one of them) 基材 Comply with 0.27wt.% <C 基材 ≤0.38wt.%, it is necessary to meet 0.32wt.%≤C 焊缝 ≤0.4wt.%, and C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.06wt.%;

[0143] (b) The carbon content C of the first pre-plated steel sheet or the second pre-plated steel sheet with the relatively lower tensile strength (if the tensile strengths of the two are the same, either one of them) 基材 Comply with 0.15wt.% <C 基材 ≤0.27wt.%, it is necessary to meet 0.19wt.%≤C 焊缝 ≤0.32wt.%, and C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.11wt.%, preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.1wt.%;

[0144] (c) The carbon content C of the first pre-plated steel sheet or the second pre-plated steel sheet with the relatively lower tensile strength (if the tensile strengths of the two are the same, either one of them) 基材 Comply with 0.05wt.% <C 基材≤0.15wt.%, it is necessary to meet 0.05wt.%≤C 焊缝 ≤0.32wt.%, and C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.30wt.%.

[0145] Carbon is an effective solid-solution strengthening element. To ensure sufficient tensile strength in welds, the carbon content must be at least approximately 0.05 wt%. However, if the carbon content exceeds 0.4 wt%, brittle twinned martensite will form, resulting in poor ductility and toughness, and significantly reduced hydrogen embrittlement resistance. Therefore, for welding low-strength steel plates, the carbon content of the weld of the present invention is not less than 0.05 wt%. For welding high-strength steel plates, the carbon content of the weld of the present invention is not more than 0.4 wt%.

[0146] For the case where the tensile strength of the two pre-plated steel plates is relatively low and one of them is 2000MPa, 1500MPa and 1000MPa respectively, both must meet C 基材 +0.01wt.%≤C 焊缝 , ensuring that the weld strength is slightly greater than the base material, achieving "micro-strengthening" of the weld. Preferably, in order to further ensure the toughness of the weld, the weld carbon content C is obtained for various situations. 焊缝 and the carbon content of the substrate C 基材 For example, when welding 2000MPa steel to 2000MPa steel, there is C 焊缝 ≤C 基材 +0.06wt.%.

[0147] Mn: about 1.0-3.0 wt.%, preferably 1.0-2.5 wt.%.

[0148] Mn can improve the hardenability of steel to ensure the strength of the weld. To ensure that the weld has good hardenability, the Mn content should not be less than 1.0wt.%. On the other hand, when the Mn content in the weld exceeds 3.0wt.%, Mn segregation is likely to occur in the weld, affecting the weld performance. Moreover, an increase in Mn content tends to lead to a decrease in the martensite plastic toughness formed in the weld after hot stamping, an increase in brittleness, and an increase in the risk of hydrogen-induced delayed cracking in the weld. Therefore, the Mn content in the weld should not be too high and should not exceed 3.0wt.%, preferably not more than 2.5wt.%.

[0149] Al: about 0.3-1.0 wt.%, preferably 0.4-0.8 wt.%.

[0150] Aluminum is a ferrite stabilizing element. If there is too much Al in the weld, it is easy to cause the weld to fail to fully form martensite after hot stamping. Studies have found that when the Al content in the weld exceeds 1.0wt.%, it is easy to cause the formation of intermetallic compound regions with high brittleness, thereby inducing cracks, thereby affecting the strength of the weld. Therefore, the Al content in the weld should not be too high. According to the present invention, it should not exceed 1.0wt.%. Preferably, the Al content in the weld does not exceed 0.8wt.%. This is to avoid the local formation of ferrite in the weld. The difference in strength between ferrite and martensite can easily lead to stress concentration and induce cracks. On the other hand, the inventors of the present invention have found that if there is an appropriate amount of Al in the weld, it can have the effect of toughening the weld and enhance the weld's ability to resist hydrogen-induced delayed cracking. Therefore, in order to obtain good resistance to hydrogen-induced delayed cracking, according to the present invention, the Al content in the weld should not be less than 0.3wt.%, preferably not less than 0.4wt.%.

[0151] In addition to the above components, as is well known to those skilled in the art, the weld is obtained by melting the base material and the welding wire material, which also contains the corresponding components in the base material and the welding wire.

[0152] Furthermore, in order to judge whether the performance of the weld meets the requirements, especially whether the resistance of the weld to hydrogen-induced delayed cracking meets the requirements, the present invention proposes to calculate the weld evaluation factor FA to assist in judging whether the weld alloy composition is conducive to achieving excellent weld performance: FA = 10Mn 焊缝 +77C 焊缝 -1900Al 焊缝 2 -12Al 焊缝 , where Mn 焊缝 、C 焊缝 、Al 焊缝 They are the contents of manganese, carbon and aluminum in the weld in percentage by weight respectively.

[0153] To achieve good weld performance, the manganese, carbon, and aluminum contents of the weld must fall within the specific ranges given above, and the FA must also fall within the corresponding ranges. The required FA value range is related to the carbon content of the steel plates being welded. The present invention requires that it meet the following conditions:

[0154] (a) at 0.27 wt.% <C 基材 When ≤0.38wt.%, it is necessary to satisfy 10%≤FA≤32%, preferably 10%≤FA≤30%;

[0155] (b) at 0.15 wt.% <C 基材 When ≤0.27wt.%, it must meet the following requirements: 10%≤FA≤30%, preferably 10%≤FA≤26%;

[0156] (c) 0.05 wt.% <C 基材 When the content of FA is ≤0.15 wt.%, the following conditions must be met: 10% ≤ FA ≤ 25%, preferably 10% ≤ FA ≤ 22%.

[0157] For the three cases (a), (b), and (c) above, the weld evaluation factor FA must be no less than 10%. This is because according to the calculation formula of FA, the FA value decreases with the increase of Al content. When the aluminum content increases, the complete austenitization temperature of the weld will increase. Using the existing hot stamping heating process, ferrite is easily produced in the weld of the hot stamping component, which in turn causes the weld to have a dual-phase structure of martensite and ferrite, and the weld is prone to breakage during stretching. The inventors have found that when FA ≥ 10%, the probability of ferrite being produced in the weld under the existing hot stamping process is extremely low, thereby better ensuring the strength of the weld. On the other hand, the upper limit of the FA value is related to the weld's ability to resist hydrogen-induced delayed cracking. The lower the FA value, the lower the risk of hydrogen-induced delayed cracking of the weld. After research, the inventors found that for case (a), when the FA of the weld is ≤32%, the risk of hydrogen-induced delayed cracking of the weld is extremely low, and FA ≤30% is further preferred; for case (b), when the FA of the weld is ≤30%, the risk of hydrogen-induced delayed cracking of the weld is extremely low, and FA ≤26% is further preferred; for case (c), when the FA of the weld is ≤25%, the risk of hydrogen-induced delayed cracking of the weld is extremely low, and FA ≤22% is further preferred.

[0158] If the percentage of each element is removed for calculation, the evaluation factor FB can be set instead of FA for judgment. The two have the same effect: FB = 10Mn + 77C - 19Al 2 -12Al, where Mn, C, and Al represent the percentage content of each element in the weld. According to the present invention, the following conditions must be met:

[0159] (a) at 0.27 wt.% <C 基材 When the content is less than or equal to 0.38 wt.%, the content must satisfy 10≤FB≤32, preferably 10≤FB≤30;

[0160] (b) at 0.15 wt.% <C 基材 When ≤0.27wt.%, the following conditions must be met: 10≤FB≤30, preferably 10≤FB≤26;

[0161] (c) 0.05 wt.% <C 基材 When ≤0.15wt.%, it must satisfy: 10≤FB≤25, preferably 10≤FB≤22.

[0162] To simplify the process, the present invention proposes that setting the aluminum or aluminum alloy pre-plating layer thickness to 6μm to 19μm is particularly advantageous. This pre-plating thickness makes it easier to achieve the appropriate Al content required by the present invention in the weld without requiring additional pre-welding operations such as stripping the pre-plating layer.

[0163] The present invention will be described in more detail below with reference to exemplary embodiments. The following examples or experimental data are intended to illustrate the present invention, and it should be clear to those skilled in the art that the present invention is not limited to these examples or experimental data.

[0164] As an example, a common hot stamping steel plate with a grade of 1000 MPa to 2000 MPa and an aluminum-silicon pre-plating layer on the market is provided, and its composition is shown in Table 1.

[0165] Table 1 Composition of steel with aluminum-silicon pre-plating layer (wt.%)

[0166] The balance is Fe and other inevitable impurity elements.

[0167] According to ASTM E8 / E8M-09, the hot stamped components made from the above materials were made into A50 tensile specimens. The mechanical properties obtained from the tensile tests are shown in Table 2.

[0168] Table 2 Mechanical properties of steel with aluminum-silicon pre-plating layer after hot stamping

[0169] Welding wires with a diameter of 1 mm were provided, each having different compositions, as shown in Table 3. Among them, W1, W2, and W5 are general-purpose welding wires suitable for welding steel plates of varying strengths and thicknesses according to the present invention. The compositions of the welding wires W3 and W4 are outside the scope of this patent and are provided as comparative examples.

[0170] Table 3 Composition of experimental welding wire (wt.%)

[0171] For the aforementioned steel, various strength grades and thicknesses were selected, along with different welding wire compositions and filler weights, to create various laser welding combinations (see Table 4). No stripping or other operations were performed on the pre-plating layer prior to laser welding. The pre-plating thickness was determined by taking the average of three metallographically measured locations.

[0172] The amount of welding wire filling is calculated based on the butt gap and weld width of the welded steel plates in the following way: a feeler gauge is used to preset a certain gap (e.g., 0 to 0.5 mm) in the middle of the butt joint of the plates to be welded. After laser welding, the widths of the upper and lower surfaces of the weld are measured and averaged. The preset gap is divided by the average weld width to obtain an estimated value of the welding wire filling amount.

[0173] Table 4 Welding combination of experimental steel

[0174] After laser welding is completed, the laser-welded pre-plated steel sheets are hot stamped according to conventional hot stamping processes in the art. In this example, a hot stamping simulation is performed on each of the laser-welded pre-plated steel sheets, and the hot stamping process is as follows:

[0175] 1) Heat the laser-welded pre-plated steel plate to 900°C and hold for 300 seconds, then cool it to above 700°C for hot stamping with a pressure of 400t and a holding time of 10 seconds, and then cool it to below 100°C in the mold and remove it;

[0176] 2) To simulate the actual use of automotive parts, the steel plates were cooled to room temperature and placed in a tempering furnace at 170°C for 20 minutes to simulate the painting and baking process of the parts. They were then taken out and air-cooled to room temperature to obtain hot stamping formed components.

[0177] Table 5 shows the mechanical property measurement results of the laser welded blanks after hot stamping, wherein the underlined examples are comparative examples that do not meet the requirements of the present invention. The measurement methods of each parameter / property are as follows.

[0178] The tensile properties were measured according to ASTM E8 / E8M-09, Standard Methods for Tensile Testing of Metallic Materials. A hot stamped component obtained by laser welding pre-coated steel sheets was made into a tensile specimen with the weld located in the middle of the tensile specimen.

[0179] The weld hardness test is carried out in accordance with the standard GBT4342-1991. The hardness measurement location is shown schematically in Figure 1. 焊缝 , take at least 6 test points along the weld diagonal line and take the average value; to measure the base material hardness, take at least three test points outside the weld and take the average value. In addition, the hardness value HV within 0.2mm from the weld fusion line on the side of the base material with high yield strength 焊缝0.2 The test value locations are schematically shown in FIG2 , that is, 3 to 6 hardness test points are taken within 0.2 mm from the weld edge, and the average value is taken.

[0180] The observation of hydrogen-induced delayed cracking was conducted according to the following method: 15 × 115 mm specimens were taken from hot-stamped flat plates according to GB / T 15970.2-2000. The weld was located in the middle of the specimen and perpendicular to the length of the specimen. The applied stress value (yield strength of a low-carbon matrix) was converted to deflection according to ISO 7539-2:1989. The deflected specimens were placed in an environment with a pH of 1. The pH value was calibrated every 24 hours until the specimen broke, and the fracture location was recorded.

[0181] Weld Seam Composition Measurement Method: Cut the weld section of a laser-welded component or laser-welded thermoformed component, ensuring the entire weld is sampled. The weld length should be greater than or equal to 2 mm. Samples should be taken from at least three different locations along the same weld. After sampling, the welds are tested for C, Mn, and Al content using a wet chemical method.

[0182] Table 5 Performance measurement results after hot stamping

[0183] As shown in Table 4, welds S1 through S50 were welded from various steel plates of various strength grades and thicknesses, including 1000 MPa, 1500 MPa, and 2000 MPa. The welding wire compositions used were numbered W1 through W5, respectively, and the filler wire weight was estimated based on the weld gap established during welding. The resulting laser-welded components were hot stamped and tempered, and then evaluated for mechanical properties, weld composition, and hydrogen-induced delayed cracking. Refer to Table 5 for the analytical results.

[0184] S1-S4, S44, and S46 involve butt welding of 1000MPa-grade and 1000MPa-grade materials, using three different welding wires, W1, W2, and W5, and three different wire filler weights, 5%, 25%, and 30%, respectively. Regarding weld composition, since the welding wire composition, wire filler weight, and pre-plating thickness of the steel sheets used in S1-S4, S44, and S46 are all within the ranges recommended by the present invention, despite slight differences in the specific values ​​of each parameter, the weld alloy composition that meets the requirements of the present invention is achieved. The C content in welds S1-S4, S44, and S46 was measured to be between 0.09 and 0.18 wt.%, the Mn content was between 1.70 and 1.90 wt.%, and the Al content was between 0.31 and 0.63 wt.%. Substituting these into the formulas for FA or FB, it can be seen that the requirements of the present invention of 10% ≤ FA ≤ 25% or 10 ≤ FB ≤ 25 are met.

[0185] In terms of weld performance, hardness measurements showed that the weld hardness was greater than that of the T1 substrate. Static tensile tests revealed that all specimens fractured from the T1 substrate. Furthermore, observations of hydrogen-induced delayed cracking revealed that specimens S1-S4, S44, and S46 all initially cracked from the T1 substrate. Therefore, the weld performance of S1-S4, S44, and S46 met the requirements.

[0186] S5 to S7 also involve butt welding of 1000 MPa-grade and 1000 MPa-grade materials, but S5 and S6 use larger wire filling amounts that do not fall within the scope recommended by the present invention, and S7 and S45 use comparative wire W3 that does not fall within the composition recommended by the present invention.

[0187] It can be seen from S5 and S6 that when W1 and W2 welding wires are used and the welding wire filling amount is increased to 35%, the C and Mn contents in the weld are increased, which in turn increases the hardness and strength of the weld. The average hardness of the weld reaches 451HV and 460HV respectively, which is much greater than the average hardness of the substrate. At this time, the strength of the weld is greater than the strength of the substrate, so the specimen breaks from the T1 substrate during static tension. Despite the excellent strength, the S5 and S6 welds have poor resistance to hydrogen-induced delayed cracking, and the cracking location is in the weld. This is because the Al content in the weld is low. Calculation shows that FA>25% (FB>25), which does not meet the requirements of the present invention. In other words, the amount of Al contained in the S5 and S6 welds is not enough to achieve a good match with C and Mn, and cannot fully exert the role of Al in improving the toughness of the weld and improving resistance to hydrogen-induced cracking.

[0188] S7 uses the comparative welding wire W3, which has higher carbon and manganese content. Even with a 25% filler, the weld also exhibits relatively high carbon and manganese content, which is not well-matched with the Al content. As a result, while weld S7 exhibits greater hardness and strength than base material T1, its resistance to hydrogen-induced delayed cracking is poor, with cracking occurring in the weld. Calculations show that FA = 30.4969%, which does not meet the present invention's requirement of 10% ≤ FA ≤ 25%.

[0189] S45 uses a pre-plating thickness exceeding 19μm without prior stripping, resulting in excessively high Al content in the weld. This resulted in the weld breaking during tensile testing due to insufficient strength. Furthermore, calculations show an FA value of <10%, reflecting a failure to achieve a good balance between the C and Mn contents and the Al content in the weld.

[0190] S8~S11, S47 and S48 involve butt welding of 1500MPa grade and 1500MPa grade materials, using three different welding wires, W1, W2 and W5, and three different welding wire filling amounts of 5%, 25% and 30% respectively.

[0191] Regarding weld composition, the welding wire composition, wire filler weight, and pre-plating thickness used in welds S8, S10, S11, S47, and S48 all fall within the ranges recommended by the present invention. Therefore, despite slight differences in the specific values ​​of these parameters, the weld alloy compositions meeting the requirements of the present invention are achieved. The carbon content in welds S8, S10, S11, S47, and S48, measured by weight percentage, ranges from 0.23 to 0.29 wt.%, the manganese content ranges from 1.22 to 1.51 wt.%, and the aluminum content ranges from 0.35 to 0.85 wt.%. Calculation of the evaluation factor FA reveals that the requirement of 10% ≤ FA ≤ 30% (10 ≤ FB ≤ 30) is met.

[0192] In contrast, although S9 uses wire W2 and a 5% filler, its pre-plating thickness is too thick, resulting in a high Al content of 1.03 wt.% entering the weld seam, which does not meet the requirements of the present invention. Calculation of the evaluation factor FA reveals a value of -2.6071%, also failing to meet the requirements of the present invention.

[0193] In terms of weld performance, hardness measurements showed that the weld hardness of S8, S10, S11, S47, and S48 was greater than that of the T2 base material. Static tensile testing revealed that all specimens fractured from the T2 base material. Furthermore, observations of hydrogen-induced delayed cracking revealed that the S8, S10, S11, S47, and S48 specimens all initially cracked from the T2 base material. Therefore, the weld performance of S8, S10, S11, S47, and S48 met the requirements.

[0194] In contrast, the excessively high aluminum content in S9 resulted in the presence of ferrite in the weld after hot stamping, which reduced the strength and hardness of the weld. The specimen broke from the weld during the static tensile test, failing to meet the weld performance requirements and eliminating the need for subsequent hydrogen-induced delayed cracking evaluation.

[0195] S12 to S14 also involve butt welding of 1500 MPa grade materials to 1500 MPa grade materials, but S12 and S13 use larger wire filling amounts that do not fall within the scope recommended by the present invention, and S14 uses a comparative wire W3 whose composition does not fall within the recommended scope of the present invention.

[0196] It can be seen from S12 and S13 that when W1 and W2 welding wires are used and the welding wire filling amount is increased to 35%, the C and Mn contents in the weld both increase, which in turn increases the hardness and strength of the weld. The average hardness of the weld reaches 529HV and 574HV, respectively, which is much greater than the average hardness of the substrate. At this time, the strength of the weld is greater than the strength of the substrate, so the specimen breaks from the T2 substrate during static tension. Despite the excellent strength, the S12 and S13 welds have poor resistance to hydrogen-induced delayed cracking, and the cracking location is in the weld. This is because the Al content in the weld is relatively low. Calculation shows that FA>30%, which does not meet the requirements of the present invention. In other words, the amount of Al contained in the S12 and S13 welds is not enough to achieve a good match with C and Mn, and cannot fully exert the role of Al in improving the toughness of the weld and improving resistance to hydrogen-induced cracking.

[0197] S14 uses comparative welding wire W3, which has higher carbon and manganese contents. Even with a 25% filler, high carbon and manganese contents are achieved in the weld. Although weld S14 exhibits greater hardness and strength than base material T2, its resistance to hydrogen-induced delayed cracking is poor, with cracking occurring in the weld. Calculation shows FA = 31.8601%, which does not meet the present invention's requirement of 10% ≤ FA ≤ 30%.

[0198] S16-S19, S40, S42, and S43 involve butt welding of 2000MPa-grade and 2000MPa-grade materials, using three different welding wires, W1, W2, and W5, respectively, and varying wire filler amounts of 5%, 20%, 25%, and 30%. Regarding weld composition, since the wire composition, wire filler amount, and pre-plating thickness of the steel sheets used in S16-S19, S40, S42, and S43 are all within the ranges recommended by the present invention, despite slight differences in the specific values ​​of the parameters, all achieve weld alloy compositions that meet the requirements of the present invention. The measured carbon content in welds S16-S19, S40, S42, and S43 ranges from 0.32 to 0.36 wt.%, the manganese content ranges from 1.20 to 1.32 wt.%, and the aluminum content ranges from 0.39 to 0.89 wt.%. Substituting the formula to calculate FA or FB, it can be seen that both meet the requirements of the present invention of 10%≤FA≤32% or 10≤FB≤32.

[0199] In terms of weld performance, hardness measurements showed that the weld hardness was greater than that of the T3 base material. Static tensile testing revealed that all specimens fractured from the T3 base material. Furthermore, observations of hydrogen-induced delayed cracking revealed that specimens S16-S19, S40, S42, and S43 all initially cracked from the T3 base material. Therefore, the weld performance of specimens S16-S19, S40, S42, and S43 met the requirements.

[0200] S15, S20~S24, S41, S49~S50 also involve butt welding of 2000MPa grade and 2000MPa grade materials, but S15 uses a smaller welding wire filling amount that does not fall within the scope recommended by the present invention, S20 uses a pre-plating thickness that does not fall within the scope recommended by the present invention, S21, S22, S41, S49, S50 use a larger welding wire filling amount that does not fall within the scope recommended by the present invention, and S23 and S24 use comparison welding wires W3 and W4 whose compositions do not fall within the recommended scope of the present invention.

[0201] For S15, due to the low filler wire content, the carbon content in the weld remained unchanged, reaching only 0.30 wt.%, which does not meet the requirements of the present invention. This resulted in the weld hardness being slightly lower than that of the base material, and therefore the weld strength being lower than that of the base material. In other words, the weld was not strengthened by the filler wire. During static tensile testing, the specimen broke through the weld.

[0202] For S20, due to the excessive pre-plating thickness, the amount of Al incorporated into the weld reached as high as 1.02 wt.%, failing to meet the requirements of the present invention. Calculation of the evaluation factor FA yielded a value of 9.0024%, also failing to meet the present invention's requirement of 10% ≤ FA ≤ 32%. Excessive aluminum content resulted in the presence of ferrite in the weld after hot stamping, reducing the weld's strength and hardness. The specimen fractured along the weld during static tensile testing, failing to meet weld performance requirements and omitting the need for subsequent hydrogen-induced delayed cracking evaluation.

[0203] As can be seen from S21, S22, and S41, when W1, W2, and W5 welding wires are used and the wire filling amount is increased to 35%, the C and Mn contents in the weld increase, which in turn increases the hardness and strength of the weld. The average hardness of the weld reaches 622HV, 637HV, and 624HV, respectively, which is much greater than the average hardness of the substrate. At this time, the strength of the weld is greater than the strength of the substrate, so the specimen breaks from the T3 substrate in the static tensile test. Despite excellent strength, the S21, S22, and S41 welds have poor resistance to hydrogen-induced delayed cracking, and the cracking location is in the weld. This is because the Al content in the weld is relatively low. Calculation shows that FA>32%, which does not meet the requirements of the present invention. In other words, the amount of Al contained in the S21, S22, and S41 welds is insufficient to achieve a good match with C and Mn, and cannot fully exert the role of Al in improving the toughness of the weld and improving resistance to hydrogen-induced cracking.

[0204] As shown in S49 and S50, when using a T4 base material and a W5 wire with a wire weight of 40% to 45%, the carbon content in the weld increases to over 0.4 wt%. This increase in carbon content effectively improves the weld strength, and the weld specimen fractured from the T4 base material during a static tensile test. However, since the weld carbon content exceeds 0.4 wt%, it does not meet the requirements of the present invention, resulting in poor resistance to hydrogen-induced delayed cracking and cracking in the weld.

[0205] S23 uses comparative welding wire W3, which has higher carbon and manganese contents. Even with a 25% filler, high carbon and manganese contents are achieved in the weld. Although the hardness and strength of weld S23 exceed those of base material T3, its resistance to hydrogen-induced delayed cracking is poor, with cracking occurring in the weld. Calculation shows FA = 36.5801%, which does not meet the present invention's requirement of 10% ≤ FA ≤ 32%.

[0206] The S24 used a comparative welding wire, W4, which has low carbon and manganese contents, which can lead to insufficient weld reinforcement and substandard hardness. During static tensile testing, the specimen broke through the weld.

[0207] S25-S30 involve butt welding of steel plates of equal thickness and different strength grades. Using the welding wires W1 and W2 and the recommended filler weights recommended by the present invention, weld alloy compositions meeting the requirements of the present invention were achieved. As shown in Table 5, for each combination, static tensile testing, hardness testing, and hydrogen-induced delayed cracking testing demonstrated that weld performance met the requirements.

[0208] S31-S34 involve butt welding of steel plates of different thicknesses and strength grades, specifically the butt welding of 1.8mm thick, 1000MPa-grade material T1 and 1.4mm thick, 1500MPa-grade material T2. Table 2 shows that the yield strength of T1 is 920MPa, and the yield strength of T2 is 1192MPa. Calculation shows that the two steel plates to be welded satisfy the following equation: T1 × YS1 ≥ 0.9 × T2 × YS2, where YS1 and T1 are the yield strength and thickness of the 1.8mm thick material T1, and YS2 and T2 are the yield strength and thickness of the 1.4mm thick material T2.

[0209] S31 and S32 adopt the welding wire composition, welding wire filling amount and pre-plating thickness suggested by the present invention, and realize the alloy composition required by the present invention. 焊缝0.2 The base material hardness is greater than 1500MPa. In static tensile testing, the specimen broke from the T2 base material. Delayed hydrogen-induced cracking was observed, and the cracking location was in the base material. Therefore, the weld performance of S31 and S32 meets the requirements.

[0210] S33 and S34 use comparative welding wires W3 and W4 that do not fall into the composition recommended by the present invention. For S33, although its hardness and strength can meet the requirements, the calculated evaluation factor FA value is 27.3401%, which does not meet the requirement of 10%≤FA≤25% of the present invention. The hydrogen-induced delayed cracking is observed, and the cracking location is in the weld. The comparative welding wire W4 used by S34 has low C and Mn contents, which easily leads to insufficient weld strengthening, resulting in substandard hardness. Even in the case of a large amount of welding wire filling, HV 焊缝0.2 It is only 440HV, which cannot meet the HV 焊缝0.2 The hardness of the substrate is greater than T2. ​​The specimen breaks from the weld in the static tensile test and does not meet the weld performance requirements. No subsequent hydrogen-induced delayed cracking evaluation is required.

[0211] S35-S38 involve butt welding of steel plates of different thicknesses and strength grades, specifically the butt welding of 1.7mm, 1500MPa material T2 and 1.4mm, 2000MPa material T3. Table 2 shows that the yield strength of T2 is 1192MPa, and the yield strength of T3 is 1350MPa. Calculation shows that the two steel plates to be welded meet the following conditions: T1×YS1≥0.9×T2×YS2, where YS1 and T1 are the yield strength and thickness of the 1.7mm material T2 to be welded, and YS2 and T2 are the yield strength and thickness of the 1.4mm material T3 to be welded.

[0212] S35 and S36 adopt the welding wire composition, welding wire filling amount and pre-plating thickness suggested by the present invention, and realize the alloy composition required by the present invention. 焊缝0.2 The hardness is greater than that of the T3 base material. In static tensile testing, the specimen broke from the T3 base material. Observed hydrogen-induced delayed cracking was located in the base material. Therefore, the weld performance of S35 and S36 meets the requirements.

[0213] S37 and S38 used comparative welding wires W3 and W4 that did not fall into the composition recommended by the present invention. For S37, although its hardness and strength can meet the requirements, the calculated evaluation factor FA value is 34.3509%, which does not meet the requirement of 10%≤FA≤30% of the present invention. The hydrogen-induced delayed cracking was observed, and the cracking location was in the weld. The comparative welding wire W4 used by S38 has low C and Mn contents, which easily leads to insufficient weld strengthening, resulting in substandard hardness. The hardness test shows that its HV 焊缝0.2 It is only 537HV, which cannot meet the HV 焊缝0.2 The hardness of the substrate is greater than T3. The specimen breaks from the weld in the static tensile test and does not meet the weld performance requirements. No subsequent hydrogen-induced delayed cracking evaluation is required.

[0214] As can be seen from the above, the weld alloy composition of the present invention can effectively handle the welding of steels of equal strength, different strengths, equal thickness, and different thicknesses, achieving reliable welds with excellent strength, toughness, and resistance to hydrogen-induced cracking. Furthermore, the solution of the present invention can be implemented at a low cost.

[0215] The above embodiments and experimental data are intended to illustrate the present invention by way of example. It should be clear to those skilled in the art that the present invention is not limited to these embodiments, and various modifications may be made without departing from the scope of protection of the present invention.

Claims

1. A hot stamping component, comprising: A first coated steel plate having a first coating layer thereon; a second coated steel plate having a second coating layer thereon; as well as a weld connecting the first coated steel sheet to the second coated steel sheet, Wherein, the weld has a weld evaluation factor FA=10Mn 焊缝 +77C 焊缝 -1900Al 焊 缝 2 -12Al 焊缝 , where Mn 焊缝 , C 焊缝 、Al 焊缝 are the manganese, carbon and aluminum contents in the weld in weight percentage, The alloy composition of the weld and the weld evaluation factor FA satisfy the following conditions: 1.0wt.%≤Mn 焊缝 ≤3.0wt.%, preferably 1.0wt.%≤Mn 焊缝 ≤2.5wt.% 0.3wt.%≤Al 焊缝 ≤1.0wt.%, preferably 0.4wt.%≤Al 焊缝 ≤0.8wt.%, and (a) at 0.27 wt.% <C 基材 When ≤0.38wt.%, the following conditions are met: 0.32wt.%≤C 焊缝 ≤0.4wt.%, C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.06wt.%; and 10%≤FA≤32%, preferably 10%≤FA≤30%; (b) at 0.15 wt.% <C 基材 ≤0.27wt.%, meets the following conditions: 0.19wt.%≤C 焊缝 ≤0.32wt.%, preferably 0.19wt.%≤C 焊缝 ≤0.29wt.% C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.11wt.%, preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.1wt.%, and 10%≤FA≤30%, preferably 10%≤FA≤26%; or (c) 0.05wt.% <C 基材 When ≤0.15wt.%, the following conditions are met: 0.05wt.%≤C 焊缝 ≤0.32wt.%, preferably 0.05wt.%≤C 焊缝 ≤0.27wt.% C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.30wt.%, and 10%≤FA≤25%, preferably 10%≤FA≤22%; Wherein, when the tensile strength of the first coated steel sheet is different from that of the second coated steel sheet, C 基材 represents the carbon content of the first coated steel sheet and the second coated steel sheet with a relatively lower tensile strength; when the tensile strength of the first coated steel sheet and the second coated steel sheet is the same, C 基材 Indicates that either the first coated steel sheet or the second coated steel sheet The carbon content of .

2. The hot stamping formed component according to claim 1, wherein: The volume content of ferrite in the weld after hot stamping is not more than 5%, preferably not more than 2%.

3. The hot stamping formed component according to claim 1 or 2, wherein: After hot stamping, the hardness of the weld meets the following conditions: (a) When the first coated steel sheet and the second coated steel sheet have the same tensile strength level, HV 焊缝 ≥HV 基材 ; (b) When T1×YS1≥0.9×T2×YS2, HV 焊缝0.2 ≥HV 高 强度基材 ; (c) When T1×YS1<0.9×T2×YS2, HV 焊缝 ≥HV 低强度基材 ; Wherein, YS1 is the yield strength of the first coated steel plate and the second coated steel plate with a lower yield strength, T1 is the thickness of the first coated steel plate and the second coated steel plate with a lower yield strength, YS2 is the yield strength of the first coated steel plate and the second coated steel plate with a higher yield strength, T2 is the thickness of the first coated steel plate and the second coated steel plate with a higher yield strength, HV 焊缝 HV is the hardness of the weld after hot stamping. 基材 is the hardness of the first coated steel sheet or the second coated steel sheet after hot stamping, HV 高强度基材 HV is the hardness of the first coated steel sheet and the second coated steel sheet with a higher yield strength after hot stamping, 焊缝0.2 HV is the hardness within 0.2 mm from the weld fusion line on the side of the first coated steel sheet and the second coated steel sheet with higher yield strength after hot stamping, 低强度基材 It is the hardness of the one with lower yield strength between the first coated steel sheet and the second coated steel sheet after hot stamping.

4. A laser welded component, comprising: A first pre-plated steel plate, on which a first pre-plated layer composed of aluminum or an aluminum alloy is provided; A second pre-plated steel plate having a second pre-plated layer of aluminum or an aluminum alloy; and a weld connecting the first pre-plated steel sheet to the second pre-plated steel sheet, Wherein, the weld has a weld evaluation factor FA=10Mn 焊缝 +77C 焊缝 -1900Al 焊 缝 2 -12Al 焊缝 , where Mn 焊缝 , C 焊缝 、Al 焊缝 are the manganese, carbon and aluminum contents in the weld in weight percentage, The alloy composition of the weld and the weld evaluation factor FA satisfy the following conditions: 1.0wt.%≤Mn 焊缝 ≤3.0wt.%, 0.3wt.%≤Al 焊缝 ≤1.0wt.%, and (a) at 0.27 wt.% <C 基材 When ≤0.38wt.%, the following conditions are met: 0.32wt.%≤C 焊缝 ≤0.4wt.%, C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.06wt.%; and 10%≤FA≤32%, preferably 10%≤FA≤30%; (b) at 0.15 wt.% <C 基材 ≤0.27wt.%, meets the following conditions: 0.19wt.%≤C 焊缝 ≤0.32wt.%, preferably 0.19wt.%≤C 焊缝 ≤0.29wt.% C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.11wt.%, preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.1wt.%, and 10%≤FA≤30%, preferably 10%≤FA≤26%; or (c) 0.05wt.% <C 基材 When ≤0.15wt.%, the following conditions are met: 0.05wt.%≤C 焊缝 ≤0.32wt.%, preferably 0.05wt.%≤C 焊缝 ≤0.27wt.% C 基材 +0.01wt.%≤C 焊缝 , preferably, C 基材 +0.01wt.%≤C 焊缝 ≤C 基材 +0.30wt.%, and 10%≤FA≤25%, preferably 10%≤FA≤22%; Wherein, when the tensile strength of the first pre-plated steel sheet is different from that of the second pre-plated steel sheet, C 基材 represents the carbon content of the first pre-plated steel sheet and the second pre-plated steel sheet with relatively lower tensile strength; when the tensile strength of the first pre-plated steel sheet is the same as that of the second pre-plated steel sheet, C 基材 represents the carbon content of either the first pre-plated steel sheet or the second pre-plated steel sheet; Wherein, the thickness of the first pre-plating layer and / or the second pre-plating layer is 6 μm to 19 μm, preferably 8 μm to 16 μm, preferably 10 μm to 16 μm.

5. The laser-welded component according to claim 4, wherein: The thickness of the first pre-plated steel sheet and / or the second pre-plated steel sheet is 0.8 to 3.0 mm, preferably 1.0 to 2.5 mm.

6. The laser-welded component according to claim 4 or 5, wherein: The alloy composition of the weld includes: 1.0wt.%≤Mn 焊缝 ≤2.5wt.%.

7. The laser-welded component according to claim 4 or 5, wherein: The alloy composition of the weld includes: 0.4wt.%≤Al 焊缝 ≤0.8wt.%.

8. A welding wire for laser welding of aluminum or aluminum alloy pre-plated steel plates, comprising the following components in weight percentage: C: 0.30-0.45wt.%, Mn: 1.0-3.0wt.%; preferably C: 0.35-0.45wt.%, Mn: 1.5-2.5wt.%.

9. The welding wire according to claim 8, wherein: The hardness of the welding wire is less than 300 HV.

10. A laser welding method for forming a laser-welded component according to any one of claims 4 to 7, wherein: During laser welding, a welding wire is used which includes the following components in weight percentage: C: 0.30~0.45wt.%, Mn: 1.0~3.0wt.%; preferably C: 0.35~0.45wt.%, Mn: 1.5~2.5wt.%; during welding, the butt gap between the first pre-coated steel plate and the second pre-coated steel plate is 0~0.5mm.

11. The laser welding method according to claim 10, wherein: The welding wire filling amount is 5-30%.

12. A method for producing a hot stamping formed component, comprising the following steps: A) providing a laser-welded component according to any one of claims 4 to 7; B) Complete austenitization treatment: heating the laser welded component in step A) to above 900° C. and keeping the temperature; C) Hot stamping process: After completing step B), the heated laser welded component is transferred to a press for thermal deformation and cooled to below 300° C. in a die to obtain a hot stamping component.

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