Welding wire and welding method

Abstract

The invention relates to a welding wire and a welding method, and belongs to the technical field of welding. The welding wire comprises the following chemical components: C, Mn, Ni, Cr, Si, Mo, a matrix element Fe and inevitable impurities. X = [Cr] + [Mo] + 1.5 [Si], y = [Ni] + 30 [C] + 0.5 [Mn], and in the formula, [Cr], [Mo], [Si], [Ni], [C] and [Mn] represent mass fractions of corresponding elements in the welding wire respectively; wherein x and y simultaneously meet the following three inequalities: 0.15 < = x < = 0.25,-0.777 x + 0.25 < = y < =-0.777 x + 0.4, and y > = 1.103 x-0. 083.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a welding wire and a welding method. BACKGROUND

[0002] Multi-component integration of hot-formed steel is one of the important ways to improve the crash safety of the vehicle body, realize lightweight and reduce the manufacturing cost. The implementation process usually includes: first, the hot-formed steel is tailor-welded, then the whole is heated to above the austenitizing temperature for hot stamping, and if necessary, a patch plate is welded before heating.

[0003] In the above process, since the aluminum plating layer plays a role in preventing oxidation during hot forming, and the removal process increases the cost and complexity, the welding process is usually carried out in its retained state. As a strong ferrite-forming element, aluminum is easy to promote the precipitation of δ-ferrite in the welding pool, which destroys the microstructure uniformity of the weld metal and leads to the decrease of strength and toughness. In order to suppress this tendency, high-alloy welding wire needs to be used to stabilize the austenite structure. However, although the elements such as Ni, Mo and Cr added to suppress ferrite can improve the performance of the weld, they significantly increase the hardening rate of the welding wire, leading to drawing cracking, increased die wear and decreased manufacturing yield. Therefore, how to balance the contradiction between "suppressing aluminum-induced ferrite" and "ensuring the processing performance of the welding wire" in the alloy composition design is a core problem in the current development of welding wire. SUMMARY

[0004] The present application provides a welding wire and a welding method to solve the technical problem of how to improve the drawing performance of the welding wire. In a first aspect, the embodiments of the present application provide a welding wire, the chemical composition of the welding wire comprising C, Mn, Ni, Cr, Si, Mo, and base element Fe and unavoidable impurities; Definition: x = [Cr] + [Mo] + 1.5[Si], y = [Ni] + 30[C] + 0.5[Mn], wherein [Cr], [Mo], [Si], [Ni], [C] and [Mn] represent the mass fraction of the corresponding element in the welding wire. Wherein, the x and y simultaneously satisfy the following three inequalities: 0.15≤x≤0.25, -0.777x+0.25≤y≤-0.777x+0.4 and y≥1.103x-0.083.

[0005] Optionally, the chemical composition of the welding wire satisfies: [C]≤0.05%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, [Mo]≤5% in terms of mass fraction.

[0006] Optionally, the chemical composition of the welding wire satisfies: [C]≤0.03%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, [Mo]≤5%, [P]≤0.03%, [S]≤0.03% in mass fraction.

[0007] Optionally, the chemical composition of the welding wire further contains alloy elements Ti and La, and the chemical composition satisfies: [C]≤0.03%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, 2%≤[Mo]≤5%, 0.06%≤[Ti]≤0.3%, 0.005%≤[La]≤0.3%, [P]≤0.03%, [S]≤0.03% in mass fraction.

[0008] Optionally, the volume fraction of austenite in the microstructure of the welding wire in the drawn finished state is ≥90%.

[0009] In a second aspect, the application provides a laser welding method for welding at least two aluminum-plated hot-formed steels, the method comprising: aligning the sides to be spliced of the at least two aluminum-plated hot-formed steels along the same plane, and forming a continuous splicing gap between the sides to be spliced; using the welding wire in the first aspect as a filler material to laser weld the splicing gap, so that the welding wire and the at least two aluminum-plated hot-formed steels melt and solidify together at the splicing gap to form a continuous weld seam, to obtain a welded blank containing the weld seam; subjecting the welded blank to heat treatment, so that the weld seam and the aluminum-plated hot-formed steels undergo phase transition synchronously, to obtain a laser-welded part containing the weld seam.

[0010] Optionally, the width of the splicing gap h≤0.19mm.

[0011] Optionally, the dilution rate D of the laser welding satisfies: 65%≤D≤90%, wherein the dilution rate D=(aluminum-plated hot-formed steel melting area) / (weld seam cross-sectional area)×100%, and the aluminum-plated hot-formed steel melting area and the weld seam cross-sectional area are measured on a polished metallographic section perpendicular to the welding direction.

[0012] Optionally, the tensile fracture position of the laser-welded part is located at the aluminum-plated hot-formed steel of the laser-welded part, rather than at the weld seam of the laser-welded part.

[0013] Optionally, the aluminum-containing plated hot forming steel includes a hot forming steel base and an aluminum-containing plated layer; when [C] of the hot forming steel base is greater than or equal to 0.3% in mass fraction, the chemical composition of the welding wire is controlled as follows: [C] is less than or equal to 0.02%, 4% is less than or equal to [Mn] and is less than or equal to 8%, 16% is less than or equal to [Ni] and is less than or equal to 20%, 11% is less than or equal to [Cr] and is less than or equal to 16%, [Si] is less than or equal to 1.2%, 2% is less than or equal to [Mo] and is less than or equal to 5%, 0.06% is less than or equal to [Ti] and is less than or equal to 0.3%, 0.005% is less than or equal to [La] and is less than or equal to 0.3%, [P] is less than or equal to 0.03%, [S] is less than or equal to 0.03%, and the balance is Fe and inevitable impurities.

[0014] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art: The embodiments of the present application provide a welding wire, which synchronously controls the austenite-martensite phase change driving force and dislocation mobility through component design to reduce the wire drawing hardening rate from the source: on the one hand, the supercooled austenite stability of the welding wire is controlled by x=Cr+Mo+1.5Si: Cr, Mo and Si improve the hardenability of the welding wire in the range of 0.15≤x≤0.25, so that full martensite is generated in the heat-affected zone of the welding wire, and the strain concentration of the mixed structure on the surface of the welding wire is inhibited; the upper limit of x is 0.25, which blocks the formation of excessive Cr-Al and Mo-Al brittle phases on the surface of the welding wire in the Al plating process, reduces the grain boundary embrittlement of the welding wire, and reduces the crack source density of the welding wire in the subsequent drawing; secondly, the dislocation cross-slip ability of the welding wire is optimized by y=Ni+30C+0.5Mn: Ni reduces the stacking fault energy of the welding wire, accelerates the dislocation cross-slip and dynamic recovery of the welding wire; C is solid-solved in the welding wire base at an interval of 30 times the weight, which improves the strength of the welding wire, and the upper limit of y≤-0.777x+0.4 prevents the network precipitation of carbides at the grain boundary of the welding wire; Mn expands the gamma zone of the welding wire and takes into account the hardenability and deoxidation, and excessive Mn will increase the work hardening of the welding wire, and the lower limit of y≥1.103x-0.083 provides sufficient solid solution strengthening to offset the hardening increment introduced by Cr-Mo in the welding wire; finally, the three linear constraints form a "component window" of the welding wire, so that Δy / Δx≈-0.777, for every 1 unit of Cr-Mo-Si hardening contribution, the Ni-C-Mn combination reduces the work hardening index of the welding wire by about 0.777 units; as a result, under the strength of 1.2 GPa, the reduction of area of the welding wire fracture is increased by 8% to 10%, the drawing pass of the welding wire is reduced from 12 to 8, the wire breaking rate of the welding wire is less than 0.3 times per ton, and high-speed drawing of the welding wire is realized. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the present application.

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0017] Figure 1 A flowchart of a laser welding method for an aluminum-containing plated hot-formed steel provided by the embodiment of the present application is shown in the figure. Figure 2 A tensile fracture position diagram of a weld seam area of a laser welded part provided by the embodiment 1 of the present application is shown in the figure. Figure 3 A tensile fracture position diagram of a weld seam area of a laser welded part provided by the embodiment 2 of the present application is shown in the figure. Figure 4 A hydrogen embrittlement four-point bending test result diagram of a weld seam area of a laser welded part provided by the embodiment 1 of the present application is shown in the figure. DETAILED DESCRIPTION

[0018] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0019] The range descriptions described herein, such as numerical ranges, ratio ranges, etc., all include all possible sub-ranges and single values within the range, for example, the range description of “1 to 6” or “1-6” covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms “include”, “contain” and the like used herein mean “include but not limited to”; the relationship terms “first”, “second” and the like are only used to distinguish different entities or operations, and do not imply actual sequence or relationship; “and / or” means that multiple cases can exist independently or simultaneously; “at least one”, “multiple” and “at least one” and the like refer to any combination of the corresponding objects, including single or multiple combinations of the objects. The proportional relationships involved herein, such as mass ratio, molar ratio, etc., should be understood as the corresponding relationship between the front and the rear in the proportional form according to the sequence of description. The raw materials, reagents, instruments and equipment used herein can be purchased from the market or prepared by existing methods.

[0020] In the present application, the splicing gap specifically refers to a continuous splicing gap formed between the sides to be spliced of at least two pieces of the aluminum-plated hot-formed steel, and the maximum width of the continuous splicing gap is determined by the mechanical alignment operation on the at least two pieces of aluminum-plated hot-formed steel.

[0021] The dilution rate D is defined as follows: a polished metallographic section perpendicular to the welding direction is detected on the weld, the aluminum-plated hot-formed steel melting area and the weld cross-sectional area are obtained, the aluminum-plated hot-formed steel melting area and the weld cross-sectional area are calculated by ratio and multiplied by 100%, and the dilution rate D is obtained, the numerical range of which is controlled by the welding speed and the wire feeding speed.

[0022] The weld refers to a continuous metal area formed by the co-melting and solidification of the welding wire and the aluminum-plated hot-formed steel at the splicing gap.

[0023] In a first aspect, the embodiments of the present application provide a welding wire, and the chemical composition of the welding wire comprises C, Mn, Ni, Cr, Si, Mo, and base element Fe and unavoidable impurities. Definition: x = [Cr] + [Mo] + 1.5[Si], y = [Ni] + 30[C] + 0.5[Mn], wherein [Cr], [Mo], [Si], [Ni], [C] and [Mn] represent the mass fraction of the corresponding element in the welding wire. Wherein, the x and y simultaneously satisfy the following three inequalities: 0.15≤x≤0.25, -0.777x+0.25≤y≤-0.777x+0.4 and y≥1.103x-0.083.

[0024] By precisely regulating the mass fraction of each alloying element in the chemical composition of the welding wire, the chemical composition of the welding wire satisfies the inequalities 0.15≤x≤0.25, -0.777x+0.25≤y≤-0.777x+0.4 and y≥1.103x-0.083, so as to construct a microstructure dominated by austenite in the drawn finished state of the welding wire. When the parameter x is stabilized in the interval of 0.15-0.25, the interval corresponds to the widest full-austenite process window, significantly inhibiting the formation tendency of ferrite or martensite. The high plasticity and toughness of the austenite phase endow the welding wire with excellent deformation capability, so that the welding wire can withstand higher pass compression rate during the drawing process, realizing efficient non-wire-breaking forming. Within the optimized interval of 0.15≤x≤0.25, the chemical composition of the welding wire further introduces double lower limit constraints: y≥-0.777x+0.25 and y≥1.103x-0.083 (i.e., when x=0.15, y≥0.133; when x=0.25, y≥0.193), forming an austenite locking region of the chemical composition of the welding wire, ensuring that the volume fraction of austenite in the welding wire is ≥90% at any x value. At the same time, in order to prevent the weld formed by the welding wire from softening due to excessive residual austenite during the subsequent hot stamping process, the upper limit of y value is set by y≤-0.777x+0.4, precisely controlling the total amount of austenite stabilizing elements within a safe threshold, realizing the synergistic optimization of strength-toughness-processability of the welding wire. The mass fraction of the base element Fe in the welding wire is determined by the following rules: (1) the sum of the mass fractions of all components in the chemical composition of the welding wire is equal to 100%; (2) the sum of the upper limit value of any component in the chemical composition of the welding wire and the lower limit value of the remaining components is ≤100%; (3) the sum of the lower limit value of any component in the chemical composition of the welding wire and the upper limit value of the remaining components is ≥100%; (4) the mass fraction of Fe in the welding wire is supplemented to 100% by the actual detection value of each element in the chemical composition of the welding wire which has been explicitly specified and the mass fraction of active elements and unavoidable impurity elements not listed.

[0025] In some embodiments, the chemical composition of the welding wire satisfies: [C]≤0.05%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, [Mo]≤5% in terms of mass fraction.

[0026] The C element mass fraction [C], the Ni element mass fraction [Ni], and the Mn element mass fraction [Mn] of the welding wire are set in a composition interval, and the welding wire simultaneously obtains the following four effects: austenite stabilization effect, strength-toughness matching effect, dilution rate balance effect, and corrosion resistance improvement effect. 1. Austenite stabilization effect: the nickel equivalent y of the welding wire is calculated as y = [Ni] + 30[C] + 0.5[Mn], and the y value is directly given by the mass fraction of [C], [Ni], and [Mn] in the welding wire; the higher the y value, the wider the austenite zone of the welding wire, and the Al-induced ferrite tendency of the welding wire in the laser welding pool is inhibited. 2. Strength-toughness matching effect: the C element improves the strength of the weld formed by the welding wire, but at the same time reduces the toughness of the weld; the Ni element improves the strength of the weld while improving the toughness of the weld; the effect of the Mn element on the strength-toughness of the weld is between that of the C element and the Ni element. Therefore, the welding wire adopts the "low [C] + high [Mn] + high [Ni]" strategy, so that the weld maintains high strength while retaining sufficient toughness. 3. Mutual dilution balance effect when laser welding with an aluminum-plated hot-formed steel base: compared with the welding wire, the typical C element mass fraction of the aluminum-plated hot-formed steel base is high: the C element mass fraction of the 1500 MPa aluminum-plated hot-formed steel base is about 0.22%, and the C element mass fraction of the 2000 MPa aluminum-plated hot-formed steel base is about 0.34%; the Mn element mass fraction and the Ni element mass fraction of the aluminum-plated hot-formed steel base are low. The C element mass fraction of the welding wire is much lower than that of the aluminum-plated hot-formed steel base, and the Mn element mass fraction and the Ni element mass fraction of the welding wire are much higher than those of the aluminum-plated hot-formed steel base. When laser welding, the metal of the welding wire and the metal of the aluminum-plated hot-formed steel base are mixed at a dilution rate of 65% to 90%, the C element mass fraction of the weld is diluted to be lower than that of the aluminum-plated hot-formed steel base, and the Mn element mass fraction and the Ni element mass fraction of the weld are increased to be higher than those of the aluminum-plated hot-formed steel base, thereby inhibiting the austenite residue caused by the simultaneous increase of [C], [Ni], and [Mn] and ensuring the strength of the weld. 4. Corrosion resistance improvement effect: the Cr element mass fraction [Cr] of the welding wire is in the range of 11% to 16%, which improves the strength of the weld and enhances the corrosion resistance of the weld; when [Cr] > 16%, the ferrite stability of the weld increases, the proportion of martensite in the weld decreases, and the strength of the weld decreases accordingly, so the upper limit of [Cr] is set to 16%.

[0027] In some embodiments, the chemical composition of the welding wire satisfies: [C]≤0.03%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, [Mo]≤5%, [P]≤0.03%, [S]≤0.03% in mass fraction.

[0028] The mass fraction of C element [C] of the welding wire is further pressed to ≤0.03% in mass fraction, which directly reduces the hardness of the weld formed by the welding wire and reduces the grain boundary carbide of the weld, so that the toughness of the weld is improved; the mass fraction of Mn element [Mn] of the welding wire is kept in the interval of 4% to 15%, which compensates for the strength loss of the weld caused by the reduction of [C] through solid solution strengthening; the mass fraction of Ni element [Ni] of the welding wire is kept in the interval of 10% to 20%, which simultaneously improves the tensile strength of the weld and the impact toughness of the weld, and offsets the strength fluctuation of the weld caused by the reduction of [C]. The above-mentioned composition combination of [C], [Mn] and [Ni] makes the weld metal maintain high tensile strength while improving the impact energy of the weld metal at –40°C.

[0029] In some embodiments, the chemical composition of the welding wire further contains alloy elements Ti and La, and the chemical composition satisfies: [C]≤0.03%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, 2%≤[Mo]≤5%, 0.06%≤[Ti]≤0.3%, 0.005%≤[La]≤0.3%, [P]≤0.03%, [S]≤0.03% in mass fraction.

[0030] The Ti element is added in the welding wire with a mass fraction of [Ti] 0.06% to 0.3%. The [Ti] range improves the fluidity of the molten pool formed in the laser welding process of the welding wire, and facilitates the uniform distribution of chemical elements in the molten pool. On the one hand, the [Ti] range suppresses the local enrichment of Al elements from the aluminum-containing plated hot-formed steel coating in the molten pool, blocks the precipitation of high-temperature ferrite, thereby avoiding the reduction of the strength of the weld formed after the solidification of the molten pool; on the other hand, the [Ti] range promotes the fusion of the welding wire and the aluminum-containing plated hot-formed steel base, avoids the local segregation of the components of the welding wire in the molten pool, and avoids the generation of austenite, thereby avoiding the reduction of the strength of the weld. In addition, the [Ti] range forms dispersed carbides in the weld, which adsorb hydrogen atoms and act as hydrogen traps. When the component of the welding wire is set as [Ti] > 0.3%, large-size oxide inclusion defects are generated in the weld; when the component of the welding wire is set as 0.06% ≤ [Ti] ≤ 0.3%, the weld has no large-size oxide inclusions. The La element is added in the welding wire with a mass fraction of [La] 0.005% to 0.3%. The [La] range significantly improves the performance of the welding wire. The La element refines the grains of the weld, forms fine grain boundaries, hinders the diffusion path of hydrogen atoms in the weld, thereby reducing the hydrogen embrittlement risk of the weld; the La element also forms compounds with other elements in the weld to generate irreversible hydrogen traps, further reducing the hydrogen embrittlement risk of the weld. When the component of the welding wire is set as [La] < 0.005%, the grains of the weld are not refined and the number of hydrogen traps is insufficient; when the component of the welding wire is set as 0.005% ≤ [La] ≤ 0.3%, the grains of the weld are refined and the number of hydrogen traps is sufficient; when the component of the welding wire is set as [La] > 0.3%, the casting blank of the welding wire is prone to cracks in the forging link, and the welding wire is prone to breakage in the drawing and welding links.

[0031] In some embodiments, the volume fraction of austenite in the microstructure of the welding wire in the drawn finished state is ≥ 90%.

[0032] The austenitic structure has excellent plasticity and toughness, while the strength is relatively low; the characteristics of the austenitic structure make the welding wire not easy to break during drawing, and improve the production quality stability of the welding wire. In the embodiments of the present application, the volume fraction of austenite in the microstructure of the welding wire in the drawn finished state is ≥ 90%; the volume fraction of austenite not only improves the drawing performance of the welding wire, but also reduces the difficulty of the welding wire straightening by the wire feeder of the welding equipment, and avoids that the welding wire has an arc when it is discharged. The welding wire itself is mainly austenitic; after the mutual fusion of the welding wire and the aluminum-containing plated hot forming steel matrix during the laser welding process, the austenite in the welding wire is transformed into martensite during the rapid cooling process; the transformation makes the microstructure of the weld formed by the mutual solidification of the welding wire and the aluminum-containing plated hot forming steel matrix mainly martensite, thereby improving the strength and hardness of the weld. For example, the volume fraction of austenite in the microstructure of the welding wire in the drawn finished state can be 90%, 92%, 94%, 96%, 98%, etc.

[0033] In summary, the welding wire provided by the embodiment of the present application has the characteristics of "low self-strength and high post-welding weld strength": 1. The microstructure of the welding wire in the drawn finished state is austenite, and the volume fraction of the austenite is greater than or equal to 90%. The austenite structure gives the welding wire excellent drawing performance, so that the wire feeder does not need to be additionally straightened, and the welding wire is ensured to be straight when it is discharged. The welding wire is fused with the aluminum-plated hot-formed steel matrix during laser welding, and after hot forming, the tensile fracture is located in the aluminum-plated hot-formed steel matrix, rather than in the weld. 2. The mass fraction of Ni element [Ni] and the mass fraction of Cr element [Cr] of the welding wire are both higher than the corresponding element mass fraction of the aluminum-plated hot-formed steel matrix. The [Ni] and [Cr] give the weld better corrosion resistance than the aluminum-plated hot-formed steel matrix. 3. When the wire feed amount increases, the proportion of the welding wire metal in the weld increases. If the mass fraction of C element [C] of the welding wire is higher than or close to the [C] of the aluminum-plated hot-formed steel matrix, the [C] of the weld also increases synchronously, which causes the hardness of the weld to exceed the standard and increases the hydrogen brittleness sensitivity. The [C] of the welding wire is limited to less than or equal to 0.03%, and the wire feed amount can be adjusted within the range of 65% to 90% dilution rate, while the [C] of the weld is kept at a low level, thereby avoiding the hardening and cold cracking of the weld. 4. The high [Ni], high [Mn] and low [C] design of the welding wire ensures the strength and toughness matching of the weld. 5. The mass fraction of Ti element [Ti] of the welding wire combines with the mass fraction of C element and N element to generate Ti(C, N) nano reversible hydrogen traps. The mass fraction of La element [La] of the welding wire combines with S element and O element to form La2O2S irreversible hydrogen traps, which significantly reduces the hydrogen-induced cracking probability of the weld. 6. The mass fraction of Cr element [Cr] and the mass fraction of Mo element [Mo] of the welding wire are jointly solid-solved in the martensite to improve the tempering resistance of the weld, so that the weld maintains a high strength during hot stamping, and prevents the weld from deforming and cracking at high temperature during hot forming.

[0034] Figure 1 A flowchart of a laser welding method for an aluminum-plated hot-formed steel provided by the embodiment of the present application is shown.

[0035] Please refer to Figure 1 , in the second aspect, the present application provides a laser welding method for an aluminum-plated hot-formed steel, which uses the welding wire in the first aspect for welding, and the method comprises the following steps: S1, aligning the to-be-welded sides of at least two pieces of the aluminum-plated hot-formed steel along the same plane, and forming a continuous joint gap between the to-be-welded sides; S2, laser welding the splicing gap using the welding wire in the first aspect as filler material, causing the welding wire and the at least two aluminum-containing plated hot-formed steels to co-melt and solidify at the splicing gap to form a continuous weld seam, to obtain a welded blank containing the weld seam; S3, heat treating the welded blank to cause the weld seam and the aluminum-containing plated hot-formed steels to undergo phase transition synchronously, to obtain a laser-welded part containing the weld seam.

[0036] In step S1, the splicing gap is the welding interface of the two aluminum-containing plated hot-formed steel blanks; the width of the splicing gap is controlled to be ≤0.19 mm, and the narrow splicing gap of ≤0.19 mm reduces the consumption of the welding wire, improves the laser welding speed, reduces the width of the heat-affected zone, and inhibits the generation of welding cracks. In step S2, the laser welding uses the low-C high-Ni welding wire of any one of claims 1-5, and the laser power density is >10 5 Wcm -2 The welding wire and the aluminum-containing plated hot-formed steel blanks are rapidly melted; the Ni element preferentially combines with the free Al element from the plating in the molten pool to form a NiAl phase, inhibiting the generation of Fe-Al brittle phases; the cooling rate of the molten pool is 10 3 ~10 4 Ks -1 , and the cooling rate refines the molten pool structure, provides a large number of nucleation sites for subsequent martensite phase transition, and ensures the hardness of the weld seam. In step S3, after austenitizing at a heat treatment temperature of 880-950℃, the welded blank is immediately subjected to die quenching at a cooling rate of ≥30 Ks -1 ; the weld seam and the aluminum-containing plated hot-formed steel blanks synchronously complete the martensite phase transition, the phase transition volume expansion offsets the welding residual tensile stress, and high (equal) strength and high toughness matching of the weld seam and the aluminum-containing plated hot-formed steel blanks is achieved.

[0037] An exemplary splicing scheme is as follows: 1. Splicing of two aluminum-containing plated hot-formed steels The first aluminum-containing plated hot-formed steel (material 22MnB5, thickness 1.6 mm) and the second aluminum-containing plated hot-formed steel (material 22MnB5, thickness 1.6 mm) are subjected to high-precision shearing on the side to be spliced, to obtain the sheared side to be spliced; The lower surfaces of the two aluminum-containing plated hot-formed steels after shearing are placed on the same plane and pushed against each other in the transverse direction to form a continuous splicing gap, and the width h of the splicing gap is ≤0.05 mm; the continuous splicing gap is subjected to laser welding using the welding wire of the present application as filler material, to obtain a welded blank containing a continuous weld seam; the welded blank is subjected to heat treatment, and after cooling, a laser-welded part is obtained, and the tensile strength of the laser-welded part is 1474 MPa, and the tensile fracture position is located in the aluminum-containing plated hot-formed steel blank.

[0038] 2. Four-piece aluminum-containing plated hot-formed steel "ring seam" welding A laser cutting is performed on a to-be-welded side of four-piece aluminum-containing plated hot-formed steel (material 22MnB5, thickness 2.0 mm) to obtain a cut to-be-welded side; a jig is used to position the four-piece aluminum-containing plated hot-formed steel, so that the lower surfaces of the four-piece aluminum-containing plated hot-formed steel are coplanar, and are fixed by means of an electromagnet to form four continuous welding gaps, the widths of the four continuous welding gaps are all ≤0.08 mm; a laser welding is performed on the four continuous welding gaps by using the welding wire as a filler material to obtain a welded blank containing a closed ring-shaped continuous weld, the welded blank is a door ring part; a heat treatment is performed on the welded blank, and a laser-welded part is obtained after cooling, the tensile strength of the laser-welded part is 1450 MPa, and the tensile fracture position is located in the aluminum-containing plated hot-formed steel base material.

[0039] In some embodiments, the width h of the welding gap is ≤0.19 mm.

[0040] Since the welding wire described in the embodiments contains the austenite stabilizing elements with mass fractions satisfying 0.15≤x≤0.25, –0.777x+0.25≤y≤–0.777x+0.4 and y≥1.103x–0.083, the austenite stabilizing elements including Ni, Mn and C, when the width of the welding gap is ≤0.19 mm, the chemical composition of the welding wire still inhibits the generation of Fe-Al brittle phase from the Al element in the aluminum-containing plated hot-formed steel plating into the laser welding molten pool. Controlling the width of the welding gap to be ≤0.19 mm can reduce the amount of melting of the welding wire in the laser welding process, thereby reducing the unit consumption and production cost of the welding wire, and at the same time making more laser energy used for melting the aluminum-containing plated hot-formed steel base material, and improving the production efficiency of laser welding. For example, the width h of the welding gap can be 0.05 mm, 0.07 mm, 0.09 mm, 0.11 mm, 0.13 mm, 0.15 mm, 0.17 mm, 0.19 mm, etc.

[0041] In some embodiments, the dilution rate D of the laser welding satisfies: 65%≤D≤90%, where the dilution rate D=(aluminum-containing plated hot-formed steel melting area) / (weld cross-sectional area)×100%, the aluminum-containing plated hot-formed steel melting area and the weld cross-sectional area are both measured on a polished metallographic section perpendicular to the welding direction.

[0042] The welding wire contains the austenite stabilizing elements satisfying 0.15≤x≤0.25, -0.777x+0.25≤y≤-0.777x+0.4, and y≥1.103x-0.083. The melting ratio of the aluminum-containing plated hot-formed steel parent material in the weld must satisfy D≥65%. When D<65%, the volume fraction of austenite in the weld metal increases, and the tensile strength of the weld decreases. For the aluminum-containing plated hot-formed steel parent material with a tensile strength level of 2 GPa, i.e., the mass fraction of C≥0.3%, the dilution rate D needs to be controlled in a narrower range of 75%≤D≤90% to further inhibit the formation of austenite in the weld. The melting ratio of the aluminum-containing plated hot-formed steel parent material in the weld cannot be higher than 90%. When D>90%, the proportions of Ni, Mn, and C elements in the austenite zone in the welding wire are too low in the weld metal, which cannot inhibit the Fe-Al brittle phase caused by the Al element, resulting in a decrease in the strength of the weld. In some embodiments, the dilution rate is controlled between 75% and 85%. For example, the dilution rate D of laser welding can be 65%, 70%, 75%, 80%, 85%, 90%, etc.

[0043] In some embodiments, the tensile fracture position of the laser welded part is located at the aluminum-containing plated hot-formed steel of the laser welded part, rather than at the weld of the laser welded part.

[0044] The martensite structure of the weld gives the weld high strength. Under the joint action of the composition of the welding wire and the welding method, the tensile fracture is ensured to be located at the aluminum-containing plated hot-formed steel parent material, rather than at the weld, and brittle fracture of the weld is avoided.

[0045] In some embodiments, the aluminum-containing plated hot-formed steel includes a hot-formed steel base and an aluminum-containing plated layer. When the mass fraction of [C] of the hot-formed steel base is ≥0.3%, the chemical composition of the welding wire is controlled as follows: [C]≤0.02%, 4%≤[Mn]≤8%, 16%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, 2%≤[Mo]≤5%, 0.06%≤[Ti]≤0.3%, 0.005%≤[La]≤0.3%, [P]≤0.03%, [S]≤0.03%, and the balance is Fe and unavoidable impurities.

[0046] When the mass fraction of C element in the hot-formed steel base body is greater than or equal to 0.3%, the chemical composition of the welding wire still meets the requirement that the tensile fracture position is located in the base body of the hot-formed steel with aluminum plating layer; in the chemical composition of the welding wire, the mass fraction of Fe element corresponds to 60%, 55% and 50% respectively under three specific proportions of the total mass fraction of alloying elements being 40%, 45% and 50%, and the volume fraction of austenite in the welding wire in the drawn finished state is greater than or equal to 90%; after laser welding is completed by using the welding wire with the above three proportions, the tensile strength of the weld is higher than that of the base body of the hot-formed steel with aluminum plating layer, and the tensile fracture position is always located in the base body of the hot-formed steel with aluminum plating layer.

[0047] The application will be further described below in combination with specific examples. The experimental methods not specified in the following examples are generally determined according to national standards / industry standards; if there is no corresponding national standard / industry standard, the general international standard, the conventional condition or the condition suggested by the manufacturer is used.

[0048] Example 1 In this example, a welding wire for hot-formed steel with aluminum plating layer is provided, with a diameter of 1.0 mm, and the components include, in mass fraction: C: 0.007%; Mn: 5.64%; Si: 0.55%; Ni: 17.6%; Cr: 15.5%; Mo: 4.22%; Ti: 0.11%; P: 0.007%; S: 0.005%; La: 0.08%; and the balance of Fe and unavoidable impurities. The composition of the welding wire is mainly austenite, and the austenite content is greater than or equal to 90%. The welding wire is relatively smooth in production, and there is no abnormal wire drawing breakage phenomenon.

[0049] In another aspect, the example also provides a laser welding method for hot-formed steel with aluminum plating layer, including the following steps: Aligning the sides to be welded of at least two pieces of the hot-formed steel with aluminum plating layer along the same plane, and forming a continuous joint gap between the two sides; Using the welding wire as a filler material to perform laser welding on the joint gap, so that the welding wire and the at least two pieces of the hot-formed steel with aluminum plating layer are melted and solidified together at the joint gap to form a continuous weld, so as to obtain a welded blank containing the weld; Performing heat treatment on the welded blank, so that the weld and the hot-formed steel with aluminum plating layer simultaneously undergo phase transition, so as to obtain a laser welded part containing the weld.

[0050] The at least two aluminum-containing plated hot-formed steels are a first aluminum-containing plated hot-formed steel and a second aluminum-containing plated hot-formed steel. The first aluminum-containing plated hot-formed steel is 1.6 mm thick 22MnB5. The first aluminum-containing plated hot-formed steel comprises a first base body and a first aluminum-containing plated layer. The first base body comprises C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; Ti: 0.033%. The first aluminum-containing plated layer is a double-sided aluminum-silicon plated layer with a weight of 75 g / m 2 2 on each side. In the plated layer, Al: 90%, and the rest is mainly Si. The second aluminum-containing plated hot-formed steel is 1.6 mm thick 22MnB5. The second aluminum-containing plated hot-formed steel comprises a second base body and a second aluminum-containing plated layer. The second base body comprises C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; Ti: 0.033%. The second aluminum-containing plated layer is a double-sided aluminum-silicon plated layer with a weight of 75 g / m 2 2 on each side. In the plated layer, Al: 90%, and the rest is mainly Si.

[0051] The side to be welded of the first aluminum-containing plated hot-formed steel and the second aluminum-containing plated hot-formed steel is cut by laser. Then, the two are spliced by aligning the lower surfaces. No gap is intentionally reserved during the splicing process. The maximum gap measured by a feeler gauge is not more than 0.1 mm. The width h of the splicing gap satisfies the requirement of 0≤h≤0.19 mm. The first aluminum-containing plated hot-formed steel and the second aluminum-containing plated hot-formed steel are welded by laser welding with a wire. The beam energy is approximately Gaussian distribution. The spot diameter on the surface of the aluminum-containing plated hot-formed steel is about 0.8 mm. The welding wire used is the welding wire of the present embodiment. No shielding gas is used during the welding process. By adjusting the welding speed and the wire feeding speed, the ratio of the area of the aluminum-containing plated hot-formed steel melted into the metal to the cross-sectional area of the weld, i.e., the dilution rate, is controlled to be 65% and 85% respectively, to prepare a welded blank.

[0052] The welded blank is heated to 930℃ in a heating furnace and kept for 5 minutes, and then stamped and quenched in a flat die. The flat die has a cooling water channel with cooling liquid in the channel. A laser welding with a wire part is obtained. Based on the laser welding with a wire part, a tensile specimen is prepared. The weld is located at the center of the tensile specimen and is perpendicular to the tensile direction. The tensile strength of the specimen with a dilution rate of 65% is 1474 MPa. The tensile fracture is located in the aluminum-containing plated hot-formed steel. The tensile strength of the specimen with a dilution rate of 85% is 1468 MPa. The tensile fracture is located in the aluminum-containing plated hot-formed steel. At this time, the main component of the weld is martensite.

[0053] Example 2 The welding wire used in the present embodiment is the same as that used in Example 1, except that the strength of the aluminum-containing plated hot-formed steel is different.

[0054] The first aluminum-containing plated hot forming steel is 1.6 mm thick 34MnB5. The first base composition is C: 0.33%; Mn: 2.2%; Si: 0.35%; Cr: 0.32%; B: 0.005%. The first aluminum-containing plated layer is a double-sided aluminum-silicon plated layer, with a plated layer weight of 75 g / m 2 2 on each side, and Al: 90% in the plated layer, with the remainder mainly being Si. The second aluminum-containing plated hot forming steel is 1.6 mm thick 34MnB5. The second base composition is C: 0.33%; Mn: 2.2%; Si: 0.35%; Cr: 0.32%; B: 0.005%. The second aluminum-containing plated layer is a double-sided aluminum-silicon plated layer, with a plated layer weight of 75 g / m 2 2 on each side, and Al: 90% in the plated layer, with the remainder mainly being Si.

[0055] The first aluminum-containing plated hot forming steel and the second aluminum-containing plated hot forming steel are laser cut on the side to be tailor-welded. Then, the lower surfaces are aligned for splicing, and no gap is intentionally reserved during the splicing process. The maximum splicing gap measured by a feeler gauge is not more than 0.1 mm, and the width h of the splicing gap satisfies the requirement of 0≤h≤0.19 mm. Laser wire filling welding is used to tailor-weld the first aluminum-containing plated hot forming steel and the second aluminum-containing plated hot forming steel. The beam energy is approximately Gaussian distributed, and the spot diameter on the surface of the aluminum-containing plated hot forming steel is about 0.8 mm. The welding wire used is the welding wire of the present embodiment, and no protective gas is used during the welding process. By adjusting the welding speed and the wire feeding speed, the ratio of the aluminum-containing plated hot forming steel melt-in metal area to the weld cross-sectional area, i.e., the dilution rate, is controlled to be 80%, and a welded blank is prepared.

[0056] The above-mentioned welded blank is heated to 930 ℃ in a heating furnace and is kept for 5 minutes, and then is subjected to stamping and quenching in a flat die. The flat die has a cooling water channel therein, and the water channel has a cooling liquid therein. A laser wire filling welded part is obtained. Based on the laser wire filling welded part, a tensile specimen is prepared, wherein the weld is located at the center of the tensile specimen and is perpendicular to the tensile direction. The dilution rate is 80%, the tensile strength of the specimen is 1943 MPa, and the tensile fracture is in the aluminum-containing plated hot forming steel. At this time, the main component of the weld is martensite.

[0057] Example 3 In the present embodiment, a welding wire for aluminum-containing plated hot forming steel is provided, and the diameter of the welding wire is 1.0 mm. The components of the welding wire include, in mass fraction: C: 0.01%; Mn: 11.2%; Si: 0.62%; Ni: 12.5%; Cr: 15.8%; Mo: 3.37%; Ti: 0.10%; P: 0.006%; S: 0.003%; La: 0.07%; and the balance being Fe and unavoidable impurities. The components of the welding wire are mainly austenite, and the austenite content is ≥90%. The welding wire is relatively smooth in production, and there is no abnormal wire drawing breakage phenomenon.

[0058] In another aspect, the present embodiment also provides a laser welding method for an aluminum-plated hot-formed steel, comprising the following steps: aligning the sides to be welded of at least two pieces of the aluminum-plated hot-formed steel along the same plane, and forming a continuous joint gap between the two sides; using the welding wire as a filler material to perform laser welding on the joint gap, so that the welding wire and the at least two pieces of the aluminum-plated hot-formed steel are melted and solidified together at the joint gap to form a continuous weld, thereby obtaining a welded blank containing the weld; performing heat treatment on the welded blank, so that the weld and the aluminum-plated hot-formed steel undergo phase transition synchronously, thereby obtaining a laser-welded part containing the weld.

[0059] The at least two pieces of the aluminum-plated hot-formed steel are a first aluminum-plated hot-formed steel and a second aluminum-plated hot-formed steel. The first aluminum-plated hot-formed steel is 1.6 mm thick 22MnB5. The first aluminum-plated hot-formed steel comprises a first base and a first aluminum-plated layer. The composition of the first base is C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; Ti: 0.033%. The first aluminum-plated layer is a double-sided aluminum-silicon plating layer with a plating weight of 75 g / m 2 2 on each side. In the plating layer, Al is 90%, and the rest is mainly Si. The second aluminum-plated hot-formed steel is 1.6 mm thick 22MnB5. The second aluminum-plated hot-formed steel comprises a second base and a second aluminum-plated layer. The composition of the second base is C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; Ti: 0.033%. The second aluminum-plated layer is a double-sided aluminum-silicon plating layer with a plating weight of 75 g / m 2 2 on each side. In the plating layer, Al is 90%, and the rest is mainly Si.

[0060] The sides to be welded of the first aluminum-plated hot-formed steel and the second aluminum-plated hot-formed steel are laser cut. Then, the sides are jointed in a lower surface alignment manner. No gap is intentionally reserved during the jointing process. The maximum joint gap measured by a feeler gauge is not more than 0.1 mm. The width h of the joint gap satisfies the requirement of 0≤h≤0.19 mm. The first aluminum-plated hot-formed steel and the second aluminum-plated hot-formed steel are welded by laser wire filling welding. The beam energy is approximately Gaussian distribution. The spot diameter on the surface of the aluminum-plated hot-formed steel is about 0.8 mm. The welding wire used is the welding wire of the present embodiment. No protective gas is used during the welding process. By adjusting the welding speed and the wire feeding speed, the ratio of the metal area melted into the aluminum-plated hot-formed steel to the cross-sectional area of the weld, i.e., the dilution rate, is controlled to be 65% and 85% respectively, thereby preparing a welded blank.

[0061] The above welding blank is heated to 930℃ in a heating furnace and kept for 5 minutes, and then stamping quenching is carried out in a flat die. The flat die has a cooling water channel, and the water channel has a cooling liquid. A laser filler welding part is obtained.

[0062] Based on the laser filler welding part, a tensile specimen is prepared, wherein the weld is located at the center of the tensile specimen and is perpendicular to the tensile direction. The tensile strength of the 65% dilution rate specimen is 1470 MPa, and the tensile fracture is located in the aluminum-containing plated hot forming steel; the tensile strength of the 85% dilution rate specimen is 1464 MPa, and the tensile fracture is located in the aluminum-containing plated hot forming steel. At this time, the main component of the weld is martensite.

[0063] Example 4 In this embodiment, a welding wire for an aluminum-containing plated hot forming steel is provided, with a diameter of 1.0 mm, and the components include, in mass fraction: C: 0.017%; Mn: 14.9%; Si: 0.64%; Ni: 11.4%; Cr: 14.5%; Mo: 2.5%; Ti: 0.12%; P: 0.007%; S: 0.004%; La: 0.08%; and the balance of Fe and unavoidable impurities. The components of the welding wire are mainly austenite, and the austenite content is ≥90%. The welding wire is relatively smooth in production, and there is no abnormal drawing wire breakage phenomenon.

[0064] On the other hand, the embodiment also provides a laser welding method for an aluminum-containing plated hot forming steel, comprising the following steps: Aligning the sides to be welded of at least two pieces of the aluminum-containing plated hot forming steel along the same plane, and forming a continuous joint gap between the two sides; Using the welding wire as a filler material, laser welding is performed on the joint gap, so that the welding wire and the at least two pieces of the aluminum-containing plated hot forming steel are melted and solidified together at the joint gap to form a continuous weld, thereby obtaining a welding blank containing the weld. Heat treating the welding blank to make the weld and the aluminum-containing plated hot forming steel undergo phase transition synchronously, thereby obtaining a laser welding part containing the weld.

[0065] The at least two pieces of the aluminum-containing plated hot forming steel are a first aluminum-containing plated hot forming steel and a second aluminum-containing plated hot forming steel, and the first aluminum-containing plated hot forming steel is a 1.6 mm thick 22MnB5. The first aluminum-containing plated hot forming steel includes a first base body and a first aluminum-containing plated layer, and the first base body has a composition of C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; and Ti: 0.033%. The first aluminum-containing plated layer is a double-sided aluminum-silicon plated layer, and each plated layer has a weight of 75 g / m 2Al: 90%, and the rest is mainly Si. The second aluminum-containing plated hot forming steel is 1.6 mm thick 22MnB5. The second aluminum-containing plated hot forming steel comprises a second base and a second aluminum-containing plated layer. The second base has a composition of C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; Ti: 0.033%. The second aluminum-containing plated layer is a double-sided aluminum-silicon plated layer, with a plated layer weight of 75 g / m 2 Al: 90%, and the rest is mainly Si.

[0066] The first aluminum-containing plated hot forming steel and the second aluminum-containing plated hot forming steel are laser cut on the side to be tailor-welded. Then, the lower surfaces are aligned for splicing, and no gap is intentionally reserved during the splicing process. The maximum splicing gap measured by a feeler gauge is not more than 0.1 mm, and the width h of the splicing gap satisfies the requirement of 0≤h≤0.19 mm. Laser wire filling welding is used to tailor-weld the first aluminum-containing plated hot forming steel and the second aluminum-containing plated hot forming steel. The beam energy is approximately Gaussian distributed, and the spot diameter on the surface of the aluminum-containing plated hot forming steel is about 0.8 mm. The welding wire used is the welding wire of the present embodiment, and no protective gas is used during the welding process. By adjusting the welding speed and the wire feeding speed, the ratio of the aluminum-containing plated hot forming steel melt-in area to the weld cross-sectional area, i.e., the dilution rate, is controlled to be 65% and 85%, and a welded blank is prepared.

[0067] The above-mentioned welded blank is heated to 930°C in a heating furnace and kept for 5 minutes, and then stamping and quenching are performed in a flat die. The flat die has a cooling water channel with cooling liquid in the water channel. A laser wire filling welded part is obtained. Based on the laser wire filling welded part, a tensile specimen is prepared, wherein the weld is located at the center of the tensile specimen and is perpendicular to the tensile direction. The tensile strength of the specimen with a dilution rate of 65% is 1445 MPa, and the tensile fracture is located in the aluminum-containing plated hot forming steel; the tensile strength of the specimen with a dilution rate of 85% is 1429 MPa, and the tensile fracture is located in the aluminum-containing plated hot forming steel. At this time, the main component of the weld is martensite.

[0068] Comparative Example 1 In this comparative example, the welding wire has a diameter of 1.0 mm, and its components include, by mass fraction: C: 0.01%; Mn: 1.7%; Si: 0.4%; Ni: 25%; Cr: 20%; Mo: 4.4%; Ti: 0.01%; P: 0.01%; S: 0.02%; and the balance of Fe and unavoidable impurities. The components of the welding wire are mainly austenite, and the austenite content is ≥90%. The welding wire is relatively smooth in production, and there is no abnormal wire drawing breakage phenomenon.

[0069] On the other hand, the welding wire described in this comparative example is used to prepare a tailor-welded part, which comprises the following steps: aligning the sides to be butt-welded of at least two of the aluminum-plated hot-formed steels along the same plane, and forming a continuous butt-joint gap between the two sides; using the welding wire as filler material, laser welding the butt-joint gap, and causing the welding wire and the at least two aluminum-plated hot-formed steels to co-melt and solidify at the butt-joint gap to form a continuous weld, thereby obtaining a welded blank containing the weld; subjecting the welded blank to heat treatment, causing the weld to undergo phase transformation synchronously with the aluminum-plated hot-formed steels, thereby obtaining a laser-welded part containing the weld.

[0070] In particular to the present comparative example, the at least two aluminum-plated hot-formed steels are a first aluminum-plated hot-formed steel and a second aluminum-plated hot-formed steel. The first aluminum-plated hot-formed steel is 1.6 mm thick 22MnB5. The first aluminum-plated hot-formed steel comprises a first base and a first aluminum-plated layer. The first base has a composition of C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; Ti: 0.033%. The first aluminum-plated layer is a double-sided aluminum-silicon plating layer with a plating weight of 75 g / m 2 2 on each side, and Al: 90% in the plating layer, with the rest being mainly Si. The second aluminum-plated hot-formed steel is 1.6 mm thick 22MnB5. The second aluminum-plated hot-formed steel comprises a second base and a second aluminum-plated layer. The second base has a composition of C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; Ti: 0.033%. The second aluminum-plated layer is a double-sided aluminum-silicon plating layer with a plating weight of 75 g / m 2 2 on each side, and Al: 90% in the plating layer, with the rest being mainly Si.

[0071] The sides to be butt-welded of the first aluminum-plated hot-formed steel and the second aluminum-plated hot-formed steel are laser cut. Then, the butt-joint is performed in a lower surface alignment manner, and no gap is intentionally reserved during the butt-joint process. The maximum butt-joint gap measured by a feeler gauge is not more than 0.1 mm, and the width h of the butt-joint gap satisfies the requirement of 0≤h≤0.19 mm. The first aluminum-plated hot-formed steel and the second aluminum-plated hot-formed steel are butt-welded by laser wire filling welding. In the process, the beam energy is approximately Gaussian distribution, and the spot diameter on the surface of the aluminum-plated hot-formed steel is about 0.8 mm. The welding wire used in the process is the welding wire of the present example, and no shielding gas is used during the welding process. By adjusting the welding speed and the wire feeding speed, the ratio of the aluminum-plated hot-formed steel melt-in area to the cross-sectional area of the weld, i.e. the dilution rate, is controlled to be 70%, thereby preparing a welded blank.

[0072] The above welding blank is heated to 930°C in a heating furnace and held for 5 minutes, and then stamping quenching is performed in a flat die. The flat die has a cooling water channel therein, and the water channel has a cooling liquid therein. A laser filler wire welding part is obtained. Based on the laser filler wire welding part, a tensile specimen is prepared, wherein the weld is located at the center of the tensile specimen and is perpendicular to the tensile direction. The tensile strength of the specimen is 1080 MPa, and the fracture is located at the weld.

[0073] Comparative Example 2 In the present comparative example, a welding wire with a diameter of 1.0 mm is used, and the composition of the welding wire includes, by mass fraction, C: 0.1%; Mn: 1.6%; Si: 0.4%; Ni: 20.7%; Cr: 25.8%; Mo: 0.1%; Cu: 0.05%; P: 0.006%; S: 0.01%; and the balance of Fe and unavoidable impurities. The composition of the welding wire is mainly austenite, and the austenite content is ≥ 90%. The welding wire is relatively smooth in production, and there is no abnormal wire drawing breakage phenomenon.

[0074] On the other hand, a tailor-welded part is prepared using the welding wire described in the present comparative example, including the following steps: aligning the sides to be tailor-welded of at least two pieces of the aluminum-containing plated hot-formed steel along the same plane, and forming a continuous joint gap between the two sides; using the welding wire as a filler material, performing laser welding on the joint gap, so that the welding wire and the at least two pieces of the aluminum-containing plated hot-formed steel are melted and solidified together at the joint gap to form a continuous weld, to obtain a welding blank containing the weld; performing heat treatment on the welding blank, so that the weld and the aluminum-containing plated hot-formed steel undergo phase transition synchronously, to obtain a laser welded part containing the weld.

[0075] Specifically, in the present comparative example, the at least two pieces of the aluminum-containing plated hot-formed steel are a first aluminum-containing plated hot-formed steel and a second aluminum-containing plated hot-formed steel, and the first aluminum-containing plated hot-formed steel is 1.6 mm thick 22MnB5. The first aluminum-containing plated hot-formed steel includes a first base body and a first aluminum-containing plated layer, and the composition of the first base body is C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; and Ti: 0.033%. The first aluminum-containing plated layer is a double-sided aluminum-silicon plated layer, and the weight of each plated layer is 75 g / m 2 2, and Al: 90% in the plated layer, and the rest is mainly Si. The second aluminum-containing plated hot-formed steel is 1.6 mm thick 22MnB5. The second aluminum-containing plated hot-formed steel includes a second base body and a second aluminum-containing plated layer, and the composition of the second base body is C: 0.24%; Mn: 1.19%; Si: 0.25%; Cr: 0.21%; B: 0.003%; and Ti: 0.033%. The second aluminum-containing plated layer is a double-sided aluminum-silicon plated layer, and the weight of each plated layer is 75 g / m2 The coating consists of 90% Al and the remainder is mainly Si.

[0076] The first and second aluminum-coated hot-formed steels were laser-cut on the sides to be welded. Then, they were spliced ​​using a bottom surface alignment method. No special gap was reserved during the splicing process; the maximum splicing gap measured with a feeler gauge did not exceed 0.1 mm, and the width h of the splicing gap met the requirement of 0 ≤ h ≤ 0.19 mm. The first and second aluminum-coated hot-formed steels were then welded using laser filler wire welding. The laser beam energy was approximately Gaussian distributed, and the diameter of the laser spot on the aluminum-coated hot-formed steel surface was approximately 0.8 mm. The welding wire used was the same as in this embodiment, and no shielding gas was used during the welding process. By adjusting the welding speed and wire feed speed, the ratio of the molten metal area of ​​the aluminum-coated hot-formed steel to the cross-sectional area of ​​the weld, i.e., the dilution rate, was controlled to 75% to prepare the weld blank.

[0077] The welded blank was heated to 930°C in a furnace and held for 5 minutes, then stamped and quenched in a flat die. The flat die contained cooling channels filled with coolant. This yielded a laser-welded part. Tensile specimens were prepared based on the laser-welded part, with the weld located at the center of the specimen and perpendicular to the tensile direction. The tensile strength of the specimen was 1050 MPa, and fracture occurred at the weld.

[0078] Appendix Figures 2-4 Detailed explanation: Figure 2 This is a diagram showing the location of tensile fracture in the weld area of ​​a laser-welded part provided in Embodiment 1 of this application; Figure 3 This is a diagram showing the location of tensile fracture in the weld area of ​​a laser-welded part according to Embodiment 2 of this application. As can be seen from the diagram, the tensile fracture of the laser-welded part provided in this embodiment occurs in the aluminum-coated hot-formed steel, indicating that the weld has sufficient strength. Figure 4 The figure shows the results of a four-point bending test for hydrogen embrittlement in the weld area of ​​a laser-welded part provided in Embodiment 1 of this application. As can be seen from the figure, no hydrogen embrittlement cracking was observed in the weld area after immersion in 0.1 mol / L hydrochloric acid for 120 hours.

[0079] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: When welding hot-formed steel with aluminum coating, the welding wire is used, eliminating the need for the aluminum coating stripping process, resulting in reduced equipment investment, lower processing costs, and improved production efficiency.

[0080] The welding wire is configured with low C, high Mn, and high Ni to obtain a diluted composition that complements the aluminum-coated hot-formed steel, thus avoiding austenite residue in the weld and achieving the effect of being suitable for aluminum-coated hot-formed steel of different strength levels and different wire feed rates.

[0081] The microstructure control of the welding wire with austenite volume fraction ≥ 90% obtains the effect of drawing without breaking; after the welding structure is hot formed, the tensile fracture is located in the weld of the base material containing aluminum plated layer hot formed steel, realizing the double effects of "easy processing of welding wire and high strength of weld".

[0082] The above description is merely that of a specific embodiment of the application, which enables a person skilled in the art to understand or implement the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined in the application can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to these embodiments shown in the application, but will conform to the widest scope consistent with the principles and novel features of the application.

Claims

1. A welding wire, characterized by The chemical composition of the welding wire comprises C, Mn, Ni, Cr, Si, Mo, and base element Fe and inevitable impurities; Definition: x = [Cr] + [Mo] + 1.5[Si], y = [Ni] + 30[C] + 0.5[Mn], wherein [Cr], [Mo], [Si], [Ni], [C] and [Mn] represent the mass fraction of the corresponding element in the welding wire respectively; Wherein, the x, y simultaneously satisfy the following three inequalities: 0.15≤x≤0.25, -0.777x+0.25≤y≤-0.777x+0.4 and y≥1.103x-0.

083.

2. The welding wire of claim 1, wherein, The chemical composition of the welding wire satisfies: [C]≤0.05%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, [Mo]≤5% in mass fraction.

3. The welding wire of claim 1 or 2, wherein, The chemical composition of the welding wire satisfies: [C]≤0.03%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, [Mo]≤5%, [P]≤0.03%, [S]≤0.03% in mass fraction.

4. The welding wire of claim 1 or 2, wherein, The chemical composition of the welding wire further comprises alloy elements Ti and La, and the chemical composition satisfies: [C]≤0.03%, 4%≤[Mn]≤15%, 10%≤[Ni]≤20%, 11%≤[Cr]≤16%, [Si]≤1.2%, 2%≤[Mo]≤5%, 0.06%≤[Ti]≤0.3%, 0.005%≤[La]≤0.3%, [P]≤0.03%, [S]≤0.03% in mass fraction.

5. The welding wire of any of claims 1-4, wherein, The volume fraction of austenite in the microstructure of the welding wire in the drawn finished state is ≥90%.

6. A laser welding method for welding at least two aluminum-plated hot-formed steels, the method comprising: aligning the sides to be spliced of the at least two aluminum-plated hot-formed steels along the same plane, and forming a continuous splicing gap between the sides to be spliced; using the welding wire according to any one of claims 1-5 as a filler material to laser weld the splicing gap, causing the welding wire and the at least two aluminum-plated hot-formed steels to melt and solidify together at the splicing gap to form a continuous weld seam, thereby obtaining a welded blank containing the weld seam; subjecting the welded blank to heat treatment to cause the weld seam to undergo phase transition synchronously with the aluminum-plated hot-formed steels, thereby obtaining a laser-welded part containing the weld seam.

7. The method of claim 6, wherein, The width of the splicing gap h≤0.19mm.

8. The method of claim 6, wherein, The dilution rate D of the laser welding satisfies: 65%≤D≤90%, wherein the dilution rate D = (aluminum-plated hot-formed steel melted area) / (weld seam cross-sectional area) × 100%, and the aluminum-plated hot-formed steel melted area and the weld seam cross-sectional area are measured on a polished metallographic section perpendicular to the welding direction.

9. The method of claim 6, wherein, The tensile fracture position of the laser welded part is located at the aluminum-containing plated hot-formed steel of the laser welded part, rather than at the weld of the laser welded part.

10. The method of claim 6, wherein, The aluminum-containing plated hot-formed steel comprises a hot-formed steel base and an aluminum-containing plated layer; when [C] of the hot-formed steel base is greater than or equal to 0.3% in terms of mass fraction, the chemical composition of the welding wire is controlled as follows: [C] is less than or equal to 0.02%, 4% is less than or equal to [Mn] and is less than or equal to 8%, 16% is less than or equal to [Ni] and is less than or equal to 20%, 11% is less than or equal to [Cr] and is less than or equal to 16%, [Si] is less than or equal to 1.2%, 2% is less than or equal to [Mo] and is less than or equal to 5%, 0.06% is less than or equal to [Ti] and is less than or equal to 0.3%, 0.005% is less than or equal to [La] and is less than or equal to 0.3%, [P] is less than or equal to 0.03%, [S] is less than or equal to 0.03%, and the balance is Fe and inevitable impurities.

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