A laser welding method for hot-formed steel with aluminum-containing plating layer

Abstract

The application provides a kind of laser welding wire for aluminum-containing plated hot-formed steel and a welding method thereof, the composition of the welding wire satisfies 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%, [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%, using the welding wire as welding material, by controlling the composition of the welding wire, on the one hand, it can provide guarantee for the composition of the weld metal, realize that the weld is mainly martensitic structure, so as to improve the strength of the weld; on the other hand, when the composition of the welding wire satisfies the requirement, the formation interval of martensite after the molten pool metal cools down is the widest, which can inhibit the performance decline problem caused by the inhomogeneity of the weld composition, therefore, under extreme conditions, even if the local welding wire does not fuse with the aluminum-containing plated hot-formed steel, martensitic structure can also be formed after the welding wire melts and solidifies again, so as to guarantee the mechanical properties of the joint.

Description

Technical Field

[0001] This application relates to the field of welding technology, and more particularly to a laser welding method for hot-formed steel with aluminum coating. Background Technology

[0002] Lightweight steel is an inevitable trend in materials development, and aluminum-silicon coated hot-formed steel is the main way to achieve this. In particular, aluminum-silicon coated products formed by hot stamping after welding have been widely used. Currently, the welding methods used for welding hot-formed steel are laser welding or laser filler wire welding.

[0003] The main problem encountered in laser welding of hot-formed steel with aluminum or aluminum alloy coatings is that during the welding process, aluminum enters the molten pool and forms high-temperature ferrite after hot forming. The hardness of high-temperature ferrite is much lower than that of martensite, thus reducing the tensile strength of the weld. To solve this problem, existing technologies typically use equipment to remove the aluminum-silicon coating before welding, avoiding the influence of coating elements on weld quality and thus addressing the issue of reduced weld strength. However, this process requires additional laser stripping equipment, increasing equipment and process costs.

[0004] Laser filler wire welding improves weld performance by adding filler wire metal to the molten pool to dilute the aluminum content. The development of filler wire is a key aspect of this process. Summary of the Invention

[0005] This application provides a laser welding wire for hot-formed steel with aluminum coating and a welding method thereof to solve the following technical problem: providing a new material for laser welding wire for hot-formed steel with aluminum coating.

[0006] In a first aspect, the present invention provides a laser welding wire for hot-formed steel with an aluminum coating, wherein the chemical composition of the welding wire satisfies:

[0007] 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%,

[0008] [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%,

[0009] Wherein [C], [Ni], [Mn], [Cr], [Mo], [Si] and [Nb] are the mass fractions of C, Ni, Mn, Cr, Si and Nb in the welding wire, respectively.

[0010] Optionally, in the welding wire, Ni: >3%, Si: 0.15%~0.8%, Ti: 0.05%~0.5%.

[0011] Optionally, the diameter of the welding wire is 0.9mm to 1.2mm.

[0012] In a second aspect, the present invention also provides a method for laser welding of hot-formed steel with aluminum coating, using the laser welding wire for hot-formed steel with aluminum coating described in the first aspect, comprising the following steps:

[0013] The first aluminum-coated plate to be welded is spliced ​​with the second aluminum-coated plate to be welded.

[0014] Laser welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam.

[0015] The welded blank is heat-treated to obtain a laser filler wire welded part;

[0016] The weld composition satisfies:

[0017] 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤12%, [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al]≤12%, 30*[C]+[Ni]+0.5*[Mn]<-0.76*([Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al])+0.187, where [C], [Ni], [Mn], [Cr], [Mo], [Si], [Nb] and [Al] are the mass fractions of C, Ni, Mn, Cr, Si, Nb and Al in the weld, respectively.

[0018] Optionally, the volume ratio of laser welding wire in the weld is 10% to 70%.

[0019] Optionally, the first aluminum-coated plate to be welded includes a first aluminum-coated layer, and the second aluminum-coated plate to be welded includes a second aluminum-coated layer. By mass fraction, the chemical composition of the first aluminum-coated layer and the second aluminum-coated layer both include: Al: 85%~95%; Si: 5%~15%.

[0020] Optionally, the thickness of both the first aluminum-containing coating and the second aluminum-containing coating is 10μm~100μm.

[0021] Optionally, the carbon equivalent of the welding wire is Ceq0, and the carbon equivalent of the aluminum-coated plate to be welded with high tensile strength is Ceq1, satisfying Ceq1≤Ceq0≤Ceq1+1, where Ceq is calculated as Ceq=[C]+[Mn] / 6+([Cr]+[Mo]) / 5+[Ni] / 15]*100%.

[0022] Optionally, the step of heat-treating the welding blank to obtain the laser filler wire welded part specifically includes: heating, hot stamping and quenching the welding blank to obtain the laser filler wire welded part;

[0023] The heating temperature is above the austenitizing temperature AC3; and / or

[0024] The quenching cooling rate is >27℃ / s.

[0025] Optionally, the laser used in the laser welding process includes a central light source and a peripheral light source.

[0026] Optionally, the width of the weld on the laser-irradiated side is greater than that on the other side.

[0027] The technical solution provided by this invention has the following advantages compared with the prior art:

[0028] This invention provides a laser welding wire for hot-formed steel with aluminum coating and a welding method thereof. The composition of the welding wire satisfies 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%. Using this welding wire as a welding material, by controlling the composition of the welding wire, on the one hand, it can ensure the composition of the weld metal, so that the weld is mainly martensitic, thereby improving the weld strength; on the other hand, when the welding wire composition meets the requirements, the formation range of martensite after the molten pool metal cools is the widest, which can suppress the performance degradation caused by the non-uniformity of the weld composition. Therefore, even under extreme conditions, even if the welding wire does not fuse with the hot-formed steel with aluminum coating in some areas, martensitic structure can still be formed after the welding wire melts and resolidifies, thereby ensuring the mechanical properties of the joint. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A flowchart of a welding method for hot-formed steel with aluminum coating provided in this application embodiment;

[0032] Figure 2 A schematic diagram of a filler wire welded part obtained after welding using the welding method provided in some embodiments of this application;

[0033] Figure 3 The tensile curve of the weld position of the filler wire welding part provided in Embodiment 1 of this application;

[0034] Figure 4 This is a diagram showing the location of tensile fracture in the weld area of ​​a filler wire welded part provided in Embodiment 1 of this application;

[0035] Figure 5 A diagram showing the location of tensile fracture in the weld area of ​​a filler wire welded part provided in Comparative Example 1 of this application;

[0036] Figure 6 This is a schematic diagram of a crack in the weld of a filler wire welded part provided in Comparative Example 3 of this application;

[0037] Figure 7 This is a schematic diagram of the laser light source provided in the embodiments of this application.

[0038] Figure label:

[0039] 1-First aluminum-containing coating on the substrate to be welded; 11-First substrate; 12-First aluminum-containing coating;

[0040] 2-Second aluminum-containing coating on the substrate to be welded; 21-Second substrate; 22-Second aluminum-containing coating;

[0041] 3-Weld;

[0042] 4-Laser; 41-Central light source; 42-Peripheral light source. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0045] In this application, unless otherwise stated, terms including "comprising" and the like mean "including but not limited to". Relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0046] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0047] In a first aspect, a laser welding wire for hot-formed steel with an aluminum coating, wherein the chemical composition of the welding wire satisfies the following:

[0048] 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%,

[0049] [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%,

[0050] Wherein [C], [Ni], [Mn], [Cr], [Mo], [Si] and [Nb] are the mass fractions of C, Ni, Mn, Cr, Si and Nb in the welding wire, respectively.

[0051] In the above embodiments, the welding wire is used as the welding material. By controlling the composition of the welding wire to meet the above relationship, on the one hand, it can ensure the composition of the weld metal, so that the weld is mainly composed of martensite, thereby improving the weld strength; on the other hand, when the composition of the welding wire meets the requirements, the formation range of martensite after the molten pool metal cools is the widest, which can suppress the performance degradation caused by the non-uniformity of the weld composition. Therefore, under extreme conditions, even if the local welding wire does not fuse with the aluminum-coated hot-formed steel, the welding wire can still form a martensite structure after melting and resolidifying, thereby ensuring the mechanical properties of the joint.

[0052] It should be noted that the composition of the welding wire can be one of the following three types:

[0053] (1) In addition to C, Ni, Mn, Mo, Cr, Si and Nb, it also includes other elements;

[0054] (2) Includes only some or all of the elements in C, Ni, Mn, Mo, Cr, Si and Nb, for example, the content of C, Cr, Nb or Mn can be 0;

[0055] (3) Includes some elements from C, Ni, Mn, Cr, Mo, Si and Nb. For example, the content of C, Cr, Nb or Mn can be 0, and it also includes other elements.

[0056] As an optional implementation, the welding wire contains Ni: >3%, Si: 0.15%~0.8%, and Ti: 0.05%~0.5%.

[0057] In the above embodiments, controlling the Ni content in the welding wire composition to be greater than 3% is, on the one hand, to offset the influence of the ferrite stabilizing element Al entering the molten pool, and on the other hand, to avoid adding too much hardenable austenitic stabilizing element such as C to the welding wire. If the C element in the welding wire is too high, it will not only increase the risk of cracking, but also cause the problem of pull-out fracture during the welding wire production process.

[0058] In the above embodiments, adding Si and Ti elements to the molten pool via welding wire reduces the surface tension of the molten pool, increases fluidity, and promotes uniform distribution of elements within the molten pool, thus avoiding localized enrichment of Al during welding. Furthermore, the addition of Si and Ti elements helps change the direction of convection in the molten pool from "from the center to the periphery" to "from the periphery to the center." Welding tests after removing the coating from the upper and lower surfaces respectively show that the coating on the laser-irradiated side (upper surface) has a greater impact on weld quality than the opposite side (lower surface). For the traditional "from the center to the periphery" convection method, on the laser-irradiated side, the molten coating around the molten pool moves downwards along the fusion line. Due to the cooling effect of the surrounding metal, the high-temperature residence time near the fusion line is the shortest, easily causing Al elements in the coating to agglomerate near the fusion line before they have time to distribute evenly in the weld, thus reducing joint quality. This invention promotes convection "from the periphery to the center" on the laser irradiation side, causing Al in the molten coating on the upper surface to move towards the center of the molten pool after entering the pool. Because the temperature is higher in the center of the molten pool, Al has sufficient time to fuse with the molten metal, improving the uniformity of Al in the molten pool. Therefore, changing the convection direction in the molten pool facilitates the uniform distribution of Al and reduces its segregation near the fusion line.

[0059] Meanwhile, since excessive Si content can easily lead to oxide inclusions, the Si content needs to be controlled between 0.15% and 0.8%. For example, the Si content can be set to 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%; the Ti content can be set to 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0060] As an optional implementation, the diameter of the welding wire is 0.9 mm to 1.2 mm.

[0061] In the above embodiments, controlling the diameter of the welding wire helps to control the welding time and volume. For example, the diameter of the welding wire can be set to 0.9 mm, 1.0 mm, 1.1 mm, or 1.2 mm.

[0062] Secondly, the present invention also provides a method for laser welding of hot-formed steel with aluminum coating, such as... Figure 1 As shown, welding using the laser welding wire for hot-formed steel with aluminum coating as described in the first aspect includes the following steps:

[0063] The first aluminum-coated plate to be welded is spliced ​​with the second aluminum-coated plate to be welded.

[0064] Laser welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam.

[0065] The welded blank is heat-treated to obtain a laser filler wire welded part;

[0066] The weld composition satisfies:

[0067] 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤12%, [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al]≤12%, 30*[C]+[Ni]+0.5*[Mn]<-0.76*([Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al])+0.187, where [C], [Ni], [Mn], [Cr], [Mo], [Si], [Nb] and [Al] are the mass fractions of C, Ni, Mn, Cr, Si, Nb and Al in the weld, respectively.

[0068] In the above embodiments, when the weld composition meets the above requirements during welding, the weld can be predominantly martensitic, thereby improving the weld strength. C, Ni, and Mn are all austenite stabilizing elements, which can prevent Al from forming high-temperature ferrite after entering the molten pool. It should be noted that due to the certain inhomogeneity of the weld structure, when the weld composition meets 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤12%, the formation range of martensite after the molten pool metal cools is the widest, which can suppress the performance degradation caused by the inhomogeneity of the weld composition, thus ensuring the improvement of the joint's mechanical properties. When the weld composition does not meet the above conditions, ferrite or austenite structures are easily formed in the weld, thereby reducing the mechanical properties of the joint.

[0069] As an optional implementation, the volume ratio of the laser welding wire in the weld is 10% to 70%.

[0070] In the above embodiments, controlling the volume ratio of the laser welding wire in the weld is intended to control the main components of the weld during welding. If the welding wire occupies too much volume, the energy required to melt the welding wire will increase, resulting in insufficient energy to melt the welding plate, reduced welding efficiency, increased welding wire consumption, and a higher risk of defects such as poor fusion. If the welding wire occupies too little volume, i.e., the amount of welding wire used is too small, the composition of the weld will have a higher aluminum content from the plate to be welded and a lower content of beneficial elements from the welding wire, which may lead to the formation of ferrite in the weld and a reduction in the mechanical properties of the joint.

[0071] As an optional implementation, the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded are spliced ​​together, specifically including: splicing the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded together, wherein the bottoms of the plates to be welded are aligned.

[0072] As an optional implementation, the first aluminum-coated substrate to be welded comprises a first aluminum-coated layer and a first substrate, and the second aluminum-coated substrate to be welded comprises a second aluminum-coated layer and a second substrate. By mass fraction, the chemical composition of both the first and second aluminum-coated layers comprises: Al: 85%~95%; Si: 5%~15%. The chemical composition of the first and second substrates comprises C, Si, Mn, Cr, Ti, and Fe.

[0073] As an optional implementation, the thickness of both the first aluminum-containing coating and the second aluminum-containing coating is 10μm~100μm.

[0074] In the above embodiments, controlling the aluminum content and thickness of the aluminum-containing coating is intended to prevent oxidation and decarburization at high temperatures during the subsequent heating process of the welded blank.

[0075] As an optional implementation, the carbon equivalent of the welding wire is Ceq0, and the carbon equivalent of the aluminum-coated plate to be welded with high tensile strength is Ceq1, satisfying Ceq1≤Ceq0≤Ceq1+1, where Ceq is calculated as Ceq=[C]+[Mn] / 6+([Cr]+[Mo]) / 5+[Ni] / 15]*100%.

[0076] In the above embodiments, controlling the carbon equivalent Ceq0 of the welding wire to satisfy Ceq1≤Ceq0 is to ensure that the joint has higher hardenability than the base material with higher tensile strength; controlling the carbon equivalent Ceq0 of the welding wire to satisfy Ceq0≤Ceq1+1 is to prevent the joint from having excessive hardenability, thereby increasing the tendency to crack.

[0077] As an optional implementation, the step of heat-treating the welding blank to obtain the laser filler wire welded part specifically includes: heating, hot stamping and quenching the welding blank to obtain the laser filler wire welded part.

[0078] As an optional implementation, the heating temperature is above the austenitizing temperature AC3.

[0079] In the above method, the heating temperature is controlled to be above the austenitizing temperature AC3. The purpose is that the welded blank can only achieve complete austenitization when the temperature is above AC3, which lays the foundation for the formation of martensite and the achievement of the specified strength after cooling.

[0080] As an optional implementation, the quenching cooling rate is >27°C / s.

[0081] In the above embodiments, the cooling rate of quenching is controlled to be >27℃ / s. The purpose is that the aluminum-coated plate with high carbon equivalent needs to reach this cooling rate during cooling in order to transform it into a certain amount of martensite structure and achieve the specified strength.

[0082] As an optional implementation, the laser used in the laser welding includes a central light source and a peripheral light source.

[0083] In the above embodiments, a central light source and peripheral light sources are used as laser sources. Due to the cooperation between the central and peripheral light sources, the central light source forms a narrow weld seam, while the peripheral light sources form a high-temperature region. By adding peripheral light sources, on the one hand, the residence time of the molten pool, especially in the area near the fusion line, in the liquid state is increased, avoiding the agglomeration of Al in the coating near the fusion line after entering the molten pool, and further improving the uniformity of Al element distribution in the molten pool; on the other hand, the cooling rate of the molten pool is reduced by the peripheral light sources, effectively preventing welding cracks from appearing in the weld seam.

[0084] As an optional implementation, the width of the weld on the laser-irradiated side is greater than that on the other side. The purpose is to further reduce the total amount of Al in the lower surface coating entering the molten pool. Combined with the control of the welding wire and weld composition, the uniformity of Al in the weld can be improved, which can reduce the impact of Al entering the molten pool on the joint performance and improve the weld strength.

[0085] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0086] Example 1

[0087] This embodiment provides a laser welding wire for hot-formed steel with aluminum coating. The wire has a diameter of 1.2 mm and its composition by mass percentage includes: C: 0.104%, Si: 0.250%, Mn: 1.62%, P: 0.008%, S: 0.001%, Cr: 1.07%, Ni: 5.99%, Mo: 1.39%, Ti: 0.08%, with the balance being Fe.

[0088] Calculations show that 30*[C]+[Ni]+0.5*[Mn]=9.92% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]=2.84%. The composition of the laser welding wire satisfies 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%.

[0089] The laser welding wire provided above is used to prepare filler wire welded parts. A schematic diagram of the resulting filler wire welded parts is shown below. Figure 2 As shown, its preparation method includes the following steps:

[0090] S1: The first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded are spliced ​​together, with the bottoms of the plates to be welded aligned. The first aluminum-coated plate to be welded has a thickness of 1.8 mm and consists of a first substrate and a first aluminum-coated layer. The first substrate has the following composition: C: 0.24%, Si: 0.25%, Mn: 1.19%, Cr: 0.21%, Ti: 0.03%, with the balance being Fe. The first aluminum-coated layer has a thickness of 30 μm and has the following composition: Al: 88%, Si: 12%.

[0091] The second aluminum-coated substrate, with a thickness of 1.8 mm, consists of a second substrate and a second aluminum-coated layer. The second substrate has the following composition: C: 0.24%, Si: 0.25%, Mn: 1.19%, Cr: 0.21%, Ti: 0.03%, with the balance being Fe. The second aluminum-coated layer has a thickness of 30 μm and a composition of: Al: 88%, Si: 12%.

[0092] Calculations show that the carbon equivalent of the welding wire, Ceq0, is 1.27, and the first aluminum-coated substrate to be welded, Ceq1, is 0.48, satisfying the condition that Ceq1 ≤ Ceq0 ≤ Ceq1 + 1.

[0093] S2: Laser filler wire welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam;

[0094] The laser consists of a central light source and peripheral light sources, with the peripheral light sources having 50% of the energy of the central light source. The central light source performs the welding, while the peripheral light sources perform the heating. The width of the upper surface of the weld is greater than that of the lower surface. The volume ratio of welding wire metal in the weld is 10%, and the average composition of the obtained weld includes: C: 0.23%, Si: 0.258%, Mn: 1.23%, Cr: 0.30%, Ni: 0.60%, Mo: 0.14%, Al: 1.02%, Ti: 0.03%. Calculations show that the weld composition meets the requirements of 7.8% ≤ 30*[C] + [Ni] + 0.5*[Mn] ≤ 12%, [Cr] + [Mo] + 1.5*[Si] + 0.5*[Nb] + 5.5*[Al] ≤ 12%, and 30*[C] + [Ni] + 0.5*[Mn] < -0.76*([Cr] + [Mo] + 1.5*[Si] + 0.5*[Nb] + 5.5*[Al]) + 0.187.

[0095] S3: The welding blank is heated, hot-stamped, and quenched to obtain a laser-welded part, wherein the heating temperature is 930℃ (>AC3) and the holding time is 5min. After heating, it is quickly transferred to a flat mold for cooling, with a cooling rate >27℃ / s.

[0096] Finally, tensile samples were prepared from the laser-welded parts, and the tensile curves are shown below. Figure 3 As shown, the fracture location after the tensile test was in the parent material, and the tensile strength was 1639 MPa. Figure 4 As shown, the weld strength performance obtained in this embodiment is good and meets the test requirements.

[0097] Example 2

[0098] This embodiment provides a laser welding wire for hot-formed steel with aluminum coating. The wire has a diameter of 1.2 mm and its composition by mass percentage includes: C: 0.08%, Si: 0.40%, Mn: 1.5%, P: 0.008%, S: 0.001%, Cr: 1%, Ni: 5%, Mo: 1%, Ti: 0.08%, with the balance being Fe.

[0099] Calculations show that 30*[C]+[Ni]+0.5*[Mn]=8.15% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]=2.6%. The laser welding wire satisfies the following conditions: 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%.

[0100] The laser welding wire provided above is used to weld and prepare filler wire welded parts. The preparation method includes the following steps:

[0101] S1: The first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded are spliced ​​together, with the bottoms of the plates to be welded aligned. The first aluminum-coated plate to be welded has a thickness of 1.2 mm and consists of a first substrate and a first aluminum-coated layer. The first substrate has the following composition: C: 0.23%, Si: 0.22%, Mn: 1.2%, Cr: 0.18%, Ti: 0.03%, with the balance being Fe. The first aluminum-coated layer has a thickness of 30 μm and has the following composition: Al: 88%, Si: 12%.

[0102] The second aluminum-coated substrate, with a thickness of 1.2 mm, consists of a second substrate and a second aluminum-coated layer. The second substrate has the following composition: C: 0.23%, Si: 0.22%, Mn: 1.2%, Cr: 0.18%, Ti: 0.03%, with the balance being Fe. The second aluminum-coated layer has a thickness of 30 μm and a composition of: Al: 88%, Si: 12%.

[0103] Calculations show that the carbon equivalent of the laser welding wire, Ceq0, is 1.06, and the first aluminum-coated substrate to be welded, Ceq1, is 0.47, satisfying the condition that Ceq1 ≤ Ceq0 ≤ Ceq1 + 1.

[0104] S2: Laser filler wire welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam;

[0105] The laser consists of a central light source and peripheral light sources, with the peripheral light sources having 50% of the energy of the central light source. The central light source performs the welding, while the peripheral light sources provide heating. The width of the upper surface of the weld is greater than that of the lower surface. The weld metal accounts for 40% of the weld volume, and the average composition of the obtained weld includes: C: 0.18%, Si: 0.31%, Mn: 1.3%, Cr: 0.5%, Ni: 2%, Mo: 0.4%, Al: 1.2%, Ti: 0.04%.

[0106] Calculations show that the weld composition meets the requirements of 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤12%, [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al]≤12%, and 30*[C]+[Ni]+0.5*[Mn]<-0.76*([Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al])+0.187.

[0107] S3: The welded blank is heated, hot-stamped, and quenched to obtain a laser-welded part. The heating temperature is 930℃ (>AC3), and the holding time is 5 minutes. After heating, it is quickly transferred to a flat mold for cooling, with a cooling rate >27℃ / s.

[0108] Finally, tensile samples were prepared from the laser-welded parts. After tensile testing, the fracture location was still in the base material, and the tensile strength was 1577 MPa, indicating that the weld strength performance obtained in this embodiment is good and meets the test requirements.

[0109] Comparative Example 1

[0110] This comparative example provides a laser welding wire for hot-formed steel with aluminum coating. The wire has a diameter of 1.2 mm and its composition by mass percentage includes: C: 0.08%, Si: 0.52%, Mn: 1.05%, P: 0.015%, S: 0.008%, Cr: 0.21%, Ni: 0.95%, Mo: 0.12%, with the balance being Fe.

[0111] Calculations show that 30*[C]+[Ni]+0.5*[Mn]=3.88% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]=1.11%. The composition of the laser welding wire satisfies [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%, but does not satisfy 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%. Furthermore, the Ni content in the welding wire used for laser filler wire welding is 0.95%, which does not meet the requirement of >3%.

[0112] The laser welding wire provided above is used to weld and prepare filler wire welded parts. The preparation method includes the following steps:

[0113] S1: The first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded are spliced ​​together, with the bottoms of the plates to be welded aligned. The first aluminum-coated plate to be welded has a thickness of 1.8 mm and consists of a first substrate and a first aluminum-coated layer. The first substrate has the following composition: C: 0.24%, Si: 0.25%, Mn: 1.19%, Cr: 0.21%, Ti: 0.03%, with the balance being Fe. The first aluminum-coated layer has a thickness of 30 μm and has the following composition: Al: 88%, Si: 12%.

[0114] The second aluminum-coated substrate, with a thickness of 1.8 mm, consists of a second substrate and a second aluminum-coated layer. The second substrate has the following composition: C: 0.24%, Si: 0.25%, Mn: 1.19%, Cr: 0.21%, Ti: 0.03%, with the balance being Fe. The second aluminum-coated layer has a thickness of 30 μm and a composition of: Al: 88%, Si: 12%.

[0115] Calculations show that the carbon equivalent of the welding wire, Ceq0, is 0.38, and the carbon equivalent of the first aluminum-coated plate to be welded, Ceq1, is 0.48. This satisfies Ceq0 ≤ Ceq1 + 1, but does not satisfy Ceq1 ≤ Ceq0.

[0116] S2: Laser filler wire welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam;

[0117] In this comparative example, the laser used has only a central light source, meaning that welding is performed using only the central light source during the welding process. The width of the upper surface of the weld is greater than that of the lower surface. The weld metal accounts for 10% of the volume of the weld. The average composition of the weld is as follows: C: 0.22%, Si: 0.28%, Mn: 1.18%, Cr: 0.21%, Ni: 0.1%, Mo: 0.02%, Al: 1%, Ti: 0.01%. Calculations show that the weld composition meets the requirements of [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al]≤12% and 30*[C]+[Ni]+0.5*[Mn]<-0.76*([Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al])+0.187, but does not meet the requirement of 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤12%.

[0118] S3: The welded blank is heated, hot-stamped, and quenched to obtain a laser-welded part. The heating temperature is 930℃ (>AC3), and the holding time is 5 minutes. After heating, it is quickly transferred to a flat mold for cooling, with a cooling rate >27℃ / s.

[0119] Finally, the obtained laser-welded parts were prepared into tensile samples. After tensile testing, the fracture location was located at the weld seam, such as... Figure 5 As shown, the tensile strength is 1295 MPa, indicating that the weld strength is insufficient and does not meet the test requirements.

[0120] Comparative Example 2

[0121] This comparative example provides a laser welding wire for hot-formed steel with aluminum coating. The wire has a diameter of 1.2 mm and its composition by mass percentage includes: C: 0.08%, Si: 0.52%, Mn: 1.05%, P: 0.015%, S: 0.008%, Cr: 0.21%, Ni: 0.95%, Mo: 0.12%, with the balance being Fe.

[0122] Calculations show that 30*[C]+[Ni]+0.5*[Mn]=3.88% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]=1.11%. The composition of the laser welding wire satisfies [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%, but does not satisfy 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%. Furthermore, the Ni content in the welding wire used for laser filler wire welding is 0.95%, which does not meet the requirement of >3%.

[0123] The laser welding wire provided above is used to weld and prepare filler wire welded parts. The preparation method includes the following steps:

[0124] S1: The first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded are spliced ​​together, with the bottoms of the plates to be welded aligned. The first aluminum-coated plate to be welded has a thickness of 1.8 mm and consists of a first substrate and a first aluminum-coated layer. The first substrate has the following composition: C: 0.24%, Si: 0.25%, Mn: 1.19%, Cr: 0.21%, Ti: 0.03%, with the balance being Fe. The first aluminum-coated layer has a thickness of 30 μm and has the following composition: Al: 88%, Si: 12%.

[0125] The second aluminum-coated substrate, with a thickness of 1.8 mm, consists of a second substrate and a second aluminum-coated layer. The second substrate has the following composition: C: 0.24%, Si: 0.25%, Mn: 1.19%, Cr: 0.21%, Ti: 0.03%, with the balance being Fe. The second aluminum-coated layer has a thickness of 30 μm and a composition of: Al: 88%, Si: 12%.

[0126] Calculations show that the carbon equivalent of the welding wire, Ceq0, is 0.38, and the carbon equivalent of the first aluminum-coated plate to be welded, Ceq1, is 0.48. This satisfies Ceq0 ≤ Ceq1 + 1, but does not satisfy Ceq1 ≤ Ceq0.

[0127] S2: Laser filler wire welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam;

[0128] The laser used in this comparative example includes a central light source and a peripheral light source; that is, welding is carried out using both central and peripheral light sources during the welding process. The width of the upper surface of the weld is greater than that of the lower surface. The weld metal accounts for 10% of the volume of the weld. The average composition of the weld is C: 0.22%, Si: 0.28%, Mn: 1.18%, Cr: 0.21%, Ni: 0.1%, Mo: 0.02%, Al: 1%, Ti: 0.01%. Calculations show that the weld composition meets the requirements of [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al]≤12% and 30*[C]+[Ni]+0.5*[Mn]<-0.76*([Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al])+0.187, but does not meet the requirement of 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤12%.

[0129] S3: The welded blank is heated, hot-stamped, and quenched to obtain a laser-welded part. The heating temperature is 930℃ (>AC3), and the holding time is 5 minutes. After heating, it is quickly transferred to a flat mold for cooling, with a cooling rate >27℃ / s.

[0130] Finally, the obtained laser-welded parts were prepared into tensile samples. After tensile testing, the fracture location was located at the weld, and the tensile strength was 1379 MPa. Although the tensile strength was higher than that of Comparative Example 1, it still did not meet the test requirements.

[0131] Comparative Example 3

[0132] This comparative example provides a laser welding wire for hot-formed steel with aluminum coating, with a diameter of 1.2 mm and a composition by mass percentage of: C: 0.08%, Si: 0.5%, Mn: 1.3%, P: 0.006%, S: 0.001%, Cr: 12%, Ni: 6%, Mo: 1%, with the balance being Fe.

[0133] Calculations show that 30*[C]+[Ni]+0.5*[Mn]=9.05% and [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]=13.75%. Therefore, the welding wire meets the requirement of 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%, but does not meet the requirement of [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%. Furthermore, the Ni content in the welding wire used for laser filler wire welding is 6%, which meets the requirement of >3%.

[0134] The laser welding wire provided above is used to prepare filler wire welded parts, and the preparation method includes the following steps:

[0135] S1: The first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded are spliced ​​together, with the bottoms of the plates to be welded aligned. The first aluminum-coated plate to be welded has a thickness of 1.2 mm and consists of a first substrate and a first aluminum-coated layer. The first substrate has the following composition: C: 0.23%, Si: 0.22%, Mn: 1.2%, Cr: 0.18%, Ti: 0.03%, with the balance being Fe. The first aluminum-coated layer has a thickness of 30 μm and has the following composition: Al: 88%, Si: 12%.

[0136] The second aluminum-coated substrate, with a thickness of 1.2 mm, consists of a second substrate and a second aluminum-coated layer. The second substrate has the following composition: C: 0.23%, Si: 0.22%, Mn: 1.2%, Cr: 0.18%, Ti: 0.03%, with the balance being Fe. The second aluminum-coated layer has a thickness of 30 μm and a composition of: Al: 88%, Si: 12%.

[0137] Calculations show that the carbon equivalent of the welding wire, Ceq0, is 3.3, and the first aluminum-coated substrate to be welded, Ceq1, is 0.47, which does not satisfy the condition Ceq1≤Ceq0≤Ceq1+1.

[0138] S2: Laser filler wire welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam;

[0139] In this comparative example, the laser used has only a central light source, and welding is performed solely using the central light source. The width of the upper surface of the weld is greater than that of the lower surface. The volume ratio of the welding wire metal in the weld is 40%, and the average composition of the obtained weld is C: 0.17%, Si: 0.33%, Mn: 1.2%, Cr: 4.9%, Ni: 2.4%, Mo: 0.4%, Al: 1.2%. This satisfies the requirements of 7.8% ≤ 30*[C] + [Ni] + 0.5*[Mn] ≤ 12% and 30*[C] + [Ni] + 0.5*[Mn] < -0.76*([Cr] + [Mo] + 1.5*[Si] + 0.5*[Nb] + 5.5*[Al]) + 0.187, but does not meet the requirement of [Cr] + [Mo] + 1.5*[Si] + 0.5*[Nb] + 5.5*[Al] ≤ 12%.

[0140] S3: The welded blank is heated, hot-stamped, and quenched to obtain a laser-welded part. The heating temperature is 930℃ (>AC3), and the holding time is 5 minutes. After heating, it is quickly transferred to a flat mold for cooling, with a cooling rate >27℃ / s.

[0141] Finally, tensile samples were prepared from the laser-welded parts. After tensile testing, the fracture location was at the weld seam, with a tensile strength of 1498 MPa, indicating that the weld strength was still insufficient. Further testing revealed the presence of cracks in the weld seam. Figure 6 As shown, the test requirements are not met.

[0142] In summary, Examples 1 and 2 both used the laser welding wire provided in this invention for hot-formed steel with aluminum coating to prepare filler wire welded parts. The tensile fracture points of the obtained products were not located at the weld seam, indicating that the weld joint strength was high. However, the laser welding wires used in Comparative Examples 1-3 did not meet the requirements of the laser welding wire in this invention. When applied to prepare filler wire welded parts, although they had a certain tensile strength, the fracture points were all located at the weld seam, indicating that the strength of the obtained weld joint was insufficient. Furthermore, in Comparative Examples 1 and 2, the same laser welding wire was used, but different laser light sources were employed for welding. Although the filler wire welded parts all fractured at the weld seam, the tensile strengths they withstood differed. In Comparative Example 2, a laser with a central light source and peripheral light sources was used for welding, and the highest tensile strength reached 1379 MPa, significantly higher than the 1295 MPa in Comparative Example 1. This demonstrates that using a central light source and peripheral light sources as the laser for welding is more beneficial to the welding process.

[0143] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for laser welding of hot-formed steel with aluminum coating, characterized in that, Welding using laser welding wire for hot-formed steel with aluminum coating includes the following steps: The first aluminum-coated plate to be welded is spliced ​​with the second aluminum-coated plate to be welded. Laser welding is performed on the first aluminum-coated plate to be welded and the second aluminum-coated plate to be welded to form a weld blank with a weld seam. The weld blank is heated, hot-stamped, and quenched to obtain a laser filler wire welded part. The heating temperature is above the austenitizing temperature AC3; the quenching cooling rate is >27℃ / s; The chemical composition of the welding wire satisfies: 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤15%, [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]≤8%; Wherein [C], [Ni], [Mn], [Cr], [Mo], [Si] and [Nb] are the mass fractions of C, Ni, Mn, Cr, Si and Nb in the welding wire, respectively; The weld composition satisfies: 7.8%≤30*[C]+[Ni]+0.5*[Mn]≤12%, [Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al]≤12%, 30*[C]+[Ni]+0.5*[Mn]<-0.76*([Cr]+[Mo]+1.5*[Si]+0.5*[Nb]+5.5*[Al])+0.187, where [C], [Ni], [Mn], [Cr], [Mo], [Si], [Nb] and [Al] are the mass fractions of C, Ni, Mn, Cr, Si, Nb and Al in the weld, respectively. The weld seam is wider on the laser-irradiated side than on the other side; The volume ratio of laser welding wire in the weld is 10% to 70%.

2. The laser welding method for hot-formed steel with aluminum coating according to claim 1, characterized in that, The first aluminum-coated plate to be welded includes a first aluminum-coated layer, and the second aluminum-coated plate to be welded includes a second aluminum-coated layer. By mass fraction, the chemical composition of the first aluminum-coated layer and the second aluminum-coated layer both include: Al: 85%~95%; Si: 5%~15%.

3. The laser welding method for hot-formed steel with aluminum coating according to claim 2, characterized in that, The thickness of both the first aluminum-containing coating and the second aluminum-containing coating is 10μm~100μm.

4. The laser welding method for hot-formed steel with aluminum coating according to claim 1, characterized in that, The carbon equivalent of the welding wire is Ceq0, and the carbon equivalent of the aluminum-coated plate to be welded with high tensile strength is Ceq1, satisfying Ceq1≤Ceq0≤Ceq1+1, where Ceq is calculated as Ceq=[C]+[Mn] / 6+([Cr]+[Mo]) / 5+[Ni] / 15]*100%.

5. The laser welding method for hot-formed steel with aluminum coating according to claim 1, characterized in that, The laser used in the laser welding process includes a central light source and a peripheral light source.

6. The laser welding method for hot-formed steel with aluminum coating according to claim 2, characterized in that, In the welding wire, Ni: >3%, Si: 0.15%~0.8%, Ti: 0.05%~0.5%.

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