CN115255715A

CN115255715A - Alloy welding wire for laser welding and method for improving strength of aluminum-boron-plated steel welding seam

Info

Publication number: CN115255715A
Application number: CN202211021746.1A
Authority: CN
Inventors: 黄圣坤; 曹伟业
Original assignee: Hunan Ruihua New Material Co ltd
Current assignee: Hunan Ruihua New Material Co ltd
Priority date: 2022-08-24
Filing date: 2022-08-24
Publication date: 2022-11-01
Anticipated expiration: 2042-08-24
Also published as: CN115255715B

Abstract

The invention belongs to the field of laser welding processing, and particularly discloses an alloy welding wire for laser welding and a method for improving the strength of a welding seam of aluminized boron steel; the alloy welding wire for laser welding comprises the following components in percentage by mass: c:0.205 to 0.219wt%, cr:1.26 to 1.34wt%, ni:5.25 to 5.60wt%, mn:3.05 to 3.15wt%, nb:0.10 to 0.12wt%, si:0.10 to 0.15 weight percent of Fe and the balance of Fe; the invention also discloses a method for improving the weld strength of the laser welding aluminum-boron-plated steel by using the alloy welding wire, which can eliminate the pain point of the weld strength reduction under the condition of not removing the aluminum plating layer or reducing the thickness of the aluminum plating layer, and incidentally also solves the welding defects of pits, undercuts and the like caused by the clamping gap error of the steel plate during butt welding; the alloy welding wire has the advantages that the welding seam strength is guaranteed from two aspects, meanwhile, the alloy welding wire can be directly coupled to a laser welding process, the welding process is not increased, the production flow is not changed, the production cost is effectively controlled, in addition, the welding wire is low in cost, and the processing and the manufacturing are easy.

Description

Alloy welding wire for laser welding and method for improving strength of aluminum-boron-plated steel welding seam

Technical Field

The invention belongs to the field of laser welding processing, and particularly discloses an alloy welding wire for laser welding and a method for improving the strength of a welding seam of aluminized boron steel.

Background

With the vigorous development of the automobile industry in China, the fuel economy and the driving safety of automobiles are more and more emphasized by people, and for automobile bodies, the improvement of the strength of steel plates becomes the mainstream design direction of the lightweight technology of the automobiles while the thickness of the steel plates is reduced, so that the use of the ultrahigh-strength boron steel plates of 1.5GPa on front and rear anti-collision beams and A, B and C columns of the automobiles is more and more common.

Laser welding steel sheets has numerous advantages: the method has the advantages of small thermal deformation, attractive weld joint forming, high welding efficiency, no need of lap welding, steel plate consumption saving and convenience for lightweight design. On the other hand, aluminum (silicon) plating is often used to protect boron steel during hot press forming in order to protect the boron steel surface from oxidation and decarburization. The technological process of the technology comprises the following steps: aluminizing boron steel, laser welding, heating by a resistance furnace at 930 ℃ and keeping the temperature for about 5 minutes, hot stamping and forming, and air cooling, as shown in figure 1. However, when mechanical property tests are carried out on the finished product, the tensile fracture position is in a welding seam, and the average hardness of the area is far lower than that of a heat affected zone and a base material. Further observation of this region revealed that: 1) This region had an uneven distribution of aluminum elements (Al: 0.1wt% to 1.5wt%, and an aluminum plating thickness of about 20 μm); 2) The decarburization is serious; 3) The ferrite phase is abundant, as shown in fig. 2 and 6. It was also found that the area with severe decarburization and the area with more ferrite had a higher content of aluminum element and exhibited high coincidence, and boron steel did not contain aluminum element, so that these aluminum elements were caused by the aluminum element of the plating layer being mixed into the weld during welding.

Some attempts to replace the aluminum-plated plate with a galvanized plate have been made, but the melting point of zinc is only 419.5 degrees, and most of the plating layer is gasified during laser welding and thermal insulation at a backward temperature of 930 degrees, so that the steel plate is not protected. Nickel plating, chromium plating, and copper plating have also been proposed to replace aluminum plating but are not known due to problems such as cost and segregation after welding.

With the progress of research, people generally know that aluminum plating and aluminum segregation are main contradictions causing the low strength of welding seams, so the solution mainly focuses on two aspects of removing or reducing the thickness of the aluminum plating; for example, a patent application No. 201911122011.6 of the chinese invention discloses a dual beam tailor welding method of a hot-formed steel sheet with an Al-Si plating layer. The patent uses a double-beam method to achieve the purpose of reducing aluminum segregation, and specifically uses a front beam to convert an aluminum-plated layer into a Fe-Al intermetallic compound, and then uses a rear beam to perform tailor welding. The applicant has also carried out similar tests with this method, with the main problems concentrated on the following two aspects: (1) If the effective scanning width of the front beam is larger than that of the rear beam, a partial area of the base material is not effectively protected during the subsequent thermal forming treatment, and oxidation and decarburization are easy; if the effective scanning width of the front beam is equal to or less than that of the back beam, segregation still exists after the back beam speed stitch welding because the segregation position is mainly concentrated near the fusion line; (2) The aluminized steel plate is double-sided aluminized, after the front side is scanned and spliced, the back side also needs to be scanned and spliced, and the scanning and splicing are performed twice, so that the welding defects such as undercut, pits and the like are aggravated, even if the front side and the back side of the steel plate are scanned first and then spliced again, the low efficiency and the clamping error caused by two times of steel plate clamping also cause the instability of the product quality. < B > without removing the aluminized layer, aluminum segregation in the weld was reduced by the facility means. For example, the patent application document with the Chinese invention patent application number of 201910949005.1 discloses a pulse tailor welding method for a hot-formed steel plate with an Al-Si coating. The patent eliminates segregation of aluminum elements by melting the melt pool with peak and trough power generated by a pulsed laser. Because the wave crest power of the pulse laser can melt steel instantly but the wave trough power cannot melt, the defects that the molten metal liquid in the subsequent melting state cannot be supplemented to the molten liquid metal in the prior art, and in addition, the melting and the solidification are too fast, so that the welding seam generates air holes, slag inclusion and the like are caused, moreover, the segregation degree of the aluminum element has a direct relation with the welding speed, the reason is that the cooling speed is accelerated when the welding speed is too fast, the volume of the welding seam can be reduced, the aluminum element mixed into the welding seam does not have time and space to diffuse, the concentration of the aluminum element is increased, and the segregation is intensified. The pulse laser is generally not applied to the field of automobile welding, and the industrial factory requires the stable reliability of the product quality, and the requirement on the laser is that the energy output must have continuous stability, and the laser power cannot swing to a large extent.

In summary, the solutions provided by the prior art mainly focus on how to "replace or control aluminum", and these methods cannot completely replace or remove aluminum element in the weld joint, and even cannot prevent the strength of the weld joint from decreasing. Because: firstly, the scheme of replacing aluminum has the problem of industrial application, and secondly, the aluminum-plated layer and the base material have undergone chemical reaction and are integrated; secondly, the cooling speed of laser welding is too high, the aluminum element does not have time to be fully diffused and dissolved, and the heat treatment within minutes cannot be solved; third, neither solution completely blocks the presence of elemental aluminum in the weld.

Disclosure of Invention

In order to solve the problems, the invention discloses an alloy welding wire for laser welding and a method for improving the strength of a welding seam of aluminum-boron-plated steel.

The technical scheme of the invention is as follows:

an alloy welding wire for laser welding contains the following components in percentage by mass:

c:0.205 to 0.219wt%, cr:1.26 to 1.34wt%, ni:5.25 to 5.60wt%, mn:3.05 to 3.15wt%, nb:0.10 to 0.12wt%, si:0.10 to 0.15 weight percent of Fe and the balance of Fe.

Further, the alloy welding wire for laser welding is applied to the field of laser welding processing in the automobile industry.

Further, in the application, the alloy welding wire is used for improving the strength of the welding seam of the aluminized boron steel during laser welding.

Further, in the application, the aluminum-boron-plated steel is 20MnTiB.

In the above application, the aluminum-plated boron steel has an aluminum plating layer thickness of 20 to 25 μm.

Further, the method for improving the strength of the welding seam of the aluminum-boron-plated steel by using the laser welding wire comprises the following steps of:

1) Selecting a 20MnTiB series aluminum-boron-plated steel plate with a workpiece thickness of 1.0-1.4mm and a coating thickness of 20-25 mu m;

2) Fixing the steel plate on a clamp, and butting and clamping the steel plate;

3) YAG or fiber laser with spot diameter of 0.6-0.7mm and power of 3000-3500W, welding speed of 1.0-1.7m/min, argon flow rate of 15-20L/min, and laser inclination angle of 5 deg;

4) Selecting an alloy welding wire with the diameter of 0.5-0.6mm, wherein the wire feeding speed is 0.7-1.2m/min, the wire feeding angle is 35-40 degrees, and the filament polishing distance is 0mm;

5) Planning a welding path, welding, directly putting the steel plate into a resistance furnace at 930 +/-10 ℃ after welding, heating for 5-7 minutes, and hot stamping and forming in air after discharging.

A chinese invention patent application No. 201380001259.1 discloses a tailor welded blank, a method of manufacturing the same, and a hot stamped part using the tailor welded blank. From the information provided in this patent it can be seen that: 1) The content provided by the patent uses a laser filler wire welding technology to solve the problem of increase of aluminum elements in a welding seam in the welding process of aluminum-boron-plated steel; 2) The design idea of the alloy welding wire provided by the patent is that austenite stabilizing elements are used for reducing ferrite stabilizing elements in a welding seam; 3) The content of carbon and manganese elements in the welding wire is higher than that of the carbon and manganese elements in the base material.

The filler wire component provided in the patent and the alloy wire component provided in the invention are essentially different in element selection, design thought and microstructure: first, the elements carbon and manganese are inherent elements that must be present in all steel and iron-based welding materials. Secondly, the carbon component and the manganese component of the alloy welding wire provided by the invention are respectively 0.1wt% to 0.8wt% and 1.5wt% to 7.0wt% higher than the corresponding elements of the base material, and the elements provided by the invention not only comprise carbon and manganese elements, but also comprise nickel, chromium, niobium and silicon elements. The patent provides a composition mainly for suppressing the formation of ferrite elements, and the present invention adds ferrite-forming elements such as chromium, niobium, silicon, etc., and further, the present invention provides a carbon element content outside the range described in the patent. Again, the invention has been specifically described for "a component system that does not produce a ferrite structure in the temperature range from 800 ℃ to 950 ℃; the concept of filler wire with a greater amount of austenite stabilizing elements is the same as the prior art approach of "aluminum control" using laser equipment or processes, since aluminum is a ferrite stabilizing element. The design idea of the invention is to improve the toughness of the welding seam by fixing carbon and introducing a proper amount of ferrite phase. Therefore, the alloy system provided by the invention is composed of an austenite forming element, a ferrite forming element and a carbide forming element. This is one of the most fundamental distinguishing features from this patent. Finally, the alloy components provided by the invention cannot solve the problem of the reduction of the strength of the boron steel weld joint, and the reasons are as follows:

1) As described above, the invention provides high contents of carbon and manganese, which will depress the martensitic transformation temperature to cause the existence of a large amount of retained austenite phase, the hardness of austenite phase is lower, which will directly cause the decrease of the strength of the welding seam, and it is known that the hardness in the welding seam is only 317Hv and the retained austenite content is as high as 72.6v% by CCT curve simulation according to the embodiment provided by the invention, as shown in FIG. 8. Therefore, the patent is to inhibit the ferrite phase in order to inhibit the ferrite phase, but not to solve the practical engineering problem, and the design idea of the alloy is seriously contrary to the basic principle of material phase transformation, which leads to the deterioration of the weld structure, because if the martensite phase transformation temperature is too low, the residual austenite phase and the martensite phase are directly subjected to phase transformation reaction in the room temperature environment, which causes the rebound phenomenon of the hot stamping formed automobile parts, and more seriously, the unsafe factors increase for the engineering materials, which is absolutely strictly prohibited in any industry.

2) In the case of boron steel having an aluminum layer thickness of 20 to 30 μm, which is generally used in the automobile industry, the applicant found in experiments that if the aluminum segregation amount in the weld bead is increased exponentially up to 5.1wt% at a coating thickness of 27 μm or less and a welding speed of 3m/min or more, even if the weld bead composition of 0.8wt% carbon +7.0wt% manganese provided in the patent is used and heat-treated at 950 degrees or less, the weld bead still has a large amount of ferrite phase (about 47v% or less), as shown in fig. 9, which is contrary to the original design of the alloy composition provided in the patent, and the weld microstructure is further deteriorated by the generation of a large amount of brittle phase. No limitations are disclosed in the contents of this patent, which means that the information provided by this patent document is not ubiquitous and violates the basic requirements of patent laws that "one of ordinary skill in the art can" achieve "the right.

3) In order to prevent cracking of alloy structural steel materials during welding or heat treatment in the automobile industry, medium and low carbon hypoeutectoid steel with carbon content below 0.45wt% is generally selected. The carbon content disclosed in the patent is up to 0.8wt%, and the carbon content belongs to the category of hypereutectoid steel, so that the cracking phenomenon is easy to occur during actual welding, and the brittleness of a welding line is very high during the application of an automobile body, so that safety accidents are easy to occur. This is in contrast to the "component system which does not generate a ferrite structure upon heat treatment" in the context of the invention; this is closely related to the design concept of having a higher number of austenite stabilizing elements. Only carbon fixation design can balance the contradiction between high strength and no cracking. This is also one of the most distinctive features between the technology provided by this patent and the prior art.

In summary, the solutions provided by the prior art mainly focus on how to "replace or control aluminum", and these methods cannot completely replace or remove aluminum element in the weld joint, and even cannot prevent the strength of the weld joint from decreasing. Because: firstly, the aluminum-replacing scheme has the problem of industrial application, and secondly, the aluminum-plated layer and the base material have undergone chemical reaction and are integrated; secondly, the cooling speed of laser welding is too high, aluminum element does not have time to be fully diffused and dissolved, and the heat treatment within minutes cannot be solved; third, neither solution completely blocks the presence of elemental aluminum in the weld. The invention is different from the prior art, focuses on solving the problems in alloying, and particularly focuses on how to construct an alloy system to dissolve more carbon elements in a solid solution manner, and then utilizes the high strengthening effect of the carbon elements to promote a proper amount of high-hardness strengthening structures to be generated in the welding seam, so that the strength of the welding seam can be improved.

The invention has the following beneficial effects:

1. the method for improving the weld strength of the laser welding aluminum-boron-plated steel by using the alloy welding wire can eliminate the pain point of the weld strength reduction under the condition of not removing the aluminum plating layer or reducing the thickness of the aluminum plating layer. By the way, the welding defects of pits, undercuts and the like caused by the clamping clearance error of the steel plates during butt welding are overcome. The weld strength is ensured from two aspects. Compared with the zinc plating, chromium plating, nickel plating and copper plating technologies, the method has the beneficial effect of saving cost.

2. According to the method for improving the strength of the welding seam of the laser welding aluminum-plated boron steel by using the alloy welding wire, the alloy welding wire can be directly coupled to the laser welding process, the welding process is not increased, the production flow is not changed, and the production cost is effectively controlled. Moreover, the welding wire is low in cost and easy to process and manufacture.

Drawings

FIG. 1 is a schematic illustration of a laser filler wire welding and hot stamping process;

FIG. 2 is a binary phase diagram prepared from the composition of a weld using the prior art with 1.5wt% segregation of aluminum and no wire fill;

FIG. 3 is a binary phase diagram prepared according to the components of the weld when the segregation amount of aluminum element is 1.5wt% and the dilution ratio of the welding wire is 0% by using the method provided by the present invention;

FIG. 4 is a binary phase diagram prepared according to the components of a weld when the segregation amount of aluminum element is 1.5wt% and the dilution ratio of a welding wire is 50% by using the method provided by the invention;

FIG. 5 is a CCT curve produced according to the components of a welding seam when the segregation amount of aluminum element is 1.5wt% and the dilution ratio of welding wire is 50% by using the method provided by the invention;

FIG. 6 is a graphical representation of microhardness profiles and representative values of welded joint cross sections measured using the prior art;

FIG. 7 is a graphical representation of a measured hardness profile of a cross-section of a weld joint and representative values using the method provided by the present invention;

fig. 8 is a graph of a CCT produced according to an example provided in patent application No. 201380001259.1;

fig. 9 is a binary phase diagram made according to the example provided in patent application No. 201380001259.1.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The reagents or instruments used in the examples of the present invention are not indicated by manufacturers, and are all conventional reagent products commercially available.

In the present invention, the selection of the elements and the content of the alloy wire used for laser welding are as shown in table 1 below.

TABLE 1 selection of elements and element content principles

In order to improve the strength of the welding seam and reduce the segregation amount of aluminum in the welding seam and the dilution rate of welding wires to the maximum extent, the following steps are defined: the thickness of the aluminum plating layer is 20-25 μm, the welding speed is 1.0-1.7m/min, and the laser power is 3000-3500W. The grade of boron steel selected by the invention is commonly used 20MnTiB alloy structural steel, and the measured chemical components and mechanical properties are shown in Table 2. At this time, the relationship among the dilution ratio of the welding wire in the weld, the range of aluminum segregation amount, and the material properties was determined based on the phase transition simulation calculation shown in fig. 2 to 5 and the metallographic and mechanical property indexes actually measured in fig. 6 to 7, as shown in table 3.

TABLE 2 chemical composition and mechanical Properties Table

TABLE 3 relationship among dilution ratio, aluminum segregation amount range, and material properties of the welding wire in the weld

Example 1

A method for improving the strength of a welding seam of aluminum-boron-plated steel by utilizing a laser welding wire comprises the following components:

C：0.205wt％；

Cr：1.26wt％；

Ni：5.25wt％；

Mn：3.05wt％；

Nb：0.10wt％；

Si：0.10wt％；

fe is the rest.

The preparation method of the welding wire can use the existing mature method, comprises the steps of smelting in an electric furnace, cogging, continuous casting and rolling into a wire rod, then drawing, copper plating and winding to form the welding wire for laser welding, and specifically refers to the guide for selecting the welding wire; chemical industry Press 2011.5.

A method for improving the strength of a welding seam of aluminum-boron-plated steel by using a laser welding wire comprises the following steps of:

1) Selecting a 20MnTiB series aluminum-boron-plated steel plate with the workpiece thickness of 1.0mm and the coating thickness of 20 mu m;

2) Fixing the steel plate on a clamp, and butting and clamping the steel plate;

3) YAG or fiber laser with a spot diameter of 0.6mm is selected, the power is 3500W, the welding speed is 1.0m/min, the flow speed of argon protection is 15L/min, and the inclination angle of the laser is 5 degrees;

4) Selecting an alloy welding wire with the diameter of 0.5mm, wherein the wire feeding speed is 0.7m/min, the wire feeding angle is 35 degrees, and the smooth wire distance is 0mm;

5) Planning a welding path, welding, directly putting the steel plate into a resistance furnace at 930 +/-10 ℃ after welding, heating for 5 minutes, and hot-stamping and forming in air after taking out of the furnace.

Example 2

C：0.219wt％；

Cr：1.34wt％；

Ni：5.60wt％；

Mn：3.15wt％；

Nb：0.12wt％；

Si：0.15wt％；

the balance being Fe.

The preparation method of the welding wire can use the existing mature method, comprises the steps of smelting in an electric furnace, cogging, continuous casting and continuous rolling into a coil element, then drawing, copper plating and winding into the welding wire for laser welding, and specifically refers to the guide for selecting welding wires; chemical industry Press 2011.5.

1) A20 MnTiB series aluminum-boron-plated steel plate with the workpiece thickness of 1.4mm and the plating thickness of 25 mu m is selected.

2) Fixing the steel plate on a clamp, and butting and clamping the steel plate;

3) YAG or fiber laser with spot diameter of 0.7mm is selected, power is 3500W, welding speed is 1.7m/min, flow speed of argon protection is 20L/min, and inclination angle of the laser is 5 degrees;

4) Selecting an alloy welding wire with the diameter of 0.6mm, wherein the wire feeding speed is 1.2m/min, the wire feeding angle is 40 degrees, and the distance of a smooth wire is 0mm;

5) Planning a welding path, welding, directly putting the steel plate into a resistance furnace at 930 +/-10 ℃ after welding, heating for 7 minutes, and hot stamping and forming in air after taking out of the furnace.

Example 3

C：0.212wt％；

Cr：1.30wt％；

Ni：5.42wt％；

Mn：3.10wt％；

Nb：0.11wt％；

Si：0.12wt％；

the balance being Fe.

1) A20 MnTiB series aluminum-boron-plated steel plate with the workpiece thickness of 1.2mm and the coating thickness of 22 mu m is selected.

2) Fixing the steel plate on a clamp, and butting and clamping the steel plate;

3) YAG or fiber laser with spot diameter of 0.7mm is selected, the power is 3200W, the welding speed is 1.4m/min, the flow speed of argon protection is 17L/min, and the inclination angle of the laser is 5 degrees;

4) Selecting an alloy welding wire with the diameter of 0.6mm, wherein the wire feeding speed is 0.9m/min, the wire feeding angle is 37 degrees, and the smooth wire distance is 0mm;

5) Planning a welding path, welding, directly putting the steel plate into a resistance furnace at 930 +/-10 ℃ after welding, heating for 6 minutes, and hot-stamping and forming in air after taking out of the furnace.

To summarize:

the invention is based on the principle of material alloying design, and achieves the purpose of improving the strength of a welding seam by a method of filling welding wires with laser; the aluminum plating layer has a segregation problem due to uneven distribution of aluminum elements. Therefore, in order to solve the problem of the decrease in the weld strength by using the alloy welding wire, the first step is to find out the range of the dilution ratio and the segregation under a certain precondition. In other words, if the dilution ratio of the welding wire is above 60%, and the maximum segregation amount of the aluminum element in the welding seam after heat treatment is above 5.1wt%, the alloy welding wire provided by the invention cannot solve the technical problem of the invention. For detailed information, please refer to table 3.

The applicant found on the basis of experiments that: when the laser power is 3000-3500W, the welding speed is 1.0-1.7m/min, the thickness of aluminium layer is 20-25 micrometers, and the heat treatment method is according to the heat treatment system (described in background art) commonly used in automobile industry. The dilution ratio of the wire in the weld is in the range of 0-50%, with the dilution ratio being the smallest near the center line of the weld and the greatest in the fusion zone and heat affected zone. On the other hand, the range of the aluminum segregation amount after the heat treatment is within 1.5wt%, and the distribution rule of the aluminum segregation is more consistent with the dilution distribution rule of the welding wire. According to the data measured by the test (shown in Table 3), the weld strength is unlikely to decrease.

The applicant needs to explain further the main characteristic differences of dilution and segregation in materials science, wherein dilution is the phenomenon that the content of each element in an alloy system is reduced integrally according to a certain proportion, and dilution is inevitable when dissimilar metals are welded. Segregation is that one element in the alloy has too much content in one region, while the other elements have too little content, and each element has no proportional relation. In order to prevent the segregation of the components of the welding wire, the invention uses a large amount of chromium, manganese and nickel elements which have similar physicochemical properties with iron elements, and the three elements also have the functions of solid solution carbon and decarburization prevention, namely, the so-called carbon element homogenization technology, which is already reflected in the hardness distribution diagram of the welding line, as shown in fig. 7.

Different from the prior art: the core design concept of the invention is to preferentially construct a ternary alloying system capable of dissolving more carbon elements in a solid solution manner, and then promote a proper amount of high-hardness strengthening structures to be generated in the welding line by utilizing the high strengthening effect of the carbon elements so as to improve the strength of the welding line. The essential reason for the reduced weld strength is the reduced hardness due to the microstructure transformation. Many people use the mixing of aluminum as a substantial cause of the decrease in the strength of the weld, so the solution focuses on how to reduce the thickness of the aluminum plating layer or control the content of aluminum. This view is clearly limited. First, the thickness of the aluminum plating layer at the upper and lower ends of the heat affected zone is much thinner than the thickness of the aluminum plating layer at the upper and lower ends of the base material, as shown in fig. 6 and 7. This is because the aluminized layer is first removed by the shock wave of the laser during the laser welding, and then the "Key Hole" effect of the laser is used to achieve the purpose of stirring the molten pool and welding. This welding method has achieved the aim of reducing the thickness of the aluminium coating or controlling the content of aluminium elements in the prior art, which is a complete act of several times. Secondly, even without the aluminizing layer, the strength of the weld is lower than that of the base material. This is caused by welding defects such as undercut, pit, etc. due to the decarburization behavior of the weld during heat treatment and clamping gap errors. Finally, no matter which method is used, aluminum elements in the welding seam exist more or less, so the prior art can not fundamentally solve the problem of the strength reduction of the welding seam, and the method of alloying the welding wire can effectively inhibit the generation of low-hardness microstructures, thereby ensuring the uniformity of the hardness and the stability of tensile strength of the welding seam, and only then can the problem of the strength reduction be fundamentally solved.

The above examples are only illustrative of a limited number of preferred embodiments of the present invention, and are described in more detail and detail, but are not to be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. The alloy welding wire for laser welding is characterized by comprising the following components in percentage by mass:

2. Use of the alloy wire of claim 1 in the field of laser welding processing in the automotive industry.

3. The use according to claim 2, wherein the alloy wire is used for improving the weld strength of aluminized and boronated steel when laser welding.

4. Use according to claim 3, characterized in that the aluminized boron steel is of the type 20MnTiB.

5. Use according to claim 4, wherein the aluminized boron steel has an aluminized layer thickness of 20 to 25 μm.

6. A method for improving the strength of a weld of aluminum-boron-plated steel by using a laser welding wire, wherein the alloy welding wire of claim 1 is used, comprising the steps of:

2) Fixing the steel plate on a clamp, and butting and clamping the steel plate;

3) YAG or fiber laser with spot diameter of 0.6-0.7mm is used, power is 3000-3500W, welding speed is 1.0-1.7m/min, flow rate of argon protection is 15-20L/min, and inclination angle of the laser is 5 deg;

4) Selecting an alloy welding wire with the diameter of 0.5-0.6mm, wherein the wire feeding speed is 0.7-1.2m/min, the wire feeding angle is 35-40 degrees, and the smooth wire distance is 0mm;