阅读说明：本技术 一种Al-Si涂层热成型钢双摆动激光焊接方法 (Double-swing laser welding method for Al-Si coating thermal forming steel ) 是由 李国新 于 2020-12-28 设计创作，主要内容包括：本发明公开了一种Al-Si涂层热成型钢双摆动激光焊接方法,包含第一摆动激光束、第二摆动激光束、Al-Si涂层热压钢板、第一喷嘴和第二喷嘴和；第一摆动激光束横向摆动,形成前置微熔池；第一喷嘴向前置微熔池中送入氧化性粉末和氧化性气体；第二摆动激光束环形摆动,搅拌前置微熔池,形成焊接熔池；第二喷嘴向焊接熔池处吹出惰性气体；本方案将Al-Si涂层打碎并预先反应生成强化相,可以在不去除涂层的条件下直接进行焊接；且部分强化相在焊后会上浮覆盖在熔池表面,成为保护层；利用细小的强化相可增强焊缝力学性能,并减少对其韧性的影响；基体背面涂层不会熔化与熔池混合,在滚轮碾压下结合后强度和抗腐蚀性较好,不需要焊后重新镀层处理。(The invention discloses an Al-Si coating hot-forming steel double-swing laser welding method, which comprises a first swing laser beam, a second swing laser beam, an Al-Si coating hot-pressing steel plate, a first nozzle, a second nozzle and a laser beam; the first swinging laser beam swings transversely to form a front micro molten pool; the first nozzle feeds oxidizing powder and oxidizing gas into the preposed micro-molten pool; the second swinging laser beam swings annularly to stir the preposed micro-molten pool to form a welding molten pool; the second nozzle blows inert gas to the welding pool; according to the scheme, the Al-Si coating is smashed and pre-reacted to generate a strengthening phase, and welding can be directly carried out under the condition that the coating is not removed; part of the strengthening phase floats upwards and covers the surface of the molten pool after being welded to form a protective layer; the fine strengthening phase can be used for enhancing the mechanical property of the welding seam and reducing the influence on the toughness of the welding seam; the back coating of the substrate can not be melted and mixed with a molten pool, and the strength and the corrosion resistance are better after the coating is combined under the rolling of a roller, and the coating treatment is not needed again after welding.)

1. A double-swing laser welding method for Al-Si coating hot forming steel is characterized by comprising the following steps: the laser beam hot-pressing device comprises a first swinging laser beam (1), a second swinging laser beam (2), an Al-Si coating hot-pressing steel plate (3), a first nozzle (4) and a second nozzle (5);

the first swinging laser beam (1) transversely swings at the welding seam of two Al-Si coating hot-pressing steel plates (3) to be welded to form a front micro-molten pool; a first nozzle (4) feeds oxidizing powder and oxidizing gas into the forward micro-bath;

the second swinging laser beam (2) is positioned at the rear side of the first swinging laser beam (1), and the second swinging laser beam (2) swings annularly to stir the preposed micro molten pool to form a welding molten pool; the second nozzle (5) blows inert gas to the welding pool.

2. The double-oscillating laser welding method of Al-Si coated hot-formed steel according to claim 1, characterized in that: the welding position of the second swing laser beam (2) is 2-10mm away from the welding position of the first swing laser beam (1).

3. The double-oscillating laser welding method of Al-Si coated hot-formed steel according to claim 1, characterized in that: the gas flow of the second nozzle (5) is not lower than 20L/min.

4. The double-oscillating laser welding method of Al-Si coated hot-formed steel according to claim 1, characterized in that: the second nozzle (5) simultaneously feeds strengthening elements into the welding pool.

5. The double-oscillating laser welding method of Al-Si coated hot-formed steel according to claim 1, characterized in that: and a rolling roller group (6) is arranged at the downstream of the second swing laser beam (2), and the rolling roller group (6) rolls the welding seam from the upper side and the lower side of the welding seam.

Technical Field

The invention relates to a double-swing laser welding method for Al-Si coating hot-formed steel, and belongs to the technical field of laser tailor-welding.

Background

With the rapid development of economic globalization in recent years, the automobile industry is in a rapid development trend, and the automobile popularity is higher and higher. The popularization of automobiles is more convenient for people to go out, but simultaneously brings great influence to the global environment, the energy consumption causes crisis, the global warming problem caused by the large emission of carbon dioxide is more and more serious, people are enabled to recognize the importance of the environment and resources, and the energy-saving and environment-friendly concept becomes the mainstream of the future development of the automobile industry. For the aspect of improving the energy conservation and emission reduction of the automobile, the light weight of the automobile is the most effective and direct mode, according to the automobile design theory, when the mass of the automobile is reduced by 10 percent, the fuel oil is reduced by 8 to 10 percent, the exhaust emission can be reduced by 5 to 6 percent, and when the weight of the automobile is reduced by 100kg, the efficiency of the combustible oil is improved by 1.3 km/L. The automobile is light in weight, the automobile body mass can be reduced, the running fuel is reduced, energy is saved, the environment is protected, the safety of the automobile can be guaranteed, and the optimization of cost and benefit can be realized. The Al-Si coating hot-pressed steel plate becomes an important material for manufacturing structural parts of automobiles due to the advantages of high tensile strength, high hardness, high energy absorption rate and the like after hot forming. The strength of the material after hot forming reaches more than 1600MPa, and under the same strength, the material usage amount can be greatly reduced, thereby achieving the aim of light weight of automobiles. The Al-Si coating on the surface of the steel plate also obviously improves the corrosion resistance of the material, so the popularization and the application of the Al-Si coating hot-pressed steel plate become the development focus of the automobile manufacturing industry.

Laser welding has become the support technology of modern automobile manufacturing because of its advantages such as welding quality is high, efficiency is fast. Compared with the traditional welding, the characteristic of large depth-to-width ratio of laser welding can realize single-side welding, and the problems of groove processing and welding space are solved; the small heat affected zone of the welding seam enables the car body to have no deformation such as electric welding, distortion after arc welding, wave and the like after welding, and can ensure the strength of a weldment; the characteristic of high energy density makes the welding seam easily melt through, has improved welding speed, and automobile production efficiency improves. When the Al-Si coating hot-pressed steel plate is subjected to laser welding, the coating melts and flows into a welding line along with a molten pool, and the structural performance of a welding joint is greatly influenced. Cracks are easily generated on the inner side of the coating due to the difference in thermal expansion coefficient between aluminum and steel. The aluminum and the silicon in the aluminum-silicon coating are solid-dissolved to the welding seam in a solid state, most of the aluminum and the silicon react with the iron to generate intermetallic compounds distributed along the welding seam, and the strength of the joint is reduced

At present, laser tailor-welding is usually carried out by completely or partially removing an aluminum-silicon coating and then welding, for example, in patent CN201820369269.0, an aluminum-silicon coating on the surface of a steel plate in a welding operation area is removed by a certain method, so as to reduce the negative effects caused by aluminum residues in weld metals. However, such a method increases the production cost, and the welded seam becomes a weak point of corrosion resistance, and requires additional processes. Therefore, the development of suitable welding materials and welding methods for directly welding the Al-Si coating hot-pressed steel plate is needed. Based on the method, the invention provides a double-swing laser welding technology of Al-Si coating hot forming steel added with alloy elements.

Disclosure of Invention

In view of the above technical problems, the present invention aims to: provides a double-swing laser welding method for Al-Si coating hot forming steel.

The technical solution of the invention is realized as follows: a double-swing laser welding method for Al-Si coating hot-forming steel comprises a first swing laser beam, a second swing laser beam, an Al-Si coating hot-pressing steel plate, a first nozzle and a second nozzle; the first swinging laser beam transversely swings at the welding seam of the two Al-Si coating hot-pressed steel plates to be welded to form a front micro-molten pool; the first nozzle feeds oxidizing powder and oxidizing gas into the preposed micro-molten pool; the second swinging laser beam is positioned at the rear side of the first swinging laser beam, and the second swinging laser beam swings annularly to stir the preposed micro molten pool to form a welding molten pool; the second nozzle blows inert gas to the welding pool.

Preferably, the welding position of the second oscillating laser beam is 2-10mm away from the welding position of the first oscillating laser beam.

Preferably, the gas flow rate of the second nozzle is not lower than 20L/min.

Preferably, the second nozzle simultaneously feeds the strengthening element into the weld pool.

Preferably, a rolling roller group is arranged at the downstream of the second swinging laser beam, and the rolling roller group rolls the welding seam from the upper side and the lower side of the welding seam.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

firstly, the Al-Si coating is broken and pre-reacted to generate a strengthening phase, so that the Al-Si coating can be directly welded under the condition of not removing the coating, and the production process and the cost are reduced; and part of the strengthening phase can float upwards to cover the surface of the molten pool after welding to form a protective layer with certain corrosion resistance.

Secondly, the mechanical property of the welding seam can be enhanced by utilizing a fine strengthening phase, and the influence on the toughness of the welding seam is reduced; strengthening element additions may also be employed at the rear to further enhance the toughness and corrosion resistance of the weld.

The back coating of the substrate can not be melted and mixed with a molten pool, and the strength and the corrosion resistance are better after the coating is combined under the rolling of a roller, and the coating treatment is not needed again after welding.

Drawings

The technical scheme of the invention is further explained by combining the accompanying drawings as follows:

FIG. 1 is a schematic diagram of a double-swing laser welding method for Al-Si coating hot forming steel.

Detailed Description

The invention is described below with reference to the accompanying drawings.

As shown in attached figure 1, the double-swing laser welding method for the Al-Si coating hot forming steel comprises a first swing laser beam 1, a second swing laser beam 2, an Al-Si coating hot-pressing steel plate 3, a first nozzle 4, a second nozzle 5 and a rolling roller group 6.

The working principle of the welding method is as follows:

the sheet material and the laser beam are continuously moved relatively, the arrow in the figure is the welding direction, and during actual welding, the sheet material is generally moved, and the moving direction of the sheet material is opposite to the arrow in the figure.

The first swinging laser beam 1 swings transversely during welding to form a preposed micro-molten pool, a band-shaped heat source is obtained by modulating the waveform, the preposed micro-molten pool with consistent fusion depth is obtained along with continuous relative movement, the fusion depth of the preposed micro-molten pool is similar to the thickness of an Al-Si coating of a plate, and a slightly larger coating is required to be adopted for plate welding according to the requirement of plate weldingA molten pool of thickness, or a molten pool slightly less than the molten pool thickness; simultaneously feeding oxidizing powder and oxidizing gas into the micro-molten pool from a first nozzle 4, wherein the first nozzle 4 is transversely arranged and vertical to the welding moving direction, and the oxidizing powder includes but is not limited to Fe₂O₃And the coating is remelted and oxidized to generate strengthened particles of aluminum oxide and the like in micron or even nanometer scale.

The preposed micro-melting pool can play a preheating role, welding is carried out by using a swinging laser beam 2 before cooling is finished, a second swinging laser beam 2 is placed 2-10mm behind a first swinging laser beam 1, and the second swinging laser beam 2 is welded in an annular swinging mode; the circular oscillation is beneficial to further stirring the molten pool, further breaking up larger particle phases and preventing the formation of large-size brittle phases.

The second nozzle 5 is placed along the welding direction, the second nozzle 5 is protected by inert gas, the flow rate is not lower than 20L/min, and in order to prevent the two protective gases from interfering, the flow rate of the protective gases depends on the distance of the laser beams; the protective gas of the second nozzle 5 is used for protecting the welding pool, and the residual powder of the front-located pool is directly cleaned by using larger gas flow to prevent excessive oxides from entering the welding pool; meanwhile, the second nozzle 5 can also be set to send powder, and strengthening elements such as manganese, chromium, boron, nitrogen and the like are added into the molten pool to improve the mechanical property of the welding seam.

The depth of a molten pool formed by the annular oscillation laser is controlled at the micro penetration degree, namely, the bottom end of the molten pool is contacted with the Al-Si coating on the back surface, but the Al-Si coating is not melted and rolled into the molten pool, the coating is softened or in a semi-melting state by heat conduction, and the bonding is realized under the rolling of the rolling roller group 6 on the rear side.

Wherein the laser can adopt CO₂Gas laser, YAG solid laser, semiconductor laser; the powder feeder can be a domestic or imported powder feeder, and the particle size of the powder is 10-200 mu m; the adjustment of the process parameters in the welding process is realized by programming of the KUKA robot.

The specific welding working steps are as follows:

the method comprises the steps of firstly, machining the part to be welded of a plate workpiece into required precision according to requirements, and polishing or cleaning the surfaces of two sides of the machined workpiece.

And secondly, fixing the polished or cleaned workpiece to be welded on a welding tool fixture, and tightly butting the workpiece to be welded with the gap of 0 without forming a groove or a V-shaped groove.

Setting welding parameters, wherein the defocusing amount of laser is minus 5-plus 5mm, the power of a front laser beam is 300-1500W, the power of a rear laser beam is 1000-5000W, the welding speed is 1-8 m/min, the center distance of double beams is 2-10mm, the swing frequency of the front laser is 50-300 Hz, and the swing frequency of the rear laser is 100-250 Hz; the pre-shielding gas is an oxidizing gas including but not limited to Ar + O₂、Ar+CO₂And the flow rate is 5-15L/min, the pre-powder feeding powder is oxide particles including but not limited to Fe₂O₃And the powder feeding amount is 0.1-5 g/min; the rear protective gas adopts Ar gas or Ar/He mixed gas and the like, and the flow rate is 20-60L/min; the post-positioned powder feeding powder can adopt simple substance or compound powder of Mn, Cr, B and the like, the particle size of the powder is 10-40 mu m, and the powder feeding amount is 3-15 g/min; the diameter of the roller is 30-80 mm, and the pressure of the roller is 400N-3 kN.

And fourthly, in the actual welding process, controlling welding technological parameters by adopting a robot integrated system, firstly introducing shielding gas and powder, presetting pressure on a roller, then controlling a laser to emit laser, and finally controlling a robot to enable a welding head to move to finish the welding process.

The following two conventional welding modes are compared with the technical effect of the scheme:

welding a 2mm thick Al-Si coating hot-pressed steel plate butt joint with a coating by conventional laser welding:

the method comprises the steps of firstly, machining the part to be welded of the workpiece into required precision according to the requirement, and polishing or cleaning the surfaces of two sides of the machined workpiece.

And step two, fixing the polished or cleaned workpiece to be welded on a welding tool fixture, and tightly butting the workpiece to be welded with a gap of 0 without forming a groove.

Setting welding parameters, wherein the defocusing amount of laser is 0mm, the laser power is 1800W, and the welding speed is 1.5 m/min. Ar gas is used as the protective gas, and the flow rate is 25L/min.

And fourthly, in the actual welding process, controlling welding process parameters by adopting a robot integration system, firstly controlling to emit laser, and then controlling the robot to enable a welding head to move to finish the welding process.

Welding an Al-Si coating hot-pressed steel plate butt joint with a thickness of 2mm and completely removed with a coating by conventional laser welding:

the method comprises the steps of firstly, machining the part to be welded of the workpiece into required precision according to the requirement, and polishing or cleaning the surfaces of two sides of the machined workpiece.

And step two, fixing the polished or cleaned workpiece to be welded on a welding tool fixture, and tightly butting the workpiece to be welded with a gap of 0 without forming a groove.

Setting welding parameters, wherein the defocusing amount of laser is 0mm, the laser power is 1600W, and the welding speed is 1.5 m/min. Ar gas is used as the protective gas, and the flow rate is 25L/min.

And fourthly, in the actual welding process, controlling welding process parameters by adopting a robot integration system, firstly controlling to emit laser, and then controlling the robot to enable a welding head to move to finish the welding process.

Welding a 2mm thick Al-Si coating hot-pressed steel plate butt joint with a coating by the method:

the method comprises the steps of firstly, machining the part to be welded of the workpiece into required precision according to the requirement, and polishing or cleaning the surfaces of two sides of the machined workpiece.

And step two, fixing the polished or cleaned workpiece to be welded on a welding tool fixture, and tightly butting the workpiece to be welded with a gap of 0 without forming a groove.

Setting welding parameters, wherein the defocusing amount of laser is 0mm, the power of a laser beam 1 is 600W, the power of a laser beam 2 is 1600W, the welding speed is 1.5m/min, the central distance of double beams is 4mm, the swinging frequency of the front laser is 200Hz, and the swinging frequency of the rear laser is 100 Hz; the preposed protective gas adopts a mixed gas of 80% Ar and 20% CO2, the flow rate is 10L/min, and the preposed powder feeding powder is Fe2O 3; the rear protective gas adopts Ar gas or Ar/He mixed gas and the like, and the flow rate is 25L/min; the powder is a mixture of Mn and B simple substances, and the particle size of the powder is 20 μm. The diameter of the roller is 40mm, and the pressure of the roller is 600N.

And fourthly, in the actual welding process, controlling welding technological parameters by adopting a robot integrated system, firstly introducing shielding gas and powder, presetting pressure on a roller, then controlling a laser to emit laser, and finally controlling a robot to enable a welding head to move to finish the welding process.

The mechanical properties of the samples welded under the three conditions were tested, and the results were as follows:

according to the test result, the tensile strength of the sample is reduced after the conventional laser welding, but the use requirement is also met, and the elongation rate is reduced, namely the plasticity is reduced, and the qualification rate of the cupping test is only 74%; after the method is adopted for welding, the tensile strength is close to the result of conventional laser welding after the coating is completely removed in the prior art, the elongation is obviously higher than that of the conventional laser welding, the qualification rate of the cupping test also reaches 100 percent, the influence caused by the fact that coating elements are fused into a welding line after being treated is controllable, and the performance of a sample reaches the qualified standard.

The above-mentioned embodiments are merely illustrative of the technical idea and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered in the scope of the present invention.