阅读说明：本技术 基于激光冲击的搅拌摩擦焊接头强化方法 (Laser shock based friction stir welding joint strengthening method ) 是由 李康妹 何幸哲 胡俊 蔡宇 于 2020-05-14 设计创作，主要内容包括：本发明公开了基于激光冲击的搅拌摩擦焊接头强化方法,步骤包括：1)用搅拌摩擦焊技术对金属焊接件进行焊接；2)用角磨机和砂纸去除由于焊接而产生的飞边；3)清洗打磨后的焊缝表面,去除金属颗粒；4)在焊接件焊缝表面上依次铺设吸收层和约束层,将焊接件固定在六轴机器人夹具上,利用激光冲击强化技术冲击焊缝表面,得到强化后的金属焊接件。本发明提供了一种高可控性、高适应性、工序简单、绿色环保的搅拌摩擦焊接头强化方法。(The invention discloses a friction stir welding joint strengthening method based on laser shock, which comprises the following steps: 1) welding a metal welding part by using a friction stir welding technology; 2) removing flash generated by welding by using an angle grinder and sand paper; 3) cleaning the polished surface of the weld joint to remove metal particles; 4) and sequentially laying an absorption layer and a restraint layer on the surface of the weld joint of the welded part, fixing the welded part on a six-axis robot clamp, and impacting the surface of the weld joint by using a laser impact strengthening technology to obtain the strengthened metal welded part. The invention provides a friction stir welding joint strengthening method which is high in controllability and adaptability, simple in process, green and environment-friendly.)

1. A friction stir welding joint strengthening method based on laser shock is characterized by comprising the following steps:

step 1): placing two metal welding parts A (1) to be welded on a friction stir welding workbench, and adjusting welding parameters to weld according to production requirements to obtain a welded metal part B (5);

step 2): removing the flash (2) caused by friction stir welding from the metal welding part B (5) obtained in the step 1) to obtain a polished metal welding part C (7);

step 3): cleaning the surface of the metal welding part C (7) obtained in the step 2), and removing metal particles generated in the polishing process;

step 4): laying an absorption layer (10) on the surface of the welding seam of the metal welding part D (9) obtained in the step 3), wherein the absorption layer is used for absorbing laser energy to generate plasma and form shock waves; a layer of restraint layer (11) is laid above the absorption layer to improve the amplitude of laser impact pressure and prolong the action time of the pressure;

step 5): fixing a metal welding part D (9) paved with an absorption layer (10) and a constraint layer (11), adjusting laser shock parameters according to production requirements, outputting a laser beam (12) by using a laser (13), changing the transmission direction and focusing the laser (12) through an optical device (15), absorbing the laser (12) by the absorption layer (12) through the constraint layer (11), generating plasma explosion to form shock waves, impacting a welding seam (3) of the metal welding part to obtain a metal welding part E (14) subjected to laser shock, and strengthening the physical performance of a stirring friction welding joint of the metal welding part.

2. The laser shock based friction stir weld joint strengthening method according to claim 1, characterized in that in step 1), the metal weld part a (5) is first removed by an angle grinder to remove the flash (2) caused by friction stir welding, and then the residual flash (2) is further ground by sand paper (6).

3. The laser shock based method for strengthening a friction stir weld joint according to claim 1, wherein the surface of the weld is cleaned in step 3) using alcohol as a detergent (8).

4. The laser shock based method for strengthening a friction stir weld joint according to claim 1, wherein the absorbing layer (10) in step 4) is black teflon tape or black paint.

5. The laser shock based friction stir weld joint strengthening method according to claim 1, characterized in that the constraining layer (11) in step 4) is water or optical glass.

6. The laser shock based friction stir weld joint strengthening method of claim 1, wherein the laser (13) in step 5) is a high power Q-switched Nd: YAG laser, and the laser beam energy follows a nearly flat-top profile.

Technical Field

The invention relates to a laser shock based friction stir welding joint strengthening method, and belongs to the technical field of welding.

Background

Friction Stir Welding (FSW) is a new welding process invented in the nineties of the last century where the weld research in the uk was made, belonging to the solid phase welding process. Compared with other welding modes, the friction stir welding utilizes heat generated by friction heat and plastic deformation as a heat source, avoids hot cracks easily occurring in the fusion welding process, has the advantages of good welding seam quality, small residual stress of the welding seam and the like, and is widely applied in the fields of aerospace and automobile manufacturing. However, friction stir welding can only weld some materials with relatively low melting points, most commonly aluminum alloys, due to the low heat source energy introduced. In addition, the heat affected zone at the friction stir welded joint is softened, so that the physical properties of the joint are significantly reduced compared to the base material. Therefore, there is a need to find a process to improve the physical properties of friction stir weld joints.

Currently, laser processing techniques are widely used in the manufacturing field. The Laser processing technology is mainly divided into two types, one is a processing technology using a Laser thermal effect, such as Laser Welding (LW), Laser Cutting (LC), Laser Surface Texturing (LST), Laser thermoforming (LF), and the other is a processing technology using a Laser force effect, such as Laser Shock Peening (LSP), Laser Shock Forming (LSF), Laser Shock Texturing (LST). The laser shock peening technology utilizes the force effect of laser, and can effectively avoid the defect caused by the influence of the heat effect. This technique has a significant advantage: under the action of transient huge laser impact pressure, the surface and the subsurface of the material generate grain refining effect, and a deeper residual compressive stress layer is formed, so that the mechanical and physical properties of the material are enhanced. Therefore, it is a new technical approach to strengthen the friction stir welding joint by using the laser shock technique.

At present, the strengthening method of the friction stir welding joint, such as the invention named as "a method for improving the quality and mechanical properties of the 7XXX aluminum alloy friction stir welding joint" (patent No. 201510139804.4), can be searched, and the strengthening steps are as follows: firstly, carrying out friction stir welding on 7XXX series aluminum alloy, and then cooling to room temperature by using a PAG solution with the concentration of 5% -10%; then placing the aluminum alloy friction stir welding joint in an environment with the temperature of 40-80 ℃ for 2-8640 hours; and slowly heating the aluminum alloy friction stir welding joint to 100-160 ℃, preserving the heat for 2-36 hours, and finally cooling to room temperature. The method can improve the quality of the welding head, effectively regulate and control the state of the precipitation strengthening phase in the welding head and improve the mechanical property of the welding head. However, the method not only consumes long time, but also adopts chemical reagents, and has hidden danger of environmental pollution. As another example, the invention entitled "a method for improving the corrosion resistance of the surface of a heat-treated and strengthened aluminum alloy friction stir welding head" (patent No. 201610704360.9), the strengthening steps are as follows: in the surface area of the obtained aluminum alloy friction stir welding seam, a groove-hole alternate distribution structure is formed, Al86-Ni10-Ce6 amorphous alloy powder and/or Se + Bi powder are added, and the Al86-Ni10-Ce6 amorphous alloy powder and/or the Se + Bi powder are dispersed and distributed on the surface of the welding seam and a shallow area below the surface under the conditions of low temperature and large plastic deformation through secondary friction stir processing, so that the phase change process or partial metallurgical reaction is carried out on the metal in the area. Compared with the original weld joint surface, the method can greatly improve the corrosion resistance of the welded joint. However, the method has many steps, and residual stress is introduced during drilling and grooving, so that other physical properties of the joint are easily reduced. As another invention named as "a method for improving the strength of a friction stir welding joint of non-heat-treated reinforced aluminum alloy" (patent No. 201810666759.1), the reinforcing steps are as follows: concave platforms are respectively processed on the butt joint surfaces of the welded plate pieces according to the plate thickness; respectively clamping the plate with the concave stations on a workbench with a water tank to form a groove along a butt joint line; filling the reinforced phase particles into the groove, compacting, and sealing the notch by using a needleless stirring head; and injecting water into the water tank, and performing multi-pass reciprocating welding along the butt joint line by using a friction stir welding tool. The method is simple to operate, low in investment and easy to implement, but the groove is difficult to machine when the thin plate is welded. Therefore, the friction stir welding joint strengthening method which is simple in process, green and environment-friendly, good in controllability and wide in applicability needs to be invented.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the technical problem of poor physical properties of the existing friction stir welding joint is solved.

In order to solve the technical problem, the invention provides a friction stir welding joint strengthening method based on laser shock, which is characterized by comprising the following steps of:

step 1): placing two metal welding pieces A to be welded on a friction stir welding workbench, and adjusting welding parameters to weld according to production requirements to obtain a metal welding piece B which is welded;

step 2): removing burrs caused by friction stir welding from the metal welding part B obtained in the step 1) to obtain a polished metal welding part C;

step 3): cleaning the surface of the metal welding part C obtained in the step 2), and removing metal particles generated in the polishing process;

step 4): laying an absorption layer on the surface of the weld joint of the metal welding part D obtained in the step 3) for absorbing laser energy to generate plasma and form shock waves; laying a layer of restraint layer above the absorption layer to improve the amplitude of laser impact pressure and prolong the action time of the pressure;

step 5): fixing the metal welding part D paved with the absorption layer and the constraint layer, adjusting laser shock parameters according to production requirements, outputting laser beams by using a laser, changing the transmission direction and focusing the laser beams through an optical device, absorbing the laser beams by the absorption layer through the constraint layer, generating plasma explosion to form shock waves, impacting welding seams of the metal welding part to obtain a metal welding part E subjected to laser shock, and strengthening the physical properties of a friction stir welding joint of the metal welding part.

Preferably, in the step 1), the metal welding piece a is firstly subjected to fillet grinding to remove the flash caused by friction stir welding, and then the residual flash is further ground by using sand paper.

Preferably, alcohol is used as a detergent in the step 3) to clean the surface of the welding part.

Preferably, the absorbing layer in the step 4) is black polytetrafluoroethylene tape or black paint.

Preferably, the constraint layer in the step 4) is water or optical glass.

Preferably, the laser in the step 5) adopts a high-power Q-switched Nd: YAG laser, and the energy of the laser beam follows a nearly flat-top distribution.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention provides a friction stir welding joint strengthening method based on laser shock, which is a brand new friction stir welding joint strengthening process; compared with the existing strengthening process, the process provided by the invention has fewer steps and is simple to operate.

(2) The laser shock peening technology is adopted as a main processing means, so that positions which are not easy to be strengthened by other technologies such as non-planar welding seams such as fillet welding and curved welding seams can be strengthened, and compared with other strengthening technologies, the laser shock peening technology has the advantages of good controllability and wide application range.

(3) The process flow of the invention does not introduce heat sources except for the friction stirring pin, thereby reducing the influence of heat on the welding joint.

(4) The process flow of the invention does not adopt chemical reagents which can pollute the environment, and is environment-friendly and environment-friendly.

Drawings

FIG. 1 is a process flow diagram of a laser shock based method for strengthening a friction stir weld joint according to the present invention;

FIG. 2 is a flow chart of a friction stir welding process;

fig. 3 is a flow chart of laser shock.

Detailed Description

In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.