CN111558777A - Strengthening method of friction stir welded joint based on laser shock - Google Patents

Abstract

The invention discloses a method for strengthening friction stir welded joints based on laser shock. The steps include: 1) welding metal welded parts with friction stir welding technology; 2) removing flashes generated by welding with an angle grinder and sandpaper; 3 ) Clean the polished weld surface to remove metal particles; 4) Lay an absorption layer and a constraint layer on the weld surface of the weldment in turn, fix the weldment on the six-axis robot fixture, and use the laser shock strengthening technology to impact the weld surface. , to obtain a strengthened metal weldment. The invention provides a friction stir welding joint strengthening method with high controllability, high adaptability, simple procedure and environmental protection.

Description

Strengthening method of friction stir welded joint based on laser shock

technical field

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

Background technique

Friction stir welding (FSW) is a new type of welding process invented by the British Welding Institute in the 1990s, which belongs to the solid phase welding process. Compared with other welding methods, friction stir welding uses the heat generated by friction heat and plastic deformation as the heat source, avoiding the hot cracks that are easy to occur during the fusion welding process, and has the advantages of good weld quality and small residual stress in the weld. It has been widely used in aerospace and automobile manufacturing. However, friction stir welding can only weld some materials with relatively low melting points due to the small heat source energy introduced, the most common being aluminum alloys. In addition, the heat-affected zone at the friction stir welded joint is softened, resulting in a significant reduction in the physical properties of the joint compared to the base metal. Therefore, it is necessary to find a process to improve the physical properties of friction stir welded joints.

At present, laser processing technology is widely used in the field of manufacturing. Laser processing technology is mainly divided into two types, one includes laser welding (Laser Welding, LW), laser cutting (Laser Cutting, LC), laser surface texture (Laser Surface Texturing, LST), laser thermoforming (Laser Forming) , LF) and other processing technologies that utilize laser thermal effect, one includes Laser Shock Peening (LSP), Laser Shock Forming (LSF), Laser Surface Texturing (LST), etc. Processing technology using laser force effect. The laser shock strengthening technology uses the force effect of the laser, which can effectively avoid the defects caused by the thermal effect. This technology has a significant advantage: under the action of instantaneous huge laser shock pressure, the surface and sub-surface of the material will have a grain refinement effect, and a deep residual compressive stress layer will be formed, thereby enhancing the mechanical and physical properties of the material . Therefore, the use of laser shock technology to strengthen the friction stir welding joint will be a new technical means.

At present, relevant strengthening methods of friction stir welded joints can be retrieved, such as the invention entitled "A method for improving the quality and mechanical properties of 7XXX aluminum alloy friction stir welded joints" (Patent No.: 201510139804.4). The strengthening steps are as follows: first The 7XXX series aluminum alloys are subjected to friction stir welding, and then cooled to room temperature with a PAG solution with a concentration of 5%-10%; The aluminum alloy friction stir welded joint is slowly heated to 100 to 160° C., kept for 2 to 36 hours, and finally cooled to room temperature. The method can not only improve the quality of the welded joint, but also effectively control the state of the precipitation strengthening phase in the welded joint, thereby improving the mechanical properties of the welded joint. However, this method is not only time-consuming, but also uses chemical reagents, which has potential pollution to the environment. Another example is the invention titled "A method for improving the surface corrosion resistance of aluminum alloy friction stir welded joints by heat treatment" (patent number: 201610704360.9), the strengthening steps are as follows: in the surface area of the obtained aluminum alloy friction stir welded Open a slot-hole alternate distribution structure and add Al86-Ni10-Ce6 amorphous alloy powder and/or Se+Bi powder to it, and make Al86-Ni10-Ce6 amorphous alloy powder and/or Se through secondary friction stir processing The +Bi powder is dispersed and distributed on the surface of the weld and the shallower area below the surface under the condition of lower temperature and large plastic deformation, and undergoes a phase transformation process or partial metallurgical reaction with the metal in this area. Compared with the original weld surface, this method can greatly improve the corrosion resistance of the welded joint. However, this method has many steps, and introduces residual stress during drilling and grooving, which easily reduces other physical properties of the joint. Another example is the invention named "a method for improving the strength of non-heat-treated strengthened aluminum alloy friction stir welded joints" (patent number: 201810666759.1), the strengthening steps are as follows: according to the thickness of the plate, the concave table is respectively processed on the butt surface of the welded plate; Clamp the plate with the concave table on the worktable with the water tank to form a groove along the butt line; fill the reinforcing phase particles into the groove, compact, and use the needleless stirring head to close the groove. Closed; water is poured into the water tank, and multi-pass reciprocating welding is performed along the butt wire with a friction stir welding tool. This method is simple in operation, low in investment and easy to implement, but it is difficult to process grooves when welding thin plates. Therefore, it is necessary to invent a friction stir welding joint strengthening method with simple process, green environmental protection, good controllability and wide applicability.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is the technical problem of poor physical properties of the existing friction stir welded joints.

In order to solve the above-mentioned technical problems, the present invention provides a method for strengthening friction stir welded joints based on laser shock, which is characterized by comprising the following steps:

Step 1): place the two pieces of metal weldment A to be welded on the friction stir welding workbench, adjust the welding parameters for welding according to production requirements, and obtain the welded metal weldment B;

Step 2): remove the flash caused by friction stir welding from the metal weldment B obtained in step 1) to obtain the polished metal weldment C;

Step 3): cleaning the surface of the metal weldment C obtained in step 2) to remove the metal particles generated during the grinding process;

Step 4): a layer of absorption layer is laid on the surface of the welding seam of the metal weldment D obtained in step 3), the function is to absorb laser energy to generate plasma and form shock waves; a confinement layer is laid on the absorption layer to improve the laser shock The amplitude of the pressure and prolong the pressure action time;

Step 5): Fix the metal weldment D on which the absorption layer and the constraining layer are laid, adjust the parameters of the laser shock according to the production needs, and use the laser to output the laser beam. The layer is absorbed by the absorption layer, and a plasma explosion is generated to form a shock wave, which impacts the weld of the metal weldment to obtain the metal weldment E after laser shock, and the physical properties of the friction stir welded joint of the metal weldment are strengthened.

Preferably, in the step 1), the metal welding piece A is first used an angle grinder to remove the burrs caused by friction stir welding, and then the residual burrs are further polished with sandpaper.

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

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

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

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

Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention proposes a method for strengthening friction stir welded joints based on laser shock, which is a brand-new friction stir welding seam strengthening process; compared with the existing strengthening process, the present invention proposes fewer process steps and is simple to operate .

(2) The present invention adopts laser shock strengthening technology as the main processing method, which can strengthen positions that are not easy to be strengthened by other processes such as fillet welding and other non-planar welds, curved welds, etc. Compared with other strengthening processes, it has The advantages of good controllability and wide application range.

(3) In the process flow of the present invention, no heat source other than the friction stirring needle is introduced, which reduces the influence of heat on the welded joint.

(4) The process flow of the present invention does not use chemical reagents that will pollute the environment, and is environmentally friendly and environmentally friendly.

Description of drawings

1 is a process flow diagram of a laser shock-based friction stir welded joint strengthening method provided by the present invention;

Fig. 2 is the flow chart of friction stir welding process;

Figure 3 is a flow chart of laser shock.

Detailed ways

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

Example

A method for strengthening friction stir welded joints based on laser shock:

Step 1: place the two pieces of metal weldment A1 to be welded on the friction stir welding workbench, adjust the welding parameters for welding according to production requirements, and obtain the welded metal weldment B5; the stirring head 4 is used during welding;

Step 2: Use an angle grinder to remove the flash 2 caused by friction stir welding on the metal weld B 5 obtained in step 1, and then use sandpaper 6 to further grind the residual flash 2 to obtain a polished metal weld C7;

Step 3: Clean the surface of the metal weldment C7 obtained in Step 2 (using alcohol as the detergent 8) to remove metal particles generated during the grinding process;

Step 4: Lay a layer of absorption layer 10 (black polytetrafluoroethylene tape or black paint) on the surface of the welding seam 3 of the metal weldment D9 obtained in the step 3, the function is to absorb the laser energy to generate plasma and form a shock wave; A confinement layer 11 (water or optical glass) is laid on the absorption layer to increase the amplitude of the laser shock pressure and prolong the pressure action time;

Step 5: Fix the metal weldment D 9 on which the absorption layer 10 and the constraining layer 11 are laid on the six-axis robot fixture 16 of the six-axis robot 17, adjust the parameters of the laser shock according to the production needs, and use the laser 13 (using high-power Q-switched Nd:YAG laser, the laser beam energy follows a nearly flat-top distribution) and outputs a laser beam 12. The laser 12 first changes its transmission direction and focuses through the optical device 15, and then passes through the confinement layer 11 and is absorbed by the absorption layer 12 to generate plasma. The explosion forms a shock wave, which impacts the welding seam 3 of the metal weldment to obtain the metal weldment E14 after laser shock, and the physical properties of the friction stir welded joint of the metal weldment are strengthened.

Claims (6)

1. a friction stir welding joint strengthening method based on laser shock, is characterized in that, comprises the following steps: Step 1): place the two pieces of metal weldment A(1) to be welded on the friction stir welding workbench, adjust the welding parameters for welding according to production requirements, and obtain the welded metal weldment B(5); Step 2): remove the flash (2) caused by friction stir welding from the metal weldment B (5) obtained in the step 1) to obtain the polished metal weldment C (7); Step 3): cleaning the surface of the metal weldment C(7) obtained in step 2) to remove the metal particles generated during the grinding process; Step 4): laying an absorption layer (10) on the surface of the welding seam of the metal weldment D (9) obtained in the step 3), the function is to absorb the laser energy to generate plasma and form a shock wave; lay a layer of restraint above the absorption layer layer (11) to increase the amplitude of the laser shock pressure and prolong the pressure action time; Step 5): fix the metal welding part D (9) on which the absorption layer (10) and the constraining layer (11) are laid, adjust the parameters of the laser shock according to the production needs, and use the laser (13) to output the laser beam (12), The laser light (12) first changes the transmission direction and focuses through the optical device (15), and then passes through the confinement layer (11) and is absorbed by the absorption layer (12) to generate a plasma explosion to form a shock wave. The impact is performed to obtain the metal welded part E (14) after laser impact, and the physical properties of the friction stir welded joint of the metal welded part are strengthened. 2. The method for strengthening friction stir welded joints based on laser shock as claimed in claim 1, wherein in the step 1), the metal weldment A (5) is first removed by an angle grinder due to friction stir welding. Flash (2) and then further sanding of residual flash (2) with sandpaper (6). 3. The laser shock-based friction stir welding head strengthening method according to claim 1, characterized in that, in the step 3), alcohol is used as a detergent (8) to clean the surface of the welded parts. 4. The laser shock-based friction stir welding head strengthening method according to claim 1, wherein the absorption layer (10) in the step 4) is black polytetrafluoroethylene tape or black paint. 5. The laser shock-based friction stir welding joint strengthening method according to claim 1, wherein the constraining layer (11) in the step 4) is water or optical glass. 6. The method for strengthening friction stir welded joints based on laser shock as claimed in claim 1, wherein the laser (13) adopts a high-power Q-switched Nd:YAG laser in the step 5), and the laser beam energy follows a Flat-top distribution.

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