Ⅰ.Understanding the friction stir welding process
No other welding consumables such as welding rods, wires, fluxes and shielding gases are required in the friction stir welding process, the only consumption is the welding stir head.
The temperature during FSW friction stir welding is relatively low, so the residual stress or deformation of the structure after welding is also much smaller than in fusion welding. Particularly when fusion welding thin plates of Al alloys, the out-of-plane deformation of the structure is very pronounced, which is troublesome and increases the manufacturing cost of the structure, whether using deformation-free welding techniques or post-weld cold or hot straightening techniques.
The stir friction welding process has been used successfully in the joining of non-ferrous metals, but is limited to the welding of structurally simple elements such as flat structures or cylindrical structures due to the limitations of the welding method and the need for the workpiece to be well supported or lined during the welding process. In principle, stir friction welding can be carried out in a variety of positions, such as flat welding, vertical welding, back welding and top welding; can be completed in a variety of forms of welded joints, such as butt, fillet and lap joints, and even thickness changes in the structure and the connection of multi-layer materials, but also the welding of dissimilar metal materials.
Ⅱ.The application of stir friction welding process in the water-cooled plate
In the power electronics heat dissipation industry, water cooling plate heat dissipation is becoming popular, due to the continued pursuit of high reliability and low cost, the traditional vacuum brazing technology for certain industries and product structures have some drawbacks, water-cooled plate using the stir friction welding process, so that the waterway design is more free, better sealing reliability, while the hard anode surface treatment can be used.
Stir friction welding is the use of high speed rotating welding tool and the workpiece friction generated by the heat to make the welded material local melting. When the welding tool moves forward along the welding interface, the plasticised material flows from the front of the tool to the rear under the friction of the rotating tool and forms a dense solid-phase weld under the squeeze of the tool.
Ⅲ.Stir friction welding process characteristics.
1, No fusion welding porosity defects in the weld, no elemental burnout, no thermal cracking, thus to ensure high reliability without leakage.
2. No solidification of elements and tissue segregation. Microstructure is isotropic in the weld area, no weld residual height.
3. The welding process is simple and belongs to the no flux type welding. No need to fill the wire, no need to open the bevel, no need to pre-weld treatment, no need to protect the gas.
4. The process is environmentally friendly, no light and gas pollution.
5. Small shrinkage and deformation in the weld area.
6. Due to the popularity of equipment, stir friction welding cost will be further reduced, become a common welding technology.
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