WELDING OF ALUMINUM ALLOY 5086 BY FSW PROCEDURE
Darko Bajić, Sanja Miljani/p>
Key words: welding, FSW, friction, tool face, tool mandrel, mechanical propertiesrong>
Abstract:/strong>
In the case of conventional arc welding of aluminum and its alloys, in addition to the great skill of the welder, high-quality preparation of the joint sides, additional electrode material, gas protection of the welding zone and adequate welding parameters are necessary. Thanks to the development of the principles of the FSW process, the quality of welding aluminum and its alloys depends, first of all, on the geometry of the welding tool and the welding parameters: rotation speed, axial force and speed of translational movement of the tool.
1. INTRODUCTION
Friction welding uses a combination of thermal and mechanical energy by friction between two elements to generate heat on the contact surfaces. At least one of these two elements must perform rotational movement. The released heat on the contact surface of the two elements turns the material into a doughy state, and the action of the axial force creates a welded joint. Thanks to the extrusion of part of the material, oxides and impurities are thrown out in this ring, so the microstructure of the joint is favorable. or both elements gives results and it is possible to connect the materials provided that their longitudinal axes match. Depending on the available equipment, elements with a rectangular cross-section can also be friction welded. The required heat is generated by moving, most often, one element or simultaneously moving both working elements in the opposite direction. Friction stir welding or FSW welding (Friction Stir Welding) was patented in 1991 by TheWeldingInstituteofCambridgeU.K.(TWI). It was primarily intended for welding aluminum and was patented as such. Due to the wear of welding tools, the procedure is mostly used commercially for welding soft materials: aluminum, copper, zinc, magnesium, and recently also a number of steel materials. to all branches of industry, especially in the aviation, railway, automotive and process industries. A schematic representation of the FSW welding process is given in Figure 1.
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Figure 1. Schematic representation of friction stir welding/em>
2. INFLUENTIAL PARAMETRIFSW PROCEDURE
The quality of welded joints made by the friction stir welding process is determined by several parameters as well as the characteristics of the materials involved in the welding process. Determining parameters and characteristics of materials affect the speed and amount of heat generation, temperature field, cooling temperature, torque and power. The following parameters have the greatest influence on the quality of friction stir welding [3-8]:
- Tool rotation speed,
- Welding speed - translational speed,
- Force in the osealate direction - axial force,
- Angle of inclination of the tool,
- Relationship between rotation speed and welding speed,
- Tool geometry
The three basic parameters are: Tool rotation speed (angular speed-ω): during the FSW welding process it is constant (1001600o/min), because any change represents a risk that leads to tool damage. Translator speed: is the welding speed as well. Its choice depends primarily on the mechanical properties of the welded material and its thickness, as well as on the adopted speed of rotation of the tool. Axial force (Fa): enables the penetration of the tool into the base material (picture 2). The maximum value is reached at the moment of penetration of the mandrel through the material to be welded, and the minimum value at the end of the penetration phase, when the initial keyhole is formed. In the literature, axial force is often called welding force.
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Figure 2. Forces acting on the tool during the welding process
In order to obtain a quality welded joint using the FSW process, an optimal combination of values is requiredsti of the mentioned parameters, which for now can only be determined by experimental methods. The thermo-physical characteristics of the materials to be welded and their thickness are two basic factors that influence the value of the parameters. The process of FSW welding of two working elements takes place through two phases[1]:
- heat generation in the base material i
- welding
Additional information can be downloaded from the link below./p>
