The versatility of TWI's PowerStir friction stir welding (FSW) machine has satisfied the requirements of one of TWI's Member's for the fabrication of a large aluminium plate.
APCO Technologies SA is based in Switzerland. It designs and manufactures high quality structures, mechanical and electromechanical equipment to meet the specific requirements of its customers. The customer in this case was Alcatel Alenia Space (AAS) - a major company in the aerospace industry, manufacturing civil and military aircraft and providing support services to the industry. Their specific requirement was for a large autoclave table for curing composite satellite components.
The dimensions of this autoclave table were such that plate for the table surface wasn't available off the shelf in the required size. Therefore, it was necessary to fabricate the piece from multiple plates, using a welding technique that was able to minimise the amount of distortion within the plate, and produce a weld that could be guaranteed defect free. TWI's ability to produce one-off complex structures to exacting technical specifications, and leading edge FSW technology and know-how ensured that APCO could be sure that they would receive exactly what they needed.
A number of test welds were made in order to establish optimal welding parameters, which were then transferred to the production of the final plate. Metallographic sections were taken from the test welds to determine that they were free from defects (See Figure 1).
The final table surface plate was to measure 6.1m by 4.3m with a thickness of 20mm, and made from the aluminium-magnesium alloy AA5083. This plate was fabricated from four plates, two measuring 4000 x 2200 x 25mm and two measuring 2300 x 2200 x 25mm. These were welded on both sides to minimise distortion. Figure 2 shows the plates being welded. Post-weld stress relieving heat treatment and plate machining was subcontracted out by TWI. Following machining, the welds could not be distinguished from the rest of the plate, and the plate flatness and surface finish were within the tolerances specified by APCO.
The plate was transported to APCO in Switzerland (Fig. 3) on a custom built wooden frame, where it was incorporated onto their autoclave table.
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