• Pfeiffer, Christian
• Weinberger, Thomas
• Enzinger, Norbert
• Mitsche, Stefan
• Schröttner, Hartmuth

Abstract

Especially for aluminium and its alloys friction stir welding (FSW) has become an established welding process. In contrast FSW for steel is still challenging and in basic research. Some reasons are the high price of the tungsten based tools, the durability of the tools and the low welding speeds. For further development of the process, it is necessary to understand the metallurgical changes in the stirred material during welding. In this work, a 4mm thick stainless steel plate (1.4301) was welded with different types of tungsten-alloyed tools. A so called stop-action-technique was used at the end of the weld and the sheet was quenched immediately to prevent metallurgical changes caused by slow cooling. During the process, the temperatures on the top of the welded plate, close to the tool shoulder (10 mm beside the weld centre line) and at the bottom of the plate, directly below the weld centre were measured. On the bottom side, the temperature was also measured 35mm in front of the end of the weld to compare the differences in the cooling rate. The measured peak temperatures ranged from 330°C on top to about 1200°C on the bottom of the specimen. Moreover rotational speed was varied up to 1200 RPM to test the possibility to reduce the process forces and spindle torque. In addition the influences of the welding process parameters on the microstructural changes were investigated. E.g. the average grain size was measured which ranged from 6 to 12 µm in the stirzone.

Topics

• impedance spectroscopy
• grain
• stainless steel
• grain size
• aluminium
• durability
• tungsten