EFFECT OF TOOL ROTATION ON THE JOINT STRENGTH OF COLD-WORK DIE STEEL BY FRICTION STIR WELDING

摘要

The present study investigates, the effect of tool rotation on the microstructure and mechanical properties resulting from friction stir welding (FSW) of cold-work die steel. A FSW tool, made of a WC-baseed material, was used to butt weld 10-mm-thick plates at a constant welding speed of 1.0 mm/min and incremental tool rotational speeds ranging from 250 up to 1350 rpm. Metallographic observation revealed that sound welds were successfully obtained for tool rotational speeds in the range 720-935 rpm, whereas, outside this range, defects were formed. Additionally, FSW decreased the grain size in the Stir Zone (SZ) and Heat Affected Zone (HAZ) leading to a consequential increase in hardness and tensile strength in the SZ. These results were attributed to the interplay between tool rotational speed and the welding heat input.