FRICTION STIR WELDING METHOD FOR STEEL SHEETS AND METHOD OF MANUFACTURING JOINT

摘要

Provided is a friction stir welding method for steel sheets comprising: inserting a rotating tool into an unwelded portion where two or more steel sheets are overlapped or butted together; moving the rotating tool along portions to be welded while rotating the tool, so that a softened portion is formed in the steel sheets by friction heat generated between the rotating tool and the steel sheets, and the steel sheets are welded together by utilizing a plastic flow generated by the softened portion being stirred; and preheating the unwelded portion before welding by the rotating tool, wherein the preheating of the unwelded portion is performed by a pair of heating devices disposed over and under the unwelded portion and ahead of the rotating tool in the advancing direction to enable high speed welding without the risk of generation of welding defects and damages to the welding tool.