| 摘要 |
PURPOSE:To maintain the ductility of a weld bead part by supplying a welding filler with a carbon content below a presribed value with iron as a main component to joining parts and melting it together with mild steel plates and controlling surely a remarkable rise of hardness of a weld bead part at the time of welding beams of the abovementioned mild steel plates. CONSTITUTION:A heat source with high energy density such as a laser beam 3 or an electron beam, etc., is projected on the joining parts 1a of the mild steel plates 1 to perform the beam welding under the following conditions. In other words, in this beam welding, the welding filler with the carbon content below wt. 0.01% with iron as the main component is supplied to the joining parts 1a of the mild steel plates 1 and molten and welded together with the mild steel plates 1. As this result, the remarkable rise of the hardness of the weld bead part 4 can be surely controlled without causing a lowering of the welding speed and an increase of the thermal distortion due to the heat treatment. Consequentl, the ductility of the weld bead part 4 can be maintained without spoiling its formability. |
