| 摘要 |
PURPOSE:To prevent the longitudinal crack of a down slope part through lowering of cooling rate by controlling beam current gently at the start of the down slope and further agitating molten pool by beam deflection. CONSTITUTION:In the stage of shifting from a section 7 of steady penetration in electron beam to a down slope, beam current Ib is controlled to a gentle slope to prevent the generation of an imperfect solidification mode in a part 8. Further, just prior to the shift to the down slope, the molten pool is agitated by rotating the electron beam in a circular shape C or oscillating (d) the same in the welding direction, whereby the segregation of a metallic compound on account of an increased rate of cooling is suppressed and the longitudinal crack of a welded part W is prevented. |
