短语词组短语seam diffusion welding 扩散缝焊seam -welding head 滚焊头;缝焊焊头longitudinal seam automatic welding 纵缝自动焊seam explosive welding 线状爆炸焊接parallel seam resistance welding equipment 并列缝合电阻缝焊装置 返回 seam welding