短語詞組短語back step welding 反手焊接;退焊接;逐步退焊法;退焊back ward welding 反手焊接;后退焊back running welding 封底焊back hand welding 反手焊接;后退焊;反向焊接;反向熔焊back run welding 封底焊;封四焊back step welding procedure 逐步退焊法Back sealing welding 封底焊;焊接back -welding shape 背面成形cast iron back -welding 鑄鐵補焊 返回 back weld