Abstract: Low and inconsistent impact energy of the weld seam is regarded as a major technological problem relating to manufacturing of ERW linepipe. Addressing the problem of inconsistent impact energy of the hi-grade L450MB ERW pipe, the Steel Tube Plant, Baogang Co., Baoshan Iron & Steel Co., Ltd. has produced by trial the L450MB ERW linepipe which is up to the impact toughness of weld seam as specified in applicable standard by adopting a technical solution involving such actions as reducing the welding speed and adjusting the heat treatment process.