back-chipped /underside(关于焊接)? Underside of Joint during Welding Double sided groove joints should be back-chipped or ground at the root before welding the second side. Where GTAW is used for the root pass, purge gas shall be used on the underside of the weld and shall be maintained until at least two layers have been completed or until oxidation is not significant. 求标红句中文。 查看更多10个回答 . 4人已关注