【摘要】 本文通过实验和分析说明：碳钢多层焊焊缝。低温冲击出现低值的直接原因是存在于焊缝中的微观氧化物夹杂。成份主要为硅、钙、铝和铁的氧化物的复盐，其形态为多边形的微观夹杂，形成冲击试样的裂源、尺寸较大的此类氧化物夹杂，可作为解理核心，引起试样脆性断裂，并诱发低值．更多还原

【Abstract】 According to the test research and theoretical approach this paper advances: for multilayer weld of carbon steel the itrunediate cause which presents low impact value in. cold-state temperature is the existence of microimpurities of oxides. The microimpurity, consisting oxides of silicon, calcium, aluminium and ferrite and having multiangular appearance,forms the source of cracks for impact sample. The ndcroimpurity of this type with the larger size becomes the nucleus of cracks on cleavage face,which presents low impact value because of the cleavage fracture in coldstate temperature.更多还原