P91钢主蒸汽管道焊缝金相缺陷形态及其形成原因探讨

Reasons for Metallography Defect Form and the Formation of P91 Steel Main Steam Pipe Welding Seam

通过对表面有微裂纹的P91钢主蒸汽管道焊缝取样试验分析,认为焊缝金相缺陷主要有3种形态:表面微裂纹、线状缺陷(晶间网状或线状析出物偏聚)及粗大的柱状晶。以钢的焊接熔池凝固、相变及多层多道焊层之间热影响区相变理论为基础,对金相缺陷形成机理进行探讨,金相缺陷的直接危害是焊缝冲击韧性极低(小于10 J)。焊接线能量过大是产生焊缝金相缺陷的主要原因。

It is believed that three forms of metallogrphy defect for wielding seams exist by sample test analyzing on surface microcracks for P91 stell main steam pipe welding seam, which are surface micro-cracks, lineal defect （intergranular reticulation or lineal defect preeipitates segregation） and bold columnar grains. Discussions are made on forming mechanism of metallogrphy defect based on the welding pool solidification, phase change and heat affected zone phase change theory between multi-layer and multi-pass wielding. The immediate danger of metallogrphy defect is the impact toughness reduces greatly （lower than 10J）. The main causes for welding seam metallogrphy defect is due to big wielding wire energy.