氧化物夹杂与Ni-Cr-Mo-V钢多层焊缝低温冲击韧性变化规律的关系

Relationship between Oxide Inclusion and Changing Rule of Low Experimental Temperature Impact Toughness of Ni-Cr-Mo-V Steel Weld Metal

测试了反应堆压力容器用Ni-Cr-Mo-V钢焊缝的冲击韧性,实验结果表明,当实验温度较低时,同一实验温度下沿盖面焊到焊根方向不同层焊缝样品的冲击吸收能呈下降趋势。通过低温实验样品断口观察到韧窝底部、起裂源、解离断刻面裂纹源存在直径为0.3~2.0μm的球形氧化物夹杂,导致试样在变形过程中氧化物夹杂与基体分离形成微裂纹,并发展为试样的韧窝、起裂源和解离断刻面裂纹源,由此推断氧化物夹杂是造成焊缝低温失效的主要原因。同时氧化物夹杂的数量沿盖面焊到焊根方向逐渐增多,使得微裂纹形核率逐渐增加,造成焊缝低温冲击韧性沿盖面焊到焊根方向逐渐变差。

The Charpy impact tests of Ni-Cr-Mo-V steel used as reactor pressure vessel material weld metal were performed,and the result of the impact experiments shows that at low experimental temperature,the impact toughness of weld metal is worse gradually at the same experimental temperature along the direction from cosmetic welding to weld root.The spherical oxide inclusions with a diameter of 0.3-2.0μm,located at the crack initiation site,dimples and cleavage facet initiation,were observed at the low temperature experimental fracture.In the process,the oxide inclusions and matrix separate to form microcracks,and develop into crack initiation site,dimples and cleavage facet initiation.It is concluded that the oxide inclusions are the main reason for low temperature failure of the weld.At the same time,the amount of oxide inclusions along the cosmetic welding to the weld root increases gradually,which causes the increase of the microcracks nucleation rate,and then the low temperature impact toughness of the weld is worse gradually along the direction from cosmetic welding to weld root.