08Ni3DR钢焊接接头最薄弱区域与冲击韧性之间的关系

低温压力容器08Ni3DR钢在极低温度下(-100℃)具有较好的强韧性匹配,在实际工程应用中,保障焊接接头的低温冲击韧性一直是压力容器制造过程中的难题之一。对于实际的焊接接头,最薄弱区域的确定以及最薄弱区域的影响对焊接接头的表征具有重要的意义。通过将夏比V型缺口开在母材、焊缝、热影响区不同位置处,系统研究了08Ni3DR压力容器钢焊接接头的组织和韧性。结果表明:焊接接头韧性最薄弱区域为粗晶热影响区,其粗晶热影响区的显微组织为粗大的粒状贝氏体和板条贝氏体组成的复合组织。粗晶热影响区宽度在缺口尖端前沿所占比例越高,试样的冲击吸收能量越低。当粗晶热影响区宽度所占比例达到100%时,冲击吸收能量为27 J,相比于母材冲击韧性损失高达90.7%。以上两个方面充分体现出焊接接头最薄弱区域对冲击韧性有很大的影响。

Relationship between the weakest zone and impact toughness of 08Ni3DR welded joint

Low temperature pressure vessel 08Ni3DR steel has a good strength and toughness at a very low temperature(-100℃).In practical engineering application,it is one of the difficult problems to ensure the low temperature impact toug-hness of welded joints in the process of pressure vessel man-ufacturing.The determination of the weakest zone and the effects of the weakest zone are very important for the charact-erization of the actual welded joints.The microstructures and toughness of the welded joints of 08Ni3DR pressure vessel steel were systematically studied by preparing the Charpy V-notch on the base metal,weld metal and different locations of heat-affected zone.The results show that the weakest toughness zone of the welded joint is the coarse grain heat-affected zone,which is a composite microstructure composed of coarse granular bainite and lath bainite.As the proportion of the width of coarse grain heat affected zone in the front of the notch tip increases,the impact absorbed energy of the specimen decreases.When the proportion of the width of the coarse grain heat-affected zone reaches 100%,the impact absorbed energy is 27 J,and the impact toughness of the coarse grain heat-affected zone reduces by 90.7%.Above two aspects fully show that the weakest zone has a great effect on the impact toughness of the welded joint.