X80管线钢气体保护焊用焊丝的研制

Development of gas metal arc welding wire for X80 pipeline steel

对所研制的焊丝进行了气体保护焊试验,测试了焊缝金属的化学成分、金相组织、冲击韧度、强度、硬度和接头的抗拉强度。金相组织主要为针状铁素体、少量的先共析铁素体和粒状贝氏体,用扫描电镜分析了冲击断口的形貌和夹杂物的组成,用透射电镜分析了焊缝金属的微观结构。结果表明,在焊丝中加入微量的Ti-B,可以有效地抑制先共析铁素体的形成,使焊缝获得细小、均匀的针状铁素体组织。焊缝中合金元素形成了弥散分布的细小夹杂物,成为了针状铁素体(AF)的形核质点。针状铁素体内有许多位错团,可以有效地阻止裂纹的扩展,提高冲击韧度。

The developed wires are used for gas metal arc welding. The chemical composition,microstructure,impact toughness,strength,hardness and tensile strength of welded joint are investigated. The microstructure is composed of acicular ferrite and a little proeutectoid ferrite and a little granular bainite. The fractured surfaces of impact specimen are analyzed by scanning electron microscope, and the microstructures of weld metal are analyzed by transmission electron microscope. Experiment results indicated that it was effective to resist proeutectoid ferrite and make fine homogeneous acicular formation by adding microcontent Ti-B elements in the wire. It had been found that alloy element in weld metal could be the nucleating-centers of acicular ferrite as long as they formed fine disperse inclusion. It is effective to prevent crack propagation and improve impact toughness because there are lots of dislocation agglomerating in acicular ferrite.