X80管线钢焊缝金属中的针状铁素体

探讨了X80管线钢焊缝中针状铁素体的形成条件、对焊缝韧性的影响及针状铁素体控制机理。结果表明,X80管线钢焊缝组织是大量针状铁素体+少量先共析铁素体的混合组织。在针状铁素体影响因素中,起决定作用的是焊缝的化学成分和冷却速度。焊缝中针状铁素体形态和数量与焊缝韧性之间存在对应关系,焊接热输入对焊缝韧性的影响较复杂,存在一个热输入最佳值。优化的焊缝合金系统和化学成分是控制焊缝针状铁素体形成的必要条件,而合理的工艺方法和焊接参数(含热输入)则是控制针状铁素体形成的充分条件。

Acicular ferrite in weld metal of X80 pipeline steel

The formation conditions of acicular ferrite, the influence of acicular ferrite on weld toughness and the control mechanism of acicular ferrite of X80 pipeline steel weld are discussed. The results show that the weld microstructure of X80 steel is composed of a large number of acicular ferrite plus a little proeutectoid ferrite. In the factors affecting acicular ferrite,the chemical composition and cooling rate of the weld play a decisive role. There is a corresponding relationship between the morphology and quantity of acicular ferrite in welds and weld toughness,the effect of welding heat input on weld toughness is more complex and there is an optimal value for heat input. The optimized weld alloy system and chemical composition are necessary conditions to control the acicular ferrite formation in the weld,and the reasonable procedure methods and welding parameters (including heat input) are sufficient conditions to control acicular ferrite formation.