高Ti-Nb系高强钢焊接接头回火前后的力学行为

采用混合气体保护焊,研究了高Ti-Nb成分体系控轧控冷高强钢焊接接头在回火前后的力学性能变化,阐述了焊态接头的软化机理,分析了这些变化与微观组织的联系. 结果表明,随焊接热输入的增加,细小的(Ti,Nb)(C,N)析出相粒子回溶基体,CGHAZ软化程度加剧;回火后接头软化程度缓解,母材强度提高,但随着回火温度的提高,接头及母材的冲击韧性均呈降低趋势,其原因与原始组织遗传及正交Fe₃C型碳化物沿晶界析出有关.

Mechanical behavior of welded joint of a high Ti-Nb content microalloyed high-strength steel before and after drawing temper treatment

In this paper, the MAG welding using 80%Ar+20％CO₂ was applied on a Ti-Nb type microalloy TMCP high-strength steel. The mechanical properties of the welded joint before and after drawing temper treatment were particularly investigated, which aimed at clarifying the softening mechanism of welded joint systematically and comprehensively analyzing the correlation between the variation of mechanical properties and microstructure. The results showed that with increasing of heat input, the precipitated particles of (Ti.Nb)(C,N) were dissolved during the welding thermal cycle, which improved the softening tendency of CGHAZ. The post drawing temper treatment mitigated the softening behaviors of welded joints and the strength of the base metal were improved. Moreover, with the increase of tempering temperature, the impact toughness of welded joint and base metal were decreased, due to the inheritance of original microstructure and the precipitation of Fe₃C-typed carbide along grain boundaries.