The effect of microstructures on strength, strain capacity and low temperature toughness of a micro-alloyed pipeline steel was elucidated. Five various dual-phase microstructures, namely, acicular ferrite and a small amount of (around 2 vol.%) polygonal ferrite (AF + PF), polygonal ferrite and bainite (PF + B), polygonal ferrite and martensite/austenite islands (PF + M/A), polygonal ferrite and martensite (PF + M) and elongated polygonal ferrite and martensite (ePF + M), have been studied. Experimental results show that AF + PF microstructure has high yield strength and excellent low temperature toughness, whereas its yield ratio is the highest. Polygonal ferrite-based dual-phase steels, PF + B, PF + M/A and PF + M microstructures show better strain capacity and low temperature toughness. The strain capacity and low temperature toughness of ePF + M microstructure are the worst due to its high strength. The relationship between microstructure, strength, strain capacity and toughness has been established. Based on the results, the optimum microstructure for a better combination of strength, strain capacity and toughness is suggested to be the one having appropriate polygonal ferrite as second phase in an acicular ferrite matrix.

阐明了显微组织对微合金管线钢的强度，应变能力和低温韧性的影响。五种不同的双相微结构，即针状铁素体和少量（约占体积的2％）的多边形铁素体（AF + PF），多边形铁素体和贝氏体（PF + B），多边形铁素体和马氏体/奥氏体岛（PF + M / A），多边形铁素体和马氏体（PF + M）和细长多边形铁素体和马氏体（ePF + M）进行了研究。实验结果表明，AF + PF显微组织具有较高的屈服强度和优异的低温韧性，而屈服比最高。多边形铁素体基双相钢PF + B，PF + M / A和PF + M的显微组织具有更好的应变能力和低温韧性。ePF + M微结构的应变能力和低温韧性由于强度高而最差。建立了显微组织，强度，应变能力和韧性之间的关系。基于这些结果，建议将强度，应变能力和韧性更好地结合的最佳微观组织是在针状铁素体基体中具有合适的多边形铁素体作为第二相的组织。