Interaction Study of Carbide Precipitation and Impurity Segregation under Temper Embrittlement Conditions in a Coarse-Grained Heat-Affected Zone in Q690 Steel

Abstract

This work studied the interaction between carbide precipitation and impurity segregation under temper embrittlement (TE) conditions in a coarse-grained heat-affected zone (CGHAZ) in Q690 steel, a low-alloy high-strength structural steel used in the hydraulic support in the fully-mechanized mining face. From the perspective of carbide precipitation, through thermodynamics calculation and analysis, it was found that the existence of cementite at the grain boundaries was preceded by impurities segregation (primarily phosphorus). The precedent phosphorus segregation thus enhances the nucleation rate of cementite at the grain boundaries by lowering the ferrite/cementite interfacial energy. Both carbide precipitation and impurity segregation at the grain boundaries reached a maximum as a result of their mutual role in the temperature range of TE.