The High Nb Content Microalloying Approach for Developing High Performance Structural Steel

Abstract

Two kinds of ULCB steel were designed with different Nb content. The yield strength of the steel which was made by adding 0.09%Nb, TMCP (Thermo Mechanical Controlling Processing) and tempering can achieve more than 900MPa. As compared with 0.05%Nb steel, adding 0.09%Nb can refine the austenite grain significantly. Through the analysis by TEM and EDX, a large amount of Nb precipitation particles can be observed in the steel with 0.09% Nb tempered at 650°C for 1h and these particles are generally small than 20nm.