Abstract
In the previous paper, we reported the low alloyed dual-phase steel could be used for elevated temperature case hardening steels without the first step quenching from microstructure observations. In the present work, mechanical properties and optimum quenching temperature of the dual-phase steels were investigated for practical case hardening applications.
The microstructural and mechanical properties of the 0.05 mass% C-2.0 mass % Si-(0.05 mass% Nb and 0.05 mass% Ti) steels carburized at 1323K for 10.8ks, quenched from 1123K-1223K and then tempered at 423K were studied. The maximum tensile and fatigue strength of the 2.0 mass% Si steel and the 2.0 mass% Si-(0.05 mass% Nb and 0.05 mass% Ti) steel were obtained after quenching from 1123K and 1223K, respectively. These properties were much higher than those of the conventional case hardening steel obtained by two step quenching. The wear resistance was not affected by quenching temperature and was much superior in the regions of higher and lower sliding speed compared with the carbon tool steel (SK 3). Skipping the first step quenching and carburizing at elevated temperatures make the processing time shorter and energy consumption to fab-ricate materials smaller. Thus, the dual-phase steel is considered to have a potential for practical use for the elevated temperature case hardening steel.
