Abstract
A large number of steel plates is currently produced by HCR (Hot Charge Rolling) process. In this study, the effect of HCR condition on the mechanical properties of Nb bearing steel is investigated.
If the charging temperature is above Ar1, the toughness of Nb bearing steel through HCR process is inferior to conventionally rolled one. This phenomenon comes from the larger amount of Nb in solid solution in the HCR process than in the CCR (Cold Charged Rolling) process. This Nb in solid solution markedly retards the recrystallization of austenite and then it precipitates finely as Nb(CN) after rolling in the HCR process. To improve the balance between the tensile strength and ductile-brittle transition temperature in Nb bearing steel at a charging temperature above Ar1, 1100°C is the most favorable for the rolling start temperature, because the finest austenite grain is obtained at this temperature range due to the homogeneous recrystallization.
