Simultaneously Improving Mechanical Properties and Stress Corrosion Cracking Resistance of High-Strength Low-Alloy Steel via Finish Rolling within Non-recrystallization Temperature

The effect of hot rolling process on microstructure evolution, mechanical properties and stress corrosion cracking (SCC) resistance of high-strength low-alloy (HSLA) steels was investigated by varying the finish rolling temperature (FRT) and total rolling reduction. The results revealed granular bainite with large equiaxed grains was obtained by a total rolling reduction of 60% with the FRT of 950 °C (within recrystallization temperature T_r). The larger grain size and much less grain boundaries should account for the relatively lower strength and SCC resistance. A larger rolling reduction of 80% under the same FRT resulted in the formation of massive martensite–austenite (M/A) constituents and resultant low ductility and SCC resistance. In contrast, a good combination of strength, ductility and SCC resistance was obtained via 80% rolling reduction with the FRT of 860 °C (within non-recrystallization temperature T_nr), probably because of the fine grain size and M/A constituents, as well as a high density of grain boundary network.