Features of the Effect of Microstructure Characteristics on Corrosion Resistance of Cold-Rolled High-Strength Low-Alloy Steels (HSLA) Grade 260-300 for Automobile Building

An experimental study is conducted on the effect of production parameters on the corrosion resistance of cold-rolled high-strength low-alloy steels (HSLA) grade 260-300, treated in continuous annealing lines (CAL). It is been shown that corrosion resistance is mainly determined by development of ageing in overageing sections and during subsequent cooling. A reduction in strip movement and an increase of overageing temperature leads to more complete development of this process. A tendency towards ageing is also affected by hot rolling parameters, i.e., the end of rolling temperature in the roughing group of stands T6, correlating with an increase reheating temperature, and finishing rolling temperature T-er . The favorable effect of the T6 increase is probably connected with more complete dissolution of manganese sulfide during heating and formation of a larger number of submicron precipitates of manganese sulfide during rolling, which are a substrate for precipitation of aluminum nitride and cementite on their surface. With a reduction in finishing rolling temperature T-er , the end of aluminum nitride precipitation is more complete. These factors cause a reduction in nitrogen and carbon concentration ferrite and, consequently the tendency towards aging.