Study on One-Step Hot-Dip Aluminizing at Intercritical Temperature of Multiphase Microstructure Steel

The third generation of advanced high-strength steels has received extensive attention and research due to their excellent mechanical properties. Intercritical annealing, as the most important process for commercial steels, improves mechanical properties by adjusting the phase fraction. However, the multiphase characteristics of intercritical microstructures seriously reduce the corrosion resistance of advanced high-strength steels. The one-step hot-dip aluminizing method was proposed and applied to the intercritical annealing of a multiphase medium manganese steel for energy-saving and corrosion resistance improvement. Specifically, the hot-rolled sheet is directly dipped in molten aluminum at an intercritical temperature of 725 degrees C after surface treatment. Here, the coating structure, mechanical properties and polarization curves of steel are systematically investigated. After dipping aluminizing, the present steel obtained significantly improved corrosion resistance with the corrosion current density reduced from 26.4 to 4.5 mu A center dot cm(-2). Meanwhile, the test steel still maintains good mechanical properties with the tensile strength of 1217 MPa, yield strength of 958 MPa and total elongation of 13.1%.