Effect of Mg addition on temper embrittlement in 2.25Cr–1Mo steel doped with 0.056% P–Mg segregation behavior at grain boundary

To verify the microalloying function and segregation behavior of trace Mg at grain boundary in steel, the 2.25Cr–1Mo steel doped with 0.056% P containing different Mg contents was refined with a vacuum-induction furnace. The effects of trace Mg addition on the temper embrittlement susceptibility of 2.25Cr–1Mo steel were studied by step-cooling test and the segregation behavior of Mg at grain boundary was explored by Auger electron spectroscopy. It is shown that P-induced temper embrittlement susceptibility can be reduced after subjecting to step-cooling treatment with trace Mg addition, mainly benefited from the segregation of Mg at grain boundary. This segregation can decrease the segregation amounts of P and S, especially for P, and increase the grain boundary cohesion, reducing the adverse effect on temper embrittlement caused by P and S.