Abstract: The Mn-containing secondary hardening ultra-high strength steel was prepared by vacuum induction melting. Hot compression experiments were conducted at temperatures of 1 000, 1 050, and 1 100 ℃ with strain rates of 0.01, 0.05, and 0.1 s^-¹, respectively. A strain-compensated constitutive equation was established based on true stress-true strain data using the strain compensation method. The prior austenite was reconstructed to investigate the effect of hot deformation parameters on quenched microstructures. The results indicate that the flow stress decreases with increasing deformation temperature, while increases with rising strain rate. The as-established strain-compensated Arrhenius constitutive model can effectively predict flow stress, with a correlation coefficient of 0.999 8 and an average relative error of 1.868 6%. The quenched martensite combinations under different deformation conditions exhibit better consistency with CPP combination characteristics. As the deformation temperature increases and strain rate decreases, the proportion of high-angle grain boundaries increases, and the average grain size of prior austenite enlarges.

Key words: secondary hardening steel, hot deformation behavior, constitutive equation, matensite variant, vacuum induction melting