Abstract: It is theoretically analyzed the invalidity of the simple model for evaluating the hardened depth obtained through laser quench, in which the isothermal line of critical temperature for perlite changing into autensite is taken as the hardened depth. However at the critical temperature isothermal line, C atoms can’t diffuse adequately and then material there can’t be effectively hardened accordingly. Based on the said theoretical analysis, a new model(Dt model) is proposed. In the new model, Fourier thermal conductivity theory and time space Dt, ensuring the adequate diffusion of C atoms, are used to evaluate the dimensions of the hardened zones. The new model has been used to evaluate the hardened depth of laser-quenched HT250, and the theoretical results are verified by the experiments and are more accurate than that of the old model.

Key words: Hardened zone, Laser quenching, Martensite, Numerical analysis