Tempering Brittleness of Die 4Kh4N5M4F2 Steel

Heat-treated 4Kh4N5M4F2 steel with adjustable austenitic transformation during operation was studied. The temperature range (450–500°C) in which the tempering brittleness of this steel was manifested was established. The impact toughness of the samples after different tempering temperatures and after steel hardening from 1100°C was determined and it was shown that after tempering at 475°C the minimum value of the impact toughness at room temperature (15 J cm² ) was reached. The role of Ni as a Fe_1–xNi_x replacement element was analyzed, and the segregation along the grain boundaries of the Me₆C carbide phase in the solid solution, which caused a decrease in the impact toughness and an increase in the steel brittleness, was recorded.