Inheritance of the initial structure in steel 4Kh5MF1S after a finish heat treatment

Abstract

The life of dies and press molds that fail due to abrasion is determined predominantly by the structure and properties of the surface layers, which change most when operating under a cyclic effect of the temperature and pressure. For this reason, the use of methods of surface strengthening is an effective way for increasing the service life of dies and press molds. An analysis of premature failure of some batches of molds for pressure casting has shown that they were fabricated with distortions of the technological process, namely, deviations from the forging temperature regime and an insufficient degree of deformation (forging without fiber entangling, often practiced in forge shops). The structure formed in forging is preserved in the quenched and tempered state. After the finish operation of nitriding the deformation in such press molds increases (the sizes of the tool change), cleavage develops in the operation, and the strengthened layer scales off. The aim of the present study consists in establishing an interrelation between the structure attained in the first stage of fabricating the press mold (after forging) and the structure attained after the subsequent operations of annealing, quenching, tempering, and nitriding.