METHOD OF AUSTENITIC STEELS HOT FORMING WITH RECRYSTALLIZATION ANNEALING

摘要

The invention concerns new technology for production of formed semi-finished products with the aim of achieving grain fineness with ultrasonic patency. The process includes added thermal processing or solution annealing immediately after production of the formed semi-finished product without inter-cooling in air. After completing forming the semi-finished product is continually cooled and, at a surface temperature higher than 700 degrees C, it is put into a furnace and their recrystallisation annealed at the temperature or at a temperature near to solution annealing. If the semi-finished product is then cooled in water the annealing can fulfil the requirements for solution annealing. When applying the low final forming temperature it is possible to return the forged piece to the heating furnace and carry out recrystallisation annealing in that furnace. The theoretical essence of the given solution is the knowledge that, at a temperature under 700 degrees C, there is precipitation in some austenitic steels heated to the forming phase, which significantly stabilises the dislocation substructure after forming in the final operation, thereby easing the course of recrystallisation with usual solution annealing, which supports the persistence of possible coarse-graininess of the formed semi-product through the process of final thermal processing.