Influence of free forging conditions on austenitic grain growth in constructional steel

1. The initial period of austenitic grain growth in heating of a hot forged billet of 50G-SSh steel and of forgings after free forging is characterized by the formation of a mixed grain structure of No. 8 fine grains and No. 3-0 coarse. 2. Reforging of the billets of 50G-SSh steel with e=90% reduced the temperature of the start of austenitic grain growth from 1000 to 950°C. 3. The formation of a mixed grain structure in the initial period of growth is characterized by nonuniform distribution of the coarse grains in the cross section of the forging. At low temperatures of heating for forging (900°C) the giant grains are uniformly distributed in the volume of the steel, while with an increase in the temperature of heating for forging the coarse grains are concentrated in the center of the forging in the regions of the “forging cross”. 4. The higher the temperature of heating for forging and the temperature of the finish of forging, the coarse the giant grains formed in the initial period of grain growth.