Strengthening of Steels by Modified Ausforming

Abstract

This paper describes strengthening and toughening of Ni-Cr and Ni-Cr-Mo structural alloy steels by modified ausforming. These steels were rolled maximum 63% in the temperature range between 880°and 750°C and quenched, and their tensile properties, the impact properties and micro-structures were compared with those of conventionally heat-treated steel after tempering from 200°to 700°C. The yield and the ultimate tensile strengths increased greatly and the maximum increase of the yield strength amounted to 0.5kg/mm² per each 1% reduction, while the elongation was not lowered. A good combination of yield strength and ductility was achieved by modified ausforming. It was also found that the process brought about a good combination of hardness and impact strength in these steels and lowered their transition temperatures. Metallographic examination revealed that the refinement of subgrains by modified ausforming was an important factor for strengthening and toughening of the steels.