High-strength of modified Ausform 9CrODS steels

Hot-rolling at the austenitic γ phase (1000 °C) led to a formation of ultra-fine grains and a high dislocation density within grain interiors by an Ausform process. Those heavily accumulated strains accelerated coarsening of prior austenite grains, and block grains transformed from the coarsened prior austenite grains were also coarser in the subsequent normalizing heat treatment. This process is called as modified Ausform process. The modified Ausform 9CrODS steels were improved in the ultimate tensile strength at 700 °C due to the formation of uniformly coarser block grains.