The Effect of Hot Deformation Parameters on Grain Size Refinement in A Martensitic Stainless Steel

The grain size refinement of aisi 422 martensitic stainless steel in the temperature range of 950-1150 ºc was investigated by hot deformation tests. the deformed specimens were held at deformation temperature with delay times of 5 to 300s after achieving a strain of 0.3. the austenite grains exhibit a considerable growth at temperature higher than 1050˚c, while the grain coarsening is negligible at lower deformation temperatures. therefore, it is a difficult task to achieve a fine grain structure at these high deformation temperatures. in the second stage of this work, the grain growth behavior of the deformed alloy at temperature range of 940-1020 ºc was investigated to obtain a fine austenite grain in the final deformation step. a uniform and fine-grain structure, with average grain size less than 30 μm, can be obtained by considering the appropriate temperature and strain per pass. at 1020˚c, a relatively fine and uniform recrystallized grain, mean grain size of about 28 μm, is obtained with an applied strain of 0.4, while at 980˚c after strain of 0.2 a nearly equiaxed grain with the same mean grain size is achieved.