Abstract: Effects of deformation amount, deformation rate, cooling method and solution treatment temperature on the grain size of 316H austenitic stainless steel were systematically studied, and the engineering trial production of the extruded large-diameter 316H austenitic stainless steel was carried out. The results show that the larger the deformation, the finer the grains. When the extrusion deformation is 80%, the grain size reaches finer than grade 4. Under the same deformation rate, the grain size of the specimens is obviously related to the cooling method, where the grain size increases in turn for the specimens with water-cooling, air-cooling and holding for 3 min then air-cooling. Under the same cooling rate, the higher the deformation rate, the finer the grain size, but with the decrease of cooling rate, the difference in grain size decreases gradually. The effect of solution treatment temperature on the increase of grain size is much greater than that of the solution time. The solution treatment is effective to homogenize the grain size after extrusion, but the grain size grows rapidly if the solution treatment temperature is too high. The solution treatment temperature and time should be controlled within 1050 ℃ and 40 min.

Key words: 316H stainless steel, grain size, extrusion temperature, deformation, solution treatment temperature