Consolidation of sheathed pure iron powders by warm caliber rolling

Metal powders produced by mechanical milling show the specific microstructures and properties. With these merits preserved, the powders should be combined into a large size compact. Saito et al. and Kimura et al. have succeeded in consolidating the iron powders into 1 ∼ 2.5 mm thick sheets by sheath rolling at a relatively low temperature of 973K. Based upon their success, we have attempted to apply caliber rolling for consolidating the powders into a large bar (φ11 × 1000 mm). The sheath can was filled with pure iron powders, sealed in vacuum, and then rolled. When the rolling temperature was 973K, rolling reduction of more than 80% was enough to make sound compacts of >10 mm diameter with fine microstructure and relative density larger than 99.6%. When the rolling reduction was 90%, the consolidation was accomplished in a wide range of rolling temperature between 1273K and 823K. At 823K and 873K, the sound consolidation could be realized without recrystallization. The tensile propertie s were better than those of the HIP treated compact. Hence, the solid-state joining is confirmed to occur much easier in the present method than in the HIP method.