Sandwich rolling of sintered compacts of pure chromium

Sandwich rolling, in which the workpiece is sandwiched between two mild steel sheets, is tried to enhance the rolling workability for sintered compacts of pure chromium. In conventional rolling, many thin cracks occur on the surfaces of workpiece rolled at higher temperatures than 1373 K. These cracks are supposed to occur by the rapid cooling of the workpiece surfaces in contact with the cold work rolls. Sandwich rolling is very effective in preventing the occurrence of surface cracks, since the mild steel sheets on both sides of the rolling workpiece interrupt the temperature decrease of the surfaces. This method is also very superior in workability to conventional rolling. The behavior of ductile-to-brittle transition and recrystallization were also examined in the rolled specimens. The ductile-to-brittle transition temperature is lowered in a specimen taken from a workpiece subjected to a large rolling reduction. The Vickers hardness of a specimen rolled at 973 K is considerably greater than that rolled at 773 K. The recrystallization temperature of the sintered compacts is almost the same to that of cast material.