Sandwich-rolling of sintered chromium

A sandwich-rolling, in which the workpiece sandwiched between two mild steel sheets is rolled, is tried to enhance the rolling workability for sintered compacts of pure chromium. In a 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. The sandwich-rolling is very effective to prevent the occurrence of surface cracks since the mild steel sheets on both sides of the rolling workpiece interrupts the temperature decrease of the surfaces. The ductile-to-brittle transition temperature (DBTT) of sintered chromium was strongly lowered by a combination of large rolling reduction and high temperature annealing.