抄録
The formability of sintered powder chromium plates of 99.8%-purity in roll-compression bending is investigated at various temperatures below the DBTT (Ductile-to-Brittle Transision Tempearture: 180°C for the chromium). In the roll-compression bending method for less-ductile chromium, roll-contact pressure is expected to prevent surface cracking, because high hydrostatic pressure increases ductility. However, on the first trial for monolithic chromium plates, a problem of this method was found from both the experiments and the FEM stress analysis that high tensile stress appears near the roll-contact region of the plate. To reduce the tensile stress there, steel-covered chromium plates were tested and were successfully bent at 80°C, whereas three-point bending was applicable only at the temperature above 130°C. It is thus confirmed that the roll-compression bending of steel-covered chromium plates is quite effective in decreasing the forming temperature.
