Roll compression bending of chromium plate
Yoshida Fusahito; Okada Tatsuo; Sato Toshiaki; Harada Yasunori; Ohmori Masanobu
Abstract: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 Transition Temperature: 180 deg. 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 deg., whereas three-point bending was applicable only at the temperature above 130 deg.. It is thus confirmed that the roll-compression bending of steel-covered chromium plates is quite effective in decreasing the forming temperature. Key Words:chromium, roll-compression bending, workability, ductile-to-brittle transition, DBTT, hydrostatic pressure