METHOD AND APPARATUS FOR CREEP FORMING OF AND RELIEVING STRESS IN AN ELONGATED METAL BAR

摘要

A hot creep stretch wrap forming method includes heating a metal bar to a forming temperature within a temperature range suitable for creep deformation thereof, applying a stretching force to the metal bar at a strain rate no greater than 0.05 inch/inch/second, and wrapping the metal bar around a die, preferably having a thermally and/or electrically insulative work surface. The stretching force is typically applied to a strain ranging from 0.5% to 15.0%. The metal bar most preferably is a titanium alloy with a forming temperature ranging from 0.45 to 0.60 of its melting temperature. The wrapped metal bar is held in position and its temperature maintained within the temperature range typically for 5 to 120 minutes for stress relief. Preferably, the metal bar is held substantially at the forming temperature throughout the process. Thermal insulation around the die and metal bar reduce heat loss from the metal bar.