Yoshiro Yamaguchi

Analysis of temperature and membrane stresses on welding and cooling in the process of producing 304 stainless-steel pipes

Abstract In order to clarify the effects of the production processes on the residual stress in a welded 304 stainless-steel pipe, the welding and cooling processes are focused on and discussed. (1) The temperature distribution on welding and cooling is analyzed by the finite-difference method and compared with the data measured by infrared thermography and thermocouples. The numerical solution is in good agreement with that from the measured temperature, which shows the effectiveness of using calculated temperature data for analyzing a thermal stress. (2) It is found that for constant wall thickness, when the welding speed is increased, the molten pool becomes larger and the reduction in temperature is smaller. (3) The change in the thermal stress in welding and cooling processes is calculated by use of membrane theory. A region of compressive stress that appears in the adjacent part to the welded bead at welding, moves towards the bottom of the pipe as time passes. After a long time the stress state is compressive in the bottom part and tensile in the welded and adjacent parts. (4) The longitudinal residual stress is tensile at the weld bead and at the bottom and compressive at the side.