Fatigue crack propagation properties of butt welded joints in air at elevated temperature

Abstract

Summary This paper describes centre crack specimens being used to determine the fatigue crack propagation properties of SB450 steel plate at 300°C under conditions where the thermal stress is significantly smaller than the test stress ratio (29–68 MPa). The fatigue crack propagates through the weld metal or base metal in air at room temperature and 300°C. To run tests at elevated temperature, a special furnace was built to achieve the proper temperature distribution and to reduce the compressive thermal stress at the specimen centre to less than 1 MPa. The low thermal stress condition avoids any enhancement of fatigue crack closure. The data obtained in the Pmax hold test suggest that, if fatigue crack closure is prevented through testing by the Pmax hold test, results much the same as those obtained in a welding tensile residual stress field can be obtained at both room temperature and 300°C.