Fatigue Crack Growth in Low Alloy Steel Submerged Arc Weld Metals

Abstract

Fatigue crack growth experiments were conducted on low alloy steel submerged arc weld metals representative of those used in the fabrication of pressure vessels. Variations of wire composition, flux type, and postweld heat treatments were used to produce weld deposits of different microstructures and tensile and toughness properties. Fatigue crack growth experiments were conducted on 25.4-mm (1-in.) thick modified wedge opening loaded (WOL) specimens at room temperature and 288 °C (550°F). A compliance calibration curve was developed at room temperature and adjusted for use with elevated temperature compliance measurements. Results of these experiments indicate: (a) a slight effect of flux type on crack growth rates, (b) incomplete tempering or relief of residual welding stress, or both, has an appreciable effect on crack growth behavior, (c) comparable or lower crack growth rates at 288°C (550°F) compared to room temperature, (d) comparable or lower crack growth rates than those predicted in Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, and (e) variations in crack growth rates due to wire, flux, and postweld heat treatment were less pronounced than the variations in toughness and tensile properties.