MEASUREMENT AND SIMULATION OF RESIDUAL-STRESS IN TYPE-304 WELD OVERLAY STAINLESS-STEEL PIPE

Repair by welding overlay is a commonly used method mainly employed to rebuild piping systems suffering from intergranular stress corrosion cracking (IGSCC). It is desirable that the overlay welding technique, by attaching an overlay weld to the pipe and sustaining a heat sink of flowing water inside the pipe, induces a compressive residual stress at the inner surface of the welded pipe for prevention of IGSCC. A bet ter understanding of the effect of a welding overlay repair on the res idual stresses at the inner and outer surfaces of weld overlay is thus required. To obtain this understanding, it is necessary to investigat e the distribution of residual stresses on the welded pipe. In this st udy, the hole-drilling strain-gauge method was adopted to determine th e residual stresses at the inner and outer surfaces of the weld overla y pipe. The incremental drilling technique was used on pipes with outs ide diameters of 267 mm. In addition, the Weld 3 code was applied to s imulate the residual stress distribution for comparison and verificati on with the measured results. The results obtained from the experiment al and from the computational methods are in good agreement. The resid ual stress at the inner surface of the pipe is compressive with a magn itude approaching the yield stress of the material; that at the outer surface is tensile, also with a magnitude close to yield stress but sm aller than the compressive stress. The experimental residual stress ma gnitude is generally greater than that from computation. This observat ion can be attributed to several factors including applied mechanics, temperature distribution, original residual stress, strain gauge locat ion, mechanical grinding and the oxidation layer.