Fatigue-Crack Propagation in Electroslag Weldments

Abstract

The paper discusses the results of an investigation of fatigue-crack propagation behavior of as-deposited electroslag weldments in two hot-rolled structural steels, ASTM A36 and ASTM A588 Grade A. Fatigue-crack growth tests were conducted on 1T wedge-opening-loading (WOL) specimens machined from six 1-in.-thick and four 4-in.-thick weldments that were representative of electroslag welds for bridges. The testing was done in air at room temperature under tension-to-tension sinusoidal loading. Various orientations and locations of the fatigue crack in relation to the weld geometry were investigated. The fatigue-crack growth rates (da/dN) in the weldments were similar to, or up to five times slower than, the rate in the base steels. The retardation in crack-growth rate was most pronounced at low values of the stress-intensity factor range (ΔK) and was substantially greater for crack propagation in the coarse-grained heat-affected zone (HAZ) and bond-line regions than in the weld metal. Marked variations in the microstructure of the weld metal and HAZ had no signficant influence on crack-propagation behavior, which appeared to be influenced primarily by the residual stresses in the weldments as discussed in a separate paper. The results of this study show that the upper bound of the crack-growth behavior for low-strength structural steels may be used as a conservative estimate of the crack-propagation behavior of as-deposited electroslag weldments in such steels. On this basis, the prediction of the service life of electroslag-welded structures subjected to cyclic loads, and the determination of safe inspection intervals, may be made by the same approach as that presently used for standard structural-steel weldments made by other processes.