Third Report of the Welding Research Committee

The report contains an account of further tests to determine (1) the effect of heat treatment on the fatigue properties of welds; and (2) the differences in the fatigue properties of welds when tested (a) as received, (b) with the top layer removed so that the weld metal is flush with the surface of the plate; (c) machined all over. Repeated stress tests have been carried out on specimens cut from welds prepared simultaneously with the longitudinal joints of boiler drums. Specimens cut from welds of boiler plates 3 inches thick were also tested in two types of repeated stress machines and the results compared with those of the repeated stress tests of the 3-inch welds carried out in a large machine capable of testing thick plates. A critical analysis of the results from the two sets of tests has been attempted. The results of numerous repeated stress tests are analysed, and curves are given relating the maximum and minimum repeated stresses with the number of repetitions. A curve is also given from which, it is suggested, the reasonable safe tensile fatigue range for any given initial stress can be obtained.

The results of static creep tests and slowly repeated stress tests, carried out at 460 deg. C. and 298 deg. C., are given, and show that creep in the welds at these temperatures is not essentially different from that in the plate.

Repeated stress tests have been carried out on three different boiler drums, annealed at 600 deg. C. for 140 minutes and then cooled in the furnace. Repeated hydraulic loadings were continued until cracks developed, but in no case did these take place in the welds, showing conclusively that the welds were not the weakest part of the drums.