Henry Granjon Prize Competition 2007 Winner, Category B “Materials Behaviour and Weldability” Development of a Compressive Residual Stress Field Around a Weld Toe by Means of Phase Transformations

Abstract

Mechanically- or thermally-induced compressive stress fields have been used for decades to increase the fatigue performance of welded joints. By means of partial stabilization of austenite in the weld metal and subsequent controlled decomposition into martensite, a compressive residual stress field can be induced at the weld toe without the need of post weld processing. By proper adjustment of manganese and chromium content, a weld metal that produces a martensitic microstructure has been developed. This alloy begins its austenite-to-martensite transformation at a temperature below that at which the thermal contraction effects can negate the phase-induced volumetric expansion. The transformation also ends above room temperature to ensure the maximum volumetric expansion. Silicon additions to the manganese-chromium alloy produced welds with large weld toe radii of curvature.