High pressure rolling of low carbon steel weld seams: Part 1 – Effects on mechanical properties and microstructure

One technique for reducing residual stress in welds is high pressure rolling of the weld seam. In this study, a variety of experimental techniques, including microhardness measurements and cross-weld tensile tests with digital image correlation, have been used to characterise the effects of rolling on the mechanical properties and microstructure of the weld material in welded structural steel specimens. It is shown that rolling applied at high temperature, as welding is carried out, promotes the formation of acicular ferrite in the weld metal. This produces a weld material with a greater yield strength and hardness, but slightly reduced impact toughness compared to unrolled welds. Rolling of the weld metal once it has cooled instead causes work-hardening. These effects are discussed as they relate to the use of rolling for weld residual stress reduction.