The Effect of Residual Stress and Microstructure on Distortion in Thin Welded Steel Plates

Abstract

The current trend in ship construction is to reduce the thickness of the ship panels, in order to minimize weight and maximize vessel speed. The ship panels of interest consist of 4 mm thick butt welded plates. This reduction in panel thickness may lead to excessive plate distortion during welding, resulting in significant additional costs during assembly. A ferritic-pearlitic DH-36 steel is used, in which phase transformations during welding may affect the distortion and stress states observed. Two large plates, representative of ship panels, have been butt welded using a metal inert gas (MIG) process. The temperature histories have been recorded during welding and the resulting distortion profile has been obtained using digital photography. Neutron diffraction measurements have been performed to determine the residual stress state in the plates before welding, due to e.g. processing and laser cutting, and after butt welding of the plates. Reference matchsticks from the weld, heat affected zone (HAZ) and parent plate have been taken from similar locations in nominally identical plates and measured to obtain the strain/stress free lattice parameter, α0. A Rietveld analysis has been performed on the diffraction data. Post welding, hardness surveys have indicated the microstructural variation in the weld, parent plate and HAZ. Results from these on-going studies are presented which identify the key factors responsible for thin plate distortion.

Effect of low transformation temperature weld filler metal on welding residual stress

“…Analyses have been performed to examine the influence of the transformation start T s temperature on residual stress predictions. The results have been compared to the stress distributions measured previously 22,23 for welds manufactured using both conventional and low transformation temperature filler wires. The following conclusions can be drawn:…”

“…Two high strength low alloy, DH-36 steel plates (base metal) 500 mm long, 250 mm wide and 4 mm thick were joined by a butt weld, using GMAW. 22,23 Two 2 mm diameter weld consumables were used, a conventional weld wire (CW) exhibiting a solid state phase transformation at y560uC, and a wire with a lower transformation temperature (LTTW) of 420uC. The chemical compositions are shown in Table 1.…”

Effect of variant transformations in fusion zones of gas metal arc welds

“…Weld samples were fabricated using manual gas metal arc welding (GMAW) procedure. [29][30][31] Two high strength low alloy steel plates of dimensions 500 mm long, 250 mm wide and 4 mm thick were single pass butt welded. A CW wire with high transformation start temperature, i.e.…”

Comparison of Residual Stress Between MIG Welding and Friction Stir Welding

“…Experimentally determined residual stress measurements, which were obtained using the neutron diffraction technique, are available on a large (1000 mm ×1004 mm) MIG butt welded plate. These measurements were performed at the plates mid-thickness, and mid-length and transverse the weld, refer to reference [4] for the detail.…”