Welding Sequence Effect on the Mechanical Properties of BS460B Medium Strength Offshore Steel

Abstract

In this paper the optimum welding sequence to enhance the mechanical performance of offshore structure fabricated with medium carbon steel was presented. This was achieved by investigating the influence of altering the sequence of welding on the mechanical properties of three welded separate thick plate of dimension 120 x 120 x 120 mm from the same material. Double “V” edged preparation, the same electrode, manual metal arc welding process (SWAM) with the same welding parameters were used for weld plate manufacture. The first plate tag welding sequence one was fully welded in the upper groove before the down groove while the second plate (welding sequence two) was welded half way in the upper groove and halfway in the down groove. Both grooves were then completely filled simultaneously. The third plate (welding sequence three) was welded half way in the upper groove followed by complete filling up of the down groove before the upper groove was then completed. Specimens for tensile, compressive, impact and hardness strength test were extracted from the weld metal zone and the heat affected zone. The result of the mechanical tests carried out on these specimens revealed that welding sequence two possess the highest tensile strength of 686(Mpa) and 421 Mpa in un-weld metal region (HAZ). The weld metal regions of the same welding sequence two possess the optimal performance in compressive and impact strength but with the least average hardness value. This experimental investigation revealed that welding sequence two is the best welding sequence for the offshore steel used.