In modern times, energy resources in polar region and abyss receives more attention due to the increased possibility of economic production of crude oil and natural gas resources. As the offshore plant and vessels installed in polar region or abyss are operated in extreme environments, the high strength and low temperature toughness properties of a structural steel is required, and the high strength weld consumables of low hydrogen type need to be applied for the requirement of structural integrity. However, when we add alloying elements to meet the high strength and lowr temperature toughness of steels and weld consumables, the weldability is normally degraded due to increase of the carbon equivalent of the welds. Heat-affected zone (HAZ) was the critical flaw for cold cracking until we used the steels to medium strength, but the location of cold cracking was incrementally shifted to the deposited metal with increasing the use of high strength steels. Therefore, previous studies of cold crack testing consists of two geometry, i.e. Y-groove and y-groove. Many studies were conducted to examine the effect of preheating temperature and diffusible hydrogen content using various FCA consumables on the cold crack. However, there is few studies to collaborate the effect of strength grade, diffusible hydrogen content, base metal thickness, preheating temperature, and groove geometry on the cold crack. The main objective of the study is to understand how the groove geometry and base metal thickness influence the cold cracks for each strength grade and diffusible hydrogen content. We used a various strength grade of welding consumable from YS.375 to 500 MPa and base metal thickness of 20mm and 40mm. Comprehensive analysis of hardness distribution. microstructure, and diffusible hydrogen content was also performed in the weld metals to understand cold crack ratio and cold crack propagation behaviour.
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