A model of hydrogen assisted cold cracking in weld metal

Abstract

Due to significant cost and productivity advantages, low heat inputs, high welding speeds, severe loading conditions and the use of cellulosic electrodes in the construction of oil and gas pipelines are unavoidable in Australia. Another significant cost reduction directly related to the tonnage of steel pipe dictates the wider use of higher grade steels, such as X70, X80 or X100. These current tendencies raise a serious concern regarding potential problems associated with weld metal hydrogen assisted cold cracking, HACC. Although there are industry standards and guidelines for the avoidance of hydrogen cracking in the heat affected zone, this is not the case for the weld metal, which is now more likely source of crack initiation in modern pipeline steels. The current paper develops a simplified mathematical model to predict the risk of hydrogen cracking in weld metal. A sensitivity study is conducted to evaluate the effect of various welding parameters and geometry, such as heat input, preheat and ambient temperatures and wall thickness on the risk of hydrogen cracking.