Formation and analysis of stack cracks in a pipeline steel

• DOI: 10.1007/bf00354254
• Publication Date: 2006-02-22T06:43:42Z
• Authors: M. Y. B. Zakaria; T. J. Davies
• Keywords: Embrittlement; Cleavage (geology)

Extensive cracking of the type known as stack cracking was demonstrated in a cathodically charged X65 microalloyed pipeline steel containing a weldment. It is shown that the formation and propagation of rolling-plane cracks, which constitute the primary stages of the stack cracking, is due to local concentration of hydrogen gas pressure and a lowering of the cohesive strength of a number of interfaces by hydrogen. The characteristic S-shape of individual cracks which occurred during the linking up of cracks was attributed to stress interactions at crack tips and cleavage cracking normal to the rolling plane. An explanation of hydrogen embrittlement fracture is given in terms of electronic state modifications of the steel, including charge polarization.