Weld hydrogen cracking has been recognized as an issue of concern and a wide range of hardenability criteria and single pass weld testing techniques have been developed to demonstrate material weldability, however, hydrogen cracks continue to be identified in welds. The potential for hydrogen cracking is related to the presence of hydrogen, the local tensile strain state and the susceptibility of the material microstructure. The weldment slow bend test and hydrogen effusion and cracking model has been used in Pipeline Research Council International (PRCI) research reported in this paper to support the development of an understanding of the interaction of these factors in promoting hydrogen cracking. The slow bend testing procedure is described with examples of the effects of increasing hydrogen and/or strain conditions are used to illustrate hydrogen cracking susceptibility. The slow bend testing procedure was applied to a range of steel weld metals to develop an understanding of the factors which make one more or less susceptible to hydrogen cracking. Combining the results of slow bend testing, the susceptibility of deposited shielded metal arc weld material to hydrogen cracking is defined using a hydrogen susceptibility curve that establishes the critical strain to form a crack as a function of hydrogen concentration. Cracking susceptibility is described through the definition of material ductility and embrittlement indices, which are derived from the hydrogen susceptibility curves. Cracking susceptibility is then correlated with mechanical, chemical and microstructure properties of the deposited welds. This model to predict weld metal hydrogen cracking susceptibility was developed to support electrode selection and welding procedure development to preclude hydrogen cracking. The results in this paper can be used to reduce the risk of hydrogen cracking and support the development of industry guidance.

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