TWI Industrial Member Report Summary 524/1995
S Bond and T G Gooch
Welded steels can suffer cracking in aqueous media as a result of hydrogen pickup from the cathodic corrosion reaction. This problem has been experienced in a wide range of environments, and becomes more severe as the material hardness increases. Cracking is promoted by the presence of H2S in particular, and for sour oil and gas service a maximum hardness limit of 250HV has been established to avoid the problem. Fewer data are available appropriate to other media. The present study was carried out to examine the influence of hardness on behaviour of welded joints in simulated seawater containing low levels of H2S, with and without cathodic polarisation.
A range of steels was selected with 380-1020MPa 0.2% proof stress. Test beads were deposited to give maximum heat affected zone hardness levels of 270-590HV. Samples were tested in a range of environmental conditions with pH from 3.5 to 8 and below 5ppm H2S, for over 720 hours, loaded in four point bend to 95% of the 0.2% proof stress. Cracking was assessed by sectioning and metallographic examination, and related to the local maximum material hardness.
To examine the influence of material and environmental variables upon the SCC behaviour of welded steels in aqueous environments.