Formation of sulphide 'patches' on inclusions in C-Mn steel weld metal

Following earlier observations indicating that sulphide coatings can form on inclusion surfaces in a C-Mn steel weld metal when cooled from high temperature, experiments have been carried out to examine the effects of cooling rate on the nature of sulphide precipitation on inclusions when cooled through the austenite range. It is found that fast cooling rates give thin films whereas slow rates produce thick films or 'patches'. The increase in film thickness is assessed in terms of the S/Mn ratio as measured by EDX.