Effect of Sulphur on Solidification Cracking in Weld Metal of Steel (Report 5) : Sulphide and Solidification Crack Susceptibility in Fe-S-Mn-Ni and Fe-S-Mn-C Quarternary Alloy Steels

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It is well known that nickel and carbon considerably promote the weld solidification crack in steel. It is not clear, however, whether manganese is still effective to prevent the detrimental effect of sulphur even in a steel containing nickel or carbon. Moreover the change in the behaviour of sulphide with an increase in nickel or carbon content has been hardly investigated so far. In this report, the effects of nickel, carbon and manganese on the behaviour of sulphide and the weld solidification crack are investigated using Fe-S-Mn-Ni and Fe-S-Mn-C alloy steels containing somewhat higher amount of sulphur than commercial steel. As the result, it is revealed that nickel and carbon cause the formation of a filmlike sulphide, but an additional increase in manganese content returns the sulphide to the original globular one and sufficiently lowers the crack susceptibility. Further, in a weld metal solidifying austenite phase due to the presence of nickel or carbon, a general law which gives the manganese content required to sufficiently lower the crack susceptibility is discussed.
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