Size distribution of oxides and toughness of steel weld metals
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چکیده
The trend in strong weld metals is towards microstructures dominated by low carbon martensite. The role of oxide particles introduced into the metal during welding then becomes uncertain. The particles do not seem to affect the nucleation or growth of martensite. This is probably because this phase forms at relatively large driving forces and therefore does not rely on heterogeneous nucleation on oxides, and the oxides are not sufficiently finely dispersed to cause drag on the transformation interfaces. What is clear is that the non-metallic particles can initiate brittle cracks, or voids during ductile failure, both events leading to a deterioration in mechanical properties. Ideally, oxides should be eliminated from the microstructure of martensitic weld metals. This of course is impractical, therefore, one alternative is to minimise the particle size so as to delay oxide related damage to the later stages of stress and strain. The purpose of the work presented here was to verify this alternative approach, even though it seems intuitively obvious that refined oxides should lead to better toughness when they do not influence the development of weld microstructure.
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تاریخ انتشار 2006