Controlling gas content and metallurgy

In the manufacture of cast steel parts, controlling the dissolved gas content in the metal is a constant challenge in the quest for quality. In general, the foundryman is particularly interested in the harmful effects of excessive gas contents (H, O, N), which can lead to the formation of volume defects that can result in the scrapping of parts. The most frequently encountered volume defects are internal porosities or linear discontinuities on the surface of parts. The uncontrolled presence of excess gas also has repercussions on mechanical characteristics such as ductility, toughness or fatigue strength, and can significantly reduce the service life of the parts concerned.

In addition to this harmful effect, the controlled addition of gases to steels has proved extremely effective in refining grain size and improving the mechanical characteristics and performance...