High concentrations of hydrogen and nitrogen in molten gray iron increase the risk of porosity in castings. Therefore, equilibrium variations of these gases at different stages in the process chain from melting to casting have been mapped. Both hydrogen and nitrogen content are affected by the melting method. The amount of hydrogen is also sensitive to the dwell-time in ladles and holding furnaces. The total amount of nitrogen, i.e. bonded and dissolved nitrogen, is not significantly affected by the temperature, while the hydrogen content is indirectly affected because of the relationship between dwell-time and temperature.

The amount of dissolved oxygen, as well as oxygen available as oxides, is considered to affect the nucleation and growth of porosity defects in gray iron castings. Therefore, the influence of melting process on oxygen content was investigated in the production at two foundries. The importance of temperature on the equilibrium between the melt and its surrounding was especially examined. It was found that the amount of dissolved oxygen decreased with decreasing temperature, but the total amount of oxygen remained unchanged, meaning that the amount of oxygen found as oxides increased as the temperature decreased.