Abstract: A system for recycling heat treating salts such as nitrates and nitrites from a rinse bath including means to prevent the excessive build-up of impurities such as carbonates or chlorides which impair heat treat efficiency. For example, carbonates which form in a nitrate-nitrite quench bath and chlorides which are carried by drag-out into a nitrate-nitrite quench bath from a chloride heat treating bath are removed by concentrating the rinse water, removing undesirable components from the concentrate and returning molten rectified salt to the quench.

Abstract: A cyanide-free molten salt carburizing process and composition comprising an alkali metal salt bath having a cover of finely divided graphite particles in a size range of about 100 mesh to about 300 mesh. The bath is operated in the temperature range of about 1550.degree. F. to 1900.degree. F. and is provided with mechanical agitation to produce entrainment of air through the surface cover and sufficient mobility of carbon monoxide coated graphite particles to produce carbon diffusion by contact into the surface of the parts immersed in the bath. Total graphite content is between about 11/2% to about 7% of the active portion of the bath. The graphite is preferably of the synthetic type so as to produce an ash content below about 1%.

Abstract: A system for recycling heat treating salts such as nitrates and nitrites from a rinse bath including means to prevent the excessive build-up of impurities such as carbonates which impair heat treat efficiency. For example, carbonates which form in a nitrate-nitrite quench bath are removed by concentrating the rinse water, rectifying the concentrate and returning molten rectified salt to the quench.