Heat treatment of metals

摘要

Ferrous metal is treated by austenitic nitro-carburizing in a heat treatment furnace. A suitable atmosphere is created by admitting to the furnace nitrogen; ammonia; and a liquid or vaporous organic compound of carbon, hydrogen and oxygen. The atmosphere is maintained at a temperature in the range 690 DEG to 750 DEG C. The organic compound is typically methanol and the atmosphere typically comprises nitrogen, carbon monoxide, hydrogen and free ammonia as well as small amounts of methane, carbon dioxide and water vapor. After being removed from the furnace, the ferrous metal is quenched. It has an outer surface layer of white, scuff-resistant, epsilon compound and an inner carbo-nitrided case containing austenitic and martensitic zone. The ferrous metal may then be treated to convert austenite to martensite or lower bainite.