METHOD FOR OXYGEN FREE CARBURIZATION IN ATMOSPHERIC PRESSURE FURNACES

摘要

A method of oxygen- free heat treatment of a steel part in an atmospheric pressure furnace is disclosed. The present batch treatment process employs an oxygen-free controlled gas atmosphere including hydrogen gas in concentrations between about 1.0 percent to 10.0 percent, a hydrocarbon gas, such as propylene, in concentrations of between about 0.1 percent and 10.0 percent that varies as a function of time, with the balance of the gas atmosphere being nitrogen. The present continuous furnace treatment process employs a plurality of zones with each zone including an oxygen-free controlled gas atmosphere including hydrogen gas in concentrations between about 1.0 percent to 10.0 percent that varies across the different zones, a hydrocarbon gas, such as propylene, in concentrations of between about 0.1 percent and 10.0 percent that varies across the different zones, with the balance of the gas atmosphere within each zone being nitrogen. The presently disclosed oxygen-free heat treatment processes, preferably carburization processes, use a precisely controlled atmosphere to minimize inter- granular oxidation, eliminate the formation of soot and cementite or other metallic carbides, and avoid hydrogen embrittlement.