Lean atmospheres for sintering chromium alloyed PM steels

Paper in proceeding, 2013

Hydrogen and carbon monoxide are effective reducing agents at different temperature ranges and there is only scarce experimental and theoretical data about their interaction and combined reducing effect at dry conditions and low amount. The work presents experimental and theoretical evaluation of the reducing and carburizing activity of lean nitrogen-based atmospheres containing hydrogen, carbon monoxide and small additions of hydrocarbons with their total content in the range of 0.3 to 5 vol%. Effect of carbon content (0 and 0.4 wt%) and temperature profile in the case of sintering of chromium prealloyed PM steels was evaluated. Results indicate that the carbon pickup increases with increasing CO content in the atmosphere, however it brings significant risk of oxidation. Atmospheres with low content of CO and H2 (<1.5 vol% of both) and small hydrocarbon additions showed to be good candidates for robust sintering of chromium alloyed PM steels.