Selection of reducing atmosphere in the secondary reduction of iron powder

Classification of reducing atmosphere

Reduction atmosphere refers to the atmosphere through the reduction furnace under high temperature conditions, mainly hydrogen, no or very little free oxygen exists, used for iron powder deoxygenation and decarbonization;The reducing gases used in the secondary reduction process mainly include pure hydrogen and decomposed ammonia. 

Contrast of reducing atmosphere

Hydrogen and decomposition of ammonia are gases can be used as a secondary reduction iron powder, the two gases is there is no high carbon potential of the components, can completely prevent the carburizing phenomenon in the process of reduction Compared with pure hydrogen, although has 25% N2 N2 in the decomposition of ammonia are inert gas, but it reduced the concentration of active ingredients of reductive gas, can make the atmosphere of reducing power decreases Due to the spread of H2 is greater than that of N2 diffusion ability, N2 influence on H2 ratio on C0 much smaller At the same time, about 20% N2 to H2 reduction rate of ferric oxideIn addition, due to the lower price of decomposed ammonia than pure hydrogen, it is easy to produce in industrial production, so although pure hydrogen is the best gas for secondary reduction, but most of the powder metallurgy plants at home and abroad are still willing to adopt decomposed ammonia.