Carbonyl iron powder reacts with iron at high temperature and pressure to form 5-carbonyl iron oil, which is separated under low pressure to obtain the product. It can be delivered after annealing and anti-oxidation treatment.
In the decomposition process, because Fe catalyzes the conversion of CO to CO2, NH3 is usually used as a protective gas to inhibit the reaction. In this way, the existence of N element is inevitable in carbonyl iron powder. The iron content of products collected from cyclone collector is about 97%, and the contents of C and N are less than 1%. Because of the existence of impurities such as Fe2O3 and Fe3N, and the adsorption of CO and NH3 on the surface of iron powder, these factors lead to the hardness of iron powder, which is usually called hard powder.
Reduction of iron powder with H2 gas for 1 hour will increase the iron content to about 99.0%, while the content of other elements will also be significantly reduced. This reduced carbonyl iron powder has a slightly lower hardness and is also called soft powder.
Carbonyl iron powder is very active, and it will automatically agglomerate with the increase of entropy after normal storage for a period of time. The particle size of agglomerated iron powder increases and the particles stick to each other, which has a great influence on the application of injection moulding.
The requirement of carbonyl iron powder is very high. When 5 carbonyl iron is decomposed, the particle size and carbon content of carbonyl iron powder can be changed obviously by 3 degrees of temperature change and 5% increase of gas flow rate.
Carbonyl iron powder belongs to spherical particles. It has the characteristics of onion spherical layered structure, ultra-fine particle size, non-cohesive particles, uniform particle size distribution, good fluidity, high density, easy to form and sinter, high hardness and high holding capacity. It is widely used in magnetic powder cores of electronic components, synthetic diamond catalysts, metal injection moulding, traditional powder metallurgy, microwave absorbing materials, magnetic shock absorbers, nutritional iron supplement and other fields.