In order to obtain sintering compact with high strength, it is necessary to remove excessive amounts of carbon in cast iron powder. We investigated conditions of rust formation on the powder, which was soaked in water and dried. We also examined a decarburization process by oxygen contained in the rust. The results were as follows.
(1) Rust could easily adhere to the surface of the powder with a function of desired quantity of oxygen when the powder, registering between 150°-200°C, was soaked in water and then dried.
(2) Carbon was removed as mainly CO gas. This action of decarburizing ended when all the oxygen was consumed.
(3) In order to obtain powder containing desired carbon and less oxide, it is necessary to heat this powder at a temperature of 1000°-1050°C for 2 hours in vacuum.
(4) The cast iron powder decarburized in this method will be useful for powder metallurgy.