Study of structure formation during sintering of iron-graphite alloys

Summary

• 1. Nonuniform saturation of austenite by carbon from graphite during sintering is the main cause of the anomalous structure of iron-graphite cermet alloys. The relatively high contents of ash and other impurities in the available graphite have an adverse effect on the structure of sintered alloys and impair their mechanical properties.

• 2. The low rate of diffusion during sintering is another cause of the anomalous structure of the iron-graphite alloys. It is desirable to search for an apply such activating admixtures that would speed up the diffusion of carbon and smooth out the microstructure.

• 3. The circumstance that the nonuniform concentration of carbon iron-graphite cermet products causes the pearlitic conversion to proceed by a mechanism differing from that in molten steels is also responsible for the anomalous structure.

• 4. Observations on iron-copper-graphite alloys during heating from room temperature up to the melting point have shown that a liquid copper phase does not form in mixtures with a copper content within the solubility range in austenite. Consequently, sintering of these mixtures takes place in the solid phase.