THE EFFECT OF COPPER AND NICKEL ADDITIONS TO HIGH-COMPRESSIBILITY SPONGE IRON POWDER ON THE SINTERED PROPERTIES OF MATERIALS WITH 0·3 AND 0.60% CARBON

Abstract

Up to 5% each of copper and nickel powders as well as 0.35 or 0.65 wt.-% graphite were added to sponge iron powder grade SC 100.26. Tensile specimens prepared from the mixes were sintered in endogas in a belt furnace at 1120°C for 1 h. Dimensional change, hardness, and tensile properties were measured. The results show that the tensile strength increases with increasing copper and nickel additions at each carbon content level and that copper has the greatest influence. Since plain copper additions cause considerable growth during sintering, it is advantageous to combine the two elements. Conditions for ‘zero growth’ have been established. The highest strength for a ‘zero growth’ material was achieved with an alloy containing 4.0% Ni, 2·5% Cu, and 0.6% C, with a density of 7.1 g/cm₃. Retention of austenite seems to limit the strengthening effect of nickel at this carbon content. Addition of molybdenum counteracts this effect and raises the strength. With a partially prealloyed powder containing 4% Ni, 1·5% Cu, and 0·5% Mo a tensile strength of 750 N/mm² is obtained at a carbon content of 0·6%. It is recommended, however, that the carbon content should be 0·6% in combination with nickel additions ⩾4%.

Notes

* Manuscript received 8 April 1974. Contribution to a Symposium on ‘Factors Affecting the Uses of PM Products’, to be held in Eastbourne on 28–30 October 1974