Patents
A single step batch process has been developed to prepare spheroidal graphite iron from beneficiated iron ore slime concentrate by plasma smelting using LECO (a coke produced from lignite where fixed carbon is 74.03%) as the carbonaceous reductant. A dc extended arc plasma furnace (35 kWh) was employed to carry out the smelting at 0.5-2 Kg scale. Basicity of slag in the charge was varied between 1 and 2 over five different compositions to achieve the maximum metal yield with good fluidity of melt. The maximum yield was recorded at a slag basicity 1.5-1.8 without sacrificing melt fluidity. The pig iron melt produced after smelting was cast into a graphite mould where Fe-40% Si-9% Mg alloy was added to spheroidize graphite in the cast iron matrix. The SG product was recovered from the mould after cooling for 30-60 min in air. XRD analysis of the said product identified Fe to be the major phase along with the occurrence of graphite as minor phase. Small quantities of Fe2C, Fe3C and Fe304 were also detected. On examination under optical microscope, the product revealed nodular graphite particles with a density 1400/mm2 and less. The diameter of the graphite spherulite was found to be 16 urn and less. Chemical analysis of the SG casting showed the critical impurities to lie in the following levels: C 4.4-6, S 0.11- 0.16, P 0.05-0.069, Si 2.1-2.3, Mg 0.02-0.05 (wt.%). Fe content was found in the range 90-92 wt. %.