Abstract
Being excited by Meehanite Metal, foundrymen in our country recently pay attention to the melting process in the use of much steel scrap by which a superior iron casting is obtained. In viewpoint of enabling this process to be easy by trying to melt iron at a higher temperature, authors investigated properties of cast iron under the various operational conditions by using the midget cupola of the internal diameter 200 mm. The results obtained are as follows: (1) Under the best operational condition, the specimen was carburized to 3.1∼3.2%C, and had the tensile strength 38 kg/mm2, good fluidity, a fine structure and good resistance in pressure test. (2) For obtaining the above good properties it is necessary that the used ratio of steel scrap should be high and also the tapping temperature should be about 1500°C. When the used ratio of steel scrap is less than 50 per cent, cast iron is carburized too much and has not a good properties because of showing a bad effect of raw material. (3) In order to rize the tapping temperature above 1500°C, coke of good quality and the coke ratio 25∼30 per cent were used, and therefrom the volume of blast was increased. It will be suitable that the coke ratio of the large cupola is about 20 per cent. (4) Inoculation of calcium siliside is necessary for cast iron not to chill easily. The adequate addition is 0.35 per cent. It was accertained by the analysis of oxides that acceleration of graphitization of calcium siliside is due to deoxidation of molten iron.
