A PRACTICAL STUDY ON HIGH CHROMIUM CAST IRON.

This experiment was carried out with two objects, one is for obtaining more durable heat-resisting casting by changing the chemical composition in high chromium cast iron, and the other for obtaining good wear-resisting cast iron by this high chromium alloy. For the heat resistance, the oxidation at a high temperature and the toughness were studied by means of the thermo-balance method and impact testing.The following result was obtained as a desirable composition:-Carbon 20 to 2·4 per cent, chromium 22 to 26 per cent, silicon 0·6 to 08 per cent manganese 1·0 to 20 per cent and aluminium 0·5 to 1·0 per cent.For the wear resistance, it is necessary to soften the material by annealing to ensure machining, and after the completion of machining, it is also necessary to harden it by air cooling. For this purpose, the effect of chemical composition and heat treatment on the hardness or the bending strength were studied, and the following composition was obtained as a desirable one:-Carbon 1·8 to 2·2 per cent, silicon 0·4 to 0·8 per cent, manganese 0·4 to 0·8 per cent and chromium 17 to 22 per cent.