Abstract

The properties of cast iron which are essential to successful working of Diesel engine cylinder and piston differ in many respects, especially on temperature and stress conditions, from those of irons, ordinarily employed for steam engine or general engineering purposes. The object of this paper is to investigate the essential properties and characteristics of cast iron for Diesel engine, and set out some of the results of tests which have been made on irons of different qualities and compositions, in the hope they may provoke a discussion from which some suggestions for further works to get more suitable cast iron may arise. In the first place, some experiments were carried out with a view to determlning the cause of decrement of tensile strength of cast iron at elevated termperature, and deduced the causes as follows : (1) Reduction of Intercrystalline cohesion of metal.(2) Decomposition of Pearlite carbide. From the results or the author's experiments, it was seen that higher tensile cast iron at ordinary temperature may keep also higher intercrystalline cohesion even at elevated temperature. It is too much clear to say that the increasing of stability of carbide will retard its decomposition at high temperature. One of the principal means of securing high tensile cast iron is melting a mixture of steel scraps and pig irons and, of securing stable carbide is to increase manganese content. These facts lead us to the conclusion that semi-steel high in manganese may answer above two requirements. A number of experiments were carried out with semi-steel containing considerable amount of manganese and the results obtained were very satisfactory. It was conclucled, as the results of these experiments, that semi-steel high in manganese will be successfully used for Diesel engine castings. The allowable amounts of manganese and silicon are to be in the range of the author's emperical formulae which should be applied where the amount of total carbon equals to from 3 to 3・5% : -[numerical formula], [numerical formula]. Where. Si.=Silicon in percentage. T.C.=Total carbon in percentage. Mn.=Manganese in percentage.