大型鋼塊用ダクタイル鋳鉄鋳型の寿命について

Abstract

The experimental and practical results of the small ingot mould made of ductile cast iron were reported by many authors. However in the case of the large ingot mould, it seems to be not yet reported in detail.Therefore, the authors made the experiment on the large ingot mould, i.e., C-61 type (weight: 5, 230kg, wall thickness 130mm) and C-56 type (weight: 4, 900kg, wall thickness 125 mm) which are used at Yawata Iron & Steel Works, for the purpose of comparing ductile cast iron with ordinary cast iron.As the result, it was found that the ductile cast iron mould has a longer life. On the other hand, however, some peculiar defects appeared on the inner surface of them in the course of ingot making. Authors diseussed those results mainly on the points of its life, surface crazing and cracking, and change of the microstructure.List of derived conclusions are as follows:1. The favorable result can be expected from the large ductile cast iron mould.2. It has superior resistance to crazing and few exfoliation is noticed on the inner surface of tested moulds.3. Pearlite and spheroidized graphites are decomposed into massive graphites by repeated heatings to 700-750°C.4. Peculiar cracks of ductile cast iron mould must be prevented by the improvement of casting technique or the development of the ingot mould design.