It is well known that the gaseous elements have detrimental effects on the annealability of white cast iron for malleablizing. The present knowledge, however, is based on the white cast iron containing about 1.0 % Si. Therefore the author made a series of experiments by using the white east irons with silicon content ranging from 1.0 % to 1.8 %, and carr ied out multiple regression analyses of the measurements. The statistically meaningsful results can be summarized as follows:

1) In the silicon range of 1. 01 ∼ 1. 60%, the first stage graphitization is retarded by the soluble nitrogen. However, when silicon exceeds 1. 6 %, the opposite is true.

2) In the silicon range of 1. 01 ∼ 1. 40 %, the second stage graphitization is retarded by the soluble nitrogen. The degree of' the retardation increases as the specimens contain less silicon. When more than 1. 40 % Si is present, the second stage graphitization proceeds independently of soluble nitrogen content.

3) Oxygen does not at. all influence the first stage graphitization, while the second stage graphitization is slightly retarded by oxygen. This is due to nodule count, which decreases as oxygen content increases.