GB495820A - Machineable grey iron castings - Google Patents

Abstract

A machineable grey-iron casting having an all-pearlitic (which may be partly or wholly sorbitic) structure with possible traces of cementite but no free ferrite whatsoever, contains chromium with or without molybdenum or manganese or both and 2,5-7 per cent of silicon, the said casting having been produced by pouring an unsuperheated molten iron containing the above-specified additions in proportions so selected, having regard to the rate of cooling and the section of the casting, that the casting has the said structure. 0,25-6 per cent of chromium and up to 1,5 per cent of manganese and up to 3,5 per cent of molybdenum may be present, 0,3 per cent of molybdenum being approximately equivalent to 0,2 per cent of chromium and 0,25 per cent of manganese being equivalent to 0,15 per cent of chromium (after the first 1,75 per cent of manganese which is stated to be without effect). The rate of cooling in the casting may be controlled by adjustment of the mould-temperature and the castings may be made in cold or preheated moulds of sand &c. or cold or warm metal moulds or stationary or rotating moulds. British Specifications 147,933, [Class 82 (i)], 495,475, and 495,819, and U.S.A. Specification 1,910,034 are referred to.