GB495475A - Improvements in or relating to the production of grey cast iron - Google Patents

Abstract

An all-pearlitic structure (which may be partly or wholly sorbitic) with possible traces of cementite, but no free ferrite whatsoever is produced in grey iron castings made in preheated moulds of refractory material and containing materials which inhibit and promote the formation of ferrite, by altering one of the following factors: (a) the quantity of ferrite-promoting material (which must always be so high as normally to produce a ferritic casting); (b) the quantity of ferrite-inhibiting material, and (c) the rate of cooling as determined by the action of the casting and the temperature of the mould. The ferrite-promoting material may be one or more of silicon, nickel, or copper in amount equivalent to 1,5-7 per cent of silicon, it being reckoned that 0,4 per bent of silicon is equivalent to 1 per cent of nickel and 0,35 per cent of silicon is equivalent to 1 per cent of copper, no more than 3,5 per cent of nickel and 4 per cent of copper being however present. The ferrite-inhibiting material may be one or more of chromium, manganese, or molybdenum, in amount equal to 1-6 per cent, up to 3,5 per cent, and up to 1,5 per cent respectively, it being reckoned that 0,3 per cent of molybdenum is approximately equal to 0,2 per cent of chromium and 0,25 per cent of manganese (after the first 1,75 per cent of manganese, which is stated to be without effect) being equal to 0,15 per cent of chromium. The inhibiting-material may be added to the cast in the pouring-ladle, the cast preferably containing a quantity of scrap from a previous operation. Specifications 147,933, [Class 82 (i)], and 495,820 are referred to. Reference has been directed by the Comptroller to Specification 245,196, [Class 82 (i)].