Patent GB-212258-A (GB)
Title: An improved process for casting iron in permanent moulds at a regulated cooling rate
IPC: B22C3/00
Filed: 1924-02-28
Abstract: 212,258. Holley, E., (Assignee of Meloche, D. H.). March 3, 1923, [Convention date]. Mould materials; casting processes; moulds; clamping moulds.-Relates to the production of self-annealed grey iron castings in metal moulds and consists in the regulation of (1) the temperature of the iron poured, (2) the temperature of the metal surface, (3) the mould wall thickness, (4) the provision of a refractory lining for the mould, (5) the application to the lining of a thick coating of lampblack, (6) the cleaning of the mould, (7) yielding means for clamping the moulds, (8) the prevention of leakage from the mould by means of a narrow contact bead or rim as described in Specification 21676/12, (9) the arrangement of special cooling means in the case of large castings, (10) the composition of the iron cast, (11) the composition of the metal moulds. The moulds are of the same composition as the iron to be cast which has preferably a silicon content greater than 2.75 per cent, a manganese contact between 0.4 per cent and 0.6 per cent, total carbon content between 2.5 per cent and 3.5 per cent, combined carbon of the pig less than 0.7 per cent and sulphur oxygen and phosphorus low. In melting the iron not more than 10 per cent low-carbon steel scrap (0.2 per cent to 0.3 per cent) should be added and the cupola blast is regulated so that the melting zone is confined to a few inches. A mixture of 50 per cent scrap, of composition similar to that set out above, and 50 per cent pig may be used. The moulds may be cast in sand or in permanent moulds and the outer skin may be removed by a small hand grinder. After cleaning, the moulds may be heated for an hour to 1500‹ F. to relieve strain that might result in distortion. A refractory coating is then painted on at a mould temperature of 500‹ F., a suitable composition being a 10 per cent saturated solution of sodium silicate in water with an equal weight of finely ground fireclay. For complicated castings a less proportion of fireclay is used. When a thick coating is required the mould temperature is raised to above 1000‹ F. to bake each layer of about 0.01" after application. A coating of “" can be built up in this way. A layer of lampblack is next applied of such thickness that the coating is substantially intact after the casting has been ejected. For castings of 2 lb. weight with sections of from 3/16" to ¥" thickness hollow cast iron moulds of ¢" wall thickness with a refractory lining of 1/64" thickness and a lampblack coating of 1/32" thickness are employed. A casting is poured every 1¢ to 2 minutes and the mould surfaces attain a temperature of 1000‹ F. The pouring temperature exceeds 2200‹ F. and the casting is ejected at a temperature of 1650‹ F. With castings of various sizes the conditions are adjusted to maintain the solidification time in the neighbourhood of 30 seconds, and the frequency of pouring is regulated to keep the mould temperature below 1150‹ F. For large castings the air cooling means described in Specification 197,334 may be employed. The moulds are mounted on a. rotating table and the castings are ejected as described in Specification 186,906, the moulds are cleaned after casting hv an air blast as described in Specification 199,390 and the lampblack is reapplied bv a burner as described in Specification 204,688. Specifications 201,913, 202,273 and 209,043 are also referred to.