GB589385A - A process for improving the properties of metal castings made by the centrifugal method - Google Patents

Abstract

The properties of centrifugally cast carbon or alloy steels, e.g., carbon chromium steels, 7 per cent. chromium tungsten steels, austenitic rustless steels, and 3 per cent. chromium molybdenum steels, are improved by subjecting the metal while hot to mechanical work to effect changes in dimensions in no case greater than 60 per cent. The working should be effected at a temperature 50 to 100 DEG C. below the normal forging temperature of the metal treated and may comprise expanding, upsetting or drawing. The casting may be roughly machined before working. Examples are given of the effect of the process when applied to alloy steels containing : I carbon 0.4, silicon 1.71, manganese 0.79, chromium 20.6, nickel 8.3, and tungsten 3.81 per cent.; II, carbon 0.11, silicon 1.29 manganese 0.3, chromium 18.3, nickel 8.88, and molybdenum 2.98 per cent.; III, carbon 0.3, silicon 1.29, manganese 0.40, chromium 14.14, nickel 12.52, and tungsten 2.70 per cent.; or IV, carbon 0.35, silicon 0.29, manganese 0.85, sulphur, 0.025, phosphorus 0.025, chromium 3.4, nickel 0.19, molybdenum 0.62. and vanadium 0.17 per cent. Examples are also given of the effect on the physical properties of eight alloy steels of various heat treatments and degrees of hot working. The analyses are as follows : <TABS:0589385/II/1> Each steel was cast, heated to 1,000 DEG or 1,200 DEG and A.C., i.e. air cooled to room temperature. No. 1 steel was then heated to 860 DEG , O.H., i.e., cooled in oil, heated to 610 DEG , A.C., forged to alter a dimension 60 per cent. at, or merely heated to, 1,000 DEG or 1,200 DEG , A.C., heated to 860 DEG , O.H. and heated to 610 DEG , A.C. No. 2 steel was heated to 850 DEG , S.C., i.e., cooled slowly, heated to or forged at 1,000 DEG or 1,200 DEG , A.C., and heated to 850 DEG S.C. No. 3 steel was heated to 950 DEG , A.C., then to 750 DEG , A.C., heated to or forged at 1,000 DEG or 1,200 DEG A.C., heated to 950 DEG , A.C., and then to 750 DEG , A.C. No. 4 steel was heated to 850 DEG , S.C., heated to or forged at 1,000 DEG or 1,200 DEG , A.C., and heated to 850 DEG , A.C. No. 5 steel was heated to 860 DEG , O.H., heated to 670 DEG , A.C., heated to or forged at 1,000 DEG or 1,200 DEG , A.C., heated to 860 DEG , O.H., and heated to 670 DEG , A.C. Nos. 6, 7 and 8 steels were forged, if at all, at the first heating and this was followed for Nos. 6 and 7 by heating to 1,050 DEG , A.C., and for No. 8 by heating to 950 DEG , A.C. The effect of forging to alter a dimension 30 instead of 60 per cent. is also given in the case of Nos. 6, 7 and 8. U.S.A. Specification 1,995,419 is referred to.