GB781083A - Improvements relating to high speed tool forms and their production - Google Patents

Abstract

High speed tools are formed from high speed steel compositions which are unforgeable in the cast conditions by pressing compacts containing at least 50 per cent of high speed steel powder to a self-sustaining mass, heating the mass to a temperature sufficient for coining and coining the heated mass to the desired shape and to a density at least 98.5 per cent of the theoretical maximum density. The high speed steel preferably has a composition of C 0.8-2.0 per cent, Cr 3.5-5.5 per cent, V 1.0-6.0 per cent, W 14.0-20.0 per cent, Mo 4.5-8.5 per cent, Co 5.0-20.0 per cent and the remainder Fe. The powder may be mixed with additional constituents such as ferro-alloys, single or multiple carbides or other refractory hard carbides, nitrides, borides and silicides, carbon or graphite, powdered metals or alloys e.g. Fe-Cr, Fe-Ni-Cr alloys, or hydrides of Fe, Ti or Ca. A lubricant such as stearic acid may also be incorporated. In an example a steel powder was compacted to shape, heated to 2250 DEG F. for 20 minutes in an atmosphere of hydrogen and propane, hot coined in a die using 30-40 tons/sq. in. pressure. In a further example there is used a mixture of 10 per cent tungsten-titanium carbide with a steel powder of composition C 1.84 per cent, Cr 4.66 per cent, V 5.97 per cent, W 15.58 per cent, Mo 5.53 per cent, Co 5.25 per cent, Fe the remainder.