High speed steel cutting tools - directly cast in sand moulds, then annealed and heat-treated

摘要

A steel is melted with compsn. by wt.: 1-1.2, pref. 1.05-1.15% C; 0-0.6, pref. 0.4-0.6% Si; 0-0.4% Mn, 0-0.03% S, 0-0.03% P, 10-12% W, 3.8-4.5% Cr, 2.8-3.i% V, 2.8-3.i% Mo, 4-5% Co, balance Fe; the tool is cast in this steel and annealed 5-10 hours at 850-870 degrees C, cooled then heated to 1190-1230 degrees c, quenched, and tempered at 545-575 degrees C. The moulds are pref. sand moulds with compsn. (a) silica sand 100 AFA, with 0.2-0.3% clay, 2-2.5% linseed oil, 1-1.5% molasses, total binder 2-2.k%; or (b) silica sand 60 AFA, with 1-1.k% clay, 0.5-1% linseed oil, 0.5-1% molasses, total binder 2.5-3%, 0.2% water. The steel obtd. is used e.g. in tools for turning, drilling and milling. When the tools are worn and can no longer be re-used, instead of sending them to a steelworks for remelting into bar, etc., they are directly recast, i.e. used in cast tools.