High Resistance Vacuum Melted Cast Irofn with 5 Per Cent Silicon Content

Abstract

When melted under vacuum (1 to 5.1O-amm Hg) and cast in metallic molds, cast iron with 2.7 to 2.S% carbon and 5%. silicon content has 55 to 65 kg/mm2 (7S,000 to 92,000 psi ) ultimate tensile strength, be­ tween 255 and 275 Brinell hardness and a reasonable impact strength. This iron has excellent machining properties. Even 22 mm (% in.) diameter die cast bars are altogether gray without any trace of chill. All melts referred to in this paper have been prepared out of good quality commercial raw ma­ terial (pig iron for ductile iron ) with, in most cases, normal 75% ferro silicon additions. Some differences were noticed when other qualities of ferrosilicon were used. The high resistance of this iron can be attributed to the very fine dispersion of graphite in a silicon rich ferritic matrix.