Casting powder

Abstract

Particulate casting material is applied onto the upper surface of molten steel in a vertical continuous casting mold where it rapidly melts to form a protective flux-lubricant molten glass covering which also flows down between the solidifying cast steel and the mold wall. Casting material is a substantially chemically homogeneous, pre-reacted, but substantially unfused mixture of multiple crystalline phases and preferably in a thorough blend of the mixture with up to 10% by weight finely divided graphite. The mixture: (a) analytically consists essentially of, by weight thereof, 20-45% SiO.sub.2, 10-40% CaO and/or SrO and/or BaO, 0-10% Al.sub.2 O.sub.3, 0-11% Fe.sub.2 O.sub.3, 5-25% Na.sub.2 O and/or K.sub.2 O, 0-15% MgO and 3-15% F ion; (b) exhibits not more than 2% weight loss upon heating thereof at 900.degree.C. for 1 hour; and (c) uniformly melts at temperatures of molten steel to form a fluid glass having the following viscosity characteristics: 1-80 poises at 1100.degree.C., 0.1-3 poises at 1500.degree.C. and a set point less than 1150.degree.C. The mixture is formed by thoroughly and intimately mixing a batch of ingredients yielding the aforesaid analytical composition and having an aggregate particle sizing, by weight, of at least 75% -120 mesh and at least 60% -200 mesh, and heating the mixed batch at temperature of at least 550.degree.C. to less than 1000.degree.C. for time sufficient to react and chemically combine the Na.sub.2 O and K.sub.2 O with the other ingredients, to render the resultant mixture substantially chemically homogeneous and to reduce volatiles in that mixture to a level not more than 2% weight loss as aforesaid.

Dependencies are inferred from the claim text.