Alumina and MgO preheatable insulating refractory liners and methods of use thereof

Claim 1

A preheatable molded refractory insulating liner structure prior to preheating of predetermined shape having insulating porosity for a metal casting vessel suitable for developing sufficient hot strength to maintain the integrity of the structure at vessel preheat and molten metal casting temperatures which are in the range of about 1900° F. to about 3000° F. comprising a molded uniform mixture having a substantial insulating porosity on the order of about 50% prior to preheating containing a particulate refractory component in an amount of about 75% to about 98.5% by weight of said preheatable liner structure of a mixture of alumina and MgO refractory grain wherein said alumina and MgO refractory grain are in a ratio of about 1:1 to about 1:94, respectively, and a binder for said component and inorganic fibrous material in sufficient amounts to maintain the predetermined shape of insulating porosity at least prior to the preheat temperatures wherein said alumina and MgO refractory grain are of a particle size in said preheatable liner structure to facilitate the formation of spinel bonding which results in increased hot strength with substantial maintenance of insulating porosity and shape without substantial shrinkage at both the vessel preheat temperatures of about 1900° F. to about 2400° F. and higher metal casting temperatures when said preheatable liner structure is used in a casting vessel heated for a sufficient period of time.