Refractory investment and mold

Claim 1

IN COMBINATION, A REFRACTORY MOLD FOR USE IN CASTING METALS MELTING AT OVER 2300* F. COMPRISING A MODEL INVESTMENT, A WAX PATTERN ONE FACE OF WHICH IS IN CONTACT WITH SAID MODEL INVESTMENT, AND AN OUTER INVESTMENT IN CONTACT WITH ANOTHER FACE OF SAID PATTERN, THE OUTER INVESTMENT DIFFERING IN COMPOSITION FROM THE MODEL INVESTMENT AND HAVING A LOWER COMPRESSION STRENGTH THAN THE MODEL INVESTMENT, A THERMAL EXPANSION NOT GREATER THAN THAT OF THE MODEL INVESTMENT, AND A SETTING EXPANSION OF NOT MORE THAN .2% THE MODEL INVESTMENT CONSISTING ESSENTIALLY BY WEIGHT OF FROM 89% TO 71.9% OF A REFRACTORY MATERIAL, FROM 7% TO 18.2% OF A WATER-SOLUBLE ACID PHOSPHATE SALT AND FROM 4% TO 10% OF MAGNESIUM OXIDE, IN WHICH 5% TO 25% BY WEIGHT OF THE REFRACTORY MATERIAL IS ZIRCONIUM SILICATE, AND THE OUTER INVESTMENT CONSISTING ESSENTIALLY BY WEIGHT OF FROM 89% TO 71.8% OF A REFRACTORY MATERIAL, FROM 7% TO 18.2% OF A WATER-SOLUBLE ACID PHOSPHATE SALT AND FROM 4% TO 10% OF MAGNESIUM OXIDE, THE OUTER INVESTMENT BEING SUBSTANTIALLY FREE FROM ZIRCONIUM SILICATE.