Mold part composition and process of making same

Claim 1

THE PROCESS OF PREPARING A FOUNDRY MOLD PART HAVING IMPROVED DIMENSIONAL STABILITY CHARACTERISTICS CONSISTING OF THE STEPS OF PREPARING A FIRST ADMIXTURE, SAID FIRST ADMIXTURE CONSISTING ESSENTIALLY OF ABOUT 30 PERCENT BY WEIGHT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ANHYDROUS CALCIUM SULFATE AND HEMIHYDRATE OF CALCIUM SULFATE WITH ABOUT 70 PERCENT BY WEIGHT OF SILICA FLOUR AND ADDING WATER THERETO IN SUFFICIENT AMOUNT TO PROVIDE WATER TO HYDRATION TO FORM SUBSTANTIALLY THE DIHYDRATE OF SAID SULFATE, ALLOWING THE RESULTING MASS OF SET UNTIL THE REACTION OF HYDRATION IS SUBSTANTIALLY COMPLETE, HEATING THE COMPOSITE THUS OBTAINED SUFFICIENTLY TO INDUCE AT LEAST A PARTIAL INTERACTION BETWEEN THE HYDRATE OF CALCIUM SULFATE AND SILICA AND PULVERIZING THE PRODUCT OBTAINED THEREBY, PREPARING A SECOND ADMIXTURE, SAID SECOND ADMIXTURE CONSISTING ESSENTIALLY OF ABOUT 30 PERCENT BY WEIGHT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OFANHYDROUS CALCIUM SULFATE AND HEMIHYDRATE OF CALCIUM SULFATE WITH ABOUT 70 PERCENT BY WEIGHT OF SILICA FLOUR AND ADDING THERETO AN EFFECTIVE AMOUNT UP TO ABOUT 6 PERCENT BY WEIGHT OF A DIMENSIONAL STABILITY IMPROVING AGENT CONSISTING OF POWDER PORTLAND CEMENT, PREPARING A BLEND CONSISTING ESSENTIALLY TO SUBSTANTIALLY EQUAL PORTIONS BY WEIGHT OF SAID FIRST ADMIXTURE WITH SAID SECOND ADMIXTURE, ADDING WATER TO SAID BLEND IN SUFFICIENT AMOUNT TO RENDER THE RESULTING COMPOSITION FLUID FOR FORMING SAID MOLD PART AND ALLOWING SAID COMPOSITION TO SOLIDIFY IN FORM OF SAID MOLD PART BY CHEMICAL HYDRATION THEREOF.