Process for producing improved cast iron

Claim 1

THE IMPROVED METHOD FOR PRODUCING GRAY CAST IRON WHICH COMPRISES ESTABLISHING A GRAY CAST IRON BATH CONTAINING ABOUT 3.4% TO ABOUT 4% CARBON ABOUT 0.1% TO ABOUT 0.4% MANGANESE, ABOUT 0.03% TO ABOUT 0.1% SULFUR, ABOUT 0.02% TO ABOUT 0.12% PHOSPHORUS, AT LEAST ABOUT 1.25% SILICON AND AT LEAST ABOUT 85% IRON, ADDING TO SAID BATH ABOUT 0.8% TO ABOUT 3% OF AN AGENT CONTAINING ABOUT 25% TO ABOUT 3% SILICON, ABOUT 14% TO ABOUT 20% MAGNESIUM, UP TO ABOUT 12% IRON, UP TO ABOUT 1% CALCIUM AND THE BALANCE ESSENTIALLY NICKEL TO DESULFURIZE THE METAL OF SAID BATH BELOW ABOUT 0.02% SULFUR AND TO INCORPORATE AT LEAST A SMALL BUT EFFECTIVE AMOUNT OF MAGNESIUM IN SAID METAL AND TO PROVIDE IN SAID METAL AN IMPROVED GRAPHITIZING PROPENSITY, AND CASTING SAID MAGNESIUM-CONTAINING METAL FROM SAID BATH TO OBTAIN GRAY IRON CASTINGS CONTAINING A SMALL BUT EFFECTIVE AMOUNT OF MAGNESIUM AND CONTAINING GRAPHITE IN COMPACTED FORM, WHEREBY SMALL SUBSTANTIALLY CONSTANT ADDITIONS OF SAID AGENT UNDER SIMILAR CONDITIONS PROVIDE PREDETERMINED RETAINED MAGNESIUM CONTENTS IN SAID CASTINGS INDEPENDENT OF VARIATIONS IN THE MAGNESIUM CONTENT OF SAID AGENT WITHIN THE AFORESAID MAGNESIUM RANGE.