Method of aging iron-base austenitic alloys

Claim 1

IN THE PROCESS OF PRODUCING A PRECIPITATION HARDENED MEMBER FROM AN IRON BASE AUSTENTIC ALLOY CONTAINING FROM 1.30% TO 3.5% BY WEIGHT OF SOLUBLE TITANIUM AS A PRECIPITATION HARDENING COMPONENT, THE STEPS COMPRISING (1) SOLUTION TREATING THE ALLOY MEMBER AT A TEMPERATURE ABOVE 1700*F., (2) RAPIDLY COOLING THE ALLOY MEMBER TO A TEMPERATURE BELOW 1250*F., (3) REHEATING THE COOLED MEMBER TO A FIRST AGING TEMPERATURE OF FROM 1100*F. TO 1250*F. AND PREFERABLY BETWEEN 1100*F. AND 1200*F. FOR ALLOYS HAVING LESS THAN 1.4% OF SOLUBLE TITANIUM, AND MAINTAINING THE MEMBER IN THIS TEMPERAATURE RANGE FOR A PERIOD OF TIME OF FROM 2 TO 50 HOURS SUFFICIENT TO CAUSE NUCLEATION OF THE PRECIPITATION HARDENING COMPONENTS WHEREBY THE HARDNESS OF THE ALLOY INCREASES FROM 30 TO 125 POINTS BY THE DIAMOND PYRAMID HARDNESS TEST, (4) THEN HEATING THE ALLOYD MEMBER OVER A PERIOD OF FROM 2 TO 32 HOURS TO INCREASE ITS TEMPERATURE SLOWLY TO A TEMPERATURE OF FROM ABOUAT 1300*F. TO 1450*F., AND PREFERABLY FROM 1.4% OF SOLUBLE TITANIUM, FOR ALLOYS HAVING LESS THAN 1.4% OF SOLUBLE TITANIUM AND MAINTAINING THE ALLOY MEMBER ON THIS RANGE UNTIL IT INCREASE IN HARDNESS AT LEAST 25 POINTS MORE THAN THE HARDNESS AFTER THE FIRST AGING TEMPERATURE.