Method of heat processing alloy steel to obtain maximum softness and uniformity

Abstract

Abstract A METHOD OF THERMALLY PROCESSING ULTRA HIGH STRENGTH STEEL TO OBTAIN MAXIMUM SOFTNESS AND UNIFORMITY TO INCREASE ITS RESPONSE TO MACHINING OR OTHER PROCESSING WITHOUT ADVERSELY AFFECTING ITS ABILITY TO RESPOND TO THE FINAL THERMAL TREATMENT REQUIRED TO MEET THE FINAL MECHANICAL PROPERTIES. THE STEEL IS SUBJECTED TO A DOUBLE THERMAL PROCESS IN WHICH THE STEEL IS INITIALLY GIVEN A THERMAL TREATMENT AT A TEMPERATURE ABOVE 1200*F. AND BELOW THE RECOGNIZED LOWER CRITICAL ON HEATING, COOLED TO BELOW THE MARTENSITIC FINISH TEMPERATURE, AND THEN REHEATED TO A TEMPERATURE IN THE RANGE OF 1250*F. TO 1350*F. DURING THE INITIAL TREATMENT THE STEEL IS MAINTAINED AT TEMPERATURE FOR A PERIOD OF TIME SUFFICIENT TO ALLOW SMALL AREAS OF THE STEEL TO TRANSFORM TO AUSTENITE AND CAUSE THE REMAINING CARBIDE TO SPHEROIDIZE AND UPON COOLING PRODUCES A MICROSTRUCTURE WHICH EXHIBITS A PARTIALLY SPHEROIDIZED STRUCTURE WITH SMALL AREAS OF FRESH MARTENSITE UNIFORMLY DISPERSED THROUGHOUT. THE SECOND THERMAL TREATMENT CAUSES THE FRESH MARTENSITE TO SPHEROIDIZE INTO CARBIDES TO PROVIDE A MICROSTRUCTURE AND LOW HARDNESS LEVEL WHICH IS MORE RESPONSIVE TO FURTHER PROCESSING, AS WELL AS IMPROVED UNIFORMITY IN HARDNESS THROUGHOUT THE PART AND FROM PARTTO-PART.

Inventors

• 👤 R Furgason

Bibliographic Details