Method for cooling and spheroidizing steel rod

Abstract

Abstract SPHEROIDIZED STEEL ROD SUITABLE FOR COLD WORKING IS OBTAINED BY HOT ROLLING COOLING AND REHEATING STEEL ROD IN DIRECT SEQUENCE. COOLING THROUGH TRANSFORMATION IS DONE IMMEDIATELY AFTER HOT ROLLING IN ORDER TO INHIBIT THE FULL GROWTH OF THE SMALL AUSTENITE GRAINS WHICH RESULT FROM ROLLING, PRIOR TO TRANSFORMATION. THE COOLING THROUGH TRANSFORMATION IS RAPID ENOUGH TO FORM CONSTITUENTS SUCH AS FINE PEARLITE, BAINITE AND MARTENSITE IN SUBSTANTIAL AMOUNTS TO RENDER THE TRANSFORMED ROD TOO HARD OR BRITTLE FOR THE INTENDED COLD WORKING AND TO SUPRESS SUBSTANTIALLY THE DEVELOPMENT OF PROEUTECTOID FERRITE. DIRECTLY THEREAFTER, BEFORE SAID ROD HAS COOLED TO AMBIENT TEMPERATURE, THE ROD IS PASSED THROUGH A SPHEROIDIZATION FURNACE, WHILE THE ROD IS IN THE FORM OF OVERLAPPING NON-CONCENTRIC RINGS, TO HEAT THE ROD TO A TEMPERATURE OF ABOUT 1280*1330*F. (690-720*C.) AT LEAST UNTIL THE CEMENTITE IN THE MICROSTRUCTURE BEGINS TO COALESCE INTO SPHEROIDAL PARTICLES. IN ONE EMBODIMENT THE ROD IS THEN COOLED AND STORED FOR FURTHER TREATMENT. IN ANOTHER EMBODIMENT IT IS MAINTAINED AT THE TEMPERATURE OF TRETMENT UNTIL ENLARGEMENT OF THE SPHEROIDAL PARTICLES OCCURS. THE PROCESS IS GENERALLY APPLICABLE TO PLAIN CARBON AND ALLOY STEEL ROD WHICH, FOR ONE REASON OR ANOTHER, IS NOT SUITABLE WITHOUT SPHEROIDIZING FOR CERTAIN COLD-WORKING PROCEDURES, AND IT PROVIDES A NOVEL METHOD OF SPHEROIDIZING TO OBTAIN RAPIDLY A UNIFORMLY ANNEALED PRODUCT.

Inventors

• 👤 V Vitelli

Bibliographic Details