Method of producing ultrafine grained steel

Claim 1

A METHOD OF PRODUCING ULTRFINE GRAIN SIZE IN STEEL WHICH IS PREDOMINATELY FERRITIC RATHER THAN AUSTENITIC AT ROOM TEMPERATURE, BECOMES COMPLETELY AUSTENITIC ON HEATING TO SUITABLE ELEVATED TEMPERATURE AND THEREAFTER BECOMES FERRITIC ON COOLING TO ROOM TEMPERATURE COMPRISING CYCLICALLY TREATING SUCH STEEL BY HEATING IT AT LEAST TWICE TO ABOVE ITS AC1 TEMPERATURE BUT BELOW THE TEMPERATURE AT WHICH AUSTENITE GRAINS COARSEN RAPIDLY FOR JUST SUFFICIENT TIME TO TRANSFORM IT TO AN AUSTENITIC STRUCTURE AND THEN BEFORE ANY APPRECIABLE GRAIN GROWTH OCCURS QUICKLY COOLING IT TO TRANSFORM THE AUSTENITE IN ALL BUT THE LAST CYCLE TO A MICROSTRUCTURE OF THE CLASS CONSISTING OF MARTENSITE, BAINITE OR MIXTURES THEREOF AND IN THE LAST CYCLE COOLING AT A RATE WHICH WILL PRODUCE THE DESIRED MICROSTRUCTURE WHEREBY AN AUSTENITE GRAIN SIZE FINER THAN ASTM #10 IS PRODUCED THEREIN.

Claim 2

A METHOD OF PRODUCING ULTRFINE GRAIN SIZE IN STEEL WHICH IS PREDOMINATELY FERRITIC RATHER THAN AUSTENITIC AT ROOM TEMPERATURE, BECOMES COMPLETELY AUSTENITIC ON HEATING TO SUITABLE ELEVATED TEMPERATURE AND THEREAFTER BECOMES FERRITIC ON COOLING TO ROOM TEMPERATURE COMPRISING CYCLICALLY TREATING SUCH STEEL BY HEATING IT AT LEAST TWICE TO ABOVE ITS AC1 TEMPERATURE BUT BELOW THE TEMPERATURE AT WHICH AUSTENITE GRAINS COARSEN RAPIDLY FOR JUST SUFFICIENT TIME TO TRANSFORM IT TO AN AUSTENITIC STRUCTURE AND THEN BEFORE ANY APPRECIABLE GRAIN GROWTH OCCURS QUICKLY COOLING IT TO TRANSFORM THE AUSTENITE IN ALL BUT THE LAST CYCLE TO A MICROSTRUCTURE OF THE CLASS CONSISTING OF MARTENSITE, BAINITE OR MIXTURES THEREOF AND IN THE LAST CYCLE COOLING AT A RATE WHICH WILL PRODUCE THE DESIRED MICROSTRUCTURE WHEREBY AN AUSTENITE GRAIN SIZE FINER THAN ASTM #10 IS PRODUCED THEREIN.