Abstract A method of hardening hypereutectoid steels having less than about 10 percent total alloy content is described which results in a structure with an ultra-fine grain size (finer than ASTM No. 10) and a natural dispersion of very small excess carbides. The process includes high temperature solid solution of the carbide phase present in the material, controlled cooling through a selected area of the time temperature-transformation for the material to form pearlite (a ferrite and carbide lamellar structure) and cementite, reheating to austenitize the material, and finally, quenching to produce a structure with an ultrafine grain and a natural dispersion of very small excess carbides that results in an improvement of fatigue life and an increase in compressive yield strength.
A METHOD FOR PRODUCING HARDENED HYPRECUTECTOID STEELS OF LESS THAN ABOUT 10 PERCENT TOTAL ALLOY RESULTING IN A STRUCTURE WITH AN ULTRA-FINE GRAIN SIZE FROM MICROCRACKS, AND VERY SMALL WELL DISPERSED EXCESS CARBIDES COMPRISING THE STEPS OF: HEATING THE MATERIAL TO A TEMPERATURE NOT EXCEEDING THE SOLIDUS FOR A TIME SUFFICIENT TO DISSOLVE THE CARBIDES PRESENT IN THE INITIAL MICROSTRUCTURE, QUENCHING QUICKLY INTO A SUITABLE LIQUID QUENCH MEDIUM TO THE APPROXIMATE RANGE OF 900* TO 1333*F TO PRODUCE PEARLITE, WHEN THE PEARLITE TRANSFORMATION IS COMPLETE, COOLING TO A SUITABLE TEMPERATURE FOR MECHANICAL DEFORMATION, AND MECHANICALLY DEFORMING THE MATERIAL THEN. RAPIDLY HEATING THROUGH THE A 13 AND ACN TEMPERATURE RANGE OF ITS EQUILIBRIUM DIAGRAM TO THE AUSTENITIZING TEMPERATURE FOR THE MATERIAL FOR A CONTROLLED TIME ONLY SUFFICIENT TO CONVERT THE CABIDE LAMELLAE WITHIN THE PEARLITE INTO VERY SMALL EXCESS CARBIDES AND TRANSFORM THE FERRITE TO AUSTENITE, AND, QUENCHING TO HARDEN THE STEEL.
Claim 2
Independent Claim
151 words
A METHOD FOR PRODUCING HARDENED HYPRECUTECTOID STEELS OF LESS THAN ABOUT 10 PERCENT TOTAL ALLOY RESULTING IN A STRUCTURE WITH AN ULTRA-FINE GRAIN SIZE FROM MICROCRACKS, AND VERY SMALL WELL DISPERSED EXCESS CARBIDES COMPRISING THE STEPS OF: HEATING THE MATERIAL TO A TEMPERATURE NOT EXCEEDING THE SOLIDUS FOR A TIME SUFFICIENT TO DISSOLVE THE CARBIDES PRESENT IN THE INITIAL MICROSTRUCTURE, QUENCHING QUICKLY INTO A SUITABLE LIQUID QUENCH MEDIUM TO THE APPROXIMATE RANGE OF 900* TO 1333*F TO PRODUCE PEARLITE, WHEN THE PEARLITE TRANSFORMATION IS COMPLETE, COOLING TO A SUITABLE TEMPERATURE FOR MECHANICAL DEFORMATION, AND MECHANICALLY DEFORMING THE MATERIAL THEN. RAPIDLY HEATING THROUGH THE A 13 AND ACN TEMPERATURE RANGE OF ITS EQUILIBRIUM DIAGRAM TO THE AUSTENITIZING TEMPERATURE FOR THE MATERIAL FOR A CONTROLLED TIME ONLY SUFFICIENT TO CONVERT THE CABIDE LAMELLAE WITHIN THE PEARLITE INTO VERY SMALL EXCESS CARBIDES AND TRANSFORM THE FERRITE TO AUSTENITE, AND, QUENCHING TO HARDEN THE STEEL.