Method and apparatus for heat treating low carbon steel

Claim 1

A METHOD OF QUENCHING A TUBULAR STEEL WORKPIECE HAVING A NON-UNIFORM CRYSTALLOGRAPHIC STRUCTURE AND CONTAINING UP TO 0.25% BY WEIGHT OF CARBON AND UP TO ABOUT 1% BY WEIGHT OF MANGANESE AND THE BALANCE IRON, COMPRISING THE STEPS OF HEATING SAID WORKPIECE TO A TEMPERATURE ABOVE 1550*F., AND SIMULTANEOUSLY SUBJECTING BOTH THE INTERNAL AND EXTERNAL SURFACES OF SAID WORKPIECE TO A PLURALITY OF PESSURIZED, ROD-LIKE, CONTINUOUS STREAMS OF A QUENCHING FLUID IN SUFFICIENT QUANTITY TO LOWER THE TEMPERATURE THROUGHOUT SAID WORKPIECE FROM 1550*F. TO A TEMPERATURE BELOW 700*F. IN LESS THAN 0.5 SECOND WHEREBY A STEEL WORKPIECE HAVING A UNIFORM MARTENSITIC CRYSTALLOGRAPHIC STRUCTURE THROUGHOUT THE THICKNESS THEREOF IS OBTAINED.