Method and apparatus for flame hardening of rails and the like

Claim 1

IN THE METHOD OF SURFACE-HARDENING A STEEL OBJECT BY APPLYING A HARDENING FLAME SUCCESSIVELY TO ADJOINING LIMITED AREAS OF A FACE TO BE HARDENED, SAID FLAME HAVING A HIGH INTENSITY SUCH AS TO HEAT THIN SURFACE ZONES BENEATH SAID LIMITED AREAS TO BE ABOVE THE CRITICAL SOLUTION TEMPERATURE OF THE STEEL AND IMMEDIATELY AFTERWARDS QUENCHING SAID HEATED ZONES BY SIMULTANEOUSLY APPLYING A JET OF COOLANT THAT IS OFFSET FROM SAID HARDENING FLAME SUCCESSIVELY ONLY TO SAID ADJOINING AREAS, THE IMPROVEMENT WHICH COMPRISES APPLYING AN AUXILIARY FLAME SIMULTANEOUSLY WITH SAD HARDENING FLAME SUCCESSIVELY TO ADJOINING LIMITED AREAS OF A FACE OF SAID OBJECT OTHER THAN THE SAID FACE TO BE HARDENED, SAID LIMITED AREAS BEING SITUATED IN THE PLANE THAT INCLUDES SAID HARDENING FLAME AND IS NORMAL TO SAID LAST-MENTIONED FACE, THEREBY CAUSING HEAT TO FLOW FROM THE SAID OTHER FACE THROUGH THE BODY OF THE STEEL OBJECT TO SAID SURFACE ZONES TO TEMPER THE METAL PROGRESSIVELY THROUGHOUT SUB-SURFACE ZONES ADJOINING SAID SURFACE ZONES, SAID AUXILIARY FLAME HAVING AN INTENSITY SUCH AS TO HEAT THE STEEL IN SUB-SURFACE ZONES TO A TEMPERATURE CLOSE TO BUT NOT ABOVE THE CRITICAL SOLUTION TEMPERATURE THEREOF.