C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
C21D1/34—Methods of heating
C21D1/40—Direct resistance heating
B—PERFORMING OPERATIONS; TRANSPORTING
B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
B21B—ROLLING OF METAL
B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
B21B45/004—Heating the product
H—ELECTRICITY
H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
H05B3/00—Ohmic-resistance heating
H05B3/0004—Devices wherein the heating current flows through the material to be heated