Abstract: The heat treatment of a continuous band or sheet of metal as the same travels through a plurality of stages in a protective atmosphere, between conveying rollers, by applying direct-current electricity to the rollers for inclusion of the travelling sheet in the circuit therebetween. The charged rollers in the initial stage are spaced more widely from one another than those in the later stage, to compensate for the lower resistivity of the metal in the former, so that the Joule effect or I.sup.2 R factor in the stages are substantially equalized. The protective atmosphere of oxidizing, reducing or inert gases which encompasses the sheet, is confined in chambers of galvanized iron sheeting and the like, the walls of which are in close proximity to the travelling sheet, so that lesser amounts of reacting gases are necessary.

Abstract: The heat treatment of a continuous band or sheet of metal as the same travels through a plurality of stages in a protective atmosphere, between conveying rollers, by applying direct-current electricity to the rollers for inclusion of the travelling sheet in the circuit therebetween. The charged rollers in the initial stage are spaced more widely from one another than those in the later stage, to compensate for the lower resistivity of the metal in the former, so that the Joule effect of I.sup.2 R factor in the stages are substantially equalized. The protective atmosphere of oxidizing, reducing or inert gases which encompasses the sheet, is confined in chambers of galvanized iron sheeting and the like, the walls of which are in close proximity to the travelling sheet, so that lesser amounts of reacting gases are necessary.