A method for heat-treating steel, primarily strip-like or rod-like steel material, such as steel strip, steel sheet, steel rod or steel wire which have been rolled and heated in an oven or furnace to a surface temperature above about 900 DEG C and thereafter cooled and optionally treated in an electrolyte bath and/or acid bath. The invention is characterized in that the oven burners are fired with a liquid or a gaseous fuel which is burned with the aid of a gas that contains at least 85 % by volume oxygen and at most 10 % by volume nitrogen.