Abstract: A furnace wherein a device for supporting a metal strip in its constrained motion during the heat treatment comprises a pair of parallel drums arranged in a thermo-insulated cell with a possible reversed rotation in the opposite directions and adopted for an alternate bifilar coiling of the metal strip and uncoiling thereof. In addition said device is provided for a pair of guide rolls pivoted with a possible motion parallel to the plane of the rotation axis of the drums. One of said rolls is installed in the thermoinsulated cell at the strip inlet side and used for inserting the metal strip into the drums before coiling it meanwhile another arranged at the strip outlet side serves for discharging said sheet metal strip from the drums upon finishing the unwinding of the coil. This furnace provides a long soaking of the metal strip having a comparatively high capacity at a continuous motion of the metal strip during its heat treatment.