A device is described for heat-treating sheet metal strips (6) having at least one radiator pipe unit (1), which has three pipes located in a common axial plane parallel to the sheet-metal strip (6), namely one middle pipe (2) attachable to a burner and two outer pipes (3) connected at both ends to the middle pipe (2) via pipe elbows (4), and having a bearing pin (9), connected to the two pipe elbows (4) between the middle pipe (2) on one side and the two outer pipes (3) on the other side, on the side of the radiator pipe unit opposite to the burner. To be able to take the occurring thermal expansions in the area of the pipe elbows (4) into consideration, it is proposed that the bearing pin (9) be arranged on a bridge (10), which bridges a gusset (11) between the two pipe elbows (4), having two sections (12) which extend on both sides of the axis of the middle pipe (2) and are inclined at an acute angle to the axis of the middle pipe (2).