Abstract: Spaced apart packs of closely spaced steel or other metallic rods, tubes or other elongate articles are annealed or otherwise heat treated by advancing them step by step by a walking beam mechanism through a chamber having a series of independently temperature controlled zones along the path of travel, the articles being disposed horizontally and transversely of the path of travel. The atmosphere within each zone is recirculated therein independently of the recirculation of atmosphere within adjacent zones and without substantial mixing of the atmosphere within adjacent zones.