A furnace construction for the heat treating of metal materials and including a conveying apparatus that provides for step-bystep movement of the metal materials through the heat treating chamber of the furnace construction, the drive for the conveying apparatus comprising a walking beam assembly. Sintering of various kinds of materials including metal compacts may be accomplished by the furnace construction and since treatment of the materials at relatively high temperatures is necessary during the heat treating cycle, a special sealing structure is provided for preventing contamination of the high temperature zone during sintering of the materials and the cooling thereof after the sintering cycle.