Abstract: A rotary drum for treating materials comprises a drum shell having a generally tubular configuration wall and one or more unitary material treating members forming a portion of the wall. In a preferred embodiment, the drum shell comprises a plurality of ring-shaped sections mechanically joined together in axial alignment wherein at least one of the sections has a unitary material treating member forming a portion of the section wall. In typical applications the treating members are cast steel members and the remaining portions of the drum shell are predominantly plate steel.The advantages of this drum include easier fabrication with a reduction in the extent of welding, avoidance of welding in inaccessible locations, elimination of abrupt changes in thickness and, in operation, a reduction of unwanted shearing stresses.