A converter vessel is coaxially surrounded by a trunnion ring carried by a pair of trunnions for rotary or tilting motion about a horizontal axis. In order to permit rotation of the vessel relative to the trunnion ring about the vessel axis at right angles with the noted horizontal axis, two annular rows of support elements such as rollers are mounted on the trunnion ring and engaged with respective annular tires on the vessel so as to bear its radial load. Two other annular rows of rollers or like support elements are also mounted on the trunnion ring and engaged with the respective tires so as to bear the axial vessel load. Several identical drive mechanisms are compactly mounted within the trunnion ring for revolving the vessel through a gear drive, friction drive, or chain drive.