| 摘要 |
The two steel tubes (6) having a rectangular cross-section are connected to each other, with interposition of a layer of refractory insulating material (18), by means of bolts (7) which are welded to the mutually facing tube walls and consist of a steel which lends itself well to welding. On a rolling-in path (1), the two steel tubes (6) are moved, with a tool (8) located therebetween and fixedly clamping the bolts (7), in stages through the welding station (3) and are moved away from there again on a rolling-out path (2). At the welding station with bottom fixed electrode (5a) and top movable electrode (5b), fixed bonding in groups is carried out cyclically by resistance welding as the tubes are advanced in stages. The bolts (7), the length of which is initially somewhat too long, are thereby shortened to the desired dimension of the tube spacing. After removing the tool (8), the interspace between the tubes is filled with insulating material. The composite profile is particularly suitable for producing fireproof door and window frames. <IMAGE>
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