Abstract: Mandrel rod (1) for pipe rolling mills, in which hollow billet (5) is rolled on mandrel rod (1), consists of two pipes (2, 3) lying inside one another. Annular gap (4) between pipes (2, 3) is filled with a thermosetting plastic, whose coefficient of expansion is selected large enough so that the thermosetting plastic completely fills annular gap (4), even with temperature differences, between pipes (2, 3).

Abstract: The invention relates to a housing for a rolling mill for producing axially bored cylindrical blooms from square bars, the housing being of the kind substantially comprising a pair of cogging rollers having round grooves and associated bearing chocks mounted in the housing, an inlet guide for bearing a square bar to be rolled, an outlet guide for the board, rolled cylindrical bloom, and means for adjustably positioning the inlet guide relative to the rolling axis.

Abstract: In the rolling of seamless tubes using a mandrel which is inserted in a hollow bloom as it is advanced through a rolling mill, the cooling of the mandrel after the tube rolling stage is effected, for example by passing the mandrel through a cooling bath, as the mandrel is returned to a ready position upstream of the mill along a return path which is at one side of the rolling axis, so that while this mandrel is being cooled a further rolling operation can be carried out using another mandrel, the mandrels being moved in a closed cycle of successive rolling and cooling stages.