Evaluation of the effect of axial adjustment on the strength of the rolling mill mandrels

Modern tube mills are usually equipped with mandrel mounted longitudinal mills such as PQF (Premium Finishing) and FQM (Thin Roll Mill) mills. The used mandrel, as a rule, reaches 10-12 m and is made of special grades of steel, resistant to abrasion, increased strength. During operation, the mandrel, when filling the deformation zone, passes through all the stands and is fixed at a certain distance. When rolling pipes, great attention is paid to setting up the mill both in terms of technological modes and in terms of the location of the stands relative to the rolling axis. During the operation of the mill, due to backlashes, vibrations and other negative factors, the axes of the stands can shift, which will lead to bending of the mandrel, increased tool wear, and accumulation of residual stresses in the mandrel. All this will create conditions for reducing the operational life of an expensive tool. In this regard, the article considers the effect of axial adjustment of PQF stands on the stress in the mandrel. In the course of the work, regression-significant equations of the influence of axial fit on the stress level in the mandrel were obtained.