The rolling radius determining method for longitudial tube rolling

Abstract

A generalized method for determining the rolling radius was developed. It based on analysis of the real form of the neutral line in the deformation zone.The assumption that the neutral plane is parallel to the rolling gauge plane of sym-metry is mostly applied in analytical determination of the conventional rolling radius at longitudinal rolling in round gauges (including rolling reduction of pipes). According to that assumption, the horizontal projection of the conventional neutral line to the perpendbcular plane is a straight line parallel to the axis of rolling. The true shape of border between the lead and lag zones (real neutral line) represents a spatial curve not parallel to the symmetry plane. And it`s horizontal projection onto the perpendbcular plane is flat curve. The equation determining its shape on this plane can be determined by considering the condition the balance of the metal inside the deformation zone under the action of applied forces. The rolling radius calculated using that equation is called the real rolling radius. Presented in this study calculations show no significant influence of the friction factor f on the ratio within f values range 0.25…0.5. Such range meets the real conditions at longitudinal pipe rolling. External axial force directed forwards to rolling direction also don`t change the ratio significantly. Over against, the backward directed external force and greater rolls diameter lead to alignment of conventional and real rolling radiuses. Increase of the diameter reduction as well as an increasing of the relative wide of the groove elevates the ratio. Same effect provides the higher wall thickness in the entrance to deformation zone. Empiric equation for ratio determining at mostly used conditions of longitudinal pipe rolling obtained in this study allows to correct rolls drive velocity to provide best stress conditions inside the deformation zone.