STUDIES ON THE ROLLING OF SEAMLESS STEEL TUBE (II)

Measurements and Analyses of Several Loads in Plug Rolling

Abstract

Three principal components of loads in plug rolling of seamless steel tube, i.e. mandrel bar force, roll-force and roll-torque were measured by means of resistance wire strain gages. The measurements were made on Aetna plug rolling mill in Nippon Tokushu Steel Tube Co., Ltd. The electromagnetic-oscillograph records of mandrel bar force and roll-force indicated a gradual (nearly linear) decrease as a pierced billet proceeds through the groove (or caliber) of rolls, and those of roll-torque revealed a characteristic vibration of the driving system of the mill.
Above experimental results, especially (i) the response of the driving system of the mill to braking torque exerted by a tube entering into and passing through the groove of rolls, and (ii) the relation among the three components measured, were analysed. An elementary theory, on which the analysis of the three components was based, gave a linear relation between (roll-force)×(radius of roll) and roll-torque, and this agreed well with the experimental observations; the coefficient of friction between tube and rolls evaluated from experimental data was 0.07-0.12 at rolling temperature (about 1000°C) of the tubes. Also, an estimation of pressure between tube and rolls was attempted.