Investigation of thermal state of long mandrels on three-roll rolling mill

Abstract

A technique was developed for the numerical analysis of the thermal state of long mandrels of a three-roll rolling mill using modern computer simulation software. The initial and boundary conditions were determined taking into account the peculiarities of rolling in a three-roll screw rolling mill on a long mandrel. The authors carried out a qualitative assessment of the thermal state of a long mandrel by means of visualized representation and established its significant inhomogeneity. Influence of the rolling temperature and diameter of the long mandrel were revealed. Small diameter mandrels are heated to higher temperatures (577 °C) with a significantly lower gradient between the axial zone and the surface. An increase in the mandrel diameter to 154 mm lowers the temperature of the outer surface to 530 °C and increases temperature gradient in the near-surface layers up to 18 °C/mm. So the temperature in the near-surface layers for a mandrel of 154 mm at a distance of 10 – 15 mm from the surface decreases from 530 °C to 315 °C. Features of the temperature field in the cross section were established taking into account thermal interaction of the sleeve with the mandrel in the zone of contact with hot metal and in gaps between the rolls. Temperature of the near-surface layers in the contact zone is 30 °C higher than in the gaps. Dependences of temperature of the cross-section characteristic points on the rolling time were determined, it has been established that in the first two seconds there is an intense growth according to the parabolic, and then according to the linear laws. Temperature of the central layers with a radius of 50 mm increases with a much lower intensity, by about 100 °С during the entire period of rolling, while during the same time, the near-surface layers are heated by 300 – 400 °С.