Asymmetric hydrodynamic roll gap model and its experimental validation

Andreas Ettl,Stefan Fuchshumer,Kurt Etzelsdorfer,Andreas Steinboeck,Martin Müller,Andreas Kugi,Hannes Seyrkammer,Katharina Prinz

doi:10.1007/s00170-018-2634-1

Abstract

In tandem hot strip rolling mills, different friction between the rolls and the strip material on the upper and lower strip surface can occur due to asymmetric surface temperatures or different conditions of oil lubrication. To capture these effects, this paper presents a hydrodynamic roll gap model with asymmetric friction. Based on similarities between the rolled material and viscous fluids, fluid mechanics theory is used to derive this model. Due to the nature of this model, the influence of the rolling speed is inherently taken into account, which allows an accurate prediction of the rolling force and the forward slip. As an analytic solution for the hydrodynamic roll gap model is available, it is well suited for online applications in rolling plants. For validation of the proposed model, an experiment with asymmetric work roll roughness was performed. A specimen of steel strip with copper pins inserted was repeatedly rolled to visualize the material flow inside the roll gap for multiple passes. The resulting deformed copper pins were cut out of the strip and show good agreement with the deformation profiles calculated by the developed model.

Highlights

In the steel industry, the demand for higher product quality and production speed has steadily increased during the last 3 voestalpine Stahl GmbH, voestalpine-Straße 3, 4020 Linz, Austria decades
A copper pin is inserted into the steel strip in vertical direction and after a roll pass the strip is cut in longitudinal direction through the middle of the pin
As the model can be analytically solved, it is well suited for online applications in strip rolling

Summary

Introduction

The demand for higher product quality and production speed has steadily increased during the last 3 voestalpine Stahl GmbH, voestalpine-Straße 3, 4020 Linz, Austria decades. Modern model-based control concepts can make an essential contribution to meet this demand by improving the overall performance of the control loops in the rolling plant. The roll gap model is very important because an accurate prediction of the roll force or the forward slip is required for several applications, e.g., process planning, calculation and adjustment of nominal operating points, observers for non-measurable quantities, and advanced model-based control concepts (see, e.g., [1, 2]). In order to improve the prediction accuracy, it is essential to correctly capture the influence of various process parameters, such as rolling speed or friction between work rolls and material. Friction is of great interest as lubrication is often used in tandem rolling to reduce the rolling force, energy consumption, roll wear, and to increase the strip surface quality

Methods

Results

Conclusion