Abstract
In the joint project PIREF, the metal forming group of the University of Duisburg-Essen has collaborated with the University of Applied Sciences Ruhr-West Mülheim (Ruhr), the University of Siegen, EMG Automation GmbH and SMS group GmbH to develop sensors, for an online measurement of material velocity and cross section as well as control models for the rolling process of wire rod and bars. The University of Duisburg-Essen provided a metal forming process model for the rolling process to assess the influencing parameters on the rolled section precision. A technique was found to segregate height- from width- influencing parameters from a measured cross-sectional area and actual roll gap. With this measuring technology and with help of the process model, rules for control of the rolling process to achieve close tolerances were obtained. The modelling was accompanied by rolling trials on a laboratory rolling mill at the University of Duisburg-Essen, where a typical Round-OvalRound pass sequence was used for validation of the rolling model concerning lateral spread, inlet and outlet velocity as well as rolling force and torque calculation. The present paper shows how the material flow and the distribution of the velocity in the roll gap can be described. In subsequent rolling of bar and rod in a continuous rolling mill the dimensions can be influenced by application of longitudinal stresses and screwdown. The application of stress can be achieved by an inter-stand velocity mismatch. With the developed models the necessary velocity mismatch can be calculated.
Highlights
In hot rolling of wire rod, bars and other long products in continuous rolling mills, the sectional deviations along a rolled material strand are affected by temperature and size [1]
It is well known from rolling theory, that roll force and torque are affected by tension stresses, but there is another direct influence of the interstand tensions on the spreading behavior of the rolling process
In the research project PIREF, we were able to develop a model for hot rolling of full sections which can be used in a control model for the rolling process
Summary
In hot rolling of wire rod, bars and other long products in continuous rolling mills, the sectional deviations along a rolled material strand are affected by temperature and size [1]. Other important influences are interstand tension stresses which arise in the rolled material between the stand positions It is well known from rolling theory, that roll force and torque are affected by tension stresses, but there is another direct influence of the interstand tensions on the spreading behavior of the rolling process. The whole influence chain described above is affected further by acting interstand tensions These effects lead to the circumstance that a control of the rolling process for long products is much more complicated than that of the flat rolling process since the lateral spread must be considered in the analysis. To enable process control during rolling, cross-section sensors developed by the HRW were used (so-called QFM sensors) which are suited for an inline use during the rolling process. With help of these sensors, the cross section of the rolled strand could be measured during the rolling process at key positions in the rolling mill layout
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