Long Products Rolling Technologies
In promoting product quality for high-end automotive applications, an in-line surface inspection system was introduced into a 32-stand wire rod rolling train. Measured continuous improvement has been accomplished by way of a managerial plan, which includes the implementation of process control by adopting the data generated from the in-line surface inspection system, the best practices in rolling operations and the enforcement rules. This article documents the plan and its execution, as well as the results of surface quality–related technical and economical metrics over a period of three years.
In a research project, the Metal Forming Group of the University of Duisburg-Essen (UDE) collaborated with academic and industrial partners in Germany to develop sensors for an on-line measurement of material velocity and cross-section as well as control models for the rolling process of wire rod and bars. UDE provided a process model to assess the influencing parameters on the section precision. A technique was found to segregate height- from width-influencing parameters from measured cross-sectional area and actual roll gap. With this technology, rules for control of the rolling process to achieve close tolerances were obtained. Additionally, rolling trials on a laboratory rolling mill were carried out using a typical round-oval-round pass sequence for validation of the model. This article shows how a control of section tolerances is possible using the developed sensors and models.
A set of integrated mathematical models for predicting microstructure evolution during hot rolling has been developed through laboratory research work. It consists of several models which include static and dynamic recrystallization mechanisms. Generally, dynamic recrystallization falls under the continuous hot rolling process. The model has been applied to compute the changes in grain at individual passes during hot rolling. The initial grain size with different heating temperatures and dwell times was computed using constitutive equation, and grain size at the individual passes was calculated using different pass schedules at individual passes. The model has been validated by comparing predicted austenite grain size with measurements made on quenched samples taken from end-cut shears. Different grades and sizes have been validated in this model. The predicted results agree well with measured values in samples.
The demands on heat treatment plants for tubes/bars with regard to green steel production with constant quality requirements are increasing. The heating system is becoming increasingly important. But also the role in setting the exact atmosphere control, which determines the material surface, is becoming more and more significant. This article gives an overview of the state of the art, especially of the different heating systems. In addition, the plants presented can also fully cover AMS2750/CQI-9 auditing with a specially developed all-in-one software solution.