There are 40 good practices in draft scheduling to be integrated into the plate mill Level 2 model, for the purpose of improving rolled plate steel properties, reported in a recent internal writing/proposal from Metal Pass . Quite a portion of the practices are to apply high draft in certain passes or certain production stages, accompanied by measures to guarantee the plate shape.
Two factors limit the application of the high draft. The first is the mill capacity, and the second is the rolled steel shape. A small draft in the finishing stage is helpful for the good shape.
(2) Integration of Metallurgical Guideline in the Temperature Control
Temperature control involves very complicated interaction of temperature with various rolling processes and mill equipment hardware. A simplified metallurgical model on grain refinement or rolled steel properties can be integrated into the Level 2 logics of the process or hardware, in order to effectively control the temperature and the rolled steel properties. Typical example is the application of Frits. There are quite complicated logics in operating Frits for temperature control. Integration of metallurgical guideline to the Frits temperature control can effectively improve the rolled steel properties.
(3) Improvement of both Property and Shape
Increasing model prediction accuracy can improve both property and shape. Suppose there is no prediction error in the Level 2 model, then even with a high draft, there should not be any draft variation over the width. It is the Level 2 model prediction error that causes the difference in the draft over the width. This also applies to the deformation along the plate length. With high-quality Level 2 model, relatively high draft in the finishing passes wonít cause shape problem. The benefit is, that the rolled steel properties would be improved.
(4) Creation of Link with Roll Bending System
Many mills have roll bending equipment. Some manufacturers own such a system but still do not have sufficient skill to use it. This often happens in Asia (China, India, etc.). If the Level 2 has an interface for the bending force of the roll bending system (a two-way link), then the Level 2 model can interact with the roll bending system in such a manner that the roll bending system compensates the roll deflection, with reference to the roll separating force accurately predicted by the Level 2 model. In this case, even if a high draft is applied in the finishing passes, the shape of the finish product may still be guaranteed. Of cause, most Level 2 systems donít have such an interface. Such an interface may be added through Level 2 improvement.
(5) Metallurgical Integration into Level 2 Model - Offline
Metallurgical models, such as those for recrystallization, microstructure and steel properties, usually involves great amount of data processing; besides, a portion of the models are still not yet mature. It is generally not a good practice to have excessive model calculation inside the online Level 2 code. Instead, most data should be designed before-hand in offline basis, and integrated into the Level 2 through database. Since the development in physical metallurgy is very dynamic, new results should be added into the database continuously without the need to reprogram the Level 2 system. In order to achieve high accuracy, data are provided for each temperature region in each of the several thousand model grades. Modern database management system (DBMS) is capable of querying great amount of data in very short time, for example, to query from millions of records in a tiny friction of second. In this way, model consideration is detailed, but with very high speed.