Research on thickness precision control strategy of dual-phase steel based on property fluctuation
Dual-phase steel has the advantages of high strength and strong extension,but it is difficult to process in cold rolling.Due to the characteristics of small diameter rolls and strong rolling ability,18-high mill is gradually becoming the main mill for producing the strip hard to form.Compared with low carbon steel,the high strength of dual-phase steel makes it more challeng-ing in cold rolling processing,so it becomes the technical research point of 18-high mill operation.Influenced by the strong de-formation resistance of the material and the thickness difference fluctuation of the initial strip,the state of the rolling deformation zone is easy to fluctuate in the production process,which leads to the thickness difference fluctuation of the finished strip and af-fects the downstream industry and process.To solve these problems,the thickness fluctuation mechanism of the strip head and tail is analyzed,and its causes is traced.Based on the mill characteristic,structure characteristics and thickness control mecha-nism characteristics,the thickness control difficulties of dual-phase steel in 18-high mill are analyzed.The results show that a certain degree of phase transformation can also occur after the hot rolling coiling process of DP780 steel,which can be shown as the difference of bainite transformation degree at different target coiling temperatures,and can cause the mechanical properties of the cold rolling base material to fluctuate,and finally causes the thickness difference of the finished strip to fluctuate.Based on an 18-high single-stand rolling mill in a factory,the control characteristics and regulatory effectiveness of FF-AGC,FB-AGC,MF-AGC and BISRA-AGC are analyzed,the thickness difference combination control strategy of"FF+FB+Bisra"and the strip head thickness fluctuation control method using sine signal for interference control are proposed.The practical production show that this method can control the incoming material with thickness difference of up to 40 μm to the thickness difference of±10 μm,and achieve accurate control of the thickness difference of the full length,significantly improve the thickness pass rate of the finished strip,effectively improve the thickness control problem in the production of dual-phase steel in the 18-high mill,and provide a new idea and method for the production of high strength steel.
dual-phase steel18-high millthickness difference fluctuationmechanical properties fluctuationcombination control strategy
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