Research On Rolling Theory And Control Strategy For Longitudinally Profiled Flat Steel

Longitudinally profiled flat steel is a kind of saving type steel products which has been applied oversea, but rolling technologies of longitudinally profiled flat steel was hardly studied in domestic rolling line. Rolling theory and control strategy of longitudinally profiled flat steel were studied in this dissertation. Rolling theory of longitudinally profiled flat steel was expounded and rolling dimension prediction formulas were developed, and multiple-point setup method and thickness control in the rolling process were studied. Experiment and application were done in mill by the programs which were inset PLC and process control programs. Good control effect was obtained. The main works are as follows:(1) Basic rolling theory of longitudinally profiled flat steel was expounded. According to comparison between conventional rolling and longitudinally profiled flat steel rolling, metal flow law and metal deformation were analyzed, and rolling characters were given. Longitudinally profiled flat steel rolling process is classified as thickening rolling and thinning rolling. The radius angel both link line between contact point and working roller center and link line of two working roller centers equals to the taper slop angle. Beginning with deforming and kinematics and mechanics condition, rolling parameters such as Biting condition, steady rolling condition, neutral angle, contact arc and forward slip were analyzed and their formulas were deduced. Variation of rolling parameters is nonlinear, and the bigger is the slope of taper section, the more obvious is non-linearity of rolling parameters.(2) Dimension forecasting of longitudinally profiled flat steel was done. Cause and influencing factors of spread for longitudinally profiled flat steel were analyzed. By semi-theory and semi-empirical formulas and introducing spread volume coefficient, micro-element was selected and analyzed along longitudinal direction in longitudinally profiled flat steel. Width function of longitudinally profiled flat steel was deduced by volume constancy. Longitudinally profiled flat steel was divided into multiple segments and total length was calculated by length of each segment.(3) The method of multiple-point dynamic setup was presented according to the varying laws of thickness and gap in the longitudinally profiled flat steel rolling process. The thickness of taper plate is linear, but gap variation is nonlinear. The traditional signal-point static setup is not suitable for longitudinally profiled flat steel, so multiple-point dynamic setup is necessary. Because longitudinally profiled flat steel is usually composed of the taper segments and common segments, rolling setup points are divided into two classes:taper segment setup points and common segment setup points. Mechanism of multiple-point setup was analyzed. Intermediate setup point is solved by penalty function method, and multiple-point dynamic setup assures that setup gap approaches target gap.(4) Decision method of setup points was respectively discussed in plan view pattern control and variable width plate rolling and longitudinally profiled plate rolling. Rolling parameters formulas of setup points such as rolling force and thickness and gap etc. were deduced. Dynamic adjusting amount of gap between nearby setup points was considered as linear variation, and was calculated by linear equation. Rolling force and rolling moment were checked by equipment ability. Matching of screw speed and rolling speed and effective travel of cylinder should be considered before longitudinally profiled flat steel was rolled.(5) Precise micro-tracking along length and dynamic thickness control strategy in the longitudinally profiled flat steel rolling process were built. Based on discrete disposal of the length of longitudinally profiled flat steel, longitudinal micro-track model was established by Newton's iteration method. The rules of gap variation and the characters of gauge control for taper plate in the longitudinally profiled flat steel rolling process were analyzed by use of P-H drawing. The variation of thickness is divided into passive thickness variation which is caused by external disturbance and active thickness variation which is necessary in taper segment. According to actual rolling force and target thickness, passive gap adjustiment was calculated by ABS-AGC. Multiple target gaps control was done by hydraulic cylinder control system in order to control dynamic varying thickness. Macro-tracking based on process control in plate mill line was analyzed. Micro-tracking and dynamic thickness control stragety were implemented by use of SIMATIC TDC or FM458 in plate rolling line.(6) Experiment and application of longitudinally profiled flat steel were done. Programs of dynamic multiple-point setup and dynamic adjustment of gap were complied in the four-high pilot rolling mill. Different kinds of longitudinally profiled flat steel were rolled in mill under different rolling condition, including single direction and single pass, and two-direction and single pass, and single direction and several passes and two-direction and several passes. Gap and rolling force were recorded, and delivery thickness was measured by micrometer calipers. Multiple-point setup model and control strategy can meet rolling requirement of longitudinally profiled flat steel by comparison between setup data and actual data. The forming MAS rolling process of plan view pattern control is applied in domestic heavy and medium plate rolling line. Rectangle figure of pate with forming MAS rolling is obtained. Exponential curve is adopted in varying thickness compensation at the head of plate, and compensation effect is obvious.Basic theory and control strategy built in the dissertation are important in the longitudinally profiled flat steel rolling process, and rolling experiment of longitudinally profiled flat steel supplies experimental basis and data reference for industry application. Good control effect and economic benefit are obtained in the MAS rolling process and varying thickness compensation control at head of plate.