Research And Development Of Continuous Annealing Simulator For Cold Rolled Strip Steel

The microstructures and properties of high grade cold rolled products are determined by continuous annealing process. Continuous annealing which determines the mechanical properties of the final products is an important technology of cold rolled strip steel. A convenient, flexible, and accurate development device is in urgent need for the development of annealing technologies and products.A project of "research and development of continuous annealing simulator for cold rolled strip steel" is proposed based on the project of "research and development of continuous annealing simulator for cold rolled strip steel" which is supported by National Natural Science Foundation of China, the contract of "research and development of bright annealing simulator" between Northeast University and Stainless Steel Branch of Baosteel Group Corporation Limited, the contract of "research and development of experimental equipments of pilot test laboratory of TISCO technology center" between Northeast University and TISCO technology center.The continuous annealing simulator for cold rolled strip steel uses small specimens to simulate a series of technological processes of continues annealing of cold rolled strip steel, for example: tension, heating, cooling and protective atmosphere. The quantitative relationships between the annealing technology and the microstructure and properties of tested steels can be obtained after the experiment.The research and development works include the design of function structure, research and development of control system, development of temperature fuzzy expert control system, research and development of the safety control strategy for hydrogen utilization, preliminary application of the simulator, etc. After plenty of hard works the first continuous annealing simulator for cold rolled strip steel which had therefore been developed successfully has been used for about three years in Stainless Steel Branch of Baosteel Group Corporation Limited, and plays an important role there. This simulator which fills a domestic gap has important significance to the research and development of cold rolled products and annealing technologies. It also improves the international competition in the related fields.Main contents and innovative achievements of this dissertation are as follows:(1) The idea of single work position is proposed after a sufficient study about the continuous annealing simulators of home and abroad. It abandons the method of moving the sample through different work positions but uses just one work position to simulate the heating, soaking, slow cooling, fast cooling and over aging processes of annealing. The idea of different work positions just is the same as the actual annealing line about the mechanical structure and working mode, but it doesn't simulates the continuous annealing process well and makes the simulator's structure complicated. As a result, simulator's functions are not comprehensive and the similarities between experiments and the real production are decreased.(2) The function structure of continuous annealing simulator for cold rolled strip steel was designed according to the design principles, design indexes and multifunctional requirements. The function parts include mechanical body of simulator, heating system, cooling system, tension system, gas and water distribution system, gas analysis system, vacuum and exhaust system, control system. The design of function structure embodies the concept of modularization and integration and the function parts supplement each other well. So handling and maintenance are very convenient. The safety function of hydrogen utilization is also considered and implemented.(3) Cooling technology is the key technology of continuous annealing line. Research and development of cooling system is the key topic of this dissertation. A combined cooling device which owned a patent of invention can simulates the cooling means of gas jet cooling (GJC), water quenching (WQ) and spray cooling was designed and developed successfully. By flexible arrangement of the cooling devices uniform cooling can be achieved. The cooling gases are composed of hydrogen and nitrogen. Full-hydrogen cooling can be implemented.(4) According to the functional demands of simulator's control system, the configuration of hardware and network structure was designed and implemented, including main control system, hydrogen safety alarming control system, arrangement plan of field sensors and actuators. The hardware of basic automation control system adopts the S7-400 PLC+FM458 configuration structure. S7-400 CPU communicates with ET200M and transmission system by PROFIBUS-DP net, and communicates with HMI by Industrial Ethernet. The hardware of hydrogen safety alarming control system adopts the SIEMENS LOGO PLC.(5) The software of control system is composed of PLC system software and HMI system software. PLC system software includes logical control system, furnace pressure control system, safety control strategy of hydrogen utilization, tension control system, temperature fuzzy expert control system, gas and water distribution system. HMI system provides the interface for operators to set experiment parameters, monitor experiment status and obtain experiment dates.(6) Because of some disadvantages of the simulator's temperature control system, for example: nonlinearity, time-varying, variable structure, multi-level, large time delays etc, the control effects were not ideal and can't meet the control performance indexes. We found that the control strategy which was composed of sectional PID control and flying gauge change (FGC) control can get a good performance. A temperature fuzzy expert control system was built after introducing the structure and theoretical basis of fuzzy expert system and combined with some expert control strategies. The control performance was good and the overshoot was small.(7) Analyzing the working principle of continuous annealing simulator and physical characteristics of hydrogen, a safety control strategy of hydrogen utilization was proposed including the controls of hermetical performance of furnace, gas content in furnace, alarm of hydrogen detection in plant, safety interlocking and emergency measures, safety operation specification, etc.