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High-precision rolling and heat treatment process and equipment technology for thin strip steel

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  This paper introduces a high-precision rolling and heat treatment process and equipment technology of Bogang Steel. Based on the preliminary work in the advanced cold rolling direction, the paper continuously improves the control precision of high-precision cold-rolled shape control system and promotes its application. Research and popularization of edge thinning control technology; in advanced continuous annealing and coating technology, continuous direct flame impact rapid heating technology, non-oxidizing rapid cooling technology and hot-dip galvanizing quality control technology research and development, and carried out Research and application of warm rolling technology and equipment technology for casting and rolling strips.
 
  Thin strip high precision rolling
  And heat treatment process and equipment technology
  Foreword
  Advanced cold rolling, heat treatment and coating process and equipment technology are the key to producing high-end cold-rolled strip steel products. Since the approval of the center, the advanced cold rolling direction has continuously improved the control precision of the high-precision cold-rolled shape control system and promoted its application and application. Based on the preliminary work, the research and popularization of the edge thinning control technology was carried out. Advanced continuous annealing and coating technology, continuous promotion of direct flame impact rapid heating technology, non-oxidation rapid cooling technology and hot-dip galvanizing quality control technology research and development, and carried out the research and popularization of the hot rolling process and equipment technology of cast strip Waiting for work.
 
  Main research progress
  2.1 High-precision cold-rolled plate shape and edge thinning control technology
  High-precision cold-rolled sheet and edge thinning control technology is the core technology to ensure the quality of cold-rolled strip. Independent research and development of high-precision cold-rolled plate shape and edge thinning control and equipment technology is of great significance for improving China's core competitiveness in the field of rolling technology.
  The modern mainstream plate-shaped control cold rolling mill usually participates in the plate-shaped closed-loop feedback control due to various plate-shaped adjustment mechanisms, making it more complicated to control the digital-analog and system. Different from the pattern recognition method based on orthogonal decomposition, RAL is based on the theory of influence efficiency function of independent research. The numerical analysis method is used to construct the control of each shape of the rolling mill tilt, work roll bending roll, intermediate roll bending roll, intermediate roll roll and so on. The effect of the efficiency of the device. The shape control effector is affected by the shape control actuator, the plate shape measured value and the target value deviation, the shape control influence factor and the plate shape control actuator adjustment amount, and the evaluation function is calculated by the optimization method. The minimum value of each actuator adjustment amount under the minimum condition is used as the output value of one closed-loop control, thereby achieving multi-variable optimization shape control (Fig. 1).
  The plate-shaped closed-loop feedback control uses the regulation efficiency coefficient of each plate-shaped adjustment mechanism and the measured plate shape value of each measuring section of the plate-shaped roller, and establishes the shape control effect evaluation function by linear least squares principle to solve the optimality of each plate-shaped adjustment mechanism. Adjust the amount. In view of the importance of the plate shape regulation efficiency coefficient in the shape control system, a self-learning model of plate shape regulation efficacy was developed. In order to obtain accurate plate shape control efficiency coefficient, the accuracy of these prior values ??is continuously improved according to the measured shape data by using artificial intelligence methods such as a neural network.
  The RAL cold-rolled shape control system has a series of proprietary technologies, which are mainly reflected in the following aspects: The online self-learning model for the shape-control efficiency factor of the plate shape has been developed, which is suitable for the plate shape of any plate specification, material and rolling mill model. The control process improves the versatility of the control system. The multivariable optimal shape optimization method based on dynamic constrained convex quadratic programming is developed. It does not need to solve the objective function gradient and Hesse matrix, and does not require the objective function to be continuously differentiable. The dynamic substitution control mechanism of the adjustment mechanism solves the problem of shape control when the actuator is saturated, and opens up new ideas for the in-depth study of the plate shape control technology. The work piece segmental cooling control based on fuzzy control is developed, which is independent of mathematics. The model solves the nonlinear, time-varying and large lag problem that is difficult to solve with conventional control.
  The successful development of RAL cold-rolled sheet shape control technology has formed a unique technical system in the field of international cold-rolled strip production, forming a core technical system with complete independent intellectual property rights control system and process control, and the practical application has achieved great Economic benefits. By the end of 2016, high-precision cold-rolled plate shape control technology has been used in 11 sets of cold-rolling mills such as Angang Steel's 1450mm cold-rolling mill, Angang Tiantie 1800mm cold-rolling mill, Siwenkede 1450mm cold-rolling mill and Shandong Guanzhou 1450mm cold-rolling mill. It has been promoted and applied, which greatly meets the increasing quality requirements of subsequent units and users.
  In the side thinning control technology, the UCM was transformed into a single-end taper work roll and UCMW cold rolling mill in the 1500mm silicon steel cold rolling mill of Anshan Iron and Steel Co., Ltd. On this basis, the edge thinning process control model and adaptive automatic control system for multi-standard strip products such as work roll, speed, bending force and so on have been developed, which greatly reduces the quality requirements of hot rolled incoming crown. The edge thinning control is further improved, the 2σ value is less than 3.15 μm, the quality of the cold rolled product and the finished product rate are increased by 2.7%, and the control precision and product quality of the silicon steel thin strip edge thinning are greatly improved. In 2016, the project “Rough-rolled silicon steel edge thinning control core technology research and development and industrial application” jointly completed by Anshan Iron and Steel and Northeastern University won the first prize of 2016 Metallurgical Science and Technology Award.
  2.2 Advanced continuous annealing and coating technology
  As the market demands for the performance and quality of cold-rolled products become more and more demanding, the existing key technologies of continuous annealing and coating are urgently needed to be broken. High-efficiency and low-cost heating and cooling technologies are important breakthroughs. The advanced cold rolling direction has made important progress in direct flame shock (DFI) rapid heating technology, non-oxidizing rapid cooling technology and hot-dip galvanizing quality control technology research, laying a solid foundation for further industrial application. The specific progress is as follows:
  1) In view of the problems existing in the existing DFI technology, a narrow-pitch multi-flame burner, flame pulse combustion control technology and flame width control technology with independent intellectual property rights have been developed. The pulse combustion control system is greatly simplified, the cost is reduced, and the flame width control method and device are simple and reliable. For the self-developed burner, the finite element simulation research and experiment on the combustion efficiency, flame characteristics, heating rate and pollution discharge are carried out. Research, optimized the burner structure and combustion process parameters, obtained the flame characteristics data (Figure 4), the sheet heating rate reached 180 °C / (s · mm), by adjusting the air-fuel ratio, control the degree of oxidation of the strip surface, heat the DFI The system design lays the foundation; on this basis, the DFI heating furnace (Fig. 5) and the corresponding workpiece transmission and gas supply control systems are designed and manufactured, which are applied to RAL and WISCO thin strip warm rolling heating to realize the breakthrough of industrial prototype.
  2) Carrying out experimental research on non-oxidizing rapid cooling technology, designing the cooling medium circulation supply system and atomizing injection device, verifying the feasibility and safety of the non-oxidation cooling technology, and studying the cooling medium pressure and flow rate to the cooling rate of the sample. The effect and the ultimate cooling rate of samples of different thicknesses. The results show that with the increase of the injection pressure of the cooling medium, the cooling rate of the sample increases. For the 1 mm sample, when the cooling medium injection pressure is 0.25 MPa, the cooling rate is close to 240 ° C / s (Fig. 6 (a)), and the surface Good quality (Figure 6(b)).
  3) Based on the above technology, the feasibility study report and scheme design of a 1500MPa ultra-high strength steel production line has been completed. The production line is characterized by high product strength, fast heating and cooling rate, short production line length, and broadband and multi-flow narrow band. Co-line production.
  4) For the coating process and equipment technology, Northeastern University and Anshan Iron and Steel Group have cooperated to make breakthroughs in the core technology of coating quality control of hot-dip galvanizing products, successfully develop coating thickness control system and realize industrial application. The average thickness deviation of the actual coating is less than 3.2g/m2, which is 1.13% higher than the international advanced level; the plating uniformity 2σ is 1.25g/m2, which is 10.7% higher than the international advanced level, and the annual economic benefit is more than 60 million yuan. In 2015, the project “Development and Industrial Application of Core Technology for Hot Dip Galvanized Steel Coating Quality Control” completed by Anshan Iron and Steel and Northeastern University won the second prize of National Metallurgical Science and Technology. In 2016, the company made breakthroughs in the industrialization of steam spray control zinc flower technology and galvanizing defect control technology. In response to the existing production line problems, it signed an application development contract with Hegang Steel to solve the problem of zinc flow pattern, edge twill, zinc. The galvanized defects such as uneven flower size reduce the variety of transition materials and increase the yield.
  2.3 Thin strip continuous casting + warm rolling new process to prepare high-precision thin strip product development platform construction
  Thin strip continuous casting + warm rolling is a new type of full-process green manufacturing process technology, mainly used for continuous casting, warm rolling and subsequent cold rolling deep processing of high silicon steel, high strength steel and special alloy materials, and can be used for various difficult metal deformations. Special rolling of thin strips. This direction cooperates with the short process direction, and independently designs and develops the first set of thin strip continuous casting + warm rolling pilot test line at home and abroad (Figure 7). Using direct combustion flame rapid temperature rise, furnace coil insulation and online anti-oxidation technology, it has formed an innovative technical route for rapid solidification to improve material properties and temperature processing of difficult-to-deform metal materials: 1) Development of cast strip, heat leveling, furnace roll warm rolling The whole process of nitrogen micro-injection technology in multiple process sections effectively solves the oxidation problem in the process of strip casting, warm rolling and finished products; 2) The self-developed direct-fired rapid heating and furnace coiling system has been successfully applied to the strip On the casting and rolling line, through the application of the furnace coil insulation and the direct heating flame rapid temperature coupling control technology, the problem of constant temperature control of the roll and the rolling section deformation zone during the warm rolling process is solved, and the 3-4 mm high silicon steel thin casting coil is realized. The material was successfully controlled by a rapid incremental cooling and warm rolling process, and a high-volume thin strip material of 0.27 mm continuous coil was successfully prepared. 3) Developed an on-line automatic widening technology device for direct-fired fast-heating flame nozzles, which optimizes the distribution with nozzles, and solves the technical problem of direct heating and rapid heating for different material widths and strip surface temperature uniformization. At present, the above-mentioned advanced technologies have successfully applied and prepared high-silicon thin-band magnetic materials in the RAL laboratory and the WISCO National Silicon Steel Engineering Technology Center thin strip casting and rolling demonstration line.
  A breakthrough in the engineering application of high-magnetism silicon steel for thin strip casting and rolling coil rolling, combined with the national “863” energy-saving high-silicon steel development project for electric motors, Northeastern University and Wuhan Iron and Steel Group Co., Ltd. signed a cooperation project, using “ 2011 plan ”Northeast University Steel Common Technology Collaborative Innovation Center in the field of thin strip casting + warm rolling field technology advantages, in the WISCO National Silicon Steel Engineering Center pilot plant construction of the first set of “500mm thin strip casting and rolling industrialization demonstration line ”The development of thin-belt continuous casting + furnace coil warm rolling preparation of 6.5% Si and other difficult-to-deform thin strip material prototype equipment“ has been developed, and at the same time, the industrialization demonstration application of WISCO pilot plant is implemented. At present, the project has completed the thermal load test of the entire line of process equipment. On April 16th, 2017, the expert group of the High Technology Center of the Ministry of Science and Technology conducted the acceptance of the ”High Silicon Steel Development for Energy-Saving Motors“ project in WISCO and conducted on-site inspection of the thin strip continuous casting + furnace coil warm rolling industrialization demonstration line. The evaluation opinions: 1) The complete process technology of 6.5% Si steel for vacuum smelting, twin-roll casting, multi-pass reversible hot rolling, warm rolling and full-process atmosphere protection was proposed, and 6.5% Si steel near-final was developed. The key equipment for manufacturing; 2) The warm rolling preparation of 6.5%Si thin strip steel was realized, and the 6.5% Si steel cold-rolled thin strip was successfully rolled; 3) The hot rolling was mainly developed, taking into account hot rolling and cold rolling. Rolling function hot/warm/cold three-purpose rolling mill (Fig. 8), through the key technologies of rolling line atmosphere protection, hot coil type coiling and heat preservation, direct combustion and rapid heating, the 6.5% Si steel thin strip coil material is realized. Process advanced process preparation. Currently. RAL Lab's thin strip casting and rolling process technology has obtained a number of industrial applications. It has signed industrial production lines for thin strip casting and preparation of high value-added thin strip products with Hebei Jingye and Jiangsu Yancheng.
  Relying on RAL laboratory thin strip casting + warm rolling experimental platform. Based on the process of production line equipment, establish the latest wireless communication technology such as on-site wireless communication bus network and Wi-Fi network, develop sensor wireless information communication module system, design wireless network topology in industrial environment, in the thin strip casting and rolling experiment line Successfully developed an integrated communication system for field bus and sensor wireless information fast transmission, enabling fast and reliable data transmission from sensor nodes to aggregation nodes to PLCs via Zigbee protocol and TCP/IP protocol to meet the steel production process. Different process characteristics and requirements. Through the information state collection, processing and transmission of metallogenic production line equipment, the mobile terminal system application is transplanted to the industrial control system, and the equipment data status is displayed on the typical mobile client with three-dimensional images to realize the experimental research of thin strip casting and rolling. Platform (such as smelting, casting, warm rolling, furnace coil and collection) full-line dynamic simulation of experimental and production processes and data monitoring and real-time dynamic monitoring of various process sections of the experimental process. At the same time, it greatly simplifies the interconnection and information intercommunication of the control devices in each process area, intelligently integrates the wired and wireless network data, and solves the fast and flexible intelligent sensing demand for the detection data in the production process, and the product quality under complex process conditions. Technical support is provided by integrated management of performance.
  Developed and designed an industrial wireless network architecture, wirelessly connected various process control areas and production line instruments, simplified information exchange between process area equipment, suitable for flexible adjustment and quality control of production processes; aimed at large data storage and processing in production process, development A high-speed data acquisition system based on fieldbus network supports high-speed data collection of wireless data, and analyzes the requirements of distributed information processing platform for the defects of centralized storage and calculation. Standard analog signal wireless sensor templates have been developed and high speed signal transmission has been achieved.
  Conclusion
  Thin strip steel high-precision rolling and heat treatment process and equipment technology research and development, providing important technical support for the production of high-end cold-rolled strip steel products, especially green strip casting and high magnetic induction electrical steel technology has completely changed the traditional electrical steel The production process and composition design can produce high-quality electrical steel with different silicon content and different thicknesses with lower cost, simpler process, higher quality and less investment. For the sustainable development of national economy and national security in China has great significance.