Automation control of hot rolled strip production line

Hot rolling is the main process in strip steel production. Part of its products are used directly as finished products, and the other part is used as semi-finished products after deep processing such as cold rolling, welded pipes and cold bending. At present, due to the high cost of cold rolling, “heat replaces cold”. “Gradually becoming a trend in strip steel production.

1. Current status of informatization in hot-rolled strip mills

The production line adopts four-level computer management, which enables the establishment of a network architecture at different application levels. Each network is interconnected step by step, and each system manages production, quality and logistics. For example, ERP integrates the procurement management system with the production and warehousing management system to synchronise plans, flow, inventory, and documents. ERP orders form production schedules in MES. MES supports functions such as uploading plan execution data, actual production information, etc. to ERP. Information technology assists in quality inspection. Key inspection systems or inspection equipment can automatically output inspection result data to relevant systems, laying the foundation for intelligent construction.

2. Development ideas for smart manufacturing in hot-rolled strip mills

Realize the intelligentization of hot rolling mill production organization, manufacturing equipment, quality control, efficiency improvement, safety assurance, cost control, and analysis and decision-making processes. Taking key production lines as breakthroughs, smart manufacturing work will focus on basic automation, unmanned driving, station and room centralized control, robots, model optimization and 3D visualization, status detection and intelligent inspection. Those with high technological maturity, easy implementation, and significant improvements in quality and efficiency will be implemented first and gradually promoted to other production lines.

2.1 Intelligent production and quality control

Starting from the entire production process of raw materials, heating, continuous rolling and finishing, we will establish an intelligent production and quality control system to fully realize intelligent production and quality control.

(1) Intelligent production control.

Taking smart decision-making as the premise, based on big data, multi-model combination, power-off optimization algorithm, high-level human-computer interaction and other strategies, establish a complete production process resource optimization allocation, automatic production orchestration, tracking, early warning and dynamic optimization adjustment A cross-production line integrated production intelligent management and control system with other functions.

(2) Full-process quality control system.

Establish accurate spatiotemporal matching of the whole-process material flow and information flow, realize traceability analysis of the whole-process product quality, and build an automatic blocking system for product defects and an intelligent prediction system for the microstructure and performance of hot-rolled strip steel.

(3) Cost analysis system.

Accurately analyze and predict the energy media consumption and corresponding costs of each rolling stock in each process.

2.2 Intelligent equipment management and control

Intelligent means are used to achieve intrinsically safe and stable operation of equipment, with the main line of sensing equipment and liberating manpower, carrying out self-intelligent exploration, intelligent monitoring, analysis and early warning, intelligent inspection and virtual practice and cycle management, and exploring equipment remaining life cycle modelling.

2.3 Intelligent control

The purpose of intelligent manufacturing is to use automation, intelligent technology and robotic systems to free manpower from tedious, dangerous and repetitive labour and improve work efficiency.

(1) Unmanned crane

Starting from the actual situation on site, we comprehensively consider the slab warehouse and steel coil inventory management process, the three-dimensional positioning of the crane, automatic data collection and wireless communication technology, and finally realize the unmanned crane for the slab warehouse and steel coil inventory.

(2) Intelligent control of heating furnace area

Establish an intelligent slab identification and verification system to realize automatic steel loading in the heating furnace. Establish a heating furnace combustion process control system to realize automatic steel burning in the heating furnace. Establish a rolling rhythm control system to realize automatic tapping of the heating furnace.

(3) Intelligent control of intermediate blank shape

At present, the shape of the hot-rolled intermediate billet such as sickle bend and button warp is generally adjusted manually by the operator. By establishing a sickle bend and button warp control model, a material shape detection device is installed at the rough rolling inlet and outlet to realize the sickle bend and button warp of the intermediate billet. Automatic adjustment of the head.

(4) Intelligent control of strip deviation and wedge shape

At present, the deviation and wedge shape of hot-rolled strips at home and abroad are generally adjusted manually by operators, and an automatic model control system for finishing rolling deviation and wedge shape has been established.

(5) Optimized shearing closed-loop control of intermediate billet

The optimized shearing system of the intermediate billet in the hot rolling production line basically adopts open-loop control. The intermediate billet and flying shear are independently controlled, which affects the shearing accuracy of the head and tail of the intermediate billet. Using the closed-loop control system for optimized shearing of the intermediate billet, the flying shear can intelligently sense the operating status of the intermediate billet, promptly correct the acceleration of the flying shear drum, and achieve precise shearing of the head and tail of the intermediate billet.

(6) Intelligent measurement and control and model technology for hot rolling production lines

For key process parameters such as rack wave shape and coiling shape during the hot rolling production process, image processing technology can be used to achieve real-time measurement and build a feedback control system. Establish a more accurate model through big data and AI technology, realize the automation of the entire hot rolling production process, and improve the accuracy of model control.

(7) Intelligent technology for surface quality detection and control of rolls and pinch rolls

Carry out automatic detection and determination of roll surface quality, big data analysis and prediction of roll health throughout the life cycle, intelligent roll grinding control model, and hot rolling online roll grinding and other technical research to reduce defects caused by rolls and realize pinch rolls Online monitoring.

(8) Hydraulic roll gap control

The main components of the hydraulic roll gap control system include a power source, adjustment device and actuator. The following is a detailed analysis of the hydraulic roll gap control system of a cold rolling mill in a steel plant.

Power source:

5 constant-pressure variable pumps form a pumping station in the pressure system. One of the variable pumps is standby. There is also a pilot-operated relief valve connected in parallel at the outlet of each variable pump. This pilot-operated relief valve The relief valve mainly functions as a safety valve. At present, high-power high-pressure servo systems generally adopt this multi-pump configuration. The advantages of this configuration are small energy loss and high efficiency, especially suitable for high-voltage and high-power systems. At the same time, it is especially suitable for systems with large flow changes and intermittent operation.

Actuator:

In the actuator, the main components include an electro-hydraulic servo valve, hydraulic cylinder, rolling mill load, thickness gauge, displacement sensor pressure sensor, etc. The servo valve can control the liquid flow entering the hydraulic cylinder, and then the up and down movement of the upper support roll and the upper work roll is controlled by the hydraulic cylinder and related mechanisms in the frame, thereby achieving the purpose of controlling the rolling pressure and pressing position.

Adjustment device:

The hydraulic roll gap control system can make the strip thickness reach the set target deviation range and adjust the rolling mill roll gap online. In the closed-loop control of position and rolling force, the feedback signal controls the amount of oil in and out of the hydraulic cylinder through the servo valve to adjust the position of the roll gap. The adjustment device exists in two independent closed-loop systems, namely rolling force control and position control. The two control methods are similar in type. When adjusting the roll gap, the results of their respective adjustments are accumulated. In the entire closed-loop control system, the first four racks all adopt position closed-loop control. The specific reduction setting is mainly based on the flow rate per second law and the constant power principle of the middle rack. The advantage of this closed-loop position control method is that it achieves better flatness at the inlet, which plays an important role in controlling the shape of the product. The fifth stand uses a rolling force control method, which can reduce the impact of roll eccentricity on the final product. the impact caused.

In terms of intelligent production and quality control, intelligent equipment control and analysis and early warning, high-efficiency intelligent equipment, intelligent safety, as well as automated steel rolling and centralized control, we will create an intelligent, high-efficiency, low-cost green hot-rolling production line to achieve It is unmanned, requires fewer people, integrates operation and testing, and centralizes management and control to achieve quality and efficiency improvement, safety and energy saving, equipment status is monitored in a timely manner, and the degree of automated steel rolling is improved.

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