In recent years, the competition in the iron and steel industry has become increasingly fierce, and enterprises can achieve further development only by continuously carrying out technological transformation, improving product quality and reducing production costs. In order to meet the needs of the market, Xuangang built two new six-machine six-strand continuous casting machines with the same model, and in the subsequent upgrading and transformation, the continuous casting machine has been upgraded to increase the flow. At present, the annual production capacity of a single machine has exceeded one million Ton. This paper mainly introduces the network structure, bus layout and main functions of the automation system after the transformation of the two continuous casting machines.
The 4# and 5# continuous casting machines of Xuangang Steelmaking Plant are key engineering projects of Xuangang, and its automation control level has reached the domestic advanced level. The software and hardware are mainly products of Rockwell Automation, which constitute a three-level network structure, which realizes the automatic production control, production scheduling command and product quality control of the continuous casting machine.
The system network structure is shown in Figure 1:
Figure 1 Control system network structure diagram
As can be seen from the above figure, the automation system of the continuous casting machine takes into account the needs of practical applications, makes full use of the resource characteristics of software and hardware, and builds a three-layer network structure, that is, the information layer, the control layer, and the equipment layer.
2.1 Information layer
The information layer should provide a network interface for the operation and maintenance of the continuous casting machine body and the plant-level computer system, access workshop-level production and management data, provide services for the data collection and monitoring of the plant-wide control system, and accept production scheduling instructions. , to coordinate the production of the whole factory. This layer is characterized by a large amount of data, but does not have high requirements for real-time performance. At the same time, in order to facilitate the interconnection of PLCs and computer systems of different manufacturers, necessary control and coordination, the TCP/IP protocol that conforms to public standards is adopted. 100Mbps rate Ethernet.
Considering the reliability requirements of industrial control and the harsh environment of the industrial site, the Ethernet adopts a redundant optical ring network, and two industrial-grade Ethernet switches have redundant management functions. One server and four operating stations of the continuous casting machine are connected to the network through the Ethernet card, and each frame of the PLC system installed with the CPU module is connected to the network through the Ethernet interface module.
2.2 Control layer
The control layer is responsible for the transmission, exchange and coordination of control data among the public PLC system, each casting strand PLC system and remote Flex I/O, and provides functions such as network programming, program maintenance, equipment configuration, and troubleshooting.
The network at this layer not only requires a stable and reliable connection, but also ensures the real-time transmission of information. ControlNet adopts the bus topology structure, the communication rate is 5Mbps, and its characteristic is that ControlNet is deterministic, which means that the I/O devices and controllers on the network communicate at a predetermined time. Every component in ControlNet has determined the communication time and duration in advance during configuration, so it is very stable and reliable, especially suitable for industrial applications with high time requirements. At the same time, in order to ensure that communication will not be interrupted, we use redundant communication media at this layer to further improve reliability.
2.3 Device layer
The equipment layer is mainly used to directly connect the main line transmission equipment, that is, the frequency converter and the soft starter, to the PLC system to which it belongs, instead of realizing control through traditional digital and analog connections. This is not only convenient and fast, but also can collect data. Data from field devices, which are configured, monitored and controlled in real time. This layer uses the Remote IO network.
The three-layer network structure makes it possible to select the appropriate communication method according to the specific application requirements of the continuous casting machine system. This network structure not only provides EtherNet/IP, ControlNet, Remote IO network connections, but also includes advanced software optimized for automatic control. interface to ensure efficient data transfer.[page]
3. System composition and function
3.1 Hardware configuration
The hardware of each continuous casting machine automation system is mainly composed of 9 sets of Rockwell AutomaTIon’s ControlLogix series PLC, 4 operation stations, 1 server and remote Flex I/O station. The main production line equipment in the transmission system is all driven by vector inverters. The water pump uses a soft starter, and the auxiliary drive equipment is controlled by the MCC. The instrumentation system is mainly composed of a rapid and continuous temperature measurement system for molten steel, a large bag and a middle bag weighing system, a mold liquid level monitoring and adjustment system, and a mold water and secondary cold water flow detection and adjustment system.
The public system of the continuous casting machine adopts a set of PLC system with an extended frame, which is used for the detection and control of the common equipment on the main table of the continuous casting machine and the part of the billet. ,control. The operation station is arranged in the main control room and the cutting operation room for monitoring, operating, processing alarm information and necessary human intervention on the equipment of the continuous casting machine. The server is used to collect production data, process, store, and transmit it.
3.2 System functions
The automation system of the continuous casting machine adopts the three-electrical integration design. All electrical control and instrument control signals are connected to the PLC. The thermal resistance, transmitter, flowmeter and other detection instruments installed on the site collect instrument data, switches, limits, etc. The equipment collects production process data and equipment operating status, and all data is imported into the PLC system. Combined with the instructions from the upper operating station, the process loop adjustment, electrical equipment sequence control and transmission equipment control are realized according to the preset program.
3.2.1 Instrumentation system
Instrument detection mainly includes rapid and continuous measurement of molten steel temperature in large and medium ladles, weight measurement of molten steel in large and medium ladles, measurement of mold water pressure, flow, temperature difference between inlet and outlet, secondary cooling water pressure, and flow measurement and adjustment of each section. In order to reduce the labor intensity of operators and improve the quality of steel billets, the continuous casting machine also collects the molten steel level of the mold, and adjusts the opening of the middle bale plug rod through the electric cylinder to keep the molten steel level stable.
The secondary cooling water distribution system has manual and automatic control functions, including water distribution, water meter setting, tracking adjustment, adjustment of water distribution correction, and Display of water flow, pressure, temperature and valve position. PLC realizes on-site data acquisition, tracking adjustment, and the operation station completes the water meter setting, water flow Display and data recording, data printing and statistical functions.
Manual and automatic control: Each flow is divided into four stages of water distribution, namely the foot roller section, the first stage, the second stage, and the third stage, and each stage has a manual/automatic conversion function. In the manual mode, the staff can change the water volume by directly setting the opening of the regulating valve on the screen of the operation station; in the automatic mode, the system will automatically adjust the water volume according to the pre-selected water meter according to the speed of the pulling speed. The water supply can be corrected at any time according to the billet temperature. The flow chart of the secondary cold water adjustment is shown in Figure 2.
Reconstruction of network structure and automation system of continuous casting machine based on field bus technology
Figure 2 Flow chart of the second cold water conditioning
Selection and modification of water meters: Dozens of sets of water distribution parameters are available for use in the operation station. The content of the parameters includes: serial number, steel type, section and water distribution ratio of each section. The operator can modify the parameters at any time to change the water distribution.
3.2.2 Electrical system
The detection and control of electrical equipment mainly include: rotation of the turntable of the large bag, lifting and lowering of the bag arm, opening and closing of the water inlet of the large bag, walking, centering, and lifting of the tundish truck, vibration of the mold, adjustment of the vibration frequency, transmission of the tension leveling machine, and tension leveling. Rolling down, dummy bar ascending, recovery tracking, stripping, storage, billet cutting to length, as well as the control of roller table before and after cutting, conveying roller table, steel turning machine, billet separator, and stepping cooling bed. The detection and control of hydraulic system, oil and gas lubrication system and dry oil lubrication system are also completed by PLC.
All the transmission equipment of the main production line is driven by frequency converters. More than 100 frequency converters are used in the transmission of mechanical equipment such as the ladle turntable and the lateral moving steel car in the continuous casting machine, and the power range is from 0.75KW to 45KW. All frequency converters are connected to the Remote I/O communication adapter through its built-in communication interface, and are directly connected to the nine Remote I/O networks formed by nine RIO interface modules, forming a transmission system based on the Remote I/O network. Considering the connection distance of the Remote I/O network and the real-time requirements of the system, the communication rate of 115.2Kbps is adopted.
The Remote I/O network works in the scanner mode, and the PLC processor establishes a serial communication chain through the RIO interface module and the remote I/O adapter. The communication interface of the inverter provides a direct and digital communication link for the network devices in the Remote I/O network. The system uses the communication interface to establish an input and output data link by configuring the I/O label of the PLC. For PLC, each inverter is regarded as a remote frame with I/O modules installed, and it is only necessary to read and write these modules to send commands to the inverter connected to it to control the operation of the equipment; It can read various data from the inverter, monitor the running status of the equipment, and transmit the data to the PLC in real time. Through the screen, the operator can provide real-time and detailed information on the display of the operation station in the main control room, and can directly operate the equipment. Even when the inverter issues an alarm and fails, the inverter can be reset in time to avoid Failure to handle it in a timely manner results in an accident. The electrical system of the continuous casting machine realizes the remote network real-time control of the transmission equipment, and enables the PLC to realize the networked digital control of the drive of the inverter. Compared with the control method, not only the real-time performance, accuracy and reliability of the system are greatly improved, but also the cost of installation, debugging and maintenance is correspondingly reduced.
3.2.3 Operation Station
According to the process requirements, the HMI screen software is equipped with the main screen, the overview of the casting strand, the overview of the blanking area, the tension leveler and the dummy bar, the liquid level of the mold, the vibration of the mold, the weighing of the big bag/middle bag, the hydraulic system, the drive There are nearly 20 pictures including device running status and PLC status. Through the monitoring of HMI, the operator can observe the operation status of the equipment in real time, modify the process parameters according to the authority, deal with the alarm events in time, and manually intervene in the operation of the equipment if necessary.
3.2.4 Command and dispatch system
Steelmaking is a complex production process. The quality of continuous casting billets is directly affected by casting conditions and process status. Even if advanced technology, equipment and technology are used, due to the characteristics of continuous casting production process, heat transfer and equipment failure and unstable operation, etc., will inevitably cause fluctuations and abnormalities in the production process, so that the quality of the casting billet will be damaged to varying degrees. Loss. The continuous casting machine needs to know the situation of the previous process in time, and the converter and refining system must also grasp the casting situation of the continuous casting machine. , Argon blowing station and other systems are jointly connected to the factory-level management network to provide data for unified coordination and command of production scheduling.
4. Application effect
The continuous casting machine automation control system of Xuangang Steelmaking Plant comprehensively integrates PLC control technology, screen monitoring technology, network communication technology and frequency conversion speed regulation technology. The automatic control of the production process completes the functions of automatic interlocking control of continuous casting production site equipment, detection and adjustment of medium parameters, data communication processing, fault alarm diagnosis and online monitoring of production conditions. After more than three years of operation and verification, the system control function is advanced, stable and reliable, which effectively improves labor productivity and reduces the labor intensity of staff. effect.