Overview
Xuanhua Steelmaking Plant 4# and 5# continuous casting machines are the key projects of Xuanhua Iron and Steel, and its automation control level has reached the domestic advanced level. The system adopts the currently popular three-electric integration design, and extensively uses fieldbus technology and automation systems. The hardware and software are based on Rockwell Automation's products and form a three-level network structure, which realizes the automatic control of the continuous casting machine production, production scheduling and command, and product quality control.
System network structure shown in Figure 1:
Figure 1 Control System Network Structure
From the above figure, we can see that the continuous casting machine's automation system takes into account the needs of practical applications, make full use of the resource characteristics of hardware and software, and build a three-tier network structure, namely information layer, control layer, and device layer.
1 Information layer
The information layer shall provide a network interface for the operation, maintenance, and plant-level computer system of the continuous casting machine, access the plant-level production and management data, provide services for data collection and monitoring of the entire plant-wide control system, and accept production scheduling instructions. , Coordinate the whole plant production. This layer is characterized by a large amount of data, but no real-time requirements, and at the same time to facilitate the interconnection of different manufacturers of PLC and computer systems, to carry out the necessary control and coordination, and thus adopt a public standard TCP/IP protocol 100Mbps Ethernet.
Taking into account the reliability requirements of industrial control and the harsh environment of industrial sites, Ethernet uses a redundant optical ring network structure, and two industrial Ethernet switches have redundant management functions. A server and four operating stations of the continuous casting machine are connected to the network via an Ethernet card. Each frame of the PLC system with a CPU module is connected via an Ethernet interface module.
2 control layer
The control layer is responsible for transferring, exchanging, coordinating and controlling the control data between the public PLC system, each cast-flow PLC system and the remote Flex I/O, and provides functions such as network programming, program maintenance, device configuration, and troubleshooting.
This layer of the network not only requires a stable and reliable connection, but also ensures the timely delivery of information. ControlNet uses a bus topology with a communication speed of 5 Mbps. 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 already established the communication time and duration in advance in the configuration, so it is very stable and reliable, especially suitable for the industrial application with higher time requirement. At the same time, in order to ensure that communications will not be interrupted, we have used redundant communication media at this level to further improve reliability.
3 equipment layer
The equipment layer is mainly used to directly connect the main line transmission equipment, ie, the inverter and the soft starter, to the affiliated PLC system. It is no longer controlled through traditional digital and analog connections. This is not only convenient and fast, but also can be acquired. Field equipment data, configuration, monitoring and real-time control. This layer uses RemoteIO 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 architecture not only provides EtherNet/IP, ControlNet, and RemoteIO network connections, but also includes an advanced software interface optimized for automatic control. To ensure efficient data transmission.
System composition and function
1 hardware configuration
The hardware of each continuous casting machine automation system is mainly composed of 9 sets of Rockwell Automation ControlLogix series PLCs, 4 operating stations, 1 server and remote Flex I/O stations. The main production line equipments in the drive system are all driven by vector inverters and the pumps are used. Soft starters, auxiliary drives are controlled by the MCC. The meter system consists of a rapid and continuous temperature measurement system for molten steel, a large package, a middle package weighing system, a crystallizer level monitoring and regulation system, a crystallizer water, and a second cold water flow detection and adjustment system.
The continuous caster public system adopts a PLC system with an extension rack, which is used for the detection and control of the common equipment on the caster body and the delivery part of the caster. Each cast system of the PLC system is used to monitor the caster system. ,control. The operating station is arranged in the main control room and cutting operation room for monitoring, operating, processing alarm information and necessary human intervention of the caster equipment. The server is used to collect production data and process, save, and transfer it.
2 system function
The continuous casting machine automation system adopts three-electrical integration design. All electronic control and instrument control signals are connected to the PLC. The thermal resistance, transmitter, flowmeter and other detection instruments installed on the site collect instrumentation data, switches, and limit positions. The equipment collects the production process data and equipment operating status. All data is imported into the PLC system. Combined with instructions from the upper operating station, process loop adjustments, sequential control of electrical equipment, and transmission equipment control are performed according to pre-set procedures.
1) Instrument system
Meter detection mainly includes rapid and continuous measurement of molten steel temperature in large and medium packages, weight measurement of molten steel in large and medium packages, water pressure, flow rate in crystallizer, temperature difference measurement at inlet and outlet, secondary cooling water pressure, flow measurement and regulation in each section. In order to reduce the labor intensity of the operator and improve the quality of the billet, the caster also collects the liquid level of the crystallizer and adjusts the opening degree of the plug rod through the electric cylinder so that the molten steel level remains stable.
The secondary cooling water distribution system has manual and automatic control functions, including water distribution, meter setting, tracking adjustment, water adjustment adjustment, water flow, pressure, temperature and valve position display. PLC realizes on-the-spot data acquisition, tracking and adjustment, the operation station completes the setting of the water meter, the display of water flow and data recording, data printing and statistics functions.
Manual, automatic control: Each section is divided into four sections of water distribution, namely foot roller section, section, section two and section three. Each section is equipped with manual/automatic conversion function. In the manual mode, the worker changes the water volume by directly setting the valve opening of the control valve on the operation station screen; under the automatic mode, the system will automatically adjust the water flow according to the speed of the pulling speed according to the pre-selected water meter. During the casting process, The amount of water can be corrected at any time based on the billet temperature. The second cold water regulation flow chart is shown in Figure 2.
Figure 2 II cold water regulation flow chart
Water meter selection and modification: Dozens of sets of water distribution parameters are available for use in the operation station. The parameters include: number, steel type, section, and water ratio of each section. The operator can modify the parameters at any time to change the water distribution.
2) Electrical system
The detection and control of electrical equipment mainly includes: rotation of the bale turret, lifting and lowering of the arm, opening and closing of the bales, walking, centering, lifting of the caster, vibration of the crystallizer, adjustment of the vibration frequency, driving of the leveling machine, and pulling Under roller pressure, the dummy rods are ascended, recycled and tracked, stripped and stored, the billet is cut to length, and the front and rear roller paths, conveyor roller paths, steel turning machines, slab separators and step cooling beds are controlled. Hydraulic system, oil-air lubrication system, dry oil lubrication system detection and control are also completed by the PLC.
All the main production line transmission equipments are all driven by frequency converters. The caster has used more than 100 frequency converters from the ladle rotary table to the horizontal steel transfer equipment and other mechanical transmissions. The power range is from 0.75KW to 45KW. All frequency converters are connected to Remote I/O communication adapters through its built-in communication interface and directly connected to nine Remote I/O networks formed by nine RIO interface modules to form a transmission system based on Remote I/O network. Considering the connection distance of the Remote I/O network and the real-time requirements of the system, a communication rate of 115.2 Kbps is used.
The Remote I/O network works in the scanner mode. The PLC processor establishes a serial communication link through the RIO interface module and the remote I/O adapter. The communication interface of the inverter provides direct and digital communication links for the network devices in the Remote I/O network. The system configures the I/O tags of the PLC and uses the communication interface to establish input and output data links. For PLCs, each drive is viewed as a remote chassis with I/O modules installed. It is only necessary to read and write these modules to send commands to the connected drive to control the operation of the drive. Can read various data from the frequency converter, monitor the running status of the equipment, and convey the data to PLC in real time. Through the screen, you can provide the operator with real-time and detailed information on the operation station display of the main control room, and can directly operate the equipment. Even when the frequency converter issues an alarm, when the fault occurs, the inverter can be reset in time to avoid the cause. Failure to deal with it led to an accident. The electrical system of the continuous casting machine realizes the real-time control of the remote network of the transmission equipment, enables the PLC to drive the inverter to realize the networked digital control, and replaces a large number of hard wirings with a communication cable, and the traditional analog quantity and switching quantity. Compared with control methods, not only greatly improve the system's real-time, accuracy and reliability, but also reduce the cost of installation, commissioning and maintenance.
3) Operation Station
According to the process requirements, HMI screen software has main screen, cast flow overview, billet area overview, drawing and leveling machine and dummy bar, mold liquid level, mold vibration, large/medium bag weighing, hydraulic system, and drive Device operation status, PLC status, etc. Nearly 20 screens. Through the monitoring of the HMI, the operator can observe the running status of the equipment in real time, modify the process parameters according to the authority, and handle the alarm events in time, and if necessary, can manually intervene the operation of the equipment.
4) Command and dispatch system
Steelmaking is a complex production process. The quality of continuous casting slabs is directly affected by casting conditions and process conditions. Even if advanced processes, equipment, and technologies are used, due to the influence of the characteristics of continuous casting production processes, heat transfer and equipment failures occur. Inconsistent operations and the like will inevitably cause fluctuations in the production process, resulting in abnormalities, so that the quality of the billet is subject to varying degrees of damage, the impact on the subsequent rolling process and the quality of the final product can not be ignored, resulting in economic and product reputation for the enterprise Loss. The continuous casting machine needs to know the conditions of the upstream process in time, and the converter and the refining system must also grasp the casting conditions of the continuous casting machine. To facilitate intuitive and rapid understanding of the entire production process, the automatic system of the continuous casting machine provides network excuses, and the converter and the refining The systems such as argon blowing stations are connected to the plant-level management network to provide data for the unified coordination and command of production scheduling.
Application effect
Xuanhua Steel Plant's continuous casting machine automation control system integrates PLC control technology, screen monitoring technology, network communication technology, and frequency conversion speed control technology. The integration of the three electrics adapts to the development trend of automation and realizes the foundation of the continuous casting machine. The automatic control of the production process completes the automatic interlock control of the continuous casting production field equipment, the detection and adjustment of the medium parameters, the data communication processing, the fault alarm diagnosis, and the on-line monitoring of the production status. After more than three years of operation verification, the system control function is advanced, stable and reliable, effectively improving labor productivity, reducing the labor intensity of the staff, and playing an active role in successfully putting into production, reaching production, increasing production efficiency, and maintaining safe production. effect.