Abstract: The production efficiency and billet quality of the continuous casting machine are directly affected by the automation level of metallurgical continuous casting production. The application of PLC control system greatly improves the automation level of the metallurgical continuous casting electrical control system, and ensures the precision and casting of the metallurgical industry. The quality of the blank. Therefore, it is necessary to strengthen the use of the PLC control system in the metallurgical continuous casting electrical, continuously optimize its design, give play to the function and role of the PLC control system, and improve the overall level of metallurgical continuous casting electrical control.
The continuous casting process is an intermediate link between steelmaking and steel rolling. It can convert liquid steel into cast slabs. Therefore, the continuous casting production process directly affects the quality of metallurgical rolled steel and the yield rate. With the advent of the PLC control system, this system is now being used in metallurgical continuous casting electrical appliances, which improves the continuous casting technology and greatly improves the automation control level of the continuous casting machine.
1. The main composition and function of PLC control system
1.1 The basic composition of a PLC control system
Siemens' S7-300/400 system uses PLC control system. Its hardware technology and software system are mature, making data more convenient. At present, PLC control systems are beginning to be used in the field of metallurgical automation, and its intelligent system is a simulation of human thinking activities. As a technology with a wide range of designs, the PLC control system integrates multiple disciplines and the system is complex, so that the intelligent control process of the metallurgical automation system can be replaced by it.
1.2 Configuration of PLC control system
The PLC control system is composed of 2 sets of PLC cabinets, 2 control stations, 1 engineer station and 1 network printer. The setting of 2 control stations is to prevent control failure in emergency situations and ensure the reliability of the system. Two sets of control stations are used on the host and auxiliary machines of metallurgical automation production. Fault-tolerant Ethernet interface modules, S7-400 control processors, power modules, redundant modules, I/O modules, etc. constitute its main components. The Intel CPU 2.8GHZ is the main configuration of 2 control stations and 1 engineer station, using Windows XP sp3 operating system and 19LCD display, with 4GB RAM storage capacity. And its software configuration includes the control station programming software STEP 7 V5. 5 SP2, 2 control stations FIX 6. 15 running edition monitoring software, 1 FIX 6. 15 development edition engineer station monitoring software.
1.3 The function of PLC control system
The use of the PLC control system needs to initialize the processing data system first. Usually, when the control system is put into operation, runs after precise inspection, or after the system fails, the system needs to be restarted for initialization processing at this time. This process first needs to read the status information and condition information of the process equipment, and display the process flow chart and equipment operating status. After all timers and timers are cleared, the device operation mode is set to "manual" mode, and then the operator "manually" operates to specify the mode and status of each device. Under the condition that the current state of the equipment is normal and the operating conditions are available, the operator sets the operation mode and switches the program operation from the "manual" mode to the "automatic" mode. And also choose its operating place. There is a "remote control/near control" authority selection switch on the operation box next to the machine, and the operation site of the equipment that needs to be controlled on the PLC is set to the "near control" position, and the field equipment is started ( Open), stop (close) operations need to use the operation indicator light and operation buttons on the operation box next to the machine. When performing "remote control" operation, it is necessary to set the selector switch, and perform remote operation at the PLC control station of the central control room. For failures that occur during the operation of the PLC control system, another control station will promptly send out an alarm signal and print a failure report. Usually PLC failures include communication failures, CPU failures, and redundant board failures. At this time, the system will automatically switch to redundant equipment without interruption, and an alarm signal will be issued by the operating station. When a non-redundant board fails, Professionals confirm and exclude.
2. Application of PLC automatic control system in metallurgical continuous casting electrical
2. 1 Large package turntable control
The large package turntable is driven by the motor to rotate, and rotates from the ascending position to the descending position after positioning. The large ladle turntable of the metallurgical continuous casting machine needs to carry two ladle. During the casting process, it is necessary to switch between the casting and the waiting state. In this process, the turntable bears a large pressure, and the turntable will fluctuate during long-term rotation. Therefore, in order to improve the efficiency of the rotation process, it is necessary to accurately control the rotation speed and time of the package turntable to prevent the rotation time from being too long. When the large package turntable rotates, the rotation angle should be precisely controlled, and the rotation angle should be detected by a pulse encoder. To use pulse encoder detection, two synchronized switches must be installed beside the large package turntable, the pulse is cleared, and the detection is done. If the bale turntable rotates to the casting position, it can be stopped by the PLC control coil.
2.2 Equipment cooling water control
The operation process of the metallurgical continuous casting machine must strictly control the water flow, including the temperature, pressure and flow rate of the cooling water of the equipment. The water pump pressurized cooling water system can supply water to the continuous caster equipment, cool the water, and pressurize it again after the cooling tower is cooled. The water pump needs to pressurize the water flow from the cooling tower. The PLC control system detects the pressure and temperature of the pressurized water flow. The cooling water supplied to the continuous caster equipment must meet the requirements. Before the water from the continuous caster equipment enters the next cycle of use, the temperature and flow rate of the water flow can be controlled by the PLC control system.
2.3 Sliding nozzle control
The molten metal in the big bag needs to pass through the sliding nozzle to flow into the middle bag, so the opening and closing state of the big bag must be controlled to ensure the accuracy of the nozzle flow and effectively prevent safety accidents. In addition, a weighing sensor is required to detect the signal of the liquid level in the bag, and its application should be combined with the signal detected by the PLC control system to set the program and process. This calculation result provides a basis for controlling the movement of the large bag sliding nozzle.
3. The design strategy of PLC control system in metallurgical continuous casting electrical
3.1. Pull-straightening hydraulic station
The working oil pump needs to be selected for automatic operation of the tension and straightening hydraulic station. When the system pressure is lower than 5. 5Mpa, the working oil pump will be started. After 1 minute delay, the solenoid valve will be energized and the system will start to supply oil. If the system pressure is greater than 7Mpa, the solenoid valve is de-energized and the oil pump will stop supplying oil. Therefore, the low limit signal of the fuel tank liquid level can be serially connected to the control circuit of the oil pump and the solenoid valve, so that when a low liquid level occurs due to a serious leak in the pipeline, the system will automatically close the oil pump and the solenoid valve after a period of delay to ensure Safety of system equipment under abnormal conditions. The rectification hydraulic station can carry out sound and light alarm, and display the alarm information in the monitoring screen of the host computer.
3.2 Process of automatic starting spindle feeding
The function of the automatic starter feeding process is to run/stop the tension leveler, the starter rod storage motor,
The safe operation of the process effectively avoids huge economic losses and personal safety. therefore,
Automatic lifting/pressing down roll and stripping roll, through the automatic feeding process to ensure continuous casting production
In the program of automatic starting spindle feeding, the dual control of limit switch and time interlock should be designed to ensure
Under normal conditions, the equipment control is completed by the limit switch. Once the limit switch fails, its control is carried out by a timer, which guarantees the safety and reliability of the control operation.
3.3 Automatic casting of slab cutting in the process of slab cutting
The working state has two modes: full-automatic and semi-automatic. Among them, the fixed-length signal sent by the sizing instrument is the cutting command in the automatic mode. When the slab reaches the fixed length, the semi-automatic cutting mode will artificially issue the cutting command. Once receiving the cutting command, the cutting machine immediately starts to cut the billet, and the clamp cylinder solenoid valve and the preheating gas, preheating oxygen, and cutting oxygen solenoid valves will all be energized respectively. After the slab is cut, the solenoid valve of the return cylinder is energized at this time, and all other solenoid valves will be de-energized, and the cutting machine will return to the initial position for automatic cutting of the slab.
3.4 The main order of the pusher
The push-steel contact and the return contact of the controller control the working stroke of the push-steel machine. The control design of this system is for its safety interlock. When the stepping turning cooling bed is working, the pusher cannot push the steel, and the pusher cannot push the steel at the same time as the turning machine turns the steel, so as not to make the pusher and the turning process of the pusher move. The steel turning machine in the conflict. Generally, after the steel pushing machine completes a pushing cycle, the action blockade of the steel turning machine must be unlocked, and then the steel turning machine will continue the next steel turning process.
3.5 Step-by-step turning cooling bed
When shortening the storage interval of casting billets on the cooling bed, the cooling bed can be reversed stepwise, and the casting billet transportation uses the forward rotation of the cooling bed. The forward and reverse contacts of the master controller installed on the shaft of the reducer control the forward, reverse and stop actions of the cooling bed. This control task accurately controls the master controller contacts to stop when the cooling bed stops. Tooth position, because if the cooling bed stops at the upper tooth position, it will hinder the pushing operation of the steel pusher. When the cooling bed is working automatically, it is necessary to design the program for the pusher to retreat for a period of time to make the cooling bed continue to rotate forward, because the pusher cooling bed moves immediately after it is retracted, and it is prone to collision with the pusher. Make the equipment damaged. Therefore, to ensure that the cooling bed rotates continuously for 8 weeks and complete the conveying work of up to 8 slabs at a time, the calculation of the cooling bed's forward rotation action time must be combined with the cooling bed motor speed, reducer reduction ratio, and master controller reduction ratio And other technical parameters. Through this program design, the closing action of the master contact can immediately stop the cooling bed. When the cooling bed is controlled to stop, the inertia of the motor will not open the master contact immediately, ensuring that the cooling bed can operate normally without failing to stop. The situation down.
4. Conclusion
Industry affects the level of my country's economic construction. Metallurgical enterprises use PLC control systems in the electrical of continuous casting machines, which is conducive to achieving the unity of social benefits, economic benefits and ecological benefits. Therefore, it is necessary to realize the importance of using PLC control system in metallurgical continuous casting electrical, continuously optimize PLC system design, and promote the automation of metallurgical continuous casting electrical.
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