Short Net and Electrical Control of LF Ladle Furnace
LF (ladle furnace) furnace is refining equipment developed in the early 1970s. Because of its simple equipment, low investment cost, flexible operation and good refining effect, it has become a rising star in the metallurgical industry and has been widely used and developed. The steel processed by the LF furnace involves almost all steel grades from special steel to ordinary steel. Different process operation systems can be adapted according to the needs of quality control in production. Among various secondary refining equipment, the LF furnace has high comprehensive cost performance. As a complex smelting system, the temperature in the refining furnace is affected by various factors. The physical parameters, such as EAF, are affected during ladle tapping. The length of transportation time and the amount of argon blowing also affect the molten steel temperature. Alloy, circulating cooling water, flue gas, soot, electrode and transformer constitutes the basis of the temperature model of the whole refining furnace.
1. Main Functions of LF Ladle Refining Furnace
1.1 Arc heating and heating
1.2 Fine-tuning the composition of molten steel
1.3 Desulfurization, deoxidation, degassing, and removal of inclusions
1.4 Uniform molten steel composition and temperature
1. 5 Change the shape of inclusions
1.6 As buffer equipment for the converter and continuous casting, it ensures the matching production of the converter and continuous casting.
2. Working Process Flow of a Steel Refining Furnace
Hoist the ladle to the ladle car → connect the argon blowing pipe and test the gas → drive the ladle car to the heating station → the furnace cover and the electrode fall in place → temperature measurement and sampling to determine the heating system and fine-tuning of the composition → add slag and alloy materials → power transmission for heating and refining →Temperature measurement and sampling →The furnace cover and the electrode are raised →the ladle car is driven out of the heating station →the wire is fed →the heat preservation agent is added →the soft argon blowing and gas cleaning →the argon blowing pipe is disconnected and the ladle is lifted out.
3. Short net
The secondary bus equipment from the second end of the transformer to the electrode is generally called the short net. The electrical parameters of the short network play a decisive role in the normal operation of the refining furnace. The productivity, lining life, power loss and power factor of the refining furnace largely depend on the selection of the electrical parameters of the short network. The short net of a steel refining furnace is mainly composed of the water-cooling compensator, water-cooling cable, conductive cross arm, electrode, electrode holder and other components. The short network has the following characteristics:
3.1 The current is high.
3.2 Short length.
3.3 Complex structure.
3.4 Poor working environment.
4. Electrical and automatic control
4.1 High voltage electric control system
It is used to switch on and off the power supply at the primary side of the transformer of the refining furnace, and fully consider the suppression of high-order harmonics and the influence of various Overvoltage on the insulation and high-voltage components of the furnace transformer. It is mainly composed of the incoming cabinet, furnace transformer vacuum switch cabinet, and protection device.
1) The incoming cabinet includes an isolating switch, which is mainly used to isolate the power supply for safe maintenance; In addition, it also includes the voltage transformer to complete power metering and protection; The zinc oxide arrester device can prevent the impact of operating overvoltage on the voltage transformer when the vacuum circuit breaker is powered off.
2) One vacuum switch cabinet, including circuit breaker (Siemens) handcart and current transformer. The circuit breaker adopts the spring operating mechanism, which can be operated remotely to complete the connection and disconnection of the transformer power supply; The closing circuit of the vacuum circuit breaker adopts anti tripping device, which overcomes the arc re-ignition caused by the reverse recombination and separation of vacuum contact, and effectively prolongs the service life of the contact. The vacuum switchgear also includes the microcomputer integrated protection device, which is used for electric quantity measurement and current quick-break protection, inverse time limit overcurrent protection, monitoring and data acquisition (in which the active and reactive electric degrees have pulse output), low voltage protection and transformer protection.
3) The protection device includes the zinc oxide arrester and resistance-capacitance absorption device, which can effectively prevent the possible harm of operation overvoltage and surge overvoltage to the insulation of the transformer and voltage transformer.
4.2 Low voltage electric control system
The low-voltage power supply comes from the second section incoming line of the converter in the distribution room of the central control building in the steelmaking new area. The rated current of the circuit breaker is 1000A. MCC provides power and control power for the hydraulic system, ladle turret, feeding system, argon blowing system, wire feeding system, temperature measurement and auxiliary system and other refining furnace equipment. With the help of PLC, it can realize the accurate control of relevant equipment to meet the process requirements. The system control circuit adopts the isolation transformer, which is fed to each system by each shunt automatic switch to ensure the stability and reliability of the control circuit.
4.3 Instrument control system
The instrument control system mainly completes the measurement of molten steel temperature; Measurement of cooling water flow, temperature and pressure; Argon flow and pressure measurement, feeding and weighing. The instrument control system adopts the integrated design of electrical, instrument and computer, which is composed of instrument, PLC and upper computer LCD; The main feature is the combination of upper computer LCD display and instrument display, which is convenient for operators to observe. It can transmit and collect data related to processing production. In case of failure and alarm of all detected process parameters, the alarm will be displayed on the LCD screen of the upper computer.
4.4 Automatic control system
The automation system consists of a set of electrode regulation PLC control systems, a set of LF furnace body PLC control systems, a feeding PLC control system, two computer operation stations, and an industrial ethernet. It has the function of communicating with the secondary station, and enough expansion space is reserved.
The most critical thing is the electrode lifting PLC control station, which is equipped with corresponding AI / AO, di / do modules and communication modules for on-site arc current, arc voltage and corresponding process information, acquisition of electrodeposition status, system control and adjustment. The input and output of PLC are isolated. The electrode lifting adjustment system is a relatively independent PLC system. In case of LAN failure, it can still complete the function of automatic electrode lifting independently. At the same time, it is connected with the primary LAN, which can easily communicate with other nodes on the network. The purpose of electrode lifting control is to adjust the distance between the end of the electrode and the steel liquid level through the proportional valve of the hydraulic station, so as to ensure that the state variable of electricity in the smelting process can track the optimized input power set point.
5. Main Equipment and Functions
1. Electrode lifting device
The electrode lifting column is a “rhombic (V-shaped)” member welded with steel plate and seamless steel pipe, and an independent column lifting oil cylinder is installed in the inner cavity.
2. Water cooling system
Provide corresponding cooling water for each cooling point of the equipment to ensure the safe and reliable operation of the equipment. Send the detected temperature, water pressure and flow signals to PLC. When the pressure is too low, the temperature is too high and the flow is too low, there will be audible and visual indications and alarms in the control room. All water pipes of the equipment are connected with threads.
3. Hydraulic system
1) The high-pressure piston pump of the pump station adopts the original imported constant pressure variable piston pump, and its configured driving power is about 30kW; There are three sets in total, two for use and one for standby.
2) Three imported electro-hydraulic proportional valves are adopted for the three-phase electrode lifting regulation of the valve station; The furnace cover lifting system adopts dn10 three-position four-way electro-hydraulic valve and is equipped with a double one-way throttle valve (with hydraulic lock function); The electrode loosening control system is controlled by dn6 two-position four-way electro-hydraulic valve.
3) The oil tank is equipped with a temperature controller (high/low temperature) and a liquid level gauge to send a signal to the liquid level (high/low), which is used to alarm and send a signal to the system. At the same time, it is equipped with a circulating filtration cooling/ heating system and other accessories; The hydraulic medium is flame retardant water glycol, and the oil tank and pipeline are made of stainless steel.
4) The main function of the accumulator device is to raise the electrode and furnace cover to a certain height in case of an accident, so that the ladle can be opened back to the turntable, and also balance the pressure of the hydraulic system; In addition, the accumulator is equipped with pressure protection and cut-off unloading device.
4. Refining furnace transformer
The transformer provides thermodynamic conditions for the smelting process of the ladle refining furnace. The main equipment includes transformer body and various accessories, oil conservator, Mr on-load voltage regulating switch and oil conservator, plate oil-water cooler and its operation box.
Customized Short Net and Electrical Control of LF Ladle Furnace
We can design and manufacture the short net and electrical control of LF ladle furnace according to the client’s required capacity, working hours, power supply, raw materials, and other related parameters. It can also be matched for users who already have a ladle furnace.
We can provide foundation layout and layout drawings
We will send engineers to your factory to install and debug machines and provide reliable after-sales service.
Competitive price and excellent quality
Our machines are easy to operate and maintain
Products can be customized according to different need
Production capacity can be adjusted according to customer requirements
Low energy consumption