The Common Failure of Electric Induction Furnace

The common failure of electric induction furnace equipment during operation are as follows:

1. The Electric Induction Furnace System Does Not Respond at Startup

① The rectifier board is faulty;

② Over-current and over-voltage protection actions;

③ The main switch is not closed properly;

④ The control power potentiometer is damaged or disconnected;

⑤ The rectifier control power supply is broken.

2. Only the Direct Current Voltmeter Has Instructions, Others Have No Response

① The inverter board and inverter circuit are faulty;

② The inverter power supply fails. There is no 220V power supply for the inverter pulse.

Note: When the power phase voltage of the induction furnace is higher than 240V, it is easy to damage the control power transformer.

3. The Electric Induction furnace Cannot Be Started Successfully When Starting, and the DC Current Is Large, and DC Voltage Is Low (Tens of Volts)

① There is a direct short circuit phenomenon in the inverter part (such as a short circuit between copper bars, breakdown of the electric heating capacitor, etc.)

②There is a problem with the inverter control circuit and the signal-taking part (open circuit or short circuit)

③ There are multiple damages to the inverter thyristor (measured with multimeter R×1 file).

4. There Is Occasional Frequency Sound When Starting the Electric Induction furnace, But Each Instrument is swinging, Or Each Instrument Swings After Starting After the Pin Increases the Power, Overcurrent Or Overvoltage

① Defective inverter control board.

② Improper adjustment of the minimum TF working angle.

③ The water cable is broken or the cable screw is loose.

④ The induction melting furnace is short-circuited or grounded, and the pressed circuit may be a short-circuit on the output side.

⑤The thyristor is defective.

5. When the Main Circuit Is Closed, It Will Trip at the Beginning of the Air, or Over-current Protection. Even If It Is Normal by Chance, There Will Be Abnormal Sound. 

① Generally, a certain rectifier thyristor is broken down.

②The performance of the thyristor decreases, or it loses its blocking ability in a certain direction and becomes a diode.

③ There is a short circuit in the rectifier circuit.

6. The Electric Induction Furnace Can Be Started, But the Sound of the Reactor Is Dull. The Meter Swings Accidentally and the DC Voltage Rises to 500V

①The main circuit lacks phase (generally, the constant power board will not have DC voltage output when the phase is lacking);

②The control circuit lacks pulse;

③One of the rectifier thyristors cannot be touched or maintained, and the gate is open-circuited or short-circuited.

7. The Electric Induction Furnace can start, but the ratio of the intermediate frequency voltage to the DC voltage Is large, the voltage Is low, and the DC current Is large

① The breakdown of a bridge wall of the inverter thyristor;

② A certain thyristor does not work (when judging, you can directly use the multimeter to measure the tube voltage drop when working at low voltage. If there is no voltage, it may break down, and pay attention to whether the adjacent bridge wall does not work. For a single-tube bridge wall, if the positive and negative voltages are the same, the related circuit can be checked. There are two cases for the double-two thyristor series circuit. The same as the single-tube circuit, there is generally no pulse between the two tubes, and the voltage is positive and negative. It means that the thyristor that bears the forward voltage is not working, check if there is a control pulse, if the polarity is normal, and if the gate is open circuited).

③The inverter control circuit is abnormal.

④The load does not match, or the minimum TF angle is set improperly.

Note: The breakdown of the KK SCR will cause the secondary parallel diode of the inverter pulse transformer to also break down, which will cause the inverter pulse to have no output. Pay attention to check when replacing the new SCR. This item will also cause reverse change the bridge and three walls to work.

8. The DC Voltage of the Intermediate Frequency Furnace Is Unstable, Or A Certain Range Is Unstable, the Meter Swings, and the Reactor Has A Broken Wire Sound

① The trigger pulse is unstable;

② The characteristics of the rectifier thyristor are poor;

③ Poor contact exists in the main circuit;

④ The PI regulator oscillates due to problems;

⑤ The control circuit leads to interference.

9. The Intermediate Frequency Voltage of the Electric Induction Furnace Is Unstable, Eliminating the Unstable DC Voltage

① Defective inverter thyristor;

② The inverter pulse is unstable;

③ The minimum TF angle is set improperly;

④ Poor contact of the corner load circuit or igniting and connecting;

⑤ The PI regulator has problems with oscillation;

⑥ The control circuit interferes.

10. The Power of the Electric Induction furnace Cannot Be Adjusted up (Without Rectifier and Inverter Faults)

①The load is not matched, too light or too heavy (the load circuit can be adjusted);

②For the circuit users of the crimped connection method, the user does not use the crimped method to connect;

③The output wire loss is too large.

11. Normal Start the Induction Melting Furnace, the Voltage Rises to A Certain Level, and the Restart Phenomenon Suddenly Occurs.

① The minimum angle adjustment is too small;

② The circuit board frequency is not adjusted properly.

12. The New Electric Induction Furnace or Cool Induction Furnace Can Start Well and Can Work Normally. When the Intermediate frequency furnace Is Hot or Full of Molten Steel, the Induction Furnace Will Stop and It Will Be Difficult to Start.

The main reason is that the circuit board frequency adjustment is inappropriate and the angle is too small.

13. The Electric Induction Furnace Equipment Can Be Started, Over Current Occurs When Power Increases

① The intermediate frequency transformer is damaged or defective.

② The inverter pulse transformer is damaged or defective.

③ Inverter SCR soft breakdown or intermittent.

④ Leakage of the primary series capacitor of the intermediate frequency transformer.

⑤ Soft breakdown of the electric heating capacitor, poor insulation of furnace ring or copper bar, grounding, or slight short circuit.

If you are interested in electric induction furnace, please mail at marketing2@hanrm.com for your solution.

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6300KVA Electric Arc Furnace Solution

1. Overview

The 6300kVA electric arc furnace is designed and manufactured according to GBl0067.14 "Basic Technical Conditions for Electric Heating Equipment". It is used for alloy smelting, the furnace body is fixed, one tap nozzle and one slag outlet are included.

2. Mechanical Structure Description

The 6300kVA high-titanium slag electric arc furnace is a fixed furnace body. The top of the fume hood is charged, and the tapping nozzle is in the form of tapping. It consists of the following parts: furnace shell, water-cooled furnace cover, electrode lifting device, high current circuit, hydraulic system, Water cooling system, feeding device, transformer, high voltage cabinet, low voltage electrical control system, etc.

3. Furnace

The furnace body includes the furnace shell, the tapping nozzle, and so on.

The furnace shell is welded with a 16mm Q235 steel plate. To increase the rigidity, ribs are provided on the outside of the furnace shell. A tapping nozzle is opened on one side of the furnace shell, and the furnace shell is lined with refractory materials.

4. Water-cooled Furnace Cover

The water-cooled furnace cover is a device for collecting smoke and dust in the furnace. It can be placed on the furnace shell or on the furnace mouth operating platform. The water-cooled furnace cover is made of 20g seamless steel pipe. The entire furnace cover must be well insulated to the ground, generally not less than 0.2MΩ. There is a flue on the top of the hood, and the flue is partially cooled by water. The water-cooled furnace cover is equipped with three-electrode holes, feeding holes, and observation holes.

5. Electrode Lifting Device

The electrode lifting device is composed of an electrode arm, a column, an electrode clamping mechanism, an electrode lifting hydraulic cylinder, a bracket, a guide wheel, and so on.

The electrode arm is a conductive cross arm, which is a fully water-cooled box-shaped structure made of copper-steel composite plates. The side surface of the front section of the side-phase cross arm and the front section of the middle-phase cross arm are respectively equipped with electrode clamping mechanisms. The electrode clamping adopts the form of disc spring, that is, the electrode is clamped by the disc spring during normal operation, and the disc spring is compressed by the hydraulic cylinder when the electrode is released.

The conductive part is insulated from the ground once, that is, the cross arm and the column are insulated by insulating cloth plates. The electrode distribution circle can be adjusted ± 50mm。

The column is a box-shaped central member welded by steel plates. It is installed upright in a mechanism equipped with guide wheels, and the guide wheels are in close contact with the column. An electrode lifting hydraulic cylinder is installed in the hollow column. The upper part of the hydraulic cylinder is connected with the electrode column, and the lower end is connected with the bracket. The electrode lifting hydraulic cylinder pushes the column to raise the electrode arm and electrode. When it descends, it is completed by its own weight. The connection between the column and the cross arm is through the intermediate adjustment plate, so that the connecting surface of the cross arm and the column is both an insulating surface and a separate surface, so that not only the adjustment of the cross arm is convenient, but the insulation between the column and the cross arm is also more reliable.

The electrode clamping mechanism is composed of an electrode clamping disc spring, connecting rod, brake, hydraulic cylinder, etc. The hydraulic cylinder and the disc spring realize the clamping and loosening of the electrode through the connecting rod and the holding brake. When the electrode is loosened, a hydraulic cylinder drives and compresses the disc spring to realize the electrode loosening. The bracket is used to connect the electrode lifting mechanism and the furnace cover lifting and rotating mechanism, so that the load of the electrode lifting mechanism is supported on the rotating frame of the furnace cover lifting and rotating mechanism through the supporting plate and the pin shaft.

During the lifting and lowering of the electrode, the guide wheel acts as a guide through the column. At the same time, in the process of furnace debugging, adjust the front, rear, left and right positions of the column by adjusting the position of the guide wheel to adjust the diameter of the electrode distribution circle.

6. High Current Circuit

The high-current line consists of connecting copper bars at the second outlet of the electric furnace transformer, compensators, copper pipes through the wall, cable joints, large cross-section water-cooled cables, conductive cross arms, electrode clamps, graphite electrodes, and brackets.

Copper bolts or stainless steel bolts are used to connect the water-cooled cable to the copper pipe through the wall and the conductive cross arm. Through-wall copper pipes, water-cooled cables, and conductive cross-arms are cooled by water.

7. Hydraulic System

The pressure of the hydraulic system is 12MPa, and the working medium is water-glycol. The system includes hydraulic pressure source and various control valves, accumulator tank, accumulator, pressure relay, etc. The hydraulic source has two pumps, and the liquid storage tank is equipped with temperature and liquid level control instruments.

8. Cooling Water System

The cooling water system consists of pressure gauges, thermometers, shut-off valves, water distributors, return tanks and pipelines.

The cooling water source is connected to the main water inlet pipe of the workshop, the pressure is not less than 2×lO5Pa, and the water temperature is not more than 35°C. The device is equipped with water pressure and water temperature alarms, when the water pressure is lower than the set value or the water temperature is higher than the specified value, an alarm signal will be issued.

The cooling water device is located in front of the furnace on the side of the transformer room wall, and is cooled with the furnace body through pipelines (including hoses)

The parts are connected for cooling of the furnace body, furnace cover, conductive cross arm, water-cooled cable and copper pipe through the wall.

The water for the transformer oil-water cooler is supplied by the high-level cooling water tank, and the return water is connected to the workshop return water network.

9. Compressed Air System

The system consists of pneumatic triple parts, distributors and solenoid valves.

10. Feeding Device

The feeding device is composed of a hopper, an air cylinder, a vibrating feeder, and a feeding tube.

11. Electrical Equipment

The electrical equipment mainly includes a high-voltage power supply system, furnace transformer, low-voltage power supply system, low-voltage electrical control system, and electrode lifting automatic regulation system.

Looking for an electric arc furnace or any relevant spare parts, please mail at marketing2@hanrm.com, our tech engineer will make a suitable solution for you.

Arc Continuous Caster

The arc continuous caster is also called the full arc continuous caster. The mold of the arc continuous caster is arc-shaped, and the secondary cooling device is in a quarter of the arc to form an arc-shaped casting billet in the mold. During the downward movement of the arc-shaped roller table, it is cooled by spraying water until it is completely solidified. After being fully solidified, the cast billet enters the straightening machine at the horizontal tangent point and then is cut to length.

The arc continuous caster is composed of ladle turret, tundish and conveying device, crystallizer and vibrating device, secondary cooling device, multi roller tension leveler, dummy bar and its storage platform, dummy bar removal device, cutting and collecting device, billet cutting equipment, etc.

1. Steel Drum Rotating Table

The ladle filled with molten steel transported from the steelmaking furnace is hoisted on the support frame by a crane, and then the support frame is rotated 180° above the intermediate tank to inject the molten steel into the intermediate tank. After pouring, rotate 180° to the receiving position, and hoist the empty can. When multiple furnaces are continuously poured, two steel buckets can be placed on the supporting frame at the same time. After one bucket of molten steel is poured into the intermediate tank, the supporting frame rotates 180°, and the other bucket of molten steel reaches the top of the intermediate tank.

2. Tundish

Tundish is an intermediate vessel between steel barrel and mould. The molten steel is injected into the mould from the tundish. The tundish is composed of tank body, tank cover and nozzle stopper.

3. Crystallizer

There are two types of crystallizers: curved and straight, which can be divided into three types: integral type, sleeve type and combined type. The width and thickness of the inner cavity of the combined mold can be adjusted. The crystallizer is composed of inner wall, outer shell, cooling water circuit and supporting arm. The material of the mold is mainly copper and copper-based alloys (phosphorus deoxidized copper, silver-containing copper, etc.). In order to increase the abrasion resistance of the inner wall, a thin layer of chromium or nickel is often plated. The length of the crystallizer is usually 700-900mm, the crystallizer taper is generally 0.5% to 0.9%, and the round billet crystallizer taper is 1% to 1.2%.

The vibration device of the mold generally adopts small amplitude and high-frequency vibration parameters, the amplitude is not more than 4mm, and the frequency is more than 150 times/min. The purpose of the vibrating device is to obtain a good lubrication condition for the inner wall, reduce friction, and prevent the molten steel from adhering to the inner wall.

4. Secondary Cooling Support Guide

The function of the secondary cooling supporting and guiding device is: direct water spraying can be used to cool the casting billet, supporting and guiding the casting billet and the starter chain, and preventing the deformation of the cast billet and the deviation of the starter chain. The secondary cooling guide section of the billet continuous caster is relatively simple. The slab caster adopts a close-packed roll structure with small diameter and small roll spacing. The guide section and the tension leveler are made into several fan-shaped sections, which is convenient for maintenance, replacement and arc alignment.

5. Straightening Machine

The drawing straightening machine is called a straightening machine for short. It is used to pull the dummy bar chain and the slab condensed with it out of the mould continuously and straighten the slab. It is liquid core tension straightening to use multi roll tension straightener to make the casting billet which is not completely solidified enter the tension straightener, which can improve the drawing speed and productivity.

The stretch-straightening machine of the billet continuous caster generally adopts a 5-roller pneumatic or hydraulic pressing type, the slab continuous caster adopts a multi-roll stretch-straightening machine, and the bloom and round billet adopt a single-frame stretch-straightening machine that can be replaced as a whole.

The starter chain is the "live bottom" of the crystallizer. The lower mouth of the crystallizer is blocked, and some scrap steel plates are placed on the starter head, so that the casting billet and the starter head are firmly connected, and the tail of the starter chain is clamped in the tension leveler. In the machine. After the start of casting, the starter chain head gradually condenses with the billet. After starting to draw the billet, the tension leveler forcibly pulls the starter chain and the steel billet connected to it from the mold until the billet is straightened and the starter chain is taken off, and then it leaves the continuous casting production line for storage.

6. Cutting equipment

A Shearing machine or flame cutting machine can be used to cut the casting billet. For billets with a cross-section of no more than 200mm×200mm, shears are generally used, and flame cutting machines can also be used for long-length billets. For square billets, round billets and slabs with a cross-section greater than 200mm×200mm, flame-cutting machines are generally used. There are electric and hydraulic shearing machines, and the shearing machine with a shearing force greater than 5000kN generally adopts the hydraulic type. The fire-burning cutting equipment consists of a cutting mechanism, a synchronization mechanism, a return mechanism, an end face detector, a fixed-length mechanism, and an oxyacetylene pipeline system. 

Advantage

The arc continuous caster is arranged in the quarter arc range, so its height is lower than that of the vertical bending continuous casting machine. This feature makes its equipment lighter, lower investment, and equipment installation and maintenance. Convenience.

Due to the low height of the equipment, the cast slab bears relatively small hydrostatic pressure during the solidification process, which can reduce internal cracks and segregation caused by the deformation of the bulge, which is beneficial to increase the drawing speed and improve the quality of the cast slab.

Industrial Technology Level

Commonly referred to as continuous casting technology is a variety of technologies targeted at arc continuous casting machines. The industrial technology level reached by the arc continuous casting machine can be summarized as follows:

1) Casting machine production capacity: The single production capacity of modern large-scale slab casters is generally 2 to 2.5 million t/a. The American Harper (LIV/Indiana Harbor) plant set an annual output of 3.05 million t/a in 1987. . The single production capacity of the bloom caster can reach 800,000 to 1 million t/a. The single production capacity of the billet multi-strand continuous caster can reach 600,000 to 800,000 tons.

2) Casting machine operating rate: generally above 80%, and more advanced casting machines can reach 85-90%.

3) High-speed casting: The general drawing speed of the slab continuous casting machine is 1.2～1.8m/min. The newly built No. 5 machine of the Fukuyama Plant of Japan Steel Pipe has created the highest record of 3.0m/min.

4) Multi-furnace continuous casting: Generally, the number of continuous casting furnaces is 4-6 furnaces on average, and there are also more than 10 furnaces. The twin-strand slab caster of the Porttalbot Plant of the British Steel Union (BSC) set a record of 300 continuous casting furnaces (with a molten steel volume of 102,000 tons) in 1987. The single-strand slab caster of American Steel's Gary Plant set a record of 329 continuous casting furnaces. In January 1988, the monthly output reached 318,500 tons.

5) The range of slab cross-section dimensions actually produced by the casting machine, mm:

Slab 125×650～220×2720 (strip steel, welded pipe billet), 350×1300

150×1000～320×1600 (thick plate), 310×2500

Bloom 200×200～600×670 (rod, shape, wire)

φ230～φ450, 560 octagonal (tube) shaped blank, 480×420×720 (rail beam)

Billet 80×80～145×145 (wire)

100×100～240×240 (rods, shapes, materials)

φ115～φ210 (pipe, rod, material)

6) Extensive use of computer technology: The production process and production management of modern continuous casting machines are automatically completed by computers.

Installer

The arc continuous caster has established a complete and accurate measurement control network before installation. The installation procedure can be determined according to the conditions of the construction site, the sequence of equipment arrival, and the requirements of the construction period.

The more reasonable installation procedure is to take the tension leveler as the positioning equipment and use its tangent point roll for positioning. Firstly, install the tension leveler curve section, align the tangent roll axis of the curve section with the transverse datum line, and the top elevation of the tangent roll is ± 0 (top elevation of discharge roller). After positioning the curve section of the tension leveler, it can be divided into two main operation lines for installation at the same time. One operation line is carried out from bottom to top in the reverse direction of casting flow, and the sequence is: lower frame of secondary cooling device → upper frame → upper beam → segment replacement device → segment → mould vibration bench and transmission device → transition segment → mould. The first line is the straight section of the tension leveler, and then the output roller table, dummy bar stand, dummy bar removal equipment and cutting equipment.

The secondary cooling device is the main part of the continuous casting machine. The complete set of equipment is located in the cooling room. After the fan-shaped section is installed, a large number of pipeline projects in the cooling room will be constructed immediately. According to the drawings, choose a reasonable construction procedure: equipment cooling water pipes, spray water pipes, Sector hydraulic pipes, dry oil lubrication pipes.

After the installation of the curved section and the straight section of the straightening machine, piping construction should be carried out. The sequence is compressed air pipe→hydraulic pipe→spray cooling water pipe→equipment cooling water pipe.

The hydraulic station matched with the continuous caster and the water distribution chamber of the secondary cooling device are complicated in the system and large in engineering volume, which must be carried out at the same time as the continuous caster.

The ladle rotating platform and tundish car traveling device on the casting platform should also be constructed in parallel with the continuous caster.

Looking for the continuous caster or relevant spare parts, please mail at marketing2@hanrm.com.

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