JPS595822B2 - Steelmaking arc furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc furnace for steelmaking, and its purpose is to be able to consistently perform processes from melting raw materials to refining in a vacuum or reduced pressure state using the same furnace body.
The purpose is to provide an arc furnace for steelmaking that can efficiently produce high-quality molten steel with little heat loss.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is a furnace shell, a trunnion shaft 2 protruding from the furnace shell,
3 is rotatably supported by a bearing 4 fixed on the foundation.

5 is a driven gear fixed to the trunnion shaft 3, 6 is a furnace tilting motor, 7 is a reducer connected to the motor, and 8 is a driving gear fixed to the output shaft of the reducer and meshed with the driven gear 5. be.

9 is an exhaust port provided in the furnace shell 1, and the exhaust port is connected to the flexible duct 1.
0 and vacuum exhaust equipment (not shown) through the exhaust pipe 11.
It is connected to the.

12 seals the furnace shell 1 airtightly with a seal 13 such as an O-ring.
The furnace lid 14 placed on the furnace lid is an electrode that is hermetically penetrated through the furnace lid by a seal 15. It is held by 17.

18 is an electrode cable, and 19 is an electrode lifting/lowering drive machine.

Reference numeral 20 denotes a raw material inlet provided in the furnace lid 12, and the inlet passes through a flexible duct 21 to a metering feeder 22 and an airtight door 23.
It is connected to a raw material hopper 24 equipped with.

25 is a melted raw material such as scrap and reduced iron.

Similarly, an auxiliary raw material inlet 26 provided in the furnace lid 12 is connected via a flexible duct 27 to an auxiliary raw material hopper 30 equipped with a metering feeder 28 and an airtight door 29.

31 is an auxiliary raw material such as ferroalloy and lime. Note that the airtight doors 23 and 29 are doors for charging raw materials or auxiliary raw materials into each hopper.

On the other hand, 32 is a gas inlet made of a porous plug provided in the furnace shell 1, and the gas inlet is connected to external inert gas and oxygen supply equipment (not shown) through a flexible pipe 33.

In addition, 34 is a tapping port that also serves as a slag discharge port provided in the furnace shell 1.
5 is an airtight door equipped with a seal 36; 37 is an airtight door 3 whose upper part is pivoted on a bracket 38 protruding from the furnace cover 12;
A lever 5 is fixed, and 3.9 is an air cylinder for rotating the lever.

Next, an example of a method of operating the furnace having the above configuration will be explained.

First, during the melting stage, each door is sealed and the exhaust port 9 is closed.
The inside of the furnace is maintained at a reduced pressure or vacuum state by being evacuated using a vacuum evacuation equipment, and the raw material 25 and the alloy iron are introduced into the furnace using the metering feeders 22 and 28, and the electrodes 14 are energized to perform melting.

As the melting progresses, the furnace body tilting drive motor 6 is operated in forward and reverse directions to swing the furnace body (furnace shell 1 and furnace lid 12) at a predetermined angle to stir the molten steel.

In addition, even when the furnace body is rocking, each hopper 2 fixed on the ground
4゜30 and the exhaust pipe 11 are connected to the furnace body by flexible ducts 10, 21, and 2γ, respectively, so that the vacuum state inside the furnace is maintained, and the electrode support 16 also tilts together with the furnace shell 1. Therefore, the electrode 14 can be moved up and down freely.

In other words, since melting is carried out under reduced pressure or vacuum conditions, the activation of boiling shortens the melting time and prevents the oxidation of the raw materials.This, combined with the fact that no air enters from outside the furnace, results in clean molten steel. Since oxidation of the ferroalloy is also prevented, the yield of the ferroalloy increases.

In addition, there is no heat loss to the furnace wall due to air convection inside the furnace,
There is no intrusion of cooling air, and raw materials can be continuously fed without opening the furnace lid 12, so thermal efficiency is extremely high.

Furthermore, since the raw material 25 can be continuously fed while being measured by the metering feeder 22, the temperature of the molten steel can be maintained within a predetermined range by feeding an appropriate amount of the raw material corresponding to the input power, and efficient melting can be performed.

Next, during the refining period, while maintaining the inside of the furnace in a reduced pressure or vacuum state, the furnace body tilting motor 6 is operated to tilt the furnace body toward the gas inlet 32 side as shown in FIG. Oxygen is blown through the gas blowing port 32.

When slag is generated, press the air cylinder 3 as shown in Figure 4.
9, open the airtight door 35, and tap the furnace body.
The slag is discharged from the tapping port 34 by tilting it to the side.

By opening the airtight door 35, the pressure inside the furnace becomes equal to atmospheric pressure, but after removing the slag, the airtight door 35 is closed to create a reduced pressure or vacuum state again. 31 into the furnace, and if necessary, inert gas such as oxygen or argon is blown into the molten steel through the gas inlet 32 with the furnace body tilted as shown in Fig. 3.
Remove slag as appropriate.

When the refining is completed, open the airtight door 35 in the same way as when removing the slag,
Steel is tapped from the tapping port 34 with the furnace body in the tilted state shown in FIG.

In other words, during the refining period, the furnace is in a vacuum or reduced pressure state except during slag removal, so the thermal efficiency is as good as in the melting period, and the oxygen and hydrogen content in the molten steel is reduced as a result of so-called vacuum degassing. .

In addition, by tilting the furnace body, inert gas such as oxygen or argon gas can be injected into the molten steel and exhausted from the exhaust port 9. It can promote vacuum degassing and improve the yield of easily oxidized alloys such as nickel and chromium, and can be easily applied even when melting stainless steel with a low carbon content.

Furthermore, by operating the furnace tilting motor 6, slag or molten steel can be easily discharged simultaneously and separately.

Additionally, since the furnace body is almost completely sealed during the melting and refining stages, soot and harmful gases are prevented from leaking out of the furnace, and noise associated with arc generation is also reduced.

Furthermore, the molten steel is stirred by the rocking of the furnace body, and the temperature of the molten steel is made uniform.

Furthermore, since vacuum degassing can be performed after melting using the same furnace body, there is less heat loss compared to the conventional method of transferring the melt to a ladle, etc., and performing vacuum degassing. occupies less space.

Although the above has described a furnace having a normal arc heating device using the electrode 14, the present invention provides a plasma arc heating device that is equipped with a plasma torch and a furnace bottom electrode and heats and melts raw materials using a plasma arc. It can also be applied to arc furnaces with

As explained above, according to the present invention, processes from melting raw materials to refining can be performed consistently in the same furnace body in a vacuum or reduced pressure state, and high-quality molten steel can be efficiently produced with less heat loss. be able to.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the steelmaking arc furnace according to the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIGS. This is a diagram equivalent to Figure 2. 1... Furnace shell, 2. Total: trunnion shaft,
4... Bearing, 5... Driven gear, 6...
...Furnace tilting motor, 7...Reducer, 8
... Drive gear, 9 ... Exhaust port, 10.
...Flexible duct, 12... Furnace cover, 13.
... Seal, 14 ... Electrode, 15 ...
... Seal, 16... Electrode support, 17...
... Electrode support arm, 20 ... Raw material inlet, 21.
... Flexible duct, 22 ... Measuring feeder, 23 ... Airtight door, 24 ... Raw material hopper, 26 ... Sub-material Inlet port, 27...
...Flexible duct, 28...Measuring feeder, 2
9... Airtight door, 30... Hopper for auxiliary raw materials, 32... Gas inlet, 33... Flexible piping, 34... - Steel tapping port, 35... airtight door, 36... seal.

Claims (1)

[Claims] 1. A furnace shell equipped with a tapping port with an airtight door and a gas inlet and tiltably supported on a foundation, and a furnace equipped with a raw material inlet and an auxiliary raw material inlet and placed on the furnace shell in an airtight manner. The lid constitutes a furnace body, a tilting drive device for tilting the furnace body, a vacuum depressurization equipment communicating with the furnace body, and a base supported on the furnace shell to move the material to be heated in the furnace body. An arc heating device for heating, a raw material hopper communicating with the raw material input port and equipped with a measuring device and an airtight door, and an auxiliary raw material hopper communicating with the auxiliary raw material input port and equipped with a measuring device and an airtight door. Steelmaking arc furnace 3