JPH0622536Y2 - Ladle refining equipment - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention prevents the increase of nitrogen in steel due to the invasion of outside air when refining molten steel in a ladle by agitating gas or gas and powder blowing. The present invention relates to a ladle refining device intended to do so.

[Conventional technology]

Recently, the necessity of producing high-purity steel has increased, and along with it, various secondary refining methods have been developed in the steelmaking process.
For example, reduction refining in which molten steel and slag in a ladle are agitated by gas injection, or injection in which refining powder is directly injected into molten steel together with an inert gas such as Ar as shown in Japanese Patent Publication No. 59-22765. Law etc.

In these methods, it is important to keep the molten steel surface to be stirred in a non-oxidizing atmosphere. To deal with this, it has been customary in the past to cover the ladle with a ladle lid for processing.

[Problems to be solved by the device] However, powder is blown into this lid to measure temperature, sample,
Since there is an opening for adding alloys and it is usually difficult to keep the top surface of the ladle completely smooth, a gap occurs between the ladle lid and the top surface of the ladle. However, if the treatment is performed in this state as it is, dust or fumes will substantially prevent the operation. Therefore, a dust collector is usually installed to collect dust inside the ladle lid.

Therefore, outside air is sucked into the ladle lid from each opening,
As a result, air oxidation and increase of [N] occur on the surface of the molten steel, which is a problem.

In order to deal with this, a method has been taken to prevent the invasion of outside air to some extent by performing treatment while blowing an inert gas such as Ar into the ladle lid. However, this method has a problem that it is economically disadvantageous because the seal is not perfect and a large amount of inert gas must be consumed.

[Means for solving problems]

The present invention has been made in order to advantageously solve the above-mentioned problems of the prior art, and is a ladle refining device for refining molten steel in a ladle while stirring the molten steel by blowing gas or gas and powder. In the above, in the ladle, there is a lance hole and a gas blowing hole for replacement in the upper part of the ladle, and a ladle lid that covers the opening of the ladle, a lower ladle lid provided around the ladle lid, and a ladle. A hood that covers the entire gap between the hood, a tube that is installed around the entire lower portion of the hood and is expandable by introducing gas, a pipe and a valve for introducing and discharging gas into the tube, and The ladle refining device is characterized in that it is fixed to the outer periphery of the ladle at a position facing the tube and is provided with a belt that is in close contact with the tube when the tube expands.

FIG. 1 is a sectional view illustrating the present invention.

In the drawing, 1 is a ladle containing molten steel 2, 5 is a ladle lid covering the opening thereof, and a lance hole 3 for blowing gas or gas and powder and a gas blowing hole 4 for replacement are provided. is there. Reference numeral 6 denotes a hood that covers the entire gap between the lower portion of the ladle lid 5 and the ladle 1. The entire circumference of the lower portion of the hood 6 is a tube 7 that is expandable by introducing gas, and gas is introduced into the tube 7. A pipe 10 and valves 11A and 11B for discharging are provided. On the other hand, a belt 14 is fixedly provided on the outer periphery of the ladle 1 at a position facing the tube 7, and the expansion of the tube 7 causes the tube 7 and the belt 14 to come into airtight contact with each other. The lid 5 and the lid 5 are sealed.

In addition, in the figure, 8 is a lance for injecting gas or gas and powder into the lance hole 3, 9 is a gas introduction pipe to the tube 7, 10 is a gas discharge pipe, and 12 is an alloy in the ladle 1. A chute 13 for charging the hood 6 is a hood that covers the outside of the hood 6 and is provided to guide the dust-containing gas leaking from the upper portion of the ladle 1 to the dust collector through the duct 13A.

Here, the hood 13 is for preventing the leakage of smoke from the gap other than the gap between the lower portion of the ladle lid 5 and the ladle 1, for example, the gap between the lance hole 3 and the lance 8, and seals the gap. However, the hood 6 may be directly connected to the duct 13A from the hood 6 without providing the hood 13. 15 is duct 1
It is a dust collection damper installed in 3A.

[Action]

Ladle 1 containing molten steel 2 is ladle lid 5 by crane and trolley
Will be transported directly below. After that, the ladle lid 5 is lowered by a winch or the like and placed on the upper surface of the ladle 1. Tube 7 at this time
Keeps valve 11B open and contracted.

Then, in this state, compressed gas is introduced from the pipe 9 into the tube 7 according to the present invention, the tube 7 is expanded and brought into close contact with the belt 14 fixed to the ladle 1. At this time, the exhaust pipe 10
Keep valve 11B closed.

At the same time, an inert gas such as Ar is supplied from the gas blowing hole 4 to replace the internal air.

In this case, it is more efficient to lower the lance 8 through the lance hole 3 and stop the lance 8 at a position where it is not immersed in the molten steel 2 and then replace the lance 8 with the lance 8 to reduce the size of the lance hole 3.

When the above preparations are complete, refining begins. During refining, preferably, the pressure of the atmosphere inside the ladle lid is measured, and the secondary refining process is performed while sucking the dust through the duct 13A with a dust collector so that the pressure becomes atmospheric pressure or slightly positive pressure.

Then, after the refining is completed, the dust collection damper 15 is fully opened to collect the dust while exhausting the compressed gas in the tube 7 to release the close contact between the tube 7 and the belt 14 fixed to the ladle 1, and the ladle lid. After raising 5, ladle 1 is transported to the next step.

Next, a concrete operation example of the present invention is compared with the conventional method, and its effect is shown in Table 1.

The conditions at this time were to take molten steel melted in a 300Ton converter to a ladle, and during that time, ferroalloy necessary for composition adjustment was also added. In the secondary refining process, to remove [S], 1500 kg / ch of pulverized coal was blown from the lance at a flow rate of Ar gas of 1.5 Nm ³ / min for 20 minutes.

[Effect of the Invention] As is clear from Table 1, since the air in the pan lid can be shut out almost completely by the present invention, the increase of [N] can be prevented. Furthermore, since there is no air oxidation, refining effects such as de-S [O] and de-O [O] capability improvement and [Al] loss reduction, as well as purging and sealing Ar gas can be greatly reduced. Extremely large.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view illustrating the present invention. 1 ... Ladle, 2 ... Molten steel, 3 ... Lance hole, 4 ... Gas injection hole, 5 ... Ladle lid, 6 ... Hood, 7 ... Tube, 8 ... Lance, 9 ... Gas Introducing pipe, 10 ... Gas exhaust pipe, 11A, 11B ... Valve, 12 ... Alloy injection chute, 13 ... Hood, 13A ... Duct, 14 ... Belt, 15
...... Dust collection damper.

Claims (1)

[Scope of utility model registration request] 1. A ladle refining device for refining molten steel in a ladle while agitating gas or gas and powder by blowing gas into the ladle, and having a lance hole and a gas blowing hole for replacement in the upper part of the ladle, and A ladle lid that covers the opening of the ladle, a hood that is provided around the ladle lid and covers the entire gap between the ladle lid lower portion and the ladle, and a gas installed around the lower portion of the hood. A tube that can be expanded by introduction, a pipe and a valve for introducing and discharging gas into the tube are provided, and
A ladle refining device, which is fixed to the outer periphery of a ladle at a position facing the tube, and is provided with a belt that is in close contact with the tube when the tube expands.