JPH07150225A - Rh degassing refining apparatus - Google Patents

Abstract

PURPOSE:To provide an RH degassing refining apparatus, in which the reflexing rate of molten steel is drastically increased and the removal effect of nonmetallic inclusion in the molten steel can drastically be improved by drastically reducing the flowing-in resistance of the molten metal from a ladle. CONSTITUTION:In an uptake immersion tube in the RH degassing refining apparatus for blowing up the molten steel by inserting gaseous argon, an expanding part 11 for immersing the tip part into the molten steel and expanding the inner diameter at a part of the lower end 10 downward, is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RH degassing and refining apparatus, and more specifically, it improves the structure of an ascending dip pipe for blowing up molten steel by interposing argon gas among the dip pipes to improve the structure. RH that greatly reduces the inflow resistance of molten steel from the ladle, greatly increases the flow rate of molten steel in this way, and greatly improves the effect of removing non-metallic inclusions in molten steel.
Related to degassing and refining equipment.

[0002]

2. Description of the Related Art At present, so-called high-grade steel, low-alloy steel, and special steel produced by converters and electric furnaces are vacuum-refined in some form. Also, this vacuum refining is widely applied to the field of ordinary steel in addition to the treatment of high-grade steel, and it brings advantages such as alloy iron saving and quality improvement, and the treatment amount is greatly increased. There is.

Generally speaking, the vacuum treatment itself was initially started with the aim of preventing hydrogen-like defects in large cast and forged steel products by vacuum casting, degassing of steel, etc. However, when the RH method suitable for mass production of rolled products was developed and put into practical use, the spread of vacuum processing has been accelerated, and in particular, the vacuum processing has become widespread in combination with a pure oxygen converter, and has reached the present.

Further, in the RH method, molten steel in a ladle is sucked into a vacuum vessel in a vacuum vessel, brought into contact with a vacuum to perform degassing and other vacuum treatments, and vacuum refining is performed by circulating such molten steel. It is a thing. The feature of the RH method is the mechanism for sucking molten steel. This mechanism involves blowing argon gas as a carrier gas into one of the two ascending dip tubes, and then using the principle of a gas lift pump with this argon gas. Is a mechanism for sucking up.

In the RH method, molten steel is sucked up into a vacuum vessel by an ascending dip tube, and after the vacuum treatment, the molten steel is returned from another dip tube into a ladle, and this circulation operation is repeated. The RH method can achieve degassing functions such as decarburization, degassing, deoxidation, and denitrification, and multifaceted effects such as floating of inclusions, but these refining effects include circulation, stirring, and
Since it is based on mixing, conventionally, in the RH method,
The following improvement measures have been proposed in order to increase the flow rate of molten steel, but there are the following problems.

That is, in Japanese Patent Laid-Open No. 2-247329, the molten steel ascending portion and the descending portion of the immersion pipe are integrally formed and separated by a partition wall, and the molten steel descending portion cross sectional area is made larger than the ascending portion sectional area. , An RH degassing refining device with an increased recirculation flow rate has been proposed. However, in order to increase the pipe diameter in this way, it is necessary to modify the lower tank of the RH degassing and refining equipment, etc. Also, since the amount of refractory used is large and it is extremely disadvantageous in terms of cost, it is economical. There are many problems.

Also proposed is an RH degassing refining apparatus in which a molten steel inflow port at the lower end of an ascending dip tube is entirely covered with a heat resistant filter. With this device, all of the molten steel that is recirculated can be filtered, but the inflow resistance of the molten steel increases due to the filter, and due to this pressure loss, the recirculation flow rate is 10 to 20.
%, And the effect of the RH method cannot be fully exerted.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks, and more specifically, in an RH degassing and refining apparatus, an ascending dip pipe for blowing up molten steel with an argon gas blown in between. The structure is improved to reduce the inflow resistance of molten steel and increase the recirculation flow rate so that the effect of RH degassing can be fully exerted. We propose an RH degassing vacuum refining device that can be effectively removed.

[0009]

That is, the present invention provides R
In the H 2 degassing and refining apparatus, an ascending dip tube for blowing molten steel with argon gas interposed is characterized in that a part of the inner diameter of the lower end portion is enlarged downward so as to dip it in the molten steel.

Further, at the lower end portion which expands downward,
It is characterized in that a filter for removing non-metallic inclusions in the molten steel is attached to the tip thereof.

Therefore, the construction and operation of these means will be described in more detail with reference to the drawings.

FIG. 1 is a vertical sectional view of an ascending dip tube of an RH degassing vacuum refining apparatus according to an embodiment of the present invention, and FIG. 2 is an RH degassing vacuum according to another embodiment of the present invention. FIG. 3 is a sectional view of an ascending dip tube of a refining apparatus, and FIG.
It is explanatory drawing which shows the principle of H degassing vacuum refining apparatus, FIG.
FIG. 4 is a vertical sectional view of an ascending dip tube of the RH degassing vacuum refining device shown in FIG. 3.

First, in FIG. 3, reference numeral 1 generally indicates RH.
A part of the degassing vacuum refining device is shown in principle. In this refining device 1, a vacuum container 2 is arranged at the upper part, and the lower ends of two dipping pipes 5 and 6 are immersed in the molten steel 4 in the lower ladle 3. The vacuum container 2 is sucked in the direction of the arrow and the inside is kept in a vacuum state.

Argon gas 7 is supplied from the vicinity of the tip of one of the ascending dip pipes 5 and 6, and the molten steel 4 is sucked into the vacuum container 2 under the interposition of the argon gas 7. The molten steel is blown up in the vacuum vessel 2, stirred, mixed and brought into contact with a vacuum to undergo a degassing reaction such as decarburization and deoxidation, and non-metallic inclusions present in the molten steel are floated and separated. Then, the molten steel 4 is refined. The molten steel that has been subjected to the predetermined vacuum refining descends from the other descending dip pipe 6 toward the ladle in the direction of the arrow, and while this operation is repeated, the molten steel 4 is refluxed, stirred and mixed, degassed and Effects such as floating of inclusions can be achieved.

Next, in the RH degassing vacuum refining apparatus having the above-mentioned structure, at least the ascending submerged pipe 5 among the two submerged pipes 5 and 6 provided so as to project downward from the bottom of the vacuum container 2 thereof. Instead, a part thereof is attached to the lower end portion 10 of the ascending dip tube having the structure shown in FIG.

That is, the ascending dip tube 5 usually has an upper end portion 51.
And a lower end portion 52, and the lower end portion 52 is a flange joint 5
It is attached to the upper end portion 51 via 3. Instead of the lower end portion 52 of the rising immersion pipe, the lower end portion 10 of the rising immersion pipe is attached via a flange joint 53.

More specifically, the lower end 10 is shown in FIG.
As shown in FIG. 3, the inner diameter is enlarged downward, and an enlarged portion 11 is formed near the tip of the lower end portion 10. The enlargement part 11 is shown in FIG.
It is usually preferable to configure by enlarging it on a truncated cone as shown in, but even without such a configuration, if the inner diameter is enlarged toward the tip, the inflow resistance of the molten steel can be considerably reduced, It can be composed of either one.

As described above, when a part of the lower end portion 10 of the ascending dip pipe is constituted by the enlarged portion 11 which expands downward toward the tip, the circulating flow rate of the molten steel 4 is such that the inflow resistance of the molten steel is reduced or reduced. Combined with the above, the inner diameter of a part of the lower end portion 10 of the ascending dip tube 5 is increased by about 10% or more as compared with the conventional example, but the ascending dip tube 5 is expanded over the entire length. No, there is no need to improve other equipment.

That is, the effect of immersion refining by the RH system, that is, the degassing effect and the floating of inclusions are based on the circulation, stirring, mixing, etc. of molten steel. Therefore, it is extremely important to increase the recirculation flow rate, and the refining effect is greatly improved by this increase.

Further, as the inner diameter of a part of the lower end portion 10 of the ascending dip pipe is enlarged, a heat resistant filter 12 can be provided at the molten steel inflow port of the enlarged portion 11 as shown in FIG. The heat resistant filter 12 can be provided on the entire surface of the molten steel inflow port of the expanded portion 11, but the filter 12 is provided by squeezing downward at the tip of the expanded portion 11 and the opening 13 is formed in the center thereof.

By providing the filter 12 in this way, it is possible to suppress the increase of the inflow resistance of the molten steel and the accompanying pressure loss to a low level.

Although the filter 12 is provided with the opening 13 as an inflow port in the central portion as described above, it may be provided over the entire surface without providing the opening 13. That is,
As described above, a part of the lower end portion 10 expands downward. Therefore, the inflow resistance of the molten steel 4 is greatly reduced. In this case, even if the filter 12 is provided over the entire surface of the inlet of the molten steel 4 at the lower end portion 10, unlike the conventional ascending dip pipe 5, the pressure loss is small and the inflow resistance of the molten steel 4 does not increase. .

[0023]

EXAMPLE A lower dip 10 shown in FIG. 1 is attached to the upper end via a flange joint 53 to form an ascending dip pipe, and a RH degassing vacuum refining apparatus to which this is attached is used to make steel grades and ultra low carbon steel. (C / ≦ 0.03%, Si / 0.03%, Mn /
0.10%), the molten steel obtained by oxygen blowing was secondarily subjected to vacuum degassing refining (treatment number of times: 300 tons × 3 hours).

In this case, the enlarged portion 11 provided in a part of the lower end portion 10 of the ascending dip pipe has an inner diameter of 750 m in the other portion of the dip pipe.
m, whereas it expands downward and the inside diameter is 11
Expanded to 00 mm.

For comparison, an ascending dip tube (inner diameter 7
(50 mm) was similarly subjected to secondary refining using the conventional RH degassing vacuum refining apparatus having a constant inner diameter throughout, for the purpose of obtaining the same steel grade.

Regarding this result, when the ring flow rate of the molten steel of the conventional example was set to 100%, when using the one according to the present invention, it was improved to 110%.

Further, as shown in FIG. 2, a filter (alumina ceramic material, large diameter 1800 mm, small diameter 8 mm) was squeezed downward on the tip surface of the enlarged portion 11 and the same test was conducted. The amount of inclusions in the molten steel (obtained as the total oxygen amount) was 18 ppm in the conventional example, but when the filter was provided, it decreased to 10 ppm, and the separation of inclusions was extremely effective. I understood.

Further, different from the one shown in FIG. 2, the same experiment was carried out for the filter provided over the entire surface without the opening. As a result, the amount of inclusions is 9-8 p
Although it decreased to about pm, the flow rate of molten steel was slightly higher than that of the conventional example and was about 103%.

[0029]

As described above in detail, according to the present invention, in an ascending dip tube for blowing molten steel with argon gas interposed, the diameter of the lower end of the rising dipping pipe is such that the tip end portion for dipping in the molten steel is enlarged downward. Is formed, and further,
In the enlarged portion that expands downward, a filter for removing non-metallic inclusions in the molten steel is attached to the tip of the enlarged portion.

Therefore, the inflow resistance of the molten steel from the lower ladle can be greatly reduced, and the ring flow rate of the molten steel can be greatly increased, so that the degassing effect and the removal effect of non-metallic inclusions are greatly improved. it can.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an ascending dip tube of an RH degassing vacuum refining apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of an ascending dip tube of an RH degassing vacuum refining apparatus according to another embodiment of the present invention.

FIG. 3 is an explanatory view showing the principle of a conventional RH degassing vacuum refining apparatus.

FIG. 4 is a vertical cross-sectional view of an ascending dip tube of the RH degassing vacuum refining device shown in FIG.

[Explanation of symbols]

 1 RH degassing and refining equipment 2 Vacuum container 3 Ladle 4 Molten steel 5 Ascending dip tube in conventional example 6 Descending dip tube in conventional example 7 Argon gas 10 Lower end of ascending dip tube 11 Expanded part 12 Filter

Claims (3)

[Claims] 1. An RH degassing and refining apparatus, comprising an ascending dip tube for blowing molten steel with argon gas interposed between the lower end portion and the tip end portion for dipping the inner diameter in the molten steel downward. RH degassing and refining equipment. 2. The lower end portion which expands downward,
The RH degassing and refining apparatus according to claim 1, wherein a filter for removing non-metallic inclusions in the molten steel is attached to the tip thereof. 3. The RH degassing and refining apparatus according to claim 1, wherein an opening is formed in the center of the filter.