JPH05311229A - Ladle degassing treatment apparatus - Google Patents

Abstract

PURPOSE:To achieve high degree of degassing in a short treating time by arranging plural lances as an arc state having a specific distance from the center of a ladle and specifying central angle of the arc. CONSTITUTION:Plural blowing lance 3 arranged in a vacuum hood covered by closely contacting with the upper part of the ladle 1 are dipped into molten steel in the ladle, and inert gas of Ar, etc., is blown into the molten steel from discharging holes 3b at the lower part of the lance. In this apparatus, plural lances 3 are arranged at the side wall 1a side in the ladle from 1/2 of the radius (r) of the ladle 1 along the side wall 1a by using the discharging hole 3b as the reference. Therefor, the distance r1 in the radius direction from the center O of the ladle 1 to the lance 3 satisfies r1>=r/2. Further, the lances 3 are arranged as the arc-state and the central angle theta in the horizontal direction formed with the lances 3c, 3c at both end parts is made to 60-270 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ladle degassing apparatus capable of efficiently removing carbon, nitrogen, hydrogen, etc. in molten steel.

[0002]

2. Description of the Related Art R is a method for refining molten steel in a ladle.
There are H method, DH method and ladle degassing method. FIG. 10 is a side cross-sectional explanatory view showing an example of a degassing treatment apparatus used in the ladle degassing method. A vacuum hood 2 is tightly covered on the upper portion of the ladle 1 containing the molten steel F, and the exhaust pipe 2a provided in the hood 2 degasses it to keep the inside of the ladle 1 in a vacuum state. A porous plug 4 is provided at the bottom of No. 1 and an argon gas is blown into the molten steel F through a supply pipe 4a connected to the porous plug 4. Reference numeral 2b represents an alloy supply pipe.

It should be noted that instead of providing the vacuum hood 4, the whole ladle 1 is housed in a vacuum tank, or the porous plug 4 used for gas injection is replaced by the broken line in FIG. Some have a blowing lance 3.

By the way, in recent years, from the viewpoint of improving the quality characteristics of steel materials, for example, the carbon concentration in molten steel is 20 ppm or less (in some cases,
10ppm or less) may be required. As described above, in order to reduce the carbon concentration in the molten steel, it has been necessary to set a long treatment time in the conventional degassing treatment apparatus.

That is, as a method for increasing the degassing rate, there are (a) a method for increasing the reaction rate of C + O → CO in the reaction zone, and (b) a method for increasing the reaction zone and the molten steel reflux rate.

In order to carry out the above method (b), it is necessary to raise the degree of vacuum of the ladle and the amount of blown argon. However, in the above-mentioned processing apparatus, there is a limit in increasing the degree of vacuum, and since the gas injection part by the lance or the porous plug is limited to one place, it is difficult to inject a large amount of gas into the molten steel. In addition, there was a problem that the gas bubbles to be blown could not be widely dispersed in the molten steel F. Therefore, the degassing process becomes non-uniform, and the time required to reach the target level of degassing in the entire molten steel is inevitably long, which causes a decrease in the molten steel temperature and a decrease in production cost. Was there.

[0007]

Therefore, an object of the present invention is to enable a large amount of gas to be blown into the molten steel in the ladle and to disperse gas bubbles widely in the molten steel so that degassing treatment can be performed. It is to provide a ladle degassing treatment device that can be efficiently performed.

[0008]

According to the present invention which has achieved the above object, a plurality of lances or porous plugs are arranged such that the horizontal distance from the center of the ladle is 1/2 or more of the radius of the ladle. Are arranged in an arc along the side wall of the ladle, and the central angle of the arc is 60 ~
The main point is to configure it to be 270 degrees.

[0009]

In the apparatus of the present invention, since a plurality of blowing lances or porous plugs are used and they are arranged at appropriate positions and spreads, a large amount of inert gas can be uniformly and efficiently blown into the molten steel. The rate of degassing such as decarbonization and dehydrogenation can be increased.

FIG. 6 shows the expansion of the blowing position when a plurality of blowing lances (or porous plugs) are arranged in an arc shape.
That is, it is a graph obtained by measuring the relationship between the central angle θ viewed horizontally from both ends of the lance and the porous plug and the ring flow rate by a model experiment using water, and when the central angle θ is 60 degrees or more.
Within the range of 270 degrees or less, the ring flow rate is 400 liters /
It can be a high value exceeding minutes.

FIG. 7 is a graph in which the relationship between the arrangement position of a plurality of blow lances (or porous plugs) in the horizontal direction and the ring flow rate is measured by a model experiment using water. It was 120 degrees. Ladle radius r
The radial distance from the center to the blow-in center of the blow-in lance (or the inner end of the porous plug) is r ₁ (r ₀ ), and this ratio r ₁ / r is shown on the horizontal axis. According to this, r ₁ /
If r is 0.5 or more (that is, closer to the side wall than 1/2 of the radius r of the ladle), a high ring flow rate of 400 liter / min is shown.

Therefore, if the blowing lance (or porous plug) is arranged so as to satisfy the above two conditions, the molten steel in the ladle is agitated so as to recirculate, and the blowing gas bubbles are also directed in the circumferential direction of the ladle. It will be dispersed and will rise later, and the degassing reaction rate such as decarbonization and denitrification can be increased. The immersion depth of the blowing lance in the molten steel (the length from the molten steel surface to the gas discharge port) is preferably 1000 mm or more, which ensures the above reflux.

[0013]

1 is a side sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II--II of FIG. The ladle 1 and the vacuum hood 2 are constructed in the same manner as the conventional example shown in FIG. 10, and a plurality of blowing lances 3, 3 ... Are formed in the vacuum hood 2 and are connected to the argon gas supply pipe 3a. The lance 3
Since a discharge port 3b is formed in the lower part of and the argon gas is blown into the molten steel F from here, the following dimensions are based on this discharge port 3b.

That is, the blowing lances 3, 3 ... Are located on the side wall 1a side of 1/2 of the radius r in the ladle 1, and are located on the side wall 1a.
It is provided along a. Therefore, the radial distance r ₁ from the center O of the ladle 1 to the blowing lance 3 satisfies r ₁ ≧ r / 2.

The plurality of blowing lances 3, 3 ... Are provided in an arc shape, and the central angle θ in the horizontal direction formed by the lances 3c, 3c at both ends thereof is arranged to be 60 degrees or more and 270 degrees or less. When dipping the blowing lance 3 into the molten steel F, it is desirable to dip it while flowing a small amount of argon gas so that the molten steel does not enter the lance.

FIG. 3 is a side sectional view showing another embodiment of the present invention, and FIG. 4 is a sectional view taken along the line IV-IV in FIG. Ladle 1
A plurality of porous plugs 4, 4, ... Are provided in an arc shape along the side wall 1a at the bottom portion 1b thereof, and the central angle θ in the horizontal direction between the ends of these porous plugs 4, 4 ,.
In addition to being provided within the range of degrees, the inner end of the porous plug 4 on the center side is disposed on the side wall side with respect to 1/2 of the radius r.

FIG. 5 is a cross-sectional explanatory view showing another embodiment of the present invention, in which a ladle 1 is provided with electromagnetic induction coils 5 and 5 for stirring. Further, FIG. 9 shows an example in which oxygen gas is sprayed from the spray nozzle 16 during degassing.

(Experimental Example 1) In an apparatus as shown in FIGS. 1 and 2, a ladle having an inner diameter of 3.8 m and a height of 3 m was used, and a diameter of 250 mm.
Soak 10 lances with a length of 2 m so that the depth to the discharge hole is 1.5 m, depressurize the inside of the ladle to a maximum of 0.5 Torr, and 3000-7000 liters / min during degassing. Argon gas was blown in at a ratio of. The central angle θ was 120 degrees, and the distance r ₁ from the center of the ladle was 1400 mm. FIG. 8 is a graph showing the decarburization rate in Example 1 above, and the treatment time is drastically shortened as compared with the conventional RH method, and for example, the treatment time for reducing the carbon concentration to 20 ppm can be shortened by 5 minutes. It became like.

(Experimental Example 2) In the apparatus as shown in FIGS. 3 and 4, the size of the ladle and the vacuum conditions were the same as in Experimental Example 1, and 12 porous plugs having a diameter of 100 mm were used and the central angle θ = 120.
And the distance r ₂ was 1400 mm. Thus, during degassing, argon gas was blown at a rate of 2500 to 6000 liters / minute to carry out decarburization, and the processing time was measured. As a result, it took 12 minutes to process the carbon concentration to 20 ppm and 18 minutes to process the carbon concentration to 10 ppm.

[0020]

Since the present invention is constructed as described above, a large amount of inert gas can be blown into the molten steel ladle, and
It is possible to promote the reflux of molten steel and widely disperse gas bubbles, so that the molten steel can be treated uniformly and uniformly, so that degassing such as decarbonization, dehydrogenation and denitrification can be performed efficiently in a short time. Became.

[Brief description of drawings]

FIG. 1 is a side sectional explanatory view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a side sectional explanatory view showing another embodiment of the present invention.

4 is a sectional view taken along the line IV-IV of FIG.

FIG. 5 is a sectional explanatory view showing another embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a central angle θ of arrangement of a lance and an annular flow rate.

FIG. 7 is a graph showing a relationship between an arrangement position of a lance and a ring flow rate.

FIG. 8 is a graph showing a degassing treatment time.

FIG. 9 is a side sectional explanatory view showing another example of the present invention.

FIG. 10 is a side sectional explanatory view showing an example of a conventional degassing device.

[Explanation of symbols]

 1 Ladle 2 Vacuum hood 3 Lance 4 Porous plug r Ladle radius

Claims (2)

[Claims] 1. A ladle degassing apparatus configured to immerse an inert gas blowing lance in a ladle molten steel, wherein a plurality of lances are arranged such that the horizontal distance from the center of the ladle is that of the ladle. A ladle, which is arranged in an arc shape along the side wall of the ladle at a position that is 1/2 or more of the radius, and is configured such that the central angle of the arc is 60 to 270 degrees. Degassing equipment. 2. A ladle degassing apparatus in which a porous plug for injecting an inert gas is disposed at the bottom of a ladle, wherein a plurality of porous plugs have a horizontal distance from the center of the ladle that is the radius of the ladle. Arranged in an arc at a position that is 1/2 or more of
A ladle degassing apparatus characterized in that the central angle of the arc is 60 to 270 degrees.