JP2012201934A - Ladle refining apparatus and ladle refining method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ladle refining apparatus capable of imparting a horizontal swirling component to a flow of molten steel in a ladle without using an elaborated apparatus, and to provide a ladle refining method using the same.SOLUTION: In the ladle refining apparatus 1, a bottom-blowing plug 3 is arranged at a position away from the center O of a ladle bottom surface 1a. On a side wall 1b close to the position of the bottom-blowing plug 3, a rectifying protrusion 5 is formed along a circumference of the side wall 1b.

Description

  The present invention relates to a ladle refining apparatus and a ladle refining method using the same.

In recent years when quality requirements for steel have become stricter, ladle smelting is generally carried out in which a molten steel is decarburized, deoxidized, desulfurized, inclusions removed, and final component adjustment is performed in a ladle. In ladle refining, technology to stir molten steel in the ladle is important.
The reason is that it is difficult to remove the small inclusion particles of several μm in the molten steel alone, but when it is agglomerated and enlarged, it can be floated and separated using a difference in buoyancy. This is to promote the aggregation of inclusion particles.

Various methods have been tried to stir molten steel in ladle refining, such as using electromagnetic force, sucking in a vacuum tank, or blowing gas from an immersed lance. Recently, a bottom-blown gas agitation by installing a plug that can be bottom-blown in a ladle and blowing gas from the plug is efficient, and it is most frequently used because it is inexpensive in terms of equipment.
Generally, in ladle bottom blowing gas stirring, a refractory porous plug or slit plug is installed at the bottom of the ladle, and an inert gas such as argon or nitrogen is blown into the molten steel to cause the molten steel to flow.
In ladle bottom blown gas stirring, in order to create appropriate stirring conditions, the gas flow rate is specified as shown in Patent Document 1, or the initial bubble diameter of gas is specified as shown in Patent Document 2. Has been tried.

JP-A-1-287218 Japanese Examined Patent Publication No. 56-49969 JP-A-6-235018

  By the way, as mentioned above, the ladle bottom blowing gas stirring is a stirring means using the buoyancy of an inert gas such as argon or nitrogen. Therefore, the flow of the molten steel generated by the rising of the gas becomes an upward flow that goes directly from the plug. This upward flow eventually turns to the horizontal direction when it reaches the bath surface and becomes a downward flow at the point where it hits the ladle side wall. In this way, the flow of molten steel inside the ladle is basically a flow that repeats ascent and descent, and does not include a horizontal swirl component that stirs inside the ladle.

Therefore, in order to more effectively implement the ladle bottom blowing gas stirring, it is only necessary to impart a horizontal swirl component to the molten steel flow. For example, in the technique described in Patent Document 3, it is attempted to give a swirl component in the horizontal direction to the flow of molten steel by changing the gas flow rate from a plurality of plugs in time series. However, in order to change the gas flow rate, there is a problem that a complicated device having a mechanical movable part is required.
Therefore, the present invention has been made paying attention to such problems, and a ladle refining device capable of imparting a horizontal swirl component to the flow of molten steel inside the ladle without using a complicated device And it aims at providing the ladle refining method using this.

In order to solve the above problems, a first invention of the present invention is a ladle refining device in which one bottom blowing plug is installed on a circular bottom surface for ladle refining, wherein the bottom blowing plug is In addition to being installed at a position away from the center of the bottom surface, a rectifying portion formed in a convex shape along the circumferential direction of the side wall surface is provided on the side wall surface near the position of the bottom blowing plug. And
The second invention of the present invention is a ladle refining apparatus in which a plurality of bottom blowing plugs are installed on a circular bottom surface for performing ladle refining, wherein at least one of the bottom blowing plugs is disposed on the bottom surface. And a rectifying portion formed in a convex shape along the circumferential direction of the side wall surface is provided on the side wall surface near the position of the bottom blowing plug. .
The third invention of the present invention is a ladle refining method, wherein refining is performed using the ladle refining apparatus according to the first invention or the second invention of the present invention. .

  According to the ladle refining apparatus and ladle refining method using the same according to the present invention, the bottom blowing plug is installed at a position away from the center of the bottom surface, and on the side wall surface near the position of the bottom blowing plug. Since the straightening portion formed in the ridge along the circumferential direction of the side wall surface is provided, the straightening component in the horizontal direction can be imparted to the flow of the molten steel inside the ladle by the straightening portion that forms the ridge. it can. And since this rectification | straightening part is made into the simple protruding item | line, it can give the turning component of a horizontal direction to the flow of the molten steel inside a ladle, without using a complicated apparatus.

It is explanatory drawing of one Embodiment of the ladle refining apparatus which concerns on this invention, The figure (a) is a front view, (b) is a top view. It is a graph explaining the effect of the ladle refining apparatus which concerns on this invention, and the ladle refining method using the same.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
1 (a) and 1 (b) show an embodiment of a ladle refining apparatus according to the present invention. In the example shown in the figure, Ar gas 4 is blown into the ladle refining device 1 (hereinafter also referred to as “ladle”) 1 with 1000 L / min of Ar gas 4 from the bottom blowing plug 3 in a state where 150 tons of molten steel 2 is held. It shows the state of the ladle refining operation.

  The ladle 1 is a container having a circular bottom surface 1a and a side wall surface 1b surrounding the bottom surface 1a. A single bottom blowing plug 3 is installed on the bottom surface 1a. The bottom blowing plug 3 is installed at a position (having a distance R) away from the center O of the bottom surface 1a. Further, the ladle 1 is provided with a rectifying portion 5 formed in a convex shape along the circumferential direction of the side wall surface 1b on the side wall surface 1b on the side close to the position of the bottom blow plug 3. Here, the height of the ridges of the rectifying unit 5 is h, the length is W, and the distance d of the end portion on the side close to the bottom surface 1a. In addition, the thickness of a protruding item | line should just be the thickness which can fix the rectification | straightening part 5 with respect to the flow of the molten steel 2, and there is no prescription | regulation of a substantial dimension. However, when this rectification | straightening part 5 is comprised with a refractory brick, although it can be considered to set it as thickness of about "130 mm", for example, it is not limited to this.

  The rectifying unit 5 can adopt various shapes as long as the shape forms a ridge along the circumferential direction of the side wall surface 1b. However, as the rectifying unit 5 of the present embodiment, the front view is a rectangular plate shape. The rectifying plate is erected along the circumferential direction of the side wall surface 1b by a refractory brick to form a ridge. Further, in the front view ((a) in the same figure), various angles can be set for the angle θ formed by the rectifying unit 5 with respect to the bottom surface 1a, but the flow while giving a sufficient swirling flow to the flow of the molten steel 2 Therefore, the angle θ is preferably about 15 to 60 degrees. In the present embodiment, the rectifying unit 5 installed on the side wall surface 1b has an angle of 45 degrees as the angle θ with respect to the bottom surface 1a.

Next, the operation and effect of the ladle 1 and the ladle refining method using the ladle will be described.
In the conventional ladle, the flow of the molten steel rising from the bottom blowing plug changes its direction in the horizontal direction when it reaches the bath surface and becomes a downward flow at the point where it hits the ladle side wall. Therefore, the molten steel flows roughly in a direction parallel to a plane passing through the position of the bottom blowing plug and the center of the bottom of the ladle.

  On the other hand, according to the ladle refining device 1, as described above, the bottom blowing plug 3 is installed at a position away from the center O of the bottom surface 1a, and the side wall surface near the position of the bottom blowing plug 3 is installed. Since the rectification part 5 formed in the ridge along the circumferential direction of this side wall surface 1b was provided in 1b, this horizontal rectification part 5 gives the horizontal swirl component to the flow of the molten steel 2 inside the ladle 1 can do. And since the rectification | straightening part 5 which makes this protruding item | line can be made into the simple shape as mentioned above, a horizontal swirling component is provided to the flow of the molten steel 2 inside the ladle 1 without using a complicated apparatus. can do.

  In order to confirm the effect of the present invention, the uniform mixing time of molten steel was examined by numerical thermal fluid analysis (simulation). Of the 150 tons of molten steel 2, 0.45% molten steel 2 present near the center O of the bottom surface 1a is marked to distinguish it from other molten steels, and how the marked molten steel 2 spreads. I investigated. The condition of this simulation is that the hot water surface height is about 2000 mm, the inner diameter of the ladle 1 at this hot water surface height is about 3800 mm, the inner diameter of the ladle 1 at the bottom surface 1 a is 3400 mm, and the convexity of the rectifying unit 5 is The height h of the ridge was 150 mm, the length W of the ridge was 2800 mm, and the distance d between the ends close to the bottom surface 1a was 300 mm. In the simulation, first, 150 tons of molten steel 2 was divided into 200,000 control volumes, and the concentration of the marked molten steel 2 was examined in each control volume. Among these, the minimum value and the maximum value of the concentration of the marked molten steel 2 were determined, and the mixing ratio was obtained by dividing the minimum value by the maximum value.

FIG. 2 shows the time transition of the mixing ratio of the molten steel 2 marked as described above. The horizontal axis represents the time from the start of stirring, and the vertical axis represents the mixing ratio. In the same figure, examples of three kinds of tests in which θ is set to 15 degrees, 45 degrees, and 60 degrees are shown together with respect to the angle θ formed by the rectifying unit 5 with respect to the bottom surface 1a. As shown in the figure, it can be seen that when the rectifying unit 5 is installed, the molten steel inside the ladle 1 can be uniformly stirred in a shorter time than when the rectifying unit 5 is not installed.
The ladle refining apparatus and the ladle refining method using the ladle refining apparatus according to the present invention are not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. It is.

  For example, in the said embodiment, although the example which installed the single bottom blowing plug 3 in the bottom face 1a demonstrated, it is not restricted to this, For example, with respect to the ladle 1 which installed the several bottom blowing plug 3 in the bottom face 1a However, the present invention can be adopted. In this case, at least one of the plurality of bottom blowing plugs 3 is installed at a position away from the center O of the bottom surface 1a, and the side wall surface 1b near the position of the bottom blowing plug 3 What is necessary is just to provide the rectification | straightening part 5 formed in the protruding item | line along the circumferential direction of the side wall surface 1b.

1 Ladle Refining Equipment 2 Molten Steel 3 Bottom Blow Plug 4 Ar Gas 5 Rectifier

Claims (3)

A ladle refining device in which a single bottom-blown plug is installed on the circular bottom surface for ladle refining,
The bottom blowing plug is installed at a position away from the center of the bottom surface, and a rectifying part formed on the side wall surface near the position of the bottom blowing plug is formed as a ridge along the circumferential direction of the side wall surface. A ladle refining device characterized by being provided. A ladle refining device in which a plurality of bottom blowing plugs are installed on a circular bottom surface for ladle refining,
At least one of the bottom blowing plugs is installed at a position away from the center of the bottom surface, and is formed on the side wall surface near the position of the bottom blowing plug in a protruding line along the circumferential direction of the side wall surface. A ladle refining device characterized by providing a rectifying unit.   The ladle refining method characterized by performing refining using the ladle refining apparatus of Claim 1 or 2.

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