JP2000256728A - Ladle for molten metal and method for refining molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ladle which can execute mechanical stirring of molten metal by forming the horizontal cross section at least near the statical bath surface height of stored molten metal to non-circular shape. SOLUTION: Relating to the ladle, preferably the non-circular shape is made to an elliptic shape having 0.75-0.95 in the range of the ratio of minor axis/major axis and the vicinity of the statical bath surface height is at least 200 mm in the vertical range of the statical bath surface, and the mechanical stirring means is provided in the inner part where the molten metal is contained. When the molten iron 5 is stirred with an impeller, the vertical stream (a) is generated and the larger the number of the rotation is, the stronger the stream (a) is, and the bath surface 10 is raised near the recessed side wall at the center part and becomes the max. near the side wall on the minor axis. However, since the space, in which the stream is run away by the difference between the minor axis side at the wall side on the major axis exists, the stream (a) is separated and the stream (b) is generated and the raising of the bath surface is lost in the stream (b) direction and reduced. In this way, the over-flow of molten metal from the ladle during refining is eliminated and the refining can stably and smoothly be executed to improve the refining effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ladle for molten metal and a method for refining molten metal, and more particularly to a technique for stably mechanically stirring molten metal such as hot metal and molten steel without any trouble.

[0002]

2. Description of the Related Art It has been known that hot metal and molten steel are charged into a ladle (hereinafter, referred to as a pan), and a refining agent is fed into the ladle while stirring with a mechanical stirrer to perform a process such as desulfurization. I have. For example, Japanese Patent Publication No. 42-12343 discloses a technique using an impeller as a stirring means. According to this technique, hot metal is put in a pot, and an impeller having a representative diameter corresponding to a length of 1/10 to 1/3 of an inner diameter of the pot is formed in a range of 150 to 300.
r. p. m to rotate the hot metal for desulfurization.

[0003] Such a mechanical stirring technique has been known for a long time, but thereafter, studies on the stirring behavior of the molten metal by gas injection have been actively conducted, and the stirring processing of the molten metal is exclusively performed by gas injection. Stirring became mainstream. The reason for this is that in mechanical stirring, the life of the refractory lining the impeller immersed in the molten metal is short, and the processing cost becomes too high. In addition, for gas injection stirring, a powdered scouring agent or alloying agent is directly injected into the molten metal using the injected stirring gas as a carrier gas, and the addition yield and the reaction efficiency with the impurity element to be removed are also increased. There was a high advantage.

[0004] However, in recent years when the requirements for the quality of molten metal have become much more severe, gas blowing agitation has a limit to the agitation power given to the molten metal, and there are cases where such requirements cannot be sufficiently satisfied. Therefore, a mechanical stirring process using an impeller is being reconsidered as a refining process in which impurities are to be reduced to a minimum. However,
When trying to apply the conventional mechanical stirring technology to the existing refining process, the following problems were encountered.

[0005]

[Problems to be solved by the invention] Japanese Patent Publication No. 42-0123
In hot metal desulfurization described in Japanese Patent No. 43, as the rotation speed of the impeller increases, the hot metal surface in the pan becomes as shown in FIG.
It has a shape in which a triangular pyramid having one point on the stirring shaft 11 as a vertex is inverted. Then, the stationary bath surface 7 in the pot of the hot metal 5 (hereinafter, referred to as
Comparing the bath surface 10 having this shape with the bath surface 10 of this shape, the higher the number of rotations, the higher the highest point of the bath surface 10 becomes higher than the above-mentioned bath surface 7. Tokiko Sho 42-01
According to JP 2343, 300r. p. m. Then, the bath surface 10 of the hot metal 5 is raised by 400 mm from the stationary bath surface 7.

On the other hand, the pot 6 is lined with a refractory material 8 and usually has a circular cross section (inner diameter of 3.0 to 4.5 m) in an internal space for accommodating the molten metal 5 and a depth of 3.5. ~ 4.0
m. In recent years, from the viewpoint of improving the refining efficiency, there is a tendency that the refining processing amount per one time of the pot 6 is increased. Therefore, the distance between the bath surface and the upper end of the side wall of the pot 6 is very small, and is only about 300 mm. When the conventional mechanical stirring technique is performed in such a state, the hot metal 5 often overflows due to the rise of the hot metal bath surface. As a countermeasure for this, it is necessary to reduce the amount of received iron in the pan 6 or to raise the height of the side wall of the pan 6 to make it extremely high with respect to the bath surface.

[0007] However, it is clear that a decrease in the amount of received iron causes a significant decrease in the transport efficiency. In addition, raising the side wall causes inconvenience for the crane that transports the pot 6.
In other words, it is not possible to cope with an increase in the amount of hoisting the chain, and it is necessary to remodel the building. Furthermore, when the pan 6 is installed in the next step, a large amount of cost is required for equipment remodeling including a change in the installation height. In addition, the work height of the refractory 8 in the pot 6 itself is increased, and the amount of refractory used must be increased.

In view of such circumstances, the present invention provides a ladle for molten metal and a ladle for molten metal which can stably perform mechanical stirring of molten metal by merely changing the construction state of a refractory lining of an existing ladle. It is an object of the present invention to provide a method for refining molten metal using a pot.

[0009]

In order to achieve the above object, the inventor repeated many tests on the relationship between the internal structure of the ladle and the rise of the molten metal surface, and realized the results in the present invention. .

That is, according to the present invention, in a ladle for molten metal lined with a refractory material and containing a molten metal, at least a flat section near the height of a stationary bath surface of the contained molten metal is constructed in a non-circular shape. It is a ladle for molten metal characterized by comprising.

In the present invention, the non-circular shape may be an elliptical shape, and the ratio of the minor axis to the major axis may be in a range of 0.75 to 0.95, or the vicinity of the height of the stationary bath surface may be set at the stationary state. A molten metal ladle having a range of at least 200 mm above and below the bath surface.

Further, the present invention is a ladle for molten metal, wherein a mechanical stirring means is provided inside the molten metal.

In addition, the present invention provides a molten metal ladle containing the molten metal, adding a refining agent and / or an alloying agent to the molten metal, and removing the molten metal by the mechanical stirring means. It is also a method for refining molten metal, which comprises stirring and refining.

In the present invention, the internal structure of the ladle is such that the molten metal is prevented from rising on the molten metal surface, so that the molten metal does not overflow from the ladle during refining. In addition, smelting can be performed stably and smoothly, and the results of smelting can be improved.

[0015]

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

First, although the pot according to the present invention may have a new outer shape, the same outer skin or outer shape as the existing pan currently used for containing the molten metal, or at least the outer shape of the hanging tool for handling the pan. It is preferred that The reason is that if the outer shape of the steel is the same as that of a normal ladle, various facilities for processing such as refining using this pan, transfer facilities such as cranes and bogies for handling the pan, and refractory stands for repair This is because there is no need to make any changes to the above.

In the present invention, a number of tests are conducted with a focus on the internal structure of the pot, and the stationary bath surface 7
By making the plane cross section in the vicinity non-circular, the rising of the bath surface 10 near the inner wall surface of the pot, which occurs when the molten metal is stirred, is reduced.

In the test, molten metal was used as hot metal.
The test was performed using the apparatus shown in FIG. The apparatus comprises a pot 6 for accommodating hot metal 5 lined with a refractory 8, a moving device 1 for shifting a stirring means to a position, and an impeller 3 of a mechanical stirring means.
And the motor 2 for rotating the impeller 3 and the elevating means 9 for lowering the impeller 3 until the blades are immersed in the bath. In this apparatus, the refining agent 4 was actually added to the hot metal 5 and desulfurization was also performed.

This test was carried out with a pot 6 having various internal structures, but it was found that the bath surface was highest when the flat cross section near the stationary bath surface 7 was circular. The first requirement of the present invention is that it is circular. further,
The test was continued, and it was also found that it was preferable that the flat cross section as shown in FIG. 1 had an elliptical shape. The elliptical shape shown in FIG. 1 has a ratio of the major axis to the minor axis of 100.
It is 95 pairs. In this case, when the hot metal 5 is stirred by the impeller not shown in FIG. 1, a vertical flow (symbol a) occurs in the hot metal 5 in the direction of being sucked into the impeller. This flow (a) is stronger as the number of revolutions of the impeller is higher. As a result, the bath surface is recessed in a shape like an inverted cone, and the bath surface rises near the side wall of the pan. The rise of the bath surface is formed in a symmetrical shape because the pan 6 is a symmetrical container. Further, the bath surface induced by the flow (a) develops so as to be maximum near the side wall on the short side. However, since there is a space on the side of the long side on which the flow can escape by the difference from the side of the short side, the flow (a) is split into a flow (symbol b). Since the flow (b) is a flow in the radial direction of the bath surface, the rise of the bath surface collapses in the flow (b) direction, and the rise of the bath surface is a conventional circular cross section (see FIG. 4). Is suppressed as compared with. The actual flow is very complicated because it involves the flow in the plane section direction due to agitation, and many tests were required. This figure 1
In the example, the rise of the bath surface is 以下 or less as compared with the conventional case (in the case of a circle), and 300 r. p. m. Was also at most 150 mm. In other words, the amount of molten metal charged into the pan 6 could be reduced to a sufficient amount without raising the side wall of the pan 6 and the amount of molten metal could be sufficiently reduced.

If the shape of the side wall of the pot is too complicated or the surface of the refractory 8 is extremely complicated, the molten metal 5 or the slag existing on the molten metal 5 causes a large amount of wear of the refractory lining 8. Preferably, the shape is as smooth as possible. In addition, since it is preferable that the refractory 8 has a simple shape in construction, an elliptical shape is considered to be the best in practical use. In this case, the ratio of the minor axis / major axis is preferably in the range of 0.75 to 0.95. Minor axis /
As the ratio of the major axis becomes smaller, the rise of the bath surface near the side wall of the pot can be suppressed. However, when the ratio is less than 0.75, the effect is almost saturated, and the flow of the molten metal or slag causes the flow of the molten metal or the slag near the bath surface. This is because the erosion of the side wall refractory tends to increase. On the other hand, when the ratio of minor axis / major axis exceeds 0.95, the cross-sectional shape of the inside of the pan becomes close to a circle, the rise of the molten metal near the side wall of the pan increases, and the molten metal flows out of the pan. This is because there is a high possibility that overflow will occur.

Further, in the present invention, the flat section may be elliptical throughout the depth direction of the pot 6, but may be a partial depth as long as the rise of the bath surface can be suppressed.
In that case, the cost of the refractory 8 and the core can be reduced, and the weight of the pot is small, so that the load of transportation by a crane or the like is small.
In the present invention, when a part of the pot in the depth direction is formed into an elliptical shape, at least a range of about 200 mm is required in order to exhibit the effect of reducing the rise of the molten metal near the side wall of the pot. It is preferable to have such a shape.

Further, the non-circular internal structure of the pot 6 can be easily formed by lining the refractory 8.
When a brick is used for the refractory lining, it can be realized in any shape depending on the shape and the way of stacking the brick. Also,
In the case of casting with an irregular-shaped refractory, the core may be formed with a shape corresponding to the above-mentioned internal shape.

Next, a means for stirring the molten metal 5 was examined.
As a result, it was found that it is best to immerse the refractory rotator in the molten metal 5 and mechanically rotate the rotator by the power of a motor or the like. As the stirring means, for example,
As disclosed in Japanese Patent No. 238321, electromagnetic stirring that applies a moving magnetic field outside the pan 6 is also known, but in the case of such electromagnetic stirring, the rotational force of the molten metal 5 increases the inner wall of the ladle. , The refractory lining 8 is greatly worn. In particular, when the flat cross section inside the ladle near the bath surface is made non-circular as in the present invention, the refractory that protrudes (or protrudes) toward the molten metal side is selectively formed by the flow of the molten metal 5. It will be worn. However, the inventor
From the many test results described above, when the rotating body is immersed in the molten metal and mechanically stirred, the flow rate of the molten metal tends to decrease as it approaches the inner wall of the pan, It has been newly discovered that such a wear problem is unlikely to occur. In the present invention, the stirring of the molten metal 5 is performed using a mechanical rotating body.

Further, the inventor puts the molten metal 5 in the pan 6 according to the present invention described above, adds a refining agent and / or an alloying agent to the molten metal 5, and adds a rotating body in the molten metal. The treatment of molten metal by immersing and stirring was also attempted. Specific examples include desulfurization treatment, dephosphorization treatment, deoxidation treatment, inoculation treatment, and addition treatment of Ca and REM for controlling the inclusion morphology of the molten iron alloy. In particular, in the case of desulfurization treatment, ni is Mg,
Metals such as Ca or REM and alloys thereof, or a combination treatment of these metals or alloys with a flux such as lime was performed. As a result, very good test results were obtained, and the refining method using such a ladle was also considered as the present invention.
In this case, in addition to the mechanical stirring, stirring may be performed by blowing gas through the rotating body itself or the bottom of the pot.

[0025]

EXAMPLE A hot metal desulfurization refining treatment was carried out using a molten metal ladle according to the present invention and a conventional ladle. At that time, the desulfurizing agent was charged at one time before the treatment. The pot 6 had a nominal inner volume of 60 tons and was lined with a refractory 8 to form a cylindrical space having a circular section having a diameter of 2400 mm and a depth of 4200 mm inside the refractory 8. And this ladle was made into the conventional type. On the other hand, the molten metal ladle 6 according to the present invention is applied to a region extending 300 mm up and down with respect to the hot metal stationary bath surface 7 of the conventional type ladle (for some, over the entire height of the pan). It was constructed by applying a side wall refractory so that a flat cross section became an ellipse. In this case, the (minor axis / major axis) ratio of the ellipse was determined as shown in Table 1. For stirring the hot metal 5, a mechanical stirring means, specifically, the impeller 3 was employed. The impeller 3 has a wing width of 100 mm and a representative diameter of 500 m.
At m, the rotation axis was arranged so as to coincide with the center axis of the pan 6 as shown in FIG.

The hot metal desulfurizing agent 4 was soda ash, and the whole amount was added immediately before starting the hot metal stirring. In addition, in this example, refining was also performed using lime as desulfurizing agent 4. The desulfurization time was 10 minutes in each case. The weight of the hot metal charged into the pan 6 was adjusted to 60 ± 1 ton in each case. The hot metal 5 overflowing from the pan 6 during the operation was recovered by laying an iron plate below the pan 6, and the amount of the hot metal 5 attached to the pan 6 was evaluated in addition to the recovered amount. The adhesion amount was calculated by the difference between the weight of the empty pot before receiving the hot metal 5 and the weight of the empty pot after dispensing the hot metal. The ratio of the overflowing hot metal 5 is indicated by dividing the amount of the overflowing hot metal by the weight of the hot metal before treatment (assumed to be 60 tons). Further, the desulfurization rate of the hot metal 5 was indicated by dividing the sulfur concentration in the hot metal after the treatment by the sulfur concentration in the hot metal before the treatment and subtracting 1 from the value.

The operating results of such hot metal desulfurization are shown in Table 1 collectively.

[0028]

[Table 1]

According to Table 1, there is almost no difference in desulfurization rate between the case using the ladle according to the present invention and the case using the conventional ladle. However, when using a conventional ladle,
The ladle of the present invention can be said to have a better desulfurization rate in view of the fact that the amount of hot metal overflowing is so large that the net amount of desulfurizing agent used in the pot is increased by that much. This is because the desulfurizing agent 4 was involved in the hot metal 5 when the rising of the bath surface collapsed due to the elliptical shape, and the desulfurization reaction was promoted. The required power is
Almost independent of the shape of the pot 6, at the same rotation speed,
In each case, it was the same. FIG. 3 shows the results of the rise of the bath surface generated during the refining in relation to the rotation speed of the impeller. From FIG. 3, it is clear that the use of the pot 6 according to the present invention can significantly reduce the rise of the bath surface as compared with the related art.

On the other hand, what greatly differs in the operation results is the overflow rate of hot metal at the time of stirring, and in the conventional ladle, the rate exceeds 10% by weight of the charged amount. Not suitable for operation. When the rotation speed of the impeller 3 is 250 r. p.
m. In case (1), as much as 15 tons, which is 25% by weight of the hot metal charged, overflowed, and a trouble such as the pot 6 being buried in the hot metal 5 occurred simultaneously. On the other hand, in the pot 6 according to the present invention, the ratio of the minor axis / major axis was changed from 0.95 to 0.75, but the overflow of the hot metal 5 was extremely small in each case.

In the above embodiment, molten metal was used as the molten metal 5. However, the present invention is not particularly limited to this, and the molten metal ladle 6 according to the present invention can be made of various molten steels, molten alloys, non-ferrous metals. It can also be used for processing metals and the like.

[0032]

As described above, according to the present invention, a ladle for accommodating a molten metal and removing the impurity element contained in the molten metal therein has been modified into an appropriate shape. As a result, even if mechanical stirring is performed, the rise of the hot metal bath surface can be significantly suppressed, and it is possible to provide a molten metal ladle that does not overflow hot metal and does not cause a significant decrease in transport efficiency. Was. In addition, it is possible to carry out efficient impurity treatment without spending a great deal of money on remodeling the equipment.

[Brief description of the drawings]

FIG. 1 is a view showing an example of an internal structure of a ladle according to the present invention, wherein (a) is a plane and (b) is a longitudinal section.

FIG. 2 is a longitudinal sectional view showing a state in which a mechanical stirring means is arranged on a ladle.

FIG. 3 is a diagram showing a relationship between a rotation speed of a molten metal and a rising height of a bath surface.

FIG. 4 is a view showing the internal structure of a conventional ladle.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 moving device of stirring means 2 motor for rotating impeller 3 impeller 4 refining agent (desulfurizing agent) 5 molten metal (hot metal) 6 ladle (pan) 7 stationary bath surface 8 refractory 9 lifting means 10 bath surface 11 stirring shaft

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C21C 7/04 C21C 7/04 QBF C22B 9/00 C22B 9/00 (72) Inventor Shigeru Ogura Chiba 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Japan F-term in the Chiba Works of Kawasaki Steel Corporation (reference) 4K001 AA10 BA23 GA18 GB05 4K013 CC09 CF13 EA03 EA13 EA18

Claims (5)

[Claims] 1. A molten metal ladle lined with a refractory material and containing a molten metal, wherein at least a flat cross section near the height of a stationary bath surface of the contained molten metal is formed into a non-circular shape. Ladle for molten metal. 2. The method according to claim 1, wherein the non-circular shape is an elliptical shape,
The ladle for molten metal according to claim 1, wherein the ratio of the major axis is in the range of 0.75 to 0.95. 3. The ladle for molten metal according to claim 1, wherein the vicinity of the height of the stationary bath surface is at least 200 mm above and below the stationary bath surface. 4. The ladle for molten metal according to claim 1, wherein a mechanical stirring means is provided inside the molten metal. 5. A molten metal ladle according to claim 4, containing a molten metal, adding a refining agent and / or an alloying agent to said molten metal, and stirring said molten metal by said mechanical stirring means. And a method for refining molten metal.