JP2001247910A - Method for stirring molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stirring molten iron held in a molten iron ladle with an impeller, with which a stable and high desulfurizing efficiency can always be obtained by using the impeller. SOLUTION: In the method for stirring the molten iron in a vessel with the impeller, this stirring method has the peculiarity, in which the ratio of the upper end depth of the impeller to the recessed depth of the molten iron surface is regulated to 0.6-0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stirring hot metal in a hot metal pot using an impeller.

[0002]

2. Description of the Related Art Conventionally, as one of the methods for desulfurizing hot metal in a hot metal pot, there is a mechanical stirring method. In this method, a stirrer is immersed in hot metal and rotated to stir the hot metal and a desulfurizing agent well to promote a desulfurization reaction. A method using an impeller (stirrer blade) for the stirrer is known. I have. In the method using the impeller, the impeller attached to the rotating shaft is immersed in the hot metal in the hot metal pot, and is rotated at a high speed by a motor to form a swirling depression and process the hot metal.

[0003]

However, depending on the conditions, a high desulfurization rate may be obtained, but a low desulfurization rate may not always be obtained in a stable manner. There is a problem that a high desulfurization rate cannot always be obtained stably.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have intensively developed and found that the desulfurization rate greatly affects the impeller immersion ratio. The present invention, which is a stirring method using an impeller, which always obtains a stable and high desulfurization efficiency by setting the ratio within a certain range has been achieved. The gist of the invention is that in a method of stirring hot metal in a vessel by an impeller, a ratio of a depth of a top of the impeller to a depth of a pit of the hot metal is set to 0.6 to 0.8. Stirring method.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view showing a method for desulfurizing hot metal by an impeller according to the present invention. As shown in this figure, the hot metal 2 in the hot metal ladle 1 is immersed in the hot metal 2 with the impeller 3 attached to the tip of the rotating shaft.
By rotating the impeller 3, the desulfurization treatment is performed by bringing the hot metal 2 into suspension contact with a desulfurizing agent having a lower specific gravity than the hot metal charged into the hot metal in the hot metal pot 1 to perform desulfurization processing. The hot water surface rises, and the central hot water surface has a dent. That is, the hot metal 6 in the hot metal ladle forms the state of the rotating hot metal surface 4 due to the rotation of the impeller 3.

[0006] The desulfurizing agent charged into the hot metal 2 in the hot metal pot in such a state collects in the concave portion 7 of the molten metal surface, and is brought into contact with the impeller 3 to be given a driving force to be discharged and dispersed into the hot metal 3. Then, a desulfurization reaction occurs in the hot metal, and the slag surface 5 is formed by floating. It is considered that the amount of the desulfurizing agent involved has a relationship with the volume of the desulfurizing agent in contact with the impeller 3 (the hatched portion in the figure, the so-called entrained volume) because the behavior of floating is repeated. Since the winding volume is determined by the depth H of the molten metal surface and the depth h of the upper end of the impeller,
The impeller immersion depth is arranged in relation to the molten metal surface depression depth H. Therefore, the impeller immersion ratio R _dip is given by the following equation. Impeller immersion ratio R _dip = impeller upper end depth h
/ Depth of molten metal surface H

FIG. 2 shows an impeller immersion ratio R according to the present invention.
It is a figure which shows the relationship between _dip and desulfurization distribution. As shown in this figure, the horizontal axis represents the impeller immersion ratio R _dip , and the vertical axis represents the logarithm of the desulfurization distribution Ls logLs (= log (% S) /
[% S]), the desulfurization distribution Ls decreases with decreasing R _dip.
It can be seen that is improved. Here, [% S] is S% of hot metal, and (% S) indicates S% after desulfurization. Therefore,
In order to obtain high desulfurization distribution, rotate the impeller at high speed,
R _dip may be reduced, but the upper limit of the impeller rotation speed is regulated by the relationship between the equipment capacity, the height of the rise, and the freeboard of the hot metal pot.

[0008] Therefore, it is necessary to accurately grasp the freeboard (falling down of the hot metal pot) of the hot metal pot and to process it at the maximum number of revolutions without overflow. Also, as R _dip is reduced, spitting occurs. This is considered to be due to stirring in a state where the upper end of the impeller is exposed on the surface of the _{molten metal} . When R _dip is 0.6 or more, this tendency is not observed, so the lower limit was set to 0.6. Further, when the value of R _dip exceeds 0.8, the desulfurization distribution decreases, so the range is set to 0.6 to 0.8. As described above, by performing R _dip within the range of 0.6 to 0.8, it was possible to achieve extremely stable and excellent improvement in desulfurization efficiency.

[0009]

As described above, the impeller immersion ratio using the impeller immersion ratio using the impeller upper end position to generate an appropriate impeller immersion depth by rotation to efficiently disperse the desulfurizing agent according to the present invention in the molten iron. By setting R _dip within the optimum range, an excellent effect of achieving extremely excellent improvement in desulfurization efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method for desulfurizing hot metal by an impeller according to the present invention.

FIG. 2 is a graph showing the relationship between impeller immersion ratio R _dip and desulfurization distribution according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot metal pot 2 Hot metal 3 Impeller 4 Rotating surface 5 Slag surface 6 Static surface 7 Depressed part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takenori Taniguchi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Works (72) Inventor Tsuneo Koseki 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Inside the Kimitsu Works (72) Inventor Kunihiko Watanabe 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside Nippon Steel Corporation (72) Inventor Reiji Iwatani 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation F term in the Kimitsu Works (reference) 4K014 AA02 AC08 AD00 4K056 CA02 EA12

Claims (1)

[Claims] 1. A method for stirring hot metal in a vessel using an impeller, wherein a ratio of a depth of an impeller upper end to a depth of a hot metal pit is set to 0.6 to 0.8.