JPH0339410A - Metal refining furnace - Google Patents

Abstract

PURPOSE:To sufficiently stir little quantity of molten metal without developing cavity of blowing gas by gradually reducing cross sectional area of molten metal storing part in a furnace from molten metal surface toward furnace bottom and making inner wall smooth in the molten metal storing part. CONSTITUTION:In furnace body of a metal refining furnace, such as converter 10, the inner diameter is max. at a furnace belly part, and a furnace opening part and the molten metal storing part (furnace bottom part) 13 are contracted respectively and as the whole, the shape of the furnace body is formed to be egg-shape. Molten iron is charged into the converter 10 while supplying gas to plural bottom blowing tuyeres 14. Auxiliary material is added to this and blowing of oxygen gas onto molten metal surface from a lance 16 is started. Then, the bottom blowing gas supplying quantity into the tuyeres 14 is increased to stir the molten metal. As ascending distance of the bottom blowing gas is lengthened, even if the quantity of charged molten metal is little, blowing through-out of gas is not developed and stirring force to the molten metal with gas can be improved. Further, consumption of lining brick 12 can be saved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a metal refining furnace for refining molten metal by blowing oxygen gas onto the surface of the molten metal while stirring the molten metal by gas bottom blowing, and in particular,
Concerning a converter for complex blowing.

[Prior art] In order to improve the blowing efficiency in a composite blowing furnace,
Gas is blown into the molten metal through the lining at the bottom of the furnace and stirred. The molten metal in the furnace is sufficiently stirred by oxygen gas top blowing and gas bottom blowing. As a result, the slag-metal reaction is promoted, and hot metal becomes high-quality molten steel in a short time.

As shown in Fig. 7, the conventional composite blowing furnace 1 has an almost same inner diameter from the bottom to the top of the furnace, except for the furnace mouth, and its vertical cross section has an overall shape resembling a pear. to do.

A plurality of bottom blowing tuyeres 4 are opened into the furnace through the iron skin 2 and refractory 3 at the bottom of the furnace, and stirring gas is blown into the molten steel 5 through these tuyeres 4.

However, in a converter with such a bottom shape,
Since the bottom of the furnace is almost flat and has a large area, when a small amount of molten metal is charged, the distance from the gas inlet to the molten metal surface becomes short, and the length for the stirring gas to pass through the molten metal is insufficient, causing the following problems. This causes various problems as shown below.

(1) Even when the amount of blown gas is limited to a small amount, gas cavities (gas blow-through to the molten metal surface) occur in the molten metal, making it difficult for slag to form.

(2) The molten metal is not stirred sufficiently and the refining time is prolonged.

(3) Uneven distribution of molten metal components occurs due to insufficient stirring.

Therefore, as shown in Fig. 8, the lining refractory 7 at the bottom of the furnace
The converter 6 has a multi-stage structure to narrow the bottom area of the furnace and increase the depth of the molten metal in the retention area even when blowing a small amount of molten metal.
The structure of has been improved.

According to such a converter 6, when the same amount of molten metal is charged, the molten metal depth L2 becomes deeper than the molten metal depth of the converter 1 described above, and the path of the gas is extended. Even if the amount of gas blown is increased, it becomes difficult to form cavities in the molten metal, and the gas stirring power improves.

[Problems to be Solved by the Invention] However, in the conventional converter where the bottom of the furnace has a multi-stage structure, the thickness of the refractory 7 at the bottom of the furnace becomes thicker than necessary, and the amount of refractory used in the entire converter decreases. increase Therefore, there is a problem in that the cost of refractories increases significantly.

This invention was made in view of the above circumstances, and
It is an object of the present invention to provide a metal smelting furnace that can sufficiently stir a small amount of molten metal without creating a cavity for blown gas, and can reduce the cost of refractories.

[Means for solving the problem] In order to improve the blowing efficiency of the converter, the area of the furnace should be made as wide as possible to increase the reaction interface area between oxygen gas and molten steel, while reducing the depth of the molten steel. It is necessary to deepen the depth and lengthen the path of the blown gas. On the other hand, a large converter has a capacity of 350 tons, and the amount of refractory used for its lining is enormous.

As a result of various studies on conventional converters with multistage structure bottoms, the inventors found that if the pear-shaped shell structure was used, the refractory lining at the bottom of the furnace would become excessively thick, resulting in a lot of waste. I found that it is impossible to avoid this. Therefore, the inventors conducted various researches to improve the gas stirring power by changing the steel shell structure at the bottom of the furnace and reducing the amount of refractory lining used, while aiming to improve the gas stirring power.

The metal smelting furnace according to the present invention is a metal smelting furnace that smelts the molten metal by blowing oxygen gas onto the surface of the molten metal while stirring the molten metal by gas bottom blowing, and in which the cross-sectional area of the molten metal retention section is directed from the surface of the molten metal toward the bottom of the furnace. It is characterized by the fact that the inner wall of the molten metal retention area is smooth as a whole.

[Function] In the metal refining furnace according to the present invention, the cross-sectional area of the molten metal retention portion gradually decreases from the surface toward the bottom of the furnace, and the inner wall of the molten metal retention portion is formed smoothly as a whole. Therefore, even if the amount of molten metal charged is small, the depth of the molten metal is deep, the distance from the gas blowing port to the scene is long, and the path of the blown gas is extended. Moreover, since the inner wall of the molten metal storage area is formed smoothly as a whole, the amount of lining refractory used is reduced.

[Example] Hereinafter, an example of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view schematically showing a composite blowing converter as a metal refining furnace according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view thereof. The outside of the converter 1o is covered with an iron shell 11,
A refractory material 12 is lined inside. The furnace body of the converter 10 has the largest inner diameter at the furnace belly, and the furnace mouth and the molten metal retention section (furnace bottom) 13 are each constricted to form an egg shape as a whole. A plurality of bottom blowing tuyeres 14 are provided at the lowest part of the retention section 13 so that stirring gas containing inert gas as a main component is blown into the molten metal 5.

As shown in FIG. 2, a plurality of tuyeres 14 are opened at appropriate locations in the retention section 13.

Next, with reference to FIG. 3, a case where composite blowing is performed using the above-mentioned converter will be explained.

After supplying a small amount of gas to the tuyere 14, hot metal is charged into the converter 10 from the ladle. Auxiliary raw materials such as lime are added to this, and oxygen gas is started to be sprayed onto the scene from the lance 16. At this time, the amount of bottom blowing gas supplied to the tuyere 14 is increased to stir the hot metal. [C] in the hot metal is combusted by the spraying of oxygen gas, and the reaction heat turns the auxiliary raw material into molten slag.

FIG. 4 is a graph showing the relationship between the inner diameter of the converter lining bricks on the horizontal axis and the depth of the steel bath on the vertical axis when charging the molten metal.

Figure 5 shows the results of various investigations into the relationship between the inner diameter of the converter lining bricks on the horizontal axis and the average superficial velocity in the furnace (the gas injection speed at which blow-through occurs) on the vertical axis. FIG. In the figure, curve F shows, for example, the amount of molten metal charged is 100 tons and the amount of gas blown is 8 tons per hour.
The results are shown when ONm3 is used.

In Figure 6, the horizontal axis represents the gas pressure P at the siding inlet,
The blown gas ff1Q is plotted on the vertical axis, and the inner diameter φ of the tuyere is varied in the range of 10.0 to 30.0iII, and the minimum depth of the steel bath at which gas blow-through occurs (the blow-through is the limit value H
; Unit: m).

As is clear from FIGS. 4 to 6 above, in the converter of the above embodiment, the depth of the steel bath can be increased, so the amount of blown gas Q can be increased. As a result, the stirring power of the bottom blowing gas has been greatly improved, and in conventional converters, when a small amount of hot metal is subjected to compound blowing, the gas blows through to the surface of the hot metal, forming slag and causing slopping. , I was able to effectively avoid this.

In addition, according to the converter of the above embodiment, the amount of lining refill gun 2 used is approximately 30% compared to a converter with a conventional multi-stage hearth bottom structure.
It was possible to reduce the refractory cost significantly.

[Effects of the Invention] According to the present invention, the path of the bottom blowing gas becomes longer, so gas blow-through does not occur even if the charged molten metal is small.
The power of stirring molten metal by gas can be greatly improved. Therefore, the reaction between the molten metal and the slag is promoted, and the combined blowing time can be significantly shortened.

Further, since gas blow-through does not occur, excessive forming of the slag is avoided, and problems such as slopping do not occur.

Furthermore, by changing the design of the furnace bottom, the amount of refractory lining used can be reduced by about 30% compared to the conventional method, resulting in a significant reduction in refractory cost.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view schematically showing a metal refining furnace according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of the metal refining furnace, and Fig. 3 is a schematic cross-sectional view of the metal refining furnace during complex blowing. 4th longitudinal cross-sectional view shown in
6 to 6 are graphs for explaining the invention in detail, and FIGS. 7 and 8 are longitudinal sectional views showing a conventional composite blowing furnace, respectively. 10: converter, 11: iron shell, 12: refractory, 13: molten metal retention section, 14: tuyere, 16: lance.

Claims (1)

[Claims] This is a metal refining furnace that refines the molten metal by blowing oxygen gas onto the surface of the molten metal while stirring the molten metal using gas bottom blowing. A metal smelting furnace characterized by an inner wall that is generally smooth.