JPS59104414A - Method for desiliconization of molten iron - Google Patents

Abstract

PURPOSE:To stabilize the efficiency of desiliconizing reaction at a high level, by adjusting the ratio of the running out speed of molten iron falling from a casting bed runner to a tilting runner and the passage sectional area of cylindrical molten iron passage body to a speific range in carrying out the desiliconization of molten iron by providing the cylindrical molten iron passage body between the casting bed runner of blast furnace and the tilting runner. CONSTITUTION:A cylindrical molten iron passage body 8, for example, discontinuously composed of refractory is provided to the casting bed runner 2 and between the blast furnace casting bed runner 2 and the tilting runner 3. The molten iron flow 7 containing desiliconizing agent is tapped into the tilting runner 3 via the cylindrical molten iron passage body 8 and the desiliconization of molten iron is carried out. In that time, the ratio of the tapping speed (kg/ min) and the passage sectional area (cm<2>) of cylindrical molten iron passage body shall be in a range of 2 to 20. When this ratio is <=2, sufficient desiliconizing oxygen efficiency can not be obtained and when it is >2, overflow of the molten metal is feared.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot metal desiliconization treatment method aimed at efficiently and stably desiliconizing hot metal in a blast furnace casthouse.

In recent years, with the increasing purity of molten steel and the upgrading of products, preliminary dephosphorization and desulfurization treatment of molten pig iron using soda ash or lime-based 7/-sox has been carried out. In this hot metal dephosphorization/desulfurization treatment, it is preferable that the hot metal Si content is as low as possible.
It is necessary to remove silicon to at least 0.15% or less.

BACKGROUND ART Conventionally, as a hot metal desiliconization method, a method for desiliconizing a cast bed in a blast furnace cast bed hot metal trough part using the natural falling energy of hot metal is well known.

As shown in Fig. 1, in this casting bed desiliconization method, hot metal flowing out from the blast furnace 1 is guided into the tobeed car 4 via the cast bed gutter 2 and the tilting gutter 3, and is stored in the hot iron 5. Since the desiliconizing agent (iron oxide) is fed onto the flow of hot metal in the cast bed trough 2 through the feeder 6, the mixing and stirring action of the molten metal and the desiliconizing agent in the cast bed trough is small, and the supply is slow. The desiliconizing agent, most of which floats on top of the hot metal, falls naturally into the next tilting trough 3, where it is stirred and mixed by its potential energy, and the desiliconizing reaction proceeds.

Therefore, the conventional castbed desiliconization method described above uses a free-fall method and stirs and mixes only near the so-called waterfall basin of the falling flow, so stirring and mixing between the desiliconizing agent and the hot metal is insufficient. It has the drawbacks of low reaction efficiency and large fluctuations.

Furthermore, another drawback of the conventional castbed desiliconization method is that when hot metal is injected from the tilting trough 3 into the torpedo car 4, the decarburization reaction caused by unreacted iron oxide (desiliconizing agent) The problem is that slag forming in the process is large, which limits the amount of iron oxide to be supplied, making it impossible to stably process Si to a low level.

The present invention has been made to solve all the problems of the conventional cast bed desiliconization method, such as low desiliconization reaction efficiency and large racking, and large slag 7 ohming in the tobead car, and has the following characteristics: However, several cylindrical molten metal channel bodies were installed in the channel through which hot metal containing a desiliconizing agent falls into the tilting gutter from the casting bed gutter, and the desiliconizing agent was added through the cylindrical molten metal channel body. By introducing the hot metal fully into the tilting culvert, the mixing and stirring of the hot metal with the desiliconizing agent is fully intensified, the desiliconizing reaction fully progresses, and the dispersion is eliminated and the desiliconizing reaction efficiency is stabilized at a high level.
．． The purpose is to prevent slag forming inside the torpedo car.

As a result of various researches conducted prior to the completion of the present invention, the present inventors found that the optimal mixing and stirring of the desiliconizing agent and hot metal is based on the channel cross-sectional area (, y4) of the cylindrical hot metal channel body. ) Atashi hot metal speed (
They found that this can be achieved when the ratio of K9/m) is within a certain range, and completed the present invention.

The conditions that the cylindrical molten metal channel body must meet are the outflow velocity W (Kg/-) of the hot metal falling from the casting bed trough to the tilting trough, and the channel cross-sectional area 5 (cfl) of the cylindrical molten metal channel body. The diameter of the channel cross section (inner tube) of the cylindrical molten metal channel body is determined so that the ratio #W/S is 2 to 20.

If the diameter of the cross section (inner tube) of the cylindrical molten metal channel body is larger than the above index of 20, the molten metal and desiliconization agent flowing back from the cast bed gutter will overflow from the cylindrical channel body. It is difficult to guide it to the tilting gutter without causing it to drop. In addition, if the diameter of the channel cross section (inner pipe) of the cylindrical molten metal channel body is smaller than 2 of the above index,
The desired purpose cannot be achieved due to insufficient mixing and stirring of the desiliconizing agent and hot metal.

The present invention will be explained below based on the drawings.

FIG. 2 is an explanatory diagram showing an embodiment of the present invention, and 2 is a cast bed gutter;
3 is the tilting gutter, from the tip of the 7tri cast bed gutter 2 to the tilting gutter 3
This is a hot metal stream containing a desiliconizing agent that flows out and falls into the molten metal.

FIG. 2(a) shows a cylindrical molten metal channel body, such as a cylindrical refractory, discontinuously attached to the cast bed gutter by an appropriate support member between the cast bed gutter 2 and the tilting gutter 3. A method of desiliconizing hot metal is shown in which the hot metal flow 7 containing a desiliconizing agent is guided to the tilting trough 3 through a pipe 8, and FIG. This figure shows a hot metal desiliconization method in which all the refractory pipes 9 are installed and melt #7 containing a desiliconizing agent flowing back from the cast bed @2 is continuously introduced into the refractory pipes 9.

Example: In the method shown in Fig. 2(a), the cast bed trough 2 and the tilting @3
．． ! A high alumina refractory pipe with an inner diameter of 500 taxis was installed between the refractory pipes, and desiliconization was performed continuously for 25 minutes through the refractory pipe at a tapping rate of s 10 Ton /=.The results are shown in Table 1.

Table 1 The desiliconization treatment method of this example had significantly improved desiliconization efficiency compared to the conventional method, and no slag 7 ohming phenomenon was observed in the torpedo car.

As described above, in the desiliconization treatment of the blast furnace casthouse, the cylindrical molten metal channel body 8 according to the present invention is used for the purpose of strengthening the mixing and stirring of hot metal and the desiliconizing agent in the process from the casting bed trough 2 to the tilting trough 3. The shape is not limited to the vertical tube shown in the examples shown in Figure 2 (a) and Figure 2 (1)), but also bent tubes, tubes with a change in inner diameter in the middle, etc. It is more desirable to use a cylindrical molten metal channel body 8 that has undergone various improvements for the purpose of enhancing the mixing and agitation of the molten metal.

In addition, the selection of W/S (hot metal speed CKy/m+)/channel cross-sectional area of the cylindrical molten metal channel body (cnl)] is one of the important requirements of the present invention from both the Si removal oxygen efficiency and workability. It is.

When W/S<l, there is almost no improvement in the Si removal oxygen efficiency.

Furthermore, as W/S increases, in the method shown in Figure 2 (a), the cross-sectional area of the immersion pipe becomes smaller relative to the amount of hot metal, so the melting needle is However, the oats may flow, leading to difficult operations. Therefore, W/S must be selected within the range of 2 to 2 degrees.

Among these, W/S of 5 to 10 is particularly desirable.

By configuring and using the present invention as described above, it is possible to achieve optimal mixing and stirring of the desiliconizing agent and hot metal, thereby promoting the full progress of the desiliconizing reaction and ultimately stabilizing the overall desulfurization reaction efficiency. Moreover, in addition to improving the quality of molten metal by suppressing slag forming inside the tobeed car,
Improvements within I also make a huge contribution.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional cylindrical furnace casting bed desiliconization process, and FIGS. 2(a) and 2(b) are explanatory diagrams showing a one-fire example of the castbed desiliconization process of the present invention. It is. 1...Blast furnace, 2...Cast bed gutter, 3...Tilt gutter, 4...
・・Tobeed car, 5・・Siliconizing agent storage hottuno ξ-16
...feeder, 7...melting needle flow containing a desiliconizing agent, 8,
9... Cylindrical pipe made of refractory material. Agent: Patent attorney Masaaki Akizawa, Mitsugai (2 people)

Claims (1)

[Scope of Claims] (11) A system for completely desiliconizing hot metal using a cylindrical molten metal channel body provided between the blast furnace cast bed trough and the tilting trough, either continuously or discontinuously in the blast furnace cast bed trough. , hot metal to which a desiliconizing agent has been added is added to the cylindrical molten metal flow path at a ratio of tapping rate (Kp/am)/flow path cross-sectional area of the cylindrical molten metal flow path body (,4) in the range of 2 to 20. A method for desiliconizing hot metal, which is characterized by passing it through a body.