JPS6140011B2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a converter for top and bottom blowing.

In converter blowing, as the converter becomes larger, oxygen is top-blown, and at the same time tuyeres are installed below the surface of the molten steel in the furnace, and stirring gas is blown into the molten steel through the tuyeres, which is called top-bottom blowing. has become more common in recent years.

Stirring gas injected from below the surface of the molten steel promotes the flow of molten steel due to top-blown oxygen and promotes stirring of molten steel.
It promotes the reactivity of slag and molten steel and the formation of slag, but the effect varies greatly depending on the position of the tuyere. For example, if the tuyere is installed near the center of the furnace,
Although the molten steel is sufficiently stirred, the slag stays around the furnace wall, making it difficult to turn the slag into slag.On the other hand, if the tuyeres are placed away from the center of the furnace, slag stirring is relatively good. However, there are many difficult problems in setting the position, such as insufficient stirring of the molten steel, and no definitive answers have been obtained at present.

The difficulty in setting the tuyere position in top-bottom blowing is that it has not been long since top-bottom blowing began and sufficient experimental data have not been obtained, and the difficulty of setting the tuyere position in top-bottom blowing is due to the fact that top-blowing oxygen jets Problems unique to top-bottom blowing include the need to consider the relationship with stirring of molten steel, and the fact that there are certain restrictions on the flow rate of stirring gas and the type of gas in relation to top-blowing oxygen. It originates from

The present invention was achieved by repeatedly conducting various experiments and research in view of the current state of top-bottom blowing technology as described above.In particular, the present invention was developed by placing the tuyere at the position where the stirring efficiency is the highest in relation to the top-blowing oxygen jet. This provides a converter with a built-in converter.

For this purpose, the converter according to the present invention has a tuyere that has a circumference drawn by the intersection of the extension line of the oxygen jet from the top-blown oxygen lance and the furnace bottom, and the distance between the circumference and the inner periphery of the furnace wall. The basic feature is that it is placed between the circumference drawn by the 1/2 point.

FIG. 1 is a front sectional view of a converter according to the present invention, and FIG.
The figure is a plan sectional view. 1 is a furnace body, 2 is a top-blown oxygen lance, 3 is an oxygen jet, and 4 is molten steel. 5
is a tuyere, which is provided between circumference a and circumference b. This circumference a is a circumference of radius r drawn by the intersection A of the oxygen jet 3 and the furnace bottom 10. Also the circumference b
is the circumference drawn by a point half the distance from the circumference a to the inner circumference 11 of the furnace wall. Now, if the radius from the center of the furnace bottom to the furnace wall circumference 11 is R, the radius of the circumference b is R-r/2+r=R+r/2.

Since the circumference a varies depending on the position of the lance 2 and the spreading angle θ of the oxygen jet, its radius r
Calculate by using the formula below.

r=(+L)・tanθ However, L: Distance from the tip of the top-blowing oxygen lance 2 to the furnace bottom 10 (However, since it varies depending on the operating conditions and the number of charges, it is usually the maximum value for blowing): When manufacturing the nozzle Determining the center of expansion of the nozzle throat section By setting the position of the tuyere 5 as described above, extremely highly efficient stirring can be achieved.

Next, examples will be shown.

Example Steel production was carried out using a 180 TON converter with various tuyere positions. The actual dimensions and operating conditions of this converter were as follows.

L = 4000mm = 550mm θ = 6゜ R = 4000mm r = (550 + 4000) × tan6 = 478mm R + r / 2 = 2239mm Bottom blowing gas: Ar 20Nm ³ /min Lance nozzle size: 35mmφ 4 holes 6゜ Tuyere 5 size: 7mmφ single Figure 3 shows the relationship between the position of the tuyere 5 in the hole and the total Fe in the slag. Also, dephosphorization rate =
The relationship between hot metal P%-end point P%/hot metal P%×100 is shown in FIG. The position of the tuyere 5 indicates the distance from the center of the hearth,
In this example, the range of the present invention is from 478 mm to 2239 mm. In the case of the graph in Figure 3, the end point [C] is 0.05
%, and in the case of the graph in Figure 4, Total Fe=15%. These graphs show that when the tuyere 5 is located within the range of the present invention, T·Fe in the slag is low, the dephosphorization rate is high, and molten steel and slag are well stirred.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view showing an embodiment of a converter according to the present invention, Fig. 2 is a plan sectional view, and Fig. 3 shows the relationship between the distance from the center of the hearth bottom to the tuyere and T/Te in the slag. The graph shown in FIG. 4 is a graph showing the relationship between the distance from the center of the hearth bottom to the tuyere and the dephosphorization rate. In the figure, 1 is a furnace body, 2 is a top-blown oxygen lance, 3 is an oxygen jet, 4 is molten steel, and 5 is a tuyere.

Claims (1)

[Claims] 1. There is a blade between the circumference drawn by the intersection of the extension line of the oxygen jet from the top-blown oxygen lance and the furnace bottom, and the circumference drawn by the point 1/2 of the distance between the circumference and the inner circumference of the furnace wall. A converter for top and bottom blowing characterized by having a mouth.