JPS5891112A - Bottom blowing nozzle for converter - Google Patents

Abstract

PURPOSE:To obtain a titled nozzle capable of avoiding burnout in which an inner diameter of an effective blowing part of the blowing hole is decreased continuously from a top to a lower end by suitably maintaining a ratio of dynamic pressure of an inner tube gas to a static pressure of molten steel although the nozzle is in a tendency of decreasing its size due to the burnout. CONSTITUTION:The inner diameter (d) of the nozzle inner tube 4 consisting of a metal tube of real circle in inner sectional area is continuously decreased from the top U to the lower end L. A point of the top U means the top of an inner side of a furnace bottom 2 of the tube 4 standing up newly. A point of the end U means a length of the shortest nozzle in a max. burnout state enabling a practical use, and a part between them is defined as an effective blowing part l1. The inner diameter of the tube 4 can be discontinuously decreased toward the top, i.e. can be formed in stepwise. By using the bottom blowing nozzle of these structures, the ratio of a dynamic pressure of the inner tube gas to static pressure of the molten steel 1 can be made to a value indicated in an equation and the burnout of blocks surrounding the nozzle can be prevented.

Description

[Detailed description of the invention] The present invention relates to the structure of a converter bottom blowing nozzle.

Various types of converter blowing nozzles have been provided in the past, and among them, those with a metal tube structure in the form of a single tube or a heavy ore tube are known. Those with the same inner diameter are used.

Among them, for example, when determining the tube shape of a double tube structure, particularly the inner diameter of the inner tube, the following requirements are required in terms of design.

In other words, the inner diameter of the inner tube may be affected by the problem of insertion of molten steel or the instantaneous ejection of gas pt6 at the upper end of the nozzle, which is called a "pregnancy tap".
The dynamic pressure of the inner pipe gas and the static pressure of the molten copper are used to avoid the occurrence of intense welding due to the intermittent blowing of the nozzle and the upper surface of the bricks surrounding the nozzle, displacing the surrounding molten metal. It is designed so that the ratio to the pressure is expressed by the following equation (1).

Melt-static pressure ρ轡・BI・H ρg: Bottom blowing gas @ armpit (II quasi-state excitation) V: Inner pipe gas; y=f1m (8m shape 11) ρcrow:
Molten steel VB degree H: Molten bath method (-bath top surface to nozzle top end) g: 1
Here, the nozzle top m- means the nozzle position at which is the same as the top surface of the brick with the nozzle circumference H.

However, the fact that the filter paper nozzle Jidfl has a 5F-iron structure like other general furnaces is a persimmon, but rather the nozzle M
4181 will be the first melted copper. That is, j141-
As shown in , the depth H when the new furnace starts up at 9 o'clock O molten sea bream] becomes V)-/ due to the melting damage of the furnace bottom s2. There is no big difference between H and 14' as in #1, but as far as the level of the tuyere part 3 is concerned, the melting occurs earlier than the hearth bottom [2, and the level is 111 and H'. For this reason, the ratio of the dynamic pressure of the internal t-gas and the static pressure of the solution mentioned above deviates from the original design, and as a result, the rate of erosion of the nozzle increases due to the insertion of the melt, and the bottom-blowing nozzle This will cause trouble in converter inspection.

The present invention solves all of these defects, and even if some melting damage occurs and the nozzle becomes short and small, the ratio of the dynamic pressure of the inner pipe gas to the static pressure of molten copper is always at a desirable ratio of 3.5. This provides a nozzle structure that can maintain the

On the other hand, the argument for this is that the inner diameter of the effective blowing portion of the nozzle's blowing hole tapers discontinuously from the upper end to the lower end. It has a smaller structure.

The details will be explained below based on some examples.

FIG. 2 is a longitudinal cross-sectional view of a nozzle inner tube 4 having a tapered V-shape at the lower end and made of a metal tube with a perfectly circular internal cross section, according to the present invention.

In this case, the inner diameter d continuously decreases from the upper end sU to the lower end, which is a so-called tenosé.

Here, the point ff1lU at the upper end in FIG. 1 means the upper end of the inner side of the furnace bottom 2 at the time of new start-up, as indicated by the resistance.

In addition, the point at the lower end means the length of the shortest nozzle in the carp large erosion state that can be used practically, and the middle part of these means t - the effective blowing part! Set to 1.

The WLa diagram shows another structure according to the present invention, which tapers in a non-continuous manner as opposed to the continuous taper in FIG. It's stepped like a strata pattern.

Of course, between the steps, or between the 0 door and the step, or between the step and L.
Even if the inner diameter between the points is the same in the blowing direction, or is tapered, or even a combination thereof is essentially included in the technical idea of the present invention.

When designing the inner diameter of these nozzles, it is recommended to assemble them as shown in Figure 4.
The curved edge represents the nozzle inner pipe diameter di relative to the distance from the upper end of the nozzle, which is designed for the inner pipe gas flow filter of one nozzle 9.

As is clear from this, the diameter d of the nozzle inner pipe 4 is continuous or discontinuous within the range of the distance ^ from the upper end U to the lower end of the nozzle, depending on the inner pipe IHk flow rate Qg per nozzle. It is better to make it smaller.

According to our experience, practical nozzle dimensions are as follows.

That is, the nozzle inner diameter d is 10 to 34 mm, preferably 14 mm.
In the range of ~28-, the distance from the nozzle upper end U to the KabT steel sL* At is 0.5 to 1.0 m, preferably 06 to 0.
．． The range shall be 8m. The structure shown in Fig. 3 is for discontinuous inner diameter sound quality, and in this case, the amount of snow in the constant inner diameter portion is 0.4 m or more or 0.2 m or less.

Note that these examples are not limited to the double-tube structure, and can also be applied to a nozzle with an 11-tube structure.

Next *Shishi? ll is shown.

Molten steel bath at startup of new furnace & H: 1.85 m Molten steel temperature source after furnace bottom melting H': 1.85 to 1.90 m Molten steel bath depth at tuyere after melting H'': within 2.4 m pipe gas flow”
Qg: 40 ONm"/H/Nozzle Taper from the upper end of the nozzle to the lower end tM5: α8m Nozzle inner tube inner diameter d: 15.8 to 145 An example using one nozzle is shown in Fig. 5. Fig. 5 The horizontal axis shows the same number of nozzles used, and the vertical axis shows the melted insulation layer of the bottom-blown nozzle, and better results were obtained than with the conventional nozzle.

[Brief explanation of the drawing]

Figure 1 is a longitudinal sectional view of the bottom of the converter furnace. Fig. 2 is a sectional view of a nozzle in which the inner diameter of the nozzle is continuously reduced according to the present invention. The third factor is a sectional view of a nozzle in which the inner diameter of the nozzle is discontinuously reduced in accordance with the present invention. FIG. 5 is a chart showing the relationship between nozzle inner diameters. FIG. 5 is a chart showing the specific yield of the number of actual uses of the nozzle of the present invention and the conventional nozzle. 1 is the melt percentage, 2 is the furnace bottom, 3 is the tuyere, 4 is the nozzle inner tube, H is the depth of the molten copper bath at the time of startup of the forefurnace, H' is the depth of the molten copper bath after melting of the furnace bottom 2, Hl is the melt bath depth% of the tuyere part 3 after melt loss
dFi nozzle inner diameter inner diameter,! 1 is the distance from the upper end U to the lower end of the nozzle, ^ is the distance of the constant inner diameter part of the nozzle inner pipe when the inner diameter changes discontinuously, Qg is the main flow rate aP of the inner pipe per nozzle, U is the upper end of the nozzle, and L is the lower end of the nozzle. Representative patent attorney Masamitsu Akizawa and 2 others

Claims (1)

[Claims] (1) A converter bottom blowing nozzle characterized by having a structure in which the inner diameter of the effective blowing portion of the blowing hole decreases continuously or discontinuously from the upper yms toward the lower end.