JPS6199618A - Blowing tuyere of converter - Google Patents

Abstract

PURPOSE:To reduce the wear of refractories in the vicinity of the opening of a tuyere of a converter and to prolong the life of the converter by feeding protective gas from the narrow gap between the outer and inner tubes of the tuyere and refining gas from the spiral hollows in the inner tube. CONSTITUTION:A blowing tuyere of a converter is composed of a thin outer tube 1 and an inner tube 2 having prescribed hollows 4, and a narrow gap 3 is left between the tubes 1, 2. In the upper part of the inner tube 2, the hollows 4 are in a multiply spiral state. Protective gas is fed from the narrow gap 3, and refining gas from the hollows 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The technical content described in this specification regarding the improvement of the blowing tuyere of a bottom-blowing converter or a top-bottom blowing converter protects the scouring gas into a hot metal bath. The purpose of this paper is to present the results of research and development on the appropriate and advantageous realization of effective decarburization and other refining processes by injecting gas together.

(Conventional technology) Converter inside the hot metal bath housed in the converter! A double pipe tuyere is generally known as a blowing tuyere for a converter that bottom-blows the scouring gas from the bottom.

This two-tube tuyere is a fitting between an outer pipe and an inner pipe whose outer diameter is slightly smaller than the inner diameter of the outer pipe, and the refining gas such as pure 61 gas or a mixed gas with an inert gas is passed through the inner pipe. In many cases, a protective gas such as propane or other hydrocarbon gas is blown into the hot metal bath previously charged into the converter through the outer tube and the outer tube.

This double-tube tuyere has the advantage that the tuyere life is much longer than that of a Thomas converter because the storage gas is injected into the molten iron along with the refining gas. However, even when using this double-tube tuyere, the hearth refractory near the tuyere opening in the converter gradually wears out as the operation progresses, and the bottom refractory of the part away from the tuyere opening gradually wears out. There is a difference in the amount of wear and tear between the big one and the big one.

In other words, the life of the hearth bottom depends solely on the amount of wear and tear on the large hearth-proof material near the tuyere opening.

In addition, when producing low carbon steel, it is necessary to
A double pipe tuyere is required, but when blowing using a bottom blowing converter equipped with a double pipe tuyere with a large tuyere diameter, molten metal may leak into the tuyere if the blowing gas chamber is narrowed beyond a certain limit. Since there is a good chance of intrusion, the restriction of the blown gas is suppressed.

If a small double-tube tuyere is used, under operating conditions that require a large flow rate of blown gas, so-called blow-through will occur, reducing the iron yield due to spitting or slomping phenomena. degradation and damage to the furnace lining is inevitable.

In other words, the range in which the gas injection rate of the double-pipe tuyere whose tuyere diameter is set to a certain size is limited is limited, so the versatility is unsatisfactory.

In addition, even with double-pipe tuyeres with large tuyere diameters, blow-through still occurs when the blown gas flow rate is increased to achieve high-speed blowing, which limits productivity improvement. It counts as a point.

In this regard, in Japanese Patent Application Laid-Open No. 55-164 (No. 118),
In order to obtain a double pipe tuyere with a wide wall that can be changed by adjusting the refining gas blower, a collection pipe bundle made by instantaneously joining multiple small diameter pipes is twisted at a predetermined angle. ,
This collecting pipe bundle is inserted into the outer pipe 8, and the scouring gas is blown from each small diameter pipe and the protective gas is blown from the gap between the collecting pipe bundle and the outer pipe 8. By twisting the collecting pipe bundle, a large flow of refining gas can be injected. This structure does not cause blow-through, and also prevents the intrusion of molten metal by restricting the gas flow rate.

However, in this case, the ratio (S out
Out/S in ) is approximately 0.5 N degrees Gc. Due to the structural constraints of arranging multiple small diameter pipes in the outer pipe, it is not possible to make the above ratio smaller.
The flow cross-sectional area of the protective gas is too large compared to about 0.25 in a normal double-tube tuyere, resulting in the following problem.

In other words, if you try to make the flow rate of the protective gas to the refining gas similar to that of a normal double-pipe tuyere, the flow rate of the protective gas will be about % of that when using a normal double-pipe tuyere. As a result, there is a danger that molten iron may be inserted into the h-holding gas blowout opening, and to avoid such a danger, it is necessary to increase the flow rate of the protective gas to the same level as a normal double-pipe tuyere. On the other hand, the applicant previously proposed in Japanese Patent Application No. 142,975/1983 that a plurality of concentric double tubes with small tuyere diameters are connected to each other in an adjacent outer space. We proposed twisting the tubes so that they join together, and inserting a spacer between the outer and inner tubes to maintain the concentric relationship described above.

In this way, the wear and tear of the heavy-duty materials near the bottom of the converter can be alleviated, extending the life of the bottom while expanding the range in which the amount of gas injection can be adjusted. Therefore, in order to perform high-speed blowing, which is useful for improving productivity, it has versatility without any problems like blow-through even when the blown gas flow gk is increased, and it is economical because the protective gas flow rate is the same as that of a normal double-pipe tuyere. I was able to achieve this by combining my gender.

However, the inventors conducted further research and found that when high-speed blowing is performed or when lime powder is mixed into the refining gas for purposes such as dephosphorization, the pressure drop in the refining gas caused by the twisting of the small diameter inner pipe is large. It was found that wear of the inner wall of the inner tube occurs due to this.

This wear is significant when a soft material such as steel, which is easily twisted, is used. In other words, although the advantage of alleviating wear and tear on the bottom refractory near the opening of the inner blade of the converter is not lost, the wear of the inner wall of the inner tube due to the twisting of the tuyere progresses, and if oxygen gas penetrates the inner tube, When this happens, there is a risk that the propane gas, which is used as a protective gas, enters the flow path and causes a gas explosion, causing a major accident, and the life of the tuyere decreases, which is inconvenient, forcing the tuyere to be replaced at an early stage.

(Problems to be Solved by the Invention) In view of the above-mentioned conventional development circumstances, this invention is based on the premise of alleviating the wear and tear of the bottom refractory near the blade opening in the transfer furnace and extending the life of the bottom. As a result, there is a wide range in which the blowing conditions can be adjusted by changing the gas injection group, and therefore it is highly versatile, and the blowing gas flow rate is increased to perform high-speed blowing to improve productivity. Even when lime powder is flowed at high speed together with refining gas for purposes such as dephosphorization, there is almost no wear on the inner wall of the inner pipe due to blow-through or twisting, and the flow rate of the protective gas is the same as that of a normal double-pipe tuyere. The object of the present invention is to provide a blowing tuyere for a converter that can reduce the production cost by reducing the production cost.

(Means for Solving the Problems) The present invention comprises a hollow, porous inner cylinder in which a narrow gap is formed between a thin outer cylinder and its inner surface, and the pores are formed in at least an end region of the inner cylinder. It forms a multiple spiral shape and opens at the end surface of the inner surface,
This blowing tuyere for a converter is characterized in that the narrow gap is used for a protective gas and the porous holes are used for a refining gas supply passage.

The blowing tuyeres of the converter of this invention are as shown in the cross section of the embodiment in FIG. li1 and a porous hollow inner cylinder 2 inserted into the thin outer cylinder 1. The thin outer surface 1 forms a narrow gap 3 between the inner surface and the outer periphery of the inner surface 2, much like the outer tube of a conventional concentric double tube.

The inner surface 2 is a porous hollow body in which, in the illustrated example, eight holes are arranged, which form a multi-spiral shape at least in the end region and are open to the end surface of the inner surface 2.

In this example, the inner cylinder 2 is provided with 3. A helical core is set in the form of a twisted spiral at intervals, and molten metal is injected and solidified around the core, and the helical core is pulled out to form a porous hollow shape. Reference numeral 6 in the figure indicates the gold-filled body obtained in this manner.

Inner 1'12 is also shown in Figure 2, in place of the above-mentioned spiral core, there are eight kinkei tubes east 7 twisted together to create a similar appearance.
A porous hollow shape may be formed around the molten metal as a filler by injecting and solidifying molten metal around it in a manner similar to the above-mentioned process. Kinpeng outer skin 5 [removed, filling body 6 is directly outside H
The case where a narrow @8 is formed between the inner surface of In either case, the filling body 6 forming the multiple spiral shape of the inner cylinder 2 and defining the hole 4 having the opening T contains a highly wear-resistant and hard material such as Qr, Ni.Mo, or V. Cast steel and other materials such as ceramics, which have excellent wear resistance, are also suitable.

(The inner cylinder 2 is held and fixed within the outer surface l of the action, the protective gas is inserted in the pincer @1, and the end ggi area of the inner cylinder 2 is formed into a multiple spiral shape and the inner cylinder W1z
The refining gas is passed through a plurality of holes 4 opened in the end face of the blowing tuyere according to the present invention.
-Tuyere shown in specification No. 1429'LS (see Figure 3)
Blowing is carried out by blowing 5 into a bottom blowing converter using 5
Heat was applied, and after the experiment, the wear on the refining gas passage wall due to the twisting of both tuyeres was compared.

The material of the blowing tuyere of this invention is that both the outer cylinder l and the metal outer skin 5 are made of Ciu, and the metal optical fiber body 6 in the inner cylinder 2 is made of 27% O.
r-Ni%Mo, Vf14 Niyorumotoshi. Here, the inner diameter of the hole 4 is 10 mm, the helical angle is 25 degrees, the inner surface 2 has an outer diameter of 1.5 mm, the length is 400 mm, the thickness of the outer skin 5 is 1.5 mm, and the outer cylinder 1 is 1.5 mm thick. Inner diameter 44.4 φ, wall thickness 2
．． 0M, and therefore the width of the narrow gap 8 is 0.7 silk. The rlIi flow for the tuyeres is 31 for each of the holes 4.
1i1117m1n, thus totaling 9 Nm
"/mj-n, and the ratio of the propane flow rate to this oxygen flow rate was 4%, and the injection was made from the narrow gap 3. On the other hand, the tuyere used for comparison had an inner diameter of 144 m and a wall thickness of 2 gl5.
Both the outer tube and the inner tube 8 with an inner diameter IQms and a wall thickness of 1.5 m are made of Cu1I, and the outer tube and inner tube 8 are aligned with the axis of the tuyere over a range R of 400 meters downward from the open end of the furnace bottom g. It is formed by twisting each other at an angle of 25°. Here, the spacer 9 has a width of 3 m.

One inner pipe was installed at a height of 0.4 m. In other words, the flow path cross section rfJ product through which the refining gas and the protective gas flow are made the same for both tuyeres.

The blowing conditions are as follows.

0/4.4~4.6%, Si/0.2~O-5
%, Mn 10.4-0.6%, Plo, 1-0.1δ
%, S10.007-13.020%, blowing was performed on 5.0-5.6 tons of hot metal at a temperature of 1250-1320°C, C10.04% or less, Si7 tr%
7+(n 70.2-0.3%, Plo, 01-0.
Molten steel having a composition of 0.03% and S10.006 to 0.0015% and a temperature of 1680 to 1720°C was obtained.

The oxygen supply rate during this blowing is I B Ns+'/min,
In the first half and second half of blowing, 9 cao for each 250
The powder was blown in at a high speed of 50 kg/min.

Blowing was performed under the above conditions, and the amount of wear was investigated after the experiment. The results are shown in Table 1.

Table 1 Note) T shown as average per inner tube.

As shown in Table 1, the amount of wear of the comparative tuyere is 700μ1
After five heats, the inner tube was worn down to about half of its wall thickness.

However, according to this invention, the amount of wear is very small at 10μ15 heats. In addition, when we observed the hearth bottom after the experiment, we found that both the tuyere of the first invention and the comparative tuyere were 1□5. Yo. . , Do□Yo□, 5□1, the corrosion resistance of the large furnace bottom material was not lost.

As a result of calculating the iron yield between 5 people by Zaranijikyo using the following formula, the iron yield is as high as 90 to 94%. It became clear that it was preserved.

(Effects of the Invention) As described above, the blowing tuyere of the present invention alleviates the wear and tear of the bottom refractory near the opening part inside the converter, extends the life of the bottom, and makes it possible to reduce the damage inside the tuyere. This method avoids gas explosion accidents caused by the merging of acidic gas flowing through the pipe and propane gas flowing between the inner and outer pipes of the tuyeres, and allows adjustment by changing the gas injection density. Since I is wide, it is versatile, and lime powder can be used at high speed with refining gas for purposes such as increasing the blown gas amount for high-speed blowing and dephosphorization in order to improve productivity. Even when flowing, there is almost no wear of the inner tube due to blow-through or twisting, and the amount of koji gas r/#J is about the same as that of a normal 2-kyo tube tuyere, reducing production costs. be able to.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a blowing tuyere for a converter according to the present invention, ZFA is a cross-sectional view of another specific example, and FIG. 8 is a cross-sectional view of a comparative tuyere. 1... Thin outer WR 2... Inner surface 8... Narrow gap Sound... Hole Patent applicant Kawasaki Steel Corporation Figure 1

Claims (1)

[Claims] 1. It consists of a porous hollow inner cylinder with a narrow gap formed between a thin outer cylinder and its inner surface, and the pores form a multi-spiral shape at least in the end region of the inner cylinder, and the end surface of the inner cylinder A blowing tuyere for a converter, characterized in that it is open, the narrow gap is used for a protective gas supply passage, and the porous hole is used for a refining gas supply passage.