JPH08165508A - Top-blowing lance for converter excellent in decarburization characteristic and refining method - Google Patents

Abstract

PURPOSE: To reduce (T.Fe) in slag at the time of stopping blowing and the generation quantity of dust, in a top-bottom combined blowing converter. CONSTITUTION: A top-blowing lance in the top-bottom combined blowing converter-type refining furnace has concentrical polygonal or concentrical circular cross section arranged with two to ten shield plates at the part of the tip opening surface. The ratio B/h of the long side length B (mm) to the short side length (h) (mm) of the individual opening hole part 2 separated by the shield plates 3, is 10 to 225, and it taking R (mm) for the lance diameter, one line of the slit oxygen supplying pipe having 0.4-4 of (B×h)/R, and 1-6 circular nozzles 4 arranged at the inside of the concentrical polygonal series or the concentrical circle and connected with the oxygen supplying piping independent of the slit oxygen supplying pipe, are formed. The lance body and the tip part of the lance containing the lance center point (a) are fitted through the shield plate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter top blowing lance having excellent decarburization characteristics in a top and bottom blowing converter and a refining method using the same.

[0002]

2. Description of the Related Art Generally, what is required for decarburization in a converter is that a small amount of dust is generated in a high carbon region, slag formation proceeds rapidly, and a decarbonation efficiency is high in a medium carbon region.
Decarburization proceeds by suppressing the generation of iron oxide to the low carbon region. Of these, the converter dust indicated by is generated from the surface (hot spot) where the top-blown oxygen and the steel bath collide, and is due to the evaporation of iron from the high-temperature hot spot and decarburization at the hot spot. It is said that there are two sources, one of which is generated by volume expansion when CO gas is generated by the reaction.

Conventionally, various methods have been proposed for reducing the amount of dust generated during blowing of a converter and increasing the iron yield. For example, Japanese Patent Application Laid-Open No. 2-156012 discloses a method of increasing the lance height and mixing an inert gas with the top-blown gas in order to reduce the dust generation amount. In this method, as the lance increases, the secondary combustion rate increases and the heat deposition efficiency decreases, so that the melting loss of the converter refractory becomes severe and the amount of inert gas used is large, which is a cost disadvantage. Become.

Also, "Materials and Processes" Vol. 7 (199)
4), p. 229 shows that the dust generation rate is governed by the oxygen supply rate divided by the fire point area. However, if the oxygen supply rate is reduced in order to reduce the oxygen supply rate per hot spot area, the productivity will decrease, and if the nozzle is made porous to increase the hot spot area, the hot spots will overlap and splash. When the lance height is increased, the secondary combustion rate is increased and the heat deposition efficiency is lowered, so that the melting loss of the converter refractory becomes severe.

On the other hand, Japanese Unexamined Patent Publication No. 62-228424 discloses a technique for increasing the secondary combustion rate by using an upper blowing lance nozzle having a large degree of deformation such as a star shape. No effect of this technique on reducing dust and splash is described, but simply applying this lance does not reduce dust. Summarizing such dust reduction techniques is to reduce the flow velocity of the oxygen jet reaching the bath surface, that is, so-called soft blow. However, in the soft-blown state, the stirring force due to the top-blown gas is small, and the temperature of the collision area (fire point) of the oxygen jet with the bath surface decreases, so the decarbonation efficiency decreases from the high carbon concentration area. However, there is a problem that the above purpose is not satisfied.

On the other hand, there has been proposed a technique for maintaining a high efficiency of decarboxylation even in the low carbon concentration range shown above. For example, JP-A-60-131908 and JP-A-60-63307 disclose a technique of mixing an upper-blown oxygen gas with an inert gas represented by Ar in an extremely low carbon region. However, since these methods require a large amount of Ar gas, there is a problem that the gas cost increases significantly.

Therefore, in order to satisfy the above-mentioned objects
It is best to supply a large flow of oxygen by soft blow in the high carbon region, a large flow of oxygen in the medium carbon region by hard blow, and a small amount of oxygen in the low carbon region by hard blow. . On the other hand, Japanese Patent Publication No. 47-477
No. 0 discloses a lance provided with a spindle having an actuating mechanism capable of moving up and down in a pipe line between a tip outlet part and a throat part of a circular oxygen nozzle of an upper blowing lance. In this case, oxygen flows through the slit formed in the gap between the circular nozzle and the spindle, but the jets after passing through the gap are always combined into a hard blow immediately after the outlet, so even if the gap is widened, the soft blow Blowing cannot be realized.

Further, in JP-A-1-123016, Ar or CO ₂ is provided outside the nozzle for supplying oxygen.
A lance having a nozzle for an inert gas, such as In this case, even if the oxygen flow rate is decreased, the flow velocity of the jet flow reaching the bath surface is not decreased by the inert gas, but since the oxygen gas is supplied from only one type of nozzle, the oxygen flow rate is greatly reduced. If it is lowered to 1, the clogging occurs due to the adhesion of metal to the nozzle. Therefore, the oxygen flow rate and the velocity of the oxygen jet reaching the bath surface cannot be changed significantly.

Further, Japanese Laid-Open Patent Publication No. 1-219116 discloses a lance having a main hole and a sub hole connected to an oxygen supply pipe independent of the main hole. The oxygen flow rate cannot be greatly reduced due to the problem of blockage due to the flow of oxygen, and since oxygen gas is supplied from both the main and auxiliary holes, the oxygen flow rate and the velocity of the oxygen jet reaching the bath surface can be greatly changed. It is not possible.

[0010]

The present invention is disclosed in JP-A-2-
In the methods disclosed in JP-A-156012, JP-A-60-131908 and JP-A-60-063307, there is a problem that the cost increases due to the large amount of inert gas used, and JP-A-62-228424. Dust is not reduced only by the method disclosed in Japanese Patent Publication No. JP-A No. 2004-187, and the problem that the iron oxidation loss in the medium carbon concentration range is large, and the method described in Japanese Patent Publication No. 47470/1972 only allows soft blow blowing. In the method disclosed in JP-A-1-123016 and JP-A-1-219116, the flow rate of oxygen and the flow velocity of oxygen jet reaching the bath surface are greatly changed. The purpose is to solve the problem of being unable to.

[0011]

According to the present invention, a gas emitted from a so-called elongated ejection hole having a large long-side to short-side ratio and an appropriate ejection hole shape is compared with a gas emitted from a circular hole. ,
A large decrease in the gas flow velocity immediately after the ejection causes soft blowing, and hard blowing is possible by combining the gas ejected from the elongated ejection hole with the gas ejected from another circular nozzle under appropriate conditions. It was made based on two new findings, and the summary is as follows.

(1) In a top-blown lance in a bottom-blown converter type refining furnace in which a steel bath is agitated by gas, a cross section of concentric 3 to 16 polygons or concentric circles 1
2 to a part of the opening surface of the tip of the slit-shaped oxygen supply pipe
1 to 6 provided inside the concentric polygonal or concentric oxygen supply pipe connected to an oxygen supply pipe having 10 shielding plates and an oxygen supply pipe independent of the slit-shaped oxygen supply pipe An upper-blown lance for a converter having excellent decarburization characteristics, characterized in that the lance main body and the lance tip including the lance center point are fixed through the shielding plate.

(2) The ratio B / h of the long side length B (mm) to the short side length h (mm) of each of the tip opening surfaces separated by the shielding plate is 10 to 225, and the lance diameter is R. (B × h) / R is 0.4 to 4 in the case of (mm), and the angle between the lance center point and the points of the two adjacent front end opening surfaces that are closest to each other. [omega] is 10 to 60 degrees, and the upper blowing lance for a converter is excellent in decarburization characteristics according to the above (1).

(3) The decarburization characteristic as described in (1) or (2) above, wherein the thickness of the shielding plate is 1 mm to 0.5 L with respect to the length L of the slit portion of the oxygen supply pipe. Excellent top blowing lance for converter. (4) The difference (θ−φ) between the inclination angle θ of the slit-shaped oxygen supply pipe with respect to the lance center line and the inclination angle φ of the circular nozzle center line with respect to the lance center line is 5 to 35 degrees. An upper-blown lance for a converter excellent in decarburization characteristics according to any one of (1) to (3).

(5) Using the upper blowing lance for a converter as described in any one of (1) to (4) above, the carbon concentration is 0.1.
In a region higher than 5 to 2.5%, 150 to 300 Nm ³ / Hr / ton of oxygen is supplied from the slit-shaped oxygen supply pipe,
From the circular nozzle, carbon dioxide or nitrogen gas of 5 to 40 Nm ³ / Hr / ton was supplied, and in the subsequent decarburization reaction region, 100 to 250 Nm from the slit-shaped oxygen supply pipe.
A refining method having excellent decarburization characteristics, which comprises supplying oxygen of ³ / Hr / ton and 10 to 50% of oxygen gas supplied from a slit-shaped oxygen supply pipe from a circular nozzle.

(6) In the region where the carbon concentration is lower than 0.05 to 0.3%, 10 to 50 is supplied from the slit-shaped oxygen supply pipe.
Nm ³ / Hr / ton carbon dioxide or Ar gas,
The refining method excellent in decarburization characteristics according to (5) above, wherein oxygen gas of 20 to 90 Nm ³ / Hr / ton is supplied from the circular nozzle. Here, the slit portion length L of the oxygen supply pipe is defined as the length of the slit-shaped oxygen supply pipe in the lance cross section. The pipe above the slit-shaped oxygen supply pipe for supplying oxygen to the slit-shaped oxygen supply pipe is preferably a pipe having a normal circular cross section with a small pressure loss.

[0017]

FIG. 1 shows an embodiment of the present invention.
FIG. 2 shows a cross section taken along the line AA 'of FIG. In order to attenuate the flow velocity of the gas discharged from the nozzle to enable soft blow, it is important that the nozzle has an elongated shape with a proper shape instead of a circular shape. Further, even if the gas ejected from the elongated nozzle is combined with the gas ejected from another nozzle, it is hard to be attenuated at the time of combination, and hard blow occurs. It is the present invention that utilizes this characteristic, and two elements of the optimization of the shape of the elongated nozzle that enables soft blow and the relationship between the elongated nozzle and the inner circular nozzle for properly performing the coalescence. It consists of

First, according to a detailed experimental study conducted by the present inventors regarding a method of attenuating the flow velocity of the gas discharged from the ejection holes, the following points are important. 1) A so-called elongated ejection hole having a large ratio of the long side (B) to the short side (h) of the tip opening surface of each slit-shaped oxygen supply pipe separated by the shielding plate. This is because the circumferential length of the jet cross section is longer than that of the gas emitted from the circular hole, and it is greatly affected by the interaction with the gas outside the jet, and a large damping effect is obtained immediately after the jet leaves the nozzle. . This effect is obtained when B / h is 10 or more. Also, B /
If h is larger than 225, piping of lance cooling water becomes difficult, which is not realistic.

2) The gas emitted from the elongated nozzle is
It has a characteristic that it is greatly attenuated immediately after it is ejected, but thereafter it is attenuated only at the 1/2 power of the distance from the nozzle tip. On the other hand, the gas emitted from the circular nozzle has a small attenuation immediately after being ejected, but thereafter, it attenuates at the first power of the distance from the nozzle tip. Therefore, it is necessary to convert the jet flow from the elongated shape to the circular cross-sectional shape after exiting from the nozzle in order to increase the subsequent attenuation while utilizing the characteristic of the above 1) that it greatly attenuates immediately after ejection. This condition is (B x
h) / R is to be 4 or less. Also, (B × h)
If / R is smaller than 0.4, it becomes difficult to maintain the machining accuracy of the nozzle, which is not realistic.

3) In the case of a multi-hole nozzle provided with a plurality of nozzles satisfying the above conditions 1) and 2), it is important not to combine jets from adjacent nozzles. One of the conditions is that The angle ω formed by the lance center point and the point of the two nozzles closest to each other is 10 to 60 degrees. If the angle ω is smaller than 10 degrees, the jets spread in the long-side direction merge with each other, and damping is less likely to occur after they merge, and if larger than 60 degrees, the opening area becomes small and the gas becomes smaller. The flow rate cannot be secured sufficiently. Further, as will be described later, since the individual nozzles are separated from each other by a shield plate having a limited thickness, if the angle ω is larger than 60 degrees, the shield plate area becomes large and the shield plate The amount of heat received becomes large, and the tendency of melting loss increases.

4) Further, in order to prevent the coalescence more completely, the region where the ejection holes have the shapes defined in the above 1) and 2) is limited to only the tip of the nozzle outlet. That is, even if the outer appearance of the tip is the same as that of FIG.
As shown in the section A-A 'of FIG. 3, the oxygen supply pipe itself does not have the cross-sectional shape defined in 1) and 2) above, but the oxygen supply pipe itself has a simple concentric polygonal or concentric circular cross-section. It is important that a thin shield plate is installed at the tip of the slit having the shape of, and only the tip of the nozzle has the cross-sectional shape defined in 1) and 2) above. In this case, the gas flow is disturbed just before the outlet, and a flow from the long side direction toward the inside of the nozzle is formed, so that there is an effect that the gas does not spread so much in the long side direction immediately after ejection. Regarding the thickness of the shielding plate, with respect to the slit portion length L of the oxygen supply pipe,
It needs to be 0.5 L or less, and if it is thicker than this, the turbulent flow effect just before the exit is not seen. Further, the lower limit is determined by the strength of the shielding plate, and it is desirable that it is substantially 1 mm or more.

The cross section of the oxygen supply pipe is a concentric polygon or a slit surrounded by concentric circles, and the concentric polygon is 3
The range is from a hexagon. This is because a polygon does not have a digon, and if the number of angles is larger than that of a hexagon, machining becomes difficult. When the number of shields is less than two, the long side (B) becomes very large,
If the number is more than 10, the long side (B) becomes very small, so in any case, B / h and B ×
h does not fall within the proper range, and no effect is obtained.

In the present invention, the lance body 1 and the tip of the lance including the lance center point a are fixed to each other via the shield plate 3, and the center point a moves vertically with respect to the lance body 1. There is nothing to do. Therefore, it is not necessary to provide a complicated drive mechanism according to the technique of dividing the lance tip portion including the center point a in the prior art into a lance body as a core and moving only the core up and down. The structure has the great advantage that the lance can be manufactured.

When the converter blowing is carried out in such an appropriate shape, soft blow which cannot be obtained by the conventional circular porous lance is possible, and therefore, the metallurgical effect of drastically reducing the dust can be obtained. . This is one of the causes of dust generation, that is, when the gas emitted from the nozzle collides with the molten metal surface, the kinetic energy causes the molten steel to scatter (splash-based dust). This is because the invention made it possible to avoid the soft blow.

However, if the soft blow state is continued up to a carbon concentration range of 1% or less, the oxidation of iron will increase. Therefore, in such a medium carbon range, the jet strength must be hard blow. For this purpose, it is necessary to supply gas from the circular nozzle at the center of the lance and combine this jet flow with the jet flow from the slit-shaped oxygen supply pipe. As shown in FIG. This can be achieved by setting the difference (θ−φ) between the inclination angle θ with respect to the line and the inclination angle φ with respect to the lance center line of the circular nozzle center line to 5 to 35 degrees.

Here, when (θ-φ) is smaller than 5 degrees, the slit-like oxygen supply pipe and the jet flow coming out of the circular nozzle are united immediately after the nozzle exit. Since the jet characteristics are the same, hard blow is possible, but there is a problem that violent splash and sloping occur. Further, when (θ-φ) is larger than 35 degrees, the jet flows from the slit-shaped oxygen supply pipe and the circular nozzle are hardly combined, and the hard blow effect cannot be obtained.

In this way, when the jet flow from the elongated slit-shaped oxygen supply pipe and the jet flow from the circular nozzle are combined, the jet flow tends to become a single jet due to its strong suction force. However, even though the center of the jet is a hard blow that maintains the characteristics of a circular nozzle, the outer periphery of the jet has the characteristics of the jet from the elongated slit-shaped oxygen supply pipe and has a large spread, so the fire point area is large. It has the property of becoming. As a result, there is an effect that the amount of dust is small even though it is a hard blow.

Next, the blowing conditions for obtaining the highest refining characteristics when using the above-mentioned top blowing lance having the appropriate conditions will be described in detail. First, in the high carbon concentration range, since sufficient carbon is present in the bath, a high decarboxylation efficiency can be obtained even by soft blowing. Therefore, it is optimal to carry out soft blow blowing for the purpose of reducing dust and promoting slag slag formation.

Specifically, the carbon concentration is 0.5 to 2.5%.
In the region higher than the above, it is 150
Oxygen of about 300 Nm ³ / Hr / ton will be supplied. Further, in this state, it is not necessary to flow gas from the circular nozzle in the center part, but in order to prevent the nozzle from being clogged with scattered metal or slag, it is possible to use 5 times from the circular nozzle.
Supply carbon dioxide or nitrogen gas of -40 Nm ³ / Hr / ton.

Here, when the carbon concentration is lower than 0.5% and the refining method in the medium carbon concentration region, which will be described later, is used, the oxidation loss of iron becomes large, and at a concentration higher than 2.5%. When the refining method in the medium carbon concentration range, which will be described later, is used, there arises a problem that the amount of dust increases. When the oxygen flowing from the slit-shaped oxygen supply pipe is lower than 150 Nm ³ / Hr / ton, the decarburization rate is slow and the productivity is poor, and when it is higher than 300 Nm ³ / Hr / ton, the CO generation rate is high. As the gas flow rate rises in the furnace, the amount of splash increases. When the gas from the circular nozzle is lower than 5 Nm ³ / Hr / ton,
Nozzles are clogged with scattered metal or slag, 40 Nm ³ /
If it is larger than Hr / ton, there is a problem that the gas supplied from the slit-shaped oxygen supply pipe interferes with and coalesces, and the soft blow effect cannot be obtained.

The gas supplied from the circular nozzle is carbon dioxide or nitrogen gas because it does not affect metallurgical properties such as decarburization reaction and is inexpensive. From the metallurgical point of view, Ar is also possible, but it is unrealistic because of high gas cost. Next, in the middle carbon concentration range in which the carbon concentration becomes lower than 0.5 to 2.5% and the decarburization reaction proceeds, carbon in the bath begins to decrease, so that stirring is weak when soft blowing is performed. As the flash point temperature decreases, the iron oxidation loss increases. Therefore, it is optimal to carry out hard blow blowing for the purpose of preventing the oxidation of iron.

Specifically, in the subsequent carbon concentration region, 100 to 250 Nm ³ /
The oxygen of Hr / ton is supplied from the circular nozzle, and 10 to 50% of the oxygen gas supplied from the slit-shaped oxygen supply pipe is supplied. Here, if the oxygen supplied from the slit-shaped oxygen supply pipe is smaller than 100 Nm ³ / Hr / ton, the jet flow from the slit-shaped oxygen supply pipe becomes too weak, and the jet flow from the circular nozzle is combined. Even if it does, the effect of hard blow is not obtained, and when it is more than 250 Nm ³ / Hr / ton, the combined flow velocity of the slit-shaped oxygen supply pipe and the jet flow from the circular nozzle becomes too high, so spitting Becomes fierce. Further, as shown in FIG. 4, when the oxygen gas supplied from the circular nozzle is less than 10% of the oxygen gas supplied from the slit-shaped oxygen supply pipe, the force for coalescing is weak and a hard blow effect is obtained. If it is not larger than 50% and the flow rate after coalescence is too high, spitting becomes violent.

When the number of circular nozzles is 7 or more,
The number of circular nozzles needs to be 1 to 6 because the flow rate of the gas discharged from each nozzle is reduced and the effect of coalescence cannot be obtained. Here, in order to satisfy the conditions of B / h and (B × h) / R and maximize the soft blow effect by the slit-shaped oxygen supply pipe while ensuring an opening cross-sectional area capable of supplying a large amount of oxygen gas, It is necessary to increase the average diameter of the concentric circles or the average diameter of the concentric polygon circumscribing circles to reduce h.
Therefore, it is desirable to dispose the slit-shaped oxygen supply pipe on the outer side of the lance and to provide the circular nozzle on the inner side. Also,
The diameter D (mm) of the circular nozzle is n (the number of nozzles), and the total area of the tip opening of the slit-shaped oxygen supply pipe is A (mm).
Is given by the equation (1), and α is 0.05 to 0.5
It is desirable that

D = {4α × A / (3.14 × n)} ^1/2 (1) When a plurality of circular nozzles are provided, the center points of the nozzles are arranged symmetrically with respect to the lance center. However, the total length V of the openings on the circumference is V /
It is desirable to arrange so that W is 0.3 to 0.7. Furthermore, a blowing method for obtaining the highest refining characteristics in the case of blowing to a further low carbon concentration range by using an upper blowing lance having this appropriate condition is shown. That is, in a region where the carbon concentration is lower than 0.05 to 0.3%, 10 to 50 Nm ³ / Hr / ton of carbon dioxide or Ar gas is supplied from the slit-shaped oxygen supply pipe, and 20 to 90 N is supplied from the circular nozzle.
Supplying oxygen gas of m ³ / Hr / ton.

Here, when the carbon concentration is changed to the above-mentioned proper conditions at a concentration lower than 0.05%, the oxidation loss of iron becomes large, and at the concentration higher than 0.3%, the above-mentioned proper conditions are changed. If you do, it is not realistic because the blowing time will be greatly extended. Oxygen gas supplied from the circular nozzle is 20
When it is less than Nm ³ / Hr / ton, it is not realistic because the blowing time is greatly extended, and it is 90 Nm ³
When it is larger than / Hr / ton, the iron oxidation loss becomes large.

The gas supply from the slit-shaped oxygen supply pipe is
This is not necessary for money, but it is necessary to prevent nozzle clogging.
It is important. Gas supply from slit-shaped oxygen supply pipe is 10
Nm ³If less than / Hr / ton, nozzle clogging
Occurs, 50 Nm³If more than / Hr / ton
Is expensive because it costs gas. Also,
As a gas, nitrogen is used to increase the nitrogen concentration in molten steel.
Cannot be used, and carbon dioxide or Ar gas is appropriate
is there.

By using the present invention, it becomes possible to reduce dust in a high carbon range, high decarboxylation efficiency in a medium carbon range, and decarburize to a low carbon concentration.

[0038]

【Example】

Example 1 The example used a 350 ton top and bottom blowing converter. As the bottom blowing gas, a mixed gas of oxygen and a tuyere cooling gas was used, and oxygen gas was supplied from a top blowing lance. The top blowing lance was based on the shape shown in FIG. 1, and the number of nozzles (openings), shape, spacing, and shield plate thickness were changed. The distance between the tip of the lance and the bath surface was 1 to 2.5 m, the dust concentration during blowing was measured from the amount of dust in the dust collecting water, and the average generation rate per blowing time was evaluated. In each case, the lance was used in which the lance body was fixed to the tip of the lance including the lance center point through the shield plate.

Test No. 1 is the lance (B = 1 shown in FIG.
00 mm, h = 2 mm, B / h = 50, (B × h) / R
= 1.2, shielding plate = 4 pieces, ω = 25 degrees, shielding plate thickness =
0.25 × L, θ−φ = 12 degrees, circular nozzle = 3,
Using the equation (1) α = 0.2, V / W = 0.4), in the region where the carbon concentration is higher than 1 to 1.5% (phase I), 200 to 250 Nm ³ from the slit-shaped oxygen supply pipe. / Hr / to
15Nm from the circular nozzle while supplying oxygen with n
Nitrogen is supplied at ³ / Hr / ton, and in a region where the carbon concentration is lower than that (stage II), the slit-like oxygen supply pipe supplies 150 to
Oxygen is supplied in even 40~70Nm ³ / Hr / ton from a circular nozzle supplies oxygen at 200Nm ³ / Hr / ton, was stopped blowing in carbon concentration of 0.04 to 0.07%.

As a result, the amount of dust generated is 0.81 to 0.
It was as low as 95 kg / (min · ton), the average decarboxylation efficiency in Phase II was high at 85 to 90%, and the (T · Fe) at the blowing stop was low at 8 to 12%. Similar results can be achieved with 1 circular nozzle
Also obtained in the case of 6 pieces (test number 2: α of formula (1) = 0.2), 6 pieces (test number 3: α of formula (1) = 0.2, V / W = 0.4) It was Further, when the concentric polygonal slit-shaped oxygen supply pipe shown in FIG. 5 is used in the same blowing pattern (test numbers 4 to 7: B, h, the number of shielding plates, ω, the shielding plate thickness, θ−φ, The number of circular nozzles, α in Formula (1), and V / W are the same as those in Test No. 1), and metallurgical characteristics substantially equivalent to the above were obtained.

On the other hand, when a circular porous lance having a combination of large and small diameters as shown in FIG. 6 is used (test number 8: the total opening area of the large diameter nozzle is the slit-shaped oxygen supply pipe of test number 1). The total opening area of the small-diameter nozzle is the same as the total opening area of the circular nozzle of test number 1). Although the oxygen was supplied at the same flow rate as the slit-shaped oxygen supply pipe of No. 1, the dust generation amount was as large as 2.21 to 2.35 kg / (min · ton), and the blow-stop (T · Fe) was Although it was 10 to 13%, the splash was severe and a problem in operation occurred. Furthermore, FIG.
When the center circular nozzle is not installed with the lance (Test No. 9) or when the number of circular nozzles is 7 (Test No. 1)
0), the amount of dust generated is 0.81 to 0.97 kg /
Although it is as small as (min / ton), the average decarboxylation efficiency in Phase II is low at 65-75%, and the blow-stop (T / Fe) is also 21.
It was as high as ~ 27%.

[0042]

[Table 1]

Example 2 Test Nos. 11 to 22 show examples of the present invention in which the lances shown in FIG. 1 were used to compare the amount of dust generated when the carbon concentration was 4 to 3%, and the oxygen supply rate was 200. ~ 250 Nm ³
/ Hr / ton, the circular nozzle was under the same conditions as Test No. 1. As in test numbers 11 to 17, the angle of the shielding plate,
Further, when both B / h and (B × h) / R of the opening are within the specified range of claim 2, further reduction of the dust amount is achieved. On the other hand, test numbers 18-2
2, the angle of the shielding plate and B / h of the opening,
It can be seen that if any of (B × h) / R deviates from the specified range of claim 2, the dust generation amount increases.

[0044]

[Table 2]

Example 3 In Example 3, the condition of test No. 11 of Example 2 (B = 100) was used.
mm, h = 2 mm, ω = 25 degrees, the number of shield plates = 4, the circular nozzle is the same as the test number 1), and the shield plate thickness is changed in the structure of FIG. It can be seen that the effect of reducing the dust is greater when the thickness is appropriate as in the case of Test No. 26.

[0046]

[Table 3]

Example 4 In Example 4, the difference (θ−φ) between the inclination angle θ of the slit-shaped oxygen supply pipe with respect to the lance center line and the inclination angle φ of the circular nozzle center line with respect to the lance center line was variously changed. This is a summary of the spray stop (T / Fe) and splash behavior in the case. The splash was judged from the adhesion of the metal at the furnace mouth after refining. The slit-shaped oxygen supply pipe is the third embodiment.
No. 24 of Test No., and only the angle was changed. The circular nozzle was the same as test number 1. Test number 31 with a small angle has a large amount of splash, and test number 32 with a large angle has a higher blow stop (T / Fe), compared to the case where the angle is appropriate as in test numbers 27 to 30. I understand.

[0048]

[Table 4]

Example 5 Next, an example of a method of blowing acid using the present invention will be described. The lance used was that used in Test No. 28. The region where oxygen was supplied from the slit-shaped oxygen supply pipe and carbon dioxide or nitrogen was supplied from the circular nozzle was designated as stage I, and the region where oxygen was supplied from both the slit-shaped oxygen supply pipe and the circular nozzle was designated as stage II. In addition, the concentration of blowout carbon is 0.03 to 0.06%
And Test Nos. 33 to 40 are tests under appropriate conditions, but it is understood that both the dust generation amount and the blow stop (T / Fe) are extremely low.

[0050]

[Table 5]

Example 6 The results obtained when various conditions of the circular nozzle were changed with the lance of test No. 28 are shown below. The propellant conditions are test number 3
Although the same as No. 3 was used, excellent metallurgical properties were obtained in all cases.

[0052]

[Table 6]

Example 7 The result of continuing blowing to a lower carbon region under the condition of Test No. 33 is shown below (the carbon concentration of blow-stopping is 150 to 250 p
pm). Here, the region in which oxygen is supplied from both the slit-shaped oxygen supply pipe and the circular nozzle was set as stage II, and the region in which carbon dioxide or Ar was supplied from the slit-shaped oxygen supply pipe and oxygen was supplied from the circular nozzle was set as stage III. Test Nos. 53 to 57 are tests under appropriate conditions, but it can be seen that (T · Fe) does not increase even though the blowing carbon concentration is extremely low.

[0054]

[Table 7]

[0055]

EFFECTS OF THE INVENTION By using the present invention, in upper and bottom blown converter refining, reduction of dust in high carbon region, high decarboxylation efficiency in middle carbon region and reduction of blowing stop (T / Fe), low It became possible to decarburize up to the carbon concentration.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a lance nozzle according to the present invention.

FIG. 2 is a diagram showing a cross section taken along the line AA ′ of FIG.

FIG. 3 is a difference (θ−φ) between an inclination angle θ of the slit-shaped oxygen supply pipe with respect to the lance center line and an inclination angle φ of the circular nozzle center line with respect to the lance center line, and (T · Fe) at the time of blowing stop.
FIG. 4 is a diagram showing the relationship of, where the blowout carbon concentration is 0.0
It was 4 to 0.06%.

FIG. 4 is a diagram showing the influence of the ratio of the flow rate of oxygen gas supplied from a circular nozzle to the flow rate of oxygen gas supplied from a slit-shaped oxygen supply pipe, which affects (T · Fe) at the time of blowing off. Here, the concentration of blow-off carbon is 0.04 to 0.06.
%.

FIG. 5 is a diagram showing another example of the lance nozzle according to the present invention in the case of having a concentric polygonal slit-shaped oxygen supply pipe.

FIG. 6 is a view showing a porous lance in which a large diameter nozzle and a small diameter nozzle are combined as a comparative example.

[Explanation of symbols]

1 Lance body 2 Gas ejection opening from slit-shaped oxygen supply pipe 3 Shielding plate 4 Circular nozzle B Long side length of each opening separated by a shielding plate h Each opening separated by a shielding plate Short side length a Lance center point ω Angle between the lance center point and the point on the circumference of the two adjacent openings that are closest to each other 12 Oxygen supply slit tube 13 Shielding plate 14 Circular lance L Oxygen Supply slit pipe length 21 Lance 22 Large diameter nozzle 23 Small diameter nozzle

Claims (6)

[Claims] 1. An upper blowing lance in an upper bottom blowing converter type refining furnace in which a steel bath is agitated by a gas, the concentric 3
~ 2 to 10 in a part of the front end opening surface of one slit-shaped oxygen supply pipe having a hexagonal polygonal or concentric cross section
Oxygen supply pipe where each shielding plate is arranged, and the slit-shaped oxygen supply pipe are provided inside the concentric polygonal or concentric oxygen supply pipes connected to an oxygen supply pipe independent from 1 to 1.
An upper blowing lance for a converter having excellent decarburizing characteristics, which has six circular nozzles, and a lance main body and a lance tip including a lance center point are fixed to each other through the shielding plate. 2. A ratio B / of a long side length B (mm) and a short side length h (mm) of each of the tip opening surfaces separated by a shield plate.
When h is 10 to 225 and the lance diameter is R (mm), (B × h) / R is 0.4 to 4, and the two adjacent tip opening surfaces are on the circumferences closest to each other. The upper blowing lance for a converter having excellent decarburizing characteristics according to claim 1, wherein an angle ω between the point and the center point of the lance is 10 to 60 degrees. 3. The transfer having excellent decarburization characteristics according to claim 1, wherein the thickness of the shielding plate is 1 mm to 0.5 L with respect to the slit portion length L of the oxygen supply pipe. Top blowing lance for furnace. 4. The difference (θ−φ) between the inclination angle θ of the slit-shaped oxygen supply pipe with respect to the lance center line and the inclination angle φ of the circular nozzle center line with respect to the lance center line is 5 to 35 degrees. The upper blowing lance for a converter excellent in decarburization characteristics according to any one of claims 1 to 3. 5. Using the upper blowing lance for a converter according to claim 1, the carbon concentration is 0.5 to 2.5.
15% higher than the slit-shaped oxygen supply pipe in the region higher than
Oxygen 0~300Nm ³ / Hr / ton, from the circular nozzle to supply carbon dioxide or nitrogen gas 5~40Nm ³ / Hr / ton, in the subsequent decarburization region, from a slit-shaped oxygen supply pipe 100-250 Nm ³ / Hr /
A refining method having excellent decarburization characteristics, characterized in that 10 to 50% of oxygen gas supplied from a slit-shaped oxygen supply pipe is supplied from a ton of oxygen from a circular nozzle. 6. In a region where the carbon concentration is lower than 0.05 to 0.3%, 10 to 50 Nm from the slit-shaped oxygen supply pipe.
³ / The Hr / 2 carbon dioxide or Ar gas ton, refining method having excellent decarburization characteristic of claim 5, wherein the supply of oxygen gas 20 to 90 nm ³ / Hr / ton from a circular nozzle .