JP2014208866A - Top blown lance for refining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a top blown lance in which the wear of a lance hole caused by dephosphorization refining agent powder can be suppressed by top-blowing the dephosphorization refining agent powder from a central hole as possible, and further, bullion insertion into the central hole after the stop of an Ncarrier can be evaded even if the Ncarrier is stopped during a period in which the dephosphorization refining agent powder is not top-blown.SOLUTION: Provided is a top blown lance 1 for refining comprising: a first passage 12 for feeding the dephosphorization refining agent powder together with a gas for transportation; a second passage 13 arranged around the first passage 12 and feeding an oxygen gas; a central hole 9 arranged at a lance tip part 7 at the lower part of the first passage 12; and a plurality of main holes 10 arranged at the lance tip part 7 connectedly with the second passage 13, in which the dephosphorization refining agent powder and gas are blown to a molten iron bath face. The part directly on the central hole 9 is provided with an opening part 11 communicating the first passage 12 and the second passage 13.

Description

  The present invention relates to a refining top blow lance, and more particularly to a refining top blow lance that blows refining flux powder and gas onto a hot metal bath surface.

  In recent years, a technology has been proposed in which lime-based dephosphorizing refining agent is powdered and sprayed from the top lance to the hot metal bath surface to promote hatching, and efficient dephosphorizing treatment with less lime-based dephosphorizing refining agent has been proposed. Yes.

For example, Patent Document 1 discloses a method of spraying CaO-based dephosphorizing refining agent powder from a central hole of an upper blowing lance onto hot metal using N ₂ gas as a carrier. At that time, O ₂ gas is blown from a plurality of main holes arranged around the center hole. There are mainly two reasons for spraying the dephosphorizing refining agent powder from the center hole and N ₂ gas as a carrier.

One is that when the dephosphorizing refining agent powder contains hard powder such as Al ₂ O ₃ or iron oxide-containing agent powder, the wear of the nozzle for discharging the dephosphorizing refining agent powder becomes remarkable. In particular, since the main hole has an inclination angle with respect to the center axis of the lance, the proportion of the powder that collides with the main hole wall when the dephosphorizing refining agent powder passes through the main hole is high, and is prominent locally. Wear occurs. For this reason, the nozzle center axis coincides with the lance center axis, and the dephosphorizing refining agent powder that collides with the nozzle wall is sprayed from the center hole where the ratio is low.

The other is to use N ₂ gas for the carrier in order to prevent the piping from burning due to the spark generated when the iron oxide-containing agent such as iron ore contained in the dephosphorizing agent comes into contact with the supply piping. In addition, since the steel pipe is normally used for the supply piping, the combustion should just be prevented. Therefore, as the carrier gas, in addition to N ₂ , an inert gas or an inert gas having a small O ₂ content may be used.

However, when the above method is used, it is necessary to continue blowing N ₂ gas even during a period in which the dephosphorizing refining agent powder is not blown up to avoid nozzle clogging and nozzle wall melting due to intrusion of metal into the center hole. . For this reason, an increase in cost due to an increase in the amount of N ₂ gas used occurs, and a problem arises in that an increase in N _{2 in} the molten steel is unavoidable in decarburization blowing.

JP 2011-1585 A

In order to prevent the piping from burning due to the spark generated in contact with the supply piping when spraying the dephosphorizing refining agent powder containing hard powder such as Al ₂ O ₃ and iron oxide from the top blowing lance to the hot metal, N ₂ gas is used for the carrier. The dephosphorizing agent powder contains 50% or more of the CaO component by mass concentration, and may contain Al ₂ O ₃ , FeO, and Fe ₂ O ₃ as other components. Furthermore, the CaO component may be included as CaCO _3, or may be a component contained in the converter slag. Typically, quick lime powder and limestone powder, or a mixed powder of them with natural minerals such as bauxite and iron ore, and converter slag are exemplified.

  The particle size of the dephosphorizing refining agent powder contains 50 mass% or more of CaO as a single substance in consideration of the role of reaction in refining, reaction efficiency, suppression of wear in the supply path, ease of conveyance by gas, etc. The limestone powder, bauxite powder, iron ore powder, converter slag powder, etc. all have a maximum particle size of 0.5 mm or less, except that the maximum particle size of the quick lime powder is 1 mm or less.

  Further, in order to suppress wear of the powder discharge hole at the tip of the lance due to the above-described dephosphorizing refining agent powder, the dephosphorizing powder is blown up from the center hole where the lance shaft core and the nozzle shaft core coincide as much as possible.

Then, a period that does not blow on the dephosphorization agent powder, stops N ₂ which is a carrier gas.
Up to now, there has been no refining top blow lance that satisfies all of the above conditions, suppresses the wear of the nozzle wall and increases the amount of N ₂ used, and prevents the nozzle wall from being melted and operates stably.

  As a result of intensive studies in order to solve the above problems, the present inventors have obtained knowledge A to C listed below and completed the present invention.

(A) Supplying the dephosphorizing refining agent powder to the hot metal bath surface to the upper part of the powder discharge nozzle arranged at the tip of the lance through the inside of the central tube where the axis of the upper lance coincides with the axis. When transporting together with the carrier gas, and then by a method of spraying onto the hot metal bath surface through a powder discharge nozzle (center hole) where the shaft core matches the lance shaft core arranged at the tip of the lance,
Even if the lance center pipe that transports the dephosphorizing powder is not completely connected to the center hole, and there is an opening in the connection, the dephosphorizing powder is discharged from the lance center pipe. After that, most of it moves to the powder discharge nozzle (center hole) and is discharged from the tip of the lance. In this case, the main hole for O ₂ gas discharge arranged around the powder discharge nozzle (center hole) has a normal angle (10 ° to 15 °) with respect to the lance axis. However, significant wear due to the dephosphorizing refining agent powder can be avoided.

(B) In the case where an opening is present between the central hole of the lance for conveying the dephosphorizing refining agent powder and the central hole, the carrier gas N is stopped after the top blowing of the dephosphorizing refining agent powder is stopped. When stopping the supply of the _2, O ₂ gas was fed into the main hole of the O ₂ gas ejection arranged around through said outer pipe of the lance core tube of a powder ejection nozzle (center hole) is, the opening It will come to discharge from a center hole through a part. Therefore, it is possible to avoid bullion feed of the N ₂ stopped after also the center hole (the phenomenon of adhesion hot metal rebounded).

(C) when blown on the dephosphorization refining agent powder, since the N ₂ gas and O ₂ gas are mixed through the powder discharge nozzle (central hole) the opening of the upper, from the center hole N ₂ gas and O ₂ The dephosphorizing refining agent powder is discharged using a gas mixture as a carrier. As a result, when there is a metal insert in the center hole, the molten iron grains and the O ₂ gas in the mixed gas come into contact with the metal insert part, but it is difficult to burn the tip portion of the lance. By using copper or a copper alloy, it is possible to avoid the problem of piping burning.

The present invention is listed below.
(1) a first path for supplying the dephosphorizing refining agent powder together with the carrier gas;
A second path disposed around the first path for supplying oxygen gas;
A central hole located at the tip of the lance below the first path;
A plurality of main holes connected to the second path and disposed at the tip of the lance,
In a refining top blowing lance that sprays dephosphorizing refining agent powder and gas on the hot metal bath surface,
An upper blow lance for refining comprising an opening for communicating the first path and the second path directly above the center hole.

(2) The cross-sectional area (S ₁ ) of the opening is S ₂ ≦ S ₁ ≦ 4 × S ₂ with respect to the cross-sectional area (S ₂ ) at the tip of the central hole (1) The top blow lance for refining described in the item.

(3) In the refining method of spraying the dephosphorizing refining agent powder and gas on the hot metal bath surface using the top blowing lance for refining described in the item (1) or (2),
The gas carrying the dephosphorizing refining agent powder in the first path is any one or more of air, reducing gas, carbon dioxide gas, non-oxidizing gas or rare gas. Refining method.

  According to the present invention, most of the dephosphorizing refining powder can be discharged from the powder discharge nozzle (center hole), so that significant wear of the lance main hole due to the dephosphorizing refining powder can be avoided.

In addition, according to the present invention, even if the N ₂ gas is stopped after the top spraying of the dephosphorizing refining agent powder is stopped, the O ₂ gas for the main hole in the lance is the opening between the powder conveying pipe and the central hole. since discharged from the central bore through, it can be avoided bullion feed into N ₂ when stopping the central hole.

For this reason, according to the present invention, the amount of N ₂ gas can be reduced and the cost can be reduced, and the N ₂ gas can be stopped in the middle of blowing, so N up in the molten steel can be avoided. The lance of the present invention can be used.

FIG. 1 is a longitudinal sectional view showing an outline of the structure of a lance tip portion of a refining top blow lance according to the present invention. FIG. 2 is a plan view showing an outline of the most advanced lance of the refining top blow lance according to the present invention. 3A is a perspective view showing one aspect of the periphery of the opening in a transparent state, FIG. 3B is a cross-sectional view taken along the line AA in FIG. 3A, and FIG. FIG. 3 is a perspective view showing another embodiment around the opening in a transparent state, and FIG. 3D is a cross-sectional view taken along line AA in FIG.

A refining top blow lance according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a longitudinal sectional view showing an outline of the structure of a lance tip portion 2 of a refining top blow lance 1 according to the present invention. FIG. 2 is a plan view showing an outline of the most advanced lance of the refining top blow lance 1 according to the present invention. The refining top blow lance 1 according to the present invention has a central hole 9 that is a powder discharge nozzle. An example of the nozzle arrangement in the case of a converter lance having five main holes 10 as well as two main holes 10 is shown.

  The lance 1 includes an outer tube 6, and pipes 3, 4, 5 and a tip 7 inside the outer tube 6. The pipe 3 is a lance center pipe, and the pipe 4 is arranged outside thereof, the pipe 5 is arranged outside the pipe 4, and the pipe 6 is arranged outside the pipe 5.

The dephosphorization refining agent powder flows through the first path 12 inside the pipe 3 using N ₂ gas as a carrier. That is, a powder discharge nozzle 9 (center hole 9) whose axial center matches the axial center is arranged directly below the central tube 3 whose axial center matches the axial center of the upper blowing lance. The dephosphorizing refining agent powder is transported through the (first path 12), and most of the dephosphorizing refining agent powder is discharged from the center hole 9.

The carrier gas of the dephosphorizing refining agent powder is basically N ₂ , but any one or more of air, reducing gas, carbon dioxide gas, non-oxidizing gas, rare gas, or those A mixed gas with N ₂ may also be used. In the following description, as shown in FIG. 1, the inner diameter of the center tube 3 is d1.

O ₂ gas flows through the _second flow path 13 between the central pipe 3 and the pipe 4. That is, O ₂ gas is caused to flow through the _second path 13 which is a gap between the central pipe 3 and the pipe 4, and most of the O ₂ gas is discharged from a plurality of main holes 10 arranged around the central hole 9.

  Further, cooling water flows between the pipe 4 and the outer pipe 6 using the pipe 5 as a partition. In the lance 1 shown in FIG. 1, the cooling water feed path is between the pipe 4 and the pipe 5, and the cooling water between the pipe 5 and the outer pipe 6 is the return path.

  The tip 7 is attached to the tip 2 of the lance 1. A center hole 9 is formed in the center of the tip portion 7 so that the lance axis coincides with the axis, and a plurality of main holes 10 are equiangularly arranged around the lance center axis at the same angle. Formed with. The lance tip 7 is preferably made of Cu or Cu alloy, which has high thermal conductivity and is difficult to burn. In the following description, as shown in FIG. 1, the inner diameter of the central tube 3 is d1, the incoming diameter of the central hole 9 is d2, the outgoing diameter is d4, and the diameter in the middle of the central hole 9 is Let d3.

Thus, the lance 1 is arranged around the first path 12 for supplying the refining agent powder together with the carrier gas, and the second path for supplying the O ₂ gas around the first path 12. A path 13, a center hole 9 disposed in the lance tip 7 below the first path 12, and a plurality of main holes 10 connected to the second path and disposed in the lance tip 7. Used to spray refining agent powder and gas on the hot metal bath surface.

  In the lance 1, an opening 11 having a length L in the vertical direction is provided immediately above the center hole 9 (between the tip of the center tube 3 and the tip 7). The shape of the opening 11 is not particularly limited. However, in the case of a hole shape, the number of holes is set to 3 or more (preferably the cross-sectional area of each hole is the same and the shape is also the same), and the lance 1 The center of each hole is on the same lance cross section immediately above the tip portion 7 of the lance, and the center position of each hole is from the upper surface of the lance tip portion 7 (inlet surface of the center hole 9) to (d1) / 2. (D1) It is desirable to arrange each hole at a symmetrical position with respect to the center axis of the lance. If the holes are not arranged at symmetrical positions, the flow direction of the dephosphorizing refining agent powder discharged from the tip of the central tube 3 to the central hole 9 is deviated from the lance central axis direction. This is because local wear is likely to occur due to collision with the side wall.

Note that _(the sum of the cross sectional area of each hole in the case of hole shape) cross-sectional area S ₁ of the opening 11, the cross-sectional area of the distal end of the central hole _{9 S 2 (= π × (} d4) 2/4) or more and It is desirable to do. If the cross-sectional area S ₁ <the cross-sectional area S ₂ , the flow rate of O ₂ gas flowing into the center hole 9 when the N ₂ gas is stopped during blowing is reduced, and the possibility that the metal is inserted into the center hole 9 is reduced. This is because it occurs.

On the other hand, the cross-sectional area S ₁ of the opening 11 is desirably 4 times or less the cross-sectional area S ₂ at the tip of the center hole 9. This is because, when the cross-sectional area S ₁ > 4 × the cross-sectional area S ₂ , the ratio of the dephosphorizing / refining agent powder discharged from the tip of the central tube 3 to the area other than the central hole 9 increases.

  FIG. 3A is a perspective view showing one aspect of the periphery of the opening 11 in a transparent state, and FIG. 3B is a cross-sectional view taken along the line AA in FIG. ) Is a perspective view showing another aspect of the periphery of the opening portion 11 in a see-through state, and FIG. 3D is a cross-sectional view taken along line AA in FIG. In the embodiment shown in FIGS. 3A and 3B, five rectangular windows each having the center of each opening 11 are arranged in the middle of the nozzle shaft core provided with five main holes 10 around it. Is the case.

  It is desirable to fix the pipe 3 so as not to move in order to make the central axes of the center pipe 3 and the center pipe 3 and the center hole 9 coincide with each other and to make the positional relationship between the pipes 3 and 4 unchanged. When the center tube 3 has a connection portion between the center tube 3 and the tip portion 7, as shown in FIGS. 3 (a) and 3 (b), the center tube 3 is formed at the tip portion by the connection portion. The positional relationship between the center hole 9 and the main hole 10 is fixed.

  However, in the case of a lance having a structure without such a connecting portion, as a method of fixing the central tube 3, as shown in FIGS. 3 (c) and 3 (d), for example, The method of fixing a side wall and the side wall of the piping 4 with the jig | tool 14 is illustrated.

  It is desirable that the inner diameter d1 of the center tube 3 and the entrance side diameter d2 of the center hole 9 satisfy the relationship of the expression (1).

d1 ≦ d2 (1)
This is because if the inner diameter d1 is smaller than the entry-side diameter d2, the rate at which the dephosphorizing refining agent powder discharged from the tip of the center tube 3 scatters other than the center hole 9 increases.

  The center hole 9 may have a straight shape (d2 ≧ d3 = d4) or a Laval shape (d2 ≧ d3 ≦ d4) in which the cross-section is enlarged toward the tip. The straight shape is a case where the length of d3 = d4 is 20 mm or more.

  Thus, in the lance 1, the first path 12 and the second path 13 communicate with each other inside the lance tip portion 2 by forming the opening 11.

Since the lance 1 has an opening 11 that communicates the first flow path 12 and the second flow path 13 inside the lance tip portion 2, the dephosphorizing refining powder is discharged from the first flow path 12. After that, most of it moves to the center hole 9 and is discharged from the tip of the lance. Therefore, remarkable wear of the lance main hole 10 due to the dephosphorizing refining agent powder is avoided. Further, when the N ₂ gas is stopped after the top spraying of the dephosphorizing refining agent powder is stopped, the O ₂ gas flowing through the second flow path 13 is discharged from the center hole 9 through the opening 11. For this reason, it is possible to avoid a bare metal insertion into the center hole 9 after stopping N ₂ .

In the lance 1, N ₂ gas and O ₂ gas are mixed on the inlet side of the center hole 9 when the dephosphorizing refining agent powder is blown up, and therefore, the N ₂ gas and O ₂ gas are mixed from the center hole 9. Dephosphorizing powder is discharged using gas as a carrier. However, if necessary, part or all of the lance tip portion 2 is made of copper or copper alloy which is difficult to burn, so that the combustion problem of piping does not occur.

Therefore, according to the lance 1, the amount of N ₂ gas can be reduced and the cost can be reduced, and the N ₂ gas can be stopped in the middle of the blowing, so N up in the molten steel can be avoided. 1 can be used.

DESCRIPTION OF SYMBOLS 1 Top blowing lance for refining 2 Lance front-end | tip parts 3-6 Pipe 7 Lance front-end | tip part 9 Center hole 10 Main hole 11 Opening part 12 1st flow path 13 2nd flow path

Claims (3)

A first path for supplying the dephosphorizing powder with the carrier gas;
A second path disposed around the first path for supplying oxygen gas;
A central hole disposed at the tip of the lance below the first path;
A plurality of main holes connected to the second path and disposed at the tip of the lance,
In a refining top blowing lance that sprays dephosphorizing refining agent powder and gas on the hot metal bath surface,
An upper blow lance for refining comprising an opening communicating the first path and the second path directly above the center hole. The cross-sectional area (S ₁ ) of the opening is relative to the cross-sectional area (S ₂ ) of the tip of the center hole.
The top blow lance for refining according to claim 1, wherein S ₂ ≦ S ₁ ≦ 4 × S ₂ . In the refining method of spraying the dephosphorizing refining agent powder and gas on the hot metal bath surface using the refining top blowing lance according to claim 1 or claim 2,
The gas carrying the dephosphorizing refining agent powder in the first path is any one or more of air, reducing gas, carbon dioxide gas, non-oxidizing gas or rare gas. A refining method characterized.

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