JP6044246B2 - Method and facility for refining molten metal - Google Patents

Description

  The present invention relates to a molten metal refining method for refining molten metal by blowing a refining gas to a molten metal accommodated in a refining vessel using an upper blowing lance in which a plurality of injection holes are formed on a tip surface, and Regarding the equipment.

  Necessary by inserting a top blowing lance into a converter (smelting vessel) containing molten metal, which is molten metal, and blowing up the refining gas from the injection hole formed at the tip of the top blowing lance. Accordingly, refining for the purpose of decarburization (hereinafter referred to as “converter blowing”) is performed by bottom blowing a refining gas into the converter. In the converter blowing, the need for dephosphorization reaction in the converter is reduced due to the development of the hot metal preliminary treatment, and the amount of generated slag in the converter has been rapidly reduced. As a result, it is difficult to form a slag layer on the hot metal contained in the converter, and in order to bring the oxygen gas used as a refining gas into contact with the hot metal, the pressure is high enough to penetrate the slag layer. It is no longer necessary to inject oxygen gas.

  By the way, although the slag layer has suppressed the scattering (henceforth "spitting") of hot metal which arises when the flow of the injected oxygen gas collides with hot metal, as mentioned above, it becomes difficult to form a slag layer. As a result, spitting is noticeably generated. By spitting, the converter opening, the top blowing lance, and even the exhaust gas equipment installed around the converter will have increased bullion, which will adversely affect the operation of the converter blowing. The generation of iron dust associated with spitting increases, and the yield of molten steel obtained by converter blowing is reduced.

  In recent years, in order to suppress this spitting, a plurality of injection holes are formed on the tip of the top blowing lance to reduce the refining gas velocity per injection hole and disperse the collision energy against the hot metal bath surface. Has been done. However, in the upper blow lance in which a plurality of injection holes are formed on the front end surface, if the number of injection holes becomes too large, a plurality of airflows of the refining gas from the injection holes may interfere with each other and merge. Sex occurs. It is known that the amount of spitting increases due to the coalescence of the airflow because the energy of the merged airflow increases.

  In order to prevent the occurrence of spitting due to the coalescence of this airflow, Patent Document 1 discloses that the overlap rate of the bath surface hot spot area geometrically calculated from the dimensions and operating conditions of the top blowing lance is below a certain threshold value. The top blowing lance is designed so that it has a small diameter nozzle that does not affect the cavity shape for the purpose of removing spitting at the center of the tip of the top blowing lance. Proposed. Further, in Patent Document 2, for the purpose of lowering the overlap ratio of the hot spot area and soft blow, the total area of the fire spot is set to 75% or more of the area of the circle surrounding the outermost periphery of the fire spot, An upper blowing lance characterized by having the following has been proposed.

JP-A-60-165313 JP 2002-285224 A

  The jet generated from the top blowing lance proposed in Patent Document 1 calculates the hot spot area on the assumption that the acid feed jet goes straight when calculating the overlap ratio of the hot spots. Accordingly, since the calculated overlap ratio of the hot spot area is estimated to be smaller than the actual one, the overlap ratio is actually reduced even in the upper blow lance designed to be safer, that is, on the safe side. There is a problem that it becomes higher than expected and it is difficult to suppress spitting.

  In the top blowing lance proposed in Patent Document 2, the throat diameter and nozzle outlet diameter of the peripheral hole (peripheral injection hole) and the central hole (central injection hole) are variable, but the total area of the fire point is the fire point. By setting it to 75% or more of the area of the circle surrounding the outermost periphery, the diameter of the central hole is inevitably equal to or larger than the diameter of the peripheral hole. There is a problem in that spitting is increased by approaching and interfering with each other and eventually coalescing.

  The present invention has been made in view of the above problems, and an object of the present invention is to install an upper blowing lance on the upper side of a smelting vessel containing molten metal, and to provide a plurality of pieces provided on the front end surface of the upper blowing lance. When the refining gas is blown from the injection holes to the molten metal bath surface and the refining process of the molten metal is performed, spitting is suppressed by more reliably suppressing the coalescence of the air flow injected from each injection hole. It is to provide a technology related to the refining process that can be suppressed.

  As a result of intensive studies in order to solve the above problems, the present inventors have determined that the airflow from the central injection hole formed in the front end surface and the concentric circle on the front end surface centered on the central axis of the central injection hole. The phenomenon in which the airflows from the plurality of peripheral injection holes formed on the circumference of each other interfere with each other and merge is the distance between the airflows, that is, the peripheral edge of the central injection hole and the peripheral edges of the plurality of peripheral injection holes It has been found that the shorter the distance h, the stronger the shortest distance h, the less the interference and coalescence of the airflows, and the more the spitting can be suppressed.

  Furthermore, the present inventors, when the lance height H from the bath surface of the molten metal at rest to the tip surface of the top blowing lance is too large, the airflow length until it collides with the molten metal increases. It has been found that interference and coalescence of airflows are likely to proceed, and that multiple airflows are more likely to collide with the molten metal after complete coalescence, leading to further spitting, while the lance height It has been found that when H is small, spitting can be reduced because the air current collides with the molten metal before the air current groups merge.

  In consideration of the above, the present inventors pay attention to the relationship between the lance height H and the shortest distance h, and increase the ratio of the shortest distance h to the lance height H to be larger than a predetermined value. Thus, it was speculated that the occurrence of spitting caused by mutual interference or coalescence between the airflow from the central injection hole and the airflow from the surrounding injection holes could be suppressed, and the present invention was completed.

The gist of the present invention for solving the above problems is as follows.
[1] A central injection hole is provided on the front end surface, a plurality of peripheral injection holes are arranged on a circumference of a concentric circle on the front end surface around the central axis of the central injection hole, and the peripheral injection hole An upper blowing lance whose central axis is inclined with respect to the central axis of the central injection hole is on a molten metal bath surface accommodated in a refining vessel so as to satisfy the following formula (1): A molten metal refining method comprising: refining the molten metal by blowing a refining gas onto the bath surface from the central injection hole and the peripheral injection hole.
ε = h / H> 0.025 (1)
Here, h: the shortest distance [m] between the peripheral edge of the central injection hole and the peripheral edges of the plurality of peripheral injection holes,
H: Lance height [m] which is the distance from the bath surface of the molten metal when stationary to the tip surface when the top blowing lance is installed.
[2] The molten metal according to [1], wherein the nozzle inclination angle α formed by the central axis of the peripheral injection hole intersecting with the central axis of the upper blowing lance is 10 to 30 °. Refining method.
[3] A refining vessel for containing molten metal, a central injection hole at the tip surface, and a plurality of peripheral injection holes on a circumference of a concentric circle on the tip surface with the central axis of the center injection hole as a center An upper blowing lance that is disposed and the central axis of the peripheral injection hole is inclined with respect to the central axis of the central injection hole, and the upper blowing lance satisfies the above formula (1) The molten metal refining equipment is installed on the bath surface of the molten metal contained in the refining vessel.
[4] The molten metal as described in [3] above, wherein the nozzle inclination angle α formed so that the central axis of the peripheral injection hole intersects the central axis of the upper blowing lance is 10 to 30 °. Refining equipment.

  By the molten metal refining method and its equipment according to the present invention, the air flow from the central injection hole formed on the front end surface of the upper blowing lance and the air flow from the surrounding injection holes interfere with each other, and thus merge. Since it can suppress, spitting resulting from the interference or coalescence of those airflows can be suppressed, achieving soft blow by porosity.

It is a schematic sectional drawing of the refining equipment which refines the molten metal of the present invention. It is a schematic explanatory drawing which shows the relationship between an upper blowing lance and the stationary bath surface of the molten metal accommodated in a refining container. It is a bottom view of the upper blowing lance which shows the front end surface seen from the lower side. It is a schematic diagram which shows the locus | trajectory of the airflow injected from an upper blowing lance. It is a graph which shows the relationship between airflow straightness degree (gamma) and ratio (epsilon) (= h / H).

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of a refining facility for refining molten metal according to the present invention. The refining facility 1 includes an upper blowing lance 2 and a refining vessel 4 that accommodates a molten metal 3. The top blowing lance 2 has a tubular lance body 5 and a lance tip 6 connected to the tip of the lance body 5 by welding or the like. The lance body 5 is not particularly limited to a circular tube, and the horizontal cross section of the lance body 5 may be elliptical. As shown in FIG. 1, a refining gas 7 is supplied to the upper blowing lance 2. A plurality of injection holes are formed in the tip surface 8 of the lance tip 6 facing the bath surface 9 of the molten metal 3, and the refining gas 7 passing through the inside of the upper blowing lance 2 is supplied to the plurality of injection holes. To the bath surface 9.

  FIG. 2 is a schematic explanatory view showing the relationship between the top blowing lance 2 and the stationary bath surface of the molten metal 3 accommodated in the refining vessel 4. In FIG. 2, the upper blowing lance 2 is shown in cross section. The lance body 5 has a multi-pipe structure, a structure having at least a triple pipe, and a refining gas passage 11 through which a refining gas 7 (see FIG. 1) passes is formed. A water supply passage 12 and a drain passage 13 through which cooling water for cooling the upper blowing lance 2 passes are formed so as to surround the gas flow passage 11 for refining. The lance tip 6 communicates with the refining gas channel 11 and the communication portion 14 that communicates with the water supply channel 12 and the drain channel 13 when the lance tip 6 is connected to the tip of the lance body 5. And a plurality of nozzles that form injection holes for injecting the gas for refining. The tip portion of the lance tip 6 on which the plurality of nozzles are formed has a shape in which the truncated cone is inverted, and the surface portion of the truncated cone facing the bath surface 9 is the tip of the lance tip 6. It becomes surface 8. The tip surface 8 has a central surface 24 that is an upper bottom surface of the truncated cone that becomes a horizontal plane, and a truncated cone surface 25 that becomes an inclined surface.

  As shown in FIG. 2, the straight lance body 5 (upper blow lance 2) is orthogonal to the bath surface 9 of the molten metal 3 accommodated in the refining vessel 4 when stationary, that is, in the vertical direction. Then, the top blowing lance 2 is inserted into the upper part of the refining vessel 4 from above. The top blowing lance 2 has a central injection hole 21 in the tip surface 8 and is inserted into the refining vessel 4 at a central position 23 of the tip surface 8 when the tip surface 8 is viewed from the lower horizontal plane. Is formed with one central injection hole 21 penetrating the lance tip 6. The central injection hole 21 communicates with the refining gas flow path 11 in the lance body 5, and the refining gas 7 is injected from the central injection hole 21. The center position 23 may be included in the central surface 24 and the central injection hole 21 may be formed in the central surface 24.

  A conical surface 25 that is inclined with respect to the central surface 24 is formed on the distal end surface 8 from the outside of the lance body 5 toward the central surface 24. Therefore, the normal direction of the conical surface 25 is vertical. It is directed outward from the central axis of the lance body 5 with respect to the direction. The peripheral injection hole 22 is formed in a conical surface 25 that is a part of the tip surface 8 so that its central axis (the direction of the air flow of the refining gas 7) is inclined with respect to the central axis of the lance body 5. Yes. For this reason, since the airflow of the refining gas 7 injected from the surrounding injection holes 22 goes to the outside of the airflow of the refining gas 7 injected from the central injection holes 21, the refining gas 7 from the central injection holes 21 Less susceptible to airflow. The nozzle inclination angle α (see FIG. 4) formed so that the central axis of the peripheral injection hole 22 intersects the central axis of the upper blowing lance 2 (lance main body 5) is preferably 10 to 30 °. If the nozzle inclination angle α is smaller than 10 °, the airflow from the peripheral injection holes 22 and the airflow from the central injection hole 21 are more likely to interfere with each other. If the nozzle inclination angle α is larger than 30 °, the airflow from the peripheral injection holes 22 The airflow may collide with the side wall of the refining vessel 4 and the refractory forming the refining vessel 4 may be worn out.

  A refining gas supply pipe (not shown) is connected to the refining gas flow path 11 of the top blowing lance 2 so that the refining gas 7 (see FIG. 1) flows through the refining gas supply pipe. Is supplied to the path 11. The refining gas 7 is sent from the refining gas flow channel 11 to the central injection hole 21 and the plurality of surrounding injection holes 22, and the refining gas 7 is injected to the bath surface 9. Generate airflow. In the present embodiment, oxygen gas is used as the refining gas 7, but is not limited to oxygen gas as long as it is a gas that can be used for refining the molten metal 3.

  The refining vessel 4 shown in FIG. 1 is provided with a hot water outlet (not shown). Oxygen gas, which is a refining gas 7, is blown from the top blowing lance 2 onto the bath surface 9 of the molten metal 3. And the oxidation of the substance contained in it, for example, carbon, is accelerated | stimulated and the refining process of the molten metal 3 is performed. When a predetermined time elapses after the refining gas 7 starts to be blown onto the molten metal 3, or when the concentration of the substance contained in the molten metal 3, for example, the carbon concentration reaches a predetermined value, the refining vessel 4 is tilted. Then, the molten metal 3 is poured out from the outlet and the refining process of the molten metal 3 is finished.

  FIG. 3 is a bottom view of the upper blowing lance showing the distal end surface 8 as viewed from below. FIG. 3 can also be said to show the front end surface 8 projected in the vertical direction on a horizontal plane virtually formed below the front end surface 8. As shown in FIG. 3, when viewing the upper blowing lance 2 (tip surface 8) from the horizontal plane, the peripheral injection holes 22 are formed on the circumference of a concentric circle on the tip surface 8 with the central axis of the central injection hole 21 as the center. A plurality of are formed. In FIG. 3, the circumference is indicated by a dotted line. When the central surface 24 of the distal end surface 8 is viewed from a horizontal plane, the central injection hole 21 is substantially circular. When the conical surface 25 is viewed from the lower surface parallel to the conical surface 25, the peripheral injection hole 22 is also substantially circular, but the peripheral axis is inclined with respect to the central axis of the central injection hole 21. Since the injection hole 22 is formed in the conical surface 25, the shape of the surrounding injection hole 22 when the surrounding injection hole 22 is seen from a horizontal plane is an ellipse. The center of the ellipse of the plurality of peripheral injection holes 22 is arranged on the circumference of the dotted line. In the present embodiment, both the central injection hole 21 and the peripheral injection holes 22 are circular when viewed from a plane parallel to the plane on which the respective injection holes are formed, but the shape is not particularly limited to a circular shape, and is elliptical. It may be a shape.

The shortest distance h between the peripheral edge of the central injection hole 21 and the peripheral injection hole 22 and the lance height H from the bath surface 9 to the tip surface 8 of the upper blowing lance 2 as viewed from the horizontal plane is expressed by the following formula ( When the tip surface 8 of the top blowing lance 2 is designed so as to satisfy 1) and the lance height H [mm] is adjusted, the airflow from the central injection hole 21 and the airflow from the surrounding injection holes 22 Can be prevented from interfering with each other. This suppresses spitting while realizing soft blow.
ε = h / H> 0.025 (1)
The shortest distance h [mm] is the shortest distance between the peripheral edge of the central injection hole 21 projected onto the horizontal plane in the vertical direction and the peripheral edges of the plurality of peripheral injection holes 22 similarly projected onto the horizontal plane in the vertical direction. It can be said. In the equation (1), ε is the ratio of the shortest distance h to the lance height H [mm].

When viewed from a horizontal plane, the diameter p [mm] of a circle in which a plurality of peripheral injection holes 22 are arranged around the central injection hole 21 and the short diameter ds [mm] of the elliptical peripheral injection holes 22. And the diameter dc [mm] of the circular central injection hole 21, the shortest distance h can be calculated by the following equation (2).
h = 1/2 * (p-ds-dc) (2)
The shortest distance h may be calculated by the equation (2), and the size and position of the central injection hole 21 and the peripheral injection hole 22 on the distal end surface 8 may be determined.

  The inventors of the present invention have the effect that the shortest distance h and the lance height H affect the phenomenon of interference and / or coalescence of airflows injected from the injection holes. For example, when the shortest distance h is reduced, a plurality of airflows from the respective injection holes are easily merged, but when the lance height H is reduced, the plurality of airflows are difficult to merge. Therefore, it was derived that the ratio ε between the shortest distance h and the lance height H should be larger than a certain threshold value. Specifically, as a result of repeated investigations by numerical fluid analysis, the present inventors have found that if the ratio ε> 0.025, there is interference between the airflow from the central injection hole 21 and the airflow from the surrounding injection holes 22. It was alleviated and led to reduced spitting.

  If the number of the peripheral injection holes 22 is too large, interference and coalescence between adjacent peripheral injection holes 22 are promoted. If the number is too small, the effect of dispersing the collision energy on the bath surface 9 is reduced. The number is preferably 3 or more and 5 or less. If the lance height H is too small, the dynamic pressure per airflow increases and the effect of dispersing the collision energy is reduced. Therefore, the lance height H is desirably 1600 mm or more.

When it becomes necessary to increase the supply amount of the refining gas 7 to the maximum value at the beginning or end of the operation, etc., so that refining can be performed under appropriate expansion conditions suitable for each purpose, The peripheral injection hole nozzle that forms the peripheral injection hole 22 is preferably a Laval nozzle having a throat at the inlet. Further, it is not necessary to increase the flow rate (m ³ / sec) of the refining gas 7 from the central injection hole 21 from the viewpoint of interference between the airflow from the central injection hole 21 and the airflow from the peripheral injection hole 22. Therefore, it is effective to reduce the dynamic pressure by generating improper expansion, and it is preferable that the central injection nozzle forming the central injection hole 21 is a straight nozzle.

  In the upper blowing lance 2 of the above embodiment, the tip portion has a shape in which the truncated cone is inverted, but the present invention is not limited to this shape. For example, the tip portion has a rectangular parallelepiped shape, It may be horizontal or flat. Even if the entire front end surface 8 is horizontal or flat, the front end surface 8 is viewed from the horizontal plane below, and the plurality of peripheral injection holes 22 are on the front end surface 8 with the central axis of the central injection hole 21 as the center. If the upper blow lance 2 is arranged on the circumference of a concentric circle and the central axis of the peripheral injection hole 22 is inclined with respect to the central axis of the central injection hole 21, the air flow from the central injection hole 21 and Interference with the airflow from the surrounding injection holes 22 and coalescence can be mitigated.

Further, on the numerical analysis software, a simulation for injecting the refining gas 7 from the central injection hole 21 and the peripheral injection holes 22 while changing the design conditions such as the size and position of each injection hole and the flow rate is performed. It is determined as follows whether the airflow from 21 and the airflow from the surrounding injection holes 22 interfere with each other and merge.
FIG. 4 is a schematic diagram showing the trajectory of the air flow of the refining gas 7 injected from the top blowing lance 2, particularly from the surrounding injection holes 22. As shown in FIG. 4, a horizontal plane including the tip position on the central axis of the peripheral injection hole 22 is defined as an X plane, and a vertical plane including the central axis of the central injection hole 21 and orthogonal to the X plane is defined as a Z plane. A perpendicular line is drawn from the tip position on the central axis of the peripheral injection hole 22 toward the Z plane, and a point on the Z plane where the perpendicular intersects is defined as an origin O, and the X plane and the Z plane are indicated by alternate long and short dash lines. . In addition, a peripheral injection hole extended center line 32 that is virtually formed by extending the central axis of the peripheral injection hole 22 is indicated by a two-dot chain line, and an air flow injected along the central axis of the peripheral injection hole 22 is shown. The track line 33 is indicated by a dotted line.
(1) As shown in FIG. 4, a horizontal plane 30 is assumed that is “0.8 × lance height H” below the tip on the central axis of the peripheral injection hole 22. In FIG. 4, the horizontal plane 30 is indicated by a thin line.
(2) The distance X _linear from the central injection hole extension center line 31 virtually formed by extending the central axis of the central injection hole 21 to the intersection of the peripheral injection hole extension center line 32 and the horizontal plane 30 is calculated. To do.
(3) A distance X _jet from the surrounding injection hole 22 to the intersection of the trajectory line 33 and the horizontal plane 30 is calculated.
(4) The ratio of X _{jet to} X _linear , that is, X _jet / X _linear is calculated as the straight airflow degree γ.

  If the airflow straightness γ is 0.8 or more, the airflow from the central injection hole 21 and the airflow from the peripheral injection hole 22 do not interfere with each other, or if the airflow from the central injection hole 21 and the surrounding Even if the airflows from the injection holes 22 interfere with each other, it can be determined that the airflows are not merged, and the airflows are not merged with each other. It can be assumed that soft-blowing has been realized.

  As described above, the tip surface 8 of the top blowing lance 2 according to the planned lance height H, with the ratio ε = h / H of the lance height H to the shortest distance h being larger than 0.025 as an index. By installing the top blowing lance 2 by adjusting the lance height H so as to satisfy the planned lance height H, the air flow from the central injection hole 21 and the surrounding injection holes 22 Interference with airflow and coalescence can be mitigated, and spitting can be suppressed.

  Using the refining equipment shown in FIG. 1, simulation of refining treatment of molten iron (molten metal) was performed a plurality of times. ANSYS FULLENT was used for the simulation and the numerical fluid analysis.

  As shown in FIG. 2, the structure of the front end surface 8 of the upper blowing lance 2 is a cone in which the central surface 24 in which the central injection hole 21 is formed is horizontal and four or five peripheral injection holes 22 are formed. Surface 25 was set. The angle of the conical surface 25 with respect to the horizontal plane of the central surface 24 was 14 ° for four peripheral injection holes 22 and 13 ° for five peripheral injection holes 22. The nozzle inclination angle α of the peripheral injection holes 22 was 14 ° when four peripheral injection holes 22 were provided, and 13 ° when five peripheral injection holes 22 were provided.

  The design items of the top blow lance 2, particularly the tip surface 8, in each of the simulations were changed as follows.

  The central injection hole 21 and the peripheral injection hole 22 are both straight nozzles, the shape of the central injection hole 21 viewed from the horizontal plane below the central surface 24 is a circle, and the diameter dc is 20 to 4 for the four peripheral injection holes 22. When the number of peripheral injection holes 22 is 5 mm, the shape of the peripheral injection holes 22 is 20 to 80 mm, and the shape of the peripheral injection holes 22 viewed from a plane parallel to the conical surface 25 is a circle. The short diameter ds of the ellipse is 81 to 98 mm when four peripheral injection holes 22 are provided, and 71 to 80 mm when five peripheral injection holes 22 are provided. In addition, when the number of the peripheral injection holes 22 is four, the diameter p of the circumference around the central injection hole 21 is 291 mm, and the number of the peripheral injection holes 22 is five. It was 244 mm.

In the simulation, oxygen gas was used as the refining gas 7. In each simulation, the oxygen gas flow rate supplied to the refining gas channel of the top-blown lance 2, 65000Nm ³ / time, 50,000 nm ³ / time, and is changed to three stages 40000Nm ³ / time, the lance height It changed into three steps, 1600mm, 2000mm, 2500mm. In a plurality of simulations, the straight airflow rate γ and the ratio ε (= h / H) are acquired.

  The inventors have intensively studied the relationship between the amount of spitting and the degree of straight airflow γ. As a result, it has been found that there is a correlation between the amount of spitting, the straightness γ of the airflow, and the shape of the depression of the bath surface 9 obtained by the collision of the airflow. Specifically, it has been found that the amount of spitting decreases as the straight airflow rate γ increases. That is, as the straight air travel γ decreases due to the collision of the air current, the ratio L / D between the depth L of the recess formed on the bath surface 9 of the molten metal 3 and the width D of the recess decreases, and the amount of spitting Tend to increase. On the other hand, as the air flow straightness γ increases, the ratio L / D between the depth L of the recess formed on the bath surface 9 and the width D of the recess increases, and the amount of spitting tends to decrease. The present inventors presume that the relationship between the straight air flow rate γ and the shape ratio L / D of the depression of the bath surface 9 is related to the presence or absence of coalescence of the air flow described above. Further, it has been empirically understood that, when the airflow straightness γ is 0.8 or more, coalescence of airflows is eliminated as described above, and spitting can be suppressed by a considerable amount. From the above, in this embodiment, the study is made with the airflow straightness γ instead of the spitting amount.

  FIG. 5 is a graph showing the relationship between the straight airflow rate γ and the ratio ε (= h / H) obtained in each simulation. As can be seen from the graph of FIG. 5, when the ratio ε (= h / H) exceeds 0.025, the airflow straightness γ is 0.8 or more. When the airflow straightness γ is 0.8 or more, the airflow from the peripheral injection hole 22 and the central injection hole 21 is prevented from interfering with each other. It was found that the airflow from 21 was prevented from coalescing.

  As described above, the central injection hole 21 and the peripheral injection hole 22 are designed on the tip surface 8 of the upper blowing lance 2 so that the ratio ε exceeds 0.025, and the position of the upper blowing lance 2 (lance If the height H) is adjusted, it is possible to suppress the air currents from the peripheral injection hole 22 and the central injection hole 21 from interfering with each other and coalescing, and spitting can be suppressed.

DESCRIPTION OF SYMBOLS 1 Refining equipment 2 Top blowing lance 3 Molten metal 4 Smelting container 5 Lance main body 6 Lance chip 7 Refining gas 8 Tip surface 9 Bath surface 11 Refining gas flow path 12 Water supply flow path 13 Drain flow path 14 Drainage path 14 Communication part 21 Central injection hole 22 Peripheral injection hole 23 Center position 24 Central surface 25 Conical surface 30 Horizontal surface 31 Central injection hole extension center line 32 Peripheral injection hole extension center line 33 Track line

Claims (4)

A central injection hole is provided at the distal end surface, a plurality of peripheral injection holes are arranged on a circumference of a concentric circle on the distal end surface with the central axis of the central injection hole as a center, and the central axis of the peripheral injection hole However, an upper blowing lance inclined with respect to the central axis of the central injection hole is installed on a molten metal bath surface accommodated in a refining vessel so as to satisfy the following formula (1). ,
Refining the molten metal by blowing a refining gas onto the bath surface from the central injection hole and the peripheral injection hole with a straight air flow rate γ of the refining gas injected from the peripheral injection hole of 0.8 or more. A method for refining molten metal, characterized by:
ε = h / H> 0.025 (1)
Here, h: the shortest distance between the periphery of said central injection hole projected into a horizontal plane, and the peripheral edge of said plurality of peripheral injection holes projected into a horizontal plane [m],
H: Lance height [m] which is a distance from the bath surface of the molten metal when stationary to the tip surface when the top blowing lance is installed,
It is.   2. The molten metal refining method according to claim 1, wherein a nozzle inclination angle α formed so that a central axis of the peripheral injection hole intersects with a central axis of the upper blowing lance is 10 to 30 °. A refining vessel containing molten metal;
A central injection hole is provided at the distal end surface, a plurality of peripheral injection holes are arranged on a circumference of a concentric circle on the distal end surface with the central axis of the central injection hole as a center, and the central axis of the peripheral injection hole An upper blowing lance inclined with respect to the central axis of the central injection hole,
The upper blowing lance is installed on the molten metal bath surface accommodated in the refining vessel so as to satisfy the following formula (1), and the straightness of the air flow of the refining gas injected from the surrounding injection holes A molten metal refining facility characterized in that γ is 0.8 or more .
ε = h / H> 0.025 (1)
Here, h: the shortest distance between the periphery of said central injection hole projected into a horizontal plane, and the peripheral edge of said plurality of peripheral injection holes projected into a horizontal plane [m],
H: Lance height [m] which is a distance from the bath surface of the molten metal when stationary to the tip surface when the top blowing lance is installed,
It is.   4. The molten metal refining equipment according to claim 3, wherein a nozzle inclination angle α formed so that a central axis of the peripheral injection hole intersects with a central axis of the upper blowing lance is 10 to 30 °.

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