JP2018131675A - Decarbonization blowing lance tip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a corrosion flow velocity to a molten metal surface while blowing without reducing an Oflow rate and changing a lance height.SOLUTION: A decarbonization blowing lance tip 1 is attached to a tip of a decarbonization blowing lance 4 used when performing the decarbonization treatment of molten iron in a converter vessel, and has a plurality of nozzles 7 for jetting oxygen to the molten iron. These plural nozzles 7 have throat parts 9 having smaller diameters than these of outlets 8 in a hole. Each of sectional shapes formed in the plural nozzles 7 in the throat parts 9 and the outlets 8 is an equal shape and noncircular. The throat parts 9 and the outlets 8 of the plural nozzles 7 are arranged in a mutually rotational symmetry state about an axis so as to be arrayed in a concentric circle taking an axis of the decarbonization blowing lance 4 as a reference, and so as to depart each other at an equal angle around the axis. The aspect ratios and the hole occupying angels of the plural nozzles 7 satisfy a predetermined condition.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a decarburizing blown lance tip used for decarburization blowing in a converter, and more particularly to a decarburized blown lance tip with less spitting.

In the blast furnace-converter method, which accounts for approximately 70% of Japan's crude steel production, the hot metal discharged from the blast furnace is charged into a batch-type converter vessel and sprayed with oxygen jet from above or from the converter tuyere. Conversion to steel by decarburization ([C] + 1 / 2O ₂ = CO) by oxygen blowing is generally performed.
In conventional converters, desiliconization / dephosphorization was performed at the same time as decarburization, but in recent years, before decarburization processing in the converter, in order to respond to cost reduction and stricter quality requirements. In many cases, converters specialize in decarburization by performing pre-dephosphorization treatment (simultaneous de-Si treatment is also performed).

Although the amount of slag generated in the converter has been significantly lower than before due to the advance dephosphorization treatment, this time the problem of dust loss due to spitting has become more prominent (if there is a lot of slag, it becomes a cover). This has the effect of reducing dust generation).
In order to prevent dust loss, it is necessary to reduce the collision flow velocity (collision pressure) of oxygen introduced from above onto the hot metal bath surface. (1) Reduce the O ₂ flow rate, (2) Lance height Generally, a method such as increasing the distance from the lance to the hot water surface is adopted.

However, if the O ₂ flow rate is reduced as shown in (1), the processing time becomes longer, which is not desirable from the viewpoint of productivity. Also, as shown in (2), when the lance height is increased and the distance from the molten metal surface to the lance is increased, secondary combustion (CO + 1 / 2O ₂ = CO ₂ ) increases, resulting in a refractory in the furnace. Adversely affect. Therefore, it is desirable to adopt a means for solving the problem of dust loss due to spitting without reducing the O ₂ flow rate and without increasing the lance height. As such spitting suppression means, techniques as shown in Patent Documents 1 and 2 below have been developed.

For example, Patent Document 1 has a wide range of adjustment of the acid feed rate, the acid feed rate can be freely changed according to the conditions in the furnace, iron scattering and dust generation at the high acid feed rate are reduced, and the final stage of blowing Discloses an upper blowing lance for converter blowing that suppresses iron oxidation at a low acid feed rate and improves the stabilization of the reaction.
The top blowing lance for converter blowing of Patent Document 1 has a Laval nozzle installed at the tip of the lance, and the Laval nozzle has a throat diameter Dt (mm) and a nozzle back pressure P (kPa) of 392 to 588. Within the range of (kPa), a predetermined relationship is established among the nozzle back pressure P (kPa), the converter capacity W (t), and the number of installed Laval nozzles n, and the outlet diameter De and the throat diameter Dt of the Laval nozzle The ratio (De / Dt) satisfies the predetermined relationship.

  Patent Document 2 discloses a converter top blowing lance for reducing dust generation in top bottom blowing converter refining. The converter top blowing lance of Patent Document 2 is a converter top blowing lance in an upper bottom blowing converter type refining furnace in which a steel bath is stirred by gas, and is a concentric 3 to 16-sided polygon or concentric cross section. 2 to 10 shielding plates are arranged on a part of the opening surface of the slit-shaped oxygen supply pipe having a slit, and the lance body and the lance tip including the lance center point are fixed to each other through the shielding plate. A converter top blowing lance is disclosed. This converter top blowing lance has a ratio B / h of the long side length B (mm) to the short side length h (mm) of each tip opening surface separated by a shielding plate, 10 to 225, and the lance diameter. When (B x h) / R is 0.4 to 4 in the case of R (mm), the angle ω formed by the point on the circumference closest to each other and the center point of the lance on the opening surface of the adjacent two holes is 10-60 degrees.

JP 2003-105425 A JP-A-8-157828

  By the way, in the top blowing lance for converter blowing of patent document 1, the arrangement | positioning condition of a nozzle exit is not described at all. Therefore, depending on the arrangement state of the Laval nozzle, the jets ejected from the nozzles may be curved, the jets of the curved jets may overlap, and the jets may be hard blown by the joining of the jets, causing spitting. That is, the technique of Patent Document 1 is insufficient as a guideline for suppressing spitting.

Further, Patent Document 2 does not describe any relationship between the throat opening shape and the nozzle outlet opening shape which greatly affects the jet flow velocity, and even the top blowing lance for converter blowing in Patent Document 2 is spitting. It is not enough as a guideline to suppress dust reduction due to
The present invention has been made in view of the above-described problems, and can reduce the collision flow velocity to the molten metal surface during blowing without reducing the O ₂ flow rate and without changing the lance height. An object of the present invention is to provide a decarburizing blown lance tip capable of reducing spitting generated during blowing.

In order to solve the above problems, the decarburizing blown lance tip of the present invention employs the following technical means.
That is, the decarburizing blown lance tip of the present invention is a decarburized blown lance tip attached to the tip of a decarburized blown lance used when performing decarburization treatment of hot metal in a converter vessel. The nozzle has a plurality of nozzles for ejecting oxygen to the molten iron, each of the plurality of nozzles has a throat structure having a throat portion narrowed in a diameter smaller than the outlet in the hole, Each of the cross-sectional shapes formed on the plurality of nozzles is equal and non-circular, and each of the cross-sectional shapes formed on the plurality of nozzles at the outlet is equal and non-circular, The throats and outlets of a plurality of nozzles rotate with respect to the axis so that they are arranged concentrically with respect to the axis of the decarburizing blow lance and at an equal angle around the axis. Symmetry Are arranged in a state, wherein the plurality of nozzles to satisfy the following condition.
(Condition 1)
“When the cross-sectional shape of the throat portion is converted into an ellipse, the aspect ratio of the cross-sectional shape converted into an ellipse is 2.4 to 5.5”
(Condition 2)
“When the bottom surface of the decarburizing blown lance tip is viewed in the circumferential direction 360 ° around the axis of the decarburizing blown lance, the total hole occupation angle is the angle range in which the nozzles are present. 330 ° or less. ''
Preferably, the outlet of the nozzle is formed with a restraining portion that restrains the flow of the jet flow ejected from the nozzle, and the restraining portion is axially centered from an opening edge on the axial center side at the outlet of the nozzle. Is formed so as to protrude with a protrusion width of 1/4 or more of the opening width in the direction away from the nozzle, and is determined from the flow rate of oxygen ejected from the nozzle, the cross-sectional area of the throat portion, and the cross-sectional area of the outlet The degree of inappropriateness is preferably 0.6 to 0.9.

According to the decarburizing blown lance tip of the present invention, the collision flow velocity to the molten metal surface during blowing can be reduced without reducing the O ₂ flow rate and without changing the lance height. It becomes possible to reduce spitting generated during smelting.

It is the figure which showed the converter equipment provided with the blown lance tip for decarburization of this embodiment. It is the figure which showed the arrangement | positioning state of the nozzle in the front end surface of the blown lance tip for decarburization of this embodiment. It is the figure which showed the calculation method of the aspect-ratio of a nozzle. It is sectional drawing of the nozzle used when demonstrating the calculation method of an improper degree. It is a figure of the front end surface of a nozzle used when explaining the calculation method of a hole occupation angle. It is the figure which showed the base-shaped lance tip front end surface which has six holes by which the cross-sectional shape was made into the perfect circle shape. It is the figure which showed the cross-sectional structure of the nozzle provided in the blowing lance tip for decarburization of this embodiment. It is the figure which showed the installation position of the throat part in the nozzle provided in the blowing lance tip for decarburization of this embodiment. It is the figure which showed the nozzle whose cross-sectional shape formed by carrying out hole coupling | bonding of the nozzle of a base shape is an unequal circle.

[First Embodiment]
Hereinafter, embodiments of the decarburizing blown lance tip 1 of the present invention will be described in detail with reference to the drawings.
FIG. 1 schematically shows a converter facility 2 provided with a decarburizing blown lance tip 1 of the present embodiment.

  As shown in FIG. 1, the converter equipment 2 of 1st Embodiment is a dephosphorization process in the top bottom blowing converter container (converter 3) beforehand charged with cold iron sources, such as a scrap and a cold metal. Then, the hot metal after dephosphorization was poured into the hot metal, and then auxiliary materials such as lime were added to the hot metal, and the decarburization blow lance 4 was inserted from the furnace port of the converter 3, and the gas was discharged from the nozzle 7 at the tip. Oxygen is blown to the hot metal, and simultaneously, decarburization refining (blowing) is performed while blowing a gas such as nitrogen or argon from a tuyere 5 provided at the bottom of the furnace and stirring the hot metal.

As shown in an enlarged view in FIG. 1, the decarburizing blow lance 4 is a long tubular member extending in the vertical direction, and is a cooling system that circulates an oxygen channel 6 that penetrates the inside in the longitudinal direction and cooling water. A flow path (not shown) is provided. The decarburizing blown lance tip 1 of the present invention is attached to the tip of the decarburizing blown lance 4, in other words, the end of the oxygen flow path 6.
The decarburizing blown lance tip 1 described above is provided with a plurality of nozzles 7 for guiding oxygen in the oxygen flow path 6 to the outside (water surface) of the lance and ejecting the introduced oxygen to the molten metal. It has a structure capable of cooling the chip itself by introducing cooling water in the flow path (not shown). The plurality of nozzles 7 each have a throat structure 9 having a throat portion 9 that is narrower in diameter than the outlet 8 of each nozzle 7 (the inside of the hole is once narrowed from the inlet of the nozzle 7 toward the outlet 8). It has a structure that will spread again later). The cross-sectional shape at the throat portion 9 is non-circular in all of the plurality of nozzles 7 and is the same shape as each other, and the cross-sectional shape at the outlet 8 is the same non-circular shape in any of the plurality of nozzles 7. Has been. The throat portions 9 and the outlets 8 of the plurality of nozzles 7 are based on the axis of the decarburization blown lance 4 when the front end surface of the decarburization blown lance tip 1 is viewed from below (front). The nozzles 7 are arranged so that the centers of the nozzles 7 are located on concentric circles, and are arranged at equal angles around the axis of the decarburizing blow lance 4. The arrangement of the plurality of nozzles 7 is such that when the bottom surface of the decarburizing blow lance 4 is rotated around the axis of the decarburizing blow lance 4, the nozzles 7 overlap each other at a predetermined rotation angle. Therefore, it can also be said that the plurality of nozzles 7 are rotationally symmetric with respect to the axial center of the decarburizing blow lance 4.

For example, in the case of the decarburization blown lance tip 1 illustrated in FIG. 2, the nozzles 7 are provided at three positions with an angle of 120 ° around the axis of the decarburization blown lance 4. The nozzles 7 are rotationally symmetric with respect to the axis of the decarburizing blow lance 4 (three-fold symmetry).
In other words, the plurality of nozzles 7 are arranged so as to be equidistant from the axis of the decarburizing blown lance tip 1 (lance). Moreover, when the nozzle 7 is seen from the axial center of the decarburization blowing lance tip 1, it can also be said that each nozzle 7 is arranged at an equal angle to each other in the circumferential direction.

  Here, “rotation symmetry” means that when the nozzle 7 is rotated by a predetermined rotation angle with respect to the axis of the decarburizing blow lance 4, the nozzle 7 rotated to the nozzle 7 located adjacent to the nozzle 7 is rotated. Say the case of complete overlap. In addition, if expressed without using “rotation symmetry”, the plurality of nozzles 7 are arranged so that the nozzles 7 are line-symmetric with respect to any line passing through the axis of the decarburizing blow lance 4. It may be said that it has been.

  In addition, each nozzle 7 has a non-circular cross section perpendicular to the axis of the decarburizing blow lance 4, and each nozzle 7 has the same cross sectional shape (the same shape). Have been). The non-circular shape means a shape other than a perfect circle (a shape in which the aspect ratio does not become 1) among shapes formed in an endless shape (closed figure shape) by combining straight lines or curves. Such non-circular shapes include not only elliptical shapes, rice ball shapes, and polygonal shapes, but also distorted shapes such as egg shapes and array shapes.

  Further, each of the nozzles 7 is provided with a throat portion 9 having a smaller cross-sectional area than the outlet 8 above the outlet 8. The sectional shape of the throat portion 9 and the sectional shape of the outlet 8 are the same. It is not necessary. That is, the cross-sectional shape of the throat portion 9 and the cross-sectional shape of the outlet 8 may be different from each other such as an elliptical shape and an oval shape. However, it is preferable that the both cross-sectional shapes be similar to each other so that the cross-section of the outlet 8 can be obtained by enlarging the cross-section of the throat portion 9 as it is. Note that this similar shape includes, for example, a case where the cross-sectional shape of the throat portion 9 is an elliptical shape that is long in the circumferential direction and the cross-sectional shape of the outlet 8 is an elliptical shape that is long in the radial direction, that is, the formation direction is different. Includes similar items. Thus, if the cross-sectional shape of the throat portion 9 and the cross-sectional shape of the outlet 8 are similar to each other, the decarburizing blown lance tip 1 of the present invention can be produced using an existing processing method such as casting. This is because it becomes easy.

  Each of the plurality of nozzles 7 described above has a throat structure in order to form a jet. The nozzle 7 having such a throat structure is generally called a Laval nozzle (see, for example, Japanese Patent Application Laid-Open No. 2014-224309). If such a Laval nozzle is used, the jet ejected from the nozzle 7 becomes a so-called jet jet, and a sonic jet can be formed. Therefore, the flow velocity at the stage of reaching the molten metal surface does not become too low (a jet flow that can ensure a flow velocity of 30 m / s or more can be formed on the molten metal surface), and the decarburization reaction can be performed efficiently (Japanese Patent Laid-Open No. Hei 7). -3318 etc.).

  If a plurality of nozzles 7 are formed on the decarburizing blown lance tip 1 described above, the jet flow is easily attenuated by being divided into a plurality of nozzles 7 and the flow velocity at the time of the hot water surface collision is sufficiently low. can do. That is, the attenuation of the jet flow ejected from the nozzle 7 is caused by the jet flow involving the external gas at the boundary surface between the external gas and the jet flow, and the momentum (kinetic energy) of the jet flow is transmitted to the external gas. That is, when the nozzle 7 is a single-hole tip, there is only one jet ejected from the nozzle 7, and the surface area of the jet contacting the external gas is small. Therefore, when the nozzle 7 employs a single-hole tip, the jet momentum attenuation is small, and the flow velocity at the time of the hot water surface collision remains high. However, in the case where the nozzle 7 has a plurality of (multi-hole) tips, there are a plurality of jets ejected from the nozzle 7, and the total surface area of the jet contacting the external gas becomes large. Therefore, the momentum of the jet is also attenuated. growing. For this reason, when a chip having a plurality of nozzles 7 is employed, the flow velocity at the time of a hot water surface collision can be sufficiently lowered (attenuated) by being divided into a plurality of nozzles 7 and ejected.

  Thus, if the flow velocity at the time of the hot water surface collision can be reduced, it becomes difficult for intense spitting to occur at the fire point (near the hot water surface), and it is possible to prevent an increase in dust loss due to spitting. Therefore, a tip provided with a plurality of nozzles 7, specifically, a decarburizing blown lance tip 1 in which the hole occupation angle of the nozzle 7 is 330 ° or less is used in this embodiment.

  As for the opening shape of the nozzle 7, by adopting a flat (flat) opening shape compared to a circle such as an ellipse, in other words, an opening shape having a large aspect ratio, the flow velocity of the jet flow from the nozzle 7 can be reduced. Attenuation can be increased (see JP-A-8-60219). Therefore, from the viewpoint of adopting the opening shape of the nozzle 7 that can sufficiently reduce the flow velocity at the time of the hot water surface collision, that is, from the viewpoint of soft blow, the nozzle having an opening shape that is longer than a perfect circle. 7 is preferably used.

Even when a plurality of nozzles having the elongated opening shape (opening shape having a large aspect ratio) as described above are provided at the tip of the chip, if the jets ejected from the nozzles are curved and the jets merge, It becomes difficult to obtain.
That is, since a negative pressure is generated between the jets ejected from the nozzles adjacent to the tip end surface of the tip, the phenomenon that the jets are curved inward due to the pressure difference occurs. Such a phenomenon is particularly likely to occur near the center of a circle, for example, when a plurality of nozzles are arranged on the same circle. In particular, when the flow velocity of the jet ejected from the nozzle is low, this curvature tends to increase (prone to occur easily).

When jets ejected from adjacent nozzles overlap due to curvature, the jets merge to form a strong flow (hard blow), and the flow velocity at the point of molten metal collision is sufficiently reduced. The blow effect cannot be obtained.
For this reason, in order to realize soft blow with a tip having a nozzle having an unequal cross-sectional shape, it is necessary to prevent the overlapping of jets due to bending.

That is, the decarburizing blown lance tip 1 of the present invention defines the opening shape and the number of holes of the nozzle 7 so as to prevent the overlapping of jets due to bending.
In recent years, computational technology has made great progress, and it has become possible to perform flow analysis of compressible fluids, which has been difficult in the past, relatively easily. The number of cases where the chip shape is originally designed is increasing.

Specifically, in the decarburization blown lance tip 1 of the present embodiment, the throat portion 9 and the outlet 8 of the nozzle 7 have the same non-circular cross-sectional shape as described above, and these The throat portion 9 and the outlet 8 of the decarburizing lance 4 have a feature that they are arranged side by side in a rotationally symmetric state at an equal angle on a concentric circle with respect to the axis of the decarburizing blow lance 4. However, the decarburizing blown lance tip 1 of the present embodiment has not only these characteristics but also the characteristics shown in the following (Condition 1) and (Condition 2).
(Condition 1)
“When the cross-sectional shape of the throat portion 9 is converted into an ellipse, the aspect ratio of the cross-sectional shape converted into an ellipse is 2.4 to 5.5, preferably 2.4 to 3.8.”
(Condition 2)
“When the bottom surface of the decarburizing blown lance tip 1 is viewed 360 ° in the circumferential direction around the axis of the decarburized blown lance 4, the total hole area occupied by the nozzle 7 is occupied. The angle θ is set to 330 ° or less. ''
Of the two conditions described above, (Condition 1) is obtained by treating this section as an ellipse with respect to the section of the nozzle 7 (the section of the throat section 9) cut at the location where the throat section 9 is formed. When the aspect ratio is obtained, the aspect ratio is 2.4 or more and 5.5 or less, preferably 3.8 or less.

  The aspect ratio described above is a ratio obtained by dividing the major axis (major axis) of an ellipse or circle by the minor axis (minor axis). For example, the aspect ratio of the circle is 1. When such an aspect ratio is used, even when the cross-sectional shape of the throat portion 9 is not a circle or an ellipse, in other words, even when the cross-sectional shape is a distorted shape such as a rice ball shape or a football shape, the aspect ratio is the same. The cross-sectional shape of the throat portion 9 and the outlet 8 of the nozzle 7 can be evaluated using the index.

Specifically, this aspect ratio can be obtained by performing <Procedure 1> to <Procedure 3> shown in FIG.
<Procedure 1>
At the throat cross-sectional position (the cross section of the throat portion 9 perpendicular to the axis of the nozzle 7), a straight line extending radially from the axis of the nozzle 7 is drawn, and the opening edge of the throat portion 9 in the radially drawn straight line The angle formed between the _two straight lines L ₁ and L ₂ is divided into two equal parts with respect to the two straight lines L ₁ and L ₂ extending so as to give up (being tangent to the opening edge of the throat portion 9) the length of the straight line L _M to traverse the cross-section of the throat portion 9 and the short diameter b.
<Procedure 2>
When the cross-sectional area S of the throat portion 9 (opening area S of the throat portion 9) and the minor axis b obtained in the procedure of <1> are substituted into the following formula (1), the throat portion 9 is treated as an ellipse. The major axis a is obtained.
<Procedure 3>
The aspect ratio of the cross section of the throat portion 9 is obtained by dividing the major axis a obtained by the procedure <2> by the minor axis b obtained by the procedure <1>.

  Note that the above-described procedures <1> to <3> are merely examples for converting the cross-sectional shape of the nozzle 7 into an ellipse. For example, an ellipse that can represent the contour of the measured cross-sectional shape most accurately is obtained as a mathematical formula by fitting a pre-modeled (formulated) ellipse to the measured cross-sectional contour of the nozzle 7. The aspect ratio can also be calculated from the obtained ellipse formula.

The aspect ratio of the throat portion 9 described above is 2.4 to 5.5 (2.4 or more and 5.5 or less), preferably 2.4 to 3.8 (2.4 or more, And 3.8 or less) for the following reason.
That is, the above (Condition 1) is preferably satisfied for at least one of the plurality of nozzles 7, and more preferably is satisfied for all the nozzles 7.

Generally, when the aspect ratio of the cross section of the throat portion 9 is increased, the effect of soft blowing is increased. However, when the above-described aspect ratio of the cross section of the throat portion 9 is less than 2.4, the effect of the elliptical jet (soft blow) Cannot be obtained sufficiently, and the collision with the molten metal surface remains at a high flow rate, so that a satisfactory soft blow effect cannot be obtained.
Also, if the aspect ratio exceeds 5.5, preferably 3.8, the jet jets ejected from each nozzle 7 will surely weaken, but as described above, the jets merge together due to the curvature. Therefore, the soft blow effect cannot be obtained. Therefore, the aspect ratio needs to be 2.4 or more and 5.5 or less, preferably 3.8 or less.

  Further, as described above, in order to realize soft blow, the jets ejected from the nozzles 7 are curved toward the axial center side of the decarburization lance 4 and jets ejected from the adjacent nozzles 7 It is important to prevent the components from being integrated. The curvature of the jet is generated because the space surrounded by the jet (in the case of the present embodiment, the space formed near the axis of the decarburizing lance 4 for decarburization) has a negative pressure with respect to the jet. . However, if there is a gap that allows outside air to enter between adjacent jets (jet jets), the outside air enters the space surrounded by the jet through such a gap, so the space between the jets is negative pressure. (Negative pressure is reduced), and as a result, the curvature of the jet is also suppressed. In other words, if the gap between the jets is too narrow, that is, if the above-described hole occupying angle is too large, the gap between the jets becomes small and outside air does not enter. For example, assuming that the outlet 8 of the nozzle 7 has an annular opening, it is clear from the fact that there is no gap and no outside air enters. That is, if the hole occupation angle θ is too large, the pressure in the space surrounded by the jet (jet jet) tends to be low, and bending tends to occur.

Specifically, the hole occupation angle θ described above can be obtained as follows.
As shown in FIG. 5, the hole occupation angle θ ₁ is _first obtained for the nozzle 7 located in the upper right of the figure. When a straight line is drawn radially in the radial direction from the axial center of the decarburizing blow lance 4 described above, two line segments that make point contact with the outer edge of the outlet 8 of the nozzle 7 located at the upper right of the drawing are drawn. be able to. When these two line segments are L ₃ and L ₄ , the angle surrounded by the two line segments L ₃ and L ₄ is the occupation angle θ _{1 of the} nozzle 7. The occupation angle θ ₁ obtained in this way is for the nozzle 7 located in the upper right of FIG. 5, but the occupation angles θ ₂ and θ ₃ can be obtained in the same manner for the nozzles 7 other than the upper right. In this way, for all the nozzles 7 formed at the tip of the decarburizing blown lance tip 1, the occupied angles θ _{1 to} θ ₃ are integrated to obtain the hole occupied angle θ in (Condition 2) (example in FIG. 5). If so, θ = θ ₁ + θ ₂ + θ ₃ ). Further, the hole occupying angle obtained in this way is 360 ° in the case of the nozzle 7 having an endless and annular cross-sectional shape continuous in the circumferential direction.

In other words, the above-mentioned “hole occupation angle is 330 ° or less” indicates the upper limit of the hole occupation angle θ regardless of the number of nozzles 7. If the hole occupying angle θ exceeds 330 °, the jet flow ejected from the nozzle 7 becomes severely curved, so that hard blow occurs due to integration of the jet jets, and the intended soft blow can be realized. Disappear.
In addition, the suppression part 10 which suppresses the flow of the jet flow spouted from the nozzle 7 can also be formed in the exit 8 of the nozzle 7 mentioned above. If such a suppression part 10 is formed, it prevents that the jet (jet) which spouted from the nozzle 7 curves toward the axial center side of the decarburization blow lance 4, and adjoins adjacent jets. be able to.

  Such installation of the suppression unit 10 is not disclosed in prior literatures such as Japanese Patent Application Laid-Open Nos. 8-1557928 and 61-143507 described in “Problems to be Solved by the Invention”. In other words, these prior documents disclose a member (suppressing portion 10) that suppresses a jet flow such as a baffle plate or a protrusion to prevent the jet jet flow ejected from the nozzle at the nozzle outlet from being curved inward (spread outward). It has not been. In other words, in these prior documents, since the bending of the jet jet inward cannot be suppressed, the jet may be hard blown by the merge of the jets, and soft blow cannot be expected.

However, the restraining portion 10 of the present embodiment is a plate member that is detachably provided at the distal end side of the decarburizing blown lance tip 1 and can close a part of the outlet 8 (opening of the outlet 8) of the nozzle 7. It is said that. The suppressing unit 10 may be a plate member (a member such as a baffle plate) capable of attenuating the jet flow ejected from the nozzle 7, or may be a portion (projection) formed in a protruding shape at the outlet 8 of the nozzle 7. .
The reason for providing such a suppression unit 10 is as follows. That is, as described above, in the decarburizing blown lance tip 1 of the present embodiment adopting the Laval structure, the fluid compressed in the throat portion 9 expands toward the outlet 8 of the nozzle 7, thereby generating a jet jet. It is formed. It is known that when the jet jet comes into contact with an obstacle in the area where the jet jet is formed, for example, in the vicinity of the outlet 8 of the nozzle 7, the flow velocity of the jet jet decreases while generating a sonic boom (shock wave). . That is, by installing the suppression unit 10 at the outlet 8 of the nozzle 7, the flow velocity of the jet ejected from the nozzle 7 can be reduced and soft blowing can be realized.

  In addition, it is preferable to form the suppressing part 10 so that it protrudes with the protrusion width more than 1/4 of opening width toward the direction away from an axial center from the opening edge of the axial center side in the exit 8 of the nozzle 7. FIG. When the size of the suppressing portion 10 is less than this, the contact area with the jet becomes small, and a satisfactory soft blow effect cannot be obtained. Further, as described above, simply lowering the flow velocity of the jet increases the curvature and makes it easy to merge. Therefore, the suppression part 10 is installed in the opening edge by the side of an axial center, and the coalescence of a jet is prevented by suppressing the jet flow of the axial center side which is easy to unite.

On the other hand, when the above-described suppression unit 10 is installed, the total flow rate of oxygen gas ejected from the decarburizing blow lance 4 is 0.5 to 1.5 [Nm ³ / min] (the total flow rate of oxygen gas is 0.5 Nm ³ / min or more and 1.5 Nm ³ / min or less), the improper degree determined from the flow rate of oxygen ejected from the nozzle 7, the cross-sectional area of the throat portion 9 and the cross-sectional area of the outlet 8 is 0.6 to It is preferable to form the suppression part 10 so that it may become 0.9.

  Here, the improper degree is an index indicating whether or not the jet jet is appropriately compressed. When the improper degree = 1, the pressure at the nozzle outlet becomes equal to the external pressure, and the energy conversion efficiency is the highest. And a powerful jet can be obtained. When this degree of improperness = 1, it is said to be “proper expansion”. On the other hand, when the degree of improperness ≠ 1, it is called “improper expansion” and the outlet pressure does not become equal to the external pressure. In particular, when the degree of improperness <1, it is called “overexpansion” and the outlet pressure is equal to or lower than the external pressure. In this case, since the conversion efficiency of pressure → kinetic energy at the nozzle 7 is low, soft blow can be realized. However, if the soft blow is performed too much, the above-described curve occurs and the jet jets are united and integrated, and as a result, the soft blow effect cannot be obtained. Therefore, there exists an optimal range in which the soft blow effect can be surely exhibited in the unsuitability degree.

Specifically, the optimum range of the inappropriateness degree of the present embodiment is set to 0.6 to 0.9. When the degree of improperness is 0.9 or more, the energy conversion efficiency when pressure is converted into kinetic energy increases, a powerful jet jet is formed, and the collision flow velocity on the molten metal surface also increases. (Soft blow effect cannot be obtained).
Further, when the degree of improperness is 0.6 or less, although the soft blow is performed in the vicinity of the outlet 8 of the nozzle 7, the jet jets ejected from the adjacent nozzles 7 are integrated by bending, so that the jet jet Attenuation becomes slow, resulting in a high collision flow velocity on the molten metal surface (soft blow effect cannot be obtained).

Therefore, the unsuitability degree needs to be in the range of 0.6 to 0.9.
It should be noted that the degree of inappropriateness described above can be actually calculated by the following procedure.
As described above, the degree of improperness (in the following formulas, the symbol f may be used to indicate the degree of improperness) is an index that represents the degree of expansion of the jet, and is expressed by the following formula (2). The

When the degree of improperness is f = 1, this is called proper expansion, and the nozzle efficiency is maximized. Further, when the degree of inadequate f <1 or the degree of inadequate f> 1, it is called overexpansion and underexpansion, respectively, and the nozzle efficiency is lower than that at the time of appropriate expansion.
In equation (2), the denominator p _0p represents “the pre-nozzle pressure during proper expansion” and is calculated as follows. The “pressure before nozzle” indicates the pressure before “nozzle” shown in FIG.

That is, assuming that the jet expansion is adiabatic expansion, the area ratio obtained by dividing the cross-sectional area (A _e ) of the outlet 8 of the nozzle 7 by the cross-sectional area (A ^* ) of the throat portion 9 of the nozzle 7 and the outlet 8 of the nozzle 7. Since the value (M _e ) showing the flow velocity of the jet at Mach number in Equation (3) is in the relationship of Equation (3), if the specific heat ratio is λ, the jet at the outlet 8 of the nozzle 7 from the area ratio (Ae / A *) The Mach number Me can be calculated as follows.

Further, the Mach number of the jet flow at the outlet 8 of the nozzle 7, the pressure on the inlet side of the nozzle 7 to be measured, and the pressure on the outlet side of the nozzle 7 are in the relationship of Expression (4). Since the proper expansion described above a case where the outlet pressure is equal to the outside pressure, the pressure p _e of the outlet 8 of the Mach number M _e, and the nozzle 7 at the outlet 8 of the nozzle 7 was calculated by the formula (3) = When 1.013 × 105 [Pa] is substituted, the pressure p _0p = p ₀ on the inlet side of the nozzle 7 at the time of proper expansion is obtained.

In equation (2), the numerator p ₀ is the actual pressure on the inlet side of the nozzle 7 to be obtained. From the mass flow velocity m ^* of the gas (oxygen) flowing through the nozzle 7, the following equation (5) Desired.

  In addition, each parameter used in the above-described formulas (2) to (5) is as shown in Table 1 below.

If the decarburizing blown lance tip 1 of the present embodiment having the above-described features is used, the flow velocity of the jet flow ejected from the nozzle 7 can be reduced, and soft blow can be realized. That is, if the decarburization blown lance tip 1 of the present embodiment is used, soft blow can be realized without reducing the flow rate (O ₂ flow rate) of the oxygen gas ejected from the nozzle 7 and the lance height. Soft blow can be realized without increasing the height. Therefore, the collision flow velocity to the molten metal surface during blowing can be reduced, and spitting generated during blowing can be reduced.

The operational effects of the decarburizing blown lance tip 1 of the present invention described above will be described in more detail using Examples and Comparative Examples.
In the example and the comparative example, when the conditions such as the opening shape of the nozzle 7, the number of holes of the nozzle 7, and the presence / absence of the suppressing portion 10 (baffle plate) are changed, the jet flow ejected from the nozzle 7 collides with the molten metal surface. Flow analysis using Fluent (Ver. Ansys14.5) to see how the central dynamic pressure (dynamic pressure at the center of the jet jet) and the central flow velocity (velocity at the center of the jet jet) change It is calculated by. In all of the examples and comparative examples, the oxygen flow rate is 1000 Nm ³ / min.

Further, the decarburization blown lance tips of the examples and comparative examples used in the flow analysis have a 6-hole lance with a perfect opening as a base shape, and a plurality of adjacent nozzles are formed from these 6 holes. As a result, the nozzle 7 having an increased aspect ratio is appropriately formed.
Furthermore, Example 1 satisfies the above-mentioned (Condition 1) and (Condition 2). In addition to (Condition 1) and (Condition 2) described above, Example 2 is provided at the outlet 8 of the nozzle 7. A flow rate of oxygen ejected from the nozzle is formed while forming a restraining portion 10 (baffle plate) that projects with a projecting width that is 1/4 or more of the opening width of the outlet 8 in the direction away from the axial center opening edge. The degree of inadequacy obtained from the cross-sectional area of the throat portion and the cross-sectional area of the outlet satisfies the condition of 0.6 to 0.9. In addition, all the thickness of the suppression part 10 formed in the exit 8 is 10 mm.

  First, the base shape of the hole connection of the nozzle 7 will be described. This decarburized blown lance tip for base decarburization is a short cylindrical shape (disk shape) with a diameter (diameter) of φ355.6 mm, and has 6 holes at equal intervals on a concentric circle 234 mm from the center. Has a round nozzle outlet. In addition, as the base shape of the hole connection, in addition to the above-described six holes, a four-hole shape was also prepared. That is, it can be said that these base shapes are rotationally symmetric at 60 ° with respect to the axis of the decarburizing blow lance, or are rotationally symmetric at 90 °. Further, an oxygen flow path for circulating oxygen gas is formed inside the decarburization blow lance. Each of these 6-hole or 4-hole nozzles connects the inlet that opens to the oxygen flow path inside the decarburizing blow lance and the outlet that is formed at the tip of the decarburizing blow lance tip. In this example, the total length is 173 mm. Inside each nozzle hole, a throat portion is formed at a position of 140 mm from the outlet toward the back side. The throat portion is a portion that is narrower than the opening diameter of the outlet of the nozzle hole, and is formed over a length of 10 mm with respect to the longitudinal direction of the lance hole.

In contrast to the base shape described above, the nozzles of the example and the comparative example are non-circular by joining two, three, and six holes adjacent to each other among the six or four holes in the base shape. A nozzle with a shape is created.
Specifically, in Experiment No. 1 to Experiment No. 19, adjacent two holes or three holes are connected to form a non-circular (arc-shaped) nozzle 7. These experiment numbers 1 to 19 are shown as “Example 1” in Table 3. Experiment numbers 20 to 28 are two non-circular (arc-shaped) nozzles 7 formed by connecting two adjacent holes. These experiment numbers 20 to 28 are shown as “Example 2” in Table 4. Furthermore, Experiment No. 29 to Experiment No. 34 are nozzles formed by connecting all three or six holes, and constitute “Comparative Example 1” in Table 5.

As shown in FIG. 5, the nozzles of Example 1, Example 2, and Comparative Example 1 are inclined (inclined) with respect to the axis of the decarburization blow lance (up and down direction on the paper surface of FIG. 5). Angle) It is inclined at 10 to 30 [deg.].
In addition, data such as dimensions other than those described above, in other words, Fluent calculation conditions used for the flow analysis are as shown in Table 2.

For the examples and comparative examples described above, “central dynamic pressure” and “central flow velocity” were obtained to evaluate whether or not soft blow could be realized.
The “central dynamic pressure” used for the evaluation is calculated using the Fluent for the dynamic pressure at the center of the jet at a position 2.8 m below the lance height (exit) in the free jet of the jet (no obstacles). It is. By setting the “central dynamic pressure” to 19.6 [kPa] or less, the amount of dust generated after the middle stage of blowing can be reduced (see JP 2013-49890 A). Therefore, in the present example and the comparative example, when the “central dynamic pressure” is 19.6 [kPa] or less, the evaluation of “◯ (there is an effect of soft blowing)” and the “central dynamic pressure” is 19.6. Those with less than [kPa] were evaluated as “× (no effect of soft blowing)”.

  Furthermore, the “center flow velocity” is the flow velocity calculated at the center of the jet 2.8 m below the lance height (exit) using Fluent in the free jet of the jet (no obstacles). By setting the “center flow velocity” to 70 [m / s] or less, the amount of dust generated during blowing can be reduced (see Japanese Patent Application Laid-Open No. 7-3318). Therefore, in the present example and the comparative example, even when the “center flow velocity” is equal to or less than 70 [m / s], the evaluation of “◯ (there is an effect of soft blow)” and the “center flow velocity” is 70 [m / s]. ] Was also evaluated as “× (no effect of soft blow)”.

The condition of “center flow velocity” is stricter than the above-mentioned “center dynamic pressure”.
Therefore, as the “comprehensive evaluation”, if the “central dynamic pressure” is not only “○” but also the “central flow velocity” is also evaluated as “◯”, the “comprehensive evaluation” is set to “◎ ( The effect is great). On the other hand, the case where either “center flow velocity” or “center dynamic pressure” is “◯” is set to “◯ (the effect of soft blow)”.

  As shown in Table 6, among the experiment numbers 1 to 34 described above, the center motions of the experiment numbers 1, 2, and 3 as “Example 1” and the experiment numbers 20, 21, and 22 as “Example 2” When the pressure is obtained, it becomes 2.1 kPa to 6.3 kPa, which is a threshold value of 19.6 kPa or less. However, in all the experimental examples of Comparative Example 1, the central dynamic pressure exceeds the threshold value of 19.6 kPa. From this, it can be seen that Example 1 and Example 2 can reduce the center dynamic pressure at the time of the molten metal collision as compared with Comparative Example 1.

  On the other hand, as shown in Table 7, when the center flow velocity was determined for Experiment Nos. 1, 2, and 3 as “Example 1” and Experiment Nos. 20, 21, and 22 as “Example 2”, 80.1 was found for Example 1. m / s to 97.8 m / s, which exceeds the threshold value of 70 m / s, but in Example 2, it is 54.9 m / s to 68.3 m / s, which is the threshold value of 70 m / s or less. From this, it can be seen that Example 2 can reduce the center flow velocity at the time of a hot water surface collision not only in Comparative Example 1 but also in Example 1.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

DESCRIPTION OF SYMBOLS 1 Blowing lance tip for decarburization 2 Converter equipment 3 Converter 4 Blowing lance for decarburization 5 Tuyere 6 Oxygen flow path 7 Nozzle 8 Nozzle outlet 9 Throat part 10 Control part

Claims (2)

A decarburization blown lance tip attached to the tip of a decarburization blown lance used when performing decarburization treatment of hot metal in a converter vessel,
It has a plurality of nozzles for ejecting oxygen to the hot metal, and the plurality of nozzles has a throat structure having a throat portion narrowed in a diameter smaller than the outlet in the hole,
Each of the cross-sectional shapes formed in the plurality of nozzles in the throat portion is equal and non-circular, and each of the cross-sectional shapes formed in the plurality of nozzles in the outlet is equal and non-circular. And
The throat portions and outlets of the plurality of nozzles are arranged on a concentric circle with respect to the axis of the decarburization blow lance, and are equiangular with each other around the axis, and are mutually A blown lance tip for decarburization, which is arranged in a rotationally symmetric state, and wherein the plurality of nozzles satisfy the following conditions.
(Condition 1)
“When the cross-sectional shape of the throat portion is converted into an ellipse, the aspect ratio of the cross-sectional shape converted into an ellipse is 2.4 to 5.5”
(Condition 2)
“When the bottom surface of the decarburizing blown lance tip is viewed in the circumferential direction 360 ° around the axis of the decarburizing blown lance, the total hole occupation angle is the angle range in which the nozzles are present. 330 ° or less. '' The outlet of the nozzle is formed with a suppressing portion that suppresses the flow of the jet ejected from the nozzle,
The suppressing portion is formed so as to protrude with a protruding width of 1/4 or more of the opening width toward the direction away from the axial center from the opening edge on the axial center side at the outlet of the nozzle,
2. The decarburization blow according to claim 1, wherein an inadequate degree determined from a flow rate of oxygen ejected from the nozzle, a cross-sectional area of the throat portion, and a cross-sectional area of the outlet is 0.6 to 0.9. Alchemy lance tip.