JPH11158529A - Refining lance - Google Patents

Abstract

(57) [Summary] [PROBLEMS] For refining that can efficiently suppress the generation of splash and dust during refining and improve refining efficiency such as decarbonation efficiency to perform highly productive refining processing. Provide a lance. SOLUTION: A smelting lance 1 which is used under atmospheric pressure or reduced pressure and blows out gas from a lower nozzle portion 14a at a high speed.
In No. 4, a hollow portion 18 was provided in a gas flow path at an intermediate position of the nozzle portion 14a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for refining molten steel under atmospheric pressure or reduced pressure, in which oxygen gas, argon gas, hydrogen gas, nitrogen gas, or a mixed gas thereof is blown onto the molten steel surface of the molten steel. Refining lance used to perform refining.

[0002]

2. Description of the Related Art Conventionally, in steelmaking refining furnaces such as a converter used at atmospheric pressure, a VOD furnace, a DH furnace, and a RH furnace for refining molten steel under reduced pressure, steelmaking refining is performed through an upper blowing lance. A gas such as oxygen gas is sprayed on the molten steel surface of the molten steel held in the furnace, and the molten steel is stirred by the jet flow of the oxygen gas, so that the oxygen gas comes into contact with and reacts with the carbon in the molten steel. Is being done. In a decarburization refining furnace typified by a converter, etc., in order to carry out decarburization blowing operation while maintaining an appropriate lance gap between the tip of the upper blowing lance and the molten steel surface, the nozzle tip A lance of a Laval nozzle having a taper that expands its diameter has been proposed, and decarburization refining in which a jet flow of oxygen gas is blown onto a molten steel surface while minimizing energy loss of a jet flow has been performed. further,
When improvement in productivity is required and it is necessary to blow gas at a large flow rate, it is common to use a so-called perforated lance having a plurality of outlets for gas discharge flow. The use of a porous lance is not limited to spraying excessive gas such as oxygen gas through a single hole, which not only reduces iron yield due to dust and splash, but also causes This is because the depth of the cavity formed on the surface reaches the depth of the steel bath, and the refractory at the furnace bottom is significantly damaged. It is known that a large amount of dust is generated due to the generation of splash including molten steel and slag at the time of such decarburization refining, thereby lowering the production yield. Also, when chromium component is contained in molten steel,
Since the chromium component is oxidized by the oxygen gas, the generated chromium oxide is taken into slag from the molten steel into the slag on the molten steel surface, causing chromium loss to increase.

As a method for preventing dust generation or chromium loss in decarburization refining using such a steelmaking refining furnace, for example, the following techniques are known. Japanese Patent Application Laid-Open No. 6-57320 discloses that six or more types of Laval nozzles having different inclination angles are alternately arranged in a circumferential direction, and are formed by a jet stream of gas injected from each of these nozzles. An upper blowing lance for refining molten metal for performing refining with a geometrical overlap area ratio of each cavity on the steel bath surface of 30% or less is shown. Japanese Patent Publication No. 62-46611 discloses an upper blowing lance having a plurality of nozzles arranged in a circumferential direction, the diameter of a cavity formed in a molten steel surface by the nozzle,
An upper blowing lance for determining a nozzle angle or the like so that an overlap ratio expressed by a ratio to a length of an overlapping portion with an adjacent cavity is 0.2 or less is described. Japanese Patent Application Laid-Open No. 58-193309 discloses a coolant for cooling a hot spot such as CO ₂ , CaCO ₃ , water vapor, and water when refining molten steel in a state in which slag to be formed is minimal or slag-free. A method of refining steel added from a supply port communicating with a blowing oxygen nozzle hole has been proposed. Japanese Patent Application Laid-Open No. 55-94421 discloses a method in which a carbon dioxide gas supply system is connected to an oxygen supply path of an upper blowing lance, and only oxygen is blown or carbonated from the beginning to the end of blowing depending on the hot metal component to be blown. An operation method in an upper-blowing oxygen converter that increases the amount of exhaust gas recovered by performing blowing with a combination of blowing only gas or mixed blowing of oxygen gas and carbon dioxide gas and controlling the low-fire temperature is shown. I have.

[0004]

However, the above-mentioned upper blowing lance and the refining method using the same have the following problems. Is a method of preventing interference between cavities by making the lance porous or optimizing the arrangement of the nozzles. In each case, a negative pressure is generated between the jet flows ejected from each nozzle. It is difficult to completely control the interference between the cavities caused by the cavities. Further, in the above, the jet stream of the oxygen gas to be blown is cooled to a hot spot generated by colliding with the molten steel surface to suppress the fume dust generated from the hot spot. By cooling the section, there is a problem that the decarbonation efficiency in a low carbon region is reduced and the refining efficiency of molten steel is deteriorated. Furthermore, all of these are intended for decarburization refining under atmospheric pressure in a converter,
In blowing acid decarburization in a vacuum such as VOD, the jet flow of oxygen gas is blown into a reduced atmospheric pressure and expanded, resulting in a large hard blow compared to the atmospheric pressure. When applied to blowing acid decarburization under reduced pressure, it has been difficult to effectively suppress the generation of splash and dust.

[0005] The present invention has been made in view of such circumstances, and efficiently suppresses the generation of splash and dust during refining, and improves the refining efficiency such as decarbonation efficiency to improve the productivity. An object is to provide a smelting lance that can perform a smelting process.

[0006]

According to the present invention, there is provided a semiconductor device comprising:
The refining lance described is used under atmospheric pressure or reduced pressure,
In a refining lance that blows gas at a high speed from a lower nozzle portion, a hollow portion is provided in the gas flow path at an intermediate position of the nozzle portion. The lance for refining according to claim 2 is used under atmospheric pressure or reduced pressure to blow oxygen gas onto the molten steel surface of the molten steel to be treated from a lower nozzle portion to oxidize and decarbonize the carbon content in the molten steel. In the refining lance to be used, a hollow portion having a step in the flow path of the oxygen gas is provided at an intermediate position of the nozzle portion. In the lance for refining according to the third aspect, in the lance for refining according to the second aspect, the throat portion where the cross section of the flow path of the oxygen gas is minimized is 50 to 2000 Nm ³ / hr / per unit area.
cm ² of oxygen gas is supplied. A lance for refining according to a fourth aspect is the lance for refining according to any one of the first to third aspects, wherein the nozzle portion has a Laval shape in which a cross section of a main flow path expands downward. A lance for refining according to a fifth aspect is the lance for refining according to any one of the first to third aspects, wherein the nozzle portion has a straight structure in which a cross section of a main flow path is cylindrical. The lance for refining according to claim 6 is the lance for refining according to any one of claims 1 to 5, wherein the inner diameter of the hollow portion is larger than the inner diameter of the throat portion to which the hollow portion is connected. Is formed.

[0007] The nozzle portion is a throat portion in which the gas flow section located above the gas discharge port of the refining lance has a minimum flow path cross section. A part that has the function of adjusting the flow of information. The hollow part is a part where the pressure of oxygen gas passing through the gas flow path is partially reduced, thereby drawing in the gas and restoring the pressure of the gas. It refers to a portion that can be applied to the gas passing through the pulsation caused by the generation of the vortex flow of oxygen gas. Further, the step portion is a portion where the change in the inclination of the tangent line on the surface of the gas flow path with which the gas flow contacts is discontinuous, and it is possible to cause the gas pressure to fluctuate in this portion. The flow rate of oxygen gas per unit area supplied to the throat portion in the oxygen gas flow path is 50 Nm ³ / hr / cm ²
If the amount is smaller, a sufficient pulsation effect cannot be generated due to a small flow rate, and it becomes difficult to improve the decarbonation efficiency. Conversely, this oxygen gas flow rate is 2000 Nm ³
/ Hr / cm ² , the generation of the splash becomes intense beyond the limit, the yield decreases due to dust,
It is not preferable because refractory damage becomes remarkable.

[0008] In general decarburization refining, even if extreme soft blowing is performed to suppress the generation of splash, the remarkable decrease in decarboxylation efficiency in the oxygen supply rate-limiting region at the peak of decarburization. unacceptable. However, in the carbon-carbon-controlled region where the carbon concentration is below the critical carbon concentration, the renewal speed of molten steel supplied to the hot spot, which is the site of the main decarburization reaction, is insufficient, leading to an extreme decrease in decarbonation efficiency. Will be. When the present invention is applied to decarburization refining, it is possible to suppress the generation of splash and dust and to maintain the decarboxylation efficiency at a high level in the carbon transfer-controlling region (low carbon region) in steel. Then, the soft blow of the oxygen gas blown to the molten steel surface is realized, and the molten steel surface at the hot spot at that time is maintained in an active state. That is, a pulsation phenomenon is caused in the gas jet stream, and the energy loss at this time enables the jet stream itself to be soft blown, and the pulsating jet stream collides with the molten steel surface. Since the jet flow itself has a pulsating wave, the pulsating wave propagates in a region where the jet stream collides with the molten steel surface (a hot spot in the case of oxygen gas), and the renewal of the molten steel surface becomes active. The decarbonation efficiency and the like when oxygen gas is used can be maintained at a high level. In addition, since the soft blow can be realized, the generation of splash and dust during refining can be significantly reduced. Furthermore, since the amount of energy consumed to generate pulsation is large, the contact of the gas on the molten steel surface is soft and the generation of splash is suppressed, thereby enabling a large supply of gas and improving the production efficiency of refining. Can be enhanced. In addition, in the refining under reduced pressure using a vacuum refining furnace as well as under the atmospheric pressure of a converter or the like, the gas discharged from the nozzle portion is reduced under reduced pressure as compared with the case of using a normal Laval nozzle or a straight nozzle. It is possible to reduce the influence of the degree of vacuum that is blown into the atmosphere and rapidly expands to increase the splash.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is an explanatory diagram of a converter facility using a lance for refining according to an embodiment of the present invention. As shown in FIG. 1, a converter facility 10 employing a lance for refining according to an embodiment of the present invention includes a converter 12 for holding a molten steel 11 and performing refining by a decarburization reaction or the like.
Lance 14 for blowing acid decarburization for blowing oxygen gas onto molten steel surface 13 formed by 1 (an example of a lance for refining)
And The molten steel 11 has a chromium component of 3 to 20 wt%.
It is molten steel or crude molten steel for stainless steel containing, taking out hot metal from a blast furnace, adjusting the sulfur content, silicon content, etc. in the hot metal, and then adding alloy components such as chromium as necessary. . The converter 12 is a steel shell 1 lined with a refractory brick 15 made of magnesia carbonaceous material or the like.
6 is a smelting vessel having molten steel 1
1 to supply molten steel 11 after refining from a tapping hole (not shown) provided on the upper side surface. The lance 14 for blowing acid decarburization is a substantially cylindrical gas injection pipe whose exterior is constructed with a refractory such as castable,
Oxygen gas is supplied from a gas passage formed inside a cored bar (not shown) disposed inside, and the oxygen gas is blown toward the molten steel surface 13 through a nozzle provided at a tip end portion. The lance 14 for blowing acid decarburization can be moved up and down by using a lifting device (not shown).
The spray distance (B + C) up to 3 can be adjusted as needed. The oxygen gas region B shown in FIG. 1 is a jet core region (supersonic region) in which the gas flow velocity is higher than the sonic speed and the cross-sectional area of the gas flow is small in the flow direction. It is a free jet area that expands rapidly. The size of the regions B and C and the size of the cavity region D are determined by the supply speed of the oxygen gas, the gas discharge angle at the nozzle tip, the nozzle diameter, and the like.

The detailed structure of the nozzle portion 14a at the lower end of the lance 14 for blowing acid decarburization is shown in FIG. The nozzle portion 14a is connected to the throat portion 17 that is reduced in diameter in the discharge direction of the supplied oxygen gas to form a minimum cross-sectional area, and is connected to the throat portion 17 and has an inner diameter connected to the inner diameter of the throat portion 17. It has a hollow portion 18 formed in a larger cylindrical shape, and a Laval-shaped tapered portion 19 serving as a main flow path whose cross section gradually expands downward from the tip of the hollow portion 18 and reaches the nozzle tip. That is,
The entire nozzle has a configuration in which a hollow portion 18 having a step portion that is connected to the oxygen gas flow path at an intermediate position of the nozzle portion 14a in a non-smooth manner is provided. The shape of the hollow portion is not limited to the cylindrical shape, for example, symmetric or asymmetric with respect to the central axis of the lance 14 for blowing acid decarburization,
In addition, it is possible to arrange a plurality of depressions having a step in the oxygen gas flow path.

With such a structure of the nozzle portion 14a, the supplied oxygen gas is once compressed by the throat portion 17, and the compressed oxygen gas is formed at the entrance of the hollow portion 18 having a columnar shape. By expanding and compressing at the outlet portion where the cross section is narrowed, it is possible to impart a pulsating phenomenon that vibrates at a low frequency to the jet stream of the oxygen gas discharged from the tip of the lance 14 for blowing acid decarburization. Thereby, as shown in FIG. 1, the pulsation of this jet flow is propagated to the region D of the cavity of the molten steel surface 13 formed by the direct collision of the jet flow of oxygen gas, and the oxygen gas in the region D of the cavity This can promote and activate the reaction with carbon in the steel that comes into contact therewith. When supplying the oxygen gas to the lance 14 for blowing acid decarburization, the oxygen gas flow rate to be supplied to the throat portion 17 having the smallest flow path cross section is set to 50 to 2000 Nm ³ / hr / cm ² , whereby the oxygen gas is supplied. Can be more effectively pulsated.

Subsequently, a lance 20 for blowing acid decarburization, which is a modification of the lance 14 for blowing acid decarburization (an example of a lance for refining).
Will be described. This modified example has the same configuration except for the structure of the nozzle portion of the lance 14 for blowing acid decarburization in the embodiment.
Nozzle part 20a in lance 20 for blowing acid decarburization of modified example
As shown in FIG. 3, a straight structure 22 of a main flow path having a cylindrical cross section is provided at a nozzle tip (main flow path). That is, following the throat portion 23 where the gas flow path is narrowest, the hollow portion 21 having a step portion is connected, and the straight portion 22 is further connected thereto. A pulsation phenomenon can be imparted, the structure becomes simpler than the lance 14 for blowing acid decarburization, and the lance 14 can be manufactured at lower cost.

In this embodiment, the case where the gas to be blown is oxygen gas has been described.
Refining lance for decarburization, dephosphorization, desiliconization, degassing, etc. using oxygen gas, nitrogen gas, hydrogen gas, argon gas, carbon dioxide gas or a mixed gas consisting of these gases Can be.

FIGS. 5 and 6 are cross-sectional views showing Laval type and straight type nozzle portions 50a and 51a respectively applied to refining lances 50 and 51 belonging to the conventional type. As shown in FIG. 5, the nozzle portion 50a of the refining lance 50 has a throat portion 52 that is reduced in diameter in the discharge direction of the supplied oxygen gas to form a minimum cross-sectional area portion, and is disposed continuously from the throat portion 52. The diameter is expanded, and the inside thereof has a tapered portion 53 formed in a conical shape. In this case, since the oxygen gas that has passed through the throat portion 52 is continuously expanded as it is via the taper portion 53, the pulsation necessary for increasing the decarbonation efficiency and calming the splash ( Vibration) phenomenon cannot be imparted to oxygen gas. In the case of a refining lance 51 having a straight nozzle portion 51a in which the flow area of the oxygen gas is constant over the entire length as shown in FIG. Since there is no portion having a pulsation in the oxygen gas flow path, pulsation cannot be given to the oxygen gas as in the case of the refining lance 50 having the Laval nozzle. The cross-sectional area of the main channel of the straight nozzle portion 51a is set to be the same as the throat portion 52 of the Laval nozzle.

FIGS. 4A and 4B show the lance 14 for blowing acid decarburization according to the present embodiment (example) and the lances 50 and 51 for refining according to Conventional Examples 1 and 2, respectively. Dust in spray acid, splash frequency when applied,
And decarboxylation efficiency. In addition,
The frequency of dust and splash generation is set to 1.0 in the case of the smelting lance 50 using a Laval nozzle. In addition, the decarbonation efficiency is based on data obtained when oxidative decarburization refining to reduce the carbon concentration in steel from 0.15 wt% to 0.05 wt% in a 150-ton VOD furnace to obtain 16 wt% Cr steel. It is. As shown in the figure, the decarboxylation efficiencies when the lance 14 for blowing acid decarburization and the lances 50 and 51 for refining are applied are 65%, 45% and 25%, respectively.
, And the frequency of dust and splash was 0.1.
4, 1.0 and 0.7. Thus, the lances 50 and 51 of the conventional examples 1 and 2 in which the lance 14 for blowing acid decarburization of the present embodiment does not generate pulsation in any case.
It turns out that it is much better than that.

The embodiments of the present invention have been described above.
The present invention is not limited to these embodiments, and all changes in conditions without departing from the gist are within the scope of the present invention. For example, in the present embodiment, a single-hole type refining lance having one nozzle hole has been described. However, the present invention can also be applied to a porous type refining lance having a plurality of nozzle holes. . The present invention can be effectively applied not only to converter refining under atmospheric pressure but also to vacuum refining furnaces which perform refining under reduced pressure. Further, in the present invention, the hollow portion disposed at the intermediate position of the nozzle portion is disposed at the intermediate position between the throat portion and the main flow path, but the entire hollow portion is formed to have a tapered diameter. It may be provided in the middle of the main flow path or in the middle of the throat portion formed in a straight shape.

[0017]

According to the present invention, claim 1 and dependent claims 4 to
In the lance for refining described in 6, since a cavity is provided in a gas flow path at an intermediate position of the nozzle, it is possible to impart pulsation accompanying pressure fluctuation at the step to the gas passing through the cavity. The contact surface between the blown gas and the molten steel to be refined can be maintained in an active state. Furthermore, since refining can be performed with a minimum necessary gas amount, generation of dust and splash can be effectively suppressed. In the refining lances according to claims 2 and 3 and subordinate claims 4 to 6, a hollow portion having a step portion in the oxygen gas flow path is provided at an intermediate position of the nozzle portion. Pulsation is applied to the oxygen gas passing through the molten steel to activate the molten steel surface which is the contact surface between the oxygen gas blown onto the molten steel surface and the molten steel, thereby improving the decarbonation efficiency. Furthermore, since blowing acid can be performed with a minimum necessary amount of oxygen gas, generation of dust and splash can be suppressed at the same time.

In particular, in the lance for refining according to the third aspect, since a specific flow rate of oxygen gas is supplied to the throat portion, it is possible to effectively improve the decarbonation efficiency and suppress the splash. it can. In the lance for refining according to the fourth aspect, since the nozzle portion has a Laval shape in which the cross section of the main flow path expands downward, the nozzle portion has a supersonic speed formed by gas or oxygen gas discharged from the lance for refining. The region or the region where the flow velocity is close to the supersonic speed can be set to a predetermined range, the distance from the tip of the lance for refining to the molten steel surface can be increased, and the heat damage at the tip of the lance for refining can be reduced. When oxygen gas is used, a cavity of an appropriate size is formed on the molten steel surface, so that the decarbonation efficiency can be favorably maintained. In the lance for refining according to the fifth aspect, since the nozzle portion has a straight structure in which the cross section of the main flow path has a cylindrical shape, the area where the gas or oxygen gas discharged from the nozzle tip expands can be set large, When gas is used, the area of the cavity formed in the molten steel surface can be increased. In the lance for refining according to the sixth aspect, since the inner diameter of the hollow portion is formed in a cylindrical shape larger than the inner diameter of the throat portion to which the hollow portion is connected, production can be facilitated and uniformity can be achieved in the radial direction of the nozzle. A gas or oxygen gas flow having a wide spread can be formed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a converter facility to which a lance for refining according to an embodiment of the present invention is applied.

FIG. 2 is a sectional view of a nozzle portion of the refining lance.

FIG. 3 is a cross-sectional view of a modified example of a nozzle portion of the refining lance.

4 (a) and 4 (b) are graphs comparing dust, splash occurrence frequency, and decarbonation efficiency in blowing acid.

FIG. 5 is a cross-sectional view of a nozzle portion in a refining lance according to Conventional Example 1.

FIG. 6 is a cross-sectional view of a nozzle portion in a lance for refining according to Conventional Example 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Converter equipment 11 Molten steel 12 Converter 13 Molten steel surface 14 Lance for blowing acid decarburization (lance for refining) 14a Nozzle part 15 Refractory brick 16 Iron shell 17 Throat part 18 Hollow part 19 Taper part 20 Lance for blowing acid decarburization Refining lance) 20a Nozzle part 21 Cavity part 22 Straight structure 23 Throat part

Claims (6)

[Claims] 1. A refining lance which is used under atmospheric pressure or reduced pressure and blows gas at a high speed from a lower nozzle portion, wherein a hollow portion is provided in a flow path of the gas at an intermediate position of the nozzle portion. A lance for refining. 2. A lance for refining, which is used under atmospheric pressure or reduced pressure, and is used to blow oxygen gas onto a molten steel surface of a molten steel to be treated from a lower nozzle portion to oxidize and decarbonize carbon in the molten steel. 2. The refining lance according to claim 1, wherein a hollow having a step in the flow path of the oxygen gas is provided at an intermediate position of the nozzle. 3. The throat portion where the cross section of the flow path of the oxygen gas is minimum is 50 to 2000 Nm per unit area.
^3. The refining lance according to claim ² , wherein oxygen gas of ³ / hr / cm ² is supplied. 4. The refining lance according to claim 1, wherein the nozzle portion has a Laval shape in which a cross section of the main flow path expands downward. 5. The refining lance according to claim 1, wherein the nozzle portion has a straight structure in which a cross section of a main flow path has a cylindrical shape. 6. The refining lance according to claim 1, wherein the hollow portion is formed in a cylindrical shape having an inner diameter larger than an inner diameter of a throat portion to which the hollow portion is connected.