JP5544807B2 - Top blowing lance for refining and converter refining method - Google Patents

Description

  The present invention relates to a refining upper blow lance for blowing an oxidizing gas to hot metal in a converter and performing oxidative refining on the hot metal to produce molten steel, and a converter using the upper blow lance More specifically, the present invention relates to a refining top blowing lance and a converter refining method that can reduce the amount of metal in the furnace body while maintaining high decarbonation efficiency.

  In the decarburization and refining of hot metal in the converter, from the viewpoint of improving the productivity of the converter, the iron content that is scattered outside the furnace as dust etc. as the operation with increased oxygen gas supply flow rate per unit time is adopted. In addition, the amount of iron adhering to and depositing near the furnace wall and furnace opening is increasing. These iron contents are finally recovered and reused as an iron source. However, if this amount increases, the cost required for recovery increases and the converter operation rate decreases, so that converter removal occurs. This is one of the important issues to be solved in coal refining.

  For this reason, many studies and studies have been made in the past regarding the suppression of dust generation amount and metal adhesion amount in decarburization and refining in converters, and the dust generation mechanism is (1) bubble burst (spitting). Or, two theories have been proposed: the theory based on the phenomenon that granular iron scatters as the bubble breaks off, and (2) the theory based on fume (evaporation of iron). It is known that the generation ratio changes. Since the amount of metal adhesion to the furnace body increases in proportion to the generation of dust, the metal adhesion mechanism may be considered the same as the dust generation mechanism.

Many means for suppressing dust generation and metal adhesion have been proposed. For example, Patent Document 1 discloses a ratio De / between the outlet diameter (De; (cm)) and the throat diameter (Dt; (cm)) of at least one of the injection nozzles provided at the tip of the top blowing lance. Dt is a relational expression between the atmospheric pressure at the outlet of the nozzle (Pe; (kPa)) and the appropriate expansion pressure (Po; (kPa)) of the nozzle, that is, “De / Dt = 0.509 × (Pe / Po) ^{−5 / 14} × [1- (Pe / Po) ^2/7 ] ^-1/4 "using a molten iron refining lance, and the inlet pressure P of the nozzle and the appropriate expansion pressure Po A molten iron refining method is proposed in which the ratio is used as a range of “1.2 × Po ≦ P ≦ 2.0 × Po” or “P ≦ 0.8 × Po”.

  This technology reduces the energy of the oxygen gas jet by making the jet of oxygen gas jetted from the Laval nozzle type jet nozzle installed in the top blowing lance out of the proper expansion range, thereby reducing the bubble gas energy. This technology suppresses the generation of dust caused by bursts. However, although the generation of dust and metal adhesion is suppressed, the original effect of the Laval nozzle is that the oxygen gas jet flow from the injection nozzle is decelerated and the energy of the oxygen gas jet on the bath surface is reduced, resulting in a supersonic jet flow. Is reduced, the decarbonation efficiency is lowered, and the oxygen blowing time is increased.

Further, in Patent Document 2, in decarburization blowing using a converter having an upper bottom blowing function, quick lime powder having a CaCO ₃ content of 20% by mass or less is sprayed on the iron bath surface together with an upper blowing oxygen gas. It has been proposed to reduce the amount of dust generated.

This technology uses the heat of decomposition of CaCO ₃ to lower the temperature of the iron bath surface, especially the hot spot (position where the oxygen gas jet collides with the bath surface), and suppresses dust generation and metal adhesion due to fume. However, there is a problem that it is necessary to grind the quick lime to be added normally in a lump and to add equipment for spraying and adding quick lime powder, which increases the manufacturing cost.

Japanese Patent Laid-Open No. 9-209021 JP 2006-342370 A

  The present invention has been made in view of the above circumstances, and the object of the present invention is to maintain a high decarbonation efficiency in carrying out decarburization and refining of hot metal by blowing up an oxidizing gas in a furnace. An object is to provide an upper blowing lance for refining capable of reducing adhesion of metal to the body and a converter refining method using the upper blowing lance.

A refining top blow lance according to a first aspect of the present invention for solving the above-mentioned problem is a refining top blow lance provided with one or more spray nozzles for injecting an oxidizing gas at a lower end portion thereof. At least one of the injection nozzles has a throat at the inlet portion thereof, a divergent portion downstream of the throat, and a throat diameter (Dt; (mm)) and an outlet diameter of the divergent portion (De) ; (Mm)) satisfies the relationship of the following equation (1) with respect to the nozzle outlet atmospheric pressure (Pe; (kPa)) and the nozzle proper expansion pressure (Po; (kPa)), and from the throat diameter Also, the diameter of the divergent portion that is the connection site with the throat is larger, and the throat center line is the center line of the divergent portion so that the throat smoothly connects to the surface of the upper lance central axis side of the divergent portion. Against the center of the top blowing lance And a control gas capable of controlling the flow rate independently of the oxidizing gas supplied from the injection nozzle, on the wall surface opposite to the central axis side of the upper blowing lance of the upper spread lance. It has at least one control gas injection hole for supplying it during refining.
(De / Dt) ² = 0.259 × (Pe / Po) ^-5/7 × [1- (Pe / Po) ^2/7 ] ^-1/2 … (1)

  A converter refining method according to a second aspect of the invention uses the refining top blow lance described in the first aspect of the invention and supplies a predetermined amount of control gas from the control gas injection hole to the injection nozzle. The supply pressure (P) of the oxidizing gas is equivalent to the nozzle proper expansion pressure (Po), and the oxidizing gas is blown toward the hot metal in the converter to oxidize and remove carbon in the hot metal. It is.

A converter refining method according to a third aspect of the invention uses the refining top blow lance according to the first aspect of the invention, and the supply pressure (P) of the oxidizing gas to the injection nozzle is the nozzle proper expansion pressure (Po). When a constant amount of control gas is supplied from the control gas injection hole, the lance height of the upper blowing lance is set to a constant height (H ₀ ) toward the hot metal in the converter. When the oxidizing gas is blown and the supply pressure (P) of the oxidizing gas to the injection nozzle is lower than the nozzle proper expansion pressure (Po), the control gas flow rate supplied from the control gas injection hole is set to After reducing, the lance height of the upper blowing lance is reduced to H ₀ × P / Po, and an oxidizing gas is blown toward the hot metal in the converter to oxidize and remove carbon in the hot metal. It is what.

  According to the present invention, among the injection nozzles arranged at the tip of the upper blowing lance, at least one of the injection nozzles has a center line of the throat relative to the center line of the divergent portion of the injection nozzle on the central axis side of the upper blowing lance. The jet angle of the jet jetted from the jet nozzle is larger than the tilt angle of the jet nozzle, while the control gas jet hole is formed on the wall surface opposite to the central axis side of the upper blow lance of the divergent portion. Therefore, the control gas injected from the control gas injection hole causes the jet flow injected from the injection nozzle to be deflected toward the central axis side of the upper blowing lance, and therefore the supersonic speed is controlled by the control gas. The injection angle of the jet flow from the injection nozzle can be adjusted while maintaining the state, and as a result, it is possible to reduce the amount of metal that adheres to the converter furnace wall without reducing the decarbonation efficiency.

It is a figure which shows the result of having investigated the relationship between the metal adhesion amount index to a furnace wall, and a nozzle inclination angle. It is a figure which shows the result of having investigated the relationship between decarbonation efficiency and a nozzle inclination angle. It is a schematic sectional drawing of the top blowing lance which concerns on this invention. It is an enlarged view of the injection nozzle shown in FIG. It is a figure which shows the result of having investigated the deflection angle of the oxygen gas jet when changing the control gas flow volume from a control gas supply hole.

  Hereinafter, the present invention will be specifically described. First, the background to the present invention will be described.

  The present inventors have injected an oxygen gas jet from an upper blowing lance which affects the amount of metal adhering to the walls of the converter when oxygen gas is blown over the molten iron in the converter to decarburize and refine the molten iron. The influence of the angle was tested and examined using a high-frequency induction melting furnace with a capacity of 150 kg, which can blow an oxidizing gas from above and blow a stirring gas from the bottom of the furnace. Oxygen gas was used as the top blowing oxidizing gas, and argon gas was used as the bottom blowing stirring gas.

  As an experimental method, using an upper blowing lance in which three Laval nozzles are installed at equal intervals on the same circumference, the oxygen gas flow rate of the upper blowing is constant at 400 NL / min, and the lance height is constant at 69 mm. As a condition of the above, the inclination angle of the Laval nozzle (inclination angle of the nozzle with respect to the center axis of the upper blowing lance) is changed within a range of 9 to 19 °, and the mass of the metal sticking to the furnace wall after the experiment is measured, The effects of the nozzle tilt angle and the nozzle tilt angle on the decarbonation efficiency were investigated. The nozzle inclination angle is an angle formed by the center line of the nozzle and the central axis of the upper blowing lance, that is, the inclination angle of the nozzle with respect to the central axis of the upper blowing lance, and the lance height is the height of the upper blowing lance. It is the distance between the tip and the hot metal surface in a stationary state in the furnace.

  Here, the supply of oxygen gas started when the carbon concentration in the hot metal was 4.0% by mass and continued until the carbon concentration reached 0.05% by mass. In hot metal decarburization and refining, the carbon in the hot metal decreases with the progress of the decarburization reaction, and eventually becomes molten steel. However, it is complicated to distinguish between hot metal and molten steel. In the present invention, the molten iron and the molten steel are collectively indicated as molten iron.

  The used top blowing lance is composed of three Laval nozzles as spray nozzles arranged at equal intervals on the same circumference of the tip, and the Laval nozzle has a throat diameter (Dt) of 1.6 mm and a nozzle. Designed with an appropriate expansion pressure (Po) of 540 kPa and a nozzle outlet atmospheric pressure (Pe) of 101.3 kPa (1 atm), the outlet diameter (De) is 1.97 mm. During the experiment, the supply pressure (P) of oxygen gas was 545 kPa, which was equivalent to the nozzle proper expansion pressure (Po).

In the case of a Laval nozzle type injection nozzle, the throat diameter (Dt: (mm)), outlet diameter (De; (mm)), nozzle outlet atmospheric pressure (Pe; (kPa)), and nozzle proper The expansion pressure (Po; (kPa)) is designed in accordance with the following equation (1), and the throat diameter (Dt), the nozzle outlet atmospheric pressure (Pe), and the nozzle proper expansion pressure (Po) Once determined, the exit diameter (De) is determined automatically. Here, the nozzle outlet portion atmospheric pressure (Pe) is the atmospheric pressure outside the injection nozzle, and in the case of decarburization refining in the converter, it is the atmospheric pressure in the converter and is usually atmospheric pressure. (101.3 kPa).
(De / Dt) ² = 0.259 × (Pe / Po) ^-5/7 × [1- (Pe / Po) ^2/7 ] ^-1/2 … (1)
Usually, at the time of operation, the supply pressure (P) of the oxidizing gas is controlled to be equal to the nozzle proper expansion pressure (Po) or within a range of about ± 10 kPa. This is because, when the supply pressure (P) of the oxidizing gas is substantially the same as the nozzle proper expansion pressure (Po), the gas expands properly and a supersonic jet is obtained, whereas the oxidizing gas If the gas supply pressure (P) is different from the nozzle proper expansion pressure (Po) (whether it is too large or too small), proper gas expansion cannot be obtained at the injection nozzle, and the injected jet is decelerated. This is because the decarbonation efficiency decreases.

FIG. 1 shows the relationship between the metal adhesion amount index on the furnace wall and the nozzle inclination angle. Here, the metal adhesion amount index is defined by the following equation (2), and is a relative value based on the reference (= 1.0) when the nozzle inclination angle is 9 °.
Barium adhesion amount index = Barium adhesion amount / Barium adhesion amount when nozzle tilt angle is 9 ° (2)
As is clear from FIG. 1, it was found that under the same conditions other than the nozzle tilt angle of the top blowing lance, the metal adhesion amount index decreases as the nozzle tilt angle increases. This is presumably because as the nozzle tilt angle increases, the pressure at the time when the oxygen gas jet collides with the hot metal bath surface decreases, and the amount of metal scattering due to spitting decreases.

FIG. 2 is a graph showing the relationship between decarbonation efficiency and nozzle tilt angle. The decarbonation efficiency is defined by the following formula (3), and is the ratio (percentage) of oxygen gas spent for the decarburization reaction among the oxygen gas supplied from the top blowing lance. is there.
Decarbonation efficiency = (amount of oxygen spent for removing carbon in molten iron) x 100 / (amount of supplied oxygen) (3)
As shown in FIG. 2, it was found that the decarbonation efficiency shows a substantially constant value regardless of the nozzle tilt angle when the nozzle tilt angle is in the range of 9 to 19 °.

  Here, it should be noted that when the nozzle tilt angle is within a range of 9 to 19 ° under the condition that the oxygen gas jet from the top blowing lance is maintained at an appropriate expansion, the decarbonation is accompanied by an increase in the nozzle tilt angle. This means that the amount of metal on the furnace wall is reduced while maintaining efficiency.

  By the way, in the operation of a large converter at a steel works, operation with a constant lance height of the top blow lance is extremely rare. However, the actual situation is to use different blowing patterns with changing lance height. For this reason, an excessive increase in the nozzle tilt angle causes the oxygen gas jet to directly collide with the furnace wall refractory when the lance height is increased, and this may promote damage to the furnace wall refractory. The tilt angle is adopted. In other words, the nozzle tilt angle varies depending on the converter shape and the operation method, but generally, the angle of about 10 to 15 ° is almost adopted, and the same applies to the present invention.

  Therefore, the nozzle tilt angle can be increased in operation near the lower limit in the height control range of the upper blow lance, and conversely, the nozzle tilt angle can be decreased in operation near the upper limit in the height control range. An upper blowing lance having an injection nozzle is desired.

  One way to achieve this is to prepare several types of top blowing lances with different nozzle tilt angles and use them separately according to the converter operation. There is a problem that the production cost of the blow lance increases. Furthermore, in order to cope with the situation where the furnace wall refractory wears unevenly, it is necessary to change the nozzle inclination angle for each injection nozzle. In such a case, the above-described problem becomes more apparent.

  Therefore, a method for adjusting the injection angle of the oxygen gas jet regardless of the physical nozzle tilt angle was studied. As a result, the knowledge that the injection angle of the oxygen gas jet can be changed during operation by using the top blowing lance as shown in FIG. 3 was obtained.

  As shown in FIG. 3, the refining upper blow lance 1 of the present invention is composed of a quadruple pipe of an outer pipe 2, an intermediate pipe 3, an inner pipe 4 and an innermost pipe 5. , A plurality of injection nozzles 6 facing vertically downward in the vertical direction are arranged on the same circumference and at equal intervals. In the refining top blow lance 1 of the present invention, the injection nozzles 6 do not necessarily have to be arranged on the same circumference and at equal intervals, but may be arbitrary, but here, on the same circumference and A description will be given of the upper blowing lance 1 arranged at equal intervals.

  An enlarged view of the injection nozzle 6 is shown in FIG. 4 is a diagram showing the jet nozzle 6 on the left side as viewed in FIG. 3, FIG. 4 (A) is a view seen from the direction of the center line of the jet nozzle, and FIG. 4 (B) is the center line of the jet nozzle. It is sectional drawing which passes through.

As shown in FIG. 4, the injection nozzle 6 has a throat 7 at the inlet and a divergent portion 8 on the downstream side of the throat 7. The throat diameter (Dt; (mm)) and the outlet diameter (De; (mm)) of the divergent portion 8 are the nozzle outlet portion atmospheric pressure (Pe; (kPa)) and the nozzle proper expansion pressure (Po; (kPa)). On the other hand, the nozzle satisfies the relationship of the above formula (1). However, the diameter of the divergent portion 8 which is a connecting portion with the throat 7 is larger than the throat diameter (D t ), and a step is provided at a part of the boundary between the throat 7 and the divergent portion 8. In this case, the center line q of the throat 7 with respect to the center line p of the divergent part 8 is centered on the upper lance 1 so that the throat 7 is smoothly connected to the surface of the upper divergent part 8 on the upper blow lance central axis side. It is installed eccentrically on the shaft side. The center line p of the end spread portion 8 is inclined at an angle θ with respect to the center axis of the upper blowing lance 1. The angle θ is the nozzle tilt angle. In addition, the spreading angle of the end spreading part 8 shall be 10 degrees or less on one side.

  Further, at least one control gas injection hole 9 for supplying control gas is provided on the wall surface on the opposite side to the central axis side of the upper blowing lance 1 of the divergent portion 8. From the control gas supply hole 9, a control gas for controlling the direction and / or flow velocity of the oxygen gas jet injected from the injection nozzle 6 provided with the control gas supply hole 9 is injected. As the control gas, any kind of gas can be used, whether oxygen gas, nitrogen gas, air, or Ar gas.

  The inside of the innermost pipe 5 serves as a cooling water supply channel for cooling the upper blow lance 1, and the cooling water supplied from the upper end of the innermost pipe 5 passes through the innermost pipe 5. Then, it reaches the tip of the upper blowing lance 1, reverses at the tip, passes through the gap between the outer tube 2 and the middle tube 3, and is discharged from the drainage joint 10 provided on the upper portion of the upper blowing lance 1.

  The gap between the inner pipe 4 and the innermost pipe 5 serves as a supply flow path for oxygen gas to the injection nozzle 6, and is connected to the inner pipe 4 and the outermost pipe from an oxygen gas supply joint 11 provided at the upper part of the upper blowing lance 1. The oxygen gas supplied to the gap with the inner pipe 5 passes through the gap between the inner pipe 4 and the innermost pipe 5 and is jetted from the jet nozzle 6 into the converter. The injected gas becomes a subsonic to supersonic jet depending on its flow rate.

  A gap between the middle pipe 3 and the inner pipe 4 serves as a supply flow path for the control gas (Ar gas in this case) to the control gas supply hole 9, and the control gas provided at the upper portion of the upper blowing lance 1. The control gas supplied from the supply joint 12 to the gap between the intermediate pipe 3 and the inner pipe 4 passes through the gap between the intermediate pipe 3 and the inner pipe 4 and is injected from the control gas supply hole 6. Thus, the control gas supply path can be controlled independently of the refining oxygen gas supply path.

  The control gas supply hole 9 is a device for controlling the direction and / or flow velocity of the jet flow injected from the injection nozzle 6, and the injection direction from the control gas supply hole 9 is as shown in FIG. Since the upper blowing lance 1 is directed from the outer surface side to the central axis side, when the flow rate of the control gas is increased with respect to the flow rate of the refining oxygen gas, the jet flow of the oxygen gas injected from the injection nozzle 6 is increased. 1 is deflected to the central axis side, and the same effect as when the inclination angle θ of the injection nozzle 6 is reduced (close to the vertical direction) is exhibited. This effect disappears when the control gas is turned off.

  FIG. 5 shows the result of investigating the deflection angle of the oxygen gas jet from the injection nozzle 6 at that time while changing the flow rate of the control gas from the control gas supply hole 9 while keeping the flow rate of the refining oxygen gas constant. As shown in FIG. 5, the control gas flow rate required to deflect the oxygen gas jet flow from the injection nozzle 6 by 1 ° is about 1% by volume with respect to the oxygen gas flow rate from the injection nozzle 6 and is small. It was confirmed that it can be controlled.

  That is, if the decarburization refining is performed using the upper blowing lance 1 according to the present invention, the throat 7 is eccentric to the central axis side of the upper blowing lance 1 with respect to the divergent portion 8, so that the jet flow from the injection nozzle 6 is By deflecting toward the outer peripheral side of the upper blowing lance 1 with respect to the inclination angle θ, while supplying the control gas from the control gas supply hole 9, the jet flow from the injection nozzle 6 becomes higher than the inclination angle θ. As a result, it was confirmed that the oxygen gas jet flow from the injection nozzle 6 can be controlled at a wide injection angle, thereby suppressing the adhesion of the metal to the converter wall.

  The present invention has been made based on the above examination results, and the refining top blow lance according to the present invention is a refining top blow lance provided with one or more injection nozzles for injecting oxidizing gas at the lower end portion. At least one of the injection nozzles has a throat at an inlet portion thereof, a divergent portion on the downstream side of the throat, and a throat diameter (Dt; (mm)) and divergent extent. Outlet diameter (De; (mm)) satisfies the relationship of the above formula (1) with respect to the nozzle outlet atmospheric pressure (Pe; (kPa)) and the nozzle proper expansion pressure (Po; (kPa)). The diameter of the divergent part, which is a connection site with the throat, is larger than the throat diameter, and the throat is smoothly connected to the surface of the upper lance central axis side of the divergent part. The center line of The oxidizing gas supplied from the spray nozzle to the wall surface opposite to the central axis side of the upper blowing lance of the upper end lance is eccentric to the central axis side of the upper blowing lance with respect to the center line of It is characterized by having at least one control gas injection hole for supplying a control gas capable of independent flow control during refining.

In carrying out decarburization refining in a converter using the top blowing lance 1 according to the present invention configured as described above, after supplying a certain amount of control gas from the control gas injection hole 9, the injection is performed. The supply pressure (P) of the oxidizing gas to the nozzle 6 is set equal to the nozzle proper expansion pressure (Po), and the lance height of the top blowing lance 1 is set to a predetermined constant height (H ₀ ). The oxidizing gas is blown toward the hot metal to oxidize and remove carbon in the hot metal. During decarburization refining, when the supply pressure (P) of the oxidizing gas to the injection nozzle 6 is within the range equivalent to the nozzle proper expansion pressure (Po), the lance height is not changed and the condition is maintained and the degassing is performed. Continue charcoal refining. This lance height (H ₀ ) is a condition in which the amount of bare metal adhering to the converter wall is minimized depending on the proper expansion pressure (Po) of the nozzle, the inclination angle θ of the injection nozzle 6 and the number of injection nozzles 6 installed. Set below.

  In the decarburization and refining of hot metal in a converter, the decarbonization efficiency decreases as the carbon concentration in molten iron decreases at the end of decarburization and refining, and the oxidation reaction of molten iron becomes remarkable. In order to prevent this, at the end of decarburization refining, an operation for reducing the oxygen gas supply flow rate is generally performed.

Thus, when reducing the oxygen gas supply flow rate, as long as the same top blowing lance 1 is used, the supply pressure (P) of the oxidizing gas to the injection nozzle 6 must be reduced. The oxygen gas jet from the nozzle 6 deviates from the optimum expansion range, and the dynamic pressure of the oxygen gas jet on the molten iron surface decreases. The decrease in the dynamic pressure is a cause of delaying the decarburization reaction. In order to prevent this, the lance height of the top blowing lance 1 is set so that the supply pressure (P) of the oxidizing gas is equal to the nozzle proper expansion pressure (Po). It is made smaller than the lance height (H ₀ ) in the case of the equivalent case, and is reduced to H ₀ × P / Po as the supply pressure (P) decreases. By reducing the lance height, the collision point on the molten iron of the jet flow from the injection nozzle 6 moves to the center side of the converter and increases the amount of metal scattering. In order to prevent this metal scattering, When the lance height is reduced, the control gas flow rate supplied from the control gas injection hole 9 is set to be higher than the flow rate when the supply pressure (P) of the oxidizing gas is equal to the nozzle proper expansion pressure (Po). The deflection of the jet flow from the jet nozzle 6 is reduced. That is, the jet is directed toward the outer peripheral side of the upper blowing lance 1.

  By carrying out converter decarburization and refining in this way, it is possible to reduce the amount of bullion adhering to the walls of the converter without reducing the decarbonation efficiency. Not only is the cost required reduced, but the frequency of removal and recovery of bullion is reduced, and the operating rate of the converter can be increased accordingly, and decarburization and refining can be performed efficiently.

  In addition, when the top blowing lance 1 has a plurality of injection nozzles 6, even if only one of the plurality of injection nozzles 6 satisfies the above condition, the high level of decarbonation efficiency can be maintained and the dust generation rate can be reduced. Although a certain degree of reduction can be obtained, in order to enjoy the effects of the present invention, it is desirable that all the injection nozzles 6 satisfy the above conditions. In addition, as the oxidizing gas supplied from the top blowing lance 1, oxygen gas is generally used, but a mixed gas of oxygen gas and argon gas, oxygen-enriched air, or the like can also be used as the oxidizing gas. is there.

  The hot metal was decarburized and refined using an upper bottom blowing converter with a capacity of 250 tons (Example 1 of the present invention). The used top blowing lance has the same configuration as that of the top blowing lance shown in FIG. 3, and five injection nozzles having the same shape at the tip portion have a nozzle tilt angle of 13 ° with respect to the axis of the top blowing lance. The nozzles are arranged on a concentric circle at equal intervals. The throat diameter (Dt) of the injection nozzle is 46.0 mm and the outlet diameter (De) is 63.2 mm. These injection nozzles are designed with a nozzle proper expansion pressure (Po) of 0.87 MPa.

  Further, in each spray nozzle, the center line of the throat is arranged to be eccentric to the center axis side of the upper blown lance by 10 mm with respect to the center line of the divergent part, and Was provided with a control gas injection hole having a diameter of 12 mm on the opposite side.

The molten iron with a temperature of 1255 to 1280 ° C. that had been subjected to dephosphorization in advance was charged into the top-bottom blowing converter, and then oxygen was blown from the top blowing lance toward the hot metal bath surface while argon was blown from the bottom blowing tuyere. The gas was blown into the hot metal as a stirring gas. The composition of the hot metal used is shown in Table 1. At that time, quick lime was charged as a slagging agent from the furnace hopper, and decarburization refining was performed until the carbon concentration of the molten iron reached 0.05 mass%. The addition amount of quicklime was adjusted so that the basicity (mass% CaO / mass% SiO ₂ ) of the slag in the furnace was 2.5.

  The oxygen gas supply flow rate from the top blowing lance injection nozzle, the control argon gas flow rate from the control gas injection hole, and the bottom blown argon gas flow rate are as shown in Table 2 according to the carbon concentration in the molten iron. Set to. That is, during refining, the oxygen gas supply flow rate and the argon gas flow rate from the control gas injection hole were not changed, and the bottom blown argon gas flow rate was changed with the carbon concentration in the molten iron being 0.4% by mass. The lance height of the top blowing lance was fixed at 2.2 m.

  In addition, for comparison, the equipment and operation method are the same as those of the above-described Example 1 of the present invention, but decarburization refining was also performed in which the control gas from the control gas injection hole was stopped (Comparative Example 1). . Table 3 shows the operation conditions and the operation results.

  As is apparent from Table 3, the invention example 1 and the comparative example 1 had almost the same blowing time and metallurgical characteristics, but in the invention example 1, the metal in the vicinity of the furnace wall and the furnace mouth Was greatly reduced. In other words, it was confirmed that the iron yield in converter decarburization refining was significantly improved by applying the present invention. In addition, the metal adhesion amount index shown in Table 3 is a relative value when the comparative example 1 is set to 1.0.

  The hot metal was decarburized and refined using an upper bottom blowing converter with a capacity of 250 tons (Example 2 of the present invention). The used top blowing lance has the same configuration as that of the top blowing lance shown in FIG. 3, and five injection nozzles having the same shape at the tip portion have a nozzle tilt angle of 13 ° with respect to the axis of the top blowing lance. The nozzles are arranged on a concentric circle at equal intervals. The throat diameter (Dt) of the injection nozzle is 46.0 mm and the outlet diameter (De) is 63.2 mm. These injection nozzles are designed with a nozzle proper expansion pressure (Po) of 0.87 MPa.

  Further, in each spray nozzle, the center line of the throat is arranged to be eccentric to the center axis side of the upper blown lance by 10 mm with respect to the center line of the divergent part, and Was provided with a control gas injection hole having a diameter of 12 mm on the opposite side.

The molten iron with a temperature of 1255 to 1280 ° C. that had been subjected to dephosphorization in advance was charged into the top-bottom blowing converter, and then oxygen was blown from the top blowing lance toward the hot metal bath surface while argon was blown from the bottom blowing tuyere. The gas was blown into the hot metal as a stirring gas. Table 4 shows the composition of the hot metal used. At that time, quick lime was charged as a slagging agent from the furnace hopper, and decarburization refining was performed until the carbon concentration of the molten iron reached 0.05 mass%. The addition amount of quicklime was adjusted so that the basicity (mass% CaO / mass% SiO ₂ ) of the slag in the furnace was 2.5.

  The oxygen gas supply flow rate from the top blowing lance injection nozzle, the control argon gas flow rate from the control gas injection hole, and the bottom blown argon gas flow rate are as shown in Table 5 according to the carbon concentration in the molten iron. Set to. In other words, the lance height of the top blowing lance is decreased from 2.2 m to 1.8 m with the carbon concentration in the molten iron as 0.4% by mass, and at the same time, the oxygen gas supply flow rate and the argon from the control gas injection hole The gas flow rate was decreased, and conversely, the bottom blown argon gas flow rate was increased.

  For comparison, the equipment and the operation method are the same as those of the above-described Example 2 of the present invention, but decarburization and refining was performed in which the control gas from the control gas injection hole was stopped (Comparative Example 2). . Table 6 shows the operation conditions and the operation results.

  As is clear from Table 6, in Example 2 and Comparative Example 2, the blowing time and metallurgical characteristics were almost the same, but in Example 2 of the present invention, the metal in the vicinity of the furnace wall and the furnace port was adhered. Was greatly reduced. In other words, it was confirmed that the iron yield in converter decarburization refining was significantly improved by applying the present invention. In addition, the metal adhesion amount index shown in Table 6 is a relative value when Comparative Example 2 is set to 1.0.

DESCRIPTION OF SYMBOLS 1 Top blowing lance 2 Outer pipe 3 Middle pipe 4 Inner pipe 5 Innermost pipe 6 Injection nozzle 7 Throat 8 End-spreading part 9 Control gas injection hole 10 Drainage joint 11 Oxygen gas supply joint 12 Control gas supply joint

Claims (3)

An upper blowing lance for refining provided with one or more injection nozzles for injecting oxidizing gas at the lower end,
At least one of the injection nozzles has a throat at an inlet portion thereof, a divergent portion on the downstream side of the throat, and a throat diameter (Dt; (mm)) and an output of the divergent portion. The diameter (De; (mm)) satisfies the relationship of the following formula (1) with respect to the nozzle outlet atmospheric pressure (Pe; (kPa)) and the nozzle proper expansion pressure (Po; (kPa)).
The diameter of the divergent portion, which is the connecting portion with the throat, is larger than the throat diameter, and the throat centerline diverges so that the throat smoothly connects to the surface of the upper lance center axis side of the divergent portion. Eccentric to the center axis side of the top blowing lance with respect to the center line of the part,
And, on the lance wall opposite to the central axis side of the flared portion, independently of the oxidizing gas supplied from the injection nozzle to supply a possible control gas flow control during refining And having at least one control gas injection hole for deflecting the oxidizing gas injected from the injection nozzle toward the central axis side of the upper blowing lance opposite to the control gas supply side. Characteristic top blow lance for refining.
(De / Dt) ² = 0.259 × (Pe / Po) ^-5/7 × [1- (Pe / Po) ^2/7 ] ^-1/2 … (1)   The refining top blow lance according to claim 1, and after supplying a predetermined amount of control gas from the control gas injection hole, supply pressure (P) of oxidizing gas to the injection nozzle is set to the nozzle. A converter refining method characterized by oxidizing and removing carbon in hot metal by blowing an oxidizing gas toward the hot metal in the converter as an equivalent expansion pressure (Po). An upper blowing lance for refining provided with one or more injection nozzles for injecting oxidizing gas at the lower end,
At least one of the injection nozzles has a throat at an inlet portion thereof, a divergent portion on the downstream side of the throat, and a throat diameter (Dt; (mm)) and an output of the divergent portion. The diameter (De; (mm)) satisfies the relationship of the following formula (1) with respect to the nozzle outlet atmospheric pressure (Pe; (kPa)) and the nozzle proper expansion pressure (Po; (kPa)).
The diameter of the divergent portion, which is the connecting portion with the throat, is larger than the throat diameter, and the throat centerline diverges so that the throat smoothly connects to the surface of the upper lance center axis side of the divergent portion. Eccentric to the center axis side of the top blowing lance with respect to the center line of the part,
In addition, a control gas whose flow rate can be controlled independently of the oxidizing gas supplied from the injection nozzle is supplied to the wall surface on the side opposite to the central axis side of the upper blow lance of the divergent portion during refining. When a refining top blowing lance having at least one control gas injection hole is used and the supply pressure (P) of the oxidizing gas to the injection nozzle is equal to the nozzle proper expansion pressure (Po) After supplying a certain amount of control gas from the control gas injection hole, the lance height of the upper blow lance is set to a constant height (H ₀ ) and an oxidizing gas is sprayed toward the hot metal in the converter. When the supply pressure (P) of the oxidizing gas to the injection nozzle is lower than the nozzle proper expansion pressure (Po), the flow rate of the control gas supplied from the control gas injection hole is decreased. , The lance height of the upper blowing lance is H ₀ × A converter refining method characterized by reducing P / Po and blowing an oxidizing gas toward hot metal in the converter to oxidize and remove carbon in the hot metal.
(De / Dt) ² = 0.259 × (Pe / Po) ^-5/7 × [1- (Pe / Po) ^2/7 ] ^-1/2 … (1)

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