JP2019002045A - Top blown lance for refining and method for refining molten iron - Google Patents

Abstract

To provide a top blown lance for refining in which a molten iron is subjected to oxidizing refining by blowing an oxygen gas for refining and a flux for refining onto a bath surface of the molten iron contained in a converter furnace, and which can prevent bullion insertion into a lance nozzle provided at a top end of the top blown lance and promote the slagging of the flux for refining.SOLUTION: A top blown lance 3 for refining has only a main hole nozzle 33 in the vertically downward direction or obliquely downward direction at a tip of the top blown lance, and has an oxygen gas supply passage 40 for supplying an oxygen gas for refining and a flux supply passage 41 for supplying a flux for refining together with a carrier gas separately in the top blown lance. The top blown lance for refining is constituted so that the oxygen gas supply passage and the flux supply passage merge inside the top blown lance, and the oxygen gas for refining and the flux for refining are simultaneously ejected from the main hole nozzle.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a refining top blowing lance for performing refining oxidation of hot metal by spraying a refining oxygen gas and a refining flux on a bath surface of the hot metal accommodated in a converter, and refining of hot metal using the same. Regarding the method.

  In recent years, in order to reduce the basic unit of refining flux such as CaO dephosphorization refining agent, refining oxygen gas and refining flux are sprayed on the bath surface of the hot metal accommodated in the converter to dephosphorize the hot metal Methods for performing oxidative refining such as decarburization and decarburization are widely used.

  For example, Patent Document 1 discloses a refining process in which fuel gas, oxygen gas, and a refining flux can be simultaneously ejected independently of a main hole nozzle for ejecting oxygen gas and a supply flow path for oxygen gas ejected from the main hole nozzle. An upper blowing lance for refining having a sub-hole nozzle for supplying a magnetic flux has been proposed.

  According to Patent Document 1, the refining flux is heated by a flame formed in the sub-hole nozzle, so that hatching is promoted and the hot metal can be efficiently dephosphorized.

  Patent Document 2 discloses a first flow path for supplying a refining flux together with a carrier gas, a second flow path that is disposed around the first flow path and supplies a refining oxygen gas, A sub-hole nozzle (center hole nozzle) disposed at the center of the lance tip below the first flow path, and a plurality of main hole nozzles disposed at the tip of the lance connected to the second flow path. In the upper blow lance for blowing the refining flux and the refining oxygen gas to the hot metal bath surface, provided with an opening for communicating the first flow path and the second flow path directly above the sub-hole nozzle. A refining top blow lance is disclosed.

  According to Patent Document 2, even if the top blowing of the refining flux is stopped and the transfer gas is stopped, the refining oxygen gas is ejected from the sub-hole nozzle through the opening. It is said that it is possible to avoid placing the metal in the sub-hole nozzle.

Japanese Patent Laid-Open No. 11-80825 JP 2014-208866 A

  However, the above prior art has the following problems.

  That is, in Patent Document 1, the refining flux is ejected from the sub-hole nozzle independent of the refining oxygen gas supply flow path, and the flow rate of the refining flux transport gas is reduced or stopped. In this case, the hot metal in the converter that has been scattered enters the inside of the sub-hole nozzle and closes the sub-hole nozzle. In the worst case, the next refining cannot be performed. In general, the scattered hot metal entering the inside of a nozzle (referred to as a “lance nozzle”) at the tip of the top blowing lance is expressed as “a metal is inserted”.

  Patent Document 2 states that by providing an opening directly above the sub-hole nozzle, the refining oxygen gas is ejected from the sub-hole nozzle when the transport gas is lowered, thereby solving the problem of metal insertion. Yes. However, when a lance nozzle causes a bullion to be inserted, it can be a major operational and safety problem. Patent Document 2 has an opening right above the sub-hole nozzle, but the area of the opening is not sufficiently large, and Patent Document 2 is not sufficient in terms of completely preventing the metal from being inserted. There is a need to further reduce the risk of money.

  Patent Document 2 is a technique in which a refining flux is ejected mainly from a sub-hole nozzle, separately from the refining oxygen gas, and a collision surface of the refining oxygen gas with the hot metal bath surface (referred to as “fire point”). ) The flux for refining sprayed on is small. In the dephosphorization treatment of the hot metal in the converter, there is a basic problem that the blowing time is short and sufficient refining flux cannot be obtained. There is a problem that the dephosphorization reaction is delayed due to the delay and the dephosphorization treatment of the hot metal. In addition, a hot spot is high temperature, and hatching of the refining flux is accelerated | stimulated by adding the refining flux to a fire point.

  The present invention has been made in view of the above circumstances, and the object of the present invention is for refining in which the refining oxygen gas and the refining flux are sprayed on the bath surface of the hot metal accommodated in the converter to perform the refining of the hot metal by oxidation. For top blowing lances, a top blowing lance for refining that can reliably prevent metal squeezing into the lance nozzle provided at the top of the top blowing lance and promote the hatching of the refining flux is provided. It is to be. Another object of the present invention is to provide a hot metal refining method using the top blowing lance for refining.

The gist of the present invention for solving the above problems is as follows.
[1] An upper blow lance for refining used for oxidation refining of hot metal accommodated in a converter, having only a main hole nozzle in a vertically downward or obliquely downward direction at a tip of the upper blow lance, The upper blow lance has a separate oxygen gas supply flow path for supplying the refining oxygen gas and a flux supply flow path for supplying the refining flux together with the transfer gas. A gas supply flow path and the flux supply flow path merge, and the refining oxygen gas and the refining flux are simultaneously ejected from the main hole nozzle. Blowing lance.
[2] The upper blow lance includes a lance body having a quadruple tube structure, and a lance tip connected to a lower end of the lance body to form a tip portion of the upper blow lance. The lower end of the pipe arranged at the innermost side of the main body does not reach the portion of the lance tip, thereby forming a joining position of the oxygen gas supply channel and the flux supply channel, and arranged at the innermost side. The distance L on the lance axis between the lower end position of the formed tube and the upper surface of the lance tip is larger than the inner diameter D (L> D) of the innermost tube (L> D), 1] The top blow lance for refining described in 1].
[3] Oxidative refining of the hot metal by using the upper blowing lance for refining as described in [1] or [2] above, and spraying a refining oxygen gas and a refining flux on the bath surface of the hot metal contained in the converter. A method for refining hot metal, characterized in that

  According to the present invention, the refining oxygen gas and the refining flux are merged inside the top blowing lance, and the refining flux is ejected together with the refining oxygen gas from the main hole nozzle. In addition, even when the refining flux is not ejected, the flow velocity of the gas ejected from the main hole nozzle is sufficiently high, which makes it possible to prevent the metal from being inserted into the main hole nozzle. Also, since the smelting flux is blown to the hot spot of the smelting oxygen gas ejected from the main hole nozzle, the hot spot has a high temperature and reacts with the smelting flux to promote the hatching of the smelting flux. And the hatching of the refining flux can be promoted.

It is a schematic sectional drawing of converter equipment. It is a general | schematic enlarged view of one example of the upper blowing lance for refining which concerns on this invention. It is a figure which shows the relationship between L / D and the ejection speed of the flux for refining. It is a figure which shows distribution of the carbon concentration in hot metal after a dephosphorization process, and the phosphorus concentration in the hot metal after a dephosphorization process by the example of this invention, and a comparative example. It is a figure which compares and shows the trouble incidence rate by a bullion with the example of this invention and a comparative example.

  Hereinafter, the present invention will be specifically described.

  The present invention is directed to a refining top blowing lance used in oxidation refining performed by blowing refining oxygen gas (industrial pure oxygen gas) and refining flux from a top blowing lance to hot metal contained in a converter. Yes. Currently, hot metal dephosphorization treatment and hot metal decarburization refining are performed as the oxidation refining, and the top blowing lance according to the present invention can be applied to both. In this case, in hot metal decarburization refining, either hot metal previously subjected to dephosphorization treatment as a preliminary treatment or hot metal that has not been dephosphorized may be used.

  The hot metal used in the present invention is a hot metal produced in a blast furnace, and this hot metal is received in a hot metal transfer container such as a hot metal ladle or a topped car and transferred to a converter for performing dephosphorization treatment and decarburization refining. To do. When dephosphorization is performed, in order to efficiently perform dephosphorization with a small amount of CaO-based dephosphorization agent, silicon in the hot metal is removed in advance before dephosphorization (“desiliconization of hot metal”). It is preferable to reduce the silicon content of the hot metal to 0.20% by mass or less, desirably 0.10% by mass or less. When the desiliconization process is performed, the slag generated during the desiliconization process is discharged before the dephosphorization process. However, even hot metal that has not been subjected to desiliconization treatment can be dephosphorized without problems except that the amount of CaO-based dephosphorization refining agent increases.

  Hereinafter, the present invention will be described with reference to the accompanying drawings, taking hot metal dephosphorization in a converter as an example. FIG. 1 is a schematic cross-sectional view of a converter facility used when performing oxidation refining such as dephosphorization treatment or decarburization refining on hot metal.

  As shown in FIG. 1, a converter facility 1 has an outer shell composed of an iron shell 4, and a converter 2 in which a refractory 5 is constructed inside the iron shell 4, and is inserted into the converter 2. And an upper blowing lance 3 that is movable in the vertical direction. A top 6 of the converter 2 is provided with a tap 6 for discharging the molten metal after refining (hot metal in the case of dephosphorization and molten steel in the case of decarburization refining). Is provided with a bottom blowing tuyere 7 for blowing a stirring gas 18 into the hot metal 15 in the furnace. The bottom blowing tuyere 7 is connected to a gas introduction pipe 8.

  An oxygen gas pipe 9 is connected to the top blowing lance 3, and oxygen gas (refining oxygen gas) supplied through the oxygen gas pipe 9 is converted from the tip of the top blowing lance 3 at an arbitrary flow rate. 2 is sprayed onto the bath surface of the hot metal 15 accommodated in the interior of 2.

  The top blowing lance 3 is connected to a dispenser 11 that contains a refining flux 17 such as a CaO-based dephosphorizing refining agent via a transfer pipe 19, while the dispenser 11 has an oxygen gas pipe 9. The oxygen gas pipe 9A and the nitrogen gas pipe 10 branched from are connected. That is, the oxygen gas supplied from the oxygen gas pipe 9A to the dispenser 11 or the nitrogen gas supplied from the nitrogen gas pipe 10 to the dispenser 11 functions as a transport gas for the refining flux 17 accommodated in the dispenser 11. The refining flux 17 accommodated in 11 is supplied to the upper blowing lance 3 via the transfer pipe 19, from the tip of the upper blowing lance 3 toward the bath surface of the hot metal 15 accommodated in the converter 2. It is designed to be sprayed (also called “projection”).

  The oxygen gas pipe 9 is provided with a flow rate adjusting valve 12, the oxygen gas pipe 9 A is provided with a flow rate adjusting valve 13, and the nitrogen gas pipe 10 is provided with a flow rate adjusting valve 14, and the top blowing lance 3 Thus, oxygen gas or nitrogen gas can be supplied as a transfer gas at an arbitrary flow rate via the dispenser 11 while supplying oxygen gas into the furnace at an arbitrary flow rate.

  Further, the oxygen gas pipe 9A and the nitrogen gas pipe 10 are connected to a bypass pipe 20 connected to the transfer pipe 19, and a shutoff valve 21 installed in the nitrogen gas pipe 10 after joining the oxygen gas pipe 9A and The shutoff valve 22 installed in the bypass pipe 20 is configured so that only oxygen gas or nitrogen gas can be supplied to the upper blowing lance 3 without going through the dispenser 11. In this case, instead of nitrogen gas, various gases such as argon gas and carbon dioxide can be used as the carrier gas.

  Although not shown, the upper blowing lance 3 is connected to a cooling water supply pipe and a drain pipe that circulate in the upper blowing lance 3 to cool the upper blowing lance 3.

  FIG. 2 shows a schematic enlarged view of an example of the upper blowing lance 3 shown in FIG. 2A is a schematic vertical sectional view of the upper blowing lance, and FIG. 2B is a schematic view of the upper blowing lance as viewed from below. In addition, although the top blowing lance 3 illustrated below is a typical example, the shape, size, number, position, etc. of each part (nozzle, path, etc.) are not limited to this. That is, in order to properly realize the purpose of each part, a structure can be designed according to an actual use environment with reference to a known technique.

  As shown in FIG. 2, the upper blow lance 3 according to the present invention is a lance that forms a cylindrical lance main body 31 and a tip portion of the upper blow lance 3 connected to the lower end of the lance main body 31 by welding or the like. Chip 32. The lance body 31 has a quadruple pipe structure in which four types of concentric steel pipes, that is, an outer pipe 34, a partition pipe 35, an inner pipe 36, and an innermost pipe 37, are arranged, of which an outer pipe 34, a partition pipe 35, and The inner tube 36 is connected to the copper lance tip 32. The lance tip 32 is provided with a plurality of (five in FIG. 2) main hole nozzles 33 whose discharge direction is a vertically oblique downward direction.

  The main hole nozzle 33 is a refining oxygen gas alone, a mixture of a refining oxygen gas, a refining flux 17 and a transport gas, or a mixed gas of a refining oxygen gas and a transport gas. It is a lance nozzle for spraying on the bath surface of the hot metal 15 in the converter. Only the main hole nozzle 33 is installed in the lance tip 32, and no other lance nozzle is installed. In FIG. 2, the main hole nozzles 33 are all in the vertically oblique downward direction. However, even if the main hole nozzles in the vertically downward direction are installed at the center of the lance tip 32, that is, the axial center position of the upper blow lance 3. Good.

  A gap between the inner pipe 36 and the innermost pipe 37 serves as an oxygen gas supply passage 40 for supplying a refining oxygen gas, and is introduced into the inner pipe 36 from an oxygen gas pipe 9 connected to the upper blowing lance 3. The refined oxygen gas passes through the oxygen gas supply channel 40 to reach the main hole nozzle 33 and is ejected from the main hole nozzle 33.

  The inside of the innermost pipe 37 is a flux supply passage 41 that supplies the refining flux 17 together with the carrier gas, and is transferred from the transfer pipe 19 connected to the upper blow lance 3 to the inside of the innermost pipe 37. The refining flux 17 introduced together with the gas descends inside the upper blowing lance 3 through the flux supply channel 41. However, the lower end of the innermost tube 37 does not reach the portion of the lance tip 32, and the merging position of the oxygen gas supply channel 40 and the flux supply channel 41 that are separate up to the lower end of the innermost tube 37 is the same. The innermost tube 37 is formed at the lower end. In other words, the refining flux 17 supplied through the flux supply channel 41 merges with the refining oxygen gas supplied through the oxygen gas supply channel 40 at the lower end of the innermost pipe 37, and the refining oxygen gas. And the refining flux 17 are ejected from the main hole nozzle 33 at the same time.

  The gap between the partition pipe 35 and the inner pipe 36 serves as a cooling water introduction passage 39 for cooling the upper blowing lance 3, and the gap between the outer pipe 34 and the partition pipe 35 is A cooling water discharge passage 38 for cooling water for cooling the blowing lance 3 is provided. Cooling water supplied from a water supply pipe (not shown) connected to the top blowing lance 3 reaches the site of the lance tip 32 through the cooling water introduction flow path 39 and is inverted at the site of the lance tip 32 to be cooled. It is discharged from a drainage pipe (not shown) connected to the upper blowing lance 3 through the discharge channel 38. The water supply / drainage path may be reversed.

  In the upper blow lance 3 according to the present invention, as shown in FIG. 2, when the distance on the lance axis between the lower end position of the innermost tube 37 and the upper surface of the lance tip 32 is defined as the distance L, the distance L is It is preferable to adjust the lower end position of the innermost tube 37 according to the inner diameter D of the innermost tube 37 so as to be larger than the inner diameter D of the innermost tube 37 (L> D). Here, the ratio between the distance L and the inner diameter D of the innermost tube 37 is defined as L / D.

  If a main hole nozzle in the vertically downward direction (hereinafter referred to as a “center position main hole nozzle”) is installed at the axial center position of the upper blow lance 3, if the L / D is small, the refining The mixing of the oxygen gas and the refining flux 17 is small, the pressure difference between the gas pressure in the oxygen gas supply channel 40 and the gas pressure in the flux supply channel 41 is maintained, and the flow rate of the jet flow of the refining flux 17 ( m / s) provides the desired flow rate. However, in this case, the refining flux 17 is mainly ejected from the central position main hole nozzle, and the refining flux 17 is hardly ejected from the other main hole nozzles. It becomes impossible to distribute and supply. That is, it becomes difficult to promote a refining reaction such as a dephosphorization reaction by the refining flux 17.

  On the other hand, when the central position main hole nozzle is not installed, if the L / D is small, the refining oxygen gas and the refining flux 17 cannot be smoothly joined, and the refining flux 17 cannot be ejected. There is a fear.

  Therefore, in the present invention, it is preferable to set the interval L larger than the inner diameter D of the innermost tube 37 (L> D) regardless of the presence or absence of the center position main hole nozzle. By satisfying L> D, the refining flux 17 can be ejected almost uniformly from all the main hole nozzles 33, and the metal insertion of the lance nozzles can also be prevented. Further, the refining oxygen gas and the refining flux 17 can be smoothly merged.

  However, when the top blow lance 3 according to the present invention is used, the gas pressure in the flux supply passage 41 is changed to the oxygen gas supply flow in order to ensure that the refining flux 17 is ejected from the main hole nozzle 33. It is necessary to make it higher than the gas pressure in the passage 40. If the gas pressure in the oxygen gas supply channel 40 is higher than the gas pressure in the flux supply channel 41, it is possible that the refining oxygen gas is much larger than the transport gas of the refining flux 17. Thus, there is a possibility that the gas ejection from the flux supply channel 41 is inhibited, that is, the ejection of the refining flux 17 is inhibited.

  In FIG. 3, when the difference between the gas pressure in the flux supply passage 41 and the gas pressure in the oxygen gas supply passage 40 is constant under the condition that the central position main hole nozzle is not installed, the L / D The result of investigating the relationship between L / D and the ejection speed of the refining flux 17 (= the mass of the refining flux ejected from the main hole nozzle 33 per unit time) is shown. The flux ejection speed (−) on the vertical axis is obtained by dividing the ejection speed (kg / min) of the refining flux 17 by the ejection speed (kg / min) of the refining flux 17 under the condition of L / D = 40. It is the value.

  As shown in FIG. 3, when L / D is less than 15, the ejection speed of the refining flux 17 is larger than the ejection speed of the refining flux 17 when L / D is 15 or more. That is, when L> D and L / D is less than 15, the refining flux 17 can be ejected almost uniformly from all the main hole nozzles 33 at the tip of the lance, and the ejection speed of the refining flux 17 (kg / kg) min) is larger than when L / D is 15 or more. Therefore, it is also suitable for increasing the amount of refining flux 17 added per hour.

  As shown in FIG. 2, the main hole nozzle 33 has a so-called Laval nozzle shape in which the cross section expands toward the tip, but may have a straight shape. Further, there are no particular restrictions on the number and diameter of the main hole nozzle 33, but due to restrictions such as the supply gas pressure to the top blowing lance 3, it is inevitably necessary to install the refining oxygen gas from the required supply amount. Since the number and the aperture are determined, they should be set within a range that satisfies them.

As the refining flux 17, all known (or foreseeable) solid substances that are introduced in order to efficiently realize the above-described oxidative refining can be applied. For example, in addition to the above CaO-based dephosphorizing refining agent (quick lime (CaO), limestone (CaCO ₃ ), dolomite (CaCO ₃ .MgCO ₃ ), decarburized slag, secondary refining slag), iron ore, mill scale, etc. Iron oxide powder, raw materials for slag (such as silica (SiO ₂ ), brick waste containing magnesium oxide, etc.), hatching accelerator (fluorite (CaF ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O) ₃ ) etc.) etc. are mentioned. Normally, at least a CaO-based dephosphorization refining agent is supplied as the refining flux 17. A mixture of limestone, limestone, and dolomite mixed with fluorite or aluminum oxide under the condition that the CaO content is 50% by mass or more can also be used as a CaO-based dephosphorizing agent.

  In the above description, the gap between the inner tube 36 and the innermost tube 37 is the oxygen gas supply channel 40, and the inside of the innermost tube 37 is the flux supply channel 41. The gap may be the flux supply channel 41 and the innermost pipe 37 may be the oxygen gas supply channel 40.

  Hereinafter, the refining method of the hot metal 15 in the converter equipment 1 provided with the top blowing lance 3 according to the present invention configured as described above will be described. As oxidation refining of hot metal 15, dephosphorization treatment of hot metal 15 and decarburization refining of hot metal 15 are currently performed, and since the refining methods of both are almost the same, here, dephosphorization treatment of hot metal 15 is performed. This will be described as an example.

  First, the hot metal 15 is charged into the converter 2. After the hot metal 15 is charged, a cold iron source such as iron scrap is charged into the converter 2 as necessary. Thereafter, while blowing argon gas or nitrogen gas as the stirring gas 18 from the bottom blowing tuyere 7, refining oxygen gas is supplied from the main hole nozzle 33 of the upper blowing lance 3 arranged at a predetermined position above the hot metal 15 in the converter. Spray the hot metal 15 on the bath surface. At the same time or after the spraying of the oxygen gas for refining to the hot metal 15, a refining flux 17 is introduced into the upper blowing lance 3 together with the carrier gas, and the refining flux 17 is refined from the main hole nozzle 33 of the upper blowing lance 3. Spray the hot metal bath surface with oxygen gas. As the refining flux 17, the above-mentioned CaO-based dephosphorizing refining agent is optimal.

The supplied refining oxygen gas reacts with a part of the carbon in the hot metal, and a decarburization reaction (C + O → CO) occurs at a fire point (a surface where the refining oxygen gas collides with the hot metal bath surface). Further, when the hot metal 15 contains silicon, desiliconization reaction (Si + 2O → SiO ₂ ) also occurs at the same time. In addition, an iron oxidation reaction (Fe + O → FeO) occurs at the fire point.

The refining flux 17 containing the CaO-based dephosphorizing refining agent ejected from the main hole nozzle 33 is sprayed to the fire point together with the refining oxygen gas. Since the hot spot is a high temperature and where FeO is generated, the refining flux 17 is heated and reacts with FeO to hatch. Further, when the desiliconization reaction occurs, the refining flux 17 reacts with the SiO ₂ generated by the desiliconization reaction and hatches. The hatched refining flux 17 forms slag 16 in the furnace.

When a decarburization reaction or a desiliconization reaction occurs, and the carbon concentration and silicon concentration of the hot metal 15 begin to decrease, the phosphorous oxide (P ₂ O ₅ ) is oxidized by the oxygen gas supplied with the phosphorus in the hot metal and the generated FeO. Is formed, and the phosphorous oxide (P ₂ O ₅ ) is absorbed by the slag 16 mainly composed of the CaO-based dephosphorizing refining agent, and the dephosphorization reaction represented by the following formula (1) proceeds.

2 [P] +5 (FeO) +3 (CaO) = (3CaO · P ₂ O ₅ ) +5 [Fe] (1)
Here, in the formula (1), [P] and [Fe] indicate components in the hot metal, and (FeO), (CaO) and (3CaO · P ₂ O ₅ ) indicate components in the slag.

The higher the basicity of the slag 16 in the furnace ((mass% CaO) / (mass% SiO ₂ )), the more the dephosphorization reaction of formula (1) proceeds, so the basicity of the slag 16 is 1.5 or more. Control. In the present invention, it is essential to blow the refining flux 17 from the top blowing lance 3, but when the refining flux 17 is supplied only from the top blowing lance 3, the basicity of the slag 16 at the initial stage of refining is secured to 1.5 or more. Since this may not be possible, a part of the planned addition amount of the refining flux 17 may be added over the chute from the hopper disposed above the converter 2 at the initial stage of refining.

  When the dephosphorization reaction proceeds and the phosphorus concentration in the hot metal 15 decreases to a predetermined value, the supply of oxygen gas from the top blowing lance 3 is stopped and the dephosphorization process is terminated. If a predetermined amount of the refining flux 17 is added to the furnace, the addition may be stopped during the dephosphorization process or may be added until the dephosphorization process is completed.

  Since the dephosphorization treatment and decarburization refining of the hot metal 15 in the converter 2 are substantially the same, the decarburization refining of the hot metal 15 may be performed according to the above dephosphorization treatment.

  As described above, according to the present invention, the refining oxygen gas and the refining flux 17 are merged inside the upper blowing lance 3 and the refining flux 17 is ejected from the main hole nozzle 33 together with the refining oxygen gas. Therefore, whether or not the refining flux 17 is ejected or when the refining flux 17 is not ejected, the flow velocity of the gas ejected from the main hole nozzle 33 is sufficiently high, thereby reducing the metal pouring at the main hole nozzle 33. This can be prevented beforehand. Further, since the refining flux 17 is sprayed on the hot spot of the refining oxygen gas ejected from the main hole nozzle 33, the hot spot has a high temperature and reacts with the refining flux 17 to promote the hatching of the refining flux 17. The concentration of iron oxide is also high, the hatching of the refining flux 17 is promoted, and the dephosphorization reaction of the hot metal 15 can be promoted.

  Further, according to the present invention, the refining flux 17 can be sprayed without installing a lance nozzle at the center of the lance tip 32, that is, the axial center position of the top lance 3. When the lance nozzle is not installed at the axial center position 3, the hole diameter of the lance nozzle must be made smaller in accordance with the lance nozzle at the axial position when designing the top blowing lance 3, and the innermost pipe There is an effect that it is possible to eliminate restrictions such as the need to provide a connection portion between the lance tip 32 and the contact 37.

  Using a 370-ton converter, the hot metal dephosphorization treatment was carried out using the top blowing lance according to the present invention having five main hole nozzles shown in FIG. 2 (example of the present invention). In the used top blow lance, the inner diameter of the innermost tube serving as a flux supply channel for supplying the refining flux is 66 mm, and L / D, which is the ratio of the distance L to the inner diameter D of the innermost tube, is 340. It was. As the refining flux, quick lime powder (average particle size of 1 mm or less) is used, as the gas for transporting quick lime powder, nitrogen gas is used, the gas pressure in the flux supply channel is changed to the gas in the oxygen gas supply channel. It was higher than the pressure. Further, argon gas was used as the stirring gas blown from the bottom blowing tuyere.

  The hot metal before the dephosphorization treatment was unified to a carbon concentration of 4.5 to 4.7 mass%, a phosphorus concentration of 0.11 to 0.12 mass%, and a hot metal temperature of 1300 to 1320 ° C. The hot metal phosphorus concentration was targeted to be 0.050% by mass or less.

  For comparison, a quadruple tube top blow lance having a sub-hole nozzle for ejecting quicklime powder in the center of the lance tip and having five main-hole nozzles around the sub-hole nozzle is used. The hot metal was dephosphorized (comparative example). In the upper blowing lance used in the comparative example, the sub-hole nozzle is connected to the innermost pipe, and the supply flow path for the quick lime powder and the supply flow path for the refining oxygen gas are independent of each other.

  The present invention example and the comparative example were carried out step by step, and in both cases, the phosphorus concentration in the hot metal after the dephosphorization treatment and the trouble occurrence rate due to the metal bar were investigated.

  FIG. 4 shows the distribution of the carbon concentration in the hot metal after the dephosphorization treatment and the phosphorus concentration in the hot metal after the dephosphorization treatment in comparison with the present invention example and the comparative example. Note that the vertical axis and the horizontal axis in FIG. 4 are dimensionless values obtained by dividing the phosphorus concentration and carbon concentration after dephosphorization by the average phosphorus concentration and average carbon in the comparative example.

  As shown in FIG. 4, in the present invention example, it was found that the phosphorus concentration in the hot metal after the dephosphorization treatment was reduced by about 20% compared to the comparative example. That is, it was confirmed that the hot metal dephosphorization reaction was promoted by using the top blowing lance of the present invention. This is considered to be because quick lime powder was added to the hot spot of the refining oxygen gas in the example of the present invention, and the hatching of quick lime powder was promoted.

  FIG. 5 shows the trouble occurrence rate due to the metal insert between the example of the present invention and the comparative example. The example of the present invention is the result of about 30000 charge, and the comparative example is the result of about 5000 charge. As shown in FIG. 5, it was confirmed that the trouble due to the metal bar can be completely prevented by using the top blowing lance of the present invention.

DESCRIPTION OF SYMBOLS 1 Converter equipment 2 Converter 3 Top blowing lance 4 Iron skin 5 Refractory 6 Outlet 7 Bottom blowing tuyere 8 Gas introduction pipe 9 Oxygen gas piping 10 Nitrogen gas piping 11 Dispenser 12 Flow control valve 13 Flow control valve 14 Flow control Valve 15 Hot metal 16 Slag 17 Refining flux 18 Stirring gas 19 Transfer pipe 20 Bypass pipe 21 Shut-off valve 22 Shut-off valve 31 Lance body 32 Lance tip 33 Main hole nozzle 34 Outer pipe 35 Partition pipe 36 Inner pipe 37 Inner pipe 38 Cooling water discharge passage 39 Cooling water introduction passage 40 Oxygen gas supply passage 41 Flux supply passage

Claims (3)

An upper blow lance for refining used for the oxidation refining of hot metal contained in a converter,
At the tip of the upper blowing lance, only having a main hole nozzle in a vertically downward or obliquely downward direction,
In the upper blowing lance, separately having an oxygen gas supply channel for supplying a refining oxygen gas and a flux supply channel for supplying a refining flux together with a carrier gas,
Inside the upper blowing lance, the oxygen gas supply channel and the flux supply channel merge,
A refining top blow lance, wherein the refining oxygen gas and the refining flux are simultaneously ejected from the main hole nozzle. The upper blowing lance comprises a lance body having a quadruple tube structure, and a lance tip that is connected to the lower end of the lance body to form the tip of the upper blowing lance.
The lowermost end of the pipe arranged at the innermost side of the lance main body of the quadruple tube structure does not reach the portion of the lance tip, thereby forming a merging position between the oxygen gas supply channel and the flux supply channel. And
A distance L on the lance axis between the lower end position of the innermost pipe and the upper surface of the lance tip is larger than an inner diameter D of the innermost pipe (L> D). The top blowing lance for refining according to claim 1.   Using the top blow lance for refining according to claim 1 or claim 2, the refining oxygen gas and the refining flux are sprayed on the bath surface of the hot metal accommodated in the converter to carry out the oxidation refining of the hot metal. A method for refining hot metal.

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