JP6658678B2 - Top blowing lance for refining and method for refining hot metal - Google Patents

Description

  The present invention relates to a refining upper blowing lance for oxidizing and refining hot metal by spraying a refining oxygen gas and a refining flux onto a bath surface of hot metal accommodated in a converter, and hot metal refining using the same. About the method.

  In recent years, in order to reduce the basic unit of flux for refining such as CaO-based dephosphorizing refining agent, oxygen gas for refining and flux for refining are sprayed on the bath surface of the hot metal stored in the converter to dephosphorize the hot metal. Oxidation smelting methods such as smelting and decarburization smelting are widely used.

  For example, Patent Literature 1 discloses a refining process that is independent of a main hole nozzle for ejecting oxygen gas and a supply flow path of oxygen gas ejected from the main hole nozzle, and that can simultaneously eject fuel gas, oxygen gas, and flux for refining. A refining upper blowing lance having a sub-hole nozzle for supplying a feed flux has been proposed.

  According to Patent Literature 1, refining flux is heated by a flame formed in a sub-hole nozzle, so that slagification is promoted and 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 arranged around the first flow path to supply a refining oxygen gas, A sub-hole nozzle (center hole nozzle) arranged at the center of the lance tip below the first flow path, and a plurality of main hole nozzles connected to the second flow path and arranged at the tip of the lance. In the provided upper blowing lance for blowing the refining flux and the refining oxygen gas onto the hot metal bath surface, an opening is provided immediately above the sub-hole nozzle for communicating the first flow path and the second flow path. A refining top blowing lance is disclosed.

  According to Patent Literature 2, even if the refining flux is stopped from being blown up and the carrier gas is stopped, the refining oxygen gas is ejected from the sub-hole nozzle through the opening. It is stated that it is possible to avoid inserting a metal into the sub-hole nozzle.

JP-A-11-80825 JP 2014-208866 A

  However, the above prior art has the following problems.

  That is, in Patent Literature 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 carrier gas decreases or stops. In this case, the hot metal in the converter that has scattered penetrates into the sub-hole nozzle to block the sub-hole nozzle, and in the worst case, a problem occurs that the next refining cannot be performed. In addition, the intrusion of the scattered hot metal into the inside of a nozzle (referred to as a “lance nozzle”) at the tip of the upper blowing lance is generally expressed as “injection of metal”.

  Patent Literature 2 discloses that by providing an opening directly above the sub-hole nozzle, when the carrier gas is reduced, refining oxygen gas is ejected from the sub-hole nozzle, which can solve the problem of ingot insertion. I have. However, if a metal bullion occurs at the lance nozzle, it may cause a serious trouble in operation and safety. Patent Literature 2 has an opening directly above the sub-hole nozzle. However, Patent Literature 2 cannot be said to be sufficient in that the area of the opening is not sufficiently large and a bullion is completely prevented. It is necessary to further reduce the risk of money.

  Patent Literature 2 discloses a technique in which a refining flux is ejected mainly from a sub-hole nozzle separately from a refining oxygen gas, and a collision surface of the refining oxygen gas with a molten iron bath surface (referred to as a “fire point”). There is little refining flux sprayed on). In the dephosphorization of hot metal in a converter, there is a basic problem that the blowing time is short and sufficient slagging of the refining flux cannot be obtained. There is a problem that the dephosphorization reaction is delayed by the dephosphorization treatment of the hot metal. The flash point is a high temperature, and the addition of the refining flux to the flash point promotes the smelting of the refining flux.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a refining apparatus for oxidizing and refining hot metal by blowing a refining oxygen gas and a refining flux onto a bath surface of hot metal accommodated in a converter. Provided is an upper blowing lance which can surely prevent a metal lance from being inserted into a lance nozzle provided at the tip of the upper blowing lance and can promote slagging of the refining flux. It is to be. Another object of the present invention is to provide a method for refining hot metal using the upper lance for refining.

The gist of the present invention for solving the above problems is as follows.
[1] An upper-blowing lance for refining used for oxidizing and refining hot metal housed in a converter, having only a vertically downward or obliquely downward main hole nozzle at the tip of the upper-blowing lance, Inside the upper blowing lance, an oxygen gas supply channel for supplying refining oxygen gas and a flux supply channel for supplying refining flux together with carrier gas are separately provided. A gas supply flow path and the flux supply flow path are merged, and the refining oxygen gas and the refining flux are simultaneously ejected from the main hole nozzle. Blowing lance.
[2] The upper blowing lance includes a lance main body having a four-tube structure, and a lance tip connected to a lower end of the lance main body to form a tip portion of the upper blowing lance. The lower end of the tube disposed on the innermost side of the main body does not reach the position of the lance tip, thereby forming a merging position between the oxygen gas supply flow path and the flux supply flow path, and disposed at the innermost position. Wherein the distance L on the lance axis between the lower end position of the pipe and the upper surface of the lance tip is larger than the inner diameter D of the innermost pipe (L> D). An upper blowing lance for refining according to 1).
[3] Oxidation refining of the hot metal by spraying a refining oxygen gas and a refining flux onto the bath surface of the hot metal accommodated in the converter using the refining top blowing lance according to the above [1] or [2]. A method for refining molten iron.

  According to the present invention, the refining oxygen gas and the refining flux are merged inside the upper blowing lance, and the refining flux is spouted together with the refining oxygen gas from the main hole nozzle. In addition, even when the refining flux is not ejected, the gas flow velocity of the ejected gas from the main hole nozzle is sufficiently high, so that it is possible to prevent the metal ingot at the main hole nozzle. In addition, since the refining flux is blown to the hot spot of the refining oxygen gas ejected from the main hole nozzle, the hot spot has a high temperature and the concentration of iron oxide which reacts with the refining flux to promote slagging of the refining flux. And the slagging of the refining flux can be promoted.

It is a schematic sectional drawing of converter equipment. It is a schematic enlarged view of an example of the upper lance for smelting concerning the present 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 the distribution of the carbon concentration in the hot metal after a dephosphorization process, and the distribution of the phosphorus concentration in a hot metal after a dephosphorization process in comparison with the example of this invention, and a comparative example. It is a figure which shows the trouble occurrence rate by a bullion in comparison with the present invention example and a comparative example.

  Hereinafter, the present invention will be described specifically.

  The present invention is directed to an upper blowing lance for refining used in oxidizing refining performed by blowing oxygen for refining (industrial pure oxygen gas) and flux for refining from a top blowing lance to hot metal housed in a converter. I have. As the oxidizing refining, dephosphorization treatment of hot metal and decarburization refining of hot metal are currently performed, and the upper blowing lance according to the present invention can be applied to any of them. In this case, in the decarburization refining of the hot metal, either the hot metal that has been subjected to the dephosphorization treatment as a preliminary treatment or the hot metal that has not been subjected to the dephosphorization treatment may be used.

  The hot metal used in the present invention is hot metal manufactured in a blast furnace, and the hot metal is received in a hot metal transfer container such as a hot metal ladle or a topped car and transported to a converter for performing dephosphorization and decarburization refining. I do. When performing the dephosphorization treatment, in order to efficiently perform the dephosphorization treatment using a small amount of the CaO-based dephosphorization refining agent, the silicon in the hot metal is removed in advance before the dephosphorization treatment ("Desiliconization treatment of the hot metal"). However, it is preferable to reduce the silicon content of the hot metal to 0.20% by mass or less, preferably 0.10% by mass or less. When the desiliconization treatment is performed, the slag generated during the desiliconization treatment is discharged before the dephosphorization treatment. However, even hot metal that has not been subjected to desiliconization can be dephosphorized without any problem except that the amount of the CaO-based dephosphorizing refining agent used increases.

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

  As shown in FIG. 1, the converter equipment 1 has an outer shell made of an iron shell 4, and a refractory 5 is installed inside the iron shell 4, and inserted into the converter 2. And an upper blowing lance 3 which is movable in the vertical direction. At the upper part of the converter 2, a tap hole 6 for discharging molten metal after refining (hot metal in the case of dephosphorization treatment, molten steel in the case of decarburizing refining) is provided. 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 upper blowing lance 3, and an oxygen gas (oxygen gas for refining) supplied through the oxygen gas pipe 9 is supplied to the converter from the tip of the upper blowing lance 3 at an arbitrary flow rate. The hot metal 15 housed in the interior 2 is sprayed on the bath surface.

  The upper blowing lance 3 is connected to a dispenser 11 containing a refining flux 17 such as a CaO-based dephosphorizing refining agent via a transfer pipe 19, while the dispenser 11 is connected to an oxygen gas pipe 9. An oxygen gas pipe 9A and a nitrogen gas pipe 10 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 carrier gas for the refining flux 17 contained in the dispenser 11, and The refining flux 17 accommodated in 11 is supplied to the upper blowing lance 3 via the transfer pipe 19, and is directed from the tip of the upper blowing lance 3 toward the bath surface of the hot metal 15 accommodated in the converter 2. It can be sprayed (also called "projection").

  The oxygen gas pipe 9 is provided with a flow rate control valve 12, the oxygen gas pipe 9A is provided with a flow rate control valve 13, and the nitrogen gas pipe 10 is provided with a flow rate control valve 14. The oxygen gas or the nitrogen gas can be supplied as a carrier gas at an arbitrary flow rate via the dispenser 11 while the oxygen gas is supplied into the furnace at an arbitrary flow rate from the furnace.

  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 the shutoff valve 21 installed in the nitrogen gas pipe 10 after merging with the oxygen gas pipe 9A. With the shut-off valve 22 installed in the bypass pipe 20, only the oxygen gas or the nitrogen gas can be supplied to the upper blowing lance 3 without passing through the dispenser 11. In this case, various gases such as argon gas and carbon dioxide gas can be used as the carrier gas instead of the nitrogen gas.

  Although not shown, the upper blowing lance 3 is connected to a water supply pipe and a drain pipe for cooling water that circulates inside the upper blowing lance 3 and cools the upper blowing lance 3.

  FIG. 2 is a schematic enlarged view of one example of the upper blowing lance 3 shown in FIG. FIG. 2A is a schematic longitudinal sectional view of the upper blowing lance, and FIG. 2B is a schematic view of the upper blowing lance viewed from below. Although the upper blowing lance 3 illustrated below is a typical example, the shape, size, number, position, and the like of each part (nozzle, path, and the like) are not limited thereto. That is, in order to appropriately realize the purpose of each part, the structure can be designed in accordance with the actual use environment with reference to a known technique.

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

  The main hole nozzle 33 is a single gas of the refining oxygen gas, or a mixture of the refining oxygen gas, the refining flux 17 and the carrier gas, or a mixed gas of the refining oxygen gas and the carrier gas. This is a lance nozzle for spraying the hot metal 15 in the converter on the bath surface. The lance tip 32 is provided with only the main hole nozzle 33, and other lance nozzles are not provided. In FIG. 2, the main hole nozzles 33 are all vertically obliquely downward, but the main hole nozzles in the vertical downward direction may be installed at the center of the lance tip 32, that is, at the axial position of the upper blowing lance 3. Good.

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

  The inside of the innermost tube 37 is a flux supply flow path 41 for supplying the refining flux 17 together with the carrier gas, and is used for transport from the transfer pipe 19 connected to the upper blowing lance 3 to the inside of the innermost tube 37. The refining flux 17 introduced together with the gas passes through the flux supply passage 41 and descends inside the upper blowing lance 3. However, the lower end of the innermost tube 37 does not reach the position of the lance tip 32, and the merging position of the oxygen gas supply flow path 40 and the flux supply flow path 41 which were separate up to the lower end of the innermost pipe 37 is determined. , Formed at the lower end of the innermost tube 37. In other words, the refining flux 17 supplied through the flux supply flow path 41 joins the refining oxygen gas supplied through the oxygen gas supply flow path 40 at the lower end of the innermost pipe 37, and the refining oxygen gas And the refining flux 17 are simultaneously ejected from the main hole nozzle 33.

  The gap between the partition pipe 35 and the inner pipe 36 is a cooling water introduction flow path 39 for cooling water 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 the cooling lance 3 is provided. The cooling water supplied from a water supply pipe (not shown) connected to the upper blowing lance 3 reaches the lance tip 32 through the cooling water introduction flow path 39, and is inverted at the lance tip 32 to be cooled. The water is discharged from a drain pipe (not shown) connected to the upper blowing lance 3 through the discharge passage 38. In addition, the path of the water supply and drainage may be reversed.

  In the upper blowing 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 that the inner diameter D becomes larger than the inner diameter D of the innermost tube 37 (L> D). Here, the ratio between the interval L and the inner diameter D of the innermost tube 37 is defined as L / D.

  Assuming that a vertically downward main hole nozzle (hereinafter, referred to as “center position main hole nozzle”) is installed at the axial center position of the upper blowing lance 3, if L / D is small, the refining The mixing between the oxygen gas and the flux 17 for refining is small, and the pressure difference between the gas pressure in the oxygen gas supply flow path 40 and the gas pressure in the flux supply flow path 41 is maintained. m / s), the desired flow rate can be obtained. However, in this case, the refining flux 17 is mainly ejected from the central position main hole nozzle, the ejection of the refining flux 17 from other main hole nozzles is small, and the refining flux 17 is discharged from the hot metal bath surface. Cannot be distributed and supplied. 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 provided, 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 jetted. There is a risk.

  Therefore, in the present invention, it is preferable that the interval L be larger than the inner diameter D of the innermost tube 37 (L> D) regardless of the presence or absence of the central position main hole nozzle. By setting L> D, the refining flux 17 can be almost uniformly ejected from all the main hole nozzles 33, and the lance nozzle can be prevented from being ingot. Further, the merging of the refining oxygen gas and the refining flux 17 can be performed smoothly.

  However, when the top blowing lance 3 according to the present invention is used, the gas pressure in the flux supply flow path 41 is reduced in order to ensure that the refining flux 17 is ejected from the main hole nozzle 33. It must be higher than the gas pressure in passage 40. When the gas pressure in the oxygen gas supply flow path 40 is higher than the gas pressure in the flux supply flow path 41, the refining oxygen gas is much larger than the carrier gas of the refining flux 17. Thus, gas ejection from the flux supply flow path 41 may be inhibited, that is, ejection of the refining flux 17 may be inhibited.

  FIG. 3 shows the L / D ratio under the condition that the main position main hole nozzle is not installed, and 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. 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 by changing. Note that 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. Value.

  As shown in FIG. 3, when the L / D is less than 15, the ejection speed of the refining flux 17 is higher than the ejection speed of the refining flux 17 when the L / D is 15 or more. That is, when L> D and L / D is less than 15, the refining flux 17 can be almost uniformly ejected 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 when it is desired to increase the amount of flux 17 for refining per hour.

  The main hole nozzle 33 has a so-called Laval nozzle shape in which the cross section increases toward the tip end as shown in FIG. 2, but may have a straight shape. There is no particular restriction on the number of holes or the diameter of the main hole nozzle 33, but the number of holes is inevitably determined based on the required supply amount of the refining oxygen gas due to the restriction on the supply gas pressure to the upper blowing lance 3. Since the number and the diameter are determined, they are set within a range satisfying these.

As the flux 17 for refining, all known (or foreseeable) solid substances that are introduced to efficiently realize the above-described oxidizing refining can be applied. For example, in addition to the above CaO-based dephosphorizing refining agents (quick lime (CaO), limestone (CaCO ₃ ), dolomite (CaCO ₃ .MgCO ₃ ), decarburized slag, secondary smelting slag), iron ore, mill scale, etc. Raw materials for iron oxide powder and slag (eg, silica stone (SiO ₂ ), brick waste containing magnesium oxide, etc.), slagging accelerators (fluorite (CaF ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O) ₃ ) etc.) and the like. Usually, at least a CaO-based dephosphorizing refining agent is supplied as the refining flux 17. A mixture of quicklime, 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 refining 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 used as the flux supply channel 41, and the inside of the innermost tube 37 may be used as the oxygen gas supply channel 40.

  Hereinafter, a method of refining the hot metal 15 in the converter equipment 1 provided with the upper blowing lance 3 according to the present invention configured as described above will be described. As the oxidizing and refining of the hot metal 15, the dephosphorizing treatment of the hot metal 15 and the decarburizing refining of the hot metal 15 are currently performed, and the refining methods of both are almost the same. 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. After that, while blowing argon gas or nitrogen gas as 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 disposed at a predetermined position above the hot metal 15 in the converter. Spray on the hot metal 15 bath surface. Simultaneously with or after blowing the refining oxygen gas onto 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. It is sprayed onto the hot metal bath together with the oxygen gas used. As the refining flux 17, the above CaO-based dephosphorizing refining agent is most suitable.

The supplied oxygen gas for refining 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 oxygen gas for refining collides with the hot metal bath surface). When the hot metal 15 contains silicon, a desiliconization reaction (Si + 2O → SiO ₂ ) occurs at the same time. At the fire point, an oxidation reaction of iron (Fe + O → FeO) occurs.

The refining flux 17 containing the CaO-based dephosphorizing refining agent ejected from the main hole nozzle 33 is blown to the ignition point together with the refining oxygen gas. Since the flash point is a high temperature and a place where FeO is generated, the refining flux 17 is heated and reacts with FeO to form slag. When a desiliconization reaction occurs, the refining flux 17 also reacts with SiO ₂ generated by the desiliconization reaction to form slag. The slag refined flux 17 forms a slag 16 in the furnace.

When a decarburization reaction or a desiliconization reaction occurs and the carbon concentration and the silicon concentration of the hot metal 15 start to decrease, the phosphorus in the hot metal is oxidized by the supplied oxygen gas and the generated FeO to form a phosphor oxide (P ₂ O ₅ ). Is generated, and this phosphorus oxide (P ₂ O ₅ ) is absorbed by the slag 16 containing a CaO-based dephosphorizing refining agent as a main component, 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 equation (1), [P] and [Fe] represent components in the hot metal, and (FeO), (CaO), and (3CaO · P ₂ O ₅ ) represent components in the slag.

The higher the basicity ((mass% CaO) / (mass% SiO ₂ )) of the slag 16 in the furnace is, the more the dephosphorization reaction of the formula (1) proceeds. Control. In the present invention, it is essential that the refining flux 17 is sprayed from the upper blowing lance 3. However, if the refining flux 17 is supplied only from the upper blowing lance 3, the basicity of the slag 16 at the initial stage of refining is secured to 1.5 or more. Since it may not be possible, at the beginning of the refining, a part of the expected addition amount of the refining flux 17 may be added via a chute from a hopper disposed above the converter 2 via a chute.

  When the dephosphorization reaction proceeds and the phosphorus concentration of the hot metal 15 decreases to a predetermined value, the supply of oxygen gas from the upper blowing lance 3 is stopped, and the dephosphorization treatment is terminated. Once a predetermined amount of the refining flux 17 has been added into the furnace, the addition may be stopped during the dephosphorization treatment or may be continued until the dephosphorization treatment is completed.

  Since the dephosphorization process and the 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 process.

  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, when the refining flux 17 is jetted or when the refining flux 17 is not jetted, the flow rate of the gas jetted from the main hole nozzle 33 is sufficiently high. It is possible to prevent it before it happens. In addition, since the refining flux 17 is blown to 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 slagging of the refining flux 17. Since the concentration of iron oxide is also high, slagging 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, at the axial center position of the upper blowing lance 3. When the lance nozzle is not installed at the axial position of the lance 3, the hole diameter of the lance nozzle must be reduced in accordance with the lance nozzle at the axial position when designing the upper blowing lance 3. There is an effect that restrictions such as the necessity of providing a connection portion between the lance tip 32 and the lance chip 32 can be eliminated.

  Using a 370 ton capacity converter, the hot metal dephosphorization treatment was performed using the top-blowing lance according to the present invention shown in FIG. 2 and having five main hole nozzles (Example of the present invention). In the used top blowing lance, the inner diameter of the innermost pipe serving as a flux supply flow path for supplying the refining flux is 66 mm, and the ratio L / D between the interval L and the inner diameter D of the innermost pipe is 340. And As the refining flux, quicklime powder (average particle size 1 mm or less) is used, and nitrogen gas is used as a carrier gas for the quicklime powder. Higher than the pressure. In addition, argon gas was used as the stirring gas blown from the bottom blowing tuyere.

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

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

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

  FIG. 4 shows a comparison between the distribution of the carbon concentration in the hot metal after the dephosphorization treatment and the distribution of the phosphorus concentration in the hot metal after the dephosphorization treatment between the present invention example and the comparative example. The ordinate and abscissa in FIG. 4 are values obtained by dividing the phosphorus concentration and the carbon concentration after the dephosphorization treatment by the average phosphorus concentration and the average carbon in the comparative example to make the dimensionless.

  As shown in FIG. 4, in the example of the present invention, it was found that the phosphorus concentration in the hot metal after the dephosphorization treatment was reduced by about 20% as compared with the comparative example. That is, it was confirmed that the use of the top-blown lance of the present invention promoted the dephosphorization reaction of the hot metal. This is presumably because in the present invention example, quick lime powder was added to the ignition point of oxygen gas for refining, and slagification of quick lime powder was promoted.

  FIG. 5 shows a comparison between the present invention example and the comparative example for the trouble occurrence rate due to the bullion insertion. The example of the present invention is a result of about 30,000 charges, and the comparative example is a result of about 5,000 charges. As shown in FIG. 5, it was confirmed that the use of the top-blowing lance of the present invention can completely prevent the trouble caused by the ingot.

DESCRIPTION OF SYMBOLS 1 Converter equipment 2 Converter 3 Top blowing lance 4 Iron shell 5 Refractory 6 Outlet 7 Bottom blowing tuyere 8 Gas introduction pipe 9 Oxygen gas pipe 10 Nitrogen gas pipe 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 Shutoff valve 22 Shutoff 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)

For refining used for oxidizing and refining hot metal housed in a converter , comprising a lance body having a four-tube structure and a lance tip connected to the lower end of the lance body to form the tip of the upper blowing lance . The top blowing lance,
The lance tip at the tip of the upper blowing lance has only a vertically downward or obliquely downward main hole nozzle,
Inside the upper blowing lance, separately having an oxygen gas supply channel for supplying refining oxygen gas and a flux supply channel for supplying refining flux together with the carrier gas,
The lower end of the innermost tube of the lance body having the four-tube structure does not reach the lance tip, thereby forming a confluence position of the oxygen gas supply passage and the flux supply passage. And
The distance L on the lance axis between the lower end position of the innermost tube and the upper surface of the lance tip is larger than the inner diameter D of the innermost tube (L> D), and L / D which is a ratio of the interval L to the inner diameter D is 340 or less,
At the merging position inside the upper blowing lance, the oxygen gas supply flow path and the flux supply flow path merge,
An upper refining lance for refining, wherein the refining oxygen gas and the refining flux are simultaneously ejected from the main hole nozzle. 2. The upper blowing lance for refining according to claim 1, wherein the ratio L / D, which is a ratio between the interval L and the inner diameter D, is less than 15. 3.   Using the refining upper blowing lance according to claim 1 or 2, spraying the refining oxygen gas and the refining flux onto the bath surface of the hot metal accommodated in the converter to perform the oxidizing refining of the hot metal. Characterized by the method of refining hot metal.

Images