Blow-refining method and steel manufacturing method

Abstract

To provide a blowing method capable of improving both a slag formation rate and a dephosphorization rate by providing an index for accurately grasping the degree of overlap between flux powder and oxygen-containing gas in a blowing process in which CaO-based flux powder is blown together with an inert gas from a center nozzle and oxygen-containing gas is blown from a plurality of peripheral nozzles around the center nozzle.SOLUTION: In a blowing process using a center nozzle for blowing CaO-containing powder and inert gas toward the bath surface of molten metal and a plurality of peripheral nozzles for blowing oxygen-containing gas toward the bath surface from the periphery of the center nozzle, the overlap ratio between a region where CaO-containing powder blown from the center nozzle collides with the bath surface and a region where oxygen-containing gas blown from the peripheral nozzles collides with the bath surface is controlled based on an accurate index.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a blowing method for refining molten iron using a top-blowing lance in which an oxygen-containing gas and refining flux powder are sprayed onto molten iron, and a method for producing steel using the blowing method. [Background technology]

[0002] In converter operation, dephosphorization is mainly performed by hot metal pretreatment, which can significantly reduce the amount of lime used, in order to reduce refining costs. This technology typically performs the treatment at a low temperature, which is favorable for dephosphorization. However, the low temperature treatment has the disadvantage that the slag does not melt easily, and some of the added flux does not contribute to the dephosphorization reaction.

[0003] As a technique to eliminate this disadvantage, Non-Patent Document 1 proposes a method of dephosphorizing molten pig iron by spraying flux powder together with gas from a top lance (powder blasting). In other words, by spraying flux powder onto the collision point (fire point) between the oxygen gas-containing jet injected from the top lance and the molten pig iron, the Fe generated at the fire point is removed. t O reacts with CaO in the flux to produce CaO·Fe with high dephosphorization ability. t As a result of the formation of the O melt, the efficiency of the dephosphorization reaction is improved.

[0004] Furthermore, Non-Patent Document 1 points out that when CaO-based flux powder is sprayed together with inert gas from a central nozzle and oxygen-containing gas is sprayed from multiple holes around the central nozzle, the overlap between the jets of CaO-based flux powder and oxygen-containing gas is small, resulting in low slag formation rate and dephosphorization rate.

[0005] Therefore, Patent Document 1 discloses a method of increasing the overlap between the impact position of the powder on the bath surface and the impact position (ignition point) of the oxygen-containing gas on the bath surface by using a lance (twisted lance) with a twisted peripheral hole for injecting oxygen gas. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5353463 [Non-patent literature]

[0007] [Non-Patent Document 1] T. Tamura, M. Miyata, Y. Higuchi and T. Matsuo: CAMP-ISIJ, 25(2012), 204. Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the method described in Patent Document 1, the torsion applied to the nozzle of the peripheral hole is determined based on the distance between the central axis of the lance and the fire point, and therefore there is room for improvement in that the degree of interference between the actual flux powder jet and the oxygen-containing gas jet is not necessarily reflected.

[0009] Therefore, the present invention aims to provide a blowing method that can improve both the slag formation rate and the dephosphorization rate by providing an index that can accurately grasp the degree of overlap between the flux powder and the oxygen-containing gas in a blowing process in which CaO-based flux powder is blown together with an inert gas from a central nozzle and an oxygen-containing gas is blown from multiple peripheral nozzles around the central nozzle. Another object of the present invention is to provide a method for producing steel using the blowing method. [Means for solving the problem]

[0010] The inventors have conducted extensive research into ways to solve the above problems, and have found that when the area where the CaO-containing powder sprayed from the central nozzle collides with the molten metal bath surface in a vessel such as a converter, electric furnace, or ladle is defined as the lime blasting area, and the area where the oxygen-containing gas sprayed from the peripheral nozzle collides with the bath surface is defined as the fire point area, the overlap between the two areas can be appropriately reflected by using the one-dimensional overlap ratio of the two areas as an index, and have thus completed the present invention. That is, the gist and configuration of the present invention are as follows.

[0011] 1. A blowing method using a central nozzle that sprays CaO-containing powder and an inert gas toward the bath surface of a molten metal and a plurality of peripheral nozzles that spray an oxygen-containing gas toward the bath surface from around the central nozzle, a lime blasting area is an area where the CaO-containing powder sprayed from the central nozzle collides with the bath surface, and a fire point area is an area where the oxygen-containing gas sprayed from the peripheral nozzles collides with the bath surface, and the diameter of the lime blasting area in a plane perpendicular to the central axis of the central nozzle on the bath surface is defined as D0, the major axis of the fire point area is defined as D1, and the center-to-center distance between the lime blasting area and the fire point area in the plane is defined as R1, wherein an overlapping ratio α defined by the following formula (1) is 0.35 or more between the central nozzle and at least one peripheral nozzle: Note JPEG0007786446000001.jpg14170

[0012] 2. The blowing method according to 1 above, wherein the peripheral nozzles further include nozzles having an overlap ratio α of −0.15 or more and 0.20 or less.

[0013] 3. A method for producing steel, which comprises refining molten iron using the blowing method described in 1 or 2 above. [Effects of the Invention]

[0014] According to the present invention, when blowing oxygen-containing gas and refining flux powder onto the molten metal from the top lance, the degree of overlap between the lime blasting zone and the hot spot zone can be used as an appropriate index. Therefore, by controlling the blowing with the top lance based on this index, the dephosphorization efficiency by the CaO-based flux powder can be improved, and the phosphorus concentration in the molten metal can be reduced. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing the structure of a top-blowing lance according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a schematic diagram illustrating the definition of an overlapping ratio α. [Figure 3] FIG. 3 is a diagram showing the structure of a top-blowing lance according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The blowing method of the present invention is based on the use of a central nozzle that sprays CaO-containing powder and inert gas toward the surface of a molten metal bath in a vessel such as a converter or electric furnace, and multiple peripheral nozzles that spray oxygen-containing gas toward the bath surface from around the central nozzle. The following describes, as a typical example, an embodiment in which the central nozzle and peripheral nozzles are integrated into a single lance, with a central opening and multiple openings around the opening (e.g., on a single circumference). However, the present invention is not limited to the following embodiment, and the central nozzle and peripheral nozzles may of course be configured as separate lances.

[0017] [First embodiment] First, the top-blowing lance used in the blowing method of the present invention will be described. One embodiment of the top-blowing lance is shown in Figure 1. Figure 1(a) is a vertical cross-sectional view, and Figure 1(b) is a plan view seen from below. The top-blowing lance 1 in the illustrated example has a central nozzle 2 on its central axis for spraying CaO-containing powder onto molten metal in, for example, a converter, and multiple peripheral nozzles 3, four in the illustrated example, that open around the central nozzle 2. The illustrated peripheral nozzles 3 are arranged so that they open at four equal positions on the circumference of a circle centered on the central axis of the lance. Furthermore, the peripheral nozzles 3 are arranged at an angle (inclination angle θ1) to the central axis of the lance in order to spray oxygen-containing gas radially outward from the central axis of the lance to expand the fire zone.

[0018] In the above-described blowing process using a top-blowing lance 1 having multiple peripheral nozzles 3 surrounding a central nozzle 2, when CaO-containing powder is injected together with inert gas from the central nozzle 2 and oxygen-containing gas is injected from the peripheral nozzles 3, it is essential to control the overlap between the impact position of the CaO-containing powder on the bath surface and the fire point, as described above. That is, it is necessary to control the overlap between the lime projection area where the CaO-containing powder injected from the central nozzle 2 impacts on the bath surface of the converter furnace and the fire point area where the oxygen-containing gas injected from the peripheral nozzles impacts on the bath surface using an overlap ratio α, which accurately indicates the overlap between the two. This overlap ratio α is expressed by the following equation (1): Note JPEG0007786446000002.jpg15170where, D0: Diameter of the lime blasting area (mm) in the plane perpendicular to the central axis of the lance on the converter bath surface D1: The major axis of the fire spot area in the plane (mm) R1: Center distance between the lime projection area and the fire point area in the plane (mm)

[0019] Next, the formula (1) that defines the overlap ratio α will be described in detail. Figure 2 shows the lime blasting zone S1 and the fire zone S2 in a plane perpendicular to the central axis of the lance on the converter bath surface, as a circle and an ellipse, respectively. The lime blasting zone S1 is a circular zone formed directly below the cylindrical central nozzle 2. The fire zone S2, on the other hand, is an elliptical zone formed by the oxygen-containing gas sprayed from the peripheral nozzles 3 inclined relative to the central axis of the lance. Also shown in Figure 2 are the diameter D0 of the lime blasting zone S1, the major axis D1 of S2, and the center-to-center distance R1 between the lime blasting zone S1 and the fire zone S2. The meaning of the above formula (1) will be explained with reference to Figure 2.

[0020] That is, on the line segment X connecting the centers of the lime projection area S1 and the fire spot area S2, the overlap between the lime projection area S1 and the fire spot area S2 is as follows: (D0+D1-2R1) / 2 (2) The sum of the radius of the lime projection area S1 on the line segment X and the major axis / 2 of the fire spot area S2 is given by the following equation (3). (D0+D1) / 2 (3) Then, by dividing the above formula (2) by the above formula (3), the above formula (1) can be derived.

[0021] Here, "Equation (2) / Equation (3) (=Equation (1))" simply indicates the ratio of oxygen and shot lime supplied to the overlapping position among the supplied oxygen and shot lime. When this ratio increases, the Fe generated at the hot spot by the shot CaO-containing powder being supplied to the hot spot increases. t O reacts with CaO in the flux to produce CaO·Fe with high dephosphorization ability. t O melt is generated. Therefore, the larger the value of equation (1), the greater the proportion of lime and oxygen used for dephosphorization. If the overlap ratio α defined by equation (1) is 0.35 or higher, a sufficient improvement in dephosphorization efficiency is observed.

[0022] Next, the calculation method for D0, D1, and R1 in this embodiment will be described. First, as the spread angle of the powder and gas from the lance nozzle, the spread angle of the jet from a cylindrical lance nozzle commonly used in converters, 12°, as described in, for example, Kiyoshi Segawa, "Iron Metallurgical Reaction Engineering," published by Nikkan Kogyo Shimbun, February 27, 1969, p. 112, is adopted. In this case, D0, D1, and R1 are each geometrically expressed by the following equations. Note that the nozzle diameter has little effect on D0, D1, and R1, so the nozzle diameter is not taken into consideration here. JPEG0007786446000003.jpg27170where, L h is the distance between the bath surface and the tip of top lance 1 (hereafter referred to as the lance height) [m]. θ1 is the inclination angle [°] of the peripheral nozzle 3 that injects the oxygen-containing gas with respect to the lance central axis (see Figure 1). x1 is the distance [m] between the centers of the peripheral nozzles 3 and the central nozzle 2 at the lance tip, which injects oxygen-containing gas (see Figure 1).

[0023] In controlling the overlap between the bath surface collision position of the CaO-containing powder and the fire point using the overlap ratio α, it is effective if α ≧ 0.35 is satisfied in the fire point region of at least one peripheral nozzle. Preferably, α ≧ 0.35 is satisfied in the fire point regions of 50% or more of all peripheral nozzles, and more preferably, α ≧ 0.35 is satisfied in the fire point regions of all peripheral nozzles.

[0024] Furthermore, it is more preferable that there are multiple fire points (more than 50% of all peripheral nozzles) with an overlap ratio α of 0.50 or more. This is because a lance usually has multiple peripheral nozzles, so there can be multiple overlaps with α ≥ 0.50. If there are three or more fire point areas on the same circumference that satisfy α ≥ 0.50, the entire lime blasting area will overlap with the fire point area, thereby making it possible to maximize the effect of the blasted lime.

[0025] Here, the above-mentioned requirement that the overlap ratio α be 0.35 or more is valid if it is realized between the central nozzle 2 and any one of the four peripheral nozzles 3 around it in the lance 1 shown in Figure 1, for example. It is preferable that α ≥ 0.35 is established for the fire point areas of 50% or more of all peripheral nozzles, and it is of course more preferable that α ≥ 0.35 is established for the fire point areas of all peripheral nozzles.

[0026] In order to make the overlap ratio α 0.35 or more, the nozzle inclination angle θ1 and the lance height L h For example, if the inclination angle θ1 of the peripheral nozzle 3 is changed or not changed, the lance height L h By changing one or more of the center distance x1 and the spread angle and adjusting the position of the fire spot area S2 relative to the lime projection area S1, an overlap ratio α of 0.35 or more can be achieved.

[0027] On the other hand, there is no need to particularly limit the upper limit of the overlap ratio α. In other words, from the viewpoint of dephosphorization efficiency, a larger α is preferable, and therefore α should be less than 1.

[0028] [Second embodiment] Next, another embodiment of the top blowing lance is shown in Figure 3. As with Figure 1, Figure 3(a) is a vertical cross-sectional view, and Figure 3(b) is a plan view seen from below. The top-blowing lance 1 shown in the figure has a central nozzle 2 on its central axis for spraying CaO-containing powder onto, for example, molten metal in a converter, and four peripheral nozzles 3 opening around the central nozzle 2, similar to the lance shown in Figure 1. The top-blowing lance 1 shown in Figure 3 has peripheral nozzles 4 arranged outside the peripheral nozzles 3, opening at four equal positions on a circle whose diameter is larger than the circle around which the peripheral nozzles 3 are arranged, with the center at the central axis of the lance. The peripheral nozzles 4 are arranged at positions that do not overlap with the peripheral nozzles 3 in the radial direction and are offset from the arrangement period of the peripheral nozzles 3. Furthermore, the inclination angle θ2 of the peripheral nozzles 4 relative to the central axis of the lance is set to be greater than the inclination angle θ1 of the peripheral nozzles 3 so that the peripheral nozzles 4 can inject oxygen-containing gas radially outward from the hot spot area of ​​the peripheral nozzles 3, thereby contributing to ensuring the area of ​​the hot spot area.

[0029] In blowing using the top-blowing lance shown in Fig. 3, it is also important that the overlap ratio α between the central nozzle 2 and any one of the peripheral nozzles 3 be 0.35 or more. The reason for setting the overlap ratio α for the peripheral nozzle 3 to 0.35 or more is as described above. Of course, it is more preferable that all four peripheral nozzles 3 satisfy α: 0.35 or more.

[0030] In blowing using the top-blowing lance shown in Figure 3, it is further preferable that the overlap ratio α between the central nozzle 2 and at least one of the peripheral nozzles 4 (which have a larger inclination angle than the peripheral nozzles 3) is -0.15 or more. The reason for this will be described later. Of course, it is more preferable that all four peripheral nozzles 4 satisfy α: -0.15 or more.

[0031] In the case of blowing using the top-blowing lance shown in Figure 3, it is more preferable to set the overlap ratio α between the center nozzle 2 and the peripheral nozzle 3 to 0.35 or more but less than 1, and to set the overlap ratio α between the center nozzle 2 and the peripheral nozzle 4 to -0.15 to 0.20. When using two peripheral nozzles with different inclination angles as shown in Figure 3, the large inclination angle of the peripheral nozzle 4 is particularly effective in increasing the fire spot area to promote dephosphorization by bulk slag. That is, if the overlap ratio α for the peripheral nozzle 4 exceeds 0.20, in other words, if the opening of the peripheral nozzle 4 is inclined toward the center nozzle 2, the fire spot area may be small, and slag formation and dephosphorization may not proceed. On the other hand, if the overlap ratio α for the peripheral nozzle 4 is less than -0.15, the bath surface dynamic pressure of the oxygen-containing gas may decrease significantly, increasing the frequency of slopping (slag ejection), which may result in reduced productivity. Furthermore, secondary combustion of CO gas generated in the vessel with oxygen increases, which reduces the reaction efficiency of the top-blown oxygen and may result in an extension of the blowing time. For these reasons, it is preferable that the overlap ratio α for the peripheral nozzles 4 be set to -0.15 to 0.20.

[0032] 3, there are four peripheral nozzles 3 and four peripheral nozzles 4, for a total of eight, but the number is not limited to this and may be less or more than that. Also, although a straight nozzle outlet is used, a Laval nozzle outlet with a larger outlet diameter may also be used.

[0033] The nozzle diameters of the peripheral nozzles 3 and 4 may be determined appropriately, taking into consideration the flow rate of the oxygen-containing gas and the distance between the lance and the bath surface (hereinafter also referred to as the lance height). The diameter of the central nozzle 2 may also be determined, taking into consideration the flow rates of the powder and inert gas, and the back pressure. Furthermore, in the illustrated example, the ratio of the diameter of the peripheral nozzle 4 to the diameter of the peripheral nozzle 3 is 1, but this ratio may be changed. However, since a larger nozzle diameter ratio will result in uneven gas flow rates, a nozzle diameter ratio of approximately 0.75 to 1.35 is desirable. [Example]

[0034] The molten iron shown in Table 1 was charged into a 250-ton top-and-bottom blown converter, and quicklime was added from the top at a feed rate of 400 kg / min. CaO powder was added from the center nozzle 2 of the top-blowing lance shown in Figure 1 at a feed rate of 1.4 kg / min / t with nitrogen gas of 0.18 Nm 3 Oxygen gas was sprayed onto the bath surface at 1.8 Nm / min / t. 3 Nitrogen gas was blown onto the bath surface at a rate of 0.18 Nm / min / t from the bottom blowing tuyeres. 3 The lance height was set to 2100 to 2500 mm and the hot metal dephosphorization blowing was carried out for 12 minutes.

[0035] [Table 1]

[0036] In the above blowing, as shown in Table 2, lances with different inclination angles θ1 of the peripheral nozzles 3 were used to change the overlap ratio α in the blowing.

[0037] The overlap ratio α was calculated from the operating conditions. The carbon concentration of the hot metal after the blowing process, the hot metal temperature after the process, and the phosphorus concentration before and after the process were measured. The calculation results and the measurement results are shown in Table 2. Furthermore, the set basicity of the flux (CaO / SiO2 mass%) and the actual slag basicity (CaO mass% in the slag / SiO2 mass% in the slag) were also measured and are shown in Table 2.

[0038] As shown in Table 2, the hot metal temperature after the blowing treatment was 1360 to 1371°C, and the P concentration after the treatment was 0.025 to 0.037 mass%. The set basicity (mass% ratio of CaO / SiO2) was 2.5, while the actual basicity (mass% CaO in the slag / mass% SiO2 in the slag) was 2.1 to 2.4.

[0039] The results shown in Table 2 reveal that the overlap ratio α of Comparative Examples 1-1 and 1-2 was 0.14, less than 0.35. Therefore, the actual basicity was low at 2.1 to 2.2, i.e., the slag conversion rate was low, and the post-treatment [P] was high at 0.029 to 0.037 mass%, i.e., the dephosphorization efficiency was low. For Comparative Example 1-3, the overlap ratio α was 0.31, less than 0.35. Therefore, the actual basicity was low, the slag conversion rate was low, and the post-treatment [P] was high at 0.034 mass%, i.e., the dephosphorization efficiency was low.

[0040] For Examples 1-1 to 1-5, the overlap ratio α was 0.37 to 0.92. That is, the overlap between the fire point region generated by the oxygen gas jet injected from the peripheral nozzle 3 and the collision position of the projected CaO powder on the bath surface was large, which promoted the melting of CaO, improved the actual basicity, and reduced [P] after treatment.

[0041] [Table 2] [Example]

[0042] The molten iron shown in Table 1 was charged into a 250-ton top-and-bottom blown converter. Quicklime was added from the top at a feed rate of 400 kg / min. CaO powder was added from the center nozzle 2 of the top-blowing lance shown in Figure 3 at a feed rate of 1.4 kg / min / t with nitrogen gas of 0.18 Nm. 3 Oxygen gas was sprayed onto the bath surface at 1.8 Nm / min / t. 3 Nitrogen gas was blown onto the bath surface at a rate of 0.18 Nm / min / t from the bottom blowing tuyeres. 3 The lance height was set to 2200 mm and the hot metal dephosphorization blowing was carried out for 12 minutes.

[0043] The inclination angle θ1 of the peripheral nozzle 3 and the inclination angle θ2 of the peripheral nozzle 4 are as shown in Table 3. Lances with different inclination angles θ1 and θ2 were used to change the overlap ratios α1 and α2 during blowing. The overlap ratio α2 for the peripheral nozzle 4 was calculated by using D2 and R2 for the peripheral nozzle 4 instead of D1 and R1 in the above formula (1). In Comparative Examples 2-1 and 2-2, lances with peripheral nozzles all having the same inclination angle were arranged on the same circumference (based on the arrangement in Figure 1(b)). In Comparative Example 2-3 and Invention Examples 2-6 and 2-7, two types of peripheral nozzles, 3 and 4, were arranged alternately at equal intervals (based on the arrangement in Figure 3(b)).

[0044] The overlap ratio α was calculated from the operating conditions. The carbon concentration of the hot metal after the blowing process, the hot metal temperature after the process, and the phosphorus concentration before and after the process were also measured. The calculation results and the measurement results are shown in Table 3. Furthermore, the set basicity of the flux (CaO / SiO2 mass%) and the actual slag basicity (CaO mass% in the slag / SiO2 mass% in the slag) were also measured and are shown in Table 3.

[0045] As shown in Table 3, the hot metal temperature after the blowing treatment was 1354 to 1374°C, and the P concentration after the treatment was 0.025 to 0.037 mass%. The set basicity (mass% ratio of CaO / SiO2) was 2.5, while the actual basicity (mass% CaO in the slag / mass% SiO2 in the slag) was 2.1 to 2.4.

[0046] The results shown in Table 3 indicate that in Comparative Examples 2-1 and 2-2, the peripheral nozzles all had the same inclination angle, and therefore the overlap ratio α1 was 0.14, less than 0.35. Therefore, the actual basicity was low at 2.1 to 2.2, i.e., the slag conversion rate was low, and the post-treatment [P] was high at 0.030 to 0.034 mass%, i.e., the dephosphorization efficiency was low. In Comparative Example 2-3, the inclination angle θ1 of the peripheral nozzle 3 was 14°, and the overlap ratio α was 0.31, less than 0.35. Therefore, the actual basicity was low, the slag conversion rate was low, and the post-treatment [P] was high at 0.037 mass%, i.e., the dephosphorization efficiency was low.

[0047] For Examples 2-1 to 2-7, the inclination angle θ1 of the peripheral nozzle 3 was 0 to 13°, the inclination angle θ2 of the peripheral nozzle 4 was 12 to 26°, and the overlap ratio α1 was 0.37 to 0.92. Therefore, there was a large overlap between the fire point region generated by the oxygen gas jet injected from the peripheral nozzle 3 and the collision position of the projected CaO powder on the bath surface, which promoted the melting of CaO, improved the actual basicity, and reduced [P] after treatment.

[0048] For Inventive Examples 2-1 to 2-5, α2 was within the range of -0.15 to 0.2, so no decrease in dephosphorization ability or increase in slopping frequency was observed. In Inventive Example 2-6, α2 was greater than 0.2, resulting in a smaller fire spot area, so a decrease in dephosphorization ability was observed compared to Inventive Examples 2-1 to 2-5. In Inventive Example 2-7, α2 was < -0.15, so slopping occurred and some of the slag was discharged outside the furnace, resulting in slag formation and a decrease in dephosphorization ability compared to Inventive Examples 2-1 to 2-5.

[0049] [Table 3] [Industrial Applicability]

[0050] The present invention is effective not only for the dephosphorization treatment described above but also for dephosphorization treatment in an electric furnace or ladle, and is effective in all refining treatments using top blowing. [Explanation of symbols]

[0051] 1 Top blowing lance 2 center nozzle 3 Peripheral nozzle 4 Peripheral nozzles

Claims

1. In a blowing process using a central nozzle that sprays CaO-containing powder and an inert gas toward a bath surface of a molten metal and a plurality of peripheral nozzles that spray an oxygen-containing gas toward the bath surface from around the central nozzle, A region where the CaO-containing powder sprayed from the central nozzle collides with the bath surface is defined as a lime projection region, and a region where the oxygen-containing gas sprayed from the peripheral nozzle collides with the bath surface is defined as a fire point region, and the diameter of the lime projection region in a plane perpendicular to the central axis of the central nozzle on the bath surface is defined as D0, the major axis of the fire point region is defined as D1, and the center-to-center distance between the lime projection region and the fire point region in the plane is defined as R1, wherein an overlapping ratio α defined by the following formula (1) between the central nozzle and at least one peripheral nozzle is 0.35 or more, A blowing method, wherein in addition to the peripheral nozzles, a nozzle having an overlap ratio α of −0.15 or more and 0.20 or less is used. Note

2. A method for producing steel, comprising refining molten iron using the blowing method according to claim 1.

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