METHOD FOR OPERATING CONVERTER

Abstract

When the decarburization refining of molten iron is performed by top-blowing oxygen gas from the top blowing lance, the oscillation of molten iron, a bubble burst, and spitting due to the bubble burst are suppressed. A refining method for a converter includes decarburizing molten iron in the converter with a top blowing lance having Laval nozzles disposed at the lower end thereof by blowing oxygen gas on the surface of the molten iron in the converter through the Laval nozzles, in which one or both of an oxygen feeding rate from the top blowing lance and lance height LH are adjusted in such a manner that an oxygen accumulation index S(F) is 40 or less.

Claims

1. A method for operating a converter, comprising: a refining process including decarburizing molten iron in a converter with a top blowing lance having one or more Laval nozzles disposed at a lower end thereof by blowing oxygen gas on a surface of the molten iron in the converter through the one or more Laval nozzles, wherein: an oxygen gas flow rate F per unit hot spot area (Nm.sup.3/(m.sup.2s)) is determined by Formula (1) described below, an oxygen accumulation index S(F) in the converter is determined from the oxygen gas flow rate F and Formula (2) described below, and one or both of an oxygen feeding rate Q.sub.g from the top blowing lance and lance height LH are adjusted such that the oxygen accumulation index S(F) satisfies Formula (3) described below, $\begin{matrix} F = \frac{{(\frac{Q_{g}}{n})}^{1.2}}{\frac{}{6} r [{(r^{2} + 4 .Math. L)}^{\frac{3}{2}} - r^{3}]} {(\frac{4.8586 .Math. .Math. P_{0}^{0.112} d_{c}^{- 0.44} v_{gc}}{1630})}^{0.2} & (1) \\ .Math. S (F) = .Math. .Math. (\frac{1}{F_{0}} - \frac{1}{F}) .Math. .Math. .Math. t & (2) \\ .Math. S (F) 40 & (3) \end{matrix}$ where in Formula (1), n is a number of the one or more Laval nozzles disposed at the lower end of the top blowing lance, d.sub.c is a throat diameter (mm) of each of the one or more Laval nozzles, Q.sub.g is the oxygen feeding rate (Nm.sup.3/s) from the top blowing lance, P.sub.0 is a supply pressure (Pa) of the oxygen gas to the one or more Laval nozzles, v.sub.gc is an oxygen gas flow velocity calculated from the lance height LH (m) at a collision surface of the surface of the molten iron and is the oxygen gas flow velocity (m/s) along a central axis of each of the one or more Laval nozzles, r is a radius (mm) of a cavity formed by colliding the oxygen gas with the surface of the molten iron, and L is a depth (mm) of the cavity, and where in Formula (2), is a constant ((m.sup.2s)/Nm.sup.3), F.sub.0 is a constant (Nm.sup.3/(m.sup.2s)), and t is a data collection time interval (s).

2. The method for operating a converter according to claim 1, wherein: an actual value of the oxygen accumulation index S(F) calculated from Formula (2) and an amount of unidentified oxygen are monitored during the blowing to determine the constant , the amount of unidentified oxygen is defined by a difference between an amount of oxygen input and an amount of oxygen output, the amount of oxygen input is defined by a sum of: (i) an amount of the oxygen gas supplied from the top blowing lance and (ii) an amount of oxygen in an auxiliary raw material charged into the converter, and the amount of oxygen output is defined by a sum of: (i) amounts of oxygen present as CO gas, CO.sub.2 gas, and oxygen gas in an exhaust gas from the converter and (ii) an amount of oxygen consumed by a desiliconization reaction and present as SiO.sub.2 in the converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a graph illustrating the relationship between the average oxygen efficiency for decarburization and the oxygen gas flow rate F per unit hot spot area calculated from Formula (1).

[0024] FIG. 2 is a graph illustrating the relationship between the index W of metal dropped to outside of a converter and the maximum value S(F).sub.max of an oxygen accumulation index S(F) in a converter calculated from Formula (2).

[0025] FIG. 3 is a graph illustrating the relationship between the maximum acceleration a.sub.max of vessel vibration and the maximum value S(F).sub.max of the oxygen accumulation index S(F) calculated from Formula (2).

DETAILED DESCRIPTION

[0026] The present application will be described below through the use of disclosed embodiments. First, the circumstances leading to the completion of the disclosed embodiments will be described.

[0027] The inventors have conducted studies on the influence of the lance height LH of a top blowing lance on the amount of metal adhering to the wall of a converter and the top blowing lance when hot metal is subjected to decarburization refining with the 300-ton-capacity converter by top-blowing oxygen gas (industrial pure oxygen gas) on hot metal in the converter, the converter being configured to enable oxygen gas to be blown from the top blowing lance and configured to enable a stirring gas to be simultaneously blown through a bottom blowing tuyere in the bottom section of the converter. Argon gas was used as the bottom-blown stirring gas. The lance height LH refers to a distance (m) from the tip of the top blowing lance to the surface of the hot metal when the hot metal in the converter is in a static state.

[0028] In an experiment, three types of top blowing lances (top blowing lances A, B, and C) were used as presented in Table 1. The oxygen feeding rate (the flow rate of oxygen supplied) from each of the top blowing lances was changed in the range of 750 to 1,000 Nm.sup.3/min. The lance height LH was changed in the range of 2.2 to 2.8 m. Metal adhering to the throat and the hood of the converter during blowing and then dropped to the outside of the converter was recovered after the blowing and weighed to check the influence of the lance height LH and blowing conditions on the amount of adhering metal.

TABLE-US-00001 TABLE 1 Throat Nozzle Type of Number Shape diameter of Exit tilt angle top blowing of main of main main hole diameter of main lance hole hole (mm) (mm) hole () Top blowing 4 Laval 76.0 87.0 17 lance A nozzle Top blowing 5 Laval 57.0 67.2 15 lance B nozzle Top blowing 5 Laval 65.0 75.3 15 lance C nozzle

[0029] In a test, an accelerometer was attached to the tilt shaft of the converter, and the acceleration in the tilt shaft direction was measured during blowing. The obtained acceleration signal was taken into an analyzer, recorded, and subjected to fast Fourier transform to perform frequency analysis of vessel vibration.

[0030] In the test, the supply of oxygen gas from each top blowing lance was started when the carbon concentration in hot metal was 4.0% by mass, and the supply of oxygen gas was stopped when the carbon concentration in molten steel was 0.05% by mass.

[0031] In the decarburization refining of hot metal by top-blowing oxygen gas, an oxygen gas flow rate F per unit hot spot area (Nm.sup.3/(m.sup.2s)) is represented by Formula (1) below. The oxygen gas flow rate F per unit hot spot area is the average of the flow rates of colliding oxygen gas per unit area at multiple hot spots, which are portions of the surface of hot metal colliding with top-blown oxygen gas in the converter, for a period of the decarburization refining.

[00004] $\begin{matrix} .Math. [Math . .Math. 4] \\ F = \frac{{(\frac{Q_{g}}{n})}^{1.2}}{\frac{}{6} r [{(r^{2} + 4 .Math. L)}^{\frac{3}{2}} - r^{3}]} {(\frac{4.8586 .Math. .Math. P_{0}^{0.112} d_{c}^{- 0.44} v_{gc}}{1630})}^{0.2} & (1) \end{matrix}$

[0032] In Formula (1), n is the number (-) of the Laval nozzles disposed at the lower end of the top blowing lance. d.sub.c is the throat diameter (mm) of each of the Laval nozzles. Q.sub.g is the oxygen feeding rate (Nm.sup.3/s) from the top blowing lance. P.sub.0 is the supply pressure (Pa) of the oxygen gas to the Laval nozzles of the top blowing lance.

v.sub.gc is an oxygen gas flow velocity calculated from the lance height LH (m) at a collision surface of a hot metal surface and is the oxygen gas flow velocity (m/s) along the central axis of each of the Laval nozzles. r is the radius (mm) of a cavity formed by collision of the oxygen gas with the hot metal surface. L is the depth (mm) of the cavity.

[0033] Methods for calculating the oxygen gas flow velocity v.sub.gc (m/s), the diameter r (mm) of the cavity, and the depth L (mm) of the cavity will be described below.

[0034] Assuming that a gas flow in the Laval nozzle is adiabatic change, the discharge flow velocity v.sub.g0 (m/s) of a gas ejected from the Laval nozzle is represented by Formula (7). In Formula (7), g is the gravitational acceleration (m/s.sup.2). p.sub.c is a pressure (static pressure) (Pa) at the throat of the Laval nozzle. p.sub.e is a pressure (static pressure) (Pa) at the nozzle exit of the Laval nozzle. v.sub.c is a specific volume (m.sup.3/kg) in the throat of the Laval nozzle. v.sub.e is a specific volume (m.sup.3/kg) in the exit of the Laval nozzle. K is an isentropic expansion factor.

[00005] $\begin{matrix} [Math . .Math. 5] \\ v_{g .Math. .Math. 0}^{2} = 2 g \frac{K}{K - 1} (p_{c} v_{c} - p_{e} v_{e}) & (7) \end{matrix}$

[0035] v.sub.gc that is the oxygen gas flow velocity along the central axis of the Laval nozzle after ejection from the Laval nozzle is known to be determined as a function of the distance from the nozzle to the surface of the hot metal. Thus, considering region length x.sub.c (m) called a potential core formed directly below the exit of the Laval nozzle, the oxygen gas flow velocity v.sub.gc is represented by Formula (8) below. In Formula (8), and are constants. Accordingly, in the case where v.sub.g0, LH, and x.sub.c are known, the oxygen gas flow velocity v.sub.gc can be calculated using Formula (8) below.

[00006] $\begin{matrix} [Math . .Math. 6] \\ v_{gc} = v_{g .Math. .Math. 0} (\frac{LH - x_{c}}{d_{c}}) .Math. & (8) \end{matrix}$

[0036] The depth L (mm) of the cavity formed on the molten iron surface with which the jet collides is represented by Formula (9) below. In Formula (9), is a dimensionless constant and is a value in the range of 0.5 to 1.0. In this embodiment, the depth L of the cavity is calculated by setting to 1.0.

[00007] $\begin{matrix} [Math . .Math. 7] \\ L = 63.0 {(.Math. \frac{Q_{g}}{n d_{c}})}^{\frac{2}{3}} e^{(- 0.78 \frac{LH}{63.0 {(.Math. \frac{Q_{g}}{n d_{c}})}^{\frac{2}{3}}})} & (9) \end{matrix}$

[0037] The diameter r (mm) of the cavity formed on the molten iron surface with which the jet collides is represented by Formula (10) below. In Formula (10), .sub.s is a jet spread angle ().

[Math. 8]

r=LHtan(.sub.s) (10)

[0038] FIG. 1 is a graph illustrating the relationship between the average oxygen efficiency (%) for decarburization during blowing when decarburization is performed in such a manner that the carbon concentration is changed from 3% by mass to 1% by mass during the blowing and the oxygen gas flow rate F per unit hot spot area (Nm.sup.3/(m.sup.2s)) calculated from Formula (1). The average oxygen efficiency (%) for decarburization was defined by Formula (11) using an exhaust gas flow rate Q.sub.offgas (Nm.sup.3/s), a CO concentration in the exhaust gas (C.sub.CO; % by volume), and a CO.sub.2 concentration in the exhaust gas (C.sub.CO2; % by volume).

[00008] $\begin{matrix} [Math . .Math. 9] \\ = \frac{11.2}{22.4} (C_{CO} + C_{CO .Math. .Math. 2}) \frac{Q_{offgas}}{Q_{g}} 100 & (11) \end{matrix}$

[0039] As apparent from FIG. 1, the average oxygen efficiency (%) for decarburization decreases as the oxygen gas flow rate F per unit hot spot area increases. In other words, a higher oxygen gas flow rate F per unit hot spot area results in a larger amount of oxygen accumulated in the converter.

[0040] FIG. 2 is a graph illustrating the relationship between the index W of metal dropped to outside of a converter and the maximum value S(F).sub.max of an oxygen accumulation index S(F) in the converter during blowing. The oxygen accumulation index S(F) in the converter is defined by Formula (2) below. In Formula (2), F is the oxygen gas flow rate F per unit hot spot area calculated from Formula (1). is a constant ((m.sup.2s)/Nm.sup.3). F.sub.0 is a constant (Nm.sup.3/(m.sup.2s)). In this embodiment, the constant is set to 0.07 (m.sup.2s)/Nm.sup.3, and the constant F.sub.0 is set to 0.60 Nm.sup.3/(m.sup.2s). The constant is a value in the range of 0.05 to 0.10 (m.sup.2s)/Nm.sup.3 in accordance with the flow rate of a bottom-blown gas per unit mass of molten steel. t is a data collection time interval (s) and is, for example, 1 second in this embodiment. In the case where t is 1 second and where the blowing time is 20 minutes, the oxygen accumulation index S(F) is calculated by calculating (1/F.sub.01/F) every 1 second, integrating this operation about 1,200 times, and multiplying the resulting value by .

[00009] $\begin{matrix} [Math . .Math. 10] \\ S (F) = .Math. .Math. (\frac{1}{F_{0}} - \frac{1}{F}) .Math. .Math. .Math. t & (2) \end{matrix}$

[0041] The index W of metal dropped to outside of a converter is defined by Formula (12) below. The Measured mass of metal dropped to outside of a converter described in the denominator on the right-hand side of Formula (12) is the average mass of metal dropped after the completion of blowing in multiple charge tests.

[00010] $\begin{matrix} [Math . .Math. 11] \\ W = \frac{\begin{matrix} Measured .Math. .Math. mass .Math. .Math. of .Math. .Math. metal .Math. .Math. dropped \\ to .Math. .Math. outside .Math. .Math. of .Math. .Math. a .Math. .Math. converter .Math. .Math. (kg) \end{matrix}}{\begin{matrix} Average .Math. .Math. mass .Math. .Math. of .Math. .Math. metal .Math. .Math. dropped .Math. .Math. to .Math. .Math. outside .Math. .Math. of .Math. .Math. a \\ converter .Math. .Math. in .Math. .Math. blowing .Math. .Math. at .Math. .Math. {S (F)}_{\max} .Math. .Math. of .Math. .Math. less .Math. .Math. than .Math. .Math. 40 .Math. .Math. (kg) \end{matrix}} & (12) \end{matrix}$

[0042] As apparent from FIG. 2, the index W of metal dropped to outside of the converter increases sharply when the maximum value S(F).sub.max of the oxygen accumulation index S(F) in the converter is more than 40.

[0043] FIG. 3 is a graph illustrating the relationship between the maximum acceleration a.sub.max at a natural frequency of 0.35 Hz calculated from Formula (6) in vessel vibration during blowing and the maximum value S(F).sub.max of the oxygen accumulation index S(F) in the converter.

[0044] As apparent from FIG. 3, the maximum acceleration a.sub.max increases as the maximum value S(F).sub.max of the oxygen accumulation index S(F) in the converter during blowing increases. When the maximum value S(F).sub.max is more than 40, the increment of the maximum acceleration a.sub.max is increased. In other words, it is found that when the maximum value S(F).sub.max is more than 40, the oscillation of the hot metal can be increased.

[0045] It should be noted here that regardless of the difference in the Laval nozzles of the top blowing lance, the oxygen gas flow rate F per unit hot spot area negatively correlates with the average oxygen efficiency for decarburization, the maximum value S(F).sub.max of the oxygen accumulation index S(F) in the converter during blowing positively correlates with the index W of metal dropped to outside of the converter and the maximum acceleration a.sub.max of vessel vibration, and that both of the index W of metal dropped to outside of the converter and the maximum acceleration a.sub.max of vessel vibration are remarkably increased at a maximum value S(F).sub.max of more than 40.

[0046] To suppress the oscillation of molten iron, to reduce metal adhering to the throat and the hood of the converter, and to prevent a decrease in iron yield, the results indicate that it is important to control the maximum value S(F).sub.max of the oxygen accumulation index S(F) in the converter to 40 or less, i.e., to satisfy Formula (3):

S(F)40 (3)

[0047] The constant changes slightly, depending on, for example, the operation state of the vessel. Thus, at the time of implementation, the actual value of the oxygen accumulation index S(F) calculated from Formula (2) and the amount of unidentified oxygen are preferably monitored during blowing to determine the constant on the basis of the actual value of the oxygen accumulation index S(F) and the amount of unidentified oxygen, the amount of unidentified oxygen being defined by the difference between the amount of oxygen input and the amount of oxygen output, the amount of oxygen input being defined by the total of the amount of the oxygen gas supplied from the top blowing lance and the amount of oxygen in an auxiliary raw material charged into the converter, the amount of oxygen output being defined by the total of amounts of oxygen present as CO gas, CO.sub.2 gas, and oxygen gas in an exhaust gas from the converter and the amount of oxygen consumed by a desiliconization reaction and present as SiO.sub.2 in the converter.

[0048] The disclosed embodiments based on the above examination results and relates to a refining method in a converter, the method including subjecting molten iron in the converter to oxidation refining such as decarburization refining with a top blowing lance having Laval nozzles disposed at the lower end thereof by blowing oxygen gas on the surface of the molten iron in the converter through the Laval nozzle, in which one or both of the oxygen feeding rate Q.sub.g from the top blowing lance and the lance height LH are adjusted in such a manner that the oxygen gas flow rate F per unit hot spot area determined by Formula (1) described above and the oxygen accumulation index S(F) in the converter determined by Formula (2) satisfy Formula (3) described above.

[0049] By adjusting one or both of the oxygen feeding rate Q.sub.g from the top blowing lance and the lance height LH in such a manner that the oxygen accumulation index S(F) satisfies Formula (3), excessive supply of oxygen to the surface of the molten iron is suppressed, subsequently excessively large CO bubbles generation is suppressed because the reaction of carbon and oxygen occurs in the molten iron, thereby suppressing a bubble burst and spitting due to the bubble burst.

[0050] As illustrated in FIG. 3, by adjusting one or both of the oxygen feeding rate Q.sub.g from the top blowing lance and the lance height LH in such a manner that the oxygen accumulation index S(F) satisfies Formula (3), the increase of the oscillation of the molten iron can be suppressed.

[0051] As described above, by implementing the method for operating a converter according to the embodiment, it is possible to suppress the oscillation of molten iron and a bubble burst and spitting due to the bubble burst. This reduces the scattering of iron to the outside of the converter, reduces cost required to recover and reuse the metal, and can suppress a decrease in the operating rate of the converter due to the removal of metal adhering and deposited on, for example, the throat of the converter.

EXAMPLES

[0052] Examples of the disclosed embodiments will be described below. Decarburization refining was performed with a 300-ton-capacity converter configured to enable oxygen gas to be blown from the top blowing lance and configured to enable a stirring gas to be blown through a bottom blowing tuyere in the bottom section of the converter (hereinafter, referred to as a top-bottom blown converter). As the evaluation of the scattering of iron to the outside of the converter, the index W of metal dropped to outside of a converter defined by Formula (12) was used.

[0053] The top blowing lance used in this example had four identically-shaped Laval nozzles serving as jet nozzles at its tip portion. The Laval nozzles are arranged concentrically to the axial center of the main body of the top blowing lance at regular intervals and an angle of 17 between the axial center of the main body of the top blowing lance and the central axis of each of the nozzles (hereinafter, referred to as a nozzle tilt angle). Each Laval nozzle had a throat diameter d.sub.c of 76.0 mm and an exit diameter d.sub.e of 87.0 mm.

[0054] Similarly, the following top blowing lances were used: a top blowing lance having five Laval nozzles, a nozzle tilt angle of 15, a throat diameter d.sub.c of 65.0 mm, and an exit diameter d.sub.e of 78.0 mm; a top blowing lance having five Laval nozzles, a nozzle tilt angle of 15, a throat diameter d.sub.c of 65.0 mm, and an exit diameter d.sub.e of 75.3 mm; and a top blowing lance having five Laval nozzles, a nozzle tilt angle of 15, a throat diameter d.sub.c of 57.0 mm, and an exit diameter d.sub.e of 67.2 mm. Table 2 presents the specifications of the top blowing lances used in tests.

TABLE-US-00002 TABLE 2 Number Throat diameter Exit diameter Nozzle tilt of main of main hole of main hole angle of main hole (mm) (mm) hole () Example 1 4 76.0 87.0 17 Example 2 5 65.0 78.0 15 Example 3 5 65.0 75.3 15 Example 4 5 57.0 67.2 15 Comparative 4 76.0 87.0 17 example 1 Comparative 4 76.0 87.0 17 example 2 Comparative 5 65.0 78.0 15 example 3 Comparative 5 65.0 78.0 15 example 4 Comparative 5 65.0 78.0 15 example 5

[0055] A method for operating a converter was as follows: After scrap iron was charged into the top-bottom blown converter, hot metal with a temperature of 1,260 C. to 1,280 C. was charged into the top-bottom blown converter. Decarburization refining was then performed by blowing argon gas or nitrogen gas serving as a stirring gas into the hot metal through the bottom blowing tuyere while oxygen gas was blown on the surface of the hot metal from the top blowing lance at an average flow rate of 2.0 Nm.sup.3/(hrt) until the carbon concentration of molten steel reached 0.05% by mass. The amount of scrap iron charged was adjusted in such a manner that the temperature of the molten steel was 1,650 C. at the time of the completion of the refining. Table 3 presents the composition and the temperature of the hot metal used.

TABLE-US-00003 TABLE 3 Chemical composition of molten iron (% by mass) Temperature of molten C Si Mn P S Cr iron ( C.) 3.9-4.2 0.01- 0.12- 0.016- 0.006- tr 1,260-1,280 0.04 0.25 0.036 0.015

[0056] Table 4 presents the oxygen feeding rate from the top blowing lance and the lance height LH. As presented in Table 4, each of the oxygen feeding rate from the top blowing lance and the lance height LH was separately set for each of sections 1, 2, and 3 in accordance with the carbon concentration in the hot metal.

TABLE-US-00004 TABLE 4 Carbon Oxygen feeding concen- rate Lance height tration (Nm.sup.3/min) (m) Section (% by mass) Section Average Section Average Example 1 >3.0 800 898 2.80 2.64 1 2 3.0-0.5 950 5.60 3 <0.5 800 2.50 Example 1 >3.0 750 885 2.50 2.48 2 2 3.0-0.5 950 2.45 3 <0.5 800 2.60 Example 1 >3.0 850 840 2.60 2.43 3 2 3.0-0.5 850 2.40 3 <0.5 750 2.20 Example 1 >3.0 850 840 2.60 2.43 4 2 3.0-0.5 850 2.40 3 <0.5 750 2.30 Compar- 1 >3.0 850 883 2.80 2.64 ative 2 3.0-0.5 900 2.55 example 3 <0.5 850 2.70 1 Compar- 1 >3.0 850 840 2.80 2.55 ative 2 3.0-0.5 850 2.50 example 3 <0.5 750 2.30 2 Compar- 1 >3.0 750 885 2.60 2.51 ative 2 3.0-0.5 950 2.45 example 3 <0.5 800 2.70 3 Compar- 1 >3.0 800 865 2.70 2.55 ative 2 3.0-0.5 900 2.50 example 3 <0.5 800 2.50 4 Compar- 1 >3.0 850 840 2.60 2.44 ative 2 3.0-0.5 850 2.40 example 3 <0.5 750 2.30 5

[0057] The oxygen feeding rate from the top blowing lance and the lance height LH were changed in accordance with the different nozzles of the top blowing lance in such a manner that the oxygen gas flow velocity v.sub.gc at the collision surface of the hot metal surface was in the range of about 120 to 240 m/s in sections 1, 2, and 3. The flow rate of the bottom-blown gas was constant in all tests.

[0058] Table 5 presents the oxygen flow rate F per unit hot spot area calculated from Formula (1), the maximum value S(F).sub.max of an oxygen accumulation index S(F) in the converter calculated from Formula (2), and operation results for each test.

TABLE-US-00005 TABLE 5 Index W of Carbon Flow rate Blowing metal dropped concentration (Nm.sup.3/(m.sup.3 .Math. s)) time to outside of Section (% by mass) Section Average S(F).sub.max (min) converter () Example 1 1 >3.0 0.962 0.758 29.5 21.0 0.98 2 3.0-0.5 0.668 3 <0.5 0.834 Example 2 1 >3.0 1.002 0.780 35.9 22.4 1.04 2 3.0-0.5 0.669 3 <0.5 0.946 Example 3 1 >3.0 0.805 0.759 27.3 22.0 1.08 2 3.0-0.5 0.734 3 <0.5 0.806 Example 4 1 >3.0 0.761 0.759 16.3 22.4 1.02 2 3.0-0.5 0.703 3 <0.5 0.722 Comparative 1 >3.0 0.870 0.762 43.9 21.1 1.78 example 1 2 3.0-0.5 0.709 3 <0.5 0.831 Comparative 1 >3.0 0.870 0.793 45.8 23.0 1.88 example 2 2 3.0-0.5 0.825 3 <0.5 0.835 Comparative 1 >3.0 1.056 0.798 41.7 22.7 1.45 example 3 2 3.0-0.5 0.669 3 <0.5 0.994 Comparative 1 >3.0 0.994 0.822 49.2 23.2 1.88 example 4 2 3.0-0.5 0.744 3 <0.5 0.899 Comparative 1 >3.0 0.855 0.808 42.8 23.3 1.77 example 5 2 3.0-0.5 0.776 3 <0.5 0.900

[0059] As apparent from Table 5, the blowing time was almost equal between the examples and the comparative examples. However, the index W of metal dropped to outside of the converter in each of Examples 1 to 4 at the time of the completion of the blowing was significantly smaller than those in Comparative examples 1 to 5 at the time of the completion of the blowing. These results indicated that at an oxygen accumulation index S(F) of 40 or less, the adhesion of metal can be suppressed, so that the converter operation that can control a decrease in iron yield can be performed.

METHOD FOR OPERATING CONVERTER

Assignee

Inventors

Cpc classification

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C21C5/32

CHEMISTRY; METALLURGY

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C21C5/5217

CHEMISTRY; METALLURGY

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C21C5/4606

CHEMISTRY; METALLURGY

International classification

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C21C5/32

CHEMISTRY; METALLURGY

Classification Explorer

C21C5/46

CHEMISTRY; METALLURGY

Abstract

Claims

Description