JP2018024911A - Method for melting bullion adhered in ladle in molten iron preliminary treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for melting a bullion adhered in a ladle in a molten iron preliminary treatment capable of easily and surely removing a bullion adhered to a ladle bottom, a side wall and a free board part of a hot metal ladle.SOLUTION: There is provided a method for melting a bullion adhered in a ladle in a molten iron preliminary treatment can easily and surely remove the bullion adhered to almost all face of the hot metal ladle by a first process for melting the bullion adhered to a hot metal ladle side wall and a ladle bottom under a molten iron surface together with a desiliconization treatment by ejection of oxygen gas to a molten iron surface and discharge of inert gas into molten iron by a stirring mechanism, a second process for removing a desiliconized slag formed in the first process and a third process for dissolving the bullion adhered to the molten iron ladle free board part together with a desiliconization and decarbonization treatment by ejection of oxygen gas to the molten iron surface and discharge of the inert gas into the molten iron by the stirring mechanism after the second process, together with conducting a molten pig iron preliminary treatment.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for dissolving an ingot in a pan in hot metal preliminary treatment.

  In a hot metal pretreatment furnace such as a hot metal ladle, hot metal pretreatment such as desiliconization, dephosphorization, and decarburization is performed. These treatments are performed by, for example, so-called oxygen gas top blowing, in which a lance for oxygen blowing is inserted from the furnace port of the hot metal pretreatment furnace and high-speed oxygen is blown from the lance to the hot metal surface. When the hot metal pretreatment is performed by blowing up the oxygen gas, the hot metal having a high melting point may be scattered due to the collision of the oxygen gas with the hot metal surface, and may come into contact with the side wall near the pan opening. The contacted hot metal adheres as a bullion, and such bullion accumulates on the side wall near the pan opening, and becomes a dam when the hot metal is discharged, causing a residue in the furnace, generating smoke and iron loss. cause.

  Also, when the hot metal ladle receives low temperature hot metal of 1400 ° C or less after regular repairs, etc., not only the metal sticks to the side wall near the pan opening but also a large amount of metal from the bottom of the pan to almost the entire side wall. Adheres. Since the amount of hot metal is limited by the weight of the pot tare, which is the total weight of the pan and the hot metal, if the amount of metal is large, the amount of hot metal charged will be reduced and the amount of hot metal will decrease. Furthermore, although the amount of hot metal decreased is compensated with scrap, the hot metal processing time is prolonged because the hot metal temperature is lowered due to an increase in scrap. Alternatively, it is necessary to fill the hot metal in the second pan. In this case, it takes more time for the process until the steel is produced, and the production efficiency is significantly reduced.

  For this reason, the hot metal ladle where the adhesion of bullion has become noticeable is generally discontinued, transported to a repair shop, and the bullion is removed. Since it usually takes about 2 to 3 days for the transportation to the repair shop and the removal of the bullion, another hot metal ladle is required during that time. However, other hot metal ladle may not be prepared. In this case, it is necessary to continue to use the hot metal ladle to which the metal is attached, which promotes iron loss and the like. Furthermore, even if the bullion is removed at the repair shop, the bullion is recovered as a metal lump that is less valuable than hot metal, leading to a decrease in profit.

  As described above, when the metal bar adheres to the hot metal ladle, in addition to hindering the efficiency of the hot metal pretreatment, the equipment trouble and the profit are reduced.

  In view of such a problem, a hot metal dephosphorization method has been devised today in which an exhaust gas is brought into contact with an ingot in a hot metal pretreatment furnace to melt the ingot (see JP 2002-105522 A). .

  In the hot metal dephosphorization method described in this publication, when the maximum thickness of the bullion adhering to the ceiling portion of the kneading vehicle exceeds a predetermined value, the blast metal is heated to a high temperature by adjusting the blowing angle of the top blowing oxygen gas. It is characterized by allowing exhaust gas to reach. According to this hot metal dephosphorization method, it is said that the exhaust metal can be melted by the exhaust gas by allowing the exhaust gas to reach the metal, and thereby the thickness of the metal can be reduced.

  However, although this hot metal dephosphorization method is effective in reducing the thickness of the metal bar attached to the ceiling of the kneading car, it is difficult to effectively remove the metal bar attached to the entire surface of the hot metal pan. It is.

  Specifically, the hot metal ladle generally does not have a ceiling portion like a chaotic car, and even if exhaust gas can reach the bullion attached to the pan side wall above the hot metal surface, It is difficult for exhaust gas to directly reach the metal that adheres to the surface.

JP 2002-105522 A

  This invention is made in view of such a situation, and the adhesion | attachment place in the pan in the hot metal preliminary treatment which can remove the metal | base metal adhering to the pan bottom, side wall, and free board part of a hot metal pan easily and reliably. The purpose is to provide a gold dissolution method.

As a result of intensive studies, the inventors of the present invention have found that a first step of melting the bottom wall of the hot metal surface and the bottom of the hot metal with a heat generated by the desiliconization treatment under a predetermined condition, and a second step of gradually removing the desiliconization slag. A slag containing CO gas is formed on the hot metal surface when performing desiliconization / decarburization treatment under predetermined conditions, and the metal in the free board is dissolved by the combustion of the CO gas in the slag. In three steps, the inventors found that the bare metal adhering to almost the entire surface of the hot metal ladle could be removed, and completed the present invention.

但し、Ｘは、上吹きランスのノズル出口から溶銑面までの距離［ｍｍ］である。Ｙは、上吹きランスの中心軸からノズル出口最外周までの距離［ｍｍ］である。Ｚｃは、上吹きランスのノズルから吐出後のガスジェットのハードコア長さ［ｍｍ］である。θは、上吹きランスのノズル傾斜角度［°］である。αは、上記ガスジェットの広がり角度［°］である。 That is, in the hot metal preliminary treatment of the present invention made in order to solve the above problems, the method of dissolving the ingot in the pan uses a top blowing lance facing vertically downward and a stirring mechanism by discharging inert gas, This is a method for melting metal adhering to a pan in hot metal preliminary treatment for desiliconization and decarburization treatment of hot metal, in which oxygen gas is blown onto the hot metal surface by the upper blowing lance, and is not injected into the hot metal by the stirring mechanism. The first step of dissolving the degassing slag formed by the first step, the first step of melting the metal bar attached to the hot metal ladle side wall and the bottom of the hot metal pan, and the desiliconization treatment by discharge of the active gas And after the second step, the hot metal ladle freezing is performed together with desiliconization and decarburization treatment by the ejection of oxygen gas to the hot metal surface by the upper blow lance and the discharge of inert gas into the hot metal by the stirring mechanism. It has a third step of dissolving the metal that adheres to the board part, the hot metal surface collision pressure of the oxygen gas of the upper blowing lance in the first step is 1000 Pa or more and 1600 Pa or less, and the input energy by gas stirring is 100 W / t or more 200 W / t or less, supply amount of oxygen gas when the amount of metal in the pan is W [kg / t] is 0.028 W + 2.8 [Nm ³ / t] or more and 0.028 W + 4.0 [Nm ³ / T], the desiliconization slag that is gradually removed in the second step is 3.5 kg / t or more and 6.4 kg / t or less, and the hot metal surface of the oxygen gas by the top blowing lance in the third step collision pressure 1600Pa above 2000Pa less, the input energy due to gas stirring 200 W / t or 400W / t or less, the supply amount of oxygen gas is 2.5 Nm ³ / t or more 3.1Nm / T or less, the shortest distance between the upper lance that the central axis intersects the hot metal surface and the hot metal pot wall of R [mm], the upper lance center of which is calculated by the following equation (1) When the shortest distance between the point where the axis intersects the hot metal surface and the farthest point in the hot metal surface collision region of oxygen gas and the wall surface of the hot metal pan is I [mm], the I / R is 0.08 or more and 0.0. It is 15 or less.

However, X is the distance [mm] from the nozzle outlet of the top blowing lance to the hot metal surface. Y is the distance [mm] from the central axis of the top blowing lance to the outermost periphery of the nozzle outlet. Zc is the hard core length [mm] of the gas jet after being discharged from the nozzle of the top blowing lance. θ is the nozzle inclination angle [°] of the top blowing lance. α is a spread angle [°] of the gas jet.

In the hot metal preliminary treatment, the method for dissolving the metal in the pan is used for the hot metal pan in which a large amount of metal is attached to almost the entire surface of the pan as described above. Therefore, in the molten metal pre-treatment method in the hot metal pretreatment, the heat generated by the SiO ₂ generation by the desiliconization reaction is generated in the first step while suppressing the decarburization reaction in the first step. In the third step, the slag containing CO gas is formed beyond the wall surface of the hot metal ladle. It is important to form this slag in accordance with the height of the bare metal attached to the free board portion of the hot metal pan while preventing it.

In this regard, the method of dissolving the ingot in the pan in the hot metal pretreatment includes the hot metal surface collision pressure of the oxygen gas of the top blowing lance in the first step, the stirring input energy of the inert gas by the stirring mechanism, and the oxygen gas to the hot metal Since the supply amount is within the above range, the desiliconization process proceeds while suppressing the reaction between oxygen and carbon, and the metal attached to the pan side wall and the pan bottom below the hot metal surface is melted by the heat generated during the generation of SiO _2. Since the slow amount of desiliconized slag in the second step is within the above range, the amount of desiliconized slag necessary for the third step can be left in the pan, and the top blown in the third step Since the hot metal surface collision pressure of the oxygen gas of the lance, the stirring energy of the inert gas by the stirring mechanism, and the oxygen gas supply amount to the hot metal are within the above range, and the I / R is within the above range, CO Including gas The slag can be formed in accordance with the height of the bullion attached, and the bullion attached to the freeboard part of the hot metal pan can be removed. Metal can be dissolved.

  The “hot metal surface” refers to the surface of the hot metal in a stationary state where no treatment such as top blowing is performed. In addition, the “hot metal surface collision area” refers to a portion of the hot metal surface where the oxygen gas discharged from the upper blowing lance collides.

Further, “hot metal surface collision pressure of oxygen gas” means Ps [Pa] represented by the following formula (2).

In the above formula (2), C is a value represented by the following formula (3) using the ratio (Mach number) M of the discharge speed of the oxygen gas to the sound speed. X ^* is a dimensionless distance calculated by the following formula (4) using the outlet diameter D [mm] of the nozzle that discharges oxygen gas, and X ₀ ^* is defined by the following formula (5). It is a dimensionless virtual origin. P _{0 (X} ^* _{= 15)} is a value calculated by the following equation (6), and is an absolute pressure [Pa] at a dimensionless distance X ^* = 15.

The absolute pressure P _{0 (X} ^* _{= 0) at} the Mach number M and the dimensionless distance X ^* = 0 can be calculated by the following equations (7) and (8), respectively. Further, the nozzle outlet diameter D is generally determined so as to reduce the pressure loss, and can be calculated by the following equation (9) using the nozzle throat diameter d [mm].

Here, the meaning of each variable is as follows. The description of the same variable names as those already described is omitted. κ is the ratio of the constant pressure molar specific heat to the constant volume molar specific heat (specific heat ratio), and is 1.4 in the case of oxygen. P _atm is atmospheric pressure and is 101325 Pa. R is a gas constant and is 8314 Pa · m ³ / K / kmol. _Tg is the oxygen gas temperature [K] at the nozzle inlet of the top blowing lance and is room temperature (298 K). _Ac is the cross-sectional area [m ² ] of the nozzle throat portion of the top blowing lance. _mg is the molecular weight of oxygen gas and is 32. Q _Tm is the mass flow rate [kg / s] of the top blowing oxygen gas, and is calculated from the following formula (10) using the top blowing oxygen gas flow rate Q _T [Nm ³ / min].

The “stirring energy” is described in “Kazumi Mori, Masamichi Sano,“ Dynamics of Injection Metallurgy ”; Iron and Steel, Vol. 67 (1981), No. 6, pp. 687”. It means ε _B [W / t] represented by the following formula (11).

Here, the meaning of each variable is as follows. The description of the same variable names as those already described is omitted. Q _B is an inert gas flow rate [Nm ³ / min] of the stirring mechanism. T is the hot metal temperature [K]. W is the hot metal weight [t]. ρ is the hot metal density [kg / m ³ ]. g is a gravitational acceleration [m / s ² ], and is 9.8 m / s ² . h is the average depth [m] of hot metal in the pan.

Further, the hard core length Zc [mm] of the gas jet of the above formula (1) can be calculated using the following formula (12) using the nozzle pre-pressure Po [kgf / cm ² ]. Here, the pre-nozzle pressure Po can be calculated using the following equation (13).

Here, the meaning of each variable is as follows. The description of the same variable names as those already described is omitted. F _O2 is the top blowing oxygen gas velocity [Nm ³ / hr]. n is the number of nozzles of the top blowing lance. ε is a flow coefficient and is 0.85.

  As described above, the method for dissolving the ingot in the ladle in the hot metal pretreatment of the present invention can easily and reliably remove the ingot attached to the bottom surface, the side wall surface, and the free board portion of the hot metal ladle.

It is typical sectional drawing which shows the hot metal ladle used for the hot metal preliminary treatment which concerns on one Embodiment of this invention. It is typical sectional drawing which shows the hot metal ladle concerning the form different from the hot metal ladle of FIG. It is typical sectional drawing which shows the hot metal ladle concerning the form different from the hot metal ladle of FIG.1 and FIG.2. It is a typical end view which shows the hot metal ladle in the 1st process which melt | dissolves the stick side wall and hot metal bottom of the hot metal surface. It is a typical end view which shows the hot metal ladle in the 2nd process of slowing the desiliconization slag produced | generated at the 1st process. It is a typical end view which shows the hot metal ladle in the 3rd process which melt | dissolves the adhesion | attachment metal in a free board part. It is a typical fragmentary sectional view which shows the oxygen gas discharge state of the top blowing lance used for the hot metal preliminary treatment of FIG. FIG. 7 is a schematic top view showing a hot metal surface collision region of oxygen gas in FIG. 6.

  Hereinafter, embodiments of the present invention will be described in detail.

<Hot metal hot pot>
In the hot metal pretreatment, the method for melting the adhering metal in the pan is performed during hot operation using a hot metal pan for pretreatment of hot metal discharged from the blast furnace. Specifically, the method of dissolving the in-place adhering metal in the pan can be performed at an appropriate timing during the desiliconization process or the like in the hot metal preliminary process. By performing the hot metal operation in the hot metal pretreatment in the hot metal pretreatment process in this way, the hot metal refining process can be prevented from hindering the smooth implementation of the hot metal refining process, and the molten metal can be removed from the hot metal. Can be used as First, the hot metal ladle used in the hot metal pretreatment will be described.

  There is no particular limitation on the hot metal ladle used in the hot metal pretreatment process in the hot metal pretreatment, and any known hot metal ladle can be used. Examples of the hot metal ladle used in the method for dissolving the adhering ingot in the pan include the hot metal ladle shown in FIGS.

The hot metal ladle 1 of FIG. 1 is configured in a bottomed cylindrical shape having an opening in the upper part. In the hot metal ladle 1, hot metal M discharged from the blast furnace is stored. The hot metal ladle 1 has a hot metal discharge part 2 protruding outward at the upper part of the side wall. Moreover, the height of the side wall upper end of the hot metal ladle 1 is made substantially uniform. The vertical length from the upper surface of the bottom wall of the hot metal ladle 1 to the upper end of the side wall is not particularly limited, but can be, for example, about 2 m or more and 5 m or less. Moreover, it is although it does not specifically limit as an inside radius of the hot metal ladle 1 (average radius of the area | region enclosed by the inner surface of a side wall), For example, it can be set as about 1 m or more and 3 m or less. Furthermore, as the free board height L ₁ of the molten iron pan 1, but are not particularly limited, and is generally a degree or 2m or less 0.5 m. The “average radius in the pan” refers to the radius when converted into a perfect circle.

The hot metal ladle 3 of FIG. 2 is configured in a bottomed cylindrical shape having an opening at the top. In the hot metal ladle 3, hot metal M discharged from the blast furnace is stored. The hot metal ladle 3 has a hot metal discharge part 4 protruding outward at the upper part of the side wall. The height of the upper end of the side wall of the hot metal ladle 3 is higher in the vicinity of the hot metal discharge part 4 than in other parts. In the hot metal ladle 3, the vertical length from the hot metal surface to the upper end of the side wall located at the lowest position (that is, the vertical length from the hot metal surface to the upper end of the side wall other than the vicinity of the hot metal discharge part 4) is the free board height L. ₂ The vertical length from the upper surface of the bottom wall of the hot metal ladle 3 to the highest position of the upper end of the side wall and the average radius in the ladle of the hot metal ladle 3 can be the same as the hot metal ladle 1 of FIG. As the free board height L _2, it is not particularly limited, and is generally a degree or 1.5m below 0.5 m.

The hot metal ladle 5 of FIG. 3 is configured in a bottomed cylindrical shape having an opening at the top. In the hot metal ladle 5, hot metal M discharged from the blast furnace is stored. The hot metal ladle 5 has a hot metal discharge part 6 protruding outward at the upper part of the side wall. The height of the upper end of the side wall of the hot metal ladle 5 is lower in the portion having the hot metal discharge portion 6 than in other portions. In hot metal pan 5, the vertical length of the hot metal surface to the upper end of the molten iron discharge section 6 is free board height L _3. The vertical length from the upper surface of the bottom wall of the hot metal ladle 5 to the upper end of the side wall other than the hot metal discharge part 6 and the average radius in the ladle of the hot metal ladle 5 can be the same as those of the hot metal ladle 1 of FIG. As the free board height L _3, it is not particularly limited, and is generally a degree or 1.5m below 0.5 m.

<Hot metal pretreatment equipment>
Next, the hot metal pretreatment apparatus used in the hot metal pretreatment process will be described. The hot metal pretreatment device 11 of FIG. 4 includes a hot metal ladle 1, an upper blowing lance 12, and an injection lance 13. The hot metal pretreatment device 11 performs desiliconization and decarburization processing on the hot metal M stored in the hot metal ladle 1. In addition, although the hot metal pretreatment apparatus 11 of FIG. 4 is provided with the hot metal ladle 1, it is not specifically limited as a hot metal ladle used with the said adhesion | attachment metal melt | dissolution method in the said pan, For example, the hot metal ladle 3 of FIG. Alternatively, the hot metal ladle 5 shown in FIG. 3 can be used.

  The hot metal ladle 1 of FIG. 4 has shown the state after the hot metal preliminary process 1 or more times was performed, and the metal B has adhered to the inner side of the pan. Specifically, the metal B is attached to the entire circumference of the bottom of the hot metal ladle 1, the side wall of the pan, and the free board portion.

  The hot metal M discharged from the blast furnace generally contains 0.2 mass% or more and 1.0 mass% or less of silicon or 4.5 mass% or more and 4.8 mass% or less of carbon. This silicon and carbon are reduced by desiliconization and decarburization processing in the hot metal pretreatment device 11. At this time, an auxiliary material such as CaO may be added to the hot metal M for the purpose of adjusting the basicity after the desiliconization and decarburization treatment. In the method for dissolving the ingot in the pot, the desiliconization reaction is promoted while suppressing the decarburization reaction in the first step and the desiliconization / decarburization reaction is promoted in the third step, as described later. The silicon contained in is preferably 0.8 mass% or more and 1.1 mass% or less.

  In order to perform the desiliconization and decarburization processes, first, the hot metal M is charged into the hot metal ladle 1 and an auxiliary material such as CaO is charged. Next, an upper blowing lance 12 is inserted from the opening of the hot metal ladle 1, and oxygen gas G is blown onto the hot metal M from the upper blowing lance 12. At the same time, an inert gas is blown into the hot metal M from an injection lance 13 inserted into the hot metal M from the opening of the hot metal pan 1. By blowing the inert gas into the hot metal M in this way, the hot metal M is stirred, and the oxygen gas G sprayed on the hot metal M reacts with silicon and carbon in the hot metal M to perform desiliconization treatment and decarburization treatment. Is called.

(Top blowing lance)
The top blowing lance 12 is inserted from the opening of the hot metal ladle 1 as described above, and its tip is disposed above the hot metal M and faces vertically downward. The upper blowing lance 12 has n nozzles disposed obliquely downward and at substantially equal angular intervals at the tip. Although it does not specifically limit as the number of nozzles of the top blowing lance 12, For example, they can be 2 or more and 5 or less. The height of the top blowing lance 12 (distance from the nozzle outlet of the top blowing lance 12 to the hot metal surface) depends on the hot metal surface collision pressure desired when the oxygen gas G is blown onto the hot metal M, but will be described later. In the first step, it can be set to 700 mm or more and 1500 mm or less, and in the third step, 3000 mm or more and 4500 mm or less.

  The top blowing lance 12 discharges oxygen gas G from each nozzle 21 as shown in FIG. The shape of the nozzle 21 is a substantially truncated cone, and the nozzle throat 21a side is narrow and the nozzle outlet 21b side is wide. The nozzle 21 has a central axis connecting the center of the nozzle throat 21a and the center of the nozzle outlet 21b with an inclination angle θ [°] outward from the central axis N of the upper blowing lance 12 ( The inclination angle of the central axis connecting the center of the nozzle throat 21a and the center of the nozzle outlet 21b with respect to the central axis N of the upper blowing lance 12 is also referred to as “nozzle inclination angle”).

  The oxygen gas G discharged from the nozzle 21 travels substantially straight in the jet core region where the central flow velocity is equal to or higher than the sonic velocity, and then collides with the hot metal surface while spreading at a certain spread angle α. A part of the collided oxygen gas G is supplied into the hot metal M. In FIG. 7, X represents the distance [mm] from the nozzle outlet 21b of the top blowing lance 12 to the molten iron surface, and Y represents the distance [mm] from the center axis N of the top blowing lance 12 to the outermost periphery of the nozzle outlet 21b. Zc represents the hard core length (the length of the jet core region) of the gas jet after being discharged from the nozzle 21 of the upper blowing lance 12.

  FIG. 8 shows a hot metal surface collision region M1 due to the oxygen gas G discharged from the upper blowing lance 12 having three nozzles. As shown in FIG. 8, the hot metal surface collision region M <b> 1 of the oxygen gas G has a substantially circular shape, and there are the same number as the number of normal nozzles 21. Here, the shortest distance between the point N0 where the central axis N of the top blowing lance 12 intersects the hot metal surface and the wall surface 1a of the hot metal ladle 1 is the distance R [mm]. Further, the shortest distance between the point M10 where the central axis N of the top blowing lance 12 intersects the hot metal surface and the farthest point M10 in the hot metal surface collision region M1 of the oxygen gas G and the wall surface 1a of the hot metal ladle 1 is the distance I [mm]. It is. This distance I can be calculated by the above formula (1) as shown in FIG. 7 by approximating the hot metal surface and the hot metal surface collision region M1 to a perfect circle.

(Injection Lance)
The injection lance 13 is inserted from the opening of the hot metal ladle 1 as described above, and is disposed so that its tip is located in the hot metal M. The injection lance 13 constitutes a stirring mechanism that stirs the molten iron M by discharging an inert gas. By blowing an inert gas from the injection lance 13 into the hot metal M, the hot metal M is stirred, and the reaction efficiency between the oxygen gas G and silicon and carbon described above is increased. Examples of the inert gas include nitrogen gas, argon gas, etc. Among them, inexpensive nitrogen gas is preferable.

(Bullion)
The bare metal B is a hot metal having a high melting point attached to the pan bottom, the pan side wall, and the free board portion in the hot metal pretreatment. When the hot metal ladle receives low-temperature hot metal of 1400 ° C. or lower after regular repairs, a large amount of metal is attached to almost the entire surface of the side wall from the bottom of the pan. Also, the hot metal M scatters due to collision with the hot metal surface of the oxygen gas G discharged from the plurality of nozzles 21 of the upper blowing lance 12 or stirring of the hot metal M by the inert gas discharged from the injection lance 13. It is formed by adhering to. When the free board height L1 is ₁ , the free metal B of the free board part adheres in a range of about 0.8 in the vertical direction from the hot metal surface. That is, the metal B adheres to a region of about 1.6 m vertically upward from the hot metal surface.

<Method for dissolving metal in the pot in hot metal pretreatment>
Next, a method for dissolving the adhering metal in the pan in the hot metal pretreatment using the hot metal pretreatment device 11 will be described. The method for dissolving the ingot in the pot is performed at an appropriate timing during the desiliconization process or the like in the hot metal preliminary process as described above. As a minimum of the frequency which performs the adhesion metal adhesion method in the pan, once for 20 charges is preferred, and once for 25 charges is more preferred. On the other hand, as an upper limit of the frequency which performs the adhesion | attachment metal | metal | money melt | dissolution method in the said pan, once for 40 charges is preferable and 1 time for 35 charges is more preferable. If the frequency of performing the method of dissolving the adhering ingot in the pan is less than the lower limit, the hot metal pretreatment efficiency per hot metal pretreatment may be reduced. On the other hand, if the frequency of performing the method of dissolving the ingot in the pan exceeds the upper limit, the pan tare weight increases due to the ingot in the hot ladle 1, and there is a possibility that the amount of hot metal necessary for the hot metal pretreatment cannot be secured. is there.

  In the hot metal pretreatment, the method of dissolving the metal in the pan is to remove oxygen gas onto the hot metal surface with an upper blowing lance, and to remove the inert gas into the hot metal with a stirring mechanism. Hot metal surface by the top blowing lance after the first step of melting the metal that adheres to the hot metal ladle side wall and the pan bottom, the second step of slowing the desiliconized slag formed by the first step, and the second step And a third step of dissolving the bare metal adhering to the hot metal ladle freeboard part together with desiliconization and decarburization treatment by jetting oxygen gas into the hot metal and discharging inert gas into the hot metal by the stirring mechanism.

(First step)
In the first step, as shown in FIG. 4, oxygen gas G is supplied from the top blowing lance 12 into the hot metal M to advance the desiliconization reaction, and the amount of heat generated during the generation of SiO ₂ is used to lower the surface of the hot metal. The desiliconized slag S is formed on the hot metal surface while melting the metal attached to the side wall and the bottom of the pan.

  In the first step, the lower limit of the hot metal surface collision pressure of the oxygen gas G by the top blowing lance 12 is 1000 Pa, preferably 1200 Pa, and more preferably 1400 Pa. The upper limit of the hot metal surface collision pressure is 1600 Pa or less. If the upper limit hot metal surface collision pressure is less than the above lower limit, the desiliconization reaction is not promoted, so that sufficient heat generation cannot be generated and the desiliconization slag is not sufficiently generated. On the other hand, when the upper limit is exceeded, the decarburization reaction is promoted together with the desiliconization reaction. The purpose of the first step is to dissolve the metal using the heat generated by the desiliconization reaction and to form desiliconized slag, and it is not necessary to generate CO gas. Unnecessary decarburization reaction reduces the carbon concentration in the hot metal, and there is a risk that the decarburization reaction and CO gas combustion in the third step described later will be insufficient.

  Moreover, the lower limit of the stirring input energy of the inert gas by the stirring mechanism is 100 W / t, and preferably 150 W / t. On the other hand, the upper limit of the stirring input energy is 200 W / t. If the stirring input energy is less than the lower limit, the desiliconization reaction is not promoted, so that sufficient heat generation cannot be generated, and desiliconization slag is not sufficiently generated. On the other hand, when the upper limit is exceeded, the decarburization reaction is promoted together with the desiliconization reaction. The purpose of the first step is to dissolve the metal using the heat generated by the desiliconization reaction and to form desiliconized slag, and it is not necessary to generate CO gas. Unnecessary decarburization reaction reduces the carbon concentration in the hot metal, and there is a risk that the decarburization reaction and CO gas combustion in the third step described later will be insufficient. In addition, the stirring energy of the inert gas by the stirring mechanism can be adjusted by controlling the flow rate of the inert gas blown from the injection lance 13, the height position of the inert gas blown, and the like.

Furthermore, the lower limit of the oxygen gas supply amount is 0.028 W + 2.8 [Nm ³ / t], where the amount of metal in the pan is W [kg / t], and 0.028 W + 3.2 [Nm ³ / t]. t] is preferable, and 0.028W + 3.6 [Nm ³ / t] is more preferable. On the other hand, the upper limit of the oxygen gas supply amount is 0.028 W + 4.0 [Nm ³ / t]. If the oxygen gas supply amount is less than the lower limit, the desiliconization reaction is not promoted, so that sufficient heat generation cannot be generated and the desiliconization slag is not sufficiently generated. On the other hand, if the above upper limit is exceeded, the refractory in the pan may be damaged.

(Second step)
Next, in a 2nd process, as shown in FIG. 5, a part of desiliconization slag S produced | generated at the 1st process is slowed down. In the 3rd process mentioned later, in order to melt | dissolve ingot B adhering to the free board part above the hot metal surface which cannot be removed in the 1st process, it is necessary to form slag S2 generated by desiliconization and decarburization reaction . However, since the desiliconization slag S produced in the first step is large, it is necessary to gradually remove unnecessary desiliconization slag while leaving the amount necessary for the third step. The lower limit of the amount of desiliconized slag that is gradually reduced is 3.5 kg / t, preferably 4.7 kg / t, and more preferably 5.5 kg / t. On the other hand, the upper limit of the amount of desiliconized slag to be gradually added is 6.4 kg / t. If the amount of desiliconized slag that is gradually reduced is less than the lower limit, the height of slag S2 forming (hereinafter sometimes referred to as “slag forming”) required in the next process cannot be secured. On the other hand, if the above upper limit is exceeded, the height of the slag foaming may overflow beyond the free board and further the upper end of the pan side wall, which may cause iron loss, equipment damage, operational troubles, and the like.

(Third process)
In the third step, the metal B attached to the free board portion above the hot metal surface that cannot be removed in the first step is melted. Unlike the first step, by reacting silicon and carbon in the hot metal simultaneously, slag forming is formed so as to cover the bare metal adhering to the free board portion, and in the formed slag S2, two CO gases are formed. Next, the adhering metal is melted with slag that has been burned and heated.

  In the third step, as shown in FIG. 6, slag containing CO gas is formed by desiliconization / decarburization reaction, and the CO gas is secondarily burned, so that the metal B is made of slag S2 that has become high temperature. Dissolve. In the third step, in order to efficiently perform secondary combustion while maintaining the height of the slag S2, by supplying oxygen gas G from the top blowing lance 12 into the hot metal M, decarburization treatment and CO in the slag S2 are performed. Promotes secondary combustion of gas.

  The lower limit of the hot metal surface collision pressure of the oxygen gas G by the top blowing lance 12 in the third step is 1600 Pa, preferably 1700 Pa, and more preferably 1900 Pa. The upper limit of the hot metal surface collision pressure is 2000 Pa or less. If the upper limit hot metal surface collision pressure is less than the lower limit, the desiliconization reaction and the decarburization reaction are not promoted, so that the slag S2 cannot be sufficiently formed. On the other hand, when the above upper limit is exceeded, the hot metal scatters and the secondary combustion efficiency in the formed slag may deteriorate.

  The lower limit of the stirring input energy of the inert gas by the stirring mechanism is 200 W / t, preferably 280 W / t, more preferably 350 W / t. On the other hand, the upper limit of the stirring input energy is 400 W / t. If the stirring input energy is less than the lower limit, the desiliconization reaction and the decarburization reaction are not promoted, so that the slag S2 cannot be sufficiently formed. On the other hand, when the above upper limit is exceeded, the hot metal scatters violently, and the secondary combustion efficiency in the formed slag may deteriorate.

Further, the lower limit of the oxygen gas supply amount is 2.5 Nm ³ / t, preferably ^{2.7Nm 3 / t, 2.9Nm 3 /} t is more preferable. On the other hand, the upper limit of the oxygen gas supply amount is 3.1 Nm ³ / t. If the oxygen gas supply amount is less than the lower limit, the desiliconization reaction and the decarburization reaction are not promoted, so that the slag S2 cannot be sufficiently formed. On the other hand, if the above upper limit is exceeded, the height of the slag foaming may overflow beyond the free board and further the upper end of the side wall of the pan, which may cause iron loss, equipment damage, and operational troubles.

  R [mm] is the shortest distance between the point N0 where the central axis N of the top blowing lance 12 intersects the hot metal surface and the wall surface 1a of the hot metal ladle 1 in the metal melting step, and the central axis N of the upper blowing lance 12 is the hot metal surface. Assuming that the shortest distance between the intersecting point N0 and the farthest point M10 in the hot metal surface collision region M1 of the oxygen gas G and the wall surface 1a of the hot metal ladle 1 is I [mm], the lower limit of I / R is 0.08. 0.10 is more preferable. On the other hand, the upper limit of the I / R is 0.15. If the I / R is not less than the lower limit, the fire point may be too close to the wall surface 1a, which may cause refractory melting. On the other hand, when the I / R exceeds the upper limit, the temperature of the slag S2 is not sufficiently increased, and the base metal B may not be sufficiently dissolved.

<Advantages>
In the hot metal pretreatment, the molten metal adhering to the pan is in the first step, the hot metal surface collision pressure of the oxygen gas G of the top blowing lance 12, the stirring energy of the inert gas by the stirring mechanism, and the oxygen gas G to the hot metal M Since the supply amount is within the above range, the desiliconization process proceeds while suppressing the reaction between oxygen and carbon, and the ingot B attached to the pan side wall and the pan bottom below the hot metal surface is generated by the heat generated during the generation of SiO _2. Since the slow amount of desiliconized slag S in the second step is within the above range, the amount of desiliconized slag necessary for the third step can be left in the pan, The hot metal surface collision pressure of the oxygen gas G of the upper blowing lance 12, the stirring energy of the inert gas by the stirring mechanism, and the supply amount of the oxygen gas G to the hot metal M are within the above range, and the I / R is within the above range. Because C The slag S2 containing O gas is formed in accordance with the height of the adhesion of the metal, and the metal B attached to the freeboard portion of the hot metal pan while preventing the slag S2 from being formed beyond the wall surface of the hot metal pan 1. Can be removed, and the above process can easily and reliably dissolve the bare metal attached to almost the entire surface of the pan.

[Other Embodiments]
In addition, the ladle adhesion metal dissolution method according to the present invention can be carried out in a mode in which various changes and modifications are made in addition to the above mode. For example, the hot metal ladle used in the method for dissolving the adhering ingot in the pan is not particularly limited, and it is possible to use a hot metal pan other than the hot metal ladle shown in FIGS.

  Further, the stirring mechanism does not need to be constituted only by the injection lance, and other stirring devices may be used, or the injection lance and other stirring devices may be used in combination.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Examples 1-38, Comparative Examples 1-133)
Using the hot metal ladle of FIGS. 1 to 3, the ingot hot metal melting method by the hot metal pretreatment of Examples 1 to 38 and Comparative Examples 1 to 133 was performed. The processing procedure is shown below. Note that the volume of the hot metal ladle used was 54 m ³ . Moreover, about the shape of the hot metal ladle used, the hot metal ladle 1 of FIG. 1 is set to A, the hot metal ladle 3 of FIG. 2 is set to B, and the hot metal ladle 5 of FIG. In addition, "free board height" shown in Tables 1 to 4 refers to the vertical distance from the hot metal surface to the lowest position in the upper end of the side wall including the hot metal discharge part of the hot metal pan.

  The top blowing lances used in Examples 1 to 38 and Comparative Examples 1 to 133 were the number of nozzles n = 4, nozzle throat diameter d = 18 mm, nozzle outlet diameter D = 20 mm, nozzle inclination angle θ = 9 °, after nozzle discharge And the distance Y from the central axis of the upper blowing lance to the outermost periphery of the nozzle outlet is 83 mm. Further, the number of injection lance holes used in Examples 1 to 38 and Comparative Examples 1 to 133 is one. Furthermore, in Examples 1-38 and Comparative Examples 1-133, nitrogen gas was used as an inert gas to be stirred.

(Procedure before implementation of the method for melting metal adhering to the pot)
First, hot metal was prepared in a hot metal pan. The hot metal ladle used was one in which the bare metal adhered to almost the entire inner surface, and the adhesion amount of the bare metal was as shown in Tables 1 to 4. Moreover, the weight, carbon concentration, and silicon concentration of the hot metal used were as shown in Tables 1 to 4. Further, CaO was added to the hot metal as an auxiliary material for adjusting the basicity. The input amount of CaO was as shown in Tables 1 to 4. The temperatures before and after the hot metal treatment were as shown in Tables 1 to 4.

  Moreover, after measuring the average radius in the hot pot of the hot metal ladle, the hot metal depth was determined from the average radius in the hot pot and the amount of hot metal by the following formula (14). Further, the level of the stationary hot metal surface was measured using a microwave level meter, and the free board height was obtained from the minimum distance between the hot metal surface level and the upper end of the hot metal ladle side wall. Tables 1 to 4 show the average radius of the hot metal ladle, the hot metal depth and the freeboard height.

(Procedure in the first step)
The first step was performed by adjusting the amount of oxygen gas supplied and the hot metal surface collision pressure Ps of oxygen gas in Examples 1 to 38 and Comparative Examples 1 to 133 to be in Tables 5 to 8. The hot metal surface collision pressure of oxygen gas was adjusted by the top blowing lance height X. The top lance height is measured using the microwave level described in Japanese Examined Patent Publication No. 4-81734, and the hot metal surface level after the hot metal charging is measured, and the hot metal surface level and the height of the discharge port of the oxygen lance are calculated. The difference between the two was the top blowing lance height. The top blowing oxygen gas velocity F _O2 was as shown in Tables 5 to 8.

Here, the oxygen gas supply amount is determined as 0.028 W + 2.8 to 4.0 [Nm ³ / t], where the amount of metal in the pan is W [kg / t] as described above, Taking Example No. 1 as an example, since W = 69 kg / t, the oxygen gas supply amount is 5.5 Nm ³ /t=0.028×69+3.6, which indicates the above formula range.

Further, the inert gas flow rate Q _B was adjusted so that the stirring input energy ε _B became a desired value. Tables 5 to 8 show the inert gas flow rate Q _B and the stirring input energy ε _B.

  Furthermore, by measuring and analyzing the hot metal after the first step by measuring the hot metal after the first step, the amount of silicon removal was determined by the difference from the Si in the hot metal before the first step in Tables 1 to 4. . Tables 5 to 8 show Si in the hot metal after the first step.

  It shows in Table 5-Table 8 about the slow amount of a 2nd process. The amount of sag was determined by measuring the pan weight before and after sag.

(Procedure in the third step)
Subsequently, the third step was performed by adjusting the supply amount of the top blowing oxygen gas and the hot metal surface collision pressure Ps of the oxygen gas to be in Tables 9 to 12. The hot metal surface collision pressure of oxygen gas was adjusted by the top blowing lance height X. Moreover, the top blowing oxygen gas velocity in Examples 1-38 and Comparative Examples 1-133 was as shown in Tables 9-12. Furthermore, the inert gas flow rate Q _B and the stirring input energy ε _B are as shown in Tables 9 to 12.

Further, the shortest and the nozzle before the pressure P _O and the furthest point and the hot metal pot wall central axis of the top-blown lance hardcore length Z _C of the gas jet in the molten pig iron surface collision area of the oxygen gas from the point of intersection with the hot metal surface The value (I / R) obtained by dividing the distance I by the shortest distance R between the point at which the central axis of the top lance intersects the hot metal surface and the wall surface of the hot metal pan was adjusted to be a desired value. Tables 9 to 12 show the hard core length of the gas jet, the pressure before the nozzle, the shortest distance between the position where the periphery of the hot metal surface is closest to the wall surface of the hot metal pan, and the wall surface of the hot metal pan, and I / R. The shortest distance R between the point where the central axis of the top blowing lance intersects the hot metal surface and the wall surface of the hot metal pan is the same value as the furnace radius in Tables 1 to 4. In the table, the shortest distance I is described as “the shortest distance between the hot metal surface collision region and the wall surface”.

  Furthermore, Si in the hot metal after the bullion melting process was measured by sampling and analysis of the hot metal after the bullion melting process. The measurement results are shown in Tables 9 to 12.

[Content of evaluation]
<Adhesive metal on the side wall and bottom of the hot metal surface>
After all the steps, the difference between the weight of the empty pan after treatment and the weight of the empty pan before adhesion of the bullion was obtained, and the presence or absence of adhesion of the bullion on the side wall of the pan below the hot metal surface and the bottom of the pan was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 13 and Table 14.
A: There is no difference between the weight of the empty pot after the treatment and the weight of the empty pot before the metal adhesion after the whole process.
B: There is a difference between the weight of the empty pot after the treatment and the weight of the empty pot before the metal adhesion after all the steps.

<Adhesion bullion on free board>
After the whole process, the entire circumference of the wall surface of the hot metal ladle in the region higher than the hot metal surface was visually confirmed, and the presence or absence of adhesion of the metal was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 13 and Table 14.
A: Unevenness is not confirmed in the free board part.
B: Unevenness is confirmed in the free board portion.

<Refractory damage>
After all the steps, the entire circumference of the wall surface of the hot metal ladle was visually confirmed, and the presence or absence of refractory damage was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 13 and Table 14.
A: A brick joint is not confirmed.
B: A brick joint is confirmed.

<Overflow>
The presence or absence of overflow in the third step was confirmed visually and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 13 and Table 14.
A: Overflow is not confirmed.
B: Overflow is confirmed.

<General>
When the evaluation of the adhesion of the bullion on the side wall and the bottom of the hot metal surface, the adhesion of the bullion on the free board part, the refractory damage and the overflow were all A, the overall evaluation was A. On the other hand, when any one or more of the above-mentioned metal adhesion, refractory damage and overflow is B, the overall evaluation is B. The evaluation results are shown in Table 13 and Table 14.

  As shown in Table 13 and Table 14, the overall evaluation of Examples 1 to 38 is A, and the side wall of the pan below the hot metal surface and the bottom metal adhesion of the pan bottom, the bottom metal adhesion of the free board part, refractory damage and overflow. All are A. On the other hand, Comparative Examples 1 to 133 have an overall evaluation of B, and any one or more of ladle adhesion on the ladle side wall and ladle bottom below the hot metal surface, ladle adhesion on the free board part, refractory damage and overflow is present. B. That is, from Examples 1 to 38, the hot metal surface collision pressure of the oxygen gas of the top blowing lance in the first step, the stirring energy of the inert gas by the stirring mechanism, the supply amount of oxygen gas to the hot metal, the release in the second step The gradual amount of silica slag, the hot metal surface collision pressure of the oxygen gas of the top blowing lance in the third step, the stirring gas input energy of the inert gas by the stirring mechanism, the supply amount of oxygen gas to the hot metal, and the above I / R It turns out that it can fully melt | dissolve and remove the metal | base metal adhering to the whole surface of a hot metal ladle, suppressing generation | occurrence | production of the refractory material in a pan and overflow by setting it as the range.

  In more detail, Comparative Nos. 1 and 12 indicate that the hot metal surface collision pressure of the oxygen gas in the first step was too small, so that the desiliconization reaction was not promoted and sufficient heat was not generated. It is thought that the attached metal on the side wall and the bottom of the pot remains. On the other hand, in Comparative No. 11, it is considered that the oxygen gas collision pressure in the first step was too large and heat generation due to the desiliconization reaction was excessive, resulting in damage to the refractory.

  In comparison number 33, it is considered that the stirring input energy in the first step was too large, and the refractory was damaged.

  In comparison number 24, it is considered that the oxygen gas supply amount in the first step was too large, and the refractory was damaged. On the other hand, since the oxygen gas supply amount in a 1st process is too small for the comparison number 37, it is thought that the deposit side metal under the hot metal surface and the pan bottom remain.

  In Comparative No. 25, since the amount of slag in the second step is too small, it is considered that the slag is not sufficiently formed and the adherence metal of the free board portion remains. On the other hand, since the comparative number 20 has too much slow slag amount in the second step, it is considered that the slag is excessively formed and overflow occurs.

  In comparison number 56, the hot metal surface collision pressure of the oxygen gas in the third step is considered to be too high, so that the hot metal is scattered on the wall surface, and the adherence metal of the free board portion is generated. On the other hand, in comparison number 13, it is considered that the molten metal collision pressure of the oxygen gas in the third step is too small, so that the slag is not sufficiently formed and the adherence metal of the free board portion remains.

  In Comparative No. 15, the gas stirring input energy in the third step is too low, so it is considered that the slag is not sufficiently formed and the adherence metal of the free board portion remains. On the other hand, it is considered that the comparative number 36 has excessive gas stirring input energy in the third step, so that the slag is excessively formed and an overflow occurs.

  In comparison number 64, it is considered that the amount of oxygen gas supplied in the third step is too small, so that the slag is not sufficiently formed and the adherence metal of the free board portion remains. On the other hand, in comparison number 120, since the amount of oxygen gas supplied in the third step is too large, the slag is excessively formed to cause overflow, and it is considered that the refractory is damaged.

  In comparison No. 5, since the I / R is too small, the temperature of the slag is not sufficiently increased, and it is considered that the adhered metal on the free board portion cannot be dissolved. On the other hand, it is considered that the comparative number 116 is damaged in the refractory because the I / R is too large.

<Examination of the effect of the method for melting metal adhering to the pot>
It calculated about the decrease in the production amount when the pot weight increased due to the adhesion of the metal, when the method of dissolving the metal in the pot in the hot metal preliminary treatment was performed and when the method of dissolving the metal in the pot was not performed. . At the same time, the damage rate of the refractory is measured to confirm whether there is any burden on the pot refractory and whether there is damage to the surrounding equipment due to the overflow of the formed slag. It was confirmed whether there was any cost burden or shutdown. The evaluation results are shown in Table 15.

  As shown in Table 15, in the case where the method for dissolving the adhering ingot in the pot is not carried out, the average production of 15 ch is reduced by 24%, whereas in the case where it is carried out, only 3% is produced. In addition, even when the method of dissolving the adhering ingot in the pan is performed, the damage rate of the pan refractory proceeds by 0.01 mm / ch compared to the case where it is not performed, and the refractory is not frequently replaced. . Furthermore, the hot metal surface collision pressure of the upper blowing lance in the third step, the stirring gas input energy of the inert gas by the stirring mechanism, the oxygen gas supply amount to the hot metal, and the I / R are within the above ranges. Therefore, the slag will not overflow, so there will be no damage to the surrounding equipment and the operation will not be stopped.

  As explained above, the method of dissolving the ingot in the hot metal pretreatment of the present invention can easily and reliably remove the metal attached to the bottom surface, the side wall surface and the freeboard portion of the hot metal pan, It is suitable as a method for suppressing the occurrence of iron loss while maintaining smooth implementation of the hot metal refining process.

1,3,5 Hot metal ladle 1a Hot metal ladle wall surface 2,4,6 Hot metal discharge part 11 Hot metal pretreatment device 12 Top blowing lance 13 Injection lance 21 Nozzle 21a Nozzle throat 21b Nozzle outlet B Metal B G Oxygen gas M Hot metal M1 Hot metal surface Collision area M10 The farthest point in the molten metal collision area of the oxygen gas from the point where the center axis of the top blowing lance intersects the hot metal surface N The top blowing lance central axis N0 The point where the central axis of the top blowing lance intersects the hot metal surface S, S2 Slug

Claims (1)

A method for dissolving metal adhering in a pan in a hot metal pretreatment in which desiliconization and decarburization treatment are performed on a hot metal ladle using a top blowing lance that faces vertically downward and a stirring mechanism by discharging an inert gas,
In addition to desiliconization treatment by blowing out oxygen gas to the hot metal surface by the top blowing lance and discharging inert gas into the hot metal by the stirring mechanism, the metal bar attached to the hot metal ladle side wall and the bottom of the hot metal ladle First step to dissolve,
A second step of gradually removing the desiliconized slag formed in the first step; and after the second step, an oxygen gas is jetted onto the hot metal surface by the upper blowing lance and into the hot metal by the stirring mechanism. Having a third step of melting the bare metal adhering to the hot metal ladle freeboard portion together with desiliconization and decarburization treatment by discharge of inert gas,
The hot metal surface collision pressure of oxygen gas of the upper blowing lance in the first step is 1000 Pa to 1600 Pa,
Input energy by gas stirring is 100 W / t or more and 200 W / t or less,
The supply amount of oxygen gas when the amount of metal in the pan is W [kg / t] is 0.028 W + 2.8 [Nm ³ / t] or more and 0.028 W + 4.0 [Nm ³ / t] or less. Yes,
The desiliconization slag that is gradually reduced in the second step is 3.5 kg / t or more and 6.4 kg / t or less,
The hot metal surface collision pressure of the oxygen gas by the upper blowing lance in the third step is 1600 Pa or more and 2000 Pa or less,
Input energy by gas stirring is 200 W / t or more and 400 W / t or less,
The supply amount of oxygen gas is not more than 2.5 Nm ³ / t or more 3.1Nm ³ / t,
The shortest distance between the point at which the central axis of the top blowing lance intersects the hot metal surface and the wall surface of the hot metal pan is R [mm], and the central axis of the top blowing lance calculated by the following equation (1) is the hot metal surface. When the shortest distance between a point farthest from the intersecting point in the hot metal surface collision region of the oxygen gas and the wall surface of the hot metal pan is I [mm], the hot metal reserve having an I / R of 0.08 to 0.15 A method for dissolving metal in the pot in processing.

However, X is the distance [mm] from the nozzle outlet of the top blowing lance to the hot metal surface. Y is the distance [mm] from the central axis of the top blowing lance to the outermost periphery of the nozzle outlet. Zc is the hard core length [mm] of the gas jet after being discharged from the nozzle of the top blowing lance. θ is the nozzle inclination angle [°] of the top blowing lance. α is a spread angle [°] of the gas jet.

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