JP5855477B2 - Hot metal refining method - Google Patents

Description

  The present invention relates to a hot metal refining method for desiliconization and desulfurization of hot metal.

As is well known, the hot metal produced in the blast furnace is loaded into a kneading car or a ladle for conveyance, and then transferred to a converter process for adjusting the components of the hot metal. In the ladle charged with hot metal, a refining agent is supplied to the hot metal to perform desiliconization, dephosphorization, and desulfurization to preliminarily perform hot metal component adjustment processing (hot metal pretreatment process).
Patent documents disclosing the technology in this hot metal pretreatment process include the following.

  Patent Documents 1 to 3 disclose techniques for performing hot metal preliminary treatment and secondary refining treatment in a ladle. A method of desiliconizing hot metal while supplying a gaseous oxygen source is disclosed, and stirring gas or stirring gas and powder are blown into the bath from a bottom blowing nozzle or immersion lance provided in the container, and the bath is stirred. It is disclosed.

  Patent Documents 4 to 7 disclose a technique for defining an installation position of an oxygen lance, an injection lance, and the like in hot metal preliminary treatment and secondary refining treatment. A secondary refining method for molten steel into which inert gas is blown, where the inert gas is blown into the molten steel from a gas blowing lance immersed in the molten steel, and the position surrounding the surface of the molten steel where the blown inert gas rises A dip tube is disposed in the secondary tube of the molten steel in which the lower end of the dip tube is immersed in the molten steel surface, and oxygen gas is blown from the oxygen nozzle disposed in the middle of the gas blowing lance to the molten steel surface in the space surrounded by the dip tube. A refining method is disclosed.

Japanese Patent Laid-Open No. 2003-41312 JP 2000-73114 A JP 2004-292924 A JP 2005-23333 A JP-A-6-41312 JP 2008-231477 A JP 60-234906 A

As described above, a number of patent documents disclosing the technology in the hot metal pretreatment process have been disclosed, but the hot metal discharged from the blast furnace can be efficiently processed continuously in the same ladle with desiliconization and desulfurization. Few technologies have been disclosed.
For example, Patent Documents 1 to 3 are not technologies that clearly define the installation positions of oxygen lances and injection lances in the hot metal preliminary treatment, and the fact is that highly efficient refining treatment cannot be performed. is there.

Patent Documents 4 to 6 only specify a part of the installation position and operating conditions of the oxygen lance and injection lance, and it is unclear how other operating conditions should be applied even if they are applied on the actual site. In addition, as a result, there is a possibility that highly efficient refining treatment cannot be performed.
Patent Document 7 discloses the installation position and operating conditions of the oxygen lance and injection lance to a certain extent, but the refining vessel is a hot metal pretreatment furnace (converter), and the operating conditions in the refining process using a ladle. It is not a regulation.

  Therefore, in view of the above-mentioned problems, the present invention efficiently refining the hot metal in the vessel using the injection lance and oxygen lance without removing slag when switching from desiliconization to desulfurization. It aims at providing the refining method of the hot metal which can be performed.

In order to achieve the above-described object, the present invention takes the following technical means.
In the hot metal refining method according to the present invention, molten iron containing 0.25 mass% or more of [Si] is charged into a ladle, oxygen is blown from the oxygen lance to the molten iron in the ladle, and the oxygen lance is transferred from the injection lance. A hot metal refining method for performing desiliconization and desulfurization of hot metal by blowing a stirring gas and a refining agent in the direction, wherein operating conditions of the oxygen lance and injection lance are as follows, and the refining agent is Switching from a desiliconization agent to a desulfurization agent containing CaO and Mg, so that the slag composition when shifting from desiliconization to desulfurization treatment is in the range of CaO / SiO ₂ = 0.5 to 1.0 and T.Fe ≦ 15 mass%. It is characterized by adjusting.

θ _inj = 0 (when n _inj = 1) or θ _inj = 30 to 120 (when n _inj ≧ 2)
H _inj / H _{m ≤0.46}
R _inj / R _lad ≦ 0.34
n _oxy = 2-4
d _oxy = 0.015-0.045
θ _oxy = 5 _~ 20
H _oxy = 1-2
0.20 ≦ L _oxy ≦ 16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) +0.25
Fr = (ρ _g / (ρ _m -ρ _g )) × (((Q _inj × W _m / 60 / n _inj ) / (π × (d _inj / 2) ^ 2)) ^ 2 / (d _inj × g))
here,
θ _inj : Angle between nozzle holes of the injection lance [°] when the injection lance inserted in the ladle is viewed from above the ladle
H _inj : Distance between the tip of the injection lance and the bottom of the _ladle [m]
H _m : Hot metal depth [m]
R _inj : Deviation in the radial direction from the center of the ladle in the horizontal section of the injection lance [m]
R _lad : Ladle radius [m]
n _oxy : Number of nozzle holes in the oxygen lance [-]
d _oxy : Oxygen lance nozzle hole diameter [m]
θ _oxy : Oxygen lance nozzle tilt angle [°]
H _oxy : Oxygen lance height (distance from nozzle discharge to hot water surface) [m]
L _oxy : Horizontal distance between oxygen lance and injection lance [m]
Fr: Modified fluid number [-]
d _inj : Injection lance nozzle _hole diameter [m]
θ _inj-oxy : Minimum angle [°] between the injection direction and oxygen lance direction on the oxygen lance side
n _inj: injection nozzle hole number of the lance [-]
Q _inj : Stirring gas flow rate [Nm ³ / min / t]
W _m : Amount of hot metal [t]
ρ _m : Hot metal density [kg / m ³ ]
ρ _g : Carrier gas density [kg / m ³ ]
g: Gravity acceleration [m / s ² ]
“^” Means power.

  According to the present invention, when performing desiliconization desulfurization of molten iron in a container using an injection lance and an oxygen lance, refining can be performed efficiently without removing slag when switching from desiliconization treatment to desulfurization treatment.

It is the figure which shows the schematic of a refining equipment (pretreatment equipment), and various dimensions. It is the figure which put together the bubble arrival distance in a water model. It is the top view which showed the pattern of the position of a nozzle discharge hole. It is the top view which showed the position of the nozzle discharge hole in an Example and a comparative example. It is the other top view which showed the position of the nozzle discharge hole in an Example and a comparative example. It is the figure which put together the relationship between angle (theta) _inj between nozzle discharge holes, and refining efficiency (desiliconization oxygen efficiency and desulfurization lime efficiency). It is the figure which put together the relationship between H _inj / H _m and refining efficiency. It is the figure which put together the relationship between R _inj / R _lad and refining efficiency. It is the figure which put together the relationship between directivity and refining efficiency in injection lance blowing. It is the figure which put together the relationship between _noxy and refining efficiency. It is the figure which put together the relationship between _doxy and refining efficiency. It is the figure which put together the relationship between (theta) _oxy and refining efficiency. It is the figure which put together the relationship between _Hoxy and refining efficiency. It is the figure which put together the relationship between _Loxy and refining efficiency. Is a diagram which shows a summary of the relationship between the CaO / SiO ₂ and refining efficiency. It is the figure which put together the relationship between T.Fe and refining efficiency. It is the figure which put together the desiliconization oxygen efficiency and desulfurization lime efficiency of an Example and a comparative example. It is the figure which put together the relationship between L _oxy -16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) and refining efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Generally, the hot metal discharged from the blast furnace is first subjected to preliminary treatment such as desiliconization treatment or desulfurization treatment and then decarburization treatment. Preliminary treatments such as hot metal desiliconization treatment and desulfurization treatment are also carried out in a kneading vehicle or the like, but in the present invention, preliminary treatment in a ladle (desiliconization treatment, desulfurization treatment) is targeted.

  In the hot metal discharged from the blast furnace, [Si] is usually 0.3 to 0.6% by mass, and may be about 1.0% by mass depending on the state of the blast furnace. It needs to be reduced. In the present invention, hot metal having a hot metal [Si] of 0.25 mass% or more is targeted. In general, [C] is 4.3 to 4.6% by mass, and [P] is about 0.09 to 0.13% by mass, and prior to decarburization or dephosphorization performed in a converter or the like from the viewpoint of refining efficiency, It is desirable to remove [Si] and [S] as low as possible.

Fig.1 (a) shows the refining equipment (pretreatment equipment) which performs the hot metal refining method concerning this invention. First, the refining equipment will be described.
The refining equipment 1 includes a ladle 3 charged with hot metal 2, an oxygen lance 4 for blowing oxygen gas to the hot metal 2 of the ladle 3, and a refining agent 5 such as a desiliconizing agent and a desulfurizing agent. And an injection lance 6. A nozzle discharge hole 7 for blowing a refining agent is provided at the tip of the injection lance 6. When performing the refining process, the oxygen lance 4 and the injection lance 6 are inserted into the ladle lid 8. Among them, the injection lance 6 is immersed in the hot metal 2, and the oxygen lance 4 is installed on the hot metal 2 in order to spray oxygen from above the hot metal 2. The oxygen lance 4 is installed at the center O of the ladle 3, and the injection lance 6 is installed eccentrically at a predetermined distance from the center O of the ladle 3 and is installed in the vicinity of the oxygen lance 4.

  In the refining process, it is desired to increase the reaction interface area and increase the reaction rate by accelerating the movement of reaction components to the interface. Therefore, in the refining process, the refining process is performed while stirring the hot metal 2 by blowing the stirring gas (carrier gas) and the refining agent into the hot metal by the injection lance 6. When the carrier gas is blown by the injection lance 6 (when the hot metal is vigorously stirred), the hot metal 2 scatters when the free board is small, so the refining equipment 1 prevents the molten metal 2 from splattering. A ladle lid 8 is provided.

In such a refining equipment 1, the hot metal 2 is removed by a transition reaction and a carrier gas while the desiliconizing agent blown into the hot metal 2 is blown into the hot metal 2 by the injection lance 6. By stirring, the reaction of the permanent reaction (between the slag and the molten iron) is advanced, and oxygen is blown onto the molten iron with the oxygen lance 4 to perform the desiliconization treatment. Next, the desulfurization reaction is advanced by switching the blowing of the refining agent from the desiliconizing agent to the desulfurizing agent by the injection lance 6 and blowing the desulfurizing agent into the hot metal. In other words, in the present invention, desiliconization treatment is performed without removing slag by properly installing the operating conditions (installation position, flow rate of oxygen gas to be blown, flow rate of refining agent, etc.) of the oxygen lance 4 and injection lance 6. Therefore, desulfurization treatment is performed at the same position to shorten treatment time and improve productivity.

First, the operating conditions of the injection lance will be described.
As shown in FIGS. 1A and 1B, the injection lance 6 is eccentric from the center O of the ladle 3, and in this eccentric state, the nozzle discharge hole 7 of the injection lance 6 faces the oxygen lance. It has been.
Here, the number and angle of the nozzle discharge holes 7 will be described.

The nozzle discharge holes 7 for blowing the refining agent 5 may be either single or plural. As shown in FIG. _1C , when the angle θ _inj between the nozzle discharge holes is considered in a plan view, when there are two or more nozzle discharge holes 7 (when n _inj ≧ 2), the distance between the nozzle discharge holes The angle θ _inj (hole interval) is set to 30 to 120 °. When the angle θ _inj <30 ° between the nozzle discharge holes, the angle of the nozzle discharge hole 7 is too small, so when the refining agent is blown out simultaneously with the carrier gas, the refining agent dispersibility is poor, and the refining agent and the molten iron The contact area is reduced. On the other hand, when the angle between the nozzle discharge holes θ _inj <120 °, the dispersibility of the refining agent is improved, but the _{stirrability with} respect to the hot metal is reduced and the hot metal cannot be circulated efficiently, and the _stirrability and reactivity As a result, the refining efficiency may be reduced. Further, since the nozzle discharge hole 7 is eccentric to the wall surface side of the ladle 3 from the center O of the oxygen lance 4 and is directed to the oxygen lance 4, the angle θ _inj <120 ° between the nozzle discharge holes is satisfied. The nozzle discharge hole 7 is located close to the wall surface of the ladle 3, and when the refining agent is blown in, the hot metal 2 may collide with the wall surface of the ladle 3 to reduce the life of the refractory. For this reason, when there are two or more nozzle discharge holes 7 (when n _inj ≧ 2), the angle θ _inj (hole interval) between the nozzle discharge holes needs to be set to 30 to 120 °. Note that when there is one nozzle discharge hole 7 (when n _inj = 1), the angle θ _inj between the nozzle discharge holes cannot be defined, so that θ _inj = 0 for convenience of explanation.

Now, when performing desiliconization treatment or desulfurization treatment, the injection lance 6 is immersed in the hot metal, but in order to efficiently perform the desiliconization treatment or desulfurization treatment, the amount of immersion of the injection lance 6 into the hot metal 2 (insertion) Depth is also important. Here, as shown in FIG. 1A, the distance from the tip of the injection lance 6 to the bottom of the ladle 3 is “H _inj ”, and the depth of the hot metal, that is, the hot metal bath surface to the ladle 3 It is assumed that the distance to the bottom is “H _m ” and the immersion amount is expressed as H _inj / H _m . When the value of H _inj / H _m (dipping amount) is large, the time for the blown refining agent to rise to the hot metal is short, and the efficiency of the transition reaction decreases. Further, when the value of H _inj / H _m is large, the stirring action and mixing action when the carrier gas is blown are weak, and in particular, the stirring force (stirring power density) by the carrier gas is reduced. For this reason, the efficiency of the permanent reaction may be reduced. Therefore, in order to perform desiliconization treatment and desulfurization treatment efficiently, the immersion amount of the injection lance should be small (the deeper the immersion position is better), specifically, H _inj / H _m ≦ 0.46. It is preferable.

As described above, the injection lance 6 has a role of stirring or mixing the hot metal 2. From this point of view, it is preferable that the hot metal 2 circulates greatly in the ladle 3. If the injection lance 6 is decentered from the center O of the ladle 3 in a state in which the ladle 3 is viewed in plan, it can be expected that the stirring efficiency by the injection lance 6 is increased. Here, when the deviation from the center O of the ladle 3 in the radial direction is “R _inj ” and the ladle radius is “R _lad ” in the horizontal sectional view of the injection lance 6, the eccentric amount R _{inj of the} injection lance 6 If / R _lad is 0.34 or less, the stirring efficiency is improved, so that the residence time of the refining agent is increased or the relative speed with the molten iron is reduced, thereby improving the refining efficiency.

In summary, the operating conditions of the injection lance 6 are summarized as _follows. The angle θ _inj between the nozzle discharge holes _needs to be 30 to 120 ° (when n _inj ≧ 2) or 0 (when n _inj = 1). The immersion amount H _inj / H _{m needs to be} 0.46 or more, and the eccentric amount R _inj / R _lad of the injection lance 6 needs to be 0.34 or less.
Now, in the desiliconization treatment, a permanent reaction by desiliconization slag and molten iron, and a reaction with oxygen blown from an oxygen lance, desiliconization slag and desiliconization agent are required. That is, as shown in FIG. 1 (a), the desiliconizing agent (refining agent 5) blown from the injection lance 6 floats up the molten iron 3 and reacts with desiliconized slag, or reacts with molten iron and oxygen. Ideal to do. Here, when considering the direction of the nozzle discharge hole of the injection lance 6, that is, the carrier gas (stirring gas) blown from the injection lance 6 and the blowing direction (directivity) of the refining agent, the carrier gas and the refining agent are oxygen lances. The refining agent is likely to reach the portion that has become bare hot water due to oxygen in the oxygen lance, and the refining efficiency is improved.

  The arrows in FIGS. 1B and 1C indicate the directivity of the injection lance 6 for blowing. As shown in FIGS. 1B and 1C, consider a combined vector obtained by combining the blowing vector from one nozzle ejection hole 7 and the blowing vector from the other nozzle ejection hole 7. When the directivity of blowing the injection lance 6 is viewed from the combined vector by the nozzle discharge hole 7, the refining efficiency is improved in a state where the combined vector is directed to the oxygen lance side.

Specifically, the experiment shows that the refining efficiency is high when the angle between the combined vector shown in FIG. 1C and the straight line connecting the center of the injection lance 6 and the center of the oxygen lance 4 is 0 to 30 °. I have confirmed. Thus, in the present invention, the refining efficiency is also improved by directing the directivity of the injection lance 6 to the oxygen lance side.
Next, the operating conditions of the oxygen lance will be described.

A nozzle for blowing oxygen is provided at the tip of the oxygen lance 4, and the number of nozzle holes n _oxy of the oxygen lance 4 is preferably 2-4. When the number of nozzle holes _noxy of the oxygen lance 4 is one, an oxygen jet (referred to as an oxygen gas jet) tends to gather at one point, and the sprayed oxygen does not react efficiently with slag or hot metal. On the other hand, when the number of nozzle holes n _oxy of the oxygen lance 4 is 5 or more, although the oxygen gas jet is dispersed, the collision pressure of the oxygen gas jet is small and the sprayed oxygen does not react efficiently with slag or hot metal. Therefore, in the present invention, the number of nozzle holes n _oxy in the oxygen lance 4 is set to 2-4.

In addition to the number of nozzle holes _noxy of the oxygen lance 4, the nozzle hole diameter _doxy is also important. If the nozzle hole diameter d _{the oxy} oxygen lance 4 is smaller than 0.015 m, liable oxygen gas jet gathered at one point, blown oxygen is not slag and hot metal reacts efficiently. Meanwhile, the nozzle hole diameter d _{the oxy} oxygen lance 4 is greater than 0.045 m, but the oxygen gas jet is dispersed, small impact pressure of the oxygen gas jets, blown oxygen is not slag and hot metal reacts efficiently. Therefore, in the present invention, the nozzle _hole diameter d _oxy of the oxygen lance is set to 0.015 to _0.045 m.

Also, the inclination angle θ _oxy of the nozzle of the oxygen lance 4 is important. When the nozzle inclination angle θ _oxy (horizontal opening angle or oxygen gas jet spread angle) of the oxygen lance 4 is less than 5 °, the oxygen gas jet tends to gather at one point, and the sprayed oxygen is more efficient than slag and hot metal. Does not respond. On the other hand, when the nozzle inclination angle θ _oxy of the oxygen lance 4 is larger than 20 °, the oxygen gas jet is dispersed, but the collision pressure of the oxygen gas jet is small, and the sprayed oxygen does not react efficiently with the slag or hot metal. Therefore, in the present invention, the nozzle inclination angle θ _oxy of the oxygen lance 4 is set to 5 to 20 °.

Further, the height H _oxy of the oxygen lance 4, that is, the distance from the nozzle to the _{molten metal} surface is also important. When the height H _oxy of the oxygen lance 4 is less than 1 m, the distance from the nozzle to the molten metal surface is too small, so that the oxygen gas jet tends to gather at one point and the collision pressure becomes too large (hard blow) and sprayed. Oxygen does not react efficiently with slag or hot metal. On the other hand, when the height H _oxy of the oxygen lance 4 is larger than 2 m, the oxygen gas jet is likely to spread over a wide area, but the bare water due to the oxygen lance pushing the slag is not formed, and the sprayed oxygen is not slag or hot metal. Does not respond efficiently. Therefore, in the present invention, the height H _oxy of the oxygen lance is set to 1 m or more and 2 m or less.

The operation conditions of the oxygen lance 4 are summarized as follows. The nozzle hole number n _oxy is 2 to 4, the nozzle hole diameter d _oxy of the oxygen lance is 0.015 to _0.045 m, the nozzle inclination angle θ _oxy of the oxygen lance is 5 to 20 °, oxygen Lance height H _oxy needs to be 1-2m.
The positional relationship between the oxygen lance 4 and the injection lance 6 is also important. When the distance (horizontal distance) between the oxygen lance 4 and the injection lance 6 is “L _oxy ”, metal may adhere to the tip of the injection lance 6 or the oxygen lance 4. In order to achieve this, the distance L _oxy between the oxygen lance 4 and the injection lance 6 needs to be set to 0.20 m or more. Further, a distance less than L _{the oxy} oxygen lance 4 and the injection lance 6 is 0.20m when the distance is too small, the portion of the Hadakayu by blowing oxygen lance oxygen hardly refining agent is floated, to promote the reaction Sometimes it doesn't connect. Therefore, in consideration of the floating position of the refining agent blown from the injection lance 6 and the collision position of oxygen from the oxygen lance 4, it is necessary to keep the distance _Loxy between the oxygen lance 4 and the injection lance 6 to some extent.

As described above, the distance L _oxy between the oxygen lance 4 and the injection lance 6 needs to be 0.2 m or more, but the oxygen collision position by the blowing of the oxygen lance 4, the bare hot water portion, and the refining agent floating position The distance L _oxy between the oxygen lance 4 and the injection lance 6 has a limit when considering the balance of the collision position of oxygen, the portion where the naked hot water is formed, and the floating position of the refining agent. .

Here, the bubble arrival distance L of the carrier gas blown from the injection lance 6 affects the floating position of the refining agent, the formation of naked hot water, and the like. Therefore, the inventors examined the maximum value of the distance L _oxy between the oxygen lance 4 and the injection lance 6 while focusing on the bubble arrival distance L of the carrier gas. As shown in "Ishibashi, Shiroishi, Yamamoto, Shimada, Iron and Steel, vol.61 (1975) 4, S110" (hereinafter sometimes referred to as Document A) about the behavior of bubbles blown into the bath. It is shown that the bubble reach distance L is proportional to Fr ^ 1/3 and d _inj , but the inventors, as will be described later, operate conditions (n _inj , d _inj ) of the injection lance 6. The bubble arrival distance L when stirring the hot metal in the ladle was determined from the water model and the actual machine experiment. As a result, it was found that the bubble arrival distance L is expressed by “16.1 × (Fr ^ (1 / 3.4)) × d _inj ”.

In addition, since the inventors also influence the directivity (angle) of blowing the injection lance 6 on the floating position of the refining agent and the formation of naked hot water, the minimum angle between the injection direction and the oxygen lance direction on the oxygen lance side. _{Taking into consideration} θ _inj-oxy (the smallest of the angles between the vector of the nozzle discharge hole 7 and the straight line connecting the center of the injection lance 6 and the oxygen lance 4), the minimum angle θ _inj-oxy From the distance, the maximum value of the distance L _oxy between the oxygen lance 4 and the injection lance 6 was verified. As a result, the maximum distance L _oxy between the oxygen lance 4 and the injection lance 6 must be 16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) +0.25 or less. I found something.

“Fr” is the modified fluid number [−], and Fr = (ρ _g / (ρ _m −ρ _g )) × (((Q _inj × W _m / 60 / n _inj ) / (π × (d _inj / 2) ^ 2)) ^ 2 / (d _inj × g)). “Q _inj ” is the stirring gas flow rate (carrier gas flow rate) [Nm ³ / min / t], “W _m ” is the hot metal amount [t], “ρ _m ” is the hot metal density [kg / m ³ ], “ “ρ _g ” is the carrier gas density [kg / m ³ ], and “g” is the gravitational acceleration [m / s ² ].
Table 1 and FIGS. 2 (a) to 2 (d) summarize the derivation process of the maximum value of the distance _Loxy between the oxygen lance 4 and the injection lance 6 by the water model and the actual machine. Derivation of the distance L _oxy between the oxygen lance 4 and the injection lance 6 by the water model will be described.

In the water model, a container having a radius R _lad = 0.238 _m is used, H _m = 0.385 _m , n _inj = 1,3, θ _inj = 120 °, injection lance _hole diameter d _inj = 0.0025 m, 0.004 m, 0.008 m, H _inj = 0.125 m, injection lance gas amount Q _ini.Ar = 0.020 to _0.180 Nm ³ / min, and the bubble arrival distance (bubble horizontal arrival distance) was determined by observing the hot water surface visually.
The actual machine uses a hot metal ladle with a radius R _lad = 1.34 _m , H _m = 2.4 m, n _inj = 1,2, θ _inj = 180 °, ejection lance _hole diameter d _inj = 0.020 m, H _inj = 0.7 m The gas amount Q _ini.N2 of the injection lance was _{set to} 1 to 4 Nm ³ / min, and the bubble arrival distance (bubble horizontal arrival distance) was obtained by taking a picture of the hot water surface through photography or video shooting. In the water model, the density of water ρ _m = 1000 kg / m ³ , the carrier gas of the injection lance 6 is Ar, and the density ρ _{m. The ar} was 1.600 kg / m ³ . In the actual machine, the hot metal density ρ _m = 6800 kg / m ³ , the carrier gas of the injection lance 6 is N ₂ , and the density ρ _{m. N2} was set to 1.251 kg / m ³ . In addition, the acceleration of gravity in water model and the actual machine was set to 9.8m / s ^2.

As shown in Table 1 and FIG. 2 (a), the bubble arrival distance (L, cal) obtained by the same formula as document A in the water model and the actual machine and the actually measured bubble arrival distance (L, obs) are Disagreement does not match. In particular, when the number of nozzle holes and the nozzle hole diameter of the injection lance 6 are changed, the deviation of the bubble arrival distance L is remarkable in the strong stirring region. Therefore, when considering actual refining, it is necessary to accurately obtain the bubble arrival distance L even with strong stirring, and the coefficient must be corrected with reference to Document A. The bubble arrival distance L from the injection lance 6 nozzle (horizontal nozzle) and the corrected fluid number are expressed as L / d _inj = a x Fr ^ b ("^" is a power display, a is a coefficient). As shown in FIG. 2 (c), L / d _inj = 7.8 × Fr ^ (1 / 3.4) based on the result of the water model and the like. As shown in FIG. 2 (b), using the above formula (L / d _inj = 7.8 × Fr ^ (1 / 3.4)), the calculated bubble arrival distance in the water model and the actual bubble arrival distance When the relationship was obtained, the bubble arrival distance could be obtained accurately. Based on the results in this water model, the bubble arrival distance (L = L, obs) in the hot metal is determined. As shown in Fig. 2 (d), L / d _inj = 16.1 x (Fr ^ (1 / 3.4)) The result was obtained. For the correspondence between the water model and the actual machine, refer to `` Analysis of gas-liquid flow phenomenon for optimal design of bottom blowing tuyere, Kato et al., Iron and Steel, Vol. 70 (1984) 3,380-387 '' I made it.

In the present invention, desiliconization treatment and desulfurization treatment are performed according to the operation conditions described above, but when the refining agent is switched from the desiliconization agent to the desulfurization agent, the slag composition is CaO / SiO ₂ = 0.5 to 1.0, T. The range is Fe ≦ 15% by mass. The desiliconization treatment is an oxidation reaction, and the desulfurization treatment is a reduction reaction. Here, when desulfurization treatment is performed without removing the desiliconized slag, the CaS produced by the transition reaction of the CaO-based desulfurizing agent comes into contact with the desiliconized slag, and the sulfur is not fixed. Therefore, composition control of desiliconized slag is important. On the other hand, securing the meltability is also important from the viewpoint of the exhaustability after the desiliconization / desulfurization treatment, and an optimum composition range exists. General desulfurization promoting conditions are high basicity (CaO / SiO ₂ ) and low oxygen potential (T.Fe). In the case of CaO / SiO ₂ <0.5 and T.Fe> 15% by mass, the desulfurization ability is low, forming a slag having a high viscosity, and it is difficult to fix sulfur S. When CaO / SiO ₂ > 1.0, the slag solidifies during the desulfurization treatment, and the oxygen potential increases due to atmospheric oxidation of the metal in the slag, making it difficult to fix sulfur S. Therefore, when switching from a desiliconization agent to a desulfurization agent, the slag composition is set to CaO / SiO ₂ = 0.5 to 1.0 and T.Fe ≦ 15 mass%.

  Tables 2 to 11 summarize examples in which refining was performed by the hot metal refining method of the present invention and comparative examples in which refining was performed by a method different from the hot metal refining method of the present invention.

First, implementation conditions in Examples and Comparative Examples will be described.
A 100-ton hot metal ladle was used, and the ladle radius R _lad was 1.34 m. In addition, H _m = 2.40m, and 0.8m of freeboard FB for the ladle was secured in consideration of the fluctuation of the molten metal surface during stirring. The hot metal weight W _m was 92.0t, and the hot metal from the blast furnace cast iron (slag) was received and refined. The hot metal temperature T _{m, i} was set to 1300 to 1400 ° C (varied depending on the operating conditions of the blast furnace), and the frequently used 1350 ° C was used as the base condition. [Si] _i of the molten iron was set to 0.40 to 0.90 mass%, and [Si] _i = 0.65 mass%, which is frequently used, was used as a base condition. Further, the [S] _i of the molten iron was set to 0.015 to 0.022% by mass, and [S] _i = 0.017% by mass having a high frequency was used as a base condition.

As a condition for the silicon removal treatment, the silicon removal treatment time τ (Si) was set to 5.0 to 16.5 min. The desiliconization treatment time is as per ordinary methods in the art as described in, for example, JP-A-08-218109. The desiliconization processing time is the time from the start of blowing of the desiliconizing agent from the injection lance 6 and / or the start of blowing oxygen from the oxygen lance 4 to the end of blowing of the desiliconizing agent and / or the blowing of oxygen lance 4. is there. The composition of the desiliconizing agent includes 70.8Fe ₂ O ₃ -21.4CaO-2.5SiO ₂ (in mass%), T.Fe = 49.5 (C 2 _O = 21.3) mass%, and CaO / SiO ₂ = 8.6. For example, as described in JP-A-2006-328453, the desiliconizing agent is a conventional one as used by those skilled in the art, and a mixture of pellet sieving powder and lime powder was used as an iron oxide source. Lime powder plays a role in adjusting the basicity (CaO / SiO ₂ ) of desiliconized slag. The desiliconizing agent charging rate [feeding rate F _inj (Si)] is as described in Japanese Patent Application Laid-Open No. 08-218109, and is 100 to 250 kg / min according to the ordinary method of those skilled in the art. The basic unit W _flux (Si) of the desiliconizing agent was 5.4 to 44.8 kg / t. De珪剤of intensity W _flux (Si) is the be obtained by _{W flux (Si) = F ing} (Si) × τ (Si) / W m, the carrier gas used was N _2. The oxygen gas flow rate Q _oxy was 0.43 to 0.54 Nm ³ / min / t, and the oxygen basic unit W _o (Si) was 5.0 to 12.6 kg / t. Oxygen consumption rate W _o (Si) is determined by _{W o (Si) = W flux} (Si) × C o / 100 + Q oxy × τ (Si) / (1000/32 × 22.4 × 10 -3)) It was.

As a desulfurization treatment condition, the desulfurization treatment time was set to τ (S) = 3.5 to 5.5 min. The desulfurization treatment time was the time from the start to the end of blowing the desulfurizing agent by the injection lance 6. The composition of the desulfurization agent was CaO-20Mg (in mass%) and C _CaO = 80 mass%. As the desulfurizing agent, for example, as described in JP-A-08-218109, lime powder was used as a CaO (S immobilization) source, and a mixture of metal Mg was used. The desulfurization agent charging rate [feed rate F _inj (S)] was 80 kg / min. Intensity of the desulfurization agent W _flux of (S) and 3.0~4.8kg / t, intensity of the desulfurization agent W _flux (S) _{is, W flux (S) = F} ing (S) × τ (S) / W m I asked for it. N ₂ was used as a carrier gas. In desulfurizing agent CaO intensity W _CaO (S) is set to 2.4~3.8kg / t, CaO intensity W _CaO (S) was determined by _{W CaO (S) = W flux} (S) × C CaO / 100 .

For the injection lance 6 and the oxygen lance 4, the operating conditions were varied. In addition, when switching from desiliconization to desulfurization, slag in the ladle was not discharged. Moreover, in a comparative example, in order to compare with an Example, CaO, a silica stone, and an iron ore were thrown in immediately before switching from a desiliconization process to a desulfurization process. The desiliconization treatment time τ (Si) and the desulfurization treatment time τ (S) were set to 9.5 to 21 minutes in accordance with the cycle time of the dephosphorization treatment in the next step. In addition, the hot metal temperature T _{m, f} after the treatment was determined in consideration of the thermal margin of the subsequent steps (dephosphorization, decarburization) and the ratio of solid oxygen and gaseous oxygen during the desiliconization treatment was aimed at 1350 ° C.

  Further, for example, in the example and the comparative example, the arrangement of the nozzle discharge holes of the injection lance 6 was changed as shown in FIG. As shown in FIG. 3, with reference to a line connecting 90 ° and −90 ° passing through the center of the injection lance 6, the side (left side) away from the oxygen lance 4 is the anti-oxygen lance side and the side closer to the oxygen lance 4 (right side) ) On the oxygen lance side, and the position of the nozzle discharge hole is shown in angle. 4 and 5 are diagrams showing the positions of the nozzle discharge holes in the examples and comparative examples, and the numbers in the drawings correspond to the numbers in the examples and comparative examples.

Since [Si] in the hot metal reacts with oxygen (oxygen sprayed by the injection lance 6 and oxygen lance 4) and is removed from the hot metal, oxygen efficiently contributed to the desiliconization reaction in the examples and comparative examples. Evaluation was made using the desiliconization oxygen efficiency (the ratio of the oxygen content used for the oxidation of [Si] in the hot metal relative to the given oxygen content) as an index to express the above.
When hot metal [S] reacts with a lime-based desulfurization agent, the reaction formula is expressed as CaO + Mg + S = CaS + MgO. Therefore, in the examples and comparative examples, lime is effectively used in the desulfurization reaction. Evaluation was made by using desulfurized lime efficiency (ratio of lime content used for reaction with [S] in hot metal to given lime content in the desulfurizing agent) as an index indicating whether it contributed.

As shown in Examples 1 to 25, even when the number of nozzle discharge holes is one (when n _inj = 1), the operating conditions of the injection lance 6 (H _inj / H _m ≦ 0.46, R _inj / R _lad ≦ 0.34) , Synthetic vector within 30 °), operating conditions of oxygen lance 4 (n _oxy = 2-4, d _oxy = 0.015-0.045, θ _oxy = 5-20, H _oxy = 1-2), injection lance 6 and oxygen The lance 4 operating conditions (0.20 ≦ L _oxy ≦ 16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) +0.25) are satisfied and switching from desiliconization to desulfurization If the slag composition conditions (CaO / SiO ₂ = 0.5 to 1.0, T.Fe ≦ 15 mass%) are satisfied, the [Si] after treatment will be 0.25 mass% or less and the treated [S] could be made 0.010% by mass or less, and desiliconization treatment and desulfurization treatment could be performed efficiently.

Further, as shown in Examples 26 to 112, even when the number of nozzle discharge holes is two or more (when n _inj = 1), the operating conditions of the injection lance 6 (θ _inj = 30 to 120 °, H _inj / H _m ≦ 0.46, R _inj / R _lad ≦ 0.34, synthesis vector within 30 °), oxygen lance 4 operating conditions (n _oxy = 2-4, d _oxy = 0.015-0.045, θ _oxy = 5-20, H _oxy = 1-2), operating conditions of injection lance 6 and oxygen lance 4 (0.20 ≦ L _oxy ≦ 16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) +0.25) If the slag composition conditions (CaO / SiO ₂ = 0.5 to 1.0, T.Fe ≦ 15 mass%) when switching between desiliconization and desulfurization are satisfied, the slag will not be discarded [Si] could be 0.25% by mass or less, and [S] after the treatment could be 0.010% by mass or less, and desiliconization treatment and desulfurization treatment could be performed efficiently.

Next, the results of the comparative example will be described with reference to FIGS.
FIG. 6 summarizes the angle θ _inj between the nozzle ejection holes in Examples 25-30 and Comparative Examples _126-129 . As shown in Comparative Examples ₁₂₆ to _129, when the angle θ _inj between the nozzle discharge holes is less than 30 ° or larger than 120 °, the desiliconization oxygen efficiency and the desulfurized lime efficiency are drastically decreased compared to the examples. The result was low. FIG. 7 summarizes H _inj / H _m for Examples 27 and 31 to 36 and Comparative Examples 130 and 131. As shown in Comparative Examples 130 and 131, when H _inj / H _m exceeded 0.46, the desiliconization oxygen efficiency and the desulfurized lime efficiency were drastically decreased, and the results were lower than in the Examples.

FIG. 8 summarizes R _inj / R _lad for Examples 27 and 37 to 40 and Comparative Examples 132 and 133. As shown in Comparative Examples 132 and 133, when R _inj / R _lad was less than 0.34, the desiliconization oxygen efficiency and the desulfurized lime efficiency were drastically decreased, and the results were lower than in the examples. FIG. 9 summarizes the directivity in blowing the injection lance 6 for Examples 27, 41 to 44 and Comparative Examples 134 to 136. As shown in Comparative Examples 134 to 136, when the synthesis vector exceeds 30 °, that is, when the carrier gas and the refining agent are not blown in the direction from the injection lance 6 to the oxygen lance, the desiliconization oxygen efficiency and the desulfurized lime efficiency are rapidly increased. Lower results were obtained compared to the examples.

Figure 10 summarizes the n _{the oxy} for Examples 27,45,46 and Comparative Examples 137-139. As shown in Comparative Examples 137 to 139, when n _oxy exceeds 1 or 4, the desiliconization oxygen efficiency and the desulfurized lime efficiency are drastically decreased, and the results are lower than in the Examples. Further, FIG 11 summarizes the d _{the oxy} for Examples 27,47～50 and Comparative Examples 140 and 141. As shown in Comparative Examples 140 and 141, when _doxy was less than 0.015 or more than 0.045, the desiliconization oxygen efficiency and desulfurization lime efficiency were drastically decreased, resulting in lower results than in Examples.

FIG. 12 summarizes θ _oxy for Examples 27 and 51 to 53 and Comparative Examples 142 and 143. As shown in Comparative Examples 142 and 143, when θ _oxy was less than 5 ° or exceeded 20 °, the desiliconization oxygen efficiency and the desulfurized lime efficiency were drastically decreased, resulting in lower results than in the Examples. Figure 13 summarizes the H _{the oxy} for Examples 27,54～61 and Comparative Examples 144-147. As shown in Comparative Examples 144 to 147, when H _oxy was less than 1 m or more than 2 m, the desiliconization oxygen efficiency and the desulfurized lime efficiency were drastically decreased, resulting in lower results than in the Examples.

14 are those for Example 27,62～66 and Comparative Examples 148-151 summarizes L _{the oxy.} As shown in Comparative Examples 148 to 151, L _oxy is less than 0.2 m, or larger than 16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) +0.25 In this case, the desiliconization oxygen efficiency and the desulfurized lime efficiency were drastically decreased, and the results were lower than in the examples. FIG. 15 summarizes CaO / SiO ₂ for Examples 27 and 76 to 78 and Comparative Examples 161 to 164. As shown in Comparative Examples 161 to 164, when CaO / SiO ₂ was less than 0.5 or more than 1.0, desiliconization oxygen efficiency and desulfurization lime efficiency were drastically decreased, and the results were lower than in the examples.

FIG. 16 summarizes T.Fe for Examples 27 and 79 to 81 and Comparative Examples 165 to 167. As shown in Comparative Examples 165 to 167, when T.Fe was greater than 15% by mass, the desiliconization oxygen efficiency and the desulfurized lime efficiency were drastically decreased, resulting in lower results than in Examples. In addition, as shown in FIG. 17, in the examples and comparative examples, even if the desiliconization oxygen efficiency and the desulfurization lime efficiency are compared, in the examples, the efficiency of the desiliconization treatment and the desulfurization treatment is very good. It was. As shown in FIG. 18, when L _oxy −16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) is seen, the desiliconization oxygen efficiency is a comparative example in the example. It was higher than

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

1 Refining equipment 2 Hot metal 3 Ladle 4 Oxygen lance 5 Refining agent 6 Injection lance 7 Nozzle discharge hole 8 Ladle lid O Center of ladle

Claims (1)

A hot metal containing [Si] of 0.25% by mass or more is charged into a ladle, oxygen is blown from the oxygen lance to the hot metal in the ladle, and a stirring gas and a refining agent are blown from the injection lance toward the oxygen lance. A hot metal refining method for desiliconization and desulfurization of hot metal,
The operating conditions of the oxygen lance and injection lance are as follows:
And the slag composition at the time of shifting from the desiliconization agent to the desulfurization agent containing CaO and Mg from the desiliconization agent to the desulfurization treatment is CaO / SiO ₂ = 0.5 to 1.0, T.Fe ≦ 15 mass% A method for refining hot metal, which is adjusted so as to be in the range.
θ _inj = 0 (when n _inj = 1) or θ _inj = 30 to 120 (when n _inj ≧ 2)
H _inj / H _{m ≤0.46}
R _inj / R _lad ≦ 0.34
n _oxy = 2-4
d _oxy = 0.015-0.045
θ _oxy = 5 _~ 20
H _oxy = 1-2
0.20 ≦ L _oxy ≦ 16.1 × (Fr ^ (1 / 3.4)) × d _inj × cos (θ _inj-oxy ) +0.25
Fr = (ρ _g / (ρ _m -ρ _g )) × (((Q _inj × W _m / 60 / n _inj ) / (π × (d _inj / 2) ^ 2)) ^ 2 / (d _inj × g))
here,
θ _inj : Angle between nozzle holes of the injection lance [°] when the injection lance inserted in the ladle is viewed from above the ladle
H _inj : Distance between the tip of the injection lance and the bottom of the _ladle [m]
H _m : Hot metal depth [m]
R _inj : Deviation in the radial direction from the center of the ladle in the horizontal section of the injection lance [m]
R _lad : Ladle radius [m]
n _oxy : Number of nozzle holes in the oxygen lance [-]
d _oxy : Oxygen lance nozzle hole diameter [m]
θ _oxy : Oxygen lance nozzle tilt angle [°]
H _oxy : Oxygen lance height (distance from nozzle discharge to hot water surface) [m]
L _oxy : Horizontal distance between oxygen lance and injection lance [m]
Fr: Modified fluid number [-]
d _inj : Injection lance nozzle _hole diameter [m]
θ _inj-oxy : Minimum angle [°] between the injection direction and oxygen lance direction on the oxygen lance side
n _inj: injection nozzle hole number of the lance [-]
Q _inj : Stirring gas flow rate [Nm ³ / min / t]
W _m : Amount of hot metal [t]
ρ _m : Hot metal density [kg / m ³ ]
ρ _g : Carrier gas density [kg / m ³ ]
g: Gravity acceleration [m / s ² ]
“^” Means power.