JPH08225818A - Top-blown oxygen lance for dephosphorizing molten iron - Google Patents

Abstract

PURPOSE: To improve dephosphorizing efficiency by providing a lance having a structure to satisfy a prescribed condition to keep FetO in the slag to a high level and suppress decarburizing amount and fusing damage to refractories in achieving the dephosphorization by the slag of low CaF2 , low Ca/SiO2 and high FetO. CONSTITUTION: The structure of a lance is satisfied by the formulae I, IV and V and the inequalities II and III, where X is the horizontal displacement (mm) of the center axis of the oxygen jet, Y is the vertical displacement (mm) thereof, S is the distance (mm) of movement in the advancing direction, (d) is the diameter (mm) of the oxygen jet at S, do is the diameter (mm) of the nozzle, α is the nozzle angle ( deg.) when the locus of the center axis of the oxygen jet is brought into contact with the surface of molten iron, β is the angle ( deg.) where the oxygen jet reaches one half of the distance between the lance and the surface of molten iron, or the angle where the oxygen jet directly hits furnace wall, whichever is the smaller, γ is the nozzle diameter (mm) where the locus of the center axis of the oxygen jet is brought into contact with the surface of molten iron, and δ is the nozzle diameter (mm) where the oxygen jet reaches one half of the distance between the lance and the surface of the molten iron.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses the equation (1) for estimating the trajectory of the central axis of an oxygen jet from a top blowing lance, and uses the solvent for dephosphorization and the cost of dephosphorization slag utilization and dephosphorization. The present invention relates to a top-blown oxygen lance for efficiently dephosphorizing hot metal by reducing the amount of decarburization and the amount of refractory melting during treatment.

[0002]

2. Description of the Related Art Since hot metal produced in a blast furnace contains a large amount of phosphorus as an impurity, it is strongly required to efficiently remove phosphorus in the production process to improve the mechanical properties of steel products. ing.

Usually, this dephosphorization treatment is carried out together with the decarburization treatment by using a quicklime-based slag-forming agent during oxidative refining in a converter or the like, and recently, it is a preliminary treatment of hot metal prior to decarburization refining in a converter. A technique for removing phosphorus as well as sulfur has been put into practical use. Specifically, a method of adding quick lime, CaF ₂ , Na ₂ CO ₃ or the like to hot metal in a torpedo car, a ladle or a converter and stirring (injection or the like) has been used. Especially, when smelting low phosphorus steel, the slag basicity should be 2 or more,
It was common to use a flux with CaF ₂ added to promote slag formation. However, quick lime, CaF ₂ , Na ₂ CO _3, etc. are relatively expensive, and further reduction of the amount of solvent used is desired from the viewpoint of cost.

Therefore, the following method has been proposed as a method for ensuring the slag formation without using CaF ₂ and efficiently performing the dephosphorization treatment of the hot metal.

CaO-SiO ₂ -Fe _t O-based flux [CaO / SiO ₂
> 0.5, iron ore or top-blown oxygen is used during treatment (% Fe _t O)] (Japanese Patent Publication No. 55-30042), CaO-Al ₂ O
₃ -Fe _t O system flux (CaO: Al ₂ O ₃ = 2.5 to 20: 1, (% Fe _t
O) = 25 to 65, (% Fe _t O) is adjusted with iron ore] (JP-A-62-207810), and CaO-SiO ₂ -Fe _t O
System flux [CaO / SiO ₂ > 2.0, (T.Fe)> 50% by weight, (%
Fe _t O) is adjusted with iron ore] (JP-A-2-11712
Issue gazette).

[0006]

[Problems to be Solved by the Invention] Normally, when melting low-phosphorus steel, the basicity (CaO / SiO ₂ ) of the slag is set to 2 or more and the flux is added with CaF ₂ to promote slag formation. It was common to apply phosphorus treatment. However, in order to further reduce the amount of solvent used, it is necessary to minimize the amount of CaF ₂ used and to dephosphorize with low basicity (CaO / SiO ₂ ).

If the slag basicity is set to 2 or less, 3CaO.SiO ₂ → 2CaO ・ SiO ₂ + f-
Since free lime generated by the CaO (f-CaO: free lime) reaction is almost absent in the slag, it is possible that the treated slag can be used as a roadbed material even if the aging treatment is omitted.

In the methods disclosed in the above-mentioned JP-A-62-207810 and JP-A-2-11712, since (% Fe _t O) in the slag decreases during the dephosphorization treatment, dephosphorization In order to efficiently carry out the process, a large amount of iron oxide (iron ore, etc.) is added in the early stage so that a high value (% T.Fe) above a certain value is maintained until the end of the treatment. However, in this method, since a large amount of iron oxide is added, the hot metal temperature is drastically lowered after the addition, the slag formation of the flux is delayed, and as a result, the dephosphorization efficiency may be reduced.

According to the method disclosed in Japanese Examined Patent Publication No. 55-30042, high (% Fe _t O) is maintained during dephosphorization treatment by iron oxide and top-blown oxygen, but high (% Fe _t O) is maintained by top-blown oxygen. No specific method is mentioned. Further, if only the required amount of oxygen is blown up without considering the trajectory of the blown oxygen jet, the following problems (a) and (b) occur.

(B) If oxygen is vigorously blown onto molten iron (hard blowing is performed), decarburization proceeds more than necessary. As a result, the reaction between oxygen and the granular iron present in the slag (the granular iron suspended by the bottom-blown gas) is reduced,
High (% Fe _t O) cannot be maintained. Furthermore, the temperature of the hot metal may rise above the optimum temperature for the dephosphorization treatment due to the heat of the decarburization reaction, and the dephosphorization efficiency may decrease.

(B) Increasing the nozzle diameter and the nozzle angle to reduce the collision of oxygen with the hot metal (soft blow)
For example, if decarburization is suppressed more than necessary, the depth of penetration of the top-blown oxygen jet into the slag will decrease, making it difficult for (FeO) to form due to the reaction between top-blown oxygen and the granular iron in the slag. Therefore, the slag content (% Fe _t O) may not increase. Further, the top-blown oxygen jet collides with the furnace wall, which may increase the amount of refractory melting.

It is an object of the present invention that the flux cost is low, and the slag after the hot metal dephosphorization treatment can be used at low cost for roadbed materials, low (% CaF ₂ ), low CaO / SiO ₂ , high (% Fe _t O) is a top-blowing oxygen lance used in the dephosphorization method using slag, which maintains the slag in dephosphorization treatment (% Fe _t O) at a high value by top-blowing oxygen, and decarburizes by the top-blowing oxygen and fire resistance. An object of the present invention is to provide a top blowing oxygen lance capable of efficiently performing dephosphorization treatment by controlling the amount of physical melt loss.

[0013]

SUMMARY OF THE INVENTION The subject matter of the present invention is the following top-blown oxygen lance for hot metal dephosphorization.

In the top-bottom blow converter, a flux containing CaO and Fe _t O as main components was added, and the top blown oxygen increased the flux.
A hot-blown oxygen lance used for dephosphorization of hot metal while maintaining (% T.Fe), characterized by having a structure satisfying the conditions of the following formulas (1) to (3). Top blowing oxygen lance for phosphorus.

[0015]

[Equation 2]

Α ≦ θ ₀ ≦ β (2) γ ≦ d ₀ ≦ δ ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (3) However, d ＝ 2S ・ tan (θc / 2) ・ ・ ・ ・ ・ ・ (a) S ＝ ∫ { (dX) ² + (dY) ² } ^1/2・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (b) X: Horizontal displacement of oxygen jet central axis (mm) Y: Vertical direction of oxygen jet central axis Displacement (mm) S: Moving distance of the oxygen jet central axis in the traveling direction (mm) θc: Oxygen jet spread angle (20 °) θ ₀ : Nozzle angle (angle from vertical axis) (°) H: S Hold up of oxygen gas in oxygen jet (
−) D: Oxygen jet diameter at S (mm) d ₀ : Nozzle diameter (mm) U ₀ : Oxygen gas flow velocity at the nozzle outlet (mm / s) ρ _s : Density of molten slag (g / cm ³ ) ρ _g : Oxygen gas density at the nozzle outlet (g / cm ³ ) ρ _g ': Oxygen gas density in the oxygen jet assuming that the oxygen gas pressure is 1 atm (that is, the oxygen gas density is constant in the oxygen jet) (g / cm ³ ) g: Gravitational acceleration (m / s ² ) α: Nozzle angle when the orbit of the oxygen jet central axis contacts the hot metal surface (°) β: When the oxygen jet reaches half the distance between the lance and the hot metal surface Angle and the angle when the oxygen jet directly hits the furnace wall (°) γ: Nozzle diameter (mm) when the orbit of the oxygen jet central axis is in contact with the hot metal surface δ: Oxygen jet lance -Nozzle diameter when reaching half the distance between the hot metal surfaces (mm) Initial condition: X = d ₀ · cos θ ₀ / {2tan (θc / 2)}, Y = −d ₀ · sin θ ₀ / {2tan (θc / 2)} ・ ・ (c) dY / dX ＝ −tan θ ₀・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (d) The oxygen jet mentioned above is one nozzle outlet. It means a single oxygen jet ejected from.

The spread angle θc of the oxygen jet is
It is constant at 20 ° (NJThemelis: Trans.Met.Soc., AI
See ME, 245, 1969, page 2425).

The above-mentioned holdup H of oxygen gas in the oxygen jet means the volume ratio of the oxygen gas in the oxygen jet when the oxygen jet is in a mixed phase flow of oxygen gas and slag.

[0019]

The present invention has a problem in the conventional hot metal dephosphorization method, that is, the use of a large amount of an expensive solvent such as CaF ₂ or quick lime, and the aging treatment cost for making the treated slag into a roadbed material. Aim to solve the increase, reduce the amount of quicklime used without using CaF ₂ (Low basicity (CaO / SiO ₂ ))
However, the nozzle structure of the top blowing oxygen lance is capable of efficiently dephosphorizing the hot metal while maintaining high (% Fe _t O) and suppressing the decarburization amount and refractory melting loss during the treatment. It is a clarification.

Hereinafter, the operation of the lance of the present invention will be described in detail together with its effects with reference to FIGS.

FIG. 1 is a diagram schematically showing the trajectory of a single top-blown oxygen jet in the top-bottom blow converter, and the nozzle of this top-blown oxygen lance has a straight multi-hole structure. FIG. 2 is a diagram schematically illustrating the behavior of a single oxygen jet at the nozzle outlet. In FIG. 2, the coordinates of the point A are (0, 0), the point B is the nozzle outlet, and the coordinates are as follows.

(D ₀ · cos θ ₀ / {2tan (θc / 2)}, −d ₀ · sin θ ₀ / {2tan (θc / 2)}) In FIGS. 1 and 2, the X direction is the horizontal direction, The Y direction is vertical, and the dashed-dotted line is the trajectory of the oxygen jet central axis. The symbols shown are defined as above.

As shown in FIG. 2, the oxygen jet ejected from the nozzle spreads at an angle θc (= 20 ° C.), the jet advances in the horizontal direction while preserving the momentum, and the change in the momentum in the vertical direction causes buoyancy. It progresses until it is in equilibrium and thereafter rises due to buoyancy, as shown in FIG.

At this time, as shown in FIGS. 7 and 12, which will be described later, the trajectory of the oxygen jet central axis can be changed by changing the nozzle diameter d ₀ . That is, as the nozzle angle θ ₀ becomes smaller, the vertical momentum of the oxygen jet increases, so that the vertical reach increases, and conversely, at that time, the horizontal momentum decreases, so the horizontal reach decreases. To do.

When the oxygen gas flow velocity U ₀ at the nozzle outlet is equal to or lower than the sonic velocity, this flow velocity is increased as the nozzle diameter d ₀ is increased.
Since U ₀ decreases, the momentum of the oxygen jet decreases, and the reaching distance decreases in both horizontal and vertical directions.

The behavior of the top-blown oxygen jet in the slag during hot metal dephosphorization and the conditions during treatment (dephosphorization, decarburization, refractory erosion behavior) were investigated, and the trajectory of the oxygen jet central axis was estimated. By optimizing the nozzle diameter d ₀ and the nozzle angle θ _{0 according} to the formulas (1), (2), and (3), it is possible to achieve 0.01% or less of [P] after processing required for low phosphorus steel melting. Then
In addition, it was found that the decarburization amount and the refractory melting loss amount can be reduced.

In equation (1), the momentum in the horizontal direction of the oxygen jet is conserved, the change in the momentum in the vertical direction is equal to the buoyancy acting on the gas in the jet, and the oxygen jet has the momentum that combines the momentum in both directions. As one that goes in the direction,
This is an equation that allows the trajectory of the oxygen jet central axis to be estimated and calculated. The initial condition is a condition that determines the advancing direction of the oxygen jet central axis at the nozzle outlet indicated by point B in FIG.

That is, from the trajectory of the oxygen jet central axis calculated using the formula (1) and the formulas (a) to (d), the following 1),
By optimizing the nozzle diameter d ₀ and the nozzle angle θ ₀ under the conditions of formula (2) and formula (3) so that the condition of 2) is satisfied,
It was found that the slag (% T.Fe) in the slag during treatment can be maintained high, and as a result, dephosphorization can be performed efficiently.

1) The oxygen jet reaches more than half of the distance between the lance and the hot metal surface and does not directly hit the hot metal.

2) The oxygen jet should not hit the furnace wall directly.

Firstly, the results of experiments conducted by changing the shape of the nozzle angle theta ₀ and BOF furnace body for optimizing the nozzle angle theta _0, it is described by Figures 3-6.

The details will be described later in Examples, but a 2 ton test converter (furnace body A: furnace inner diameter 1090 mm, in some experiments furnace body B: furnace inner diameter)
1290 mm) and a flux containing CaO and Fe _t O as main components, and further hot metal dephosphorization was performed by blowing oxygen from the top blowing lance (outer diameter 90 mm) to remove the phosphorus and dephosphorize the oxygen lance at the nozzle angle θ _0. The effect on charcoal and refractory erosion was investigated. The nozzle diameter d _{0 at} this time is 3.7 m
m straight, 4 nozzles, oxygen flow 1.0Nm ³
/ min, the lance height was 350 mm.

FIG. 3 is a diagram showing the relationship between the slag (% T.Fe) and the nozzle angle θ ₀ during the dephosphorization treatment of 2 tons of hot metal. As shown in the figure, when the nozzle angle θ ₀ is 25 to 53 °,
The slag (% T.Fe) during processing could be maintained at a high value.

FIG. 4 shows the nozzle angle θ ₀ after processing [% P].
It is a figure which shows the relationship with. As shown in the figure, the target [P] ≦ 0.01 was achieved when the nozzle angle θ ₀ that maintained a high (% T.Fe) was 25 to 53 °.

FIG. 5 shows the refractory melting loss index and the nozzle angle θ _0.
It is a figure which shows the relationship with. Here, the refractory melting loss index is 1 when the single hole lance with a nozzle diameter of 8 mm (nozzle angle θ ₀ = 0 °) is used (oxygen jet does not collide with the furnace wall). It is an index. As shown in the figure, in the case of the furnace body A, the refractory melting loss index sharply increases when the nozzle angle θ ₀ is 30 ° or more. On the other hand, in the case of the furnace body B, the dephosphorization behavior matches that when the furnace body A is used as shown in FIG. 3, but the refractory melting loss index is almost 1 regardless of the nozzle angle θ _{0 as} shown in FIG. Met.

FIG. 6 shows the nozzle angle θ ₀ after processing [% C].
It is a figure which shows the relationship with. Nozzle angle θ as shown
_It can be seen that the smaller the _{value of 0, the} lower the [% C] after the treatment.

In FIG. 7, the nozzle angle θ ₀ is appropriately changed from 10 ° to 65 ° in the case of the furnace body A and the furnace body B, and
(1) shows the result of calculating the trajectory of the central axis of the oxygen jet alone. In FIG. 7, the upper left point 0 is the point A shown in FIG. As a result of measuring the slag foaming height during blowing and calculating the density ρ _{s of the} molten slag, 0.15 g / cm ³ was obtained, so this value was used in the above calculation.

From the results shown in FIGS. 7 and 3, when the trajectory of the oxygen jet central axis is not in contact with the hot metal surface (nozzle angle θ
₀ is 25 ° or more), the slag can be maintained at a high value (% T.Fe),
As a result, it is considered that after treatment [% P] was also lowered.
When the nozzle angle θ ₀ is smaller than 25 °, the oxygen jet directly hits the hot metal, so oxygen is consumed in the decarburization reaction and Fe
_tO could not be generated sufficiently and slag (% TF
e) becomes low. As a result, it is considered that the [% P] also increased after the treatment. When the nozzle angle θ ₀ exceeds 53 °, the oxygen jet cannot reach half of the distance between the lance and the hot metal surface, and the reaction between the oxygen jet and the granular iron in the slag decreases ((% T.Fe) in the slag). Was lower, and after treatment [% P] was also higher.

The nozzle angle θ ₀ is 30 ° or more and the furnace body A
In the case of No. 3, since the oxygen jet directly hits the furnace wall, it is proved that the refractory melt loss index rapidly increased as shown in FIG. However, in the case of furnace body B, the nozzle angle θ
_{Since the} oxygen jet does not directly hit the furnace wall regardless of ₀ , it is considered that the refractory melting loss index did not depend on the nozzle angle θ _{0 as shown} in FIG.

As described above, in order to perform the dephosphorization process efficiently, the optimum range for the nozzle angle θ ₀ , that is, the formula (2)
It can be seen that there is a range (α ≦ θ ₀ ≦ β) indicated by.
Here, α is obtained from the nozzle angle when the oxygen jet central orbit is in contact with the hot metal surface, and β is the angle when the oxygen jet reaches half the distance between the lance and the hot metal surface and when the oxygen jet hits the furnace wall directly. The angle is obtained from the smaller one, and the case of using the furnace body A corresponds to the latter, and the case of using the furnace body B corresponds to the former.

Next, regarding the optimization of the nozzle diameter d ₀ , the furnace body A
In the case of, the experimental results obtained by changing the nozzle diameter d ₀ will be described with reference to FIGS. The nozzle angle θ _{0 at} this time is
The conditions of 15 ° and other conditions were as in the above-mentioned test.

FIG. 8 is a diagram showing the relationship between the slag (% T.Fe) and the nozzle diameter d _0, and FIG. 9 is a diagram showing the relationship between the treated [% P] and the nozzle diameter d ₀ . As shown in FIGS. 8 and 9, when the nozzle diameter d ₀ was smaller than 4.6 mm, the slag (% T.Fe) could not be maintained at a high value, and [P] ≦ 0.01% could not be secured after the treatment. However, when the nozzle diameter d ₀ was 4.6 mm or more and 8.8 mm or less, high (% T.Fe) could be maintained and [P] ≦ 0.01% could be secured after the treatment. High when the nozzle diameter d ₀ exceeds 8.8 mm (% T.
Fe) could not be maintained, and [% P] increased after the treatment.

FIG. 10 is a graph showing the relationship between the refractory melting loss index and the nozzle diameter d ₀ . As shown in the figure, the refractory melting loss index was almost 1 regardless of the nozzle diameter d ₀ .

FIG. 11 is a view showing the relationship between the [% C] after treatment and the nozzle diameter d ₀ . As shown in the figure, as the nozzle diameter d ₀ increased, the post treatment [% C] increased.

FIG. 12 shows the result of calculating the trajectory of the oxygen jet central axis by the equation (1) with the nozzle diameter d ₀ appropriately changed, the nozzle angle θ ₀ being 15 °, and the slag density ρ _s being 0.15 g / cm ^3. Indicates. As shown in the figure, when the nozzle diameter d ₀ is smaller than 4.6 mm, the oxygen jet directly hits the surface of the hot metal, so oxygen is consumed in the decarburization reaction and Fe _t O cannot be generated sufficiently. T.Fe) becomes low. As a result, as shown in FIG. 9, the value after the treatment [% P] was also high. Nozzle diameter d ₀
When the value exceeds 8.8 mm, the oxygen jet cannot reach half the distance between the lance and the hot metal surface, the reaction between the oxygen jet and the iron in the slag is reduced, and the slag concentration (% T.Fe) becomes low. It is considered that [% P] also increased.

In this case, since the oxygen jet does not directly hit the furnace wall regardless of the nozzle diameter d ₀ , as shown in FIG.
The refractory melting loss index became almost 1 regardless of the nozzle diameter d ₀ .

As described above, in order to efficiently perform the dephosphorization treatment, it is found that there is an optimum range for the nozzle diameter d ₀ , that is, the range (γ ≦ d ₀ ≦ δ) shown by the equation (3). . γ is obtained from the nozzle diameter when the central orbit of the oxygen jet contacts the molten iron surface, and δ is obtained from the nozzle diameter when the oxygen jet reaches half the distance between the lance and the hot metal surface.

As described above, the trajectory of the central axis of the oxygen jet is calculated by the equation (1), and the oxygen jet reaches more than half of the distance between the lance and the hot metal surface and does not directly contact the hot metal, and the furnace wall To avoid hitting directly
By satisfying (3) and optimizing the nozzle angle θ ₀ and nozzle diameter d ₀ , (% T.Fe) during processing can be maintained high, and as a result, dephosphorization can be performed efficiently and It is possible to suppress the amount of decarburization and the amount of refractory meltdown inside.

Α ≦ θ ₀ ≦ β (2) γ ≦ d ₀ ≦ δ ...・ ・ ・ ・ ・ ・ ・ ・ (3) The above effect is not particularly dependent on the number of nozzle holes in the case of an outward straight nozzle with two or more holes,
Since the contact area between the oxygen jet and the slag increases as the number of holes increases, the high (% T.Fe) during processing can be efficiently maintained.
However, on the contrary, if the number of holes is too large, the oxygen flow rate per hole decreases, the oxygen jet does not reach half of the distance between the lance and the hot metal surface, and high (% T.Fe) cannot be maintained. Further, since the proper number of holes depends on the oxygen flow rate and the reaching distance of the oxygen jet at that time, the range of the desirable number of holes is 3 to
About 10 and more preferably about 3 to 6 or 8.

As the flux, one containing CaO and Fe _t O as main components is used as the initial packaging. CaO in composition by weight percent of the desired flux: 20~40%, Fe _t O: is about 50-80%, good components also contain other is MnO, Al ₂ O ₃ and SiO ₂
And so on. Preferred sources of Fe _t O include iron ore, scale and converter slag. The shape of the flux is not limited, but it is desirable to use a lump having a size of about 1 to 50 mm because it is added in the furnace.

A desirable oxygen flow rate range is about 0.3 to 0.7 Nm ³ / min per ton of molten iron.

[0052]

[Example] Top-bottom blowing test converter (furnace body A, furnace inner diameter: 1090 mm)
2 tons of hot metal (composition, C: 4.5%, Si: 0.3
%, P: 0.1%, balance: Fe and impurities))
11kg / t, 15kg / t of iron ore were added, and the nozzle diameter and nozzle angle were variously changed under the conditions shown in Table 1, and oxygen was 1.0Nm ³ / min (2.0Nm ^{3 for the} initial 3 minutes from a 4 hole straight top blowing lance). / min)
It was sprayed and dephosphorized for about 20 minutes.

The target [% P] after the treatment is 0.01% or less necessary for smelting low phosphorus steel, which is in great demand in recent years, and the target of the refractory melting loss index is 1 or less. It was investigated whether the slag after treatment could be used as a roadbed material without aging treatment. However, the test No. shown in Table 1
In Nos. 6, 9 and 11, a converter (furnace body B) having an inner diameter of 1290 mm was used.

Table 1 also shows (% T.Fe) during dephosphorization treatment, after treatment [% P], after treatment [% C], refractory damage index and posttreatment temperature.

[0055]

[Table 1]

When the nozzle diameter d ₀ = 3 mm, as shown in FIG. 7, in the furnace body A, the nozzle angle θ ₀ = 25 ° (test No. 4),
In furnace body B, nozzle angle θ ₀ = 30 °, 53 ° (Test No. 6, 9
) Only the condition of
Since the conditions 1) and 2) were satisfied, efficient dephosphorization became possible.

1) The oxygen jet reaches more than half of the distance between the lance and the hot metal surface, and does not directly hit the hot metal.

2) The oxygen jet should not hit the furnace wall directly.

When the nozzle angle θ ₀ = 15 °, as shown in FIG. 12, the nozzle diameter d ₀ = 4.6 mm, 7.0 mm, 8.8 mm (test
No.13, 14, 15 and furnace body A) only above
Since the conditions 1) and 2) were satisfied, efficient dephosphorization became possible.

Evaluations shown in Table 1 are indicated by ○ marks (after treatment [% P] <0.
In the post-treatment slag with 01 and the refractory dissolution index of 1.0), the free lime content was as small as 0.5% or less, and there was no risk of hydration swelling even without aging treatment. on the other hand,
In the case of (% T.Fe)> 10 in the slag after the treatment with the evaluation X mark, it was similar to the case of the above evaluation ○ mark, but (% T.Fe) ≤10
In this case, the slag formation was poor and the slag content was high. Therefore, aging treatment was required to suppress hydration expansion.

[0061]

EFFECTS OF THE INVENTION According to the top blowing oxygen lance for hot metal dephosphorization of the present invention, high (% T.Fe) in slag can be obtained without using expensive fluorspar (CaF ₂ ), quicklime and a large amount of iron ore. ) Can be maintained and dephosphorization can be performed efficiently. Moreover, it is possible to suppress the amount of decarburization and the amount of refractory melting at the time of processing, and it is possible to reduce the cost of melting low phosphorus steel.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a trajectory of a single top-blown oxygen jet in a top-bottom blow converter.

FIG. 2 is a diagram schematically illustrating the behavior of a single oxygen jet at the nozzle outlet.

FIG. 3 is a diagram showing a relationship between a slag (% T.Fe) during dephosphorization treatment and a nozzle angle θ ₀ .

FIG. 4 is a diagram showing a relationship between a processed [% P] and a nozzle angle θ ₀ .

FIG. 5 is a diagram showing a relationship between a refractory melting loss index and a nozzle angle θ ₀ .

FIG. 6 is a diagram showing a relationship between a processed [% C] and a nozzle angle θ ₀ .

FIG. 7 is a diagram showing the results of calculating the trajectory of the central axis of the oxygen jet simple substance by equation (1) while changing the nozzle angle θ ₀ .

FIG. 8 is a diagram showing a relationship between slag (% T.Fe) and nozzle diameter d ₀ .

FIG. 9 is a diagram showing a relationship between [% P] after processing and a nozzle diameter d ₀ .

FIG. 10 is a diagram showing a relationship between a refractory melting loss index and a nozzle diameter d ₀ .

FIG. 11 is a diagram showing a relationship between [% C] after processing and a nozzle diameter d ₀ .

FIG. 12 is a diagram showing the result of calculation of the trajectory of the central axis of an oxygen jet simple substance by equation (1) while changing the nozzle diameter d ₀ .

[Explanation of symbols]

S: Oxygen jet central axis moving distance (mm) θc: Oxygen jet spread angle (20 °) θ ₀ : Nozzle angle (angle from vertical axis) (°) d: Oxygen jet diameter at S ( mm) d ₀ : Nozzle diameter (mm) U ₀ : Oxygen gas flow velocity at the nozzle outlet (mm / s) ρ _s : Density of molten slag (g / cm ³ ) ρ _g : Oxygen gas density at the nozzle outlet (g / cm ³ ) ρ _g ': Oxygen gas density (g / cm ³ ) in the oxygen jet when the oxygen gas pressure is assumed to be 1 atm (oxygen gas density is constant in the oxygen jet)

Claims (1)

[Claims] 1. A top-and-bottom blow converter, in which a flux containing CaO and Fe _t O as main components is added, and it is increased by top-blown oxygen.
A hot-blown oxygen lance used for dephosphorization of hot metal while maintaining (% T.Fe), characterized by having a structure satisfying the conditions of the following formulas (1) to (3). Top blowing oxygen lance for phosphorus. [Equation 1] α ≤ θ ₀ ≤ β ... (2) γ ≤ d ₀ ≤ δ ...・ ・ ・ ・ ・ ・ ・ ・ (3) However, d ＝ 2S ・ tan (θc / 2) ・ ・ ・ ・ ・ ・ (a) S ＝ ∫ {(dX) ² + (dY) ² } ^1/2 ... (b) X: Horizontal displacement of oxygen jet central axis (mm) Y: Vertical displacement of oxygen jet central axis (mm ) S: Moving distance of the oxygen jet central axis in the traveling direction (mm) θc: Oxygen jet divergence angle (20 °) θ ₀ : Nozzle angle (angle from the vertical axis) (°) H: During oxygen jet at S Hold-up of oxygen gas (
−) D: Oxygen jet diameter at S (mm) d ₀ : Nozzle diameter (mm) U ₀ : Oxygen gas flow velocity at the nozzle outlet (mm / s) ρ _s : Density of molten slag (g / cm ³ ) ρ _g : Oxygen gas density at the nozzle outlet (g / cm ³ ) ρ _g ': Oxygen gas density in the oxygen jet assuming that the oxygen gas pressure is 1 atm (that is, the oxygen gas density is constant in the oxygen jet) (g / cm ³ ) g: Gravitational acceleration (m / s ² ) α: Nozzle angle when the orbit of the oxygen jet central axis contacts the hot metal surface (°) β: When the oxygen jet reaches half the distance between the lance and the hot metal surface Angle and the angle when the oxygen jet directly hits the furnace wall (°) γ: Nozzle diameter (mm) when the orbit of the oxygen jet central axis is in contact with the hot metal surface δ: Oxygen jet lance -Nozzle diameter when reaching half the distance between the hot metal surfaces (mm) Initial condition: X = d ₀ · cos θ ₀ / {2tan (θc / 2)}, Y = −d ₀ · sin θ ₀ / {2tan (θc / 2)} ・ ・ (c) dY / dX ＝ −tan θ ₀・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (d)