JP2003105424A - Method for controlling blowing process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert an auxiliary raw material for refining into slag in a short time without using a fluorite while excluding an adverse effect caused by a mixture of metals even by using a refractory containing an alumina, in the case of blowing oxygen into an iron raw material for steelmaking in a converter. SOLUTION: In the control of the blowing process, a monolithic refractory (e.g. the monolithic waste refractory having >=15% apparent porous ratio and about 3-50 mm average grain diameter) as the alumina-containing waste refractory is used and the amount of the refractory is adjusted so that the slag produced when the refining is performed, saisfies the following equations (1)-(4). A=%CaO/(%SiO2 +%Al2 O3 +%T.Fe)=0.7 to 3...(1) B=%SiO2 /A=3 to 40...(2) C=%Al2 O3 /A=0.7 to 14...(3) D=%T.Fe/A=5 to 27...(4) Ratio (Ps/W) of collided pressure Ps of spouted oxygen in the blowing process to the mass W of the molten steel may be controlled to <=50 Pa/t.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a blowing process, in which an amorphous waste refractory material containing alumina can be effectively reused when blowing an iron raw material for iron and steel (such as hot metal) in a converter. And a method for manufacturing steel using this method.

[0002]

2. Description of the Related Art Alumina-containing refractory materials (alumina refractory materials, etc.) are used as steel refractory materials, etc. Most refractory materials are treated as industrial waste after use, and only a small part of them are used. Refractory is reused as a raw material for pouring tap iron in a blast furnace. However, alumina-containing refractory materials for steelmaking are often added with a small amount of metal fibers or wires in order to improve the strength during use, and the inclusion of these metals adversely affects reuse. That is, when fibers or wires are mixed, it is not possible to control the desired refractory composition, and it is not possible to exert a predetermined strength. Therefore, it is difficult to reuse it as a refractory material.

On the other hand, Japanese Unexamined Patent Publication No. 2000-104109 discloses a method for refining a molten metal in a reaction vessel lined with a refractory material using a slag containing 40 wt% or more of CaO and MgO in total. A method for reducing unslagged CaO and MgO in slag is disclosed, which comprises adding a substance containing 5 wt% or more of alumina (a nozzle refractory for continuous casting of steel, etc.) to a reaction vessel. This method is suitably applied to the smelting reduction refining of Cr ore, and for example, refining is performed by using a refractory scrap for continuous casting nozzle crushed to 300 mm or less and blowing for 67 minutes.

However, according to this method, since the Cr ore is smelting-reduced and refined, the processing time of one charge (batch) is 60 to 7 times.
It can take as long as 0 minutes, during which CaO can only be slagged, and cannot be applied to refining with a short processing time. For example, when refining steel in a converter, the smelting time is usually about 15 minutes, and CaO and the like cannot be slagged in such a short time even if a continuous casting nozzle refractory is used.

Further, when refining (dephosphorization) in a converter uses hot metal which has been preliminarily dephosphorized and desulfurized by hot metal pretreatment, since the Si content in the hot metal is low, the amount of SiO ₂ generated during refining is also high. Less. If the amount of SiO ₂ is small, the calcined lime added for dephosphorization in the refining furnace (converter) may become difficult to slag, so a large amount of SiO ₂ source is added to adjust the basicity (CaO / SiO ₂ ). In addition, it is necessary to add a large amount of agglomeration accelerator such as fluorspar. In particular, when refining steel with a high carbon concentration (for example, steel with a carbon concentration of 0.15% or more at the time of blowing), even if oxygen is supplied to the molten steel, the carbon burns before iron, so refining It is difficult for the iron oxide concentration in the slag to rise, and it becomes particularly difficult to slag the calcined lime added for dephosphorization. Therefore, it is necessary to add a large amount of slag formation accelerator such as fluorspar.

However, when a large amount of fluorspar is added, the slag generated after the converter refining contains a large amount of fluorine, and the slag is often used as a roadbed material or a raw material for civil engineering work. May be eluted little by little and cause soil pollution, which is an important issue for environmental conservation.

Although it is not an invention utilizing refractory materials,
Kaihei 8-157921 discloses a furnace of the upper and lower blow converter type.
Dephosphorization Fractions Consisting of Converter Slag and Iron Oxide
Slag and the basicity of the slag condition during treatment by weight%
(% CaO /% SiO₂) = 1.2-2.0, (Al₂O
₃) = 2 to 16%, (T.Fe) = 7 to 30%
A method for dephosphorizing by means of N is disclosed, for example, N in the embodiment.
o. In 8 (Table 2), the slag composition during the dephosphorization treatment was Ca.
O = 41 wt%, SiO₂= 23 wt%, T.I. Fe = 7
wt%, Al₂O₃= 10.2 wt%
Has been. In addition, Japanese Patent Laid-Open No. 9-59709 also discloses that
Blow converter type furnace is mainly composed of converter slag and iron oxide
The flux for dephosphorization
% Basicity (% CaO /% SiO)₂) = 1.2-2.
0, (Al₂O₃) = 2 to 15%, (T.Fe) = 7 to 2
Those who dephosphorize by controlling 5%, (MnO) = 5-15%
The method is disclosed, for example, No. 1 of the embodiment. 4 (Table 2)
Then, the slag composition during dephosphorization treatment is CaO / SiO₂
= 1.82, T.I. Fe = 23 wt%, MnO = 8.5w
t%, Al₂O₃= 6.8 wt% is stated
There is. Organized the compositions described in the examples of these publications
Then, in the case of JP-A-8-157921, A =%
CaO / (SiO₂+% Al₂O₃+% T. Fe) = 1.
0, B =% SiO₂/ A = 23, C =% Al₂O₃/ A =
10, D =% T. Fe / A = about 7, which is the case of JP-A-9-
In the case of 59709, A =% CaO / (SiO₂+
% Al₂O ₃+% T. Fe) = 0.7, B =% SiO₂/
A = 33, C =% Al₂O₃/ A = 10, D =% T. Fe
/ A = about 35. However, these JP-A-8-157
921 and JP-A-9-59709.
In the method, it takes time to form slag and it is inefficient.

[0008]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above circumstances, and its purpose is to blow an iron raw material (hot metal etc.) for steelmaking in a converter. Even if a refractory material containing alumina is used, it is possible to eliminate a bad influence due to metal mixing, and to provide a steel manufacturing method capable of slagging a refining auxiliary material (such as CaO) in a short time without using fluorspar. .

[0009]

As a result of intensive studies to solve the above-mentioned problems, the present inventor uses an amorphous refractory as a refractory containing alumina, and further produces it during blowing. It was found that by adjusting the amounts of the amorphous refractory and refining auxiliary materials (CaO etc.) so that the composition of the slag falls within a specific range, the adverse effects of metal contamination can be eliminated, and CaO can be rapidly slagged. By controlling the oxygen ejection pressure during blowing based on a specific calculation formula, the adverse effects of metal contamination can be eliminated, and C
The present invention has been completed by finding that aO can be converted into slag.

That is, the method for controlling the blowing step according to the present invention is such that when the iron raw material for steelmaking is blown in the converter, the alumina-containing amorphous waste refractory material (for example, apparent porosity of 15% or more, average particle size) is used. When using an amorphous waste refractory of about 3 to 50 mm) and other components as auxiliary materials, the composition of the auxiliary materials is such that the slag generated during blowing satisfies the following formulas (1) to (4). Adjust.

A =% CaO / (% SiO ₂ +% Al ₂ O ₃ +% T.Fe) = 0.7 to ₃ (1) B =% SiO ₂ / A = 3 to 40 (2) C =% Al ₂ O ₃ /A=0.7 to 14 (3) D =% T.Fe / A = 5 to 27 (4) [In the formula,% CaO,% SiO ₂ ,% Al ₂ O ₃ ,% T. F
e represents the CaO content (mass%), the SiO ₂ content (mass%), the Al ₂ O ₃ content (mass%), and the total iron content (mass%) in the slag produced during blowing, respectively.] Another method for controlling the blowing step according to the method is, when the alumina-containing amorphous waste refractory is used, for a predetermined period (for example, during the blowing step to the latter period), a jet calculated based on the following formula (5). Ratio of oxygen collision pressure Ps and molten steel mass W (Ps /
W) is controlled to 50 Pa / t or less.

Ps = C × (X ^* −X ₀ ^* ) ⁻² × [P ₀ (X ^* = 15) −P] (5) [where Ps is the collision pressure (Pa) of the jetted oxygen against the molten steel.
Indicates. C represents a numerical value calculated by the following formula (6),
X ^* represents a dimensionless distance calculated by the following formula (7), and X ₀
^{* Indicates} a dimensionless virtual origin calculated by the following equation (8). P ₀ (X ^* = 15) represents the absolute pressure (Pa) calculated by the following equation (9) when the dimensionless distance X ^* is 15, and P represents the atmospheric pressure (Pa).

C = −26.3 × M ² + 11.8 × M + 162 (6) X ^* = X / D (7) X ₀ ^* = 1.2 × M ² −0.6 × M + 2.2 (8) P ₀ (X ^* = 15) = [0.25 × M ² −1.1 × M + 1.43] × P ₀ (X ^* = 0) (9) (where M is M = The oxygen-sending velocity (Mach number) calculated by the velocity V ₀ (m / s) of the ejected oxygen / sound velocity V (m / s), and X is the distance (m) from the outlet of the oxygen introduction tube to the molten metal surface.
And D indicates the diameter (m) of the oxygen introducing tube outlet. P ₀ (X ^*
= 0) indicates an absolute pressure (Pa) when the dimensionless distance X ^* is 0)] A manganese component may be used as the other component, and the Ps / W is 50 Pa / t or less for a predetermined period. By controlling the MnO concentration in the slag generated during blowing,
You may adjust to 15 mass%.

The present invention also includes a method for producing steel by blowing an iron raw material for steelmaking using the method for controlling the blowing step.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION [Waste refractories containing alumina]
The alumina-containing refractory used as a waste material in the present invention is not a fixed refractory such as brick, but an irregular refractory (granular refractory, kneaded clay refractory, etc.). The amorphous refractory has a high porosity and efficiently reacts with the refining auxiliary materials (calcium component etc.) existing around the amorphous refractory. Therefore, as compared with other alumina sources, the melting point of the refining auxiliary material (especially CaO) can be lowered in a shorter time, and the slag can be rapidly slagged.

The apparent porosity of waste refractories containing alumina is
For example, it is 15% or more, preferably 20% or more, more preferably 25% or more. The higher the apparent porosity of the alumina-containing waste refractories, the more rapidly the other refining auxiliary materials (such as CaO) can be slagged. The apparent porosity of the waste refractory material is usually 50% or less, preferably 40% or less, and more preferably 30% or less.

The apparent porosity is JIS R 220.
5 can be measured.

The waste refractory material containing alumina may be appropriately crushed or powdered, and the average particle diameter of the waste refractory material after crushing or powdering is, for example, 50 mm or less, preferably 40 mm or less, and more preferably. It may be 30 mm or less. By finely pulverizing or pulverizing the waste refractory material, the solubility or meltability of the refractory material can be improved, and other refining auxiliary materials (calcium component etc.) can be slagged more rapidly.

If the average particle size of the waste refractories is too small,
When the waste refractory is thrown into the converter easily, the waste refractory may not function effectively, and the slag formation speed may be reduced. Therefore, the average particle diameter of the waste refractory material is usually 3 mm or more, preferably 4 mm or more, and more preferably 5 mm or more.

The alumina content in the alumina-containing waste refractory material is, for example, 30% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more. The higher the alumina content, the more effectively it can be used as a slagging agent for the auxiliary raw material for refining. The alumina content is usually 99% by mass.
It is about below (for example, 90% by mass or less).

The alumina-containing waste refractory may contain SiO ₂ . When SiO ₂ is contained, alumina-containing waste refractories can be used as a SiO ₂ source, and the amount of silicon components (fused stone, silica stone, serpentine, etc.) used for adjusting the basicity of converter slag can be reduced. . The SiO ₂ content of the alumina-containing waste refractory is, for example, 1 to 50% by mass.
About 5 to 20% by mass.

The alumina-containing refractory is an alumina-based refractory [(high) alumina refractory (for example, Al ₂ O ₃ content: about 50 to 98% by mass, SiO ₂ content: 1 to 50).
Mass% (high) alumina refractory material, alumina graphite refractory material (for example, Al ₂ O ₃ content: 30 to 70 mass%)
Degree, SiO ₂ content: 0 to 40% by mass of alumina graphite refractory, alumina chrome refractory (for example, A
l ₂ O ₃ content 30 to 70% by mass, SiO ₂ content: 1 to
Alumina chrome refractory of about 20 mass%), mullite refractory (for example, Al ₂ O ₃ content: 60 to 80 mass%, SiO ₂ content: mullite refractory of about 20 to 30 mass%) , Clay refractories (for example, Al ₂ O ₃ content:
30-50 wt%, SiO ₂ content: 40 to 80 wt%
Clay refractory), Jamot refractory (for example,
Al ₂ O ₃ content: 30 to 50% by mass, SiO ₂ : content of about 40 to 70% by mass, such as jammott refractory material) can be appropriately selected.

The alumina-containing refractory material may be used alone or in combination of two or more kinds.

[Smelting of Iron Raw Material for Steel Making (Blowing)] In the present invention, the waste refractory and other components are used as auxiliary raw materials, and the iron raw material for steel making [hot metal, scrap iron (scrap), etc.] is used in a converter. Refining to steel. A conventional method can be used for refining. For example, a converter capable of top blowing (upper blow converter such as LD converter, upper bottom blow converter, etc.) is used, and iron raw material for steelmaking is put into the converter. A method in which oxygen is fed from a top-blown oxygen introduction pipe (lance) and then blown can be used.

Although the hot metal may be used as it is,
In the present invention, the hot metal preliminarily dephosphorized and desulfurized by the hot metal pretreatment can be advantageously used. With hot metal pretreatment,
The Si content in the hot metal decreases, and in general, it may be difficult to slag the calcium component added for dephosphorization in a refining furnace (converter). The waste refractory is used and the amount of the waste refractory is adjusted so that the composition of the converter slag is within a specific range as described later, so other components (calcium component, etc.) can be easily slagged. it can.

The carbon concentration of the iron raw material for steelmaking is
It may be relatively high, and may be, for example, about 0.2 to 1% by mass. Refining raw materials with high carbon concentration (blown)
In that case, since the iron oxide concentration is unlikely to rise, it may be difficult to slag the calcium component, whereas
In the present invention, other components (such as calcium component) can be easily slagged for the same reason as in the case of the hot metal pretreatment described above.

The other components include calcium components (slaked lime, quick lime, limestone, etc.), silicon components (silica stone, pyrophyllite, serpentine, etc.), magnesium components (dolomite, magnesite, carnallite, etc.), manganese components ( Mn
Ores, Mn alloys, Mn-containing slag, and the like, and particularly ferromanganese). The calcium component is, for example,
It can be used as a dephosphorizing agent, and the silicon component is, for example,
It can be used as a basicity adjusting agent.

In the present invention, each component in the slag (refining slag) produced during blowing is adjusted by adjusting the constitution of the auxiliary raw materials (the refractory and other components) so that
Make it within the range of (4). By adjusting the composition of the auxiliary material, even when the refractory is reused, it is possible to eliminate the adverse effects of metal contamination in the refractory, and to eliminate other components (such as calcium components) in a short time without using fluorspar. Since it can be turned into slag, it can prevent insufficient dephosphorization. Furthermore, sloping can also be prevented, and there is no fear that productivity will decrease. In particular, when the alumina-containing amorphous refractory is used under the condition that the component amounts are adjusted to fall within the ranges of the following formulas (1) to (4),
The slag slag can be extremely efficiently (for example, in a short time) slagged by the slagging effect of adjusting the amount of the components and the high reactivity of the refractory material in combination.

A =% CaO / (% SiO ₂ +% Al ₂ O ₃ +% T.Fe) = 0.7 to ₃ (1) B =% SiO ₂ / A = 3 to 40 (2) C =% Al ₂ O ₃ /A=0.7 to 14 (3) D =% T.Fe / A = 5 to 27 (4) [In the formula,% CaO,% SiO ₂ ,% Al ₂ O ₃ ,% T. F
e represents the CaO content (mass%), the SiO ₂ content (mass%), the Al ₂ O ₃ content (mass%), and the total iron content (mass%) in the refining slag, respectively] [Equation 1] (4) is, as a whole, a calcium component (such as CaO) used for dephosphorization and the like, a silicon component (such as SiO ₂ ) used to lower the melting point of CaO, iron oxide (T.Fe), and an aluminum component. The compounding ratio with (Al ₂ O ₃ etc.) is specified.

Specifically, the parameter A of the above formula (1) is
Is CaO in the slag and Si as a melting point depressant.
O ₂ , T. The ratio of Fe and Al ₂ O ₃ is shown. The smaller this value, the easier CaO is to dissolve.

The parameter B, C or D of the above formula (2), (3) or (4) is SiO ₂ , Al _{2 in the} slag.
O ₃ , or T.I. It reflects the ratio of Fe and CaO.
Then, by comparing with the above-mentioned parameter A, rather than simply comparing with CaO, it can be used as a highly accurate index for the solubility of CaO and the purification efficiency (eg, dephosphorization efficiency).

The preferred range of A is 0.9 or more (particularly,
1 or more) and 2.5 or less (particularly 2 or less). Also,
The preferred range of B is 5 or more (especially 8 or more) and 30 or less (especially 14 or less). The preferred range of C is 1
It is above (especially 2 or more) and below 10 (especially below 7). The preferred range of D is 5 or more (particularly 7 or more), 19
It is below (in particular, below 15).

The amount of auxiliary materials (waste refractory and other components) to be added is not particularly limited as long as the components in the refining slag can be adjusted and the iron raw materials for steelmaking can be refined (such as dephosphorization). The amount of waste refractory to be added is usually about 0.1 to 10 kg, preferably 0.
It is about 5 to 7 kg. The amount of silicon component, calcium component, magnesium component, and manganese component added is 0.5 to 1 with respect to 1 t of the iron raw material for steelmaking.
0 kg (preferably 1 to 7 kg), 5 to 50 kg (preferably 10 to 20 kg), 3 to 20 kg (preferably 5)
~ 15 kg), 0.5-10 kg (preferably 1-7 k)
It may be about g).

The timing of feeding the above-mentioned auxiliary raw materials (by-product slag and other components) is not particularly limited, but usually by the middle of the blowing step, for example, the blowing step is 70% (preferably 50%) in terms of time factor. , More preferably 30%), preferably before the start of blowing or before charging the iron raw material for steelmaking,
Almost all amount (80% by mass or more, preferably 90% by mass or more, particularly 100% by mass, relative to the total amount of input) is added (or placed). By adding almost all the auxiliary materials by the middle stage of the blowing process, the slag slag can be promoted.

The starting point of the blowing step is the start point of the oxygen transfer from the oxygen introducing pipe. Further, the end point of the blowing process is when the steel reaches product suitability (for example, when the phosphorus content is 0.
015 mass% or less, and the C content becomes 0.50 mass% or less).

The time required for blowing is usually 30 minutes or less (about 10 to 30 minutes), preferably 20 minutes or less (10 to 10 minutes).
20 minutes), more preferably 15 minutes or less (10 to 1)
About 5 minutes).

In the blowing step, the oxygen supply strength (hard blow, soft blow, etc.) may be appropriately selected. In the present invention, soft blowing is often performed for at least a predetermined period, for example, hard blowing is performed at the start of blowing, and the blowing step proceeds by 30% or more (preferably 50% or more, more preferably 70% or more) depending on the time factor. Then, I often switch to soft blow. By soft-blowing for a predetermined period, the T. The Fe concentration can be increased, and the composition parameters A to D can be easily controlled.

Incidentally, even in the conventional case, the T. F
Although soft blow was used to increase the e concentration, the blow strength is controlled by the ratio (L / Lo) of the depth L of the molten steel due to the oxygen jet and the depth of the steel bath Lo (L / Lo). The use efficiency of oxygen for carbon (decarbonation efficiency) cannot be controlled. That is, the reaction between the slag metals cannot be accurately controlled, and the T.S. The Fe concentration cannot be controlled accurately. On the other hand, in the present invention, the supply strength of oxygen is controlled by the ratio (Ps / W) between the collision pressure Ps of ejected oxygen and the molten steel mass W calculated based on the following formula (5) and FIG. And Ps / W is 50 Pa during soft blow.
It is controlled below / t. That is, in this method, since the collision energy of the oxygen jet is defined by the value per unit mass of molten steel, the decarbonation efficiency of the oxygen jet can be controlled. As a result, the amount of oxygen used for other than decarburization (that is, oxygen that oxidizes the molten steel and increases the iron oxide concentration of the slag) can be controlled, and the T.O. Fe (iron oxide concentration) can be controlled to any value. Since the reaction between the slag metals can be accurately controlled in this manner, the T.O. The Fe concentration can be stably increased to 15% by mass or more.

Ps = C × (X ^* −X ₀ ^* ) ⁻² × [P ₀ (X ^* = 15) −P] (5) [In the formula, Ps is the collision pressure (Pa) of the jetted oxygen against the molten steel.
Indicates. C represents a numerical value calculated by the following formula (6),
X ^* represents a dimensionless distance calculated by the following formula (7), and X ₀
^{* Indicates} a dimensionless virtual origin calculated by the following equation (8). P ₀ (X ^* = 15) represents the absolute pressure (Pa) calculated by the following equation (9) when the dimensionless distance X ^* is 15, and P represents the atmospheric pressure (Pa).

C = −26.3 × M ² + 11.8 × M + 162 (6) X ^* = X / D (7) X ₀ ^* = 1.2 × M ² −0.6 × M + 2.2 (8) P ₀ (X ^* = 15) = [0.25 × M ² −1.1 × M + 1.43] × P ₀ (X ^* = 0) (9) (where M is M = The oxygen-sending velocity (Mach number) calculated by the velocity V ₀ (m / s) of jetted oxygen / sound velocity V (m / s), and X is the distance (m) from the outlet of the oxygen introducing pipe to the molten metal surface.
And D indicates the diameter (m) of the oxygen introducing tube outlet. P ₀ (X ^*
= 0) indicates the absolute pressure (Pa) when the dimensionless distance X ^* is 0)] FIG. 1 shows the variables D, X, X ^* , and P of the equations (5) to (9).
^{_{s, P 0 (X * =}} 0), P 0 (X * = 15), is a device schematic diagram for explaining the concept of X ₀ ^*. That is, the variable D is
The diameter (m) of the outlet of the oxygen introducing pipe 2 is shown, and the variable X shows the distance (m) from the outlet of the oxygen introducing pipe 2 to the molten metal surface 1. The variable X ^* is a value obtained by dividing the variable X by D, and has the same axis as the variable X. That is, at the outlet of the oxygen introducing pipe 2, X ^* = 0, and the value of X ^* is 1 for each distance X / D.
It increases, and X ^* = D on the surface 1. Ps represents the collision pressure of ejected oxygen on the molten metal surface 1 (that is, X ^* = D), and P ₀
(X ^* = 0) indicates the absolute pressure (Pa) at the outlet of the oxygen introducing pipe 2, and P ₀ (X ^* = 15) is at the position where the distance X / D from the outlet of the oxygen introducing pipe 2 is 15. Indicates absolute pressure (Pa). X ₀ ^* is
The above-mentioned constant distance (critical distance) when oxygen ejected from the nozzle at a high speed (for example, supersonic speed) proceeds with almost no deceleration up to a certain distance and starts decelerating after exceeding a certain distance.

In particular, during soft blowing, the ratio Ps / W calculated based on the equation (5) and FIG. 1 is set to 50 Pa / t.
The following (for example, 10 to 50 Pa / t, preferably 10 to
40 Pa / t, more preferably 10-30 Pa / t)
When the manganese component is used as the other component, the MnO concentration in the slag can be controlled to 5 to 15% by mass, and the slag slag can be promoted when the manganese component is used as the other component.

According to the present invention, although the refractory material is reused and blown, the slag generated during the blow can be surely converted into slag, so that dephosphorization by other components (calcium component, etc.) can be achieved. It can be done reliably. That is, the obtained steel is comparable to conventional steels in terms of quality, and can be used for various purposes, despite refining by recycling waste refractories.

[0043]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately applied within the scope of the above and the following points. It is of course possible to make changes and implement them, and all of them are included in the technical scope of the present invention.

Examples 1 to 4 and Comparative Examples 1 to 4 In the examples, the hot metal and scrap were smelted using the upper and lower blowing converter shown in FIG. That is, in the upper-bottom blowing converter of FIG. 2, a converter main body 3 having an opening in the upper portion, a steel raw material 5 charged into the converter main body 3 and a slag 4 generated at the time of blowing gas from the bottom side. A bottom-blowing gas pipe 6 for blowing air and an oxygen introduction pipe (oxygen lance) 2 for blowing oxygen from the upper side of the iron raw material 5 for steelmaking and the slag 4 are provided.
In the example, 100 tons of hot metal and scrap were charged into the converter body 3 as the iron raw material 5 for steelmaking, and the auxiliary raw materials (alumina-containing amorphous waste refractory, silica stone, fluorite, calcined lime, Light burned dolomite, FeMn, etc.) were charged into the converter body 3 from the auxiliary raw material charging hopper 8 provided above the converter body 3 through the upper opening of the converter 3.
Then, oxygen was supplied from the oxygen lance 2. The blow strength of the oxygen-sending at the time of supplying oxygen (blowing process) is as shown in FIG. 3, and in Examples 1 to 4 and Comparative Examples 2 to 3, the collision pressure in the first half of the blowing process is 50% (time basis). The ratio Ps / W between the Ps and the molten steel mass W is controlled to 70 Pa / t, and the latter half of the blowing step 50
% (Time basis) of the Ps / W was controlled to 30 Pa / t. In Comparative Example 1, Ps / W in the first half 50% (time base) of the blowing process was controlled to 70 Pa / t, and the second half 50%.
(Time base) Ps / W was controlled to 60 Pa / t.

The amorphous waste refractory had an apparent porosity of 17% and was sized to a particle size of about 10 to 50 mm. The composition is as follows: Al ₂ O ₃ content 85% by mass, SiO ₂ content 10% by mass, MgO content 3% by mass, metal (stainless steel) content 2
It was mass%.

As hot metal, hot metal pretreated was used. The composition was as follows: C content 4.00% by mass, Si content trace (trace), Mn content 0.15% by mass, P content 0.
The content is 020% by mass, the S content is 0.020% by mass, and the balance is substantially iron.

During smelting, the degree of slag formation of the refined slag is visually observed, and the composition of the slag is analyzed to obtain the above formula (1)-
The composition parameters A to D calculated by (4) were calculated.

The P content and C content of the obtained steel were measured and the suitability of the steel for products was judged according to the following criteria.

O: P content is 0.015% or less and C content is 0.
Table 2 shows the results in which the P content of 40 to 0.45 mass% exceeds 0.015%.

[0050]

[Table 1]

[0051]

[Table 2]

As is clear from Table 2, according to the method of the example, an amorphous waste refractory is used as the auxiliary raw material, and the auxiliary raw material is added so that the slag produced during blowing has a specific composition. Therefore, the degree of slag formation of the refined slag can be improved, and further the product suitability of the obtained steel can be satisfied. On the other hand, according to the method of Comparative Example, since the slag generated during blowing does not have a specific composition, insufficient slag formation or excessive slag formation occurs, resulting in insufficient dephosphorization, and the obtained steel Cannot be used as a product.

Further, the above Examples 1 to 4 and Comparative Examples 1 to
In 4, the fluorine concentration (mass%) in the slag produced during blowing was measured. Further, the amount of fluorine eluted from this smelting slag was measured as follows.

[Measurement of Fluorine Elution Amount (mg / l)] Small and medium gravel is removed from the collected slag, and after coarse crushing, a powdery slag is obtained by passing through a metal sieve having an opening of 2 mm.
After thoroughly mixing the powdery slag, the powdery slag is added to hydrochloric acid diluted with pure water (pH after dilution = 5.8 to 6.3) to a concentration of 10 w / v%. The volume of the dilute hydrochloric acid solution of the powdery slag (hereinafter referred to as the sample solution) is 5
Sufficient dilute hydrochloric acid is used so that the amount is not less than 00 ml.

The sample solution is continuously shaken for 6 hours using a shaker. The fluorine concentration in the sample solution after shaking is measured according to the method listed in Appendix Table 6 of the Environmental Agency Notification No. 59, December 1972.

The results are shown in FIGS. 4 and 5.

As is clear from FIGS. 4 and 5, since fluorite is used in Comparative Example 4, a large amount of fluorine may be eluted to cause soil pollution. On the other hand, in the embodiment, since waste refractory is used instead of fluorite, there is no risk of fluorine elution and there is no risk of soil contamination.

Examples 5 to 8 Aluminium-containing amorphous waste having an apparent porosity of 5% (Example 5), 10% (Example 6), 20% (Example 7), or 25% (Example 8) The same procedure as in Example 3 was performed except that a refractory material was used. The time-dependent change in the dissolution index (degree of slag formation) of the calcined lime was measured for each example.

The dissolution index was determined as follows. That is, when the CaO component such as calcined lime charged in the furnace is in a sintered state, it is not slagged (dissolution index = 0.0),
The case where forming slag was generated was regarded as good (dissolution index = 1.0), and the degree of slagging (dissolution index) during that time was divided into a plurality of stages and evaluated visually.

The results are shown in FIG.

As is apparent from FIG. 6, the higher the apparent porosity of the waste refractory material, the more quickly the calcined lime becomes slag.

Experimental Example 1 The procedure of Example 3 was repeated except that the average particle diameter of the refractory material was changed within the range of 1 to 50 mm. The dissolution index of the calcined lime was measured 15 minutes after the start of blowing.

The results are shown in FIG.

As is apparent from FIG. 7, the average particle size is 3 to
Within a range of about 50 mm, calcined lime can be slagged very quickly.

Experimental Examples 2 to 8 Ps / W in 50% of the latter half of blowing was 10 Pa / t (Experimental Example 2), 20 Pa / t (Experimental Example 3), 30 Pa / t (Experimental Example 4), 40 Pa / t (Experimental) Example 5), 50 Pa / t (Experimental Example 6), 60 Pa / t (Experimental Example 7), or 70 Pa / t
Example 3 was repeated except t (Experimental Example 8).
The MnO concentration in the slag was measured for each experimental example.

The results are shown in FIG.

As is apparent from FIG. 8, Ps in the latter half of blowing
The smaller the / W, the higher the MnO concentration can be.

[0068]

EFFECTS OF THE INVENTION According to the present invention, an amorphous refractory is used as a refractory containing alumina, and the composition of the slag produced during blowing is within a specific range for refining the amorphous refractory and refining. Since the amount of auxiliary materials (CaO etc.) is adjusted or the oxygen ejection pressure is controlled based on a specific calculation formula, the adverse effects of metal contamination can be eliminated, and refining is possible without using fluorite. Auxiliary raw materials (CaO, etc.) can be turned into slag in a short time.

[Brief description of drawings]

FIG. 1 is a conceptual diagram for explaining a blowing method of the present invention.

FIG. 2 is a schematic view of a converter used in the blowing method of the embodiment.

[Fig. 3] Fig. 3 is a graph showing the relationship between the degree of progress of blowing (time standard) and Ps / W in the example.

FIG. 4 is a graph showing the fluorine concentration in refining slag in Examples 1 to 4 and Comparative Examples 1 to 4.

FIG. 5 is a graph showing the elution amount of fluorine from the refining slag produced in Examples 1 to 4 and Comparative Examples 1 to 4.

FIG. 6 is a graph showing the relationship between blowing time and dissolution index.

FIG. 7 is a graph showing the relationship between the average particle size of waste refractories and the dissolution index.

FIG. 8 shows the blow strength (Ps /
It is a graph which shows the relationship between W) and the MnO concentration in slag.

[Explanation of symbols]

1 ... Surface 2 ... Oxygen introduction tube 3 ... Converter body 4 ... Slag generated during blowing 5 ... Iron raw material for refining

Claims (7)

[Claims] 1. When blowing iron raw materials for steelmaking in a converter,
When the alumina-containing amorphous waste refractory and other components are used as auxiliary raw materials, a blower for adjusting the composition of the auxiliary raw materials so that the slag generated during blowing satisfies the following formulas (1) to (4) Management method of smelting process. A =% CaO / (% SiO ₂ +% Al ₂ O ₃ +% T.Fe) = 0.7 to ₃ (1) B =% SiO ₂ / A = 3 to 40 (2) C =% Al ₂ O ₃ / A = 0.7 to 14 (3) D =% T.Fe / A = 5 to 27 (4) [In the formula,% CaO,% SiO ₂ ,% Al ₂ O ₃ ,% T. F
e represents the CaO content (mass%), the SiO ₂ content (mass%), the Al ₂ O ₃ content (mass%), and the total iron content (mass%) in the slag produced during blowing, respectively.] 2. When blowing an iron raw material for steelmaking in a converter,
When using alumina-containing amorphous waste refractory and other components as auxiliary materials, the ratio (Ps /) of the collision pressure Ps of jetted oxygen calculated based on the following formula (5) and the molten steel mass W is calculated for a predetermined period. A method for controlling a blowing process in which W) is controlled to 50 Pa / t or less. ^{Ps = C × (X * -X} 0 *) -2 × [P 0 (X * = 15) -P] ... (5) [ wherein, Ps is the collision pressure on molten steel jetted oxygen (Pa)
Indicates. C represents a numerical value calculated by the following formula (6),
X ^* represents a dimensionless distance calculated by the following formula (7), and X ₀
^{* Indicates} a dimensionless virtual origin calculated by the following equation (8). P ₀ (X ^* = 15) represents the absolute pressure (Pa) calculated by the following equation (9) when the dimensionless distance X ^* is 15, and P represents the atmospheric pressure (Pa). C = −26.3 × M ² + 11.8 × M + 162 (6) X ^* = X / D (7) X ₀ ^* = 1.2 × M ² −0.6 × M + 2.2 (8) P ₀ (X ^* = 15) = [0.25 × M ² −1.1 × M + 1.43] × P ₀ (X ^* = 0) (9) (where M is M = emitted oxygen) Oxygen transfer rate (Mach number) calculated by velocity V ₀ (m / s) / sonic velocity V (m / s), and X is the distance (m) from the oxygen introduction tube outlet to the molten metal surface
And D indicates the diameter (m) of the oxygen introducing tube outlet. P ₀ (X ^*
= 0) indicates the absolute pressure (Pa) when the dimensionless distance X ^* is 0)] 3. The method for controlling the blowing process according to claim 2, wherein the ratio (Ps / W) of the collision pressure Ps and the molten steel mass W is controlled to 50 Pa / t or less during the blowing process and the latter period. 4. A manganese component is used as the other component, and the Ps / W is controlled to 50 Pa / t or less for a predetermined period so that the MnO concentration in the slag generated during blowing is 5 or less.
The method for controlling the blowing process according to claim 2 or 3, wherein the method is adjusted to -15% by mass. 5. The apparent porosity of the amorphous waste refractory is 1
It is 5% or more, The management method of the blowing process in any one of Claims 1-4. 6. The average particle size of the amorphous waste refractory is 3 to 5
It is 0 mm, The management method of the blowing process in any one of Claims 1-5. 7. A method for producing steel by blowing an iron raw material for steelmaking by the method according to claim 1.