JP3503176B2 - Hot metal dephosphorizer for injection - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lime-based dephosphorizing agent used for blowing hot metal, and it is an object of the present invention to achieve an advantageous improvement in reaction efficiency without causing an increase in cost.

[0002]

2. Description of the Prior Art In order to reduce the load of converter refining and reduce the amount of slag generated, a pretreatment of hot metal is generally performed. In recent years, in such hot metal pretreatment, it is usual to first perform desiliconization treatment, and then perform dephosphorization and desulfurization treatment using soda ash or lime. However, when the dephosphorization treatment is performed using soda ash, there is a problem that it is difficult to effectively use the slag produced as a dephosphorization slag by-product. This is because Na ₂ O contained in the slag may react with water and elute.

Therefore, a lime-based flux is often used in a steelmaking plant which requires effective use of slag,
In that case, the basic composition of the dephosphorizing agent is mill scale or iron ore as the oxidizing agent, and calcium oxide as the fixing agent for the generated phosphorus oxide. However, when lime-based flux is used, it is cheaper than when soda ash is used and the use of dephosphorization slag is widespread, but on the other hand, the flux slagging property during dephosphorization is used. However, the reaction efficiency is low due to the poor quality, and there is a drawback that a large amount of flux is required to obtain hot metal having low phosphorus. Further, when the amount of flux used is increased, the hot metal temperature during the dephosphorization process is lowered, which causes a problem in the subsequent refining process, for example, the desulfurization process of the hot metal or the decarburization process in the converter.

As a solution to the above problem, for example, Japanese Patent Publication No. 37133/1992 proposes a method of improving the slag forming property by adding CaF ₂ or CaCl ₂ to the flux. However, the addition of such a halogen compound, as is well known, causes severe damage to the refractory material in the refining vessel, which is disadvantageous in that the refractory material cost increases.

Further, Japanese Patent Publication No. 56-33442 discloses that the components after firing are CaO: 60 to 70 wt% (hereinafter simply referred to as%), F
e ₂ O ₃ : 10 to 25%, Al ₂ O ₃ : 12 to 30%, TiO ₂ , SiO ₂ and
A slag-making agent (dephosphorizing agent) for iron refining containing 5% or less of each of MgO is disclosed. Although this dephosphorizing agent is not pre-melted, it becomes self-fluxing by firing,
Although it slags at 1400 ℃, it is difficult to say that the slagging property is sufficient because 60 to 70% of CaO is required to increase the dephosphorization efficiency.

Further, Japanese Patent Publication No. 57-37648 proposes a technique for improving the slagging property by forming a synthetic slag. This technology uses de-Si treated hot metal to remove C
De-P / C-reaction in an oxygen steelmaking furnace using a molded synthetic slag consisting of aO: 40-70%, Fe ₂ O ₃ : 50% or less, basic and / or neutral oxide: 10-30%. In this technique, it is expensive when the entire amount of the dephosphorizing agent is melted or fired in advance, and when it is used as a mixture, the slag is used. There was a problem in that the chemical conversion was insufficient.

The same applies to the technique disclosed in Japanese Patent Publication No. 58-55207. That is, Japanese Patent Publication 58-5
No. 5207 discloses a mixture of quick lime: 30 to 70% and iron ore and / or manganese ore: 30 to 70% (further one or more selected from fluorite, cryolite, colemanite and sodium carbonate or Mixture containing 20% or less of two or more)
Has a weight average diameter of 500 μm after firing or melting.
It is pulverized as follows, and quick lime and iron oxide and / or manganese oxide are made to coexist in the pulverized particles, but when the dephosphorizing agent is melted or calcined in advance, it is expensive. It had to be something like that.

[0008]

The present invention advantageously solves the above problems and has not only good slag-forming property and low cost, but also the essential function required as a dephosphorizing agent, that is, dephosphorizing agent. It is an object of the present invention to propose a dephosphorization agent for hot metal injection, which has various functions such as high efficiency (efficiency of utilization of oxygen for dephosphorization), no re-phosphorization, and little damage to refractories.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to achieve the above object, and as a result, as a dephosphorizing agent for blowing, raw materials pulverized through a melting process, powder raw materials, and the like. It is found that the intended purpose can be advantageously achieved by using not only each of them alone but also using the pulverized powder that has been melted and the raw material powder in combination, and adjusting the component composition within a predetermined range. Got The present invention is based on the above findings.

That is, the present invention comprises a mixture of a raw material pulverized through a melting process in advance and a powder raw material containing calcium oxide, the composition of which is CaO: 35-55%, SiO ₂ :
2 to 15%, FeO + Fe ₂ O ₃ : 25% or more, Al ₂ O ₃ : 0.5 to 8
%, MgO: 3 to 8%, P ₂ O ₅ : 5% or less. A hot metal dephosphorization agent for blowing (first invention).

Further, in the invention, in the first invention, the compounding ratio of the raw material crushed in advance through the melting process is 10 to 60%.
And the composition of the raw material is CaO: 20 to 50%, SiO ₂ : 5 to
_{15%, FeO + Fe 2 O} 3: 50% or _{less, Al 2 O 3: 0.5 ~10} %,
MgO: 3-10%, P ₂ O ₅ : 5.0% or less, and CaO / SiO
₂ : A hot metal dephosphorization agent for blowing (second invention), characterized by satisfying the range of 1.0 to 6.0.

In the present invention, the raw material which has been pulverized through the melting process in advance means that most of the raw material composition is not mixed alone but is once melted and then solidified. It means that the objects are connected to each other and are distributed almost uniformly. Converter slag, for example, is advantageously suitable as such. In addition, the powder raw material means an ordinary powder or granular material that has not been subjected to melting treatment or firing treatment, and such powder raw material is based on dust contained in exhaust gas discharged from various refining furnaces and lacks CaO and the like. It is preferable to add the necessary amount of the component. As described above, in the present invention, the cost can be further reduced by effectively using the waste materials such as the converter slag and various dusts as the raw material.

[0013]

The present invention will be described in detail below. The dephosphorization reaction of hot metal is expressed by the following equation (1). 3CaO ＋2 P ＋ 5FeO ＝ 3 CaO ・ P ₂ O ₅ ＋ 5Fe --- (1) Therefore, the dephosphorizing agent is an oxidizing agent of P in the hot metal, F
C that stabilizes eO, Fe ₂ O _{3 and the} oxidation product P ₂ O ₅
It is necessary to use aO at the same time, and the dephosphorizing agent mixed with these is blown into the hot metal by using a lance together with air, nitrogen gas, and argon gas. When the dephosphorization treatment is performed using the hot metal dephosphorization agent, desiliconization, demanganization, decarburization, etc. often proceed simultaneously. The chemical composition of the hot metal which has been previously subjected to desiliconization is usually C: 3.8-4.5.
%, Si: 0.05 to 0.20%, Mn: 0.05 to 0.30%, P: 0.050
.About.0.150%, S: 0.01 to 0.05%.

In the present invention, the amount of CaO in the dephosphorizing agent is set to 35.
The range is limited to ~ 55% because if the content is less than 35%, the slag composition after dephosphorization treatment is CaO / SiO ₂ ≧ 1.8%.
This is because it is difficult to maintain the slag composition, and in such a case, dephosphorization is likely to occur after the dephosphorization treatment. On the other hand, when it exceeds 55%, the slag composition after the dephosphorization treatment is CaO / SiO ₂ > 6.0. In many cases, the slag slag draining property from the processing container is significantly impaired. Here, the preferable range of the CaO / SiO ₂ ratio is 4.0 ≦ CaO / SiO ₂ ≦ 10.

The reason why the amount of SiO ₂ is limited to the range of 2 to 15% is that
Considering the amount of slag after desiliconization mixed in the processing container and the amount of SiO ₂ generated from Si in the hot metal that was simultaneously oxidized during dephosphorization treatment, CaO / SiO ₂ = 1.
This is to achieve 8 to 6.0.

The amount of FeO + Fe ₂ O ₃ is limited to 25% or more because the oxygen source required in the above reaction formula (1) is the most economical treatment condition (the dephosphorization agent blowing speed and the blowing time). This is because the dephosphorization treatment is performed while supplying the dephosphorization agent basic unit). Note that F
Although the upper limit of the amount of eO + Fe ₂ O ₃ is naturally determined in relation to other components, it is preferable to set it to about 70%.

The amount of Al ₂ O ₃ was limited to 0.5 to 8% because
If it is less than 5%, the slagging property of the dephosphorizing agent, which is a feature of the present invention, deteriorates, and not only the effect of improving the reaction efficiency is not sufficiently obtained, but also the damage to the refractory of the processing vessel becomes severe, while the ratio of 8% This is because if the amount is too large, the cost of the dephosphorizing agent only becomes high and no beneficial improvement effect is obtained.

The MgO content is limited to 3 to 8% because if it is less than 3%, the slag forming property of the dephosphorizing agent is deteriorated and a sufficient reaction efficiency improving effect cannot be obtained, like Al ₂ O _3. If it exceeds 8%, the wear-preventing effect of the refractory is improved, but the slagging property of the dephosphorizing agent is rather hindered, and a good reaction efficiency improving effect cannot be obtained.

The P ₂ O ₅ content is limited to 5% or less because if it exceeds 5%, not only the reaction rate at the time of dephosphorization decreases but also dephosphorization from the slab easily occurs after dephosphorization. . Particularly, in order to obtain hot metal with P ≦ 0.030% after dephosphorization treatment, P ₂ O ₅
It is preferable that ≦ 3%.

Although the proper component composition range of the dephosphorizing agent according to the present invention has been described above, in the present invention, it is necessary to include, as the dephosphorizing agent, a raw material which has undergone a melting process in advance, preferably in the range of 10 to 60%. There are the following advantages. (1) When the dephosphorizing agent is blown into the hot metal, the dephosphorizing agent easily penetrates into the hot metal from inside the carrier gas bubbles, and therefore the amount effectively used for dephosphorizing increases. It is considered that this is because a part of the dephosphorizing agent is melted in advance, so that the wettability of the dephosphorizing agent and the hot metal is good and the density of the raw material is increased. (2) Further, due to the effect of (1) above, the dephosphorization reaction site in the hot metal increases, so the efficiency of the dephosphorization reaction carried by the powder raw material is higher than that in the case where only the powder raw material is blown into the hot metal. improves. (3) Due to the reasons (1) and (2) above, since the slagging property in the hot metal is improved, the reaction of the formula (1) shown above proceeds with the liquid-phase dephosphorizing agent. The speed is high and the reaction efficiency is also improved.
Moreover, there is no need for a halide that is harmful to refractories. (4) Since it has undergone the melting process, the temperature drop during dephosphorization is smaller than that of the simple mixture. In order to realize the above effects, it is desirable to mix at least 10% or more of the raw materials that have undergone the melting process in advance. In addition, the effect is improved as the content of the raw material that has undergone the melting process is increased, but the addition of an excessively large amount causes a significant cost increase compared with the effect of improving the reaction efficiency, so the upper limit is about 60%. Is preferred.

Here, the chemical composition of the raw material which has undergone the melting process in advance is as follows: CaO: 20 to 50%, SiO ₂ : 5 to 15%, FeO + Fe
₂ O ₃ : 50% or less, Al ₂ O ₃ : 0.5-10%, MgO: 3-10
%, P ₂ O ₅ : 5.0% or less, and CaO / SiO ₂ : 1.0 to 6.0
It is preferable that the range is satisfied. This is because if each component satisfies the above range, (1) the desired dephosphorizing agent can be obtained at the most economical mixing ratio, and (2) the melting temperature at the time of pre-melting can only be lowered. This is because melting loss of refractory in the container can be reduced.

[0022]

【Example】

Example 1 Table 1 shows the chemical compositions of various raw materials used. The dephosphorizing agent (particle size: -1 mm) obtained by blending the various raw materials shown in Table 1 in the proportions shown in Table 2 was prepared with an L-shaped lance for 50 kg of molten iron produced in a high-frequency melting furnace. It was blown for 15 min with 40 l / min of air. The hot metal temperature at this time is 1350
℃, chemical composition of hot metal is C: 4.3%, Si: 0.12%, Mn: 0.
It was 10%, P: 0.120%, S: 0.020%. In addition, (T.Fe): 6.0%, CaO: 41%, on the hot metal surface before the experiment,
_{SiO 2: 33%, MnO:} 4%, Al 2 O 3: in advance 3 kg / t on location slag of 6% of the composition.

Table 2 summarizes the experimental results. In the table, No. 1 is a comparative example in which conventional CaO and iron ore powder are mixed, No. 2 is a comparative example in which conventional CaO and powdery raw material A are mixed, and Nos. 3 to 7 are dephosphorizing agents. This is a compatible example in which a premelt raw material is mixed.

[0024]

[Table 1]

[0025]

[Table 2]

As is clear from the table, when the dephosphorizing agent in which the premelt raw material is preliminarily blended according to the present invention is used,
In addition to the conventional dephosphorization rate and dephosphorization rate, the oxygen utilization efficiency for dephosphorization has been remarkably increased.

Example 2 For 200 t of hot metal in the tope shown in FIG.
A dephosphorizing agent having a composition ratio of o.7 was used as a delivery gas at 8 Nm ³ / min of air per minute at a blowing rate of 400 to 450 kg / min.
Total amount: 45 kg / t was blown into the hot metal using a dip lance with a diameter (inner diameter) of 40 mm. In FIG. 1, reference numeral 1 is a blowing lance, 2 is a topido car, 3 is a dispersion / reaction region of a dephosphorizing agent,
4 is a pressure gauge, 5 is a powder supply pipe, 6 is a valve, 7 is a dispenser, and 8 is a powder tank. The hot metal temperature before the treatment was 1345 ℃, the chemical composition of the hot metal was C: 4.36%, Si: 0.12
%, Mn: 0.18%, P: 0.122%, S: 0.026%. As a result, the P content after treatment was 0.010%, and the P content when the conventional dephosphorizing agent of Comparative Example 2 was used under the same conditions.
A significant improvement effect was obtained compared to 0.045%. Also,
The temperature decrease after the treatment was 10 ° C. lower in the example than in the comparative example, and was 1285 ° C. after the treatment.

[0028]

As described above, according to the present invention, a dephosphorizing agent having good slag forming property, low cost, high dephosphorization efficiency (efficiency of utilization of oxygen for dephosphorization), and low re-phosphorization and damage to refractories can be obtained. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a hot metal dephosphorization procedure in an actual machine.

[Explanation of symbols]

1 blowing lance 2 Torpedo 3 Dispersion / reaction area 4 pressure gauge 5 Powder supply pipe 6 valves 7 dispensers 8 powder tank

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Sorimachi, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba, Kawasaki Steel Works Ltd. Technical Research Headquarters (72) Harushi Okuda 1-chome, Mizushima Kawasaki-dori, Kurashiki City No address) Kawasaki Steel Co., Ltd. Inside Mizushima Works (56) Reference JP-A 64-55315 (JP, A) JP-A 4-333506 (JP, A) JP-A 58-27915 (JP, A) Kaihei 6-287615 (JP, A) JP 59-94560 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21C 1/02 110

Claims (2)

(57) [Claims] 1. A mixture of a raw material pulverized through a melting process and a powder raw material containing calcium oxide, the composition of which is CaO: 35-55 wt%, SiO ₂ : 2-15 wt%, FeO + F.
e ₂ O _3: 25wt% or _{more, Al 2 O 3: 0.5 ~8wt} %, MgO: 3~
A hot metal dephosphorization agent for blowing, characterized by satisfying a range of 8 wt% and P ₂ O ₅ : 5 wt% or less. 2. The composition according to claim 1, wherein the raw material which has been pulverized through the melting process in advance has a compounding ratio of 10 to 60 wt%, and the composition of the raw material is CaO: 20 to 50 wt%, SiO ₂ : 5 to 15 wt%. , FeO
+ Fe ₂ O ₃ : 50 wt% or less, Al ₂ O ₃ : 0.5-10 wt%, MgO:
3-10 wt%, P ₂ O ₅ : 5.0 wt% or less, and CaO / Si
O ₂ : A hot metal dephosphorization agent for blowing characterized by satisfying the range of 1.0 to 6.0.