JPS61177314A - Sintered ore for dephosphorizing and desulfurizing molten pig iron or molten steel - Google Patents

Abstract

PURPOSE:To improve the slagging property and to accelerate dephosphorization and desulfurization by blending prescribed percentages of CaO, T.Fe, T.Mn, F and Cl and providing a prescribed basicity. CONSTITUTION:This sintered ore for dephosphorizing and desulfurizing molten pig iron or molten steel consists of, by weight, 20-40% CaO, 30-55% T.Fe, <=20% T.Mn, <=16% F and <=21% Cl and has >=4 basicity (CaO/SiO2). The sintered ore is formed by using calcium ferrite having a low m.p. as the principal component. When lumps of the sintered ore are added to molten pig iron, dephosphorization and desulfurization reactions proceed only by agitation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to dephosphorization and desulfurization treatment technology for hot metal and molten steel, and in particular to a dephosphorization and desulfurization process that effectively advances dephosphorization and desulfurization reactions in dephosphorization and desulfurization treatment. Regarding sintered ore.

Prior art and its problems In the method of performing dephosphorization and desulfurization treatment as a preliminary treatment of hot metal, the dephosphorization and desulfurization agents used for the dephosphorization and desulfurization treatment generally include an oxidizing agent such as an iron magnet and a fluxing agent such as fluorite. A mixture of lime and quicklime is used. In this case, in order for the dephosphorization and desulfurization reactions to proceed effectively, it is necessary to quickly slag the dephosphorization and desulfurization agent to form a highly basic slag even at relatively low temperatures such as the hot metal temperature. Therefore, the composition of the dephosphorization and desulfurization agent is generally determined so that its melting point is 1300° C. or lower. However, in the case of a simple mixed dephosphorization and desulfurization agent, quicklime, iron ore, etc., which have a high melting point of 1300°C or higher, are locally unevenly distributed when used alone, so slag formation is delayed during hot metal dephosphorization and desulfurization treatment, and dephosphorization is delayed. There was also the problem that the desulfurization reaction was also delayed. In order to solve this problem, a method has been proposed in which a powder composition obtained by sintering or melting a mixture of quicklime, iron ore, fluorite, etc. is used as a dephosphorizing agent (Japanese Patent Laid-Open No. 57-140809
) have been proposed, but this method involves sintering or melting using an external heat source to produce the dephosphorizing agent.
It is difficult to put it into practical use because the dephosphorizing agent is very expensive.

In addition, as for the CaO source necessary for dephosphorizing molten steel in a converter, quicklime obtained by calcining a single limestone using an external heat source is mainly used, and there is a limit to the increase in the dephosphorization reaction rate.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and is a low-cost, low-cost method that facilitates the formation of slag in the dephosphorization and desulfurization treatment of hot metal and molten steel and significantly accelerates the dephosphorization and desulfurization reactions. The purpose is to propose sintered ore for dephosphorization and desulfurization at a melting point.

Structure of the Invention The sintered ore for dephosphorizing and desulfurizing hot metal and molten steel according to the present invention is composed of CaCO, containing minerals such as limestone, and Ca(OH)z.
*More than 15 types of CaO4 in terms of CaO
36%, 38% or more of iron and manganese oxides such as iron ore, millscale μ, blast furnace dust, manganese ore, etc.
3-10% coke and 3-10% moisture were added to a blended feedstock containing up to 20% of a composition such as ~75% and fluorite containing alkaline earth metal fluorides and/or chlorides. It is characterized by being sintered using the heat of combustion of carbon in the coke stream and/or blast furnace dust as the main heat source.

The sintered ore for dephosphorization and desulfurization as a product obtained by limiting the raw materials for sintering as described above is Ca020
~40 wt%, T, Fe ao ~55 wt%, ・T
, M, 20wt% or less, F 15wt% or less, C
At 121 wt% or less, the basicity (CaO/5iOv) becomes 4.0 or more.

This invention will be explained in detail below.

As mentioned above, the sintered ore for dephosphorization and desulfurization according to the present invention is limestone* Ca (OH)! e It is sintered by adding coke to a mixture consisting of an inexpensive CaO source such as CaSO4, an oxygen source such as iron ore, mill scale, manganese ore, and a flux such as fluorspar + CaC4. By sintering the mixture in this way, the coke becomes a heat source and the degree of sintering progresses efficiently, resulting in CaOp Fe1O
1t2CaO・FezO3, Ca0・2Fe,
o.

Calcium ferrite with a low melting point is produced.

By the way, in order to effectively progress hot metal dephosphorization and desulfurization, it is necessary to increase the CaO content in the dephosphorization and desulfurization agent to 20 to 40% in order to ensure basicity and lower the melting point. When limestone is used as a raw material, it is necessary to reduce the limestone content to 30 to 55% in the raw material mixture, but in the case of the dephosphorization and desulfurization agent of this invention, sintering proceeds with high efficiency, so limestone is almost completely absorbed. Can be made into μsium ferrite.

By using this low melting point compound as a dephosphorization and desulfurization agent, slag formation becomes extremely easy even in hot metal dephosphorization treatment in a low temperature range, and the degree of dephosphorization is promoted.

Next, the reason why the raw material components of the sintered ore for dephosphorization and desulfurization are limited in this invention will be explained.

The reason why one or more of limestone, Ca(OH), and lcaso was limited to 25 to 62% is as follows.

In order to effectively progress hot metal dephosphorization and desulfurization, the basicity of the slag needs to be 3.0 or more.

In order to ensure this condition under standard hot metal dephosphorization conditions (dephosphorizing agent 50 kg/T, pre-treatment bath pig iron [5th t) = o, xs], CaO in the dephosphorizing and desulfurizing agent It is necessary to make it 20% or more. For this purpose, CaGO, containing minerals such as limestone in the raw material mixture + Cm (OH)! I Ca
5O.

The lower limit of is set as 1596 in terms of C and O. On the other hand, if the CaO in the dephosphorization and desulfurization agent exceeds 40%, the melting point of the dephosphorization and desulfurization agent itself becomes high and the reaction is delayed, so the upper limit is 36% in terms of CaO.
%.

Oxygen sources such as iron ore, mill scale, blast furnace dust, and manganese ore are limited to 38 to 75% because of CaCO and minerals containing e Ca(OH) s CaSO such as limestone.
This is because by setting the blending amount of No. 4 to 15 to 36% in terms of CaO, the balance becomes 38 to 75%. however,
If T and Mn in the dephosphorization and desulfurization agent are 13% or more, the melting point will increase, so it is preferable that the content of manganese ore be 50% or less.

Fluorite is added to further improve the dephosphorization and desulfurization properties of μsium ferrite, but the amount of addition is 2
If it exceeds 0%, the effect of fluorspar becomes saturated and the cost increases, so the amount of fluorspar added was set to 20% or less.

The reason why the amount of coke added was set at 3 to 10% is that less than 3% is insufficient as a heat source to advance sintering.
%, the heat source becomes excessive and at the same time, part of the reduction of iron oxide and manganese oxide progresses, increasing the risk of sintering of the sintered ore and the sintering machine. Moreover, if the coke ratio is too high, it will be disadvantageous in terms of cost.

The reason why the amount of water added is 3 to 10% is because if it is less than 3%, the permeability of the raw material will be poor and the productivity of the sintering machine will be reduced.
%, moisture distribution becomes uneven before sintering starts,
This is because this also results in a decrease in productivity.

The chemical composition of the sintered ore for dephosphorization and desulfurization as a product obtained by sintering the raw materials limited as above is cao
20-40 wt%, T, Fe 30-55 ft%.

T-Mn is 20wt% or less, F is 12wt% or less, but if the [%Sin,) in the dephosphorizing agent is high, C, which is effective for dephosphorization,
As O decreases and efficiency deteriorates, basicity (Cab/S
i Ox ) is preferably limited to 4.0 or more.

Table 1 shows typical chemical compositions of raw materials for sintered ore for dephosphorization and desulfurization according to the present invention.

(Leaving space below) Table 2 shows examples of blending conditions for sintered ore for dephosphorization and desulfurization according to the present invention, and Table 3 shows examples of sintered ore for dephosphorization and desulfurization sintered under the blending conditions shown in Table 2. An example of the chemical composition of concretion is shown in comparison with existing sintered ore for blast furnaces.

Table 2 Examples of sinter blending conditions Table 3 Examples of chemical composition of sintered ores As shown in Tables 1, 2, and 3 above, the sintered ores for dephosphorization and desulfurization of the present invention are , compared to existing sintered ore for blast furnaces [%CaO], basicity (Cm O/S i Ot
) is very high, making the composition advantageous for dephosphorization and desulfurization. In addition, X-ray diffraction of the sintered ore for dephosphorization and desulfurization and the sintered ore for blast furnaces revealed that the mineral phase of the sintered ore for blast furnaces was Fe! 0
1t CaO-2Fe201 is the main component, whereas sintered ore for dephosphorization and desulfurization is composed of CaO・Fe, O,,2Ca0
-ve, o, were the main characters. The results show that the sintered ore for dephosphorization and desulfurization of the present invention is mainly composed of calcium ferrite having a low melting point, and has good slagability, dephosphorization, and desulfurization properties.

Example 1 Figure 1 shows the amount of dephosphorization when the sintered ore for hot metal dephosphorization and desulfurization shown in Table 4 and the conventional mixed dephosphorizing agent were each added to hot metal in a 145-ton hot metal ladle by injection method. Shown below.

As is clear from the results shown in Figure 1, in the case of the dephosphorizing agent of the present invention, CaO quickly turns into slag due to the formation of low melting point oxides, so the CaO basic unit to obtain the same amount of dephosphorization is I was able to reduce it to a large extent.

(Leaving space below) Table 4 Example 2 The sintered ore for dephosphorization and desulfurization shown in Table 5 was added to the hot metal in a 145-ton hot metal pot using a combination of bulk addition and powder injection method to perform dephosphorization treatment. A comparison is shown in Figure 2.

From the results shown in FIG. 2, it can be seen that the addition rate of the dephosphorizing agent can be increased by the combination of bulk addition, and dephosphorization progresses more rapidly. That is, since the sintered ore for dephosphorization and desulfurization of the present invention has a low melting point, it is possible to proceed with dephosphorization simply by adding lumps to hot metal and stirring.

In addition, since the conventional mixed dephosphorizing agent (CaO type) has a high melting point, effective dephosphorization cannot proceed unless it is added to hot metal in the form of powder.

Table 5 Example 3 When the dephosphorization and desulfurization sintered ore and the blast furnace sintered ore shown in Table 6 were added to hot metal in a 35-ton hot metal ladle by injection method to perform dephosphorization and desulfurization treatment. The results are also shown in Table 6.

As is clear from Table 6, in the case of the sintered ore for dephosphorization and desulfurization of the present invention, since the slag basicity is sufficiently ensured, deSi, deP, and deS proceed together. In the case of condensation, only Si removal progresses.

(The following is a blank space) Effects of the Invention As is clear from the above examples, the sintered ore for dephosphorization and desulfurization of the present invention is mainly composed of calcium ferrite with a low melting point, so it is suitable for hot metal desorption in a low temperature range. Good slagability is obtained in phosphorus and desulfurization treatments,
Dephosphorization and desulfurization reactions are promoted. In addition, conventional CaO
In the case of dephosphorizing agents, effective dephosphorization could not proceed unless they were added to hot metal in the form of powder due to their high melting points.However, the sintered ore for dephosphorization and desulfurization of this invention Since it has a melting point, it is possible to proceed with dephosphorization simply by adding lumps to hot metal and stirring. therefore,
The cost required for crushing and injecting the dephosphorization and desulfurization agent becomes unnecessary. Furthermore, in the case of the sintered ore for dephosphorization and desulfurization of the present invention, the external heat source required for sintering is only a heat source for igniting the coke in the blended raw materials, and after that, the combustion heat of the coke is used to achieve extremely high efficiency. Since the sintering reaction proceeds, the manufacturing cost is much lower than sintering using an external heat source. Furthermore, in the case of the sintered ore for dephosphorization and desulfurization of the present invention, slag formation is promoted from the initial stage of blowing, which is advantageous for dephosphorization of molten steel in a converter. Not even.

[Brief explanation of the drawing]

Fig. 1 is a chart showing the influence of CaO basic unit on the amount of dephosphorization in Example 1 of the present invention, and Fig. 2 is a chart showing the change in hot metal [%P] during dephosphorization treatment in Example 2 of the same. It is.

Claims (1)

[Claims] 1 20 to 40 wt% of CaO, T.I. Fe30~55wt
%, T. Mn 20wt% or less, F16wt% or less, Cl
21 wt% or less, basicity (CaO/SiO_2)4.
A sintered ore for dephosphorization and desulfurization of hot metal and molten steel, characterized in that it consists of 0 or more. 2 CaCO_3-containing minerals such as limestone, Ca(OH)_
2. One or more of CaSO_4 in CaO conversion of 15~
36%, 38% or more of iron and manganese oxides such as iron ore, mill scale, blast furnace dust, manganese ore, etc.
Addition and mixing of 3 to 10% coke and 3 to 10% water to a blended raw material containing ~75% and 20% or less of a composition such as fluorite containing alkaline earth metal fluoride and/or chloride. A sintered ore for dephosphorization and desulfurization of hot metal and molten steel, characterized in that the sintered ore is sintered using the combustion heat of the carbon content in the coke and/or blast furnace dust as the main heat source.