KR100362486B1 - A material for pretreating pig iron - Google Patents

Abstract

The present invention relates to a molten iron pretreatment for treating impurities contained in molten iron drawn out from a blast furnace by using by-products generated in a steel mill, more specifically, slag floated on a continuous casting ladle.

The molten iron pretreatment material of the present invention is 35-45 wt% CaO, 6-12 wt% MgO, 5-25 wt% Al ₂ O ₃ , 13-25 wt% T-Fe, 3-6 wt% MnO, SiO ₂ 8 -12% by weight, P ₂ O ₅ 0.8-2.5% by weight, S 0.02-0.05% by weight, TiO ₂ 0.6-1.2% by weight and other unavoidably contained impurities, manufacturing costs compared to conventional molten iron pretreatment It is inexpensive and combines dephosphorization, desulfurization and desulfurization functions, facilitates slag composition, prevents the restoration of impurities, and reduces the wear and tear of processing facilities, thereby improving product productivity.

Description

A material for pretreating pig iron}

The present invention relates to a molten iron pretreatment material for use in the process of removing impurities contained in the molten iron from the blast furnace after the steelmaking process. More specifically, in the present invention, after the steelmaking process, impurities such as S (sulfur), P (phosphorus) and Si (silicon) contained in the molten iron drawn out from the blast furnace are formed by vaporization or slag and separated from the molten iron. The present invention relates to a molten iron pretreatment material for facilitating refining operations in a Linze Donawitze Stirring Converter (LDS) converter.

In general, the quality of steel and its defects are determined by the content of impurities contained in the molten iron from the blast furnace, so the pretreatment to separate it from the molten iron is an important process to determine the quality of the product. . As such molten iron pretreatment materials, Na ₂ CO ₃ system, CaC ₂ system, CaO system, CaCO ₃ system, MgO system, CaMgCO ₃ system and the like have been generally used.

Among them, Na ₂ CO ₃ , CaC ₂ , CaO and CaCO ₃ pretreatment materials are mainly used as desulfurization materials. Specifically, CaCO ₃ ash has a higher desulfurization rate than CaC ₂ , and is advantageous for forming bonds (crystal structures) at low temperatures, while having poor workability (ejection, etc.), and CaO 3 or CaC ₂ systems can be formed by applying a high temperature. Therefore, there is a disadvantage that the manufacturing cost is high. In addition, when CaO is used as a pretreatment material, impurities such as phosphorus and sulfur are recovered from slag into molten iron due to the excessive oxidative property of the slag itself, and the recovery rate increases as time passes after the pretreatment. The result is displayed.

MgO-based pretreatment material having desulfurization and dephosphorization effect among conventional pretreatment materials has a higher correction basicity (CaO + MgO / SiO ₂ + Al ₂ O ₃ + P ₂ O ₅ ) value as the content of MgO prevents impurity restoration. However, at the dehydration temperature of 350 ° C, CaMgCO ₃ starts to decompose and high temperatures are required to obtain MgO, which requires a high processing cost, and tends to maintain its bondability even at a high temperature of 2800 ° C. There is a disadvantage in that the workability is bad to use as a pretreatment material in the steelmaking and steelmaking process that work is carried out at a high temperature.

The composition of the conventional pretreatment material used for removing impurities in the molten iron is shown in Table 1 below.

Composition (wt%) of conventional molten iron pretreatment Composition (wt%) SiO ₂ CaO MgO Al ₂ O ₃ T-Fe Etc Remarks CaO system 1.5 91.0 1.5 - - 6.0 Other water content CaCO ₃ series 2.2 50.0 3.0 0.8 0.5 43.5 MgO system 1.5 45.0 37.0 - - 16.5 CaMgCO ₃ system 1.0 30.0 22.0 0.3 0.7 46

Among iron components, phosphorus, sulfur, and silicon may be necessary depending on the purpose of use of iron products, but since general steels generally act as impurities, a pretreatment material having a composition as shown in Table 1 above is used. Will be removed. When such a pretreatment material is used, the volatiles flying to the gas at the time of stirring become less, and most of it becomes slag and floats on the upper part of the molten iron. The slag floating above the molten iron should be removed, which is determined by the basicity (CaO / SiO ₂ ) in the slag. In other words, when the basicity is low, the phenomenon of restoring impurities into the molten iron appears severely, and the slag is difficult to remove.

Slag composition after treatment with molten iron slag and conventional pretreatment Composition (wt%) Fe ₂ O ₃ SiO ₂ CaO MgO Al ₂ O ₃ P ₂ O ₅ S MnO basicity Dedicated Line Slag 3-6 35-45 30-45 5-7 10-18 0.1-0.2 0.5-1.2 0.5-2.0 1.1-1.8 Melting slag after CaC ₂ treatment 0.1-1.0 25-35 40-50 2-8 5-15 0.1-0.25 0.1-5.0 2.0-5.0 1.5-2.5 Molten iron slag after MgO treatment 5-8 10-15 30-40 20-38 5-10 0.5-1.3 1.0-5.0 1.0-5.0 3.0-6.0

As shown in Table 2, the slag composition when using the CaC ₂ pretreatment material is low or similar to the SiO ₂ and P ₂ O ₅ % by weight, it appears that the weight% of CaO, MnO and S is high, It is relatively excellent in the desulfurization function, the basicity of 3% by weight or less, it can be seen that there is difficulty in the slag composition and post-composition removal work. On the other hand, when the MgO-based pretreatment material is used, the P ₂ O ₅ and S component contents and basicity are high, indicating that the dephosphorization and desulfurization effects are high, and it is advantageous to prevent the restoration of impurities.

Therefore, the present invention, in order to solve the problems of the conventional pretreatment material, by using the slag floating on the continuous casting ladle (Laddle) during the steelmaking process, impurities contained in the molten iron from the blast furnace, in particular, S, P, Si In removing the components, it is possible to smooth the composition of slag, prevent the restoration of impurities, and combine the effects of desulfurization, dephosphorization and desulfurization as well as inexpensive raw materials, and reduce the wear rate of equipment to improve product productivity. It aims to provide.

The molten iron pretreatment material of the present invention for achieving the above object is 35-45 wt% CaO, 6-12 wt% MgO, 5-25 wt% Al ₂ O ₃ , 13-25 wt% T-Fe, MnO 3-6 Weight percent, 8-12 weight percent SiO ₂ , 0.8-2.5 weight percent P ₂ O ₅ , S 0.02-0.05 weight percent, 0.6-1.2 weight percent TiO ₂ , and other unavoidable impurities.

The molten iron pretreatment material of the present invention can be produced using minerals as a raw material, but it is preferable to produce by-products generated in steel mills, in particular, slag floating on the continuous casting ladle during the steelmaking process. The flotation on the continuous casting ladle satisfies the conditions for the preparation of the molten iron pretreatment material having a powder degree of 88 μm or less for good condensation, collection, and decomposition, and having good low temperature decomposition and low water content. In addition to these basic conditions, there are also conditions that can be commercialized according to the addition of the coagulant combination.

In addition, in the case of using the pretreatment material of the present invention, compared with the conventional pretreatment material, the width of the calorie and temperature change is less advantageous in terms of workability.

Hereinafter, the present invention will be described in detail.

The CaO component contained in the pretreatment material of the present invention is preferably in the range of 35-45% by weight in order to combine with SiO ₂ to lower the slag.

In addition, although the MgO component has more content, it is excellent in the collection property of P, S, Si, etc. according to the bondability of slag, but it is preferable to contain in the pretreatment material about 6-12 weight% in proportion to CaO content.

Since cationic Ca, Mg, Na and anions S, P, and O are bound by Na ₂ SO ₄ , CaSO ₄ , MgSO ₄ , Mg ₂ P ₂ O _7, etc., depending on their crystal bonding structure, CaO, MgO and P ₂ O ₅ is advantageous as the content is higher depending on the bonding property.

Al ₂ O ₃ content is a bond promoter for MgO, CaO, and SiO _2. The higher the content, the better the slag fluidity and the coagulation power. However, the content of Al ₂ O ₃ is 5-25% by weight. It is preferable to make it contain.

On the other hand, T-Fe, an accelerator of impurity-containing composition in molten iron, acts as a center of bonding promoter between elements by the composition of FeO, and adjusts excessive decomposition composition according to the situation, and according to the bonding ratio of Al ₂ O ₃ and SiO ₂ It is preferable to set it as 13-25 weight%.

In addition, the higher the content of SiO ₂ component, the more advantageous for the desulfurization operation, but silicon is increased as the slag fluidity decreases to reduce the cohesive force, it is preferable to include as little as possible, the content of 8-12 in consideration of the basicity in the slag It is good to set it as weight%.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are presented to specifically illustrate the present invention, but the scope of the present invention is not limited by these examples.

<Example 1-5>

Melting pretreatment using slag on continuous casting ladle

The pretreatment material (Example 1-5) of the present invention was prepared by crushing the slag floating on the continuous casting ladle into a particle size of 88 μm or less.

The molten iron from the blast furnace is discharged equally at 230 t / ch, and before loading into the steelmaking converter, the CaO-based molten iron pretreatment material and the molten iron pretreatment material of the present invention (Example 1-5) are each blown at 1500 kg / ch. Thus, the produced slag was analyzed. The results are shown in Table 3 below.

Composition (wt%) SiO ₂ CaO MgO Al ₂ O ₃ MnO FeO S P ₂ O ₅ (others) Coagulation Composition Work result CaO-based pretreatment One 1.5 90.0 1.5 0.5 0.5 6.0 Good usually usually 2 1.3 91.2 1.5 0.5 0.5 5.0 Good usually usually 3 1.4 91.0 1.5 0.5 0.5 5.1 Good usually usually x 1.4 90.7 1.5 0.5 0.5 5.4 Good usually usually MgO-based pretreatment One 1.0 30.0 22.0 0.3 0.7 46.0 usually usually usually 2 1.0 31.0 22.5 0.4 0.5 44.6 usually usually usually 3 1.1 30.5 22.3 0.4 0.6 45.1 usually usually usually x 1.03 30.5 22.3 0.37 0.6 45.2 usually usually usually Example One 10.12 40.43 10.31 11.76 4.12 15.84 0.03 7.39 Good Good usually 2 10.20 39.26 9.74 12.65 4.95 14.16 0.02 9.02 Good Good usually 3 10.56 39.77 10.61 12.25 3.74 15.81 0.03 7.23 Good Good usually 4 10.65 39.26 10.42 12.68 4.65 14.93 0.03 7.38 Good Good usually 5 11.32 38.44 10.36 10.82 4.26 15.42 0.02 9.36 Good Good usually

In addition, the slag generated after the treatment with the molten iron pretreatment material of the present invention has a good agglomerated state, generally excellent in the composition state, and has a viscosity, it is easy to remove impurities, and also excellent workability.

The molten iron pretreatment material according to the present invention is manufactured by using slag on the continuous casting ladle generated as a by-product during the steelmaking process, and is a low-cost raw material, having both desulfurization, dephosphorization, and de-silification functions. It can effectively remove the contained impurities, and has high basicity to prevent the restoration of impurities, to facilitate the composition of slag, and to reduce the wear rate of equipment (used equipment) to prevent damage to equipment, thereby improving product productivity. To provide.

Claims (4)

CaO 35-45 wt%, MgO 6-12 wt%, Al ₂ O ₃ 5-25 wt%, T-Fe 13-25 wt%, MnO 3-6 wt%, SiO ₂ 8-12 wt%, P ₂ O ₅ 0.8-2.5 wt%, S 0.02-0.05% by weight, TiO ₂ 0.6-1.2 material hot metal pre-treatment including a% by weight, and other inevitably contained impurities. The method of claim 1, A molten iron pretreatment, characterized in that the basicity is 3.0 or more. The method according to claim 1 or 2, A molten iron pretreatment, characterized in that it is produced from the slag floating on the continuous casting ladle generated as a by-product in the steel mill. The method of claim 3, wherein A molten iron pretreatment, characterized in that produced through the process of crushing and sorting the slag floating on the continuous casting ladle.