JP4637528B2 - Molten iron making material and method of using the same - Google Patents

Description

  The present invention relates to a desulfurization refining material for efficiently desulfurizing hot metal or molten steel and a method for desulfurizing molten iron using the same. More specifically, the present invention relates to a desulfurization refining material and a desulfurization refining method used when melting low-sulfur steel from molten iron by means of secondary refining treatment or out-of-furnace refining treatment. In the present specification, hot metal and molten steel are hereinafter collectively referred to as molten iron.

  When impurities such as sulfur and inclusions are contained in the steel, the mechanical strength that determines the properties of the steel is significantly deteriorated. For this reason, it is necessary to remove, that is, refine, these impurities. Impurity refining is generally performed by so-called refining to remove impurities in the state of molten iron discharged from a blast furnace or in the state of molten steel to produce low-sulfur molten iron. As a means for obtaining the low sulfur value, various refining methods are established today and are widely used.

  Typical hot metal treatment includes injection refining of desulfurized material in a receiving vessel and stirring refining of hot metal and desulfurized material using a stirring blade. On the other hand, in the case of molten steel, desulfurization refining is possible through reduction refining in a steelmaking furnace. However, as a streamlined refining method in recent years, out-of-core refining that separates oxidation refining and reductive refining is widely used as a generalized method.

  In the case of the former hot metal desulfurization refining, since the temperature of the treated hot metal is low, it can be considered as a solid-liquid desulfurization reaction mainly composed of solids, and it is said that some gas desulfurization reactions are also performed in parallel. On the other hand, desulfurization refining with molten steel is refining under a liquid-liquid reaction between molten steel and slag. Therefore, the slag properties play an extremely important role. Slag used for refining is mainly made from quicklime based on its reaction characteristics.

  In addition to desulfurization refining, slag is used for diffusion deoxidation and inclusion refining, and plays a useful role in other steel refining processes. Slag is separated and refined from molten steel by reacting and adsorbing impurities in the steel through contact reaction with molten steel.

According to the description of the Chemical Dictionary, etc., the general mass% composition of slag is as follows.
Steel blast furnace _{slag, SiO 2; 31~37%, FeO} ; 1%, CaO; 40~50%, MgO; 1~6%, Al 2 O 3; 8~16%, MnO; a 8-13% , reduced slag composition range in basic steelmaking _{furnace, SiO 2; 8~20%, FeO} ; 0.5~5%, CaO; 40~50%, MgO; 5~15%, MnO; 0.5~ 3%.

  The main component of a general desulfurization material of hot metal or molten steel is lime-based. In addition, calcium carbide and soda ash are also available. Aluminum oxide, magnesia and calcium fluoride are also used for the purpose of improving the efficiency of refining.

  Each of these desulfurization materials has advantages and disadvantages. For example, when the main component is lime-based, the melting point of the main component quick lime is high and is in the range of about 2700 ° C. The refining temperature is about 1550 to 1600 ° C. even in the case of molten steel as well as in the case of molten steel. The reactant quicklime is in a solid state. As a result, the desulfurization reaction rate is slow and the desulfurization reaction time is long. Furthermore, there is a drawback that it is difficult to set conditions for the interfacial reaction between the molten iron and slag that governs the desulfurization reaction.

  The desulfurization material for hot metal, the main component soda ash system, generates a large amount of white smoke during the addition reaction to the molten iron, significantly lowers the temperature of the molten iron, and separates and discharges the steel slag at the end of refining. Have drawbacks.

Similarly, desulfurization refining by the main component calcium carbide system can provide an effective reaction, but generates troublesome acetylene gas during slag treatment after refining. In this case, since consideration for the environment cannot be missed, there is a disadvantage that the operation of the harmful measures becomes complicated.
If a two-component system other than the lime system is used, it is difficult to recycle the generated slag, and the slag separation / disposal operation is complicated.
For this reason, various improvement of the main component lime system which is easy to operate has been proposed.

  Patent Document 1 proposes to increase the reaction specific surface area by pulverizing quick lime to 4 mesh or less, preferably 16 mesh or less in a refining agent obtained by mixing aluminum slag and / or metal aluminum and quick lime. We recommend desulfurization refining, which uses gas to transport the refining agent to the molten steel. However, the desulfurized quicklime particles blown into the molten steel together with the carrier gas cannot secure sufficient contact time with the molten steel because of the high flotation speed in the molten steel, and react only for a very limited time. There is a drawback that it is difficult to control the reaction stably.

In Patent Document 1 and Patent Document 2, it is also proposed to add fluorite as a refining aid, but in the method described in Patent Document 2, the addition of fluorite (CaF ₂ ) causes the fluorine (% F) to be steel. It will be discharged in the slag.
Recently, wastewater treatment standards for harmful and pollutants have become strict due to social demands, wastewater from manufacturing processes, wastewater generated at garbage incinerators, wastewater discharged from steelworks and thermal power plants, floor washing wastewater, Wastewater such as smoke-washed wastewater discharged from garbage incineration plants often contains fluorine and other harmful and pollutants.

  Even in the steelmaking and steel refining process, fluorite has been used for a long time, and fluorine-containing slag has been used and discarded. Legal provisions already exist that the fluorine emission standards should not exceed 0.8 ppm on the soil elution basis and 0.4% on the soil content basis. Naturally, these slags that have been refined need to separate and remove harmful substances, etc., and meet the environmental waste disposal standards. However, since removal is extremely difficult due to the characteristics of elemental fluorine, there is a problem that it is difficult to use a sufficient amount in terms of desulfurization and refining alone. Furthermore, there is a drawback in that desulfurization refining and inclusion refining treatment methods must be reexamined or refining must be changed.

  It is also considered to add this as a refining material using the reactivity of metallic magnesium. However, magnesium is an element with a strong deoxidation and desulfurization smelting ability with respect to molten iron, its reactivity is extremely high, and it is difficult to operate alone under hot metal and molten steel temperature. Therefore, various methods have been proposed for use as an Mg alloy alloyed with components such as Fe, Si, Mn, and Al, and in special cases, coke is impregnated with Mg. However, (MgS) produced by the desulfurization reaction with Mg is unstable in the atmosphere, and reacts with oxygen in the atmosphere to (MgS) becomes (MgO) and [S], so that sulfur is regenerated. A so-called sulfation reaction occurs. In order to prevent this resulfurization reaction, it is preferable to simultaneously supply quick lime CaO to react with (MgS) to (MgO) and (CaS). Necessary. Furthermore, there are disadvantages that the removal time after refining becomes longer, the other operations become complicated, and the amount of slag increases, which also hinders recycling.

Therefore, in Patent Document 3, calcium aluminate (12CaO · 7Al ₂ O ₃ ) having excellent reactivity is added to compensate for the slow reactivity of fine powdered lime with a small amount of metallic magnesium that cannot be used in large quantities. It has also been proposed. Although this proposal is quite excellent in improving the reactivity and excellent in the desulfurization effect, it has a drawback that the material operation management for newly adding calcium aluminate becomes complicated.

Patent Document 4 introduces a technique for improving a problem caused by the refined material being a fine powder. In this document, in the case of a conventional desulfurization material, in order to prevent the powder from being blown away by the heated air current on the molten steel, a nozzle or a lance for blowing the desulfurization material powder into the molten steel must be immersed in the molten steel. For this reason, maintenance work of the nozzle and lance is required, and there is a defect in work operability.Because the desulfurization material is used directly as a lump, the reactivity is poor and the desulfurization effect cannot be expected. It proposes the use of square, rectangular and spherical briquettes in which the metal carbonate of the agent is mixed with CaO and has a particle size of 1 mm to 15 mm, that is, an apparent specific gravity of 1.3 kg / m ³ . The briquette has such a strength that it cannot be destroyed just by being introduced into the molten steel, and immediately after the addition, gas is generated and decomposed in the molten steel to become a fine powder. However, even in this technique, since the metal carbonate is thermally decomposed to generate gas, the briquette is immediately decomposed when it is put into the molten steel as a desulfurizing material, and the above-mentioned drawbacks are not sufficiently solved.

JP-A-1-139714 JP 2002-206108 A JP 2002-206109 A JP-A-7-188728

  The present invention has the disadvantage that the desulfurization reaction rate is slow and the desulfurization reaction time is long, the desulfurization material is likely to be unevenly distributed, the operation and management of refining materials are complicated, and the operability that satisfies the environmental waste disposal standards. An object of the present invention is to provide a steelmaking material that solves all of the disadvantages and can simultaneously produce satisfactory and stable quality steel, and a method for using the same.

The present inventor has intensively studied in order to solve the above problems, and has found a specific aggregate having a specific composition mainly composed of quicklime, and has achieved the present invention.
That is, the present invention has the following aspects (1) to ( 4 ).

(1) X-ray intensity of 40 to 70% by mass of quicklime particles having an X-ray intensity position 2θ (°) of 31.7 to 32.7 °, 36.9 to 37.9 °, and 53.4 to 54.4 °. Volume formed by pressure-molding 30 to 60% by mass of aluminum ash particles having a position 2θ (°) of 32.8 to 33.8 °, 34.7 to 35.7 °, and 38.1 to 39.1 °. 1 Ri Do from one aggregate rounded of 20 cc, average particle size of the quick lime particles are 75Myuemu～3mm, an average particle size of the aluminum ash 75Myuemu～2mm, the average particle of the aluminum ash particles diameter smaller than the average particle size of the crude lime particles, the aluminum ash particles covers the quicklime particles surface, molten iron Zokasuzai breaking strength of the agglomerates is characterized 30~50Kg der Rukoto.
(2) 20-50 mass% of quicklime particles having an X-ray intensity position 2θ (°) of 31.7-32.7 °, 36.9-37.9 °, 53.4-54.4 °, and X-rays 20-60 mass% of aluminum ash particles having an intensity position 2θ (°) of 32.8-33.8 °, 34.7-35.7 °, 38.1-39.1 °, and an X-ray intensity position 2θ ( °) Ri is Do from one aggregate rounded volume. 1 to 20 cc of the magnesia particles 20-50 wt% obtained by pressure molding of 42.4～43.4,61.8～62.8, the The average particle size of the quick lime particles is 75 μm to 3 mm, the average particle size of the aluminum ash is 75 μm to 2 mm, and the average particle size of the aluminum ash particles is smaller than the average particle size of the quick lime particles. ash particles covers the quicklime particles surface, molten iron Zokasu breaking strength of the agglomerates is characterized 30~50Kg der Rukoto .
( 3 ) The molten iron making material according to (1) or (2) above, wherein aluminum ash particles are embedded in the surface of the quicklime particles.
( 4 ) The molten iron forging material according to any one of (1) to ( 3 ) above is charged into molten iron or molten steel containing sulfur in an out-of-core smelting furnace or a secondary smelting furnace in a hot metal smelting or molten steel refining process. A method of using molten iron making material characterized by:

  By using the ironmaking material of the present invention, there is no uneven distribution of the desulfurized material, the desulfurization reaction time is shortened, the operation and management of the refining material becomes easy, and the operability for satisfying the environmental waste treatment standard is also good. Thus, it is possible to produce steel with stable quality.

The present invention will be described in detail and specifically below.
The molten iron making material of the present invention is composed of an aggregate composed of quick lime particles and aluminum ash particles, or an aggregate composed of quick lime particles, aluminum ash particles and magnesia particles. This agglomerate can be obtained by uniformly mixing the component particles and press-molding them in a mold. The preferable volume of the aggregate is 1 to 30 cc, more preferably 1 to 20 cc, and the size is preferably uniform.

  If the volume is less than 1 cc, it may be unevenly distributed in the slag on the molten iron, causing problems in rapid hatching, and also delaying desulfurization refining. In addition, when the volume exceeds 30 cc, it is too large to be poured uniformly into the hot metal or molten steel and even into the existing slag, and there are disadvantages that affect the desulfurization effect. It takes too much time to dissolve, causing difficulty in operability. Furthermore, the target desulfurization refining is delayed, which is not preferable.

  The shape of the aggregate is preferably a rounded shape. When the shape is all cubes, rectangular parallelepipeds, or sharp shapes with many rounded protrusions, it is not preferable for handling because it tends to chip due to frictional collision and become powdery. Since there are disadvantages that are difficult to obtain, the shape is more preferably an almond shape, for example, among the rounded shapes. The round shape is a specific shape with such roundness. In the case of transportation and storage as a sculpting material, there is almost no possibility of generating a powdery material due to impact. There is. Further, when it is introduced into the existing molten slag, it is easy to add it into the existing slag or molten iron from the fine powder, and the aggregate is easily present in the uniform heating reaction zone.

  The molten iron smelting material of the present invention forms an agglomerate, and the composition, shape, and volumetric capacity are in a specific range, and a hatching promotion measure is taken by decomposing the agglomerate by a metal salt of a gas generating agent by thermal decomposition. It can be easily melted and hatched in the slag field without any problems.

When the molten iron making material of the present invention is added to the molten iron or molten steel, it is exposed to the refining temperature region for a short time in the furnace or slag and heated, so that it can be blended with two or more raw materials as described above. Since it is an aggregate, after passing through a sintering (sintering) process, it transitions to a low melting point composition (12CaO.7Al ₂ O ₃ as the main composition), and melts at a molten iron refining temperature or lower, It will diffuse into the slag and contribute to refining. As a result, the above-mentioned problem of fine powder of quicklime does not occur, it is possible to eliminate the drawbacks of the conventional measures, and a surprising effect that does not exist in the prior art is derived. The molten iron smelting material of the present invention easily forms calcium aluminate at the time of use, but the calcium aluminate is synthesized in this way in order to rapidly hatch quick lime having a high melting point above the molten iron refining temperature. is there.

  For the purpose of destroying the aggregates at an early stage, the slag material may contain a metal carbonate that generates gas by thermal decomposition, but in that case, the aggregates are destroyed quickly by heating by thermal decomposition. A sufficient amount may be added, and the amount is usually 5% by mass or less of the total slag material.

The aggregate constituting the molten iron making material of the present invention comprises quick lime particles 40 to 70% by mass and aluminum ash particles 30 to 60% by mass, or quick lime particles 20 to 50% by mass and aluminum ash particles 20 to 60%. It consists of 20% by mass and 20-50% by mass of magnesia particles.
Moreover, the aluminum ash particle which comprises this aggregate normally contains 1-10 mass% of magnesia and silicon oxide, respectively.

  The quick lime in the present invention is a granular material represented by CaO, and in order to achieve the object of the present invention, one having a purity of 92 to 99 wt% is preferable. As this CaO, CaO obtained by baking limestone or CaO obtained by baking shells can be used. As shown in FIG. 1, the CaO has specific X-ray intensity positions 2θ (°) of 31.7 to 32.7 °, 36.9 to 37.9 °, and 53.4 to 54.4 °. It is a compound having absorption strength.

  This X-ray intensity position 2θ (°) was measured with an RAD-C type X-ray measuring apparatus manufactured by Rigaku Corporation. Cu / 40 KV / 30 mA, SCAN speed; 6.000 ° / min, sampling width; It is read from the chart measured at 020 °, scanning range; 5-70 °.

  The average particle diameter of the raw material CaO forming the aggregate is preferably 75 μm to 3 mm (based on the measurement method of JISK0069-1966). Moreover, it is preferable that the average particle diameter of the raw material aluminum ash particle | grains which form an aggregate is 75 micrometers-2 mm (based on a JISK0069-1966 measuring method). The particle size of the aluminum ash is preferably smaller than CaO because it is effective for producing calcium aluminate.

The raw material magnesia particles forming the aggregates preferably have an average particle diameter of 75 μm to 2 mm as measured based on the measurement method of JISK0069-1966. The amount of magnesia is 20-50% by mass. Magnesia is frequently used in the field for the purpose of improving the durability of smelting furnace materials. In other words, slag refining with intense stirring in the ladle will severely erode the refractory, so as a general measure, add dolomite material, which is a compound of quicklime and magnesia to the smelted slag. Is used to refine (% MgO) in slag, and this technique is publicly known and universalized. In this case, the content of (% MgO) in the slag is generally 10% or more and 15% or less.
In the present invention, magnesia particles are used as a raw material component of the slag material, and a basic refractory material is generally used as a slag zone refractory material in ladle refining treatment of molten iron, and magnesia refractory material is representative. Examples of such materials include non-fired magnesia carbon refractory materials and dolomite refractory materials, which are intended to extend the life of the refractory materials due to molten iron.

  The X-ray intensity position 2θ (°) of aluminum ash is 32.8 to 33.8 °, 34.7 to 35.7 °, and 38.1 to 39.1 ° as shown in FIG. There may be peaks of 35.6 to 36.6 °, 36.5 to 37.5 °, 37.5 to 38.5 °, and 59.0 to 60.0 °.

The main component of aluminum ash is alumina (Al ₂ O ₃ ), and metallic aluminum (Me—Al), magnesia (MgO), and silicon oxide (SiO ₂ ) are the main constituent components. These oxides are formed by being oxidized when aluminum alloy is melted and metal magnesium or metal silicon is added and alloyed.
Me-Al is a component of aluminum ash, when performing slag by adding a slag material of the present invention in a molten iron refining, iron oxide in the slag (% FeO and% Fe ₂ O _3, etc.) or oxidation Acts as a reducing material for reducing lower oxides such as manganese (% MnO), and can contribute to the improvement of desulfurization refining, which is the main purpose, and further to the improvement of the yield of Si alloy iron, which is a molten steel deoxidizing material. .

  Me-Al contained in aluminum ash which is a raw material of the ironmaking material of the present invention effectively acts on molten iron ironmaking refining. In general, the Me-Al component contained in the aluminum ash ranges from 5% to 60%, but in the present invention, a product containing 10% to 40% Al is preferable. In this case, the Me—Al content is preferably determined by the content of the lower oxide in the slag described above in order to optimize the refining conditions. Of course, even if the content of Me-Al is a low value, there is no problem with respect to the early synthesis of calcium aluminate, which is a low melting point compound.

Similarly, the MgO component in the aluminum ash has no harmful effect on molten iron refining and is an effective component in the present invention in connection with the aspect (2) of the invention. On the contrary, since the SiO ₂ component acts as an inhibitory component for refining, the lower the value, the better. It is preferable to use raw aluminum ash that is 5% or less.

  An X-ray chart when the aggregate in the present invention is heated at 1350 ° C. is shown in FIG. X-ray intensity position at 2θ (°) of 17.5 to 18.5 °, 32.8 to 33.8 °, and 36.1 to 37.1 ° at an aggregate having an extremely higher strength than other strengths. It may be easy to solve the object of the present invention.

  The agglomerate is produced by a dry pressure molding method by filling a predetermined slagging material material into a mold having a rounded concave mold (for example, almond shape). According to the description in the Chemical Engineering Handbook, as the mechanical properties of powder, when powder particles are pressurized, the distance between particles decreases, intermolecular force (Van der Waals force), liquid crosslinking force, electrostatic force acts. And agglomeration. Due to this cohesive force, the aggregate is solidified and molded.

  As one aspect of the method of using the molten iron molding material of the present invention, the mixed components for the molding material consisting of quick lime particles and aluminum ash particles are uniformly mixed for a predetermined time, filled in an almond mold, pressure To obtain a molded article with high breaking strength in which the distance between particles is reduced. Furthermore, by increasing the average particle size of quick lime and making the particle size of aluminum ash smaller than the particle size of quick lime, hard aluminum ash particles are embedded in the surface of soft quick lime particles, and the degree of adhesion between the particles increases. Therefore, a so-called preferable interparticle distance is obtained. In addition, since the aluminum ash excellent in thermal conductivity covers the surface of the quicklime particles, the calcium aluminate synthesis is facilitated as the aggregate is heated. This effect also contributes to an improvement in processing yield during molding. Since this aggregate uses quick lime softer than calcium carbonate, an aggregate having high breaking strength can be obtained. Even if the particle diameter of quick lime is too small, a hard aggregate is difficult to obtain.

  As another aspect of the method of using the molten iron molding material of the present invention, a mixed component for a molding material consisting of quick lime particles, aluminum ash particles, and magnesia particles is uniformly mixed for a predetermined time, and is placed in an almond mold. Filled and molded by applying pressure to obtain a molded article with high fracture strength in which the distance between particles is reduced. Furthermore, by increasing the average particle size of quick lime and making the particle size of aluminum ash and magnesia smaller than the particle size of quick lime, hard aluminum ash particles and magnesia particles are embedded in the surface of soft quick lime particles, as described above In addition, since the degree of adhesion between the particles increases, a so-called preferable inter-particle distance is obtained. In addition, since the aluminum ash excellent in thermal conductivity covers the surface of the quicklime particles, the calcium aluminate synthesis is facilitated as the aggregate is heated. This effect also contributes to an improvement in processing yield during molding.

A cross-sectional view observed by cutting the aggregate is shown in FIG. The cross-sectional structure is a structure in which the aluminum ash particles 2 surround the quick lime particles 1, and the aggregate has an appropriate hardness due to the structure in which the particles are in contact with each other in strength. In this case, the CaO compound is easily converted into calcium aluminate (12CaO · 7Al ₂ O ₃ ). As a result, an effect of facilitating dissolution in a considerably low temperature region than quick lime is obtained, which can lead to stable desulfurization refining. Moreover, since the aggregate has a higher bulk density than the powder by compressing and agglomerating, it does not float on the slag covering the surface of the molten steel at the time of addition in the furnace, so it will be immersed in the slag. The agglomerates are heated uniformly from the surroundings and are effective in shortening the ironmaking time, resulting in a surprising effect that leads to a shortening of the desulfurization refining time.

In addition, the hardness of the aggregate is preferably 10 to 50 kg in breaking strength in accordance with the object of the present invention. More preferably, it is 30-50 kg. If the breaking strength is less than 10 kg, the agglomerates are pulverized and high melting point CaO is present alone, so that hatching does not proceed well. That is, the production of 12CaO · 7Al ₂ O ₃ does not proceed smoothly, and the object of the present invention cannot be achieved, and also the problem of fine powder of quicklime is caused.
The numerical values of the breaking strength in the present invention denote the values measured with a Kiya type hardness meter.

The ironmaking material of the present invention is particularly effective for producing low-sulfur steel by secondary refining of molten iron. The molten iron in this case refers to the molten iron obtained by the iron ore reduction process, or the molten iron enriched with [% C] from the steel raw material to the eutectic region in the Fe—Fe ₃ C binary system. In addition, molten steel refined in steelmaking furnaces represented by converters that use hot metal as steel, processed steel scrap and commercial steel scrap are the main raw materials, and are melted using electric power or oil energy from an electric furnace or the like. Refers to molten steel.

  Typical secondary refining for the purpose of molten iron refining is the above-described refining of the desulfurization material into the receiving vessel and the hot metal stirring desulfurization refining with addition of the desulfurization material. On the other hand, in the case of molten steel treatment, there are two types of secondary refining: desulfurization material blowing refining into a receiving vessel, and desulfurization material-added hot metal stirring desulfurization refining. On the other hand, in the case of molten steel processing, LF (abbreviation of ladle furnace), ASA-SKF refining furnace, gas, which is published in 1981 and described in “Recent Advances in Special Refining Technology” published by the Japan Iron and Steel Association There is an in-furnace refining furnace for bubbling ladle refining, RH or DH type vacuum processing refining furnace, and other ladle vacuum processing refining furnaces, and an EBT type electric furnace with controllable slag in the melting furnace And ladle addition refining at the time of steel removal from the furnace as in the case of converters.

  LF refining furnace, which is a basic patent described in Japanese Patent Publication No. 52-23968 (name of the invention "reduction refining method of molten steel"), the technology of which was established in 1972, was later referred to as the LF furnace. Since the furnace adopts a slag refining method that places emphasis on the molten steel-slag interface reaction refining given kinetic energy by inert gas stirring as compared with other refining furnaces, the present invention It is particularly suitable for application.

When subjecting the ironmaking material of the present invention to the above-described target refining furnace and refining process, the case of performing refining by the independent addition of the ironmaking material of the present invention, and the combination of the combination of the ironmaking material of the present invention and quicklime There are cases where molten iron refining is performed. In this case, the addition of alloyed iron represented by Fe-Si and other deoxidizing and reducing materials for the purpose of deoxidation of molten iron or slag reduction to the refining region does not refuse anything, but gives a preferable refining environment, Good results will be obtained for the target molten iron refining.
In particular, the important factors that have an important influence on the refining results are the slag composition and the amount of slag in the refining environment.

The slag composition at the time of reductive refining mainly using desulfurization refining is (Fe ₂ O ₃ ) (CaS) in addition to the main component of (CaO) (SiO ₂ ) (Al ₂ O ₃ ) (MgO). Since these slag compositions and slag values have various values depending on the molten iron refining process, refining is required by adding the products of the present invention as determined. As an example, when refining by adding the product of the present invention to an existing molten slag, the basicity represented by (% CaO) / (% SiO ₂ ) targets 2.0 or more, and (% Al The value of ₂ O ₃ ) needs to be 5% by mass or more, preferably 10 to 20% by mass, because it gives a fluidity factor important for refining.

  The (% MgO) composition is intended to protect the refractory material of the smelting furnace from the molten slag. Further, a low value is desired for the (% Fe2O3) and (% CaS) compositions. From these, the composition range of the product of the present invention is changed and subjected to refining, and there is a correspondence of co-addition with quick lime for the purpose of increasing the basicity of molten slag and diluting (% CaS).

As described above, in the case of desulfurization refining of hot metal with metallic magnesium, a sulfur fixing operation (CaS) using quick lime is required in order to prevent resulfurization.
In order to prevent this resulfurization, a lot of time and labor must be spent and the desulfurization slag must be sufficiently separated, and when desulfurization treatment using lime system is performed using a ladle for hot metal separation As described above, the main component of the lime system is a solid at the smelting temperature of the molten metal, so that there is a disadvantage that the desulfurization reaction treatment time becomes long when the ultra-low sulfur steel is melted. Furthermore, since the separation time of desulfurization slag to the ladle for hot metal separation is required, there is a drawback that the desulfurization treatment time cannot be shortened. This causes difficulty in matching with the next process in which the operation time is limited. As a technique for improving this defect, there is a technique of Patent Document 3 in which a koji-making material containing calcium aluminate is previously used in molten iron. There are disadvantages that become complicated. The present invention can solve all of these various drawbacks.

In using the product of the present invention, for example, an argon gas bubbling refining method utilizing an inert gas during hot metal or molten steel refining can be used as necessary. It is recommended that this gas bubbling refining be used in combination as a means for maximizing the ironmaking and refining effects of the product of the present invention.
Further, the slag material of the present invention can contain an amount of fluorite in an amount not causing environmental pollution problems.

The present invention will be described based on examples.
[Example 1]
(Manufacture of ironmaking materials)
Quicklime particles having an X-ray intensity position 2θ (°) of 31.7 to 32.7 °, 36.9 to 37.9 °, and 53.4 to 54.4 ° (average particle diameter: 3 mm: manufactured by Chichibu Lime Industry Co., Ltd.) QA0-3) Aluminum ash particles (average particles) having 50% by mass and X-ray intensity position 2θ (°) of 32.8 to 33.8 °, 34.7 to 35.7 °, and 38.1 to 39.1 ° (2 mm in diameter) and 50% by mass were mixed for 10 minutes to obtain a uniform mixture. This mixed composition was filled into a plurality of rounded almond molds with a capacity of 7 cc and pressure-molded to obtain a slag-forming material having desulfurization ability. The mixed aggregate agglomerated material taken out from the mold after molding had a rounded almond mold, and had a volume of 7 cc and a bulk density of 1.8 g / cc. As a result of measuring this with a Kiyama-type hardness meter, the crushing strength was 30 kg. FIG. 4 shows a photograph of a cut cross section of the pressure-molded body. When the portion observed as a large particle shape indicated by reference numeral 1 in FIG. 4 was collected as a sample and subjected to component analysis, the CaO content was 97 mass%. Thereby, the particle | grains shown with the code | symbol 1 were able to identify with quicklime particle | grains. Moreover, the surroundings of the large lime particles were surrounded by fine aluminum ash particles, and it was observed that the aluminum ash particles were embedded in the quick lime particles. FIG. 3 shows an X-ray analysis chart when the koji material is heated to a heating temperature of 1350 ° C.
(Evaluation of ironmaking material)
Next, the product of the present invention and quicklime were added at a ratio of 1: 2 to the LF refining furnace, which is a typical molten steel out-of-core refining system, and subjected to refining. As a result, the value of [% S] in the molten steel was 0.035% by mass to 0.018% by mass, which was a very satisfactory desulfurization refining result.
The effect of desulfurizing and refining molten steel will be described in detail in Examples 2 and 3 below.

[Comparative Example 1]
A test piece was made of a koji material that was manufactured under the same conditions as described in Example 1 and was an agglomerate having a rectangular shape with no round shape.
First, as a first test, a test using a storage hopper receiver by dropping 700 mm through a 3 m long belt conveyor was repeated three times to investigate the ratio of powdering thereafter. As a result, in the classification test using a 2 mm screen, there was a difference in the pulverization phenomenon as much as 29% on average compared to the almond-shaped aggregate of Example 1.
Next, as a second test, the slagging material mixed with this powdery material was added to the LF refining furnace under the same conditions as in Example 1 and a desulfurization rate comparison test was conducted. The difference in the subsequent desulfurization speed was measured. As a result, compared with the almond shape product manufactured in Example 1, the desulfurization reaction rate of the slag material of Comparative Example 1 was reduced by 22% on average.

[Comparative Example 2]
Under the same conditions as described in Example 1, a comparative test for melt hatching was conducted using an aggregate having a shape volume of 35 cc as a test material.
Since it was difficult to observe the hatching status in the LF refining furnace, the hatching status was compared by comparing the desulfurization rate as in Comparative Example 1. As a result, the desulfurization speed 5 minutes after the addition of the ironmaking material of this comparative example was 29% lower on average than the 7 cc almond-shaped ironmaking material of Example 1 in volume.

[Example 2]
In this example, the agglomerate / molded body produced in Example 1 was subjected to ironmaking in an LF refining furnace and subsequent molten steel refining, and the hatching rate was confirmed. Moreover, the superiority was confirmed in comparison with refining in normal operation.

First, test conditions and evaluation methods will be described below.
<Test conditions and evaluation methods>
(1) Raw material blending ratio, raw material size, production method of the koji material of the present invention provided for implementation Blending ratio: Quick lime (raw material size 3 mm or less): 70% by mass
Aluminum ash (raw material size 2mm or less): 30% by mass
Production method: After mixing the above raw materials, it was molded and solidified into an almond shape by a roll molding machine.
Molded product size: Approximately 30mm x 20mm x 15mm
Fracture strength of molded products: range of about 15-30Kg

(2) Conditions for steelmaking used for steelmaking and molten steel refining Arc electric furnace: Type
Capacity 80 Ton
Secondary refining furnace: LF refining furnace (capacity: 80 Ton)
Test steel type: Structural carbon steel

(3) Outline of the steelmaking process used for ironmaking and molten steel refining Figure 5 shows the outline of the steelmaking process used for steelmaking and molten steel refining and the addition position of the steelmaking material used for molten steel refining. FIG. 5A shows the method of the present invention, and FIG. 5B shows the conventional method.
The melting and oxidation refining in the arc electric furnace was produced in the same way as the normal refining process. At the time of steel production, the addition of iron alloy and quicklime was a predetermined amount based on the work standards. After steelmaking, additional quicklime was added for the purpose of improving desulfurization refining and inclusion refining at the LF refining furnace position.

(4) Evaluation of the solubility of quicklime The solubility of quicklime was compared between the case where the product of the present invention was added in the early stage of LF refining and the case of normal operation, that is, the case of adding quicklime alone. The comparison was made by comparing the speed of hatching of quicklime newly added to the existing slag brought in during steelmaking.
The hatching rate of the added quicklime was measured by the ICP analysis method by sampling (mass% CaO) in the smelted slag at a certain elapsed time.

<Evaluation results>
In FIG. 6, the horizontal axis represents the elapsed time since the addition of the ironmaking material into the molten iron, and the vertical axis represents (mass% CaO) in the slag, and the relationship is plotted. The horizontal axis “0” indicates the time when quick lime or the product of the present invention and quick lime are added at the LF refining position, and the numerical value on the horizontal axis indicates the elapsed time (minutes) thereafter. Similarly, the vertical axis “0” indicates (mass% CaO) in the slag immediately before the addition of quick lime or the product of the present invention and quick lime, and the numerical value on the vertical axis indicates the quick lime or main lime at the subsequent LF refining position. (Mass% CaO) after the addition of the invention and quicklime is shown.

  The graph of ● shows the case by the method of the present invention, and the graph of ○ shows the case by the conventional method. From the results shown in FIG. 6, the difference between the case of using the kneading material of the present invention and the case of using the conventional method is obvious, and the kneading material of the present invention is made of quick lime having a melting point higher than that of iron. It is clear that the hatching is accelerated, the LF refining time is shortened, and the refining efficiency is increased.

By the addition of the present product, the present product embraces quick lime added at the same time, and hatching proceeds, the hatching speed of (mass% CaO) in the slag is fast, and the (% CaO) content is saturated early. The characteristic result of reaching the state is obtained. At this time, fluorite, which is a typical flux for high melting point quicklime, is not added at all.
On the other hand, in the case of adding quicklime powder alone according to the conventional method, it takes time to hatch CaO, and the time until it contributes to molten steel refining is also long.

The high hatchability of the product of the present invention shown in this example confirms the effects of the embodiments (1) to (4) of the present invention, and “calcium aluminate having a low melting point mineral composition in the smelted slag. This shows the effect of being able to achieve early generation of "". This is also verified from X-ray diffraction analysis.
This means that the product of the present invention is extremely effective in the case of a furnace bottomed steel type electric furnace that refuses harmful oxidation defects in refining refining or the secondary refining method that measures converter steelmaking and slag renewal. A method will be provided.

In addition, it is necessary to reduce the value of slag treatment after refining (mass% F) from the viewpoint of environmental pollution because of social responsibility. The following numerical values are values obtained by measuring the residual (mass% F) concentration in the slag by the analytical method defined in JIS for two specimens for the case of general fluorite flux and for the case of the invention. Is a comparison.
Residual (% F) value in slag
For quicklime + fluorite slag: 0.37% by mass ・ 0.31% by mass
For quicklime + product of the present invention: 0.008% by mass / 0.15% by mass
The amount of calcium fluoride added in the former case was 0.8 to 1.0 Kg / molten steel Ton, which was a low addition level. Of course, in the case of the product of the present invention which is a comparative example, the addition of calcium fluoride forms the smelting and refining without adding any calcium fluoride.
Incidentally, it is stipulated that the value should not exceed a value of 0.4% on a soil content basis.
The product of the present invention is released from the use of fluorite flux, which has been universalized in the steelmaking process, and can contribute to the so-called fluorite-less operation, that is, the refining operation that does not contain fluorine.

[Example 3]
In this example, the agglomerated / molded body produced in Example 1 was added to the steel bottom in a furnace bottom steel arc electric furnace and used for the practice of molten steel refining, and its desulfurization performance was confirmed. Moreover, the superiority was confirmed in comparison with refining in normal operation.

First, test conditions and evaluation methods will be described below.
<Test conditions and evaluation methods>
(1) Raw material blending ratio, raw material size, production method of the slag material of the present invention provided for implementation Except that the raw material blending ratio was 50% by mass for quick lime and 50% by mass for aluminum ash, In the same manner as in Example 1, an aggregated / molded product was obtained.

(2) Conditions for steelmaking used for ironmaking and molten steel refining The same as in Example 2.
(3) Outline of the steelmaking process used for ironmaking and molten steel refining Figure 7 shows the outline of the steelmaking process used for ironmaking and molten steel refining and the addition position of the steelmaking material used for molten steel refining. FIG. 7A shows the method of the present invention, and FIG. 7B shows the conventional method.
The melting and oxidation refining in the arc electric furnace was produced in the same way as the normal refining process. At the time of steel production, the addition of iron alloy and quicklime was a predetermined amount based on the work standards. In this example, a predetermined amount of quicklime and the product of the present invention were added simultaneously. After steelmaking, additional quicklime was added to improve desulfurization refining and inclusion refining at the LF refining furnace position.

(4) Evaluation of “S-distribution coefficient” It is defined by the following formula (1) as a means of grasping the speed of refining and the refining status of molten steel by adding quick lime added at the time of steel production or the present invention and quick lime. The “S-distribution coefficient” was used to compare the effects.
S-distribution coefficient = (mass% S) in slag / [mass% S] in molten steel (1)
The S-distribution coefficient was calculated by taking slag samples and molten steel samples at regular time intervals and using the analysis values obtained by the above analysis method.

<Evaluation results>
FIG. 8 shows the elapsed time after adding quick lime or the present invention and quick lime at the time of steel in the furnace on the horizontal axis, and the “S-distribution coefficient” on the vertical axis. Is a plot of the relationship between the elapsed time from the addition of S and the S-partition coefficient.
The vertical axis is “zero” for each value of (mass% S) in the slag and [mass% S] in the molten steel immediately before the addition of quick lime or the present invention and quick lime, The S-distribution coefficient at that time is set to “0” for convenience. The numbers in parentheses on the horizontal axis indicate the elapsed time from the start of LF refining.

  The graph of ● shows the case by the method of the present invention, and the graph of ○ shows the case by the conventional method. From the results shown in FIG. 8, the difference in the effect of molten steel refining (desulfurization of S) accompanying the difference in hatchability is obvious between the case of using the steelmaking material of the present invention and the case of using the conventional method.

The addition of the present invention along with the furnace bottom steel embraces simultaneously added quick lime, hatching progresses, the speed of increase in the molten steel refining (desulfurization S refining) capacity in the slag is fast, conventional quick lime + Characteristic results with a big difference between the fluorite forging and the next process of molten steel refining.
At this time, no addition of fluorite, which is a flux material for melting high melting point quicklime, is performed. On the other hand, in the case of “quick lime + fluorite addition” from the conventional method, which is a comparison test, it takes time to hatch quick lime as a result, and an increase in the S-partition coefficient, which is a guideline for refining, that is, de-S refining The time difference until the time is about 3 to 4 times as long as that of the product of the present invention, and FIG. 8 shows that the time until contributing to molten steel refining becomes longer.
The increase of the S-partition coefficient, that is, the desulfurization of S, cannot be achieved without hatching of quicklime, which is the desulfurization material. The increase in the (CaO) activity in the slag increases with the dissolution of quicklime in the existing slag, and it is theoretically widely known that the above-described de-S refining progresses.

  The high hatchability of the product of the present invention shown in this Example confirms the effects of the embodiments (1) to (4) of the present invention, and the low melting point mineral composition “calcium aluminate” is contained in the smelted slag. This shows the effect of being able to generate early. This is also verified from X-ray diffraction analysis. This means that in the case of an electric furnace with a bottom bottom steel type that refuses oxidizers harmful to reductive refining, or a secondary refining method that measures converter steelmaking and slag renewal, the present product is a very effective steelmaking method. Is to provide.

  In this example, the molten steel was discharged from the melting and refining furnace in a slag-free state and transferred to a steel receiving ladle. At this time, ironmaking is measured by the effect of the product of the present invention utilizing the powerful stirring energy of the molten steel, and the so-called smelting smelting smelting continuity is confirmed by the shift to molten steel refining. It was done. In the case of general furnace bottom steel-type electric furnace operation or converter operation, the steel-making material and the alloyed iron with a predetermined amount of quick lime as the main raw material are put into the receiving steel ladle at the time of steel extraction. Addition measures molten steel deoxidation and ironmaking. However, quick lime having a high melting point does not lead to hatching within a limited time, and actually covers the molten steel in the form of solid quick lime. This is also evident from the measurement of the S-partition coefficient.

  Since the product of the present invention enables “development smelting and refining”, it leads to a reduction in the burden of LF refining in the next process, and the arc heating mode, which is the basis of LF refining, is stable from the initial stage of operation. Form "can be taken. This compensates for the refractory unit performance, which is the weakness of the most excellent LF refining furnace for obtaining high-grade molten steel, and provides a way to cut costs.

[Example 4]
In Example 1, a koji material was produced in the same procedure as in Example 1 except that the raw material composition was 40% by mass of quick lime particles, 30% by mass of aluminum ash particles, and 30% by mass of magnesia particles. The physical properties of the molded molding material thus obtained were measured by the same method as in Example 1. The obtained results were: Volume: 7 CC, Bulk density: 2.0 g / cc, Breaking strength: 35 Kg.
Next, the obtained slagging material was used together with quick lime as a smelting / smelting material for the LF smelting furnace.
The mode in that case was the addition of the product of the present invention according to the addition position of the koji making material indicated in Example 2. (% MgO) in the slag at the end of refining in the conventional method was in the range of 6-8%, but by adding the slagging material of the present invention together with quicklime, the (% MgO) was reduced to 12-14%. Rose. Moreover, the hatching state after addition of the LF refining furnace also completed early slagging as in Example 2 and contributed to refining.
And it was confirmed from the molten steel composition analysis that this (% MgO) tempered slag does not act as an inhibiting factor on the desulfurization refining ability which is the main purpose of the product of the present invention. Although the ladle erosion performance must wait for a long term and the result of the comparison test, the life extension is sure to be high because a high value of 12 to 14% was stably obtained for the (% MgO) content.

As is apparent from the comparison of the hatching rate between the product of the present invention and the conventional product shown in Example 2 (see FIG. 6), the koji material of the present invention has a slow desulfurization reaction rate and a long desulfurization reaction time. It solves all the disadvantages, the disadvantage that desulfurization materials are unevenly distributed, the disadvantage of complicated operation and management of refining materials, and the disadvantage of operability that satisfies environmental waste disposal standards. The effect of being able to produce quality steel was achieved.
Therefore, the ironmaking material of the present invention can be suitably used in the fields of hot metal, molten steel desulfurization and inclusion refining. In particular, desulfurization refining and inclusion refining have been highly evaluated by refining employing a gas stirring method, and is particularly useful for the most widely spread LF refining furnace as out-of-furnace refining.

It is a X-ray-diffraction analysis chart figure of the ironmaking raw material CaO of this invention. It is a X-ray-diffraction analysis chart figure of the ironmaking raw material aluminum ash of this invention. FIG. 3 is an X-ray diffraction analysis chart diagram after heating at 1350 ° C. for a mixed aggregate of the raw material CaO and aluminum ash of the present invention. It is a figure which shows the cut | disconnected cross section of this invention product and an aggregate ironmaking material. In Example 2, it is a figure which shows the outline | summary of the steelmaking process used for the steelmaking and molten steel refining, and the addition position of the steelmaking material used for molten steel refining. It is a comparison figure of the hatching speed (increase amount of% CaO value) of the product of the present invention in Example 2. In Example 3, it is a figure which shows the outline | summary of the steelmaking process used for the steelmaking and molten steel refining, and the addition position of the steelmaking material used for molten steel refining. It is a comparison figure of the desulfurization refining ability (increase amount of S-distribution) of the product of the present invention in Example 3.

Explanation of symbols

1 Quicklime 2 Aluminum ash

Claims (4)

The X-ray intensity position 2θ (X-ray intensity position 2θ (°) is 40 to 70% by mass of quick lime particles having 31.7 to 32.7 °, 36.9 to 37.9 °, and 53.4 to 54.4 °. °) is 32.8~33.8 °, 34.7~35.7 °, volume 1-20 obtained by pressure molding and 30-60 wt% aluminum ash particles of from 38.1 to 39.1 ° Ri Do of aggregates with a rounded cc, said mean particle size of the quick lime particles are 75Myuemu～3mm, said average particle size of the aluminum ash a 75Myuemu～2mm, average particle size of the aluminum ash particles the smaller than the average particle size of the quick lime particles covers the aluminum ash particles quicklime particle surface, molten iron Zokasuzai breaking strength of the agglomerates is characterized 30~50Kg der Rukoto. The X-ray intensity position 2θ is 20-50% by mass of quicklime particles having an X-ray intensity position 2θ (°) of 31.7 to 32.7 °, 36.9 to 37.9 °, and 53.4 to 54.4 °. 20 ° to 60% by mass of aluminum ash particles having (°) of 32.8 to 33.8 °, 34.7 to 35.7 °, and 38.1 to 39.1 °, and an X-ray intensity position 2θ (°) and 20 to 50 wt% magnesia particles 42.4～43.4,61.8～62.8 Ri Do from one aggregate rounded of pressure molding and volume 1 comprising 20 cc, of the quick lime particles The average particle size is 75 μm to 3 mm, the average particle size of the aluminum ash is 75 μm to 2 mm, the average particle size of the aluminum ash particles is smaller than the average particle size of the quicklime particles, and the aluminum ash particles covers the quicklime particles surface, molten iron Zokasuzai breaking strength of the agglomerates is characterized 30~50Kg der Rukoto. The molten iron making material according to claim 1 or 2 , wherein aluminum ash particles are embedded in the surface of the quicklime particles.   The molten iron forging material according to any one of claims 1 to 3 is charged into molten iron or molten steel containing sulfur in an out-of-core smelting furnace or a secondary smelting furnace in a hot metal or steel refining process. How to use molten iron making material.

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