KR101099792B1 - Preparation method for calciumferrite flux for steelmaking - Google Patents

Abstract

The present invention is a method for producing a calcium ferrite flux for steelmaking comprising the step of adding a limestone and iron oxide mixed powder to a cement kiln and calcining at 1120 ~ 1280 ℃ and the step of manufacturing the mixed powder as a clinker in the cement kiln. It is about.

Cement kiln, clinker, calcium ferrite, steelmaking, steelmaking

Description

Preparation method of calcium ferrite flux for steelmaking {Preparation method for calciumferrite flux for steelmaking}

The present invention relates to the production of steel and in particular to fluxes for steelmaking.

In steelmaking and steelmaking processes, slag removes impurities from steel, forms a film between molten steel and the atmosphere, reduces heat loss, and prevents refined steel from recombining with O, N, and H in the atmosphere. Role.

Non-metallic inclusions (O, S, P, etc.) contained in steel deteriorate the properties of steel. In particular, oxides and sulfides greatly deteriorate the properties of steel. Therefore, it is essential to remove these impurities in steelmaking processes such as electric furnaces and converters. For this purpose, flux is used. Quicklime (CaO) is most commonly used as a degassing agent to remove impurities due to its excellent thermodynamic dehydration limit and low price, but its high melting point (2,570 ℃) slows down the reaction rate and increases degassing time, slag For fluidity, there are problems such as maintaining the furnace temperature above the melting point of steel (1,400 ° C).

As such, slag originated from quicklime and non-metallic inclusions has a high melting point and high oxidative properties.If the composition is inappropriate, impurities such as O, S, and P melt into the steel again from the slag, and if the melting point is high, the operating time increases due to the high temperature in the furnace. Al, Si, Ti, Mn, V, etc. required for the vortex steel may be excessively eluted with slag.

In addition, the metal Al.substrate on the CaO—SiO 2 —Fe 2 O 3 slag including FeO, SiO 2 and the like. When the slag composition is changed to CaO-Al 2 O 3 -SiO 2 system by adding a suitable solution, there is a limit to the removal of impurities by slag unless a proper floc is added to the top slag to change the composition to an excellent impurity trapping ability. In other words, the top slag has a low melting point, good fluidity, low oxygen potential (Potential) and must satisfy all the conditions of the activity of impurities.

In order to improve slag fluidity and outflow capacity, first, CaF2 is added to top slag. CaF2 reliably improves slag fluidity in a short time, but affects not only the CaO-Al2O3-SiO2 bonds of slag but also the CaO-Al2O3 bonds of the refractory, resulting in refractory loss, HF gas generation and fluorine leaching during slag recycling. Cause the same problem.

The second method is to adjust the composition of the top slag to a region having a low melting point. For this purpose, calcium ferrite (CaO-Fe2O3), calcium aluminate (CaO-Al2O3), and iron oxide bauxite (Fe2O3 having a high content of Al2O3H2O) ) Is used.

In Korean Patent Application No. 1944-29054 (name: converter conversion method using ladle slag as solvent), 275 tons of ladle slag was used as a low melting point (1332 ℃) solvent during blast furnace conversion to replace existing fluorspar. In the Korean Patent Application No. 1996-71444 (name: converter conversion method), manganese ore is almost mixed 1: 1 in the ladle slag (melting point 1320-1335 ℃) and the converter is blown. It is a method to suppress the oxidation loss of manganese in molten iron. However, the above methods are effective at low melting point because the concentration of Al2O3 in ladle slag is 20-50% by weight, but it is more effective than conventional operation by erosion of converter refractory or production of complex compound of Al2O3 and calcium oxide (CaO). The lack of phosphate stabilizing role of calcium oxide implies a high possibility of adversely affecting the delineation reaction. In addition, the use of converter slag as a sintering raw material or continuous recycling to the next charge is applied. I have a problem.

In addition, Korean Patent Application No. 1999-2388 (name: converter solvent and method for refining the converter using the same) relates to a solvent agent that promotes slag goods during the drilling of the converter. In order to ensure that the sintered dust, mill scale and converter sludge are formulated into a briquette by mixing at an appropriate mixing ratio, and then added, the technical point is to promote the recyclability while lowering the melting point of the slag, but this is 50% by weight of the solvent. Since the moisture content of the converter sludge is above 20% by weight, special attention is required because it is highly likely to deteriorate the quality of molten steel due to the increase of hydrogen in the molten iron. In addition, it is possible to solve the drying problem at high temperature in order to solve the above-mentioned hydrogen rise problem, but the workability is poor because there is a risk of fire due to ignition of iron oxide (FeO) during the drying process as well as cost increase.

In addition, Korean Laid-Open Patent Publication No. 2003-0013727 (name: low melting point solvent composition having a slag calming effect and delinquency for refining converter), in order to provide a slag calming effect of limestone with a particle size of 0.1 ~ 1.0 mm and delinquency and low In order to provide a melting point, it is proposed to prepare a low melting point solvent composition having a slag soothing effect and delinquency, which is made of pellets by mixing iron oxide having a particle size of 0.1 to 1.0 mm and having a melting point of 1100 to 1300 ° C. The simple mixing of limestone and iron-containing raw materials has the disadvantage of increasing the reaction time with the slag in the furnace, and it is also uncertain whether a low melting point effect of 1300 ° C. or less can be achieved unlike when limestone and iron-containing raw materials are added.

In addition, there has been an attempt to manufacture a low-cost flux using slag generated in the ladle of the steelmaking process, and in Korea Patent Publication No. 2005-0084699 (name: flux replacement agent composed of mini-mill refined slag), mini mill Although it is proposed a flux substitute composed of mini-mill refined slag that can replace the flux for steelmaking used in conventional electric furnace steelmaking process by recovering the refined slag that is excluded after refining in the refinery during the steelmaking process, but used in the flux substitute The mini-mill refined slag is used to select the refined slag having a particle size of 5 ~ 50mm among the mini-mill refined slag, there was a problem that can not utilize the refined slag of particle size less than 5mm.

It is an object of the present invention to provide a method for preparing calcium ferrite flux for adjusting the chemical composition of top slag to a region having a low melting point in a steelmaking process.

In the manufacturing method of the calcium ferrite flux for steelmaking of the present invention, 1160 by adding a limestone and iron oxide mixed powder to a cement kiln composed of a pre-heater, a rotary kiln and a clinker cooler. It is characterized in that it comprises a step of firing at ~ 1260 ℃ and the mixed powder in the cement kiln into a clinker, and crushing and sorting the clinker to 2 ~ 200mm.

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In the manufacturing method of the calcium ferrite flux for steelmaking of the present invention, the molar ratio of CaO and Fe2O3 of the calcium ferrite flux for steelmaking is 2: 1 to 1: 2.

The present invention omits the process of finely grinding limestone and iron-containing raw materials in the form of agglomerates or agglomerates for the manufacture of calcium ferrite fluxes, and provides a method for producing calcium ferrite fluxes by clinker using a cement kiln to break down existing processes. By shortening it can reduce the manufacturing cost of calcium ferrite flux for steelmaking.

In the manufacturing method of calcium ferrite flux for steelmaking of the present invention, a limestone and iron oxide mixed powder is added to a cement kiln composed of a pre-heater, a rotary kiln, and a clinker cooler. Firing at 1260 ° C. and preparing the mixed powder as a clinker (plastic) in a cement kiln, and crushing and sorting the clinker to 2 to 200 mm.

Since limestone and iron oxide of the present invention is melted together in a cement kiln, the particle size does not need to be particularly limited, but it is preferable to use an average particle size in the range of 0.01 to 1 mm so as to be evenly mixed in a desired ratio. It is preferable to mix, or mix and grind in advance before entering.

Cement kiln of the present invention is a secondary equipment consisting of a conventional rotary kiln (Pre-heater) and a clinker cooler (OPC) for the manufacture of ordinary OPC (Ordinary Portland Cement) If necessary, it is also possible to use an electric furnace such as EAF.

In the manufacturing method of the calcium ferrite flux for steelmaking of the present invention, the melting temperature is 1120 ~ 1280 ℃, preferably 1160 ~ 1260 ℃, more preferably 1200 ~ 1250 ℃. If the melting temperature is less than the lower limit, after the decarbonation is completed, the reaction does not participate and there is a large amount of free CaO remaining to form calcium ferrite. It is difficult to quantitatively input when it is dusted in the steelmaking process, and it is difficult to float on the top slag layer even if it is injected. To this end, that is, the steelmaking calcium ferrite flux of the present invention formed by cooling the clinker so that it can sink when dosed and injected into the top slag layer has a particle size of 2 to 200 mm, preferably 5 to 100 mm, more preferably. It is preferably 20 to 80 mm, and if necessary, may include a process of crushing and screening the clinker to a desired particle size.

In order to adjust the chemical composition of the top slag in the steelmaking process to a region of low melting point, CaO and Fe 2 O 3 should be added appropriately.In the case of adding them separately or in a mixed form, CaO (melting point 2570 ° C.) and Fe 2 O 3 (melting point 1,565 ° C.) High melting point requires much time to change slag composition. In the CaO-Fe2O3-SiO2 slag, the lowest melting point is a calcium ferrite mineral phase (2CaOFe2O3, CaOFe2O3, or CaO2Fe2O3, etc.), as shown in FIG. Therefore, the molar ratio of CaO and Fe 2 O 3 in the calcium ferrite flux of the present invention is preferably 2: 1 to 1: 2.

Hereinafter, the present invention will be described in detail by way of examples. However, the following examples are merely to illustrate the present invention, but the content of the present invention is not limited thereto.

[Example]

Mill scale was used as limestone and iron oxide to prepare calcium ferrite flux. Each particle size was 90% residue 12% average particle size was 50㎛. Table 1 shows the results of component analysis of limestone and mill scale.

division Fe2O3 SiO2 CaO MgO Al2O3 Mill scale 108.42 0.6 0.3 0.01 0.1 Lime lime 0.32 5.62 50.2 1.35 1.62

The prepared limestone and wheat scale were blended in the mixing ratio (%) of Table 2.

division Fe2O3 SiO2 CaO MgO Al2O3 Total Compounding cost Mill scale 108.42 0.6 0.3 0.01 0.1 109.43 37 Lime lime 0.32 5.62 50.2 1.35 1.62 59.11 63 Formulation result 40.32 3.76 31.74 0.85 1.06 77.73 (Mixed powder) 51.87 4.84 40.83 1.10 1.36 100 (Converted value)

The CaO content of the mixed powder was 31.74% and Fe2O3 was 40.32%. SiO2 was 3.76% and Al2O3 was 1.06%. When the result of chemical analysis of the mixed powder was 100 except ignition loss and trace components, the CaO content was 40.83% and Fe2O3 was 51.87%. In addition, SiO2 was 4.84% and Al2O3 was 1.36%. That is, the CaO content of the finally prepared calcium ferrite flux was estimated to be 40.83%, and Fe 2 O 3 was estimated at 51.87%.

Mixed water (mixed water / mixed powder = 20%) was added to the mixed powder and mixed to prepare a molded product of about 30 g. The molded article was dried for 24 hours in a 100 ℃ dryer. The dried molded body was fired in an electric furnace, and the firing conditions were raised to the maximum firing temperature at 10 ° C. per minute and then maintained at the highest firing temperature for 30 minutes. At the highest firing temperature, the fired clinker was immediately unloaded. The firing temperatures were 1100 ° C, 1200 ° C, 1225 ° C, 1250 ° C and 1300 ° C, respectively.

At 1100 ° C. firing conditions, as shown in FIG. 2, it was confirmed that a large amount of free-CaO remaining was not present in the reaction after the decarbonation was completed. However, after 1200 ° C. (FIGS. 3, 4 and 5), only a small amount of free-CaO could be observed, because free-CaO reacted with the Fe2O3 component of mill scale to generate calcium ferrite. In the case of firing at 1225 ° C., agglomerates (average diameter 50 mm) were maintained even after being rolled out with clinker, but in 1300 ° C. firing conditions, firing of clinker as shown in FIG. The phenomenon is observed, which is considered to be due to the expansion of minerals by the decomposition of CaO from calcium ferrite during the cooling process. Also, in the XRD pattern of FIG. 6, relatively higher free-CaO peaks were observed than FIGS. 3, 4, and 5.

In the above embodiment, limestone and mill scale (iron oxide) of the components shown in [Table 1] are based on the example of firing a mixed powder in an electric furnace, as shown in [Table 1] It is well known that the same clinker can be produced when limestone and mill scale (iron oxide) of [] component are loaded into cement kiln at the mixing ratio of [Table 2], and the kiln is operated according to the firing conditions of the example. As in the embodiment, it is a common method widely used to confirm the firing conditions of an electric furnace as the firing conditions of a cement kiln or to manufacture a prototype.

Figure 1 shows a CaO-Fe2O3-SiO2 state diagram.

2 is a graph showing the X-ray diffraction pattern of the fired article 1100 ℃.

3 is a graph showing an X-ray diffraction pattern of a baked product at 1200 ° C.

4 is a graph showing an X-ray diffraction pattern of a fired product fired at 1225 ° C.

5 is a graph showing an X-ray diffractogram pattern of a 1250 ° C rolled fired article.

6 is a graph showing an X-ray diffraction pattern of a fired product 1300 ° C.

7 is a photograph of a 1225 ° C rolled fired article.

8 is a photograph of a 1300 ° C rolled fired article.

Claims (4)

Limestone and iron oxide mixed powder is put into a cement kiln consisting of a pre-heater, rotary kiln and clinker cooler and calcined at 1160 ~ 1260 ℃ and the mixed powder is cement A method of producing calcium ferrite flux for steelmaking, comprising the steps of preparing a clinker in a kiln, and crushing and selecting the clinker to have a thickness of 2 to 200 mm. delete delete The method of claim 1, The molar ratio of CaO and Fe2O3 of the steelmaking calcium ferrite flux is 2: 1 to 1: 2 manufacturing method of calcium ferrite flux for steelmaking.

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