RU2164960C1 - Method of modifying agent production - Google Patents

Abstract

FIELD: metallurgy, particularly, production of complex deoxidizer-modifier for improvement of steel and iron quality. SUBSTANCE: method includes additional introduction into charge of lime and simultaneously of aluminum in amounts of 20-50 and 10-30% of charge weight, respectively; holding of melt in deenergized furnace and alloy tapping at temperature of 1300-1450 C, and slag tapping after its repeated heating to temperature no more 1500 C. In so doing, prior to slag tapping, flux may be charged into furnace. Flux is used in the form of fluorspar and/or broken soda-ash glass in amount of 1-3% of charge weight. Reduction is carried out, mainly, with aluminum. EFFECT: produced modifying agent containing rare-earth and alkali-earth metals, high yield of product with relatively low power consumption. 3 cl, 1 tbl

Description

 The invention relates to the field of metallurgy, and in particular to the production of complex deoxidizing modifiers to improve the quality of steel and cast iron.

 The proposed method can be used in metallurgical and engineering plants to obtain modifiers and their processing of steel and cast iron.

 A known method of producing a modifier containing rare earth and alkaline earth metals, includes the melting of the mixture, consisting of screening of calcined dolomite, oxides or fluorides of rare earth metals and ferrosilicon [1].

 In accordance with this method, the reduction of metals is carried out by silicon ferrosilicon. The disadvantage of this method is the relatively low (20-22%) metal recovery.

Closest to the invention in technical essence and the achieved effect is a method for producing a modifier containing rare earth and alkaline earth metals, including the melting of the mixture, metal recovery, the addition of aluminum waste at 1300-1400 ^o C and the release of the resulting alloy and slag [2].

In accordance with the specified method, the reduction of metals is carried out mainly by silicon ferrosilicon, and the temperature of the alloy and slag during release are respectively 1600-1660 ^o C and 1510-1570 ^o C.

The disadvantage of this method is the relatively high temperature of the alloy and slag during release. This leads to large losses of reduced metals, in particular magnesium and calcium, by evaporation due to their low boiling point, respectively 1090 ^o C and 1484 ^o C. This drawback is exacerbated by the simultaneous release of alloy and slag having a close density and, therefore, adverse conditions their separation during solidification.

The objective of the proposed method is the creation of an energy and resource-saving method for producing a modifier that provides high yield for a product with a relatively low power consumption. The technical result is achieved by the fact that in the method of producing a modifier containing rare earth and alkaline earth metals, including the melting of the mixture, consisting of screening the calcined dolomite, oxides or fluorides of rare earth metals and ferrosilicon, metal recovery and the release of the obtained alloy and slag, according to the invention, to the charge additionally lime and aluminum are simultaneously introduced in an amount of 20-50% and 10-30%, respectively, of the charge mass, the melt is kept in a disconnected furnace and at 1300-1450 ^o C the alloy is released, and the slag is released after it is reheated to a temperature of no more than 1500 ^o C. In this case, flux, which is used as fluorspar and / or sodium glass fight, can be loaded into the furnace before the slag is released, in an amount of 1-3% of the mass of the charge, and the recovery is carried out mainly by aluminum.

 If the upper limit of the amount of lime in the charge is exceeded (more than 50%), the charge penetration rate decreases due to the high melting point of the highly basic slag, which will reduce the furnace productivity.

 A decrease in the amount of lime in the mixture below the lower limit (less than 20%) will increase the viscosity of the slag due to the relatively high content of magnesium oxide in it, a decrease in the calcium content in the alloy and a deterioration in the quality of the modifier.

 An increase in the amount of aluminum in the charge of more than 30% will increase the viscosity of the slag, worsen the conditions for the separation of alloy and slag, and reduce the yield of the alloy.

A decrease in the amount of aluminum in the charge of less than 10% will lead to the predominant reduction of metals by silicon ferrosilicon and the formation of refractory slag of the CaO-SiO _{2 system} , a decrease in furnace productivity and an increase in energy consumption. In addition, a decrease in the amount of aluminum in the charge of less than 10% will lead to a decrease in the aluminum content in the alloy and an increase in the melting temperature of the alloy, i.e. to the deterioration of its consumer properties.

The increase in the temperature of the melt in the furnace before the release of the alloy more than 1450 ^o C will lead to partial or complete discharge of the slag together with the alloy, their mixing and reduce the yield of the alloy.

The lower limit of the temperature of the melt in the furnace (1300 ^o C) before the release of the alloy is due to the fact that a further decrease in temperature will lead to incomplete drainage of the alloy from the furnace due to the fact that its crystallization temperature is 1000-1200 ^o C and at a temperature of less than 1300 ^o C its viscosity.

An increase in the temperature of the slag over 1500 ^o C is impractical, since the predominant reduction of metals by aluminum and the additional introduction of lime into the mixture makes it possible to obtain low-melting slag of the CaO-Al ₂ O _{3 system} , the melting point of which is approximately equal to 1600 ^o with an equal content of CaO and Al ₂ O ₃ in it C. In addition, at temperatures above 1500 ^o C, lime interacts with the carbon of the graphite crucible with the formation of calcium carbide, which will lead to a decrease in the calcium content in the alloy and a decrease in the stability of the crucible.

 The loading of flux into the furnace before slag discharge reduces the melting point of the slag, which will speed up the preparation of slag for release and increase the productivity of the furnace.

 An increase in the amount of flux more than 3% of the mass of the charge will increase its cost and worsen working conditions of workers due to the intensification of dust and gas emissions.

 The lower limit of the amount of flux (1%) is due to the fact that with a further decrease in the amount of flux, the slag viscosity will increase. This will lead to reduced furnace performance and increased energy consumption.

 The proposed method for producing the modifier includes loading into the furnace a mixture consisting of screening the calcined dolomite, oxides or fluorides of rare-earth metals, ferrosilicon, lime and aluminum, its melting, metal recovery mainly with aluminum, holding the melt in a disconnected furnace, releasing the alloy, re-heating the slag and its release.

The method according to the invention is as follows. The mixture is loaded into a graphite crucible heated to 1500 ^° C, filling the entire internal volume of the crucible. After the charge is melted and the melt is formed, the melt is held at the furnace power off, lowering its temperature to 1300-1450 ^o C. This will increase the viscosity of the slag, which will allow the alloy to be drained from the crucible, and the slag left in the crucible. The slag remaining in the crucible is heated to 1500 ^° C. without loading or with flux loading and the slag is drained.

In contrast to the known method, in which the reduction of metals is carried out mainly by silicon ferrosilicon, aluminum is added to the furnace after the charge is melted at 1300-1400 ^o C and the alloy is released from the furnace at 1600-1660 ^o C simultaneously with slag, in the proposed method, the mixture is additionally administered simultaneously and lime aluminum, which allows the recovery of metals preferably aluminum alloy to reduce the outlet temperature to 1300-1450 ^o C, and slag - no more than 1500 ^o C. The relatively low temperature of the alloy and slag When separate release and release sharply reduce loss of the active metal alloy by evaporation and oxidation by atmospheric oxygen and also because a better separation of the slag and the alloy at issue.

 Example. To conduct comparative tests of the known and proposed methods, the melting time and yield of the suitable modifier were evaluated. The modifier was melted in a graphite crucible of the IST-0.05 induction furnace according to the known and proposed methods. The test results are shown in the table.

 From the table it follows that upon receipt of the modifier by the proposed method, the melting time decreases by 25-42%, and the yield of the product increases by 2-7% compared with the known method.

 These features of the proposed method provide energy savings and charge materials, a high yield of the product and its higher quality in comparison with the known method.

Sources of information
1. USSR author's certificate N 461964, cl. C 22 C 33/00, 1975.

 2. Copyright certificate of the USSR N 949011, cl. C 22 C 33/04, 1982.

Claims (3)

1. A method of obtaining a modifier containing rare earth and alkaline earth metals, including loading into the furnace and melting the mixture, consisting of screening the calcined dolomite, oxides or fluorides of rare earth metals, ferrosilicon, metal recovery and the release of the alloy and slag from the furnace, characterized in that lime and aluminum are additionally introduced into the charge at the same time in an amount of 20-50% and 10-30%, respectively, of the charge, the melt is kept in a disconnected furnace and at 1300-1450 ^o C the alloy is released and the slag is released they are cooled after it is reheated to a temperature of no more than 1500 ^o C.  2. The method according to claim 1, characterized in that the recovery is carried out mainly by aluminum.  3. The method according to claim 1, characterized in that before the release of slag in the furnace load flux, which is used fluorspar and / or the battle of sodium glass, in an amount of 1 to 3% by weight of the charge.

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