RU2176275C1 - Method of preparing metallized iron-carbon material for smelting cast iron and melting steel - Google Patents

Abstract

FIELD: metallurgical industry, more particularly preparation of charge materials for smelting cast iron and melting steel. SUBSTANCE: method comprises using iron oxides, carbon and binder, pressing thereof in the form of briquettes and metallizing in carbon oxide atmosphere. Metallizing of briquettes is carried out in sealed space heated at 1000-1200 C. Binder is mixture of calcined soda with loam. Briquettes comprise, wt %: binder, 3-7; mixture of iron oxide and carbon oxide, above 100. Invention makes it possible to prepare metallized iron-carbon material, containing 12-13 % of carbon not exposed to secondary oxidation and sintering during prolonged storage. EFFECT: more efficient preparation method. 1 dwg, 1 tbl

Description

 The invention relates to metallurgical production, namely to the preparation of charge materials for smelting cast iron and steel.

 A known method of producing iron-carbon metallized materials in the form of pellets intended for steel and cast iron [1, p. 20-28, 51, 83-86].

 The essence of the known process is to restore iron from its oxides contained in the "raw" pellet. The reducing agent is the gaseous atmosphere obtained by various methods of natural gas conversion. Technological processes of metallization are carried out by heating and aging "raw" pellets in a converted gas environment.

The disadvantages of the method:
- converted gas, in addition to reducing components (CO, H ₂ ), in a significant amount contains CO ₂ , N ₂ , CH ₄ and H ₂ O, which reduces the reducing ability of the gas;
- a narrow range of possible carbon content (0.07 ... 2.2%) in the metallized material, which requires additional carburization of the melt when smelting cast iron in electric furnaces using pellets.

 A known method of metallization of ore pellets with a combined recovery process [2, p. 62-70]. In this method, solid carbon is introduced as part of the "raw" pellets (internal reducing agent) and mixed with pellets (external reducing agent), after which the layer of pellets together with carbon passes through the conveyor through a chamber heated by the nozzles from the inside with the formation of an oxidizing atmosphere, and metallized.

 The disadvantage of this known method is that it does not provide the maximum use of the potential of the internal reducing agent due to its significant waste and carbon production in metallized pellets of more than 1.9%, as demonstrated by the data given in table. 1.

 A common drawback of metallization methods is the high interconnected porosity of metallized pellets, leading to their secondary oxidation and sintering during long-term storage and transportation.

 The objective of the invention is the creation of a method for producing iron-carbonized metallized material in the form of briquettes for smelting cast iron and steel containing over 12% carbon and not subject to secondary oxidation and sintering during long-term storage and transportation.

 The technical result of the invention is the production of iron-carbon metallized material in the form of briquettes for smelting cast iron and steel, containing 12-23% carbon and not subject to internal oxidation and sintering during long-term storage.

The specified technical result is achieved by the fact that the material in the form of briquettes, compressed from a powder mixture, wt.%, Iron oxides 70 - 80, carbon 30 - 20, a binder 3 - 7 in excess of 100% of the mixture, is metallized in a sealed space without access to an oxidizing atmosphere from the outside by heating to a temperature of 1000 - 1200 ^o C.

 Enriched iron ore, steel oxide are used as oxides, coal, coke, and electrode waste are used as carbon. The binder includes a ground concentrate of a mixture of soda ash with loam in a ratio of 1: 6. The binder prevents the formation of interconnected pores, which is achieved by the formation of thin glassy films in metallized briquettes during heating, which impede the penetration of air into the interior and secondary oxidation.

 When briquettes are heated inside them in a wide temperature range, solid carbon gasification reaction takes place with the generation of carbon monoxide CO, which interacts with metal oxides and together with solid carbon reduces iron. Excess CO is released into the sealed heating chamber, creating a reducing atmosphere inside it. After the gasification, reduction, and carburization of the reduced metal are completed, solid carbon residues are located in the closed pores of the sponge iron.

 The content of oxides in the initial briquette of less than 70% leads to a decrease in the amount of reduced iron and density of the finished material, and more than 80% leads to a decrease in residual carbon.

 The inclusion of a binder in the composition of the briquette over 7% is limited by the amount of slag formed during melting.

 Modeling according to the scheme for the industrial production of metallized iron-carbon material is shown in the drawing, where: 1 - a heating furnace, 2 - a briquette, 3 - a cap (alundum) from refractory material, 4 - a shutter (sand), 5 - a steel plate.

 Example. In the experiments used materials: steel oxide containing, by weight. %: iron (total) 73.3; phosphorus 0.008; sulfur 0.009; electrode battle; a binder is a mixture of soda ash and loam in a ratio of 1: 6.

Dross and electrode battle were crushed to a fraction of 0.1 - 0.2 mm, a binder to a fraction of 0.01 - 0.05 mm. The components were mixed in certain proportions, moistened, pressed. Dried briquettes 2 with a diameter of 50 mm and a mass of 106 g were placed in a heating furnace 1 on a plate 5 under a hood 3 sealed with a shutter 4, metallized at a temperature of 1100 ^o C for 1.5 hours

 The experimental results are given in table. 2.

The degree of metallization is 100%. The moisture absorption of metallized briquettes is in the range of 0.2 - 0.4%, which indicates the absence of communicating pores. Metallized briquettes are not susceptible to secondary oxidation, loaded in bulk do not bake after being held in an oxidizing atmosphere at 500 ^° C for 24 hours and do not ignite spontaneously.

 At the same time as metallization, the atmosphere in the metallization chamber was examined under cap 3. For this purpose, a layer of crushed scale 6 weighing 10 g was placed under briquette 2 (see drawing). After the metallization process was completed, it was found that the scale was reduced to iron weighing 7.2 g. This indicates the presence of a reducing atmosphere under the hood.

Sources of information
1. Gimmelfarb A.I., Nemenov A.I., Tarasov B.E., Metallization and electric melting of iron ore raw materials. -M: Metallurgy, 1981, -152 p.

 2. Kudryavtsev B.C., Pchelkin S.A. Pellet metallization. - M: Metallurgy, 1974, - 136 p.

Claims (2)

1. A method of producing a metallized iron-carbon material for smelting cast iron and steel, comprising the use of iron oxides, carbon and a binder as components and their metallization in a carbon monoxide atmosphere, characterized in that the iron oxides, carbon and binder are pressed in the form of briquettes, briquetting is carried out metallization in a sealed space by heating at a temperature of 1000-1200 ^o With, and as a binder use a mixture of soda ash with loam. 2. The method according to claim 1, characterized in that the briquettes contain, wt.%:
Iron oxide - 70-80
Carbon - 30-20
3. The method according to claim 1, characterized in that the briquettes contain, wt.%: A binder of 3-7% in excess of 100% of a mixture of iron oxide and carbon.

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