SU910793A1 - Method for extrafurnace treatment of steel and martin furnace - Google Patents

Description

(54) STEEL TREATMENT AND MARTENOV FURNACE

The invention relates to the metallurgy of carbon and alloyed steels and can be used. at the enterprises having open-hearth furnaces. Methods are known for desulfurization of open-hearth steel, including loading lumpy lime into a ladle before pouring metal into it or blowing various kinds of mixture with reagents and melt. The disadvantages of these methods are the low degree of dasulfurization using solid lump lime due to the low degree of its dissolution (melting) in the ladle when pouring the metal, as well as the need to prepare fine powdered mixtures and reagents, reducing or neutral gas - carrier and devices for spinning the metal. This is a drive .t to the great complexity of production, increased, its cost of steel, moreover, these methods are not always effective. Known devices of the rear wall of the open-hearth furnace, including steel outlet and slag-holes. However, this mutual arrangement of the slag and steel outlet in the rear wall of the furnace is known, with which the final slag from the open-hearth furnace can be delivered to the steel-teeming ladle before the metal is released and the steel is desulfurized. The closest to the proposed method is the desulfurization of open-hearth steel, which means that in the smelting unit, steel is smelted under the basic ferrous slag containing by the end of the smelting at least kQ% iron oxides with a basicity of more than 4; The furnace slag at the end of smelting is released into the ladle, and then the unoxidized low carbon metal is then drained. When metal and slag are mixed during metal discharge, the content of sulfur and other elements in the metal decreases. Then the metal in the ladle is blown under a layer of ferrous slag with gases (for example, inert oxygen, gaseous gas or mixtures). When this occurs, the content of sulfur and other impurities in the metal is further 1 J. However, the processing of low-carbon unoxidized (containing a lot of oxygen) metal in the ladle with high iron slags (containing more than 40% iron oxides) is accompanied by a slight desulfurization: 1; In addition, the method is characterized by a weak degree of steel desulfurization with additional blowing of the metal with gases in the ladle under strongly oxidized ferrous slag and difficulties with falling into the specified chemical composition of the steel: increased wear of the lining of the ladle upon contact with the ferrous; slags; the need to have additional equipment; the complexity of the whole processing cycle and a significant increase in the cost of steel; lack of guidance on how and the open-hearth furnace can be first released

in the ladle slag, and then the metal.

All this leads to a slight degree of desulfurization, the impossibility of using the method in the manufacture of steels with high carbon contents, the need to use complex additional equipment during blowing, reduced durability of buckets and increased consumption of refractories, and an increase in the cost of steel.

Closest to the proposed technical essence and the achieved results is a device including an average charging port, through which the primary slag is removed from the furnace into the slag bowl. Liquid steel is discharged from the furnace through a steel outlet through the chute into the casting ladle. Through the same hole and chute after the release of the metal in the casting ladle the final slag converges.

Large open-hearth furnaces operating by the scrap ore process (in addition) in the rear wall have one or two slag holes and

The goal is achieved by releasing the final furnace slag through an additional inclined opening in the furnace rear wall 0.05–15 bath depth below the level of working window thresholds along the additional slag transport chute into the steel-teeming ladle, by deoxidizing the slag in the chute during its production with coke powders, silico-calcium and aluminum followed by discharge into the same metal bucket containing 0.6-1.5 carbon at a temperature of 1580-1650 C,

It is advisable powders of coke, silicocalcium and aluminum prisazivat respectively in quantities of 0.1-, 1-3 and 0, 5-2.0 kg per 1 ton of liquid steel.

Claims (3)

Moreover, the amount of powdered deoxidizing agents that are sown depends on the carbon content in the metal. With a lower carbon content in the metal, the deoxidizing agents sit down at the upper recommended limits, and when the carbon content in the metal at the upper limit is used, the deoxidizing agents sit down at the lower limit of their specific slag chutes, as well as slag buckets, installed on the stands in the casting span. The excess (primary) slag is removed from these furnaces not only through the threshold of the middle batch window, but also through the slag holes along the slag chutes in the slag ladles. Iidka steel and the final slag in large-capacity furnaces are produced in the same way as in furnaces of medium and large capacity f 2 J. However, the slab holes and troughs of heavy-load open-hearth furnaces are intended only for removing primary slag contaminated with verdict impurities. The final slag can be released from the furnace only after the metal has been discharged through a steel outlet and a chute intended for metal release, which excludes the possibility of preparing the final slag for desulfurization of the metal to the ladle. The purpose of the invention is to create cost-effective, easy-to-implement methods and devices for desulfurization of open-hearth steel, ensuring deep desulfurization, removal of other harmful impurities, and increasing the productivity of main open-hearth furnaces by reducing the duration of the desulfurization period in the furnace. moves. After the slag is released and deoxidized, a metal is produced in the ladle with a carbon content in the range of 0.61.5% at a temperature of 1580–150 °, and the higher the carbon content of the metal, the lower its temperature at the outlet and vice versa. , FIG. 1 shows a open-hearth furnace, a cross section through the outlet openings for slag and metal; in fig. 2 - the rear wall of the Mar-ten furnace with a steel casting ladle, top view. During the cold repair of an open-hearth furnace in its back wall 1 to the right or to the left (depending on local conditions) from the steel outlet hole 2 and chute 3 through which metal C is released into the ladle 5, an additional inclined hole 6 is made to release the final slag 7 and the inclined chute 8 for transportation of slag to the steel-teeming ladle 5 Example 1. When the carbon content in the metal before the release of smelting is 0.6-0.9, the slag is deoxidized by the coke powders Z-kg / t, silica silicate 3 kg / t and aluminum 2 kg / t , while the metal from the furnace release s at. Example. 2. When carbon content in metal is 0, 2%, slag is deoxidized with coke powders 1-2 kg / t, silicocalcium 2 kg / t and aluminum 1.5 kg / t, while the metal is released from the furnace at 1-101-1 ° 3 WITH. - Example 3. When the carbon content in the metal is 1, 21-1, 5, the slag is deoxidized with coke powders of 0.10, 9 kg / t, silicocalcium .1 kg / t, and aluminum 0,, 0 kg / t, while the metal It is released from the furnace at 1580-1600 C. The recommended deoxidation, depending on the carbon content before melting, ensures a low and almost equal content of iron oxides in the slag 1.5 to 2.0, which leads to stable and deep desulfurization of the open-hearth steel, as well as the removal of other harmful impurities. The recommended temperature of the metal before the release of smelting, depending on the carbon content, ensures the normal mode of steel casting. As a result, in the bucket, the metal is processed by its own donkey, the refining capacity of which is significantly increased due to deoxidation. After appropriate holding of the metal in the ladle, it is poured into molds or poured into another furnace by known methods. The proposed method can be used both for processing intermediate produced in the main open-hearth furnace for overflowing into an acidic open-hearth furnace, and independently for producing medium and high carbon and alloyed steels in the main open-hearth furnaces of medium and small capacity. The expected technical and economic effect that can be obtained by using the invention will be expressed in obtaining acidic and basic carbon, high carbon and alloyed steels with low sulfur contents of 0.005-0, and other harmful impurities, while reducing the duration of smelting by about 1H20%. These steels will provide high-quality ingots and blanks of the required mass. Claim 1. An after-treatment process for steel, which includes metal treatment with its own furnace slag, characterized in that, in order to carry out deep desulfurization, remove other harmful impurities and reduce the duration of smelting, the Izmarten furnace firstly releases the final slag into the ladle powders of coke, silicocalcium, and aluminum, and then in the same ladle the metal is released at a carbon content of 0.6-1.5% and a temperature of 15801650 С. 2. Method pop.1, which is also distinguished by the fact that coke, silicocalcium and aluminum powders are seated, respectively, in quantities of 0.1-41-3 and 0.5-2.0 kg per ton of liquid steel. 3. A open-hearth furnace containing a back wall with a steel outlet and a chute for metal discharge, characterized in that, in order to carry out desulfurization, remove other harmful impurities and reduce melting, an additional wall was made in the back wall of the furnace. There are holes for discharging the final slag, the inlet part of which is located below the urdvi of the working window thresholds at the lower level of the slag, and an additional chute is installed at the outlet of the hole to drain the final slag into the steel teeming ladle. Sources of information taken into account during the examination 1. USSR Author's Certificate No., кп. C 21 S B / og, 1969. 2o Steel Metals. Ed. V.I. Yvoisky, M., Metallurgists, 1973, G. 606. / Lz