JP2711779B2 - Treatment method of reducing slag in arc furnace refining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for converting slag generated in a steel refining process using an arc furnace and a ladle refining furnace, in particular, reducing slag into slag having no weathering collapse property.

[0002]

2. Description of the Related Art A method for melting and refining steel in an electric arc furnace is as follows.
Recently, only scrap melting and oxidizing refining are performed in an arc furnace, and reduction refining is performed by taking a ladle refining furnace (a ladle is brought under a lid equipped with a heating electrode,
Let the smelting furnace function. Hereinafter, the case where they are integrated is called a refining furnace, and the case where they are not integrated is simply called a ladle. The separation and refining method carried out in ()) is becoming mainstream. Among them, the conventional method for treating slag is as follows. Oxidizing slag for oxidizing and refining is made in an arc furnace, and after oxidizing and refining, slag is separated and transferred to a slag pot and molten steel to a ladle. In the ladle refining furnace, a new slag-making agent is put into the molten steel surface, an electrode is inserted into the slag-making agent, and a latent arc is melted and heated. After the reduction smelting is completed, the ladle is moved below the vacuum degassing device, and through vacuum degassing smelting (there may be no such case, but the presence or absence thereof is not particularly relevant to the present invention). Or, it is transferred from the nozzle at the bottom of the ladle to the steel ingot mold. After the molten steel is discharged, the reduced slag remaining in the ladle and the remaining hot water (the slag is mixed when trying to discharge all of them, so some must be left) are transferred to the slag pan. The remaining hot water and slag are separated and transferred or separated after simultaneous transfer. During or after the transfer of the reducing slag to the slag pot, a reforming treatment for eliminating the collapse / expansion property of the reducing slag is performed by mixing some additives.

[0003]

As described above, the reforming treatment of reducing slag has conventionally been carried out after most of the slag has been transferred to a slag pot. In this case, the temperature of the slag may have dropped considerably, the reactivity was poor, and the reforming often lacked homogeneity. Even when oxidizing slag from an arc furnace is used as a modifying agent, the temperature does not always drop and mix well due to the problem of slag timing and the time and labor required for transportation. The extra work increased processing costs.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and the gist of the invention is that an amount of oxidizing slag corresponding to the amount of reducing slag generated per heat is previously supplied from an arc furnace to a ladle. The molten slag and the remaining molten steel remaining after tapping of the ladle of the preceding heat are transferred onto this at the same time as the molten steel is transferred to the slag pot, and then the mixed slag is transferred to the slag pot Things.

[0005]

[Action] Since the hot oxidizing slag is mixed with the reducing slag of the preceding heat on the high-temperature molten steel immediately after the transfer from the arc furnace to the ladle, the temperature of the reducing slag of the preceding heat is reduced. Even if the temperature is lowered, a sufficient reaction temperature can be obtained. When mixing and stirring transfer the reducing slag to the ladle,
This is performed twice when the mixed slag is transferred to the slag pan, and the mixing and reaction are sufficiently performed. Since oxidizing slag is used as a modifier, there is no cost for the modifier. In the operation, only one step of tilting and transferring the mixed slag from the ladle to the slag pan is added, and the processing cost is hardly required. In the method of the present invention, all the residual molten steel that has always been generated in the ladle is returned to the subsequent heat, so that the molten steel yield is increased and the cost for the residual molten steel treatment is no longer required.

[0006]

EXAMPLE An example in which low alloy steel is melted in a 100 ton arc furnace will be described. After finishing the oxidizing refining, the molten steel is transferred to ladle A from the arc furnace. At this time, the oxidizing slag is left in the furnace without discharging about 5 tons, and the slag is simultaneously transferred. Almost before and after this, Ladle B, two heats ahead
Then the transfer to the tundish is over. Ladle B has about 4 tons of reduced slag and about 1 ton of residual molten steel. This is taken over ladle A, and a total of about 5 tons of the total content is transferred to ladle A. The transfer time is about 3 minutes. Immediately after the completion of the transfer, the ladle A is tilted to transfer the entire amount of the slag to the slag pot. The slag in the slag pot is processed normally in the slag processing plant and used as roadbed material. Table 1 shows an example of the composition and temperature of both slags and the mixed slag at this time.

[0007]

[Table 1]

[0008] The disintegration and expansion of slag are mainly Ca
Depending on the O / SiO ₂ ratio and the presence or absence of an oxygen source such as MnO or P ₂ O _5, as shown in Table 1, the mixed slag is
In general, the composition is sufficient to be recognized for high-quality roadbed materials, and can be put to practical use as roadbed materials.

[0009]

According to the present invention, the reducing slag generated in the steel making method using the arc furnace and the ladle refining furnace can be reformed very effectively at almost no cost. No residual hot water was generated in the ladle, and the yield of molten steel was improved, which played a major role in streamlining the reduction slag treatment process.

Claims (1)

(57) [Claims] In a method of melting and refining steel in which melting and oxidizing refining are performed in an arc furnace and reduction refining is performed in a ladle, a predetermined amount of molten steel after oxidation refining is transferred from the arc furnace to the ladle. Transfer the oxidized slag at the same time as the oxidized slag, and further transfer the reduced slag and remaining hot water remaining after tapping from the ladle of the preceding heat, and then immediately transfer this mixed slag to the slag pot A method for treating reducing slag in arc furnace refining.