JPH0693324A - Treatment of reducing slag in arc furnace refining - Google Patents

Abstract

PURPOSE:To reform molten reducing slag of high collapsibility by adding molten reducing slag and remained molten steel in a ladle for reducing-refining into the molten steel and molten oxidizing slag after oxidizing-refining in the following heat, at the time of refining the molten steel by the reducing-refining succeeding to the oxidizing-refining by an arc furnace. CONSTITUTION:The molten steel produced by oxidize-decarburizing refining in an arc furnace is shifted in the ladle refining furnace, and after reducing- refining by making new molten reducing slag, if necessary, vacuum-degassing refining is executed and continuous casting or ingot-making is executed. In this case, by mixing the molten reducing slag, in which CaO content remaining in the ladle refining furnace is high and the treatment is inconvenient because of the formation of powder by efflorescence and collapsing after solidification of the molten oxidizing-refining slag from the arc furnace in the following heat into the molten slag ladle, the CaO/SiO2 ratio value in the molten slag is made low and the collapse after solidifying is eliminated and the slag is reformed to the material which can be used to a firm road bed material. Further, the remaining molten steel in the ladle can be used as the molten steel for casting in high yield.

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 disintegration property.

[0002]

2. Description of the Related Art A method for melting and refining steel in an arc furnace is
Recently, only melting and oxidative refining of scrap is performed in an arc furnace, and reduction refining is carried out by ladle refining furnace (take the ladle under the lid equipped with a heating electrode, cover it with the lid, and integrate it.
Let it act as a refining furnace. 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 the main subject. Among them, the conventional method for treating slag is as follows. Oxidizing slag for oxidative refining is made in an arc furnace, and when oxidative refining is completed, slag is separately transferred to a slag pan and molten steel is transferred to a ladle. In the ladle refining furnace, a new slag-forming agent is newly introduced into the molten steel surface, and an electrode is thrust into the slag-forming agent to melt and heat the latent arc to form reducing slag and perform reduction smelting. After the reduction and refining is completed, the ladle is moved to a position below the vacuum degassing device, and is subjected to vacuum degassing and refining (there are some cases where it is not related to the present invention), and the tundish for continuous casting is used. Or, transfer to the steel ingot mold from the nozzle at the bottom of the ladle. After the molten steel is discharged, the reducing slag that remains in the ladle and the residual hot water (the slag will be mixed if you try to discharge all of it, so there is no choice but to leave some), and the mixture is poured into the slag pan. The residual hot water and slag should be separately transferred or separated after simultaneous transfer. During the transfer of reducing slag to the slag pot, or after the transfer, some kind of additive is mixed in to carry out a modification treatment to eliminate the disintegration / expansion property of the reducing slag.

[0003]

As described above, the reforming treatment of the reducing slag has conventionally been carried out after it is mostly transferred to the slag pot. In this case, since the temperature of the slag may be considerably lowered, the reactivity is poor and the reforming homogeneity is often lacking. Even when using an oxidizing slag from an arc furnace as a modifier, the temperature does not always drop well and the reaction does not always occur due to problems with the timing of slag and the time and effort required for transportation. The extra work of the above increased the processing cost.

[0004]

The present invention is intended to solve the above problems, and its gist is to ladle an amount of oxidizing slag that corresponds to the amount of reducing slag generated per heat in advance from an arc furnace. At the same time as the molten steel is transferred to, the reducing slag remaining after the tapping of the preceding heat ladle and the remaining molten steel are all transferred onto it, and then this mixed slag is transferred to the slag pan. It is a thing.

[0005]

[Function] Since the reducing slag of the preceding heat is mixed with the oxidizing slag of sufficiently high temperature on the hot molten steel immediately after being transferred from the arc furnace to the ladle, the temperature of the reducing slag of the preceding heat is Even if the temperature is lowered, a sufficient reaction temperature can be obtained without any problem. When mixing stirs when transferring the reducing slag to the ladle,
This is done twice when transferring the mixed slag to the slag pot, so that the mixing and the reaction are sufficiently performed. Since the oxidizing slag is used as the modifier, there is no cost for the modifier. The work involves only one additional step to transfer the mixed slag from the ladle to the slag pan, and there is almost no process cost. 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 becomes unnecessary.

[0006]

EXAMPLE An example of melting a low alloy steel in a 100 ton arc furnace will be described. After finishing the oxidation refining, molten steel is transferred from the arc furnace to the ladle A. At this time, about 5 tons of oxidizing slag is left in the furnace without being discharged, and this is transferred at the same time. Almost around this, ladle B preceded by 2 heats
Then the transfer to the tundish is over. About 4 tons of reducing slag and about 1 ton of residual molten steel remain in the ladle B. Take the ladle B on the ladle A, and pour the total amount of about 5 tons of the contents into the ladle A. The transfer time is about 3 minutes. Immediately after the transfer is completed, the ladle A is tilted and the entire amount of the slag is transferred to the slag pan. The slag in the slag pot will be treated normally at the slag treatment plant and used as roadbed material. Table 1 shows an example of the composition and temperature of both slags and mixed slag at this time.

[0007]

[Table 1]

[0008] The slag disintegration and expansion are mainly due to 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
The composition is generally sufficient to be recognized as a good quality roadbed material, and can be put to practical use as a roadbed material.

[0009]

By implementing the present invention, the reducing slag generated in the steelmaking method using the arc furnace and the ladle refining furnace can be reformed very effectively with almost no cost. It also played a major role in streamlining the reducing slag treatment process by improving the yield of molten steel by eliminating the generation of residual hot water in the ladle.

Claims (1)

[Claims] 1. A method for melting and refining steel in which melting and oxidation refining are carried out in an arc furnace and reduction refining is carried out in a ladle, wherein a predetermined amount of molten steel after being oxidized and refined is transferred from the arc furnace to the ladle. It is transferred at the same time as the oxidizing slag, and then the reducing slag remaining after tapping and the remaining hot water are transferred from the ladle of the preceding heat, and then this mixed slag is immediately transferred to the slag pan. A method for treating reducing slag in arc furnace refining, which comprises: