Refine method of hot metal

Abstract

When manufacturing molten steel from hot metal using a two base converter-type refining furnace and using one as a hot metal pretreatment refining furnace and the other as a hot metal decarburization refining furnace, the molten slag generated in the decarburization refining furnace is used while still hot as a refining agent in the pretreatment refining furnace without compromising the productivities of the two refining furnaces. A refining method for manufacturing molten steel from hot metal using a converter-type refining furnace with at least two bases and using one as a hot metal pretreatment refining furnace (14) and using the other as a decarburization refining furnace (3) for the hot metal (2) pretreated in the pretreatment refining furnace. After the molten steel (5) obtained by decarburization refining in the decarburization refining furnace has been tapped in a ladle (7), the slag (9) remaining inside the decarburization refining furnace is allowed to flow down, still in the molten state, from above stacked iron scraps to solidify at least a portion of the slag. Then in pretreatment of hot metal in the pretreatment refining furnace, the slag, at least a portion of which has been solidified, is used together with the iron scraps while still hot.

Description

technical field [0001] The present invention relates to a method for refining molten iron, which uses at least two sets of converter-type refining furnaces, one of which is used as a hot metal pretreatment furnace for molten iron, and the other is used as a hot metal pretreatment furnace for pretreatment The final decarburization refining furnace of molten iron is used to smelt molten steel from molten iron. In detail, it relates to a refining method using slag generated in a decarburization refining furnace in a high-temperature state as a refining agent for a preliminary treatment refining furnace. Background technique [0002] Technological development to meet the demands for higher quality and lower prices of various steel materials is carried out in each process of the iron and steel manufacturing process. In the refining process of smelting molten steel from molten iron, the impurity components transferred / separated from the molten metal phase to the slag phase by ref...

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Problems solved by technology

[0012] That is, in Patent Document 1, since the slag remaining in the decarburization refining furnace is temporarily recovered and used after crushing, the heat possessed by the slag is not recovered.

In addition, when the slag is discharged from the decarburization refining furnace, the molten steel remaining in the decarburization refining furnace is discharged out of the refining process system together with the slag and processed, so it becomes a factor of deterioration of the molten steel yield

[0013] In Patent Document 2, it is necessary to arrange the molten iron holding container for storing the molten iron directly below the decarburization refining furnace in the vertical direction, which may not be possible due to the height restriction directly below the furnace.

In addition, even if it can be implemented, because the molten iron holding container is arranged directly under the decarburization refining furnace, or the molten iron holding container after receiving the slag is moved to the dephosphorization refining furnace, the molten iron is kept from the molten iron. The container is loaded into the dephosphorization refining furnace, etc., so the molten iron holding container is frequently and cumbersomely moved, which is easy to cause time loss, resulting in a decrease in production volume and a decrease in the temperature of the molten iron

In addition, if the slag discharged to the molten iron holding container and the undeoxidized molten steel are involved in the molten iron, there is a danger of sudden CO gas generation and bumping, which also poses a safety problem.

[0014] In Patent Document 3, the process from dephosphorization of molten iron to decarburization and refining is carried out continuously in one converter type refining furnace. Although the heat dissipation accompanying the liquid discharge can be prevented, the residence time in the converter type refining furnace becomes longer. Reduced productivity of converter-type refining furnaces

In addition, although the dephosphorization treatment can be carried out in the low-temperature temperature range with a small load on the refractory material of the furnace body, since the dephosphorization treatment to the decarburization refining is carried out sequentially, the refractory material of the furnace body cannot withstand the high temperature state of 1650°C or higher. In the case of decarburization and refining, it is necessary to change the refractory material of the furnace body, and there is a problem that the cost of refractory material increases

In addition, in order to solidify the decarburized slag in the molten state, a large amount of iron oxide is added, so that the reduction of the iron oxide requires heat, so excessive heat loss increases, and the loss of the furnace body refractory due to the added iron oxide increases. this question

And, even if the slag is discharged after the dephosphorization treatment, there is a problem that a part of the slag containing about 2% by mass of phosphorus generated during the dephosphorization treatment remains in the furnace, and rephosphorization (rephosphorization) occurs in the subsequent decarburization refining. : Phosphorus in the slag is transferred to molten iron or steel to increase the concentration of phosphorus in molten iron or steel)

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