JPH01225715A - Production of high manganese steel - Google Patents

Abstract

PURPOSE:To reduce manganese shifted into slag under oxide state with reducing agent and to effectively make component in molten steel of the manganese by charging pretreated molten iron, adding manganese ore or manganese oxide and the reducing agent into molten iron and blowing. CONSTITUTION:The manganese ore, etc., as manganese source and the reducing agent of ferro-silicon, etc., are added into the pretreating molten iron charged in a converter body 1. Then, a lance 3 is inserted from furnace opening part 2 of the converter body 1 and oxygen gas is blown from tip part of the lance 3 to execute the oxygen blowing. During blowing operation, by blowing argon gas into the converter body 1 from gas blowing holes 4 arranged at the bottom part, molten steel 5 is stirred. In this case, as dephosphorizing agent is not needed, the slag 6 quantity is a little in the body 1 and the manganese quantity shifting from the slag is relatively a little. Therefore, by reducing the manganese content existing as MnO in the slag with the reducing agent, it can be made to the component in the molten steel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing high manganese steel, which manufactures high manganese steel by blowing hot metal in a converter furnace.

[Prior Art] Conventionally, when manufacturing high manganese steel, hot metal is blown in a converter, and after blowing, the molten steel is tapped into a ladle.

Next, the molten steel in the ladle is heated by an electrode with an arc and stirred with argon gas to refine the ladle. At this time, ferromanganese is added to the molten steel in the ladle to make manganese a component of the molten steel. In addition, ferromanganese contains some hydrogen, and this hydrogen causes defects in the steel.
Particularly in the case of thick plates, hydrogen is removed from the molten steel by degassing the molten steel using an RH degassing facility or the like after ladle blowing.

[Problems to be Solved by the Invention] However, when producing high manganese steel in this way, there is a drawback that the number of steps is large and the processing cost becomes extremely high.

This invention was made in view of such circumstances, and
An object of the present invention is to provide a method for manufacturing high manganese steel that can simplify the manufacturing process.

[Means for Solving the Problems] In the method for producing high manganese steel according to the present invention, hot metal that has been pretreated to reduce the phosphorus concentration is charged into a converter, and manganese ore or manganese oxide and manganese ore are added to the hot metal. The method is characterized by adding a reducing agent and performing converter blowing while reducing manganese that has migrated into the slag in the converter and exists in an oxide state with the reducing agent.

In this case, it is preferable to use ferrosilicon or silicon as the reducing agent.

[Operation] In this invention, pretreated hot metal is charged into a converter, and manganese ore or manganese oxide and a reducing agent are added to the hot metal and then blown into the slag in an oxide state. The transferred manganese can be reduced by a reducing agent and can be effectively used as a component in molten steel. In addition, since the phosphorus concentration of the hot metal is low, there is little risk of rephosphorization. In this case, since manganese can be added to the molten steel without using ferroalloy, ladle refining and RH degassing are not necessary. Therefore, the process for manufacturing high manganese steel can be simplified, and processing costs can be reduced.

[Example] Examples of the present invention will be specifically described below.

FIG. 1 is a schematic diagram showing a converter blowing equipment. Reference numeral 1 in the figure is a converter main body, into which pretreated hot metal whose phosphorus concentration has been reduced to about 0.01% is charged. This pre-treated hot metal contains Cab, CaF2
It can be obtained by supplying a dephosphorizing agent such as the above and oxygen into hot metal, causing the phosphorus in the hot metal to migrate into slag in the form of calcium phosphate, and removing this slag. By using such pretreated hot metal, there is no need for a dephosphorizing agent in the converter.

Manganese ore or manganese oxide as a manganese source, and a reducing agent such as ferrosilicon, metallic silicon, or aluminum are added to the pretreated hot metal charged into the converter body 1. Then, a lance 3 is inserted through the furnace port 2 of the converter main body 1, and oxygen gas is blown into the converter from the tip of the lance 3 to perform oxygen blowing. A gas inlet 4 is provided at the bottom of the converter main body 1, and argon gas is blown into the converter main body 1 from this gas inlet 4 during blowing.
Stir the molten w45 inside.

In this case, since a dephosphorizing agent is not required, there is very little slag 6 in the converter main body 1, and relatively little manganese migrates into the slag. However, there is a high concentration of M in the slag.
n O is included, and the P2O5 concentration is significantly lower than in normal blowing. Therefore, the manganese present in the form of M n O in the slag can be reduced by the reducing agent to become a component in the molten steel. Moreover, the amount of rephosphorus during reduction can also be suppressed to a low level.

FIG. 2 is a graph showing the relationship between the processing time on the horizontal axis and the manganese reduction rate on the vertical axis.

In the figure, white circles indicate the case where ferrosilicon is used as the reducing agent, and black circles indicate the case where aluminum is used as the reducing agent.

At this time, the supply amount of bottom-blown argon gas was set to 0.17 Nm/37 minutes per ton of molten steel. As shown in this graph, it was confirmed that a high reduction rate of 80 to 90% could be achieved in about 3 minutes no matter which reducing agent was used.

When ferrosilicon or metallic silicon is used as a reducing agent, the oxygen concentration in the steel can be about 1 to 100 ppm. On the other hand, when aluminum is used as a reducing agent, the oxygen concentration in the steel becomes essentially 0, but this makes it easier for nitrogen contained in the argon gas used as a stirring gas for the molten steel to be picked up in the molten steel. . On the other hand, in the case of the above-mentioned ferrosilicon or metal silicon, molten steel contains a certain amount of oxygen,
Since the nitrogen gas can be maintained in a stable state, nitrogen pickup can be suppressed. Therefore, in the case of steel types where nitrogen pickup has a negative effect on quality, it is preferable to use ferrosilicon or metallic silicon as the reducing agent.

FIG. 3 is a graph showing the relationship between the processing time on the horizontal axis and the nitrogen pick-up amount of molten steel on the vertical axis. In the figure, white circles indicate the case where ferrosilicon is used as the reducing agent, and black circles indicate the case where aluminum is used as the reducing agent. As shown, up to 40 ppm of nitrogen was picked up when aluminum was used, but it was confirmed that it was about 15 ppm when ferrosilicon was used.

After blowing in the converter in this way, the molten steel is poured into a ladle,
This molten steel is made into a product of a desired shape by ingot formation or continuous casting.

In this case, since manganese can be effectively added to the molten steel in the converter in the form of ore or oxide, expensive ferromanganese can be reduced. In addition, since ferromanganese is not used, there is virtually no risk of hydrogen being mixed into the molten steel (therefore, there is no need for vacuum degassing equipment such as RH). Since there is no need to add , ladle refining equipment is not required.

[Effects of the Invention] According to the present invention, manganese can be effectively made into a component in molten steel during converter blowing, so ladle refining can be omitted. Furthermore, since manganese can be added without using ferromanganese, there is no need to remove hydrogen from molten steel, and vacuum degassing such as RH can be omitted. In this way, since ladle refining and vacuum degassing can be omitted, the process can be simplified and the processing cost of molten steel can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a converter for carrying out this invention;
FIG. 2 is a graph showing the manganese reduction rate, and FIG. 3 is a graph showing the nitrogen pick-up amount. 1-Converter body, 2. Furnace mouth, 3: Lance, 4: Gas inlet Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) Hot metal that has been pretreated to reduce the phosphorus concentration is charged into a converter, and manganese ore or manganese oxide and a reducing agent are added to the hot metal, which migrates into the slag in the converter and becomes an oxide. A method for producing high manganese steel, which comprises performing converter blowing while reducing existing manganese with a reducing agent. (2) The method for manufacturing high manganese steel according to claim 1, wherein the reducing agent is ferrosilicon or metal silicon.