JPH05171243A - Production of high alloy steel - Google Patents

Abstract

PURPOSE:To effectively utilize the retention heat in a molten iron ladle and to produce a high alloy steel in good thermal efficiency by charging alloy raw material into the empty high temp. molten iron ladle and preheating at the time of producing the high alloy steel by shifting the high alloy molten iron in the molten iron ladle into a converter and executing decarbon-refining. CONSTITUTION:The high alloy molten iron 5 as raw material for the high alloy steel is charged into the top-bottom combined blowing converter 2 and Fe-Si 8 as heat source is charged and oxygen is blown from a top-blowing lance 9, and by oxidizing Si in the Fe-Si, exothermic reaction is executed and the molten iron temp. is raised, and while stirring the molten iron by blowing gas 12 of Ar, etc., from a tuyere at the bottom, the decarbon-refining is executed by the oxygen blowing from the top-blowing lance 9, to produce the high alloy steel 11. The alloy raw material 3 of high carbon Fe-Mn, etc., is charged into the empty molten iron ladle 1, in which the high alloy molten iron 5 has been charged, and after preheating the alloy raw material by the retaining heat, the molten iron 4 is charged and the alloy raw material is melted to make the high alloy molten iron 5, and thereafter, pre- refining for desulfurization, dephosphorization, etc., is executed and the slag is removed and the low S and low P high alloy molten iron 5 is charged into the converter 2 to execute decarbon-refining. By effectively utilizing the retention heat in the molten iron ladle, the high alloy steel can be produced in good thermal efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high alloy steel containing a large amount of alloy components such as manganese, chromium and nickel by using a converter.

[0002]

2. Description of the Related Art As a conventional melting method of high alloy steel using a converter, there is a melting method of high manganese steel described in Japanese Patent Publication No. 61-38248. In this method, molten iron is charged into a vertical blowing converter with tuyere at the bottom, low carbon steel is first melted by top blowing, and high carbon ferromanganese is added to this to obtain molten steel with a predetermined manganese content. After that, decarburization refining is performed by using oxygen blowing from a top blowing lance and supplying an inert gas from the tuyere at the bottom of the furnace together. Therefore, the melting of low carbon steel and the decarburization refining after addition of high carbon ferromanganese can be carried out in the same furnace.

[0003]

However, in the above prior art, the addition amount of high carbon ferromanganese, which is an alloy raw material, to the molten steel is large, and the temperature drop of the molten steel due to this melting is large. Therefore, in order to compensate for the amount of heat required for melting the high carbon ferromanganese, there is a problem that the molten steel temperature must be increased before adding it, that is, at the time of blowing the low carbon steel.

In order to cope with the temperature drop of the molten steel as described above, at present, when charging the alloy raw material, ferrosilicon is added as a heating agent. It is an object of the present invention to provide a melting method for high alloy steel, which can reduce the amount of the above-mentioned heating agent added.

[0005]

In order to achieve the above object, in the present invention, the molten iron is charged into a converter and the alloy raw material is put into an empty molten metal container so that the heat held by the molten metal container is used. After heating, the molten iron is charged into this molten metal container to melt the alloy raw material. Then, after performing hot metal pretreatment such as desulfurization treatment or dephosphorization treatment on the hot metal in which the alloy raw material is stored in the molten metal container, it is charged into a converter and blown with oxygen.

[0006]

The hot metal tapped from the blast furnace is put in a hot metal pot such as a hot metal ladle or a tope car, is subjected to hot metal pretreatment such as desulfurization and dephosphorization, and is then charged into a converter to be blown with oxygen. The molten metal container charged with the molten iron into the converter and emptied receives the molten iron from the blast furnace again, and is circulated and used in the above order. In the process of circulating and using this molten metal container, the molten metal container charged with the molten iron into the converter is empty,
Heat is dissipated until the next pig iron, and its temperature decreases with the passage of time.

Therefore, in the present invention, firstly, it is intended to store the heat retained in the molten metal container to recover the heat and to suppress the heat dissipation of the molten metal container. In particular,
When alloy raw materials such as ferromanganese, ferrochrome, ferro-nickel, and metallic nickel are placed in an empty high-temperature molten metal container, the alloy raw material is heated by the heat held in the molten metal container. Therefore, a part of the heat held in the molten metal container is stored in the charged alloy raw material.

The temperature of the heat-stored alloy raw material lowers with the temperature drop of the molten metal container with the lapse of time, but the temperature is still high when the next hot metal is received. When the hot metal is received in the molten metal container containing the alloy raw material heated to this high temperature, the alloy raw material is at a high temperature and is easily melted together with the stirring of the hot metal at the time of receiving. Also, if you put the alloy raw material in the empty molten metal container, the inner surface of the molten metal container will be covered with the alloy raw material,
Until the temperature of the molten metal container and the temperature of the alloy raw material are about the same,
Heat dissipation from the molten metal container is suppressed.

FIG. 2 is a diagram showing a heat storage effect and a heat release suppressing effect by preliminarily charging the alloy raw material into an empty molten metal container. This figure shows that hot metal of 1500 ℃ is received in the hot metal ladle,
This shows the effect when the received amount is 200 t and 20 t of ferromanganese is charged as the alloy raw material. In FIG. 2, the curve (2) shows the temperature drop condition of the hot metal when only the hot metal is charged into the hot metal ladle and left as it is, and the curve (2) is according to the method of the present invention and is an empty molten metal container. Fig. 3 shows the state of decrease in hot metal temperature when the alloy raw material is put in and heated and the hot metal is received on it. And
The curve of is obtained by calculation of the drop state of the hot metal temperature when the alloy raw material is charged after the hot metal is received.

From the results shown in FIG. 2, the temperatures after 5 hours are compared for the cases of and. First, based on the case of receiving only hot metal, the hot metal temperature in the case of the present invention is lower than that in the case of only receiving hot metal. However, the temperature difference from this is Δ
T ₁ is about 60 ° C. (the temperature is about 1400 ° C., the temperature is about 1340 ° C.), while the temperature difference ΔT ₂ is about 120 when the alloy raw material is charged after the hot metal is received. C. (the temperature is about 1400.degree. C., the temperature is about 1280.degree. C.). As described above, when the alloy raw material is charged before the hot metal is received in the hot metal ladle, the heat accumulation and the suppression of heat release can greatly reduce the temperature drop of the hot metal.

[0011]

EXAMPLE FIG. 1 is an explanatory view of a method for producing a high alloy steel according to an example of the present invention. In FIG. 1, a hot metal ladle is used as a molten metal container for containing and transporting the hot metal, and the circulating use state of this hot metal ladle is shown. In the figure, white arrows indicate the order of using the hot metal ladle, 1 is a hot metal ladle which is a molten metal container, and 2 is a converter.

The hot metal ladle 1 (the hot metal ladle on the right side in the lower row in the figure) that has been emptied by charging the hot metal into the converter 2 is still in a high temperature state.
Into this empty hot metal ladle 1, alloy raw materials 3 such as ferromanganese, ferrochrome, ferronickel, metallic nickel, etc. are charged within a short time after the completion of the hot metal charging.
The alloy raw material 3 in the hot metal ladle 1 is heated (in other words, the heat retained in the hot metal ladle 1 is stored in the alloy raw material 3). After a certain period of time, the hot metal 4 is received from the blast furnace.
As a result, the alloy raw material 3 is dissolved in the hot metal 4.

Next, hot metal pretreatment agent 6 such as quick lime or mill scale is blown into hot metal 5 in which the alloy raw material is melted to desulfurize or dephosphorize. After the pretreatment is completed, the slag 7 is discharged, and the molten pig iron 5 in which the alloy raw material is melted is charged into the converter 2.
The molten metal container 1 charged with the hot metal 5 and emptied is circulated and used in the above order. In the converter 2, after a small amount of ferrosilicon 8 is added as a heat source, oxygen 10 is blown from an upper blowing oxygen lance 9 to perform refining. The molten steel 11 is agitated by an agitating gas 12 such as argon, nitrogen or carbon dioxide gas blown from the tuyere at the bottom of the converter.

(Example 1) After the hot metal was discharged into the converter, 3
20 t of metallic nickel was put into the hot metal pan after 0 minutes. At this time, the temperature of the bottom inner wall of the hot metal ladle was 800 ° C. About 2 hours after charging the metallic nickel, 200 t of hot metal at 1550 ° C was received from the blast furnace in the hot metal pan to dissolve the metallic nickel. The temperature of the hot metal in which metallic nickel was dissolved was 1500 ° C. In the hot metal ladle containing this hot metal, quicklime, mill scale powder, etc. were blown to perform dephosphorization treatment. Then, the pretreated hot metal was charged into a converter. The temperature of this hot metal was 1200 ° C. Then, 600 kg of ferrosilicon, which is a heating agent, was added and oxygen blowing was performed for 20 minutes. The basic unit of ferrosilicon at this time was 2 kg per molten steel t.

(Comparative Example) About 2 after hot metal was discharged into the converter.
The temperature at the bottom inner wall of the hot metal ladle after 700 hours was 700 ° C. 200 tons of hot metal at 1550 ° C. was received from the blast furnace into the hot metal ladle, and quick lime, mill scale powder, etc. were blown into the hot metal ladle containing the hot metal to perform dephosphorization treatment. Then, the pretreated hot metal was charged into a converter. The temperature of this hot metal is 12
It was 00 ° C. Then, 2700 kg of metallic nickel and 1200 kg of ferrosilicon were added and oxygen blowing was performed for 25 minutes. The basic unit of ferrosilicon at this time is molten steel t
It was 4 kg per unit.

Comparing the results of the above example and the comparative example, the example shows that the unit of ferrosilicon is reduced to about 1/2 and the oxygen blowing time in the converter is 5 in comparison with the comparative example. It was shortened by a minute.

[0017]

Industrial Applicability According to the present invention, an alloy raw material is put in a molten metal container which is emptied by charging the molten iron into a converter and heated by the heat held in the molten metal container, and then the molten pig iron is charged to supply the alloy raw material. This is a method in which the hot metal obtained by melting and melting this alloy raw material is subjected to hot metal pretreatment such as desulfurization treatment and dephosphorization treatment, and then charged into a converter and blown with oxygen.

According to the present invention, the heat retained in the high-heat molten metal container can be stored in the alloy raw material to recover the heat.
The basic unit of ferrosilicon added to the converter as a heating agent is reduced, and the alloy raw material is melted in advance, so that the blowing time of the converter is shortened.

[Brief description of drawings]

FIG. 1 is an explanatory view of a method for producing a high alloy steel according to an embodiment of the present invention.

FIG. 2 is a diagram showing a heat storage effect and a heat release suppressing effect by previously charging an alloy raw material into an empty molten metal container.

[Explanation of symbols]

 1 Hot metal ladle 2 Converter 3 Alloy raw material 4 Hot metal 5 received from blast furnace 5 Hot metal melted alloy raw material 6 Hot metal pretreatment agent 7 Slag 8 Ferrosilicon 9 Top blowing oxygen lance 10 Oxygen 11 Molten steel 12 Stirring gas

Claims (1)

[Claims] 1. The molten iron is charged into a converter and the alloy raw material is put into an empty molten metal container and heated by the heat held in the molten metal container. Then, the molten pig iron is charged into the molten metal container to obtain the alloy raw material. After performing hot metal pretreatment such as desulfurization treatment and dephosphorization treatment on the hot metal obtained by melting and melting the alloy raw material contained in the molten metal container, it is charged into a converter and blown with oxygen. Melting method for alloy steel.