JP2968142B2 - How to operate a shared melting and refining furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scrap, ferro-alloys,
The present invention relates to a method of operating a furnace that can share melting and refining in the production of molten steel and alloyed steel from ore and the like.

[0002]

2. Description of the Related Art Melting furnaces and refining furnaces for producing molten steel and alloyed steel can be classified into two types: converters, in which molten iron is used as a main iron source and oxygen blowing is performed, and scrap or alloyed iron is used as a main iron source to perform melting by electric energy. In order to produce an electric furnace and alloy steel such as stainless steel, it is roughly classified into an AOD furnace that blows chromium-containing crude molten steel melted in an electric furnace with oxygen and argon.

The criteria for selecting these processes include the price and availability of iron and alloy sources, the price and availability of energy required to obtain molten steel and alloy steel, and the quality of steel. The required components of molten steel and alloyed molten steel are the main ones. For example, in an integrated steel mill with blast furnace equipment, it is most economical to use hot metal as an iron source.In this case, refining in a converter using oxygen gas and adding various types of alloy iron etc. Steel grade can be manufactured.

[0004] On the other hand, in an ironworks having an electric furnace, scrap and ferromagnetic iron are used as an iron source and an alloy source, and are directly heated and melted by electric energy. At this time, an operation method in which electric energy is supplemented using a small amount of carbon material and oxygen gas is generally used. Generally, after treating the obtained molten steel outside the furnace, various kinds of steel types can be produced by adding alloyed iron or the like.

[0005] In each of the above-described processes, usable iron sources, alloy sources, and energies are almost fixed, and significant changes are not possible. For example, in the converter process, the use of scrap and ferro-alloy cold iron sources is equivalent to 20% of all iron sources.
% Or less, and the external energy is mostly oxygen gas.

On the other hand, in the electric furnace process, almost all of the iron source and the alloy source are cold iron sources such as scrap and ferromagnetic iron,
There is no equipment structure that can use a large amount of hot metal. Most of the energy that can be used is electric energy, and is combustion heat obtained by burning carbonaceous material with oxygen gas in a complementary manner. Furthermore, an electric furnace is generally a furnace that only performs melting, and after tapping, it is necessary to perform a refining process using an AOD furnace or vacuum processing equipment. By the way,
The price and availability of alloy sources and energy, etc., fluctuate with time. For this reason, it is required to select the most economical iron source and energy according to the fluctuation of the price of raw materials and energy.

An example in which the range of use of the iron source and the energy source is expanded and a flexible steelmaking furnace is proposed is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-47417. Is a method of melting and refining with the use of coal or coke and oxygen gas as energy sources, as disclosed in JP-A-59-215427. A method in which the part is replaced by heating with a pulverized coal combustion burner, as disclosed in Japanese Patent Application Laid-Open No. 63-100119, the scrap charged in the furnace is bored and melted by a DC arc electrode, and then the electrode is extracted. There is a method in which an oxygen lance is inserted into a boring hole to dissolve the scrap.

Further, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-235209, the furnace body is divided into upper and lower parts, the upper part is detachable, and the upper part is supplied with an electric furnace part having electrodes and oxygen gas. There is a method in which a converter part having a lance is replaced as needed to melt hot metal, scrap, and iron ore as an iron source. However, the above-mentioned prior art has the following disadvantages and problems. In the method disclosed in Japanese Patent Application Laid-Open No. Sho 62-47417, it is difficult to completely burn coal or coke in a converter with oxygen gas and to completely utilize the combustion heat. In addition, there is a limit to the heat that can be generated within a unit time in a converter, and depending on the conditions, it is possible to use only combustion heat even in a situation where it is economical to use electric energy directly. It is not economical because it cannot be done.

Next, the methods disclosed in JP-A-59-215427 and JP-A-63-100119 are based on utilizing scrap as an iron source. This method is not economical under conditions where the use of ore is generally less expensive.
Furthermore, the method according to Japanese Patent Application Laid-Open No. 4-235209
The electric furnace is divided into upper and lower parts in order to select and use electric energy and combustion energy. Therefore, the furnace body becomes complicated, the furnace body is difficult to manage, and it takes a long time to attach and detach the upper part of the furnace body. There is a problem that requires.

As described above, most of the conventional techniques cannot cope with large fluctuations in the prices of raw materials and energy, so that the most economical melting method, raw materials and energy cannot be selected. Or, there was a problem in operation management due to the complicated furnace structure.

[0011]

Accordingly, an object of the present invention is to change the price of raw materials such as molten iron, scrap, ferro-alloy and ore as an iron source, the price fluctuation of electricity, oxygen, carbon materials and the like as energy, it is intended to economically advantageous proposed operations method of melting and refining shared furnace which can respond according to the variation factors, such as steel in the component required for quality.

[0012]

According to the method of operating a shared melting and refining furnace of the present invention , a tuyere and a lower electrode are provided at a lower portion of a furnace body, a hood is provided above the furnace body, and the furnace body is passed through the hood. In a melting and refining shared furnace provided with an upper electrode and a lance inserted therein, after charging a cold iron source to the shared melting and refining furnace, the cold iron source is melted by a DC arc by the upper electrode and the lower electrode. After melting, refining is performed by supplying a refining gas from the lance and the tuyere.

[0013]

Operation method of melting and refining sharing furnace of the effects of the present invention, it is possible to operate the furnace body as an electric furnace and a converter, if
In the production of gold and stainless steel, the cold iron source is
After unraveling, refining of molten steel can be performed in the same furnace .

[0014]

EXAMPLES operations method of melting and refining sharing furnace of the present invention
An example of an apparatus for performing this will be described with reference to a longitudinal sectional view shown in FIG. 1 and a plan view shown in FIG. The furnace body 1 has a zirconia-based, chamotte-based or high-alumina-based perm brick 3 installed inside a steel shell 2, and a magcro-based lining brick 4 installed inside the perm brick 3. Furnace body 1
Above the hood, a hood 5 for exhausting or collecting dust is provided so as to be able to move up and down by a driving mechanism (not shown). ing. The lance 6 and the upper electrode 7
The pole 1 is supported via the support 12 and the swing arm 13 respectively.
4, the turning arm 13 moves up and down along the pole 14 and turns around the pole 14.

The right and left sides of the furnace body 1 are tiltably supported by trunnion shafts 9 and 9. The furnace body 1 is tilted about the trunnion shafts 9 and 9 by a drive mechanism (not shown), and the furnace body 1 And hot metal charging and tapping are possible. In the lower part of the furnace body 1, tuyere 10 for refining gas supply,
For example, a plurality (4 to 8) of the lines connecting the trunnion shafts 9 and 9 are provided on one side, and the tuyere 10 and the lance 6 can blow up and blow down.
Further, a lower electrode 11 made of graphite is provided on the bottom wall 1B of the furnace body 1, and direct current arc heating is possible with the upper electrode 7.

The upper electrode 7 and the lower electrode 11 are
Considering the capacity of the lining brick 4 and the refractory of the lining brick 4, two or three lining bricks may be provided. Further, about 2 to 12 tuyeres 10 may be provided on the bottom 1B of the furnace body in consideration of stirring of molten steel. The hood 5 may be provided with a function of turning or sliding in addition to moving up and down. Further, the lance 6 and the upper electrode 7 may be slid instead of turning.

Further, in the melting method, DC arc heating between the upper electrode 7 and the lower electrode 11 causes less wear of the furnace refractory, facilitates electrode management, and enables stable melting. If there are equipment restrictions such as capacity or the installation position of the furnace body, three upper electrodes 7 may be used, and AC arc heating of only the upper electrodes may be performed.

Next, the dissolution method of the present invention shown in FIGS.
The operation method of the shared refining furnace will be described. The operation method of the present invention is characterized in that it can be used as an electric furnace as shown in FIG. 3A, an upper and lower blown converter as shown in FIG. 3B, or a bottom blown converter as shown in FIG. When used as an electric furnace,
As shown in (A), the upper electrode 7 is inserted into the furnace body 1 through the insertion hole 8 of the hood 5, a direct current arc is generated between the upper electrode 7 and the lower electrode 11, and the inserted scrap, alloy iron, ore, etc. Heat the cold iron source. At this time, the tuyere 1 at the bottom of the furnace body
By supplying oxygen gas from 0, various operations such as increasing the dissolution rate and blowing an inert gas to prevent oxidation of the cold iron source G can be performed. Partial dissolution (generally 70%
Refining is performed after complete dissolution or complete dissolution.

When refining is performed, the upper electrode 7 is lifted up and pulled out of the hood 5, and then swirled and removed as shown in FIG. Next, the lance 6 is swiveled toward the hood and stopped on the insertion hole 8, then lowered and charged into the furnace. Next, as shown in FIG.
As shown in FIG. 3 (C), bottom-blowing converter refining is performed with the insertion hole 8 closed. After the bottom-blowing converter refining, the lance 6 is replaced with the upper electrode 7 when used as an electric furnace.

Next, when used as a converter, FIG.
(B), the oxygen gas or oxygen gas through the lance 6 and tuyere 10 into the furnace body 1 and the other gas (Ar, N
₂ , or a mixed gas of CO ₂ ) or an inert gas such as Ar or N ₂ is blown to perform decarburization and refining of the hot metal and final refining such as reduction and component adjustment after the decarburization refining.

The choice of use as a top-blowing converter or a bottom-blowing converter can be made arbitrarily in consideration of the refining time or the reaction efficiency. It is efficient to use it as a blown converter and then use it as a bottom blown converter. Use from the converter to the electric furnace can be easily performed by replacing the lance 6 with the upper electrode 7 by the reverse operation. At the time of tapping and charging of raw materials, the lance 6 and the upper electrode 7 are raised and then swirled away to raise the hood 5.

[0022] Next, the method of operation melting and refining shared furnace of the present invention
Another apparatus example for performing the above will be described with reference to a longitudinal sectional view shown in FIG. 1 and 2, the hood 5 is provided with a lance insertion hole 16 through which the lance 6 can pass and an electrode insertion hole 15 through which the graphite upper electrode 7 can pass. The lance 6 and the upper electrode 7 are supported on the pole 14 so as to be able to move up and down and pivot similarly to FIGS.

When used as an electric furnace , the upper electrode 7 is inserted into the furnace body 1 through the electrode insertion hole 15 of the hood 5, and a direct current arc is generated between the upper electrode 7 and the lower electrode 11 as described above. The cold iron source G such as the loaded scrap, ferromagnetic iron, ore, etc. is heated and melted. This time lance 6, the tip of La
It is positioned so as to block the Nsu insertion hole 16.

Next, when refining is performed , the upper electrode 7 is raised as shown in FIG. 4 and stopped at a position where the tip thereof closes the electrode insertion hole 15 . Next, the lance 6 is lowered and the furnace body 1
Into the furnace and perform top and bottom blown converter refining or bottom blown converter refining. At the time of tapping and charging of raw materials, the lance 6 and the upper electrode 7 are raised as described above, and then, the lance 6 is retreated and the hood 5 is moved.
To rise.

Next, when used as a converter, the furnace body 1
Blowing oxygen gas or oxygen gas, mixed gas or Ar other gases (Ar, N ₂ or the like, CO _2), an inert gas such as N ₂ through lance 6 and tuyere 10, soluble
Refining similar to that in FIG. 3B or FIG. 3C is performed, such as decarburization and refining of steel , and reduction and component adjustment after decarburization.

[0026] The operation method of melting and refining shared furnace according to the present invention will be described with reference to a specific example. The furnace actually used is a 60-ton scale furnace. The tuyere 10 at the lower part of the furnace body shown in FIG. 1 has a double tube structure, and N ₂ ,
Ar is 200 Nm ³ / Hr, and O ₂ ,
N ₂ and Ar gas of 1000 to 4000 Nm ³ / Hr were blown. Furnace body is adapted to the upper electrode and the lance can be easily replaced, the O ₂ gas from the lance 1000
５5000 Nm ³ / Hr was blown. The power transformer capacity when the upper electrode is inserted is 48 MVA.

[0027] When the cold iron source of scrap and alloy iron melting and refining sharing furnace above began operating with 60t charging is required about 60 minutes to dissolve, then about an upper electrode lance 1 minute blowing was carried out for about 30 minutes by switching in, 5 in one furnace
8 tons of molten stainless steel could be produced.

[0028]

Effects of the Invention For the conventional steelmaking plant has been provided a converter and an electric furnace separately, in the manufacturing such as stainless steel,
The transfer process for transferring the molten steel melted in the electric furnace to the AOD furnace for refining was unnecessary , but according to the present invention,
This eliminates the need for the step of transferring molten steel .

[Brief description of the drawings]

FIG. 1 shows a method for operating a shared melting and refining furnace according to the present invention.
FIG. 2 is a longitudinal sectional view showing an example of an apparatus for performing the above.

FIG. 2 is a plan view of FIG.

FIG. 3 is an explanatory view of an operation method of a shared melting and refining furnace according to the present invention , wherein (A) is an arc melting furnace, (B) is a top-bottom blow refining furnace, and (C) is a bottom blow refining furnace. It is a figure showing the operation state of.

FIG. 4 illustrates a method for operating a shared melting and refining furnace according to the present invention.
FIG. 7 is a longitudinal sectional view showing another example of the apparatus for performing the above.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Furnace body 2 Iron shell 3 Perm brick 4 Lining brick 5 Hood 6 Lance 7 Upper electrode 8 Insertion hole 9 Trunnion shaft 10 Tuyere 11 Lower electrode 12 Support body 13 Rotating arm 14 Pole 15 Electrode insertion hole 16 Lance insertion hole G Cold Iron source

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-235209 (JP, A) JP-B-62-58524 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21C 5/34 C21C 5/52 C22B 7/00 F27B 3/08 F27D 11/10

Claims (1)

(57) [Claims] 1. A tuyere and a lower electrode are provided in a lower part of a furnace body,
A hood is provided above the furnace body, and in the method for operating a shared melting and refining furnace provided with an upper electrode and a lance inserted into the furnace body through the hood, a cold iron source is charged into the shared melting and refining furnace. After that, the cold iron source is melted by a DC arc generated by the upper electrode and the lower electrode, and after melting, refining gas is supplied from the lance and the tuyere to perform refining.