JPH0411603B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a steel manufacturing method in which a large amount of solid iron-containing cold material such as cold pig iron or scrap is melted and then oxygen-blown in a converter. be.

(Prior art) In general converter refining, hot metal supplied from a blast furnace is used as the main raw material, a relatively small amount of scrap is added to it, and a sizing agent and a high flow rate of oxygen are supplied to produce oxygen. It is common to perform blowing. In this conventional method, the amount of scrap in the total raw material charge is at most 35% due to restrictions due to the heat source, and it cannot be said that this method allows for the use of a large amount of scrap.

Regarding this point, conventionally, as a steelmaking method in which a large amount of iron-containing cold material, mostly scrap or cold pig iron, is used for refining in a converter, an oxygen top blowing device as proposed in Japanese Patent Publication No. 60-34605 has been proposed. 10 to 30% per heat from scrap using an oxygen top-bottom blowing converter equipped with a carbon material introduction nozzle installed at the bottom of the furnace.
There is a method in which a considerable amount of excess molten steel is refined, and the excess molten steel is left in the furnace as seed water for the next heat, and the scrap is charged and refined in the next heat.

However, this method uses the same converter for melting and refining, and then sequentially uses the remaining molten steel as a seed metal.As a result, the sulfur content in the large amount of coal or coke used is reduced to molten steel. to go into.

There is a wide range of temperature changes from scrap melting to decarburization refining, and the high temperatures during the tapping stage result in a short refractory life.

Since the refining is carried out almost continuously from melting to the end of blowing, it takes a long time, and therefore more pyrolyzed hydrogen from propane, etc. used to protect (cool) the bottom blowing tuyere is absorbed into the molten steel.

It is said that there is a drawback.

In order to solve these drawbacks, Japanese Patent Application Laid-Open No. 1986-
No. 174812 is proposed. This proposed method attempts to eliminate the above drawbacks by performing the process of melting the iron-containing cold material using seed water and the process of refining the melted material in separate converters. Two types of converters are used, and high-carbon molten iron is obtained by supplying iron-containing cold material, carbon material, and oxygen to one converter (converter exclusively for melting) in which seed metal is present, and this molten iron is transferred to another converter. Its basic feature is to obtain molten steel with the required components by oxygen blowing in a furnace (a converter exclusively used for refining). The iron-containing cold material is melted to obtain high-carbon molten iron, the melting converter is overturned, a part of the molten iron is extracted into a ladle, and the rest of the molten iron remains as a seed metal. Ferrous cold material, carbonaceous material, and oxygen are supplied again into the melting converter to melt the iron-containing cold material to obtain high carbon molten iron. By repeating the operation of withdrawing a portion of the iron into the ladle, and finally discharging the entire amount of high-carbon molten iron in the melting converter into a ladle different from the ladle, it is necessary for refining and seeding. of high carbon molten iron.

The high carbon molten iron discharged into the ladle is then charged into a separate converter exclusively for refining, where it is oxygen blown and refined using conventional steelmaking methods to produce molten steel with the desired composition. It is refluxed to the converter exclusively for melting as a seed water at the start of operation.

(Problems to be Solved by the Invention) As described above, the method proposed in JP-A-60-174812 is able to determine the amount of seed metal at the start of operation of the next heat in the converter exclusively for melting and the converter exclusively for refining in the next process. In order to obtain the total amount of high-carbon molten iron required for , and to flow it back to the melting converter and supply it to the refining converter, the melting converter is toppled multiple times (specifically, three times). There is a problem in that it requires additional operations and the dissolution process takes a long time.

Furthermore, when starting the next heat operation, the molten iron temporarily stored in the ladle must be charged into the converter exclusively for melting as seed water, further prolonging the melting process time.

The present invention provides a converter steel manufacturing method that shortens the above-mentioned melting treatment time and improves melting efficiency.

(Means for Solving the Problems) The gist of the present invention is to obtain high carbon molten iron by supplying iron-containing cold material, carbon material, and oxygen to a melting converter in which a seed metal exists, and to use this molten iron as a raw material. In the converter steel manufacturing method in which molten steel with the required composition is obtained by oxygen blowing in a separate converter exclusively for refining, in the converter exclusively for melting, the required refining amount in the converter exclusively for refining and the amount of refining in the converter exclusively for melting are determined. High-carbon molten iron in the total amount of the required amount of seed hot water is obtained, and the required amount of high-carbon molten iron is refined from the melting-only converter to the refining-only converter in one tap for oxygen refining. A converter steel manufacturing method characterized in that the remaining amount of seed water of molten iron is left in a melting-only converter and used as seed water for melting the iron-containing cold material.

The high carbon molten iron in the present invention is molten iron with a carbon content of 2% or more.

According to the method of the present invention, the amount of pre-treated molten iron required for the refining converter can be obtained in one tapping operation, that is, only one overturning operation of the melting converter in which excess melt has been melted,
On the other hand, the remaining amount of seed hot water of the pretreated molten iron is left in the melting-only converter and used as seed hot water for melting the iron-containing cold material, and in the melting process of the method proposed in JP-A-60-174812, 2 required for seed hot water supply
In addition to eliminating the need for multiple collapse operations, it also eliminates the need to charge molten iron from the ladle into the converter dedicated to melting, which is required as a seed metal at the start of the next melting heat, and the melting process time is significantly reduced. The dissolution efficiency is improved.

Further, according to the present invention, a ladle for storing seed hot water is also unnecessary, and the manufacturing cost of high carbon molten iron can be reduced.

Although the invention disclosed in Japanese Patent Publication No. 60-34605 is different from the method of using two types of converters with different functions, which is the object of the present invention, Table 1 of the examples is shown below.
Scrap is placed in an oxygen top-bottom blowing converter in the presence of a seed bath.
The process of supplying carbonaceous materials and oxygen is repeated twice to obtain high carbon molten iron, and the converter is collapsed to discharge a portion of the molten iron into the ladle as seed molten metal for the next heat, and the remainder is poured into a ladle. Scrap, carbonaceous material, and oxygen are newly supplied to the converter where molten iron remains, and the scrap is melted.Then, the scrap is blown into molten steel with the required composition by oxygen blowing, and the entire amount is tapped. A method is disclosed in which molten iron is charged as seed water into a converter after tapping,
In addition to tapping the steel, it is necessary to operate the furnace for tapping the seed hot water.
It is necessary to carry out the overturning operation twice, and the molten iron in the ladle must be charged into the converter at the start of the next heat operation.
Same as No. 17812, scrap melting and refining processing time,
In particular, it has the disadvantage that the dissolution treatment time is long.

Furthermore, according to Example Table 2 of the same publication, a method is shown in which the seed water is left in the furnace, and the number of times the furnace is collapsed is the same as the present invention, but according to Table 2, the seed water is left in the furnace. Since the entire amount including steel is refined into steel, there is a disadvantage that the amount of oxygen used is large and the steel manufacturing cost is high. Therefore, Japanese Patent Publication No. 60-34605 and the present invention are different.

Furthermore, according to JP-A No. 59-23808, it has a process dedicated to melting the seed metal called a repeat cycle, and a process for refining it into molten steel called a production cycle, and the two seed metals obtained by the above repeat cycle and tapped. ,1
It is proposed that one be subjected to the next repeat cycle and the other to the manufacturing cycle. and,
It is shown that the hot water was poured over iron-containing cold materials such as scrap. In contrast, the method of the present invention requires the seed metal to remain in the converter exclusively for melting, does not have the so-called production cycle of refining iron-containing cold material into molten steel all at once, etc.
This is fundamentally different from No. 59-23808.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a process diagram showing the method of the present invention, in which 1 is a converter exclusively for melting, for example, it has an oxygen top blowing lance 2,
A tuyere 3 is provided at the bottom of the furnace so that carbonaceous materials such as coal and coke can be blown in together with a non-oxidizing carrier gas (e.g. nitrogen gas), and oxygen and a non-oxidizing gas for cooling (e.g. LPG) can be blown in. This is an oxygen top-bottom blowing converter. 4 is another converter exclusively for refining, which has, for example, an oxygen top blowing lance 5, and an oxygen top blowing furnace having a tuyere 6 at the bottom of the furnace for blowing an inert gas, such as carbon dioxide, for stirring the molten iron in the furnace; This is an inert gas bottom blowing converter.

As shown in Fig. 1a, scrap 8 is charged into the converter 1 in the presence of a seed bath 7 (a portion of high carbon molten iron in which scrap, which will be described later, has been melted remains in the furnace), and the tuyere Carbon material and oxygen are supplied from lance 3, and oxygen is supplied from lance 2 to carburize and melt the scrap 8.
When the scrap is melted, new scrap is charged into the high carbon molten iron made of the seed metal 7 and the scrap melt, and the same process of carburizing and melting is carried out multiple times, for example twice, and the amount of seed metal is The total amount of high-carbon molten iron, for example, 3.5% carbon content, is obtained in the subsequent refining converter 4 (the state shown in FIG. 1b). Next, as shown in Fig. 1c, the melting converter 1 is operated to collapse to increase the required amount (an amount equivalent to the total amount of scrap charged in multiple times) in the refining converter 4. The carbon molten iron is tapped into the ladle 9, and the remaining amount of the high carbon molten iron is left in the melting converter 1 (the state shown in Figure 1 d), and is used as a seed molten metal for scrap carburization in the next heat. use.

The high carbon molten iron obtained in the ladle 9 is shown in Figure 1 e.
As shown in FIG.
While stirring the molten iron by introducing carbon dioxide gas, oxygen is supplied from the top blowing lance 5 to decarburize the iron and refine it into molten steel with the required composition. Steel will be tapped.

If the sulfur content of the carbon material used in the melting converter 1 is high and the sulfur content of the molten iron discharged into the ladle 9 is high, as shown in Figure 1g, the molten iron in the ladle 9 It is also possible to add a desulfurizing agent to the iron and perform the desulfurization treatment by stirring it with an impeller 11, for example, and then supply the desulfurized molten iron to the converter 4 exclusively for refining.

In addition, as the refining converter 4, an oxygen top-blowing converter,
An oxygen bottom blowing converter, an oxygen top and bottom blowing converter, etc. can be used.

(Example) Seed water amount: 84 tons, required amount for refining converter 4: 116 tons
FIG. 2 shows an example of the operation pattern of the melting converter 1 shown in FIG. 1 when obtaining molten iron with a total amount of 200 tons and a carbon content of 3.5%. For more information, see Carbon Content
29 tons of scrap was charged into the converter 1 in the presence of 84 tons of 3.5% molten iron (scrap charging), coal was supplied from the bottom tuyere 3, oxygen was supplied from the tuyere 3 and lance 2, and the scrap was Carburizing and melting yielded 113 tons of molten iron. Next, 58 tons of scrap was charged into the converter 1 in the presence of 113 tons of molten iron (scrap charging), and in the same manner, coal was supplied from the bottom tuyere 3 and oxygen was supplied from the tuyere 3 and lance 2, and the scrap was was carburized and melted to obtain 171 tons of molten iron. then
Scrap inside converter 1 in the presence of 171 tons of molten iron
29 tons of scrap was charged (scrap charging), and in the same way, coal was supplied from the bottom tuyere 3 and oxygen was supplied from the tuyere 3 and lance 2 to carburize and melt the scrap, resulting in a carbon content of 3.5% and 200 tons. Obtained molten iron. Next, the converter 1 was collapsed and the required amount of 116 tons in the refining converter 4 was tapped into the ladle 9, leaving the remaining seed metal amount of 84 tons in the converter 1 to complete the melting heat cycle. . The dissolution heat cycle time was 66 minutes.

(Conventional example) Under the same scrap charging, oxygen, and carbonaceous material supply conditions as in the above example, the amount of seed metal is 84 tons, and the required amount in the converter 4 for refining is 116 tons.The total amount is 200 tons, and the carbon content is 3.5 tons.
% of molten iron, the furnace was collapsed before the second 58-ton scrap charging in the above example, and a part of the obtained molten iron, that is, 29 tons, was tapped into a ladle for seed storage. However, before the third charge of 29 tons of scrap in the above example, a portion of the molten iron obtained by toppling the furnace was 55
A total of 84 tons of seed hot water was secured in the ladle by tapping the molten iron into the storage ladle, and finally the entire 116 tons of molten iron obtained in the converter 1 was tapped into the ladle, and then transferred to the ladle. 84 tons of molten iron was charged into the furnace 1 from the seed hot water storage ladle to complete the melting heat cycle. The melt heat cycle time is 81 minutes.

(Effects of the Invention) As described in detail above, according to the converter steel manufacturing method of the present invention, the melting efficiency can be improved and the cost of manufacturing molten iron can be reduced.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the steel manufacturing method of the present invention,
FIG. 2 is an explanatory diagram of an embodiment of the method of the present invention. 1... Converter exclusively for melting, 4... Converter exclusively for refining, 7
...Taneyu, 8...Scrap, 9,10...Ladle.

Claims (1)

[Claims] High-carbon molten iron is obtained by supplying iron-containing cold material, carbonaceous material, and oxygen to a melting-only converter containing seed water, and this high-carbon molten iron is used as a raw material for oxygen blowing in another smelting-only converter. In the converter steelmaking method for obtaining molten steel with the required components, in the melting-only converter, high carbon molten iron is obtained in the total amount of the required refining amount in the refining-only converter and the required seed metal amount in the melting-only converter, The required refining amount of high carbon molten iron from the melting converter to the refining converter is provided for oxygen refining in one tap, while the remaining amount of seed metal of the high carbon molten iron is left in the melting converter. A converter steel manufacturing method characterized in that the converter is used as a seed hot water for melting the iron-containing cold material.