JPH08157926A - Decision of carbon quantity at blowing off in converter - Google Patents

Abstract

PURPOSE: To decide the blowing-off carbon quantity to be in the lowest cost in a converter and to obtain a low carbon steel at a low cost by executing operation considering the producing cost in a converter process and a degassing process based on the variation in the conditions of kind of treating steel, its history, etc., in the degassing process. CONSTITUTION: Beforehand, the producing cost of the degassing process which is obtd. from a degassing time and the producing cost of the converter process which is obtd. from the blowing-off carbon quantity in the converter and the blowing time of the converter obtd. from the blowing-off carbon, are obtd. Further, the effects of factors such as the order of cast in a continuous casting process and the kind of treating steel, its history, etc., in the degassing process having effect on the decarburizing speed exerting on the necessary degassing time are obtd. Successively, the relation between the blowing-off carbon quantity and the necessary degassing time and the relation between the blowing-off carbon quantity and the producing cost of the degassing process are obtd. from the target carbon quantity after degassing and the above values, and successively, the relation between the blowing-off carbon quantity and the producing cost of the converter process is obtd. The blowing-off carbon quantity by which the total cost of the degassing process and the converter process becomes lowest, is used as the target carbon quantity in the converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining carbon in a converter for blowing steel in steelmaking, and in particular, in consideration of changes in conditions such as history of treated steel in the degassing process, the treatment process is positively performed.
The present invention relates to a method of determining carbon blown by a converter in a steelmaking process in which the treatment content is changed.

[0002]

2. Description of the Related Art Generally, in a converter in an iron mill, molten steel produced in a blast furnace is produced by a process in which carbon in the molten pig iron is reduced by oxygen and alloy iron is added. Molten steel produced in the converter is once transferred to a ladle,
After processing such as bubbling, the tundish is passed through a mold to form a continuously cast slab. In this case, in the method of determining the blowout carbon in the converter, the treatment contents of the blowout carbon and the degassing process are determined and fixed in advance from the balance of manufacturing cost and process capability for each steel type.

[0003]

As described above, in the method of determining converter blowout carbon, the contents of the converter blowout carbon and the degassing process are determined in advance from the balance of manufacturing cost and process capability for each steel type. In the actual situation, the carbonization time for obtaining the target carbon for the converter blowing carbon and the degassing process differs depending on, for example, the history of treated steel in the degassing process. It is impossible to reduce the total manufacturing cost unless the processing contents are matched with the cost and capacity in the carbon-free and degassing process. That is, there is a problem that it is not possible to reduce the total manufacturing cost with a fixed standard.

[0004]

[Means for Solving the Problems] In order to solve the above-mentioned problems, as a result of intensive studies by the inventors, as a result of the change in conditions such as the history of treated steel in the degassing process It is an object of the present invention to provide a method for determining carbon blown by a converter in a steelmaking process, which dynamically changes the treatment process and the treatment contents so that the production cost in the degassing process becomes the lowest.
Where the gist of the invention is, in the method for determining the converter blowing carbon that the manufacturing cost in the converter process and the degassing process is the lowest, the manufacturing cost of the degassing process that is obtained in advance by the degassing time, Decarburization of the degassing process such as the manufacturing cost of the converter process, which is calculated from the converter blown carbon and the required converter blowing time, the order of casting in the continuous casting process, the processing steel grade history of the degassing process, etc. The effect of the factors affecting the speed on the required degassing time is calculated in advance,
The relationship between the blowout carbon and the required degassing time, and the relation between the blowout carbon and the manufacturing cost of the degassing process are obtained from the target carbon after degassing of the charge and each value of the factors affecting the decarburization rate. , Next, obtain the relationship between the blowing carbon of the charge and the manufacturing cost of the converter process, and set the blowing carbon that has the lowest total manufacturing cost of the degassing process and the converter process as the target carbon of the converter. The method for determining blown carbon of a converter is characterized by:

[0005]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a series of steps for carrying out the present invention. As shown in FIG. 1, the pig iron discharged from the blast furnace is subjected to de-Si treatment, dephosphorization and desulfurization are performed as hot metal pretreatment, and then hot metal is discharged, and top blowing oxygen blowing is performed in the converter 1. After decarbonization, denitrification and dehydrogenation are performed by secondary refining, for example, by RH vacuum degassing treatment 2 to perform high-purity molten steel in a continuous casting 3 to produce a slab 4 in a continuous continuous process.

FIG. 2 is a diagram showing the relationship between the blowing time in the converter and the blowing carbon. As shown in FIG. 2, the decarburization time is different in order to obtain the target carbon after treatment depending on whether the carbon of the previously charged steel grade is high or low, and the high carbon steel grade of the previous charge is different. The decarburization time this time after the smelting is due to the effects of high carbon steel remaining in the converter and the metal deposits in the furnace due to high carbon steel, etc. It becomes clear that the decarburization time for obtaining the target carbon after blowing the low carbon steel type with the previous charge is short. As described above, the previous treated steel type history has a great influence on the decarburization time to be performed next time. Therefore, it is necessary to correct the decarburization time in consideration of this influence.

FIG. 3 is a diagram showing the relationship between the blowout carbon and the manufacturing cost performance index. As shown in this figure, regarding the relationship between each blowing carbon in the converter and vacuum degassing (RH) and the manufacturing cost, in the converter, the manufacturing cost by blowing is lower as the blowing carbon is higher. . On the contrary, in the vacuum degassing process (RH), the manufacturing cost performance index increases as the blowing carbon increases. As described above, the manufacturing costs in the converter and the RH differ depending on the level of blown carbon. Therefore, by utilizing the characteristics of each of the converter and the RH, it is possible to implement an operating method for obtaining a comprehensively low manufacturing cost.
Therefore, the manufacturing cost performance index curve (converter + RH) in which both are used together is shown above.

Similar to FIG. 2, the symbols and are the curves when the previous charged steel grade has a high carbon treatment history, and the previous charged steel grade has a low carbon treatment history. The relationship between each blown carbon and the manufacturing cost performance index is shown.

As described above, since the converter and the RH have different manufacturing costs for decarburizing the target carbon, the converter blowing and the degassing step have the lowest manufacturing costs. In order to determine carbon, it is necessary to determine it from the balance between both the degassing process and the converter process. Therefore, for example, from the curve showing the relationship between the overall manufacturing cost performance index of both the converter and the RH shown in FIG. 3, in the case where the cheapest value of blown carbon is 4.8 × 10 ^-2 %, It can be seen that is 3.8 × 10 ^-2 %. in this way,
The production cost of the degassing process and the production process of the converter process should be calculated in advance, and the degassing process and the converter process should be considered in consideration of the effect of factors affecting the decarburization rate, such as the history of treated steel, on the required degassing time. It is possible to reduce the manufacturing cost by making the target carbon of the converter be the blown carbon which has the lowest total manufacturing cost with the process.

[0010]

As described above, by performing the operation in consideration of the total manufacturing cost of both the converter process and the degassing process in consideration of the influence of the precharge component according to the present invention,
It has an excellent effect that low-carbon steel can be manufactured at an extremely low cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a series of steps for carrying out the present invention,

FIG. 2 is a diagram showing a relationship between blowing time in a converter and blowing carbon.

FIG. 3 is a diagram showing a relationship between blown carbon and a manufacturing cost performance index.

[Explanation of symbols]

 1 Converter 2 RH vacuum degassing 3 Continuous casting 4 Slab

Claims (1)

[Claims] 1. A method of determining converter-blown carbon for which the manufacturing cost in a converter process and a degassing process is the lowest, in the method of determining degassing time, the manufacturing cost of the degassing process, and the converter blowing Factors affecting the decarburization rate of the degassing process such as the manufacturing cost of the converter process, which is determined from carbon and the converter blowing time required from it, and the order of casting in the continuous casting process, the history of treated steel grades of the degassing process, etc. And the effect on the required degassing time of the charge, the relationship between the blown carbon and the required degassing time from the target carbon after degassing of the charge and each value of the factors affecting the decarburization rate, The relationship between the blowing carbon and the manufacturing cost of the degassing process is calculated, and then the relationship between the blowing carbon of the charge and the manufacturing cost of the converter process is calculated, and the total manufacturing cost of the degassing process and the converter process is calculated. Converter with minimum blown carbon A method for determining blown carbon in a converter, which is characterized by using the target carbon of