JPH05156339A - Method for assuming carbon concentration in molten steel in converter refining - Google Patents

Abstract

PURPOSE:To assume precisely carbon concn. in molten steel and to smoothly execute the converter operation by substituting the molten steel manganese concn. assumed value and the measured value of solidified temp. in the molten steel calculated from the measured values of the molten steel temp. and dissolved oxygen concn. into a specific equation. CONSTITUTION:Into the molten steel 2 incorporated in the converter 1, the oxygen is blown from an oxygen lance 10 to execute the refining. In the above blow-refining of the converter, by a sublance 3 providing a lifting device, the temp. of the molten steel 2, the dissolved oxygen concn. and the solidified temp. are measured and these measured values are inputted into a calculator for process. In an arithmetic device 8 in this calculator, based on the above molten steel temp. and the dissolved oxygen concn. and the operational data from a storing device 7, the manganese concn. in the molten steel 2 is calculated. Successively, the above mol-ten steel solidified temp. and the manganese concn. assumed value are substituted into the equation: Ts= k1[%C]<2>+(k2+k3[%Mn]) [%C]+k4[%Mn]<2>+k5[%Mn]+k6 (wherein, Ts: molten steel solidified temp., [%C]: carbon concn. in the molten steel, [%Mn]: manganese concn. assumed value in the molten steel, k1 to k6: constant).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating molten steel carbon concentration in converter refining.

[0002]

2. Description of the Related Art In the method of estimating the carbon concentration in molten steel, generally, the carbon concentration is estimated from the solidification temperature of molten steel measured by sublance using a calibration curve.

However, when the Mn concentration in the molten steel becomes 0.2% or more as in the less slag refining, the freezing point is lowered by Mn. Therefore, if the carbon concentration in the molten steel is simply calculated from the solidification temperature, an error occurs. May become large and the components may be out of alignment. Therefore, it has been put into practical use to estimate the carbon concentration by multiplying the Mn concentration in molten steel by a constant and correcting the carbon concentration estimation method from the conventional solidification temperature.

As an example, Japanese Patent Application Laid-Open No. 2-57629 discloses "a converter molten steel carbon estimation method". That is, in the method for estimating the carbon content of molten steel during converter refining using dephosphorized hot metal, the following converter molten steel carbon estimation method including the following is described.

Collecting molten steel and measuring its temperature and solidification temperature; obtaining a primary estimated carbon amount in the molten steel from the solidification temperature; using the primary estimated carbon amount and the molten steel temperature; Obtaining the estimated Mn amount in molten steel from the Mn equilibrium equation and mass balance equation, obtaining the carbon amount using the primary estimated carbon amount and the estimated Mn amount, where carbon [% C] in the molten steel is practical With linear accuracy as a linear expression of Ts and [% Mn],
It is expressed by equation (1).

[0006]

[Equation 2]

[0007]

However, although the above-mentioned method has improved accuracy as compared with the method for estimating the carbon concentration calculated from the solidification temperature of molten steel by using a calibration curve, the value which is still satisfactory cannot be obtained. I haven't arrived.

The present invention has been made to solve the above problems, and provides a method for estimating the carbon concentration of molten steel with which the carbon concentration in molten steel can be accurately estimated even when the Mn concentration in the molten steel is high. The purpose is to

[0009]

In order to achieve the above object, the present invention measures the molten steel temperature and the dissolved oxygen concentration of molten steel in converter refining, and estimates the molten steel manganese concentration estimated from those measured values. The value and the measured solidification temperature of the molten steel are substituted into the following formula to estimate the molten steel carbon concentration, which is a method for estimating the molten steel carbon concentration in converter smelting.

[0010]

[Equation 3]

[0011]

[Equation 4]

In equations (3) to (6), unknowns are MnO concentration% in slag, Mn concentration% in molten steel, and FeO in slag.
The concentration% and the slag amount are four, and the rest are known amounts. That is, the molten steel temperature and the dissolved oxygen are amounts that can be directly measured by the sublance. The amount of manganese supplied is the main raw material (hot metal),
It is calculated as the sum of the amounts of manganese contained in each of the charging scrap and auxiliary raw materials.

The molten steel amount can be calculated by multiplying the charging amount by the yield. Furthermore, the amount of other slag is specifically the amount of MnO, SiO ₂ , and CaO, which can be calculated from the amount of hot metal, the hot metal component, and the amount of auxiliary raw material charged.

Thus obtained [% Mn],
[% C] is obtained by substituting Ts into the equation (7) obtained by solving the equation (2).

[0015]

[Equation 5]

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an apparatus used in the present invention. In the figure, 1 is a converter, 2 is molten steel, 3 is suprance, 4 is a process computer, 5 is a sublance lifting device,
A display device 6 is a CRT display or the like. The temperature and the dissolved oxygen concentration of the molten steel 2 produced by refining the converter 1 are measured by the sublance 3. 10 is an oxygen lance.

The result is input to the process computer 4. In the process computer 4, the storage device 7 is input with operating data such as the amount of hot metal, the components, and the actual results of the auxiliary raw materials.
The Mn concentration in the molten steel is calculated by the arithmetic unit 8 from the operation data and the input data from the sublance. Solidification temperature data measured with the same sublance is 2 from molten steel temperature data.
When input to the process computer 4 with a delay of 0 to 30 seconds, the carbon concentration in molten steel is calculated by the arithmetic unit 8.

In the above equation (2), k _1, k _2, k _3, k _4,
k _{5 and} k ₆ are constants and are values obtained by multiple regression analysis based on data of several tens of points, and k ₁ = 0.80, k ₂ = -82.86, k ₃ = 5.82, k ₄ = 4.31, k
_{4 = 4.31, k 5 = -8.65} , is set to k ₆ = 1537.99. The calculation result is displayed on the CRT display 6a. At the same time, as a result, a command is issued to the control device 9.

The series of steps will be described with reference to FIG.
In the storage device 8 of the process computer 4, hot metal amount, hot metal component, scrap amount, scrap component, auxiliary raw material input amount, and auxiliary raw material component are input as an operation database.

The arithmetic unit 8 calculates the manganese concentration estimated value in the molten steel from the operation data from the storage unit 7, the molten steel temperature and the dissolved oxygen concentration measured by the sublance 3, and the same sublance is used for the measurement. An estimated value of the carbon concentration of the molten steel is calculated from the measured value of the solidification temperature of the molten steel and the estimated value of the manganese concentration in the molten steel.

The carbon concentration of the molten steel is displayed on the CRT display 6a. At the same time, the controller 9 issues a command to the converter operation based on the result. According to the above, it is possible to accurately measure the carbon concentration in molten steel having a manganese concentration in the molten steel of 0.1% or more in the range of 0.04 to 0.5% in the molten steel.

The range of the carbon concentration in the molten steel of 0.04 to 0.5% is generally adjusted as the carbon concentration of the molten steel in the steelmaking method. Manganese concentration in molten steel is 0.1
% Or more is a range that generally affects the measurement of carbon concentration by the solidification temperature of molten steel. The upper limit is not particularly limited, but practically up to 1.0% is often applied.

FIG. 3 shows the result of obtaining the accuracy of the estimated value of the carbon concentration in the molten steel according to the present invention. Figure 4 shows a comparison
This is a conventional example. As is clear from FIGS. 3 and 4, the accuracy of the present invention is much higher than that of the prior art.

According to the method of the present invention, the estimated value and the chemical analysis value are compared in accuracy, and the error average is -0.0002.
%, And the standard deviation was 0.006%. On the other hand, in the conventional method using the linear equation for estimating the carbon concentration, the average error was 0.014% and the standard deviation was 0.035%. According to the present invention, the component deviation was reduced from 0.3% to 1.0%.

[0025]

According to the present invention, even if the Mn concentration in the molten steel is high, the carbon concentration in the molten steel can be accurately determined. Therefore, the converter operation can be made smooth.

[Brief description of drawings]

FIG. 1 is a diagram showing a state of an embodiment of the present invention.

FIG. 2 is a diagram showing a flow of carbon concentration estimation according to an embodiment of the present invention.

FIG. 3 is a diagram showing the accuracy of the estimated carbon concentration according to the embodiment of the present invention.

FIG. 4 is a diagram showing the accuracy of an estimated carbon concentration in a conventional example.

[Explanation of symbols]

 1 Converter 2 Molten Steel 3 Sublance 4 Process Computer 5 Sublance Lifting Device 6 Display Device 6a CRT Display 7 Storage Device 8 Computing Device 9 Control Device 10 Oxygen Lance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaki Takenaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Chihiro Taki 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside the steel pipe company

Claims (1)

[Claims] 1. A molten steel temperature and a dissolved oxygen concentration of molten steel in a converter refining are measured, and a molten steel manganese concentration estimated value estimated from the measured values and the solidified temperature measurement value of the molten steel are substituted into the following formula. A method for estimating molten steel carbon concentration in converter refining, which comprises estimating molten steel carbon concentration. [Equation 1]