JPH01298109A - Method for controlling manganese content at the time of stopping blowing in converter - Google Patents

Abstract

PURPOSE:To control Mn content in molten steel to be aimed at good accuracy and to improve the hitting ratio of C content at the time of stopping blowing by obtaining assumed Mn content from measured values of temp. and C content of the molten steel at the end stage of refining at the time of steelmaking refining in a converter from dephosphorized molten iron as raw material and further, comparing the assumed Mn at the time of stopping the blowing obtd. from end point control model. CONSTITUTION:At the time of producing the molten steel by decarburized refining with oxygen blowing after charging the pre-dephosphorized molten iron into the oxygen top and bottom flowing converter, the temp. and C content in the molten steel at end stage of blowing are measured with the sub-lance and the assumed value of Mn in the end stage of the blowing is obtd. from these measured values. At the same time, the assumed Mn content at the time of stopping the blowing is obtd. based on the assumed C content and temp. at the time of stopping the blowing calculated with the end point control model from the above both measured values. From the assumed Mn, etc., at the end stage of the flowing and the assumed Mn content at the time of stopping the flowing, O2 quality consumed with oxidized loss of Mn, is calculated, and the oxidized loss O2 quantity for Mn is added to the additional O2 quantity needed to decarburization and the raising temp. calculated with the end point model and the end point blowing is executed and Mn content at the time of stopping the blowing into the converter is controlled and C level in the molten steel at the end stage is accurately hit to the aimed value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a converter blow-off manganese control method for precisely controlling the target manganese content in a steel bath in converter blowing using dephosphorized hot metal. It is related to.

[Conventional technology] Conventional converter end point control technology has a low manganese content in the steel bath (
This is for controlling under conditions (0.2 to 0.5 νt%). However, no specific proposal has been made regarding a method for estimating the amount of manganese in a steel bath based on information obtained from sublance measurements at the end of blowing and using this for control of manganese at the end of blowing.

[Problem to be solved by the invention] Conventional converter end point control technology performs end point control under the conditions described above, and in converter blowing using dephosphorized hot metal, manganese ore is Due to direct reduction, the steel bath manganese content is as high as 0.5 to 5 vt%, and if the conventional technology is applied as is, the effect of manganese oxidation will not be reflected, resulting in poor end point control accuracy and a decrease in the blow-off rate. There was a problem.

In order to solve the above-mentioned problems of the conventional technology in converter blowing using dephosphorized hot metal, the present invention provides end-point manganese control by reflecting the amount of oxygen lost due to manganese oxidation in the conventional dynamic control. The purpose of the present invention is to provide a method for controlling manganese blowing up in a converter with the aim of improving the quality of manganese.

[Means for Solving the Problems] The converter blow-off manganese control method according to the present invention is a converter refining method using dephosphorized hot metal, and the converter end point is adjusted to adjust the composition and temperature of the steel bath to target values. In the control method, the carbon content and temperature of the steel bath are measured at the final stage of blowing, and based on the measured values, the estimated manganese content at the final stage of blowing is calculated, and the expected carbon content at the end of blowing is calculated from the end point control model. Based on the expected temperature at the end of blowing, the estimated amount of manganese at the end of blowing is calculated, and the amount of oxygen consumed due to manganese oxidation loss is calculated from the estimated amount of manganese at the end of blowing and the expected amount of manganese at the end of blowing. This is a converter blow-off manganese control method that performs end point control by adding the amount of oxygen loss due to manganese oxidation to the calculated amount of additional oxygen required for decarburization and temperature rise.

[Function] In order to solve the problems in the prior art as described above, the present inventors investigated the relationship between the carbon content and the manganese content at the final stage of blowing, and found that the carbon content (vt%) of the steel bath It was determined that the relationship with steel bath manganese ffi (wt%) was as shown in FIG. From this, the steel bath manganese tends to increase due to the reduction of manganese ore until the decarburization transition point [C]T, and after the decarburization transition point [C]□, the total iron content in the slag increases due to the oxidation reaction of iron. It was found that, on the contrary, it followed a decreasing trend.

Therefore, the oxygen blown into the steel bath at the final stage of blowing is consumed not only by decarburization reactions and iron oxidation reactions, but also by manganese oxidation reactions.

Therefore, the following method was applied to determine the amount of oxygen consumed by manganese oxidation.

First, in order to obtain the manganese in the steel bath at the time of sublance measurement at the end of blowing, from the manganese balance equation [(1)] and manganese balance equation C(2)], the estimated manganese content at the blowing stage [
Find Mn]s.

log(Mn)s/[Mnl s=log(A/C
O]s)+B/Ts+C・(1) WsTx [Mr+CoS+SiSI,X (Mn
)s ” vP x [:Mn1P+δ ×
v...(2) n0RE However, (Mn)+ Mn component in varnish slag, Ti: Molten steel temperature [M
nl: Mn component in molten steel, W: weight J [C]: C component in molten steel, δ: Mn content in Mn ore.

A, B, C: constants.

1-8: At the time of sublance measurement, E: At the time of blow-off, P: Hot metal.

j-3T: Molten steel, SL Nislag, P: Hot metal.

Nn0RE: Mn ore Solve equation (2) for (Mn)s and solve (Mn) of equation (1)
) and solve the nonlinear equation.

This can be easily solved using a computer using the Newton-Rhapson method or the like.

At the same time, the amount of oxygen required to obtain the target carbon content and temperature is calculated using dynamic control based on the carbon content and molten steel temperature measured by the sublance.

Usually, the calculation result of dynamic control is that carbon may be blown down in order to ensure the target temperature, and it is known to simultaneously calculate the expected amount of carbon at the end of blow-off and the expected end-of-flow temperature.

゛Therefore, from the expected amount of carbon at the end of the blow and the expected temperature at the end of the blow, (1
), From equation (2), the predicted manganese component [Mn1
We can find E. The calculation method is as described above. At this time, the amount of oxygen consumed by manganese oxidation is: △O-([M]3-[Mn]E) .

Mn WT2 total charging amount It can be calculated as

Adding △σMn obtained by formula (3) to the additional oxygen amount △O obtained by dynamic control calculation, △0−△O+△
0...(4) T c On However, △0 Nidotal additional oxygen amount △0: As the dynamic control additional oxygen amount C, the additional oxygen amount △0. can be found.

At this time, in the actual blowing, the blowing may be completed when an additional oxygen amount ΔOT is blown from the cumulative oxygen amount at the time of sublance measurement.

It goes without saying that if iron ore is introduced after sublance measurement, the amount of oxygen contained in the iron ore (20ON3/T) needs to be reflected in the amount of additional oxygen.

Next, examples of the method of the present invention will be described.

[Example 250T top-bottom blowing converter was equipped with dephosphorized hot metal C4.2%, St
tr.

MnO, 16%, P 0.017% were charged, and blowing was carried out at a target blow-off carbon of 0.140%, blow-stop manganese 1.40%, and blow-off temperature of 1640°C.

When the carbon content and temperature were measured using a sublance at the end of blowing, the carbon content was 0.607% and the temperature was 1604°C.

Here, from the following equations (1) and (2), log(Mn
) /[:Mnl s -1og (A/
[C. )+BITs+C...(1> WX[Mnko + W x (Mn)s
-WP x [Mn] PST S
SL +δ× ν...(2) n0RE However, (Mn) Mn component in the varnish slag Tl: Molten steel temperature [M
nl: Mn component in molten steel W, : Weight J [C]: C component in molten steel δ; Mn content in Mn ore A,
B, C: constant i=s: during sublance measurement, E: during blow-off, P: hot metal.

j-3T two molten steel, SL: slag, P: hot metal.

Mn0RE: Mn ore estimated manganese component [Mn1S was calculated, [Mnl
3-1.56% was obtained.

At the same time, from the dynamic control model, the expected blow-off carbon content is 0.144%, the expected temperature is 1643°C, and the additional oxygen amount ΔO = 125ONm3. 0.6T of iron ore for cooling was obtained.

Therefore, based on the expected carbon content and temperature, the above (1)
When the predicted manganese blowout was calculated from the formula (2), [MncoE-1, 31% was obtained.

Furthermore, when the amount of oxygen consumed by manganese oxidation was calculated from the following equation (3), ΔT:) -14Nm3 was obtained.

Mn △σ − ([M] [Mn]E) X 1010l
X 11.2 After putting BT into the furnace and blowing in ``1144N [D'' as an additional amount of oxygen, when the blow-off was stopped, the blow-off carbon (1,147
A good result with a good continuity rate was obtained at a temperature of 1643° C. with an X-blown manganese content of 1.34%.

Table 1 below shows a comparison of the effects of the method of the present invention and the conventional method.

Further, FIGS. 2 and 3 are graphs showing the relationship between the target manganese and the blowout manganese for the method of the present invention and the conventional method, respectively.

As shown in Table 1 and FIGS. 2 and 3, according to the converter blow-off manganese control method of the present invention, the target manganese (wt
%) - Actual manganese (vt%) is 0.051 on average
%, σ is 0.072%, and the average value in the conventional method is 0.
．． It is clear that the estimation accuracy is improved compared to 231% and σ0.319%.

The blow-off manganese control method according to the method of the present invention can be applied to converter blowing using dephosphorized hot metal regardless of the size of blow-off manganese.

[Effects of the Invention] By applying the converter blow-off manganese control method of the present invention to converter blowing using dephosphorized hot metal, it improves the accuracy of estimating the amount of manganese at the time of converter blow-off, and The simultaneous success rate of carbon content and temperature was improved, and as a result, the effect of significantly reducing the reblowing ratio due to unsuitable manganese and carbon content was obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between steel bath carbon and manganese at the final stage of blowing, FIG. 2 is a graph showing the relationship between target manganese and blow-off manganese in an embodiment of the method of the present invention, and FIG. It is a graph showing the relationship between target manganese and blow-off manganese.

Claims (1)

[Claims] In a converter refining method using dephosphorized hot metal, the carbon content and temperature of the steel bath are measured at the end of blowing in a converter end point control method for adjusting the composition and temperature of the steel bath to target values. Based on the measured values, the estimated amount of manganese at the end of blowing is calculated, and the estimated amount of manganese at the end of blowing is calculated based on the expected amount of carbon at the end of blowing and the expected temperature at the end of blowing calculated from the end point control model. Calculate the amount of oxygen consumed by manganese oxidation loss from the estimated amount of manganese and the expected amount of manganese at blow-off, and add the amount of oxygen lost from manganese oxidation to the additional amount of oxygen required for decarburization and temperature rise calculated using the end point control model. A converter blow-off manganese control method characterized by performing end point control.