JPS5819723B2 - Tenrosougiyouhouhou - Google Patents

Description

[Detailed description of the invention] The present invention relates to a converter operating method.

Methods for measuring the components of converter-blown molten steel include thermodyne method, exhaust gas analysis method, and sublance method.

The concept of the above-mentioned sublance method is to sample molten steel during blowing, measure the C content in the steel at that point, and calculate the blowing time etc. to achieve the target C content thereafter.

However, it has been found that such a method does not yield satisfactory results when applied to actual operations.

The method of the present invention is based on the premise that when blowing steel, accurate and rapid measurement technology of molten steel temperature and composition (mainly C and P, 5fj) by the sublance method is fully utilized throughout the blowing process. This is to accurately predict the blowout components, etc., and to accurately grasp the steel components, etc. during tapping, and to ensure the amount of ferroalloy added in subsequent processes, thereby improving quality. , its characteristics include the temperature of molten steel and the components (C, P, S) in the steel during blowing in converter blowing.
Measure the following blowing conditions at the end of blowing to achieve the target components (c, s, p) at the end of blowing (blowing time and amount of oxidation)
is determined, blowing is performed based on the determined value, and then the temperature of the molten steel and the components in the steel (the amount of C20) are measured at the end of blowing.

As is well known, the components that greatly affect the quality of steel are C, Mn, S, and P, and the temperature of molten steel is a factor that affects the subsequent processes such as ingot making and continuous casting. In the present invention, the molten steel temperature and C, Mn, S, and P in the steel are measured during the above-mentioned blowing process.
For example, in the case of ordinary steel, the measurement time point is 2 to 2 seconds before blow-stopping.
By measuring at 6 minutes, based on the results, the target temperature at the end of blowing, the blowing time for the components, and the amount of oxygen passed (oxygen amount for blowing) are calculated, and blowing is performed based on this. This is to stop the target value.

Such measurements during blowing can be carried out by sampling the molten steel using a sublance, in which case the temperature can be measured immediately, or C can be measured at the solidification temperature, Mn, S.

P can be measured in several tens of seconds using a Kantopack.

However, as a mode of temperature measurement, for example, the target temperature and the temperature measurement result are introduced into a computing unit, and Q=('r-'r1)xK (however,
Q: Oxidation amount, T: Molten steel temperature during temperature measurement, T1: Target temperature,
The amount of oxygen passing from the time of temperature measurement to the time of blow-off is calculated using the formula K: temperature increase rate (°C/Nm02).

In addition, as a method to measure the amount of C in steel from the solidification temperature and determine the amount of oxidation from the time of measurement to the time of blow-off, the method is to measure C in steel in the same way.
Introduce the quantity and target C value to the calculator, Q1=(C-01)×
k (however, Ql: amount of oxygen passed, C: amount of molten steel C at the time of temperature measurement, C1
: Target C amount, k: Decarburization rate %C/Nm'02) Calculate the amount of oxygen passing from the time of measurement to the time of blow-off.

Also, the overacid time (blowing time) is calculated from the amount of oxygen passed per unit time.

From this, if Q=Q, blowing continues according to '-Q'.

In the case of Q>QI, blowing continues according to ″>Q.

If Q<Ql... Add coolant and blow according to correction Q1.

(Correction Q1: Correct Ql by the amount of decarburization of the coolant.

) While the blowing continues in this manner, the measured values of P and S are determined by Cantpack analysis, and the following aspects are distinguished.

Estimated end P amount ≦ Target P amount ・・・・・・・・・ (1)
Estimated blow-off P amount>Target P amount ・・・・・・・・・ (2)
Estimated blow-off S amount ≦ Target S amount ・・・・・・・・・ (3)
Estimated blow-off S amount>Target S amount ・・・・・・・・・ (4)
However, in cases (1,) and (3) above, blowing is carried out as is in the state of 5, and in cases (2) and (4), dephosphorization and desulfurization are performed by adding quicklime and fluorite, etc. Facilitate.

In this case, the model formula for estimating the blowhole P and S is, for example, the estimated blowhole P amount - (P% measured during blowing) - 1 x △02 blowhole S deposition amount = - (s% measured during blowing) ) -1<2X△0□However, 1- theory P speed (0,001~0.0034/Nm0
2) k2 = theory S speed (0,001 to 0.002%/
Nrr Estimated P amount - Target P amount) x ρ1 or (Estimated stop S amount - Target S amount) x ρ2 Estimated stop P amount - Target P amount) x ρ3 or (Estimated stop S amount - Target S Calculated by: (amount) x ρ4.

However, ρ1 to ρ4 are the amounts of quicklime or fluorite necessary to lower P or S by o, o1%.

In this way, the above-mentioned control is carried out from the measurement point during blowing to blowing 1, and after the blowing is stopped and before tapping, the molten steel is measured by the sublance method as described below, and based on the results, the molten steel is tapped. However, it is extremely important to carry out processing that takes into account various conditions such as the addition yield of ferroalloy and the tapping temperature in the process after tapping, which contributes to improving quality.

That is, as measurement elements for the molten steel after blow-stopping and before tapping, the molten steel temperature and the amount of C2O in the molten steel are measured by the sublance method.

In other words, the temperature of the molten steel can be adjusted to prevent cracking during pouring in the subsequent process, and the amount of C in the steel can be reduced by carburization even after tapping.
Since the amount can be adjusted, even if the amount of C is lower than the target blow-off amount, priority is given to controlling other elements such as molten steel temperature, steel P, S, etc. to the target values.
It is necessary to measure the amount of oxygen in the steel to determine whether or not to carburize it if necessary.Also, depending on the amount of oxygen in the steel (free oxygen), it will react with the oxygen in the steel when adding ferroalloy later, and The yield will be poor, and therefore, unless the oxygen in the steel is accurately known, it will not be possible to precisely adjust the steel type by adding ferroalloy, and there are cases in which the finished product will not be produced, especially in special steels.

Furthermore, by measuring the amount of oxygen in the steel, the amount of C in the steel can be accurately determined.

In other words, if the C content in steel is about 0.12 fb or more, it can be easily measured by the solidification temperature as described above, but if it is less than about 0.12%, it is difficult to accurately measure it by the solidification temperature. For example, in the case of blowing low carbon steel, when the amount of C in the steel is stopped at about 0.12% or less, the amount of C can be accurately grasped by estimating the amount of C from the amount of oxygen in the steel.

By doing this, P, S, etc. in the steel can be accurately stopped at the target value, but it is effective to measure for final confirmation.

Further, other components such as Mn can also be controlled.

By carrying out the method of the present invention as described above, the following excellent effects can be obtained.

Since the temperature of molten steel and the components in the steel can be accurately controlled (adjusted), quality can be dramatically improved.

Furthermore, by accurately grasping the amount of oxygen before tapping, the amount of ferroalloy added can be made precise, and from this point as well, excellent effects such as the ability to significantly improve the quality of the finished product can be obtained.

Next, an example of a control mode according to the method of the present invention will be described.

In the drawing, the temperature of molten steel during blowing, C, is measured by measuring device 1.
Measure the amount and immediately introduce it into the calculator 2. For other P, S, etc., measure the taken out molten steel with the Cantopack analyzer 3, and similarly introduce it into the calculator 2, and adjust the composition to the target value under the current blowing conditions. If it is necessary to change the blowing conditions, make the necessary adjustments as shown in the figure. Immediately after the blowing stops, measure various elements with the measuring device 1' as shown in the figure. In addition to determining the necessity, etc., the amount to be added is specified in accordance with the amount of O and taking into account the yield of ferroalloy.

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

210 tons of such hot metal, 7 tons of scale, and 2 tons of limestone as auxiliary raw materials.
0.5t of fluorite was charged and ordinary steel was blown as follows.

(1) Peracid rate: 70 ON for 7 minutes (2) Peracid pressure: 8.5 kg/1 (3) Distance between oxygen blowing lance and hot water level: 2000 mm Blow + h under these conditions, C: 0.08, P: 0 .01
%, S: 0.02 ratio, temperature: In order to achieve 1600°C, the planned oxygen amount for blowing was set to 1l100ON, and 700ONm.
``The molten steel being blown after peracid was taken by the sublance method and measured with a measuring device, and the C: 0.5% (determined by solidification temperature)
, Temperature: 1580°C was introduced into the computer, and then P: 0.04 and S: 0.021 were measured using a 1 minute diameter Cantopack analyzer.
% value, immediately input it into the computer, and calculate as above, the peracid amount is 70ON i/min, the peracid pressure is 8.5
kq/cit, hot water level spacing 20oO, the amount of superoxidation up to the end of blowing is calculated to be 2100Nm3, and based on this, the above correction is made, and since the molten steel temperature will be higher than the target value after the next 5 blowings, it is used as a coolant. Iron ore2. I blew it while adding Ot and it failed.

Then, the molten steel is immediately sampled using the sublance method and measured using the measuring device 1.
', C: 0.06 ratio, p: o, os ratio, S: 0
．． 0] Section 9, 0: 0.05%, Mn: 0.20%,
A measurement result of a temperature of 1605°C was obtained, which was immediately introduced into the computer 2, and instructions were given to introduce 2.21% of ferroalloy (Fe-Mn).At the same time, since C was lower than the target value, it became necessary to carburize. The other conditions meet the target values and there is no need for adjustment, so in the tapping ladle, F
E-Mn (ferroalloy) was introduced, coke powder was added as a carburizer to the upper surface of the molten steel, the amount of C was adjusted, and a predetermined amount of pot deoxidation was performed, followed by ingot formation of rimmed steel.

As described above, according to the present invention, the components, temperature, etc. can be adjusted to target values without any troubles during blowing such as after-blowing.

[Brief explanation of the drawing]

The drawing is a block diagram showing a control aspect of the method of the present invention. 1...Measuring device, 2...-...Calculator, 3.
・－・・・Analyzer (cantback).

Claims (1)

[Claims] 1 (4) The molten steel being blown in an oxygen top blowing converter is sampled by the sublance method, the molten steel temperature is measured, the C content is measured at the solidification temperature of the molten steel, and the P, Measure the amount of S, (b) then Q = ('r-'ri) Calculate the amount of oxygen passing from the time of temperature measurement to the time of blow-off based on the formula of N m'-02), and calculate the amount of oxygen passed from the time of temperature measurement to the time of blow-off, and Ql-(CC1) C amount of molten steel at time, C1: Target C amount, k
: Calculate the amount of oxidation from the time of measurement to the end of blowing based on the formula of coal drying speed coefficient C/Nraney 0□), (d) If Q = Qt, blow according to Q as it is, Q, >Q1, blowing is continued according to Ql, and when Q<Ql, coolant is added and blowing is performed according to Ql corrected by the amount of decarburization of the coolant, (e) Blowing is continued. Estimated blow-off P, from the measured values of P and S obtained by cantback analysis.
Find the S amount and compare it with the target P and S amount to determine the estimated stop P,
If the S amount is less than the target P, S amount, blowing is continued, and if the estimated blowout P, S amount is greater than the target P, S amount, quicklime and banding are added to perform dephosphorization and desulfurization. (to) Thus, after blowstopping and before tapping, the temperature of the molten steel and the C in the molten steel decrease.
A converter operating method characterized in that the amount of 2O is measured by a sublance method, and if the amount of C is lower than the target blow-off amount, carburization is performed, and the amount of ferroalloy added is adjusted based on the amount of C.