DE2361420A1 - PROCEDURES FOR CONTROL AND REGULATION OF THE TEMPERATURE AND THE CARBON CONTENT OF A STEEL MELT - Google Patents

Description

PATENTANWÄLTE HENKEL— KERN - FEILER - HÄNZEL— MÜLLER

DR. PHIL. DIPL.-ING. DR. RER. NAT. DIPL.-ING. DIPL.-ING.

0529802 HNKi. D EDUARD-SCHMID-STRASSE 2 V ^ S ^ S ^^ S ^ s

in _ÄÄ ι, _ο · τ ^ _1n Q _{1 Q7} WECHSELBANK MUNICH NO. 318-S5

I "rsom * Munich D-8000 MUNICH 90 Postal check: mchn rezi 47-

Nippon Kokan Kabushiki Kaisha ^ oor ι / on

. _ ■ ZOD I4ZU

Tokxo, Japan

_/ ' 10 DEC. 1973

Method for controlling or regulating the temperature and the carbon content of a steel melt

The invention relates to a method for controlling or "regulating the temperature and the carbon content of a steel" melt.

The invention relates generally to inflation oxygen converters and specifically to a control method therefor in which during the oxygen blowing operation of the converter a probe or a mill inserted into the molten steel is used to adjust the temperature and the carbon content of the To measure molten steel, on the basis of the measured values the temperature and the carbon content of the molten steel at Oxygen inflation endpoint can be controlled at the same time.

The known methods for controlling the temperature and des The carbon content of molten steel at the end point of oxygen inflation in converters fall into two general classes: Let me take a look at the way at which the temperature or the carbon content of the steel melt by an in this inserted probe is measured to simply determine the tempe-

^{Ee / B1 / Ho} 40982B / 08O

temperature or the carbon content at the end point depending on. ability of. the. to control the measured values obtained, and on the two- », th. in. the way in which the temperature measurement by means of a In the molten steel introduced probe takes place, while the carbon content by means of a separate probe or a separate .. Mhlers or determined on the basis of information being that of another. Source than the steel melt originate, e.g. from the analysis of the exhaust gases, which increases the temperature and the carbon content of the steel melt at the end « point can be controlled at the same time.

A disadvantage of the former method is that that it is a single control process in which either the temperature or the carbon content on the End point is controlled or · regulated alone. The second one In the process, the defect is liable to the fact that as a result of the use of two or more radiators or probes or the Using the information obtained from the analysis of the exhaust gases not only requires a greater amount of equipment and labor is required, but also their repeated application over a longer period of time in terms of accuracy and maintenance of the instruments is difficult.

The invention is therefore primarily based on the object of eliminating the aforementioned difficulties and to create a process by means of which the. temperature and the carbon content of the steel melt at the end point of the Oxygen inflation in converters can be controlled simultaneously can. .

This task is used in a method for controlling or regulating the temperature and the carbon content of a steel melt at the end of the fizzling in a blown oxygen converter solved according to the invention in that the raw materials

409825/0847

be prepared in such a way that the temperature of the Molten steel at the end point one above the target temperature on End point lying value reaches that the temperature and the Carbon content of the steel melt by means of a single sensor or probe at the same time after the inflation of the Oxygen can be measured in an amount appropriate to achieve a predetermined molten carbon content the desired carbon content of the steel to be produced is calculated based on the measured values of the temperature and the carbon content, an anticipated heating or Heating factor and decarburization parameters are calculated that based on the anticipated heating factor the Amount of oxygen derived after the measurement Increase the temperature to blow up to an estimated value is that based on the amount of oxygen after the measurement as well as the decarburization parameter a calculated carbon content is determined, and that the one to be injected at the end point Amount of oxygen, a required amount of coolant or that Scheme of light blowing according to the difference between the calculated carbon content at the end point and the Target carbon content at the end point can be calculated, whereby the temperature and the carbon content of the steel melt at the end point can be regulated or controlled simultaneously. .

The mill used according to the invention is capable of at the same time Measure the temperature and carbon content of the molten steel. It consists of a solidification temperature measuring by a Sillzium tube protected thermocouple that arranged in a sample vessel attached to a measuring lance as well as a thermocouple that is attached to the bottom of the sample vessel and measures the steel melt temperature. The feeler is designed in such a way that it offers satisfactory protection for the compensating leads. /,

409825/0847

According to the invention, an exemplary work sequence is carried out for an oxygen top-up converter in such a way that (a) the preparation of the raw materials required for a given temperature is carried out in such a way that the temperature of the steel bar at the end point is slightly higher than the target temperature at the end point, ( b) after the start of inflation, the oxygen rings are calculated and displayed according to a static model, so that the carbon content of the melt has a predetermined value within a range of ₀ 50-100? £, depending on the desired carbon content of the product to be produced Steel, (e.g. $ 0.50 for low and medium carbon steels), (c) that after this amount of oxygen has been inflated, a measuring lance is inserted into the molten steel so that the molten steel temperature and the liquidus temperature are measured simultaneously by a probe or a mill and then the temperature and carbon content of the steel sc The melt can be read from an automatic display program _} (d) and that immediately after the measurement, a predetermined heating factor and decarburization parameters are calculated in order to determine the amount of oxygen required to bring the endpoint temperature to the target temperature at the endpoint If the inflation process is continued under the conditions prevailing at the time of the measurement (i.e. the amount of oxygen blown in to increase the temperature to an estimated value after the measurement), whereupon a calculated carbon content at the end point is determined based on the amount of oxygen thus determined and the decarburization parameters.

At this point it must be determined whether at the end of the up- blowing this calculated amount of oxygen after the measurement (1) the calculated carbon content at the end point within the permissible depending on the desired steel grade

409625/0847

. ".". · 236U20

Range is' (i.e. according to type (a) in Pig. 1), (2) the calculated Carbon content at the end point is predicted to be excessively high (corresponding to type (b) in Mg. 1, where the Introduction of a coolant is required), and (3) the calculated carbon content at the endpoint as being excessively low "is predetermined (corresponding to type (c) in FIG." 1, where easy inflation - i.e. with low pressure required is), whereupon the control system reacts according to the

temporary determination can take place «,

According to the invention, the heating ^{factor A (t χ 0} G / Nm ^ oxygen) is defined as follows:

W ₁₁ . . AT

where mean:

the amount of blown oxygen to increase the temperature to an estimated value after measurement (only),

m is the weight of the total batch (in t); the temperature rise after the measurement ( ⁰ G) ₀

The predicted heating factor, as well as the target end point temperature, are calculated from the following Equation determines:

where mean:

A ¹ the prediction heating ^factor (t p0 C / E [m ^ oxygen)

⁰ C / E [m ^

Eq is the calorie content of the initial batch (Kcal)

E-o the calorie content of the batch at the time of measurement (Kcal)

E-g. the target or target calorie content of the batch on End point (Kcal)

Ε-, the calorie loss between the measurement and the End point (Kcal)

AWp is the amount of decarburization (t)

^ Wj, the amount of oxidized molten iron (t) _o

The amount of oxygen blown in to increase the temperature to an estimated value after the measurement is thus used calculated using the following equation:

(2)

Assuming that there is a relationship between the decarburization rate and the carbon content according to Mg ₀ 3, the decarburization rate results from the following equation:

. _{exp (} .

where mean: '

ν = the rate of decarburization (kgC / Nnr oxygen)

Wg ₁ = the weight of the molten steel (kg) Q = the integral or whole amount of oxygen (Fm)

40Ö82B / 08A7

= the carbon content

the decarburization speed during the period of maximum decarburization (kgO / Um oxygen)

a curve parameter

the carbon content at critical decarburization

The terms V, Op and O ^ are used here as decarburization parameters designated.

Furthermore, assuming that

0-g is the carbon content at the time of measurement. (in 1o) ■

⁰ EA the target or target coal content-at the end point (in 1 »)

mean, using equation (3), get the following equation:

AQ = -

^a > ^W ST ° 1OO ^; V {i-exp (- P ^ ⁰ J

100 V

1n

exp (

⁰ B " ⁰ O

Therefore:

⁰ EG = ^c o ^{+ O} P ^e1n L ¹⁺ l ^ex P (

⁰ B - ⁰ O,

, exp

100V

w _ST .c _p

825/0847

where E _{EG means} the calculated carbon content (in $) at the end point «. Of the decarburization parameters, C _{Q is} a constant based on determining actual results from previous operations, while V and Op can be determined experimentally as functions of fresh conditions. Therefore, when the carbon content Cg is measured during the blowing operation, the calculated carbon content C-gβ at the end point can be determined. The control is determined according to the difference between the calculated carbon content at the end point and the intended target carbon content.

According to the invention, the required raw materials are prepared in such a way that that the temperature of the steel melt at the end point is slightly higher than the target temperature at the end point, because if the measurement results of the sensor indicate the slight inflation, the time span from the measurement by means of the ihler to End point is 2-3 min, which of course limits the effects of slight inflation »For this Reason, the melt temperature is kept a little higher at the beginning of the initial inflation, and so the raw materials become prepared that a slightly higher temperature than the target temperature at the end point is achieved at the end point, so that the correct temperature and carbon content at the end point can be achieved even with a slight inflation is applied «, In addition, the temperature and carbon content of the molten steel after the completion of the inflation corresponding to the amount of oxygen required to achieve a predetermined molten steel carbon content the desired carbon content of the steel to be produced is measured, as firstly the temperature rise of the steel melt varies even with the same amount of inflated oxygen, when the steel melt composition is not constant at the time of measurement, so that the determination accuracy of Temperature at the end point is affected when taking measurements

409825/0847

do not come together with practically the same molten steel composition be carried out, and secondly because a period of time of 2-3 min is required for the effective lance effect when inflating slightly. That with the control according to the invention The coolant used can be of the usual type and consist, for example, of scrap.

The following are preferred embodiments of the invention explained in more detail with the aid of the attached drawing.

Figo Ta, 1b and 1c three different regulation or control schemes according to the temperature and the carbon content the steel melt at the end point,

long. 2 shows a timing diagram of an exemplary control system for Carrying out the method according to the invention,

Pig. 3 is a graph showing the relationship between the rate of decarburization and the carbon content and

4a and 4b graphical representations of the recovery processes as well as the temperature and the carbon content accuracy in successive operating processes of a converter according to the method according to the invention.

The symbols according to Fig. 1 have the following meanings:

= the amount of oxygen blown in to increase the Temperature to an estimated value after the measurement; .

= the amount of oxygen to be injected at the end point; = the temperature at the time of reading;

40 98 2S / ÖS4 7

L · = carbon content at the time of measurement; = the target temperature;

⁰ EA ^{= the}
The numbers in Fig. 2 indicate the following:

1 = final temperature of pig iron

2 = heat compensation calculation

3 = raw material display

.4 = 8 min interruption after the onset of blowing

5 = data verification

6 = data error indication

7 = Calculation of the amount of oxygen for inserting the sensor

8 = oxygen quantity display

9 = steel clay temperature interruption

10 = liquidus temperature interruption

11 = calculation of carbon content according to calibration curve

12 = measuring temperature and carbon content display

13 = Calculation of the heating factor and the decarburization parameter

meters

14 = determination of type a, b or c

15 = Calculation of the amount of oxygen, the amount of coolant

and the light blow scheme at the end point

16 = Display of the amount of oxygen, the amount of coolant

and the light blow scheme at the end point

17 = interruption every 40 ETm

18 = Calculation of temperature rise and decarburization

19 = display of the calculated temperature and the calculated Carbon content

20 = temperature interruption at the end point

21 = heating factor rounding to simplify the calculation

22 = carbon content — break at end point

23 = rounding of decarburization parameters to simplify the

calculation

409826 / ΟβΌ

Note 1: The measuring times of the steel melt temperature and the liquidus temperature will be automatically through routinely provided display devices are displayed.

Note 2: The deviation rounding values for the heating factor and the decarburization parameters are-after Setting tables adjustable. ·

The method according to the invention is carried out by the rule Control system carried out according to FIG. 2, the very precise control of the temperature and the carbon content of the Steel melt guaranteed at the end point «

The following example is the application of the invention Procedure explained in more detail:

A converter was charged with a charge of 82.8 t of molten pig iron at a temperature of 128O ⁰ C and with 18.7 t of scrap. Since the steel to be produced was a medium-carbon steel, an integral or total amount of oxygen of 4060 Nm was inflated according to calculation according to a static model, the temperature and the carbon content of the molten steel at this point in time being measured by means of a sensor or a probe. The measured values for melt ^{temperature and carbon content were 1584 °} C. and 0.46 _e

These values were in the control system of Mg ₀ 2 in excess · conformity processed with the previously-indicated equations, where the required regulation or control has been performed "With this operation, the amount of coolant (scrap) 520 entered kg, which after the measurement injected oxygen quantity 660 only (the whole, to the end point blown oxygen amount corresponded to 4720 NNR), the temperature at the end point of 1651 ⁰ C and the carbon content at the end point $ 0.09.

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In this example the target temperature and target carbon were content at the end point at 166 ° C or $ 0.10, so that both "the temperature and the carbon content are close to." corresponded to the setpoints.

FIGS. 4a and 4b illustrate an example of the results obtained when the simultaneous control (i.e., "h _o of temperature and carbon content) was applied by the inventive process successively on a number of heating or starting processes. The following table illustrates the control accuracy. '

TABEL Simultaneous temperature carbon content

χ - 0.4 ⁰ C $ 0.001 6 0.5 ⁰ C 0.0175%

Degree of match (accuracy) $ 81 $ 73 $ 63

Note: 1) Regarding the temperature, an accuracy of ± 10 ⁰ C was considered a good agreement «,

2) Concerning the carbon content, an accuracy was obtained of ± $ 0.02 considered a good match.

3) The simultaneous match refers to the pail, in which both the temperature and the carbon content reached the target values in the same batch «

4) The temperature range at the end point was 1600 - 169O ⁰ C.

-40982S / 0847

5) Per carbon content range at the end point was 0.08 ~ 0.18 # _o

6) χ «Average value of accuracy.

7) ό s normal deviation of accuracy. '

Due to the greater accuracy of the The following notable results result in a control or regulating effect Advantages: -.-.."

1. Since the carbon content of the steel melt can be regulated to the correct value, there is no danger for '

an abnormally high increase in the oxygen content in steel; there is also a reduction in non-metallic inclusions guaranteed, while a constant output of "ferro-alloys is also ensured"

2. By the simultaneous control of the steel melt temperature and the carbon content will result in a reduction

of reblowing and adding coolant after the end point ensured, which leads to an improvement in the efficiency and productivity of steelmaking.

When blowing · steel in an inflation oxygen converter are thus the temperature according to the method according to the invention and the carbon content of the molten steel at a predetermined point in time before the end point by means of a cooler or a probe, where according to the process = » The difference between a calculated carbon content at the end point and a target carbon content obtained by processing the measured values at the end point the amount of oxygen to be injected at the end point and the coolant requirement or the light blowing scheme, i.e. blowing with wind with low pressure, can be calculated to the temperature and the carbon content to regulate or control the molten steel at the end point at the same time. '

40982S / 0847

Claims (1)

-H- Pat en ti a η claims β method for controlling or regulating the temperature and the carbon content of a steel melt at the end point of freshening in an inflation oxygen converter, thereby characterized in that the raw materials are prepared in such a way that the temperature of the Melted steel at the end point reaches a value above the target temperature at the end point that the temperature and the carbon content of the molten steel by means of a single sensor or probe simultaneously after the Inflation of oxygen can be measured in an amount necessary to achieve a predetermined molten carbon content is calculated according to the desired carbon content of the steel to be produced that based on the readings of temperature and carbon content an anticipated heating or heating factor as well Decarburization parameters are calculated that derived from the expected heating factor, the amount of oxygen is to be blown after the measurement to increase the temperature up to an estimated value that based on the amount of oxygen after the measurement and the decarburization parameters a calculated carbon content is determined, and that the amount of oxygen to be injected at the end point, a required amount of coolant or the scheme of light blowing according to the difference between, the calculated carbon content at the end point and the target carbon content at the end point are calculated, whereby the temperature and the carbon content of the steel melt at the end point are regulated or controlled at the same time will. 2. The method according to claim 1, characterized in that that the time of use of the! 409Ö25 / 0847 the probe is chosen so that. its use takes place when such an amount of oxygen has been blown that the carbon content of the melt a reached a predetermined value in the range of 0.50 - T.00 $ corresponding to the desired carbon content of the steel to be produced, 3. Yerfahren nach'Anspruch 1, characterized by g e k e η η that a sensor or probe is used that simultaneously measures the temperature and able to measure the carbon content of the melt » 4. The method according to claim 1, characterized in that the expected or predetermined Heating factor is calculated using the following equation '= f (E, E _B , where mean: A ^{1 is} the prediction heating _{factor (t e} ° C / Nnr oxygen). E _{0 is} the calorie content of the initial batch (Kcal) E-g is the calorie content of the batch at the time of measurement (Kcal) the target * or _c target calorie content of the batch at the end point (Kcal) the calorie loss between the measurement and the end point (Kcal) the amount of decarburization (t) the amount of molten iron oxidized (t). 40982B / 0.8 47 A method according to claim 1, characterized in that the amount of oxygen to be injected to increase the temperature up to an estimated Value after the measurement at which the temperature at the end point coincides with the target temperature at the end point or «, matches, according to the equation is calculated in which AQ β the amount of oxygen blown in (in Nur) for Increasing the temperature to an estimated value after the measurement, Wm ^{s is} the weight of the total batch (in t) and ΔΤ - the temperature rise after the measurement (in ⁰ C) Method according to claim 1, characterized in that the decarburization rate according to the following equation G χ it is determined in which ν = the rate of decarburization (kgO / flinr Oxygen) Wgij, = the weight of the molten steel (kg) Q α the integral or whole amount of oxygen (Nnr) ' O * the carbon content 409825/0847 Decarburization parameters: = the decarburization speed during the Period of maximum decarburization (kgO / lJnr Sauer material) · = a curve parameter = the carbon content in the case of critical decarburization
"mean. 7. - The method according to claim 1, characterized geke η η ζ eich net that the calculated carbon content at the end point of blowing using the equation = C ₀ It is determined in which G z = the "calculated carbon content at the end» point (in <fi) ' Oq, Op, V = decarburization parameters, AQ = the amount of oxygen blown in to increase the temperature to an estimated value of measurement (in ninr) and GQ = the carbon content at the time of measurement (in Jl) ■ - - mean. 40982S / Ö847 Blank page