JPH0441611A - Method for controlling end point of blowing in top and bottom-blown converter - Google Patents

Abstract

PURPOSE:To inexpensively control the carbon content, phosphorus content and temp. at the end point with high precision by measuring the carbon content and temp. of steel at the end point of blowing by a sublance in a top and bottom-blown converter and calculating the requisite amts. of the oxygen and cold charge to be blown to obtain the target carbon content, phosphorus content and temp. from a specified relational expression. CONSTITUTION:The oxygen consuming rate and heating rate are previously expressed by the polynominal of the carbon concn. in steel based on the actual results in consideration of variable blowing factors in the operation of a top and bottom-blown converter, and a relational expression between the carbon content at the end point through the oxygen content at the end point from the actual blowing results in the past is prepared. The requisite amts. of the oxygen and cold charge to be blown from the measurement by a sublance to the end point of blowing are calculated from the carbon content Cs and temp. Ts of molten steel measured by the sublance at the end of blowing, polynominal and relational expression, and the operation is carried out based on the calculation results.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for controlling the end point of blowing in the dynamic control of a converter, particularly for controlling the carbon content, phosphorus content, and molten copper temperature at the end point of refining using a top-bottom blowing converter. This invention relates to a blowing control method for controlling the amount of oxygen and coolant by adjusting the amount of oxygen and coolant.

(Prior Art) Even in conventional top-blown converter blowing, the biggest challenge is to make the end point molten steel carbon content, phosphorus content, and temperature consistent with target values. Therefore, Guinaminok end-point control was developed to measure the flow rate and component analysis of the converter exhaust gas during blowing, or to measure the molten copper temperature and carbon content in the steel by sublance, and modify the blowing conditions based on the measurements. There is. For example, there are the following methods.

(1) A method (specially (No. 54842, 1983).

(2) Starting from the measured values of the molten copper temperature and carbon content at any point during blowing, the flue gas flow rate and flue gas analysis values measured from time to time, the oxygen supply amount, and the molten steel temperature from the gas generated from the auxiliary raw materials in the furnace The change in carbon content, the change in the amount of oxygen in the slag, and the change in the amount of oxygen in the slag are determined, and compared with the locus estimated from the equation for each change that has been determined in advance, control is performed to reduce the difference between the two, and the end point target is determined. The amount of blown oxygen required for the temperature and carbon content,
A method for estimating the amount of cold material thrown and performing lance operation (Unexamined Japanese Patent Publication No. 5
No. 8-56002).

(3) Secondary combustion obtained by measuring the concentrations of co, co□, and N2 in the exhaust gas during converter blowing, and calculating the secondary combustion efficiency of CO in the converter based on the measured values. A method of comparing the efficiency with a standard secondary combustion efficiency determined in advance and adjusting the amount of refrigerant and the amount of oxygen supplied according to the deviation (Japanese Patent Laid-Open No. 62-224623).

(4) During the blowing period, when the molten steel carbon concentration is 0.1% or more, measure the molten steel carbon with a sublance, estimate the oxygen concentration from that value, and calculate the oxygen concentration of the molten steel from the amount of oxygen blown until the end of the blowing. Converter blowing control method for estimating the oxygen concentration of molten steel at the end point of blowing from the increment Δ[0] (Japanese Patent Application Laid-Open No. 62-56511)
.

(Problems to be Solved by the Invention) However, these conventional methods have drawbacks such as problems in control accuracy and expensive equipment required for control. Especially when applied to upper and lower blowing furnaces, accuracy was a problem.

That is, in the methods (1) and (4) in the previous section, the control accuracy may be lowered because the bottom blowing amount and the fluctuations in the lance action at the end of blowing are not taken into consideration.

Similarly, methods (2) and (3) provide good control accuracy, but require high equipment investment due to component analysis of the exhaust gas.

Thus, an object of the present invention is to provide a method for controlling the end point in a top-bottom blowing converter, which is inexpensive and highly accurate in controlling the end point carbon content, phosphorus content, and temperature.

(Means for Solving the Problems) The inventors of the present invention have conducted various studies to achieve the above object, and have focused on the method (1) above, further introduced a temperature increase rate equation, and further introduced an end-point oxygen amount. By correlating the relational expression between and the end point carbon concentration and the end point oxygen amount and the end point fia degree, the oxygen supply amount and the amount of six materials input are controlled based on the measured data of the melt W4 temperature and carbon content. He realized that it was effective to do so, and completed the present invention.

Here, the gist of the present invention is to reduce the carbon content (
Cs) and steel temperature (Ts), and based on the oxygen consumption rate formula and temperature increase rate formula, which were established based on operating results and taking into account blowing fluctuation factors, and the relationship between the end point oxygen cap and the end point carbon concentration. The required amount of blown oxygen and amount of coolant to reach the target carbon content, phosphorus content, and temperature at the end of blowing are calculated from the equation and the relational expression between the end point oxygen amount and end point phosphorus concentration, and based on this calculation result. This is a method for controlling the end point of blowing in a top-bottom blowing converter, which is characterized by operating the converter based on this method.

Note that the above-mentioned final stage of blowing does not have a particular IQ limit, but generally refers to the period of \5 minutes until the end of blowing.

According to Mr. B, the control method of the present invention is that, in the operation of a top-bottom blowing converter, the oxygen consumption rate and temperature increase rate at the end of blowing are expressed by a multiple expression of the carbon concentration in the steel, and the polynomial and Based on the carbon content C3 in the steel and the molten steel temperature T obtained by sublance measurement at an appropriate time before the end point of blowing, the amount of oxygen blown in Δo2 and the temperature value Δd2 and the period from that point to the end point of blowing. Including the amount of coolant injected into the molten steel ~ 6L, the carbon content in the steel at the end of blowing C4, scrubbing, blowing mixture ratio, sublance measurement temperature at the end of blowing, bottom blowing gas flow rate, lance surface distance. , an equation expressing the correlation between these variables using the amount of the input solvent as a factor was obtained, and the temperature of the carbon in the wire and the molten steel obtained by sub-lancing measurements at an appropriate point before the end of predicted blowing for each blowing was calculated. ] Marked carbon-containing IC4 and eyes +! Given the temperature 'I', the required blown oxygen cap and the required coating material cap from the time of sublance measurement to the blowing end point are calculated from the above correlation formula, and the operation is performed based on the calculation results. be.

In addition, a correlation formula between the end point carbon content and the end point phosphorus content is created using the end point oxygen content based on past blowing results, and the target end point carbon content is corrected from the target end point phosphorus content. The content may also be controlled.

(Operation) Next, the present invention will be described in more detail with reference to the accompanying drawings.

First, the blowing control method of the present invention is shown in a flowchart in FIG.

As will be clear from this, according to the present invention, a dynamic control formula (oxygen consumption rate formula and temperature increase rate formula) is determined in advance, and on the other hand, a relational formula between end point oxygen and end point carbon concentration, end point oxygen and end point Find the relational expression for each with the phosphorus concentration.

dO□/IAit The oxygen consumption rate at the end of blowing is expressed as dC in the following formula: Sea urchin.

LL dC Nikode C: Carbon content in steel W (wt%), 1t: Weight of molten steel (1) From carbon content Cs in steel at the time of sublance measurement), carbon content in steel C4 (I) at the end of blowing. ), the basic unit F11 (N-2/T) required for decarburization is Fe(Cs,C
I) ”' an(Cs −Ci)+a+log(Cs/CE)”
' (2) From equation (2), past blowing performance data Fo, Cs, and C1 are substituted to determine the optimal values of ao and a. Next, the relational expression with the operational factors is quantified as shown below (approximated by a linear expression of factor change).

Fe (Cs, Ct) -Fo' (C5, CI) +Σ
hot (xi xtm) + Fmo ... (3) where F.: Oxygen consumption after Sarans measurement (here, the amount of oxygen supplied by cypress wood etc. is added) X3: Blowing factor variable Xrk: Blowing factor Variable reference value Pa' (Cs, Ct): This is the value obtained by substituting 80, a, into the right side of equation (2).

Fso is a constant based on the past 40 charges.

The blowing factor variables here are the distance between the lance hot water surfaces, the molten steel temperature at the time of sub-lance measurement, and the converted C input before and during blowing.
The aO amount, bottom blowing gas flow rate, and cold pig heavy cold iron ratio were adopted.

By substituting the actual data into 2(3), the optimum value of the influence coefficient 11of is determined.

T Similarly, set the temperature increase rate □ as in the following equation, dC to dC Here, T: hot metal temperature ~.

Integrating from the carbon content in steel C5 (g) at the time of sublancing measurement to the carbon content in steel C4 (g) at the end of blowing, the temperature increase Δ
T is hT = (Tt Ts) = bo(Cs Ci)
10b+log(Cs/c,) HH+ (5). Equation (5) contains blowing performance data ΔT, C,,C.

, and determine the optimal values of bo and b. Next, the relational expression with the operational factors is quantified as shown below (same as Equation (3)).

hT (TETs) - ΔT' (Cs, CE) +Σ
hyi (x, x;k) +FB?・ ・
・(b) ΔT: Amount of temperature increase after sublance measurement■ (Adding the temperature decrease due to the addition of cypress wood) 8T"; This is the value obtained by substituting bo and bl into the right side of equation (5). .

FIT is a constant based on the past 40 charges.

hT, is the influence coefficient.

The blowing factor variables used were the lance surface distance, the molten steel temperature at the time of sublance measurement, the equivalent amount of CaO introduced before and during blowing, the bottom blowing gas flow rate, and the cold pig iron + cold iron ratio.

The optimum value of the influence coefficient hTi is determined by substituting the actual data into equation (6).

By the way, the end point target carbon content (CT R
, end point target phosphorus content (P'rt), end point target temperature (T
T is fixed. Therefore, in the control method according to the present invention, the end point target phosphorus content is converted into the end point carbon content via the end point oxygen concentration.

That is, the end point phosphorus concentration PE and the end point carbon content are
E has a relationship between the end point temperature TI and the end point oxygen concentration OE.

log CP t) = d+ (mixed pig iron ratio) 10 dz (
1/(TE+273))d3 log (Of) +d
4(Input 5iOz(K/T))+ds(In
put Ca0(X/T)) +da ClnputM
gO(K/T)) +dq [Input P(K/T)
)) +d@(Input Mn(K/T)) +d
q (InputTi(K/T)) +d+o ・
・ ・(8) Here, the mixed pig iron ratio - (molten pig iron amount, cold pig iron amount) / (
Input Sing: 5 of the auxiliary raw materials input during blowing
in2 consumption rate Hot metal [Si] x60/28 Medium [P) amount x mixed pig iron ratio Inp
ut Mn: Input n unit of auxiliary raw material input during blowing 10 in hot metal [-〇] X mixed pig iron ratio Input Ti: Amount of (Ti) in hot metal Also C0 to C6 and d, to d,. is recalculated every charge using the value obtained through multiple regression based on the data of the most recent 100 charge blowing results. Therefore, at the time of sublance measurement at the end of blowing, the target phosphorus amount (P
yt) to calculate the required end point carbon content C11.

C here! If TF≦CUT, modify the final target carbon content as 7-GETP.

Next, based on the molten steel carbon content C3 and the molten steel concentration T measured by the sublance, first Ts
, C-, Ctr, and find TE.

Here, ■ If T E > T E T, an instruction is given to add coating material such as scale or iron ore.

For example, scale input amount (Wnysc) = (TE
To) Xo, 250 ・ ・ (9) Iron ore input amount (Lyr.) = (TE Ttt) X O, 167 ・ ・ 0
0).

If the amount of scale input is 10 kg/or more, the remaining amount is input as iron ore. Next, the required top-blowing oxygen amount F 6V is obtained by subtracting the oxygen amount in the scale iron ore from equation (3).
Calculate.

F 6v=FO(Cm, GET) 16yicX0.
15-a. Xo, 20 ... θ0 also ■T
In the case of E=Ttr, the required top-blowing oxygen amount Fov is calculated from equation (3) in the same manner as above without issuing an instruction to insert the electrical material.

Fov= Fo(Cs, C1t)...0
2) Also, if TE < T IT, then TE in equation (6)
Substituting T, T3, and C3, the final target carbon concentration CUT is revised again.

Next, using the obtained GET, the required top blowing oxygen amount Fov
is calculated using equation (3).

Fov-Fo(Cs,C,,)...03)
Based on the amount of mixed material input and the required amount of top-blowing oxygen thus obtained, the blowing is completed.

At the same time as blowing ends, the end point temperature and end point carbon content are measured using a sublance, and the F No. and FI of formulas (3) and (6) are measured.
Update T and perform the next blowing training.

(Example) Next, an example of a 250-ton vertical blowing converter furnace using the control method according to the present invention will be shown.

First, oxygen consumption rate and temperature increase rate equations (2), (3),
The optimum values for each of the coefficients (5) and (6) were determined based on the actual results of 150 charges, and the results were as shown in Table 1.

Table 1 Dynamic control influence coefficient log [PE] = d + (χ mixed pig iron ratio] + dz
[1/ (T÷273)] +d:+log[oE(
ppm)]+d411nput SiO□] ′k”+
d5[rnput Cab) +k”+da[Input
t Mg01 ””+d, 1lnput Pi ””+
d, [Input Mn] ””'+dq[Input
Til""+d+o'・"(8)'The offline blowing calculation results based on the above coefficients are shown in Figure 2 (
As shown in a) and (b), the oxygen consumption rate is ±1.
The simultaneous success rate was 83.6%, with 9.38% within ONI/T and 85.7% within ±12°C of temperature.

In addition, the relationship between the end point carbon content, end point phosphorus content, and end point oxygen concentration was as follows.
, (b), respectively. Furthermore, the continuous accuracy of [C] and molten steel temperature when blowing is controlled based on these coefficients are shown in FIGS. 4(a) and 4(b), respectively. End point rcI series 88.2% within ±0.02%, temperature series 83.6% within ±12°C, simultaneous series 80.2
%Met.

As is clear from the above, the blowing control method according to the present invention makes it possible to achieve an inexpensive and highly accurate blowing process, and the need for additional processing during tapping is greatly reduced.

(Effects of the invention) The method of the present invention can control the blowing end point, carbon content, phosphorus content, and temperature at low cost and with high precision, and there is little need for prevention of component separation, reblowing, and additional cooling work. This greatly contributes to improving production efficiency, improving quality, and reducing the unit consumption of refractories.

The various calculations in the method of the present invention can be performed automatically by having a process control computer perform them, and by providing this computer with functions for automatically adding a mixture material and automatically stopping oxygen supply.

[Brief explanation of drawings]

FIG. 1 is a flowchart of the blowing control method of the present invention. FIGS. 2(a) and (bl) are graphs showing actual values and estimated values based on the method of the present invention for the oxygen consumption unit and temperature rise from the time of sublance measurement to the end point, respectively. FIG. 3(a), 0)) are respectively [CI
and [Pi] is a graph showing the analytical values and the estimated values according to the method of the present invention. FIGS. 4(a) and (b) show the [CI
and? 8 is a graph showing the measured value (sublance) of the steel temperature and the Guinaminoku end point target value.

Claims (1)

[Claims] The carbon content (C_s) and temperature (T_s) in the steel are measured by a sub-lance at the end of blowing in a top-bottom blowing converter, and the oxygen consumption rate formula is established based on operating results, taking into account blowing fluctuation factors. The target carbon content, phosphorus content, and temperature at the end of blowing can be arrived at from the equation of temperature increase rate, the relation between the end point oxygen amount and the end point carbon concentration, and the relation between the end point oxygen amount and end point phosphorus concentration. A blowing end point control method in a top-bottom blowing converter, characterized in that the required amount of blown oxygen and the required amount of coolant are calculated, and the converter is operated based on the calculation results.