JPS5941409A - Control of blowing - Google Patents

Abstract

PURPOSE:To improve the quality and yield rate of steel, by detecting the level of slag and a slag-forming condition using a microwave slag level meter, and maintaining these values under standard conditions. CONSTITUTION:Microwaves are projected from a microwave generator 20 to the surface of slag in a converter furnace 1. The microwaves reflected from the surface of slag are received by an antenna 5 constituting a microwave slag level meter, and th frequency of mixed waves comprising projected and reflected waves and/or the reflection ratio of the microwaves on the surface of slag is calculated. Thereafter, the level of slag and a slag-forming condition is detected on the basis of said calculated values. By controlling elements having effects on these values, the level of slag and the slag-forming condition are maintained under predetermined standard conditions. Thus, the quality and the yield rate of steel are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blowing control method for controlling the settings of, for example, the amount of oxygen fed, the height of the lance, the amount of auxiliary material input, etc., based on furnace condition data detected using a microwave slag level meter. It is something.

Blowing in a converter involves, for example, spraying pure oxygen gas onto molten steel from a lance inserted through the mouth of the converter to decarburize the molten steel while agitating it, or to cause film removal and desulfurization reactions. By the way, maintenance of an appropriate slag level and slag slag status is an important management item for stable blowing operations. Abnormal slag levels are a sign of so-called slopping, in which slag foams and blows out of the furnace mouth.Failure to form slag slag affects the progress of descaling and desulfurization, both of which affect steelmaking. is known to have a significant impact on component quality and yield. For this reason, various methods for detecting the slag level and the state of slag slag have been proposed and put into practice.

For example, as a method for detecting the slag level, there is a method of detecting the sound of a specific frequency in the converter, detecting the forming state of the slag by analyzing the level, and predicting the slag level accordingly (Japanese Patent Laid-Open No. 55 -15451
No. 7). However, this method has problems such as low detection accuracy because the sound source position and intensity change, and the relationship between slag 7 ohming and acoustics is low.In addition, Sublance is a method for detecting slag slag conditions. A method of sampling slag intermittently during the blowing period and analyzing the concentration of each component in the slag, especially the concentration of FeO, to detect the slag condition, or detecting the vibration of the lance during blowing and detecting the slag condition. There is a method of indirectly detecting the slag formation situation by capturing kinetic energy as vibration energy of the lance. However, in the former case, these methods can only obtain indirect data, and it takes time to collect and analyze the sample, resulting in a significant time delay in the detection data.On the other hand, in the latter case, indirect detection method, the detection accuracy is low;
Further, when the amount of slag is small, the lance and slag do not come into contact with each other, making detection impossible.

The present inventors conducted experiments and research on methods for detecting the slag level and slag slag formation during the blowing process as described above. As a result, the microwaves reflected from the slag surface were The frequency and slag level of the beat wave (hereinafter referred to as mixed wave) generated by mixing the projected microwave wave and the reflected wave, as well as the microwave reflectance from the slag surface, the slag level, and the slag slag condition, and We found that there is a close relationship with the occurrence of slopping. Incidentally, the relationship between the frequency of the mixed wave and the slag level is shown in FIG. 1 (a), and the relationship between the microwave reflectance and the state of slag formation is as shown in FIG. 1 (b). The graph shown in FIG. 1(a) shows the frequency (Hz) on the horizontal axis and the slug level on the vertical axis, and as is clear from this graph, the existence of a certain proportional relationship is recognized. In addition, the graph shown in Figure 1 (b) shows the microwave reflectance on the horizontal axis and the T-Fe concentration in the slag used to evaluate slag slag formation on the vertical axis. It is recognized that there is a certain negative correlation. This is considered to be due to the fact that the degree of attenuation of reflected waves becomes large in slag with a high microwave reflectance of TeFe, that is, in a good slag state. Note that this microwave reflectance also has a certain relationship with the slag level, as shown in FIG. 1(c).

The graph in Figure 1 (C) shows the blowing time on the horizontal axis, the slag level (C) on one side on the vertical axis, and the microwave reflectance (relative value) on the other side. The solid line in the graph shows the slag level, and the broken line shows the microwave reflectance. As is clear from this graph, the microwave reflectance has a reciprocal relationship with the slag level, and the microwave reflectance is determined by the slag slag formation state and the slag level from the graphs shown in Figures 1 (b) and (c). It is recognized that a predetermined relationship is shown with the level. The occurrence of slopping, which is one of the main purposes of slag level detection, has a close relationship with the slag level and microwave reflectance, as shown empirically in FIG. The graph shown in Figure 1) shows the microwave reflectance on the horizontal axis and the detected slag level based on the mixed wave frequency on the vertical axis.The shaded area in the graph is slopping. This is the area of occurrence.

The present invention has been made based on such knowledge, and its purpose is to improve the mixed wave frequency of the projected wave and the reflected wave when microwaves are projected onto the slag surface using microwaves. In addition, the microwave reflectance is detected, and based on this detection data, the slag level and slag slag formation status are detected, and the occurrence of slag is predicted, sedatives are added to prevent slopping, lance height is adjusted, and the amount of oxygen is sent. It is an object of the present invention to provide a blowing control method that allows accurate and rapid adjustment and further control of settings such as the timing and amount of slag injection.

The blowing control method according to the present invention projects microwaves onto the slag surface in a converter, captures the microwaves reflected from the slag surface, and determines the frequency of the mixed wave of the projected waves and reflected waves and/or the slag surface. Calculate the microwave reflectance at
It is characterized in that the setting side controls these influencing factors in order to maintain the slag level and the slag slag condition at a predetermined reference state.

First, the principle of the blowing control method according to the present invention will be explained below.

Detection of the slag level based on the mixed wave frequency of the microwave projected onto the slag surface and the reflected wave from the microwave is performed as follows. That is, there exists a relationship between the two as shown in FIG. 1(a), which can be expressed as the following equation (1), and the slag level can be detected using this equation.

However, fb: Mixed wave frequency (Hz) L: Distance between the furnace mouth and the slag surface fo = Frequency change rate (Hz/sec) C: Microwave propagation velocity (3 x 10" m/sec) Regarding this slag level, the first As shown in Figure (c), there is a close relationship with the microwave reflectance, and although it is not specifically shown, it is presumed that it can be easily determined by multiplying the microwave reflectance by a predetermined coefficient.

Next, the state of slag slag formation based on the microwave reflectance is detected as follows. First, the microwave reflectance is expressed by the following equation (2) when the microwave u1 projected onto the object is expressed as the equation (3) below, and the relative value u 2 / u 1 given as.

ul = Ulcos (ω1t)
”・(21 However, U = amplitude ω□: angular frequency t: time J = U, cos (ω2t)
-(31 However, U2: Amplitude ω2: Angular frequency The microwave reflectance given as above is shown in Fig. 1 (
As shown in b), T in the slag indicates the state of slag slag.
-There is a predetermined relationship with the Fe concentration, therefore, the correspondence between the two is determined in advance, and the quality of the slag slag formation status can be judged from the reference value of the microwave reflectance (shown by the dashed line in Figure 1 (b)). The determination may be made based on whether or not it decreases. Furthermore, as shown in Figure 1, the occurrence of slopping can be determined by setting predetermined limit values for the slag level and microwave reflectance, respectively, and determining whether or not both exceed the limit values. .

Therefore, in a steady state, the lance height, auxiliary material input, oxygen supply amount, etc. are controlled based on the standard turn with time changes due to the blowing time determined empirically in advance, and the When an abnormality occurs in the slag level or slag slag condition,
In addition, when the slopping occurrence condition is reached, until the steady state is restored, the operator manually monitors the display etc., or as in the above embodiment, automatically adjusts each influencing factor. For example, adjusting lance height, oxygen supply amount, auxiliary raw materials,
It is only necessary to control settings such as the amount of sludge-forming agent, etc., and the timing of the addition.

The specific configuration for carrying out the method of the present invention will be described below. FIG. 2 is a schematic diagram showing the state of implementation of the present invention, in which 1 indicates a converter, 2 a hood for collecting waste gas, and 3 a lance for blowing oxygen, etc. The lance 3 is inserted into the converter 1 from the furnace mouth 1a through the hood 2, and its tip is positioned within the slag 1b in the converter 1, so as to blow oxygen into the slag 1b and the molten steel IC below it. It has become.

An antenna 5 constituting a microwave slag level meter 4 is installed in the door 2 on the converter 1 at a position facing the converter mouth 1a. Antenna 5 is a water cooling jacket)
5a, and is connected to the microwave generator 20 and the signal processing device 30 via a waveguide and microwave circuit 10 (not shown), and is connected to the microwave oscillator device 20.
The antenna 5 projects microwaves toward the slag surface in the converter 1 using microwave signals from the converter 1, and receives microwaves reflected from the slag.

FIG. 2 is a block diagram showing the electric circuit system of the microwave circuit 10, the microwave generation circuit 20, and the signal processing device 30. In response to the modulation signal from the frequency modulator 22, the microwave oscillator 21 operates at an angular frequency of ω1. (ω1/2π=1~
A microwave signal of about 1000GH2) is output, and this microwave signal is transmitted to the magic Tll of the microwave circuit 10.
and is given to the antenna 5 via the circulator 12,
Microwaves are emitted from the antenna 5. The reflected wave from the slug 3 is received by the antenna 5, and the microwave signal related to this reflected wave is input to the circulator 12 of the microwave circuit 10. The microwave circuit 10 is configured to be able to capture weak reflected wave signals with high sensitivity, and includes a magic Tll, a circulator 12. It consists of a bridge circuit including a mixer 13 and a variable attenuator 14. The projected wave signal and the reflected wave signal are mixed in the mixer 13, and the mixed wave signal is input to the preamplifier 31 of the signal processing device 3o. The mixed wave signal is amplified by the preamplifier 31 and then input to the filter 32, as well as to the frequency detection circuit 35, which detects the frequency of the mixed wave and outputs the detected frequency signal. The signal is output to the control circuit 6.

On the other hand, the mixed wave signal inputted to the filter 32 is inputted to the waveform shaping circuit 33 after the DC component, ie, %(Uτ+UH), etc. is removed. The waveform shaping circuit 33 also receives a microwave modulation signal from the modulation oscillator 22, and the mixed wave signal is rectified by the waveform shaping circuit 33.
In addition to outputting and recording the smoothed voltage corresponding to the amplitude U,, U, to the recorder 34, the reflectance detection circuit 36
will be appearing in

The reflectance detection circuit 36 detects that the amplitude voltage of the mixed wave signal is the reflectance K.
The reflectance K of the microwave slug is detected using the fact that it is proportional to , and this detected data is output to the control circuit 6.

The reason why this reflectance K can be understood as a voltage proportional to the amplitude of the mixed wave is that the mixed wave P is expressed as follows from the projected wave u1 and the reflected wave u2, and P = 'A
(U”1 + U: + 2UIU2cos (ω+
-ωz) t) When the amplitude U1 of the projected wave u1 is constant, the amplitude U and U2 of the mixed wave P are the amplitude U2 of the reflected wave u2.
This is because the reflectance corresponds to the amplitude of the mixed wave P.

The control circuit 6 uses the frequency fb of the mixed wave input from the same wave number detection circuit 35 and the frequency change rate (H
z 7 seconds), based on the microwave propagation velocity C (1) above.
The slag level L is calculated according to the formula, and this is displayed on the display 7n.
In addition to outputting this to the upper limit value Lu and lower limit value Ld of the slug level that have been input in advance, Ld≦L≦Lu
determine whether or not the condition is satisfied, and when the slag level L exceeds the condition, cause the display 7n to display a warning;
It is also a slug level influencing element that issues a signal to generate an alarm sound and makes the slug level /l/L between the upper and lower limit values. For example, control signals are output to the lance height setting device 7a, oxygen feeding amount setting device 7b, auxiliary material feeding amount setting device 70, etc. to control the lance height, the amount of oxygen fed, and the amount of auxiliary material input. There is.

The control circuit 6 also receives the microwave reflectance K input from the reflectance detection circuit 36 and the microwave reflectance K shown in FIG.
The state of slag slag formation is detected based on the data related to the T-Fe concentration in the slag as shown in , and this detected data is output to the display 7n, and also inputted in advance in relation to the blowing time. Compare the standard pattern of a certain slag slag situation to find the deviation, and when this deviation exceeds a certain level,
In order to eliminate the deviation, a control signal is output to the slag forming agent input amount setting device 7m in order to control factors that influence the slag slag formation status, such as the slag forming agent input amount.

Furthermore, the control circuit 6 controls the slag level L obtained in the above process.
and the microwave reflectance input from the reflectance detection circuit 36 are compared with the pre-input limit value for preventing slopping, and when both the slag level L1 microwave reflectance K exceed the limit value. directly determines that slopping has occurred, displays an alarm on the display 7n, and outputs a control signal to each setter 7a etc. to set and control the aforementioned slag level influencing factors.

Next, an example of blowing control by the method of the present invention will be explained using specific numerical values. The converter used as the target was 150);
/LD converter, which is used to control blowing in the process of melting high carbon ordinary steel, especially slopping prevention control, and Figure 4 shows the control pattern. . The graph in Figure 4 shows the blowing time (%) on the horizontal axis, the level relative to the furnace mouth on the vertical axis, and the amount of oxygen supplied (Nm3/min).
, the microwave reflectance (relative value) is taken and shown. In the graph, A is the slag level, B is the microwave reflectance, and Lu
, Ld are the upper and lower limits of the slag level, a is the lance height, b is the time when the auxiliary raw material (iron ore) is introduced, and C is the amount of oxygen fed. As is clear from this graph, the slag level L exceeds the slag level upper limit Lu in the early and middle stages of blowing, but on the other hand, in the early stage of blowing, by reducing the amount of oxygen supplied, , to lower the slag level and prevent slopping, and in the middle stage of blowing, add auxiliary raw materials to cool the slag, and reduce the slag c.

The removal of air bubbles was improved and the lance was raised to lower the slag level to prevent slopping. As a result of such blowing control, the frequency of occurrence of slopping was as shown in FIG.

FIG. 5 is a graph showing the frequency of slopping when the method of the present invention is applied, as described above, compared to when the conventional method is applied, and the horizontal axis shows the date of the test;
In addition, the vertical axis shows the slopping occurrence frequency index, and in the graph, the line connecting the black circle plot points shows the results of the method of the present invention, and the line connecting the white circle plot points shows the results of the conventional method. . As is clear from this graph, when the method of the present invention is used, the frequency of slopping occurrence is significantly reduced compared to when the conventional method is used.

The results of melting in this test are shown in Table 1.

Table 1 (unit: weight %) Note that the actual results in Table 1 above are before tapping in the LD converter. As is clear from Table 1, both the components and the temperature substantially matched the target values, indicating that the purification was carried out appropriately.

In the above control example, when the slag level exceeds the upper limit value, a configuration is shown in which different controls are performed separately in the early and middle stages of blowing, but this is not particularly limited. It is possible to determine in advance the influencing factors that can most effectively control the slag level and slag slag formation for each of various conditions, and to control the settings globally, selectively, or arbitrarily according to each condition. Of course. Further, the control may be performed automatically as described above, but it may also be performed manually according to each situation while the operator monitors the display 7n.

As described above, in the method of the present invention, microwaves are projected onto the slag surface, and the microwaves reflected from there are detected,
Based on this detection signal, the mixed wave frequency of the projected microwave and reflected microwave and the microwave reflectance from the slag surface are determined, and based on these calculated data, the slag level,
We decided to detect the slag slag formation status and set and control each influencing factor accordingly, so we could control lance height adjustment, oxygen supply amount adjustment, auxiliary raw material input, slag forming agent input, etc. in response to fluctuations in slag level. The present invention has excellent effects such as being able to perform this process accurately according to the furnace conditions, significantly reducing the occurrence of slopping, poor slag formation, etc., and improving steel quality and yield. be.

[Brief explanation of the drawing]

Figure 1 (a), (b), (c), and (b) show the mixed wave frequency, microwave reflectance, and slag level used in the method of the present invention.
A graph showing the relationship between the slag formation situation, slopping occurrence area, etc., FIG. 2 is a schematic diagram showing the implementation state of the method of the present invention,
Figure 3 is a block diagram of a control system implementing the method of the present invention, Figure 4 is a graph showing an example of slopping prevention control using the method of the present invention, and Figure 5 is a comparative test between the method of the present invention and the conventional method. It is a graph showing the results. 1... Converter 2... Hood 3... Lance 4.
-Microwave slag level meter 5...Antenna 6
...Control circuit 7a, 7b 111187m
- Setting device 1o... Microwave circuit 20...Microwave generator 30...Signal processing circuit Patent applicant Sumitomo Metal Industries Co., Ltd. Patent attorney Noboru Kono: Bicon J: Number of PL for l . (b) Micro crawling load resistance (8 vs. Peeru) (b) 1st Zubuki I Tochichima ('10) (c) My 70 reward Funago (4I! month?-) (d)

Claims (1)

[Claims] 1. Project microwaves onto the slag surface in the converter, capture the microwaves reflected from the slag surface, and calculate the frequency of the mixed wave of the projected wave and reflected wave and/or the microwave reflectance on the 727 surface. The blower is characterized in that the slag level and the slag slag formation condition are detected based on these calculated values, and these influencing factors are set and controlled in order to maintain the slag level and the slag slag formation condition at a predetermined reference state. Ren control method.