JPH0435528B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention suppresses the occurrence of slopping and spitting based on the amount and composition of fume dust generated by converter blowing, and also targets the molten steel composition at the end of blowing. The present invention relates to a method of controlling converter blowing conditions to match the composition.

[Prior art]

The important operational points in converter blowing are to improve the tapping yield by preventing the occurrence of slopping and spitting, the temperature of the molten steel at the end of blowing, the carbon content in the molten steel,
To make the components such as P and S match the target component values To accurately judge the slag formation during blowing necessary to achieve the above To achieve the above blowing to suppress the amount of loss of refractories in the furnace These include shortening the time and the time between the end of blowing and the time of steel tapping.

In view of these important points, usually at the end of blowing and before tapping, a sublance is inserted into the converter from above to sample the molten steel (sublance method), which is quickly analyzed to determine the molten steel composition. In addition, at the same time as the sublance is inserted into the furnace, the temperature of the molten steel is determined to determine the converter blowing status, and based on the results of this determination, the blowing conditions are changed and the blowing is terminated.

[Problem that the invention seeks to solve]

However, when using the sublance method, (a) the molten steel composition and temperature at the final stage of blowing are known, but they are unknown before then, and actions cannot be taken to satisfy the important points, and as a result, the important points cannot be adequately understood. (b) It is unclear about the continuous changes in the composition and temperature of molten steel. (c) Running costs are high. (d) The waiting time for analysis results is long, 2 to 5 minutes, and it takes a long time to take action based on the analysis results. C) There are drawbacks such as the inability to determine the slag formation status during blowing.

Furthermore, in addition to the control method using the sublance method described above, a method has also been reported in which control is performed by monitoring the slag formation state and determining the converter blowing state. For example, lance vibration method, acoustic method, radiometer method, etc. are available for monitoring the slag formation condition, and monitoring by these methods has the following drawbacks.

(b) The SN conversion was poor and a clear judgment could not be made. (b) It was not possible to quantitatively evaluate the reaction situation inside the converter.

In recent years, in order to stabilize converter operation and improve productivity, automatic blowing has been promoted using computers, and for this purpose, the converter blowing status can be accurately detected and the important points mentioned above can be determined based on the accurate detection of the converter blowing status. The blowing conditions that can satisfy the following conditions, specifically, the oxygen flow rate, lance height,
A method has been developed that can determine the flow rate of bottom-blown stirring gas, the amount of auxiliary raw materials, the amount of cold material to be added, and the timing of their addition.

[Means for solving problems]

The present invention was made in view of the above circumstances, and the amount of fume dust generated during converter blowing,
It is possible to understand the converter blowing situation, which has a certain relationship with the composition, and control the converter blowing situation based on this, to suppress the occurrence of slopping and spitting, improve the tapping yield, and also to prevent the blowing from ending. An object of the present invention is to provide a blowing control method for a converter that can make the molten steel composition match a target composition value.

A first method of controlling blowing of a converter according to the present invention is to measure the amount and composition of fume dust generated during converter blowing to determine whether or not slopping or spitting occurs, and based on the determination result, slopping or spitting occurs. It is characterized by controlling the lance height, acid flow rate, bottom blowing stirring gas flow rate, or amount of auxiliary raw material input in order to suppress the occurrence of spitting, and the second is that spitting occurs during converter blowing. The molten steel composition is estimated by measuring the amount and composition of fume dust, and based on the estimation results, in order to make the molten steel composition at the end of blowing match the target composition value, the lance height, oxygen flow rate, and bottom blowing stirring gas flow rate are determined. , the amount of auxiliary raw materials input or the time point at which blowing ends is controlled.

〔Example〕

The present invention will be specifically explained below based on the drawings.
FIG. 1 is a schematic diagram showing a state in which the present invention is applied to a top-blown converter in which stirring gas is blown from the bottom of the furnace, and numeral 1 in the figure indicates the top-blown converter. Top blowing converter 1
A lance 2 suspended from the base end is inserted into the furnace with the height of the tip inside the furnace controlled, and the lance 2
Oxygen gas with a controlled flow rate is sprayed from the tip of the furnace onto the molten steel 3 stored in the furnace. This spraying causes a flash point reaction and CO,
SiO ₂ , FeO, etc. are generated, and among them, SiO ₂ , FeO, etc. become constituent substances of the slag 4 existing on the molten steel 3 . In addition, due to the formation reaction of slag 4, the so-called slag formation reaction,
CaO, CaO.SiO ₂ , CaO.P ₂ O ₅ are generated, and CaO.P ₂ O ₅ , Fe, O, and CO are further generated by the slag metal reaction between the molten steel 3 and the slag 4.

The fume dust generated as described above is transferred to the converter 1.
The exhaust gas is sucked into an exhaust gas recovery device 5 having an inlet 5a above the furnace opening 1a, passes through a flue 5b following the inlet 5a, and is collected in a dust collector 5c. Dust collector 5 of flue 5b
A probe 6 is attached to the inlet 5a side with its tip positioned at the center of the cross section, and a suction tube 7 is connected to the proximal end of the probe 6. The suction side of the suction pump 8 is connected to the base end of the suction tube 7,
A discharge pipe 9 is connected to the discharge port of the suction pump 8, and the base end of the discharge pipe 9 communicates with the inside of the flue 5b.

A detection section 10 of a fume dust concentration measuring device 13, a detection section 11 of a fume dust analysis device 14, and a calibration sampler 12 are installed in order from the probe 6 side in the middle of the suction pipe 7, and the flue 5b sucked from the probe 6 The exhaust gas inside passes through the suction pipe 7 and the exhaust pipe 9 and returns to the flue 5b.

The fume dust concentration measuring device 13 is, for example, a light scattering type densitometer, and measures the fume dust concentration in the exhaust gas based on the signal detected by the detection unit 10, and outputs the measurement signal to the computer 15.

The fume dust analyzer 14 is, for example, a plasma emission spectrometer, and analyzes the composition of the fume dust based on the signal detected by the detection unit 11.
A signal related to the analysis value is output to the computer 15.

The calculator 15 receives signals regarding the oxygen supply flow rate, lance height, bottom blowing stirring gas flow rate, amount of auxiliary raw materials input, etc., and the calculator 15 receives these signals, the above-mentioned fume dust concentration value, and the analysis value of the fume dust composition. Based on the estimation and determination principle described below, the slag status is determined, the presence or absence of slopping and spitting is determined, and the P and S concentrations in the molten steel 3 are estimated, and the slag status is determined to be good. A control signal to suppress the occurrence of slopping and spitting, and a control signal to set P and S in the molten steel to target component values at the end of blowing are output to the converter control device 17. Converter control device 1
7 performs the control described below based on the input signal.

Next, the estimation, determination principle, and control content to be performed by the converter control device 17 will be explained.

(Estimation of slag formation status) Figure 2 shows the blowing time (minutes) on the horizontal axis, and the concentration (%) and fume dust generation amount (g/m ³ ) on the vertical axis. CaO concentration in fume dust generated during blowing (×−×),
SiO ₂ concentration (×…×), MgO concentration (○−○), MnO
It is a graph showing changes in the concentration (○...○), the T/Fe concentration (●-●), and the amount of hume dust generated (●...●).

The ratio of the concentration of CaO and the concentration of SiO ₂ that changes in this way, that is, the basicity (=concentration of CaO/concentration of SiO ₂ ) changes with the thickness of the slag, as shown in Figure 3 (on the horizontal axis).
There is a uniquely defined relationship as shown in } where CaO/SiO ₂ is taken and the thickness of the slag (mm) is plotted on the vertical axis.

Therefore, the thickness of the slag, that is, the slag formation status, can be determined based on the analyzed CaO concentration and SiO ₂ concentration, and when the slag thickness is thin, the degree of slag formation can be increased by performing soft blowing. On the other hand, when the slag is thick, the degree of slag formation can be reduced by performing hard blowing. Further, when the thickness of the slag is thin, the degree of slag formation can be further increased by adding a slag forming agent, for example, an auxiliary raw material such as limestone or quicklime.

(Determination of slopping, etc.) Figure 4 is a graph showing the change in the amount of fume dust generated when sloping occurs during blowing, with the vertical axis representing the blowing time and the vertical axis representing the amount of fume dust generated. . As can be understood from this figure, the amount of fume dust generated changes greatly as the blowing time changes, and the amount of fume dust generated changes greatly in areas where sloping occurs (at A, B, C, and D in the figure). Although not shown in the figure, where spitting occurs, the amount of fume dust generated is large, and the degree of change appears to be smaller than when slopping occurs.

Therefore, by detecting the amount of fume dust generated and the degree of change thereof, it is possible to accurately determine whether slopping or spitting has occurred.

(Estimation of P and S in molten steel) Figure 5 is a graph showing the change in the basicity of hume dust, with the horizontal axis representing the blowing time (minutes) and the vertical axis representing the basicity of the fume dust. FIG. 6 is a graph showing the relationship between the P removal rate (%) on the horizontal axis and the basicity of hume dust on the vertical axis. In addition, the P removal rate is {P in hot metal (%)
- P (%) in molten steel}/P (%) in molten steel.

The basicity of the hume dust shown in FIG. 5 is determined from the concentration of CaO and SiO ₂ in the analyzed dust, and the dephosphorization rate can be determined based on this basicity and FIG. 6. Furthermore, the P concentration in the molten steel can also be determined from the determined P removal rate.

For example, when the obtained P concentration is higher than the target P concentration, soft blowing is performed to increase the degree of slag formation, and when the P concentration is within the target P concentration, the blowing conditions are not changed and the P concentration is the target. When the P concentration becomes lower than the lower limit, hard blowing is performed. Furthermore, when the P concentration is higher than the target P concentration, deP can be further promoted by adding auxiliary raw materials such as lime in addition to soft blowing to increase the CaO component and raise the basicity.

Also, the same procedure as before is performed for S. For example, when the S concentration is higher than the target S concentration, it is preferable to perform soft blowing to increase the degree of slag formation, and to add auxiliary raw materials such as lime to further increase the basicity. When the S concentration becomes lower than the target S concentration, hard blowing is performed.

(Commands to the converter control device) As mentioned above, if the degree of slag formation is low, if spitting occurs, or if the P and S concentrations in the molten steel are higher than the target P and S concentrations, in each case In order to perform soft blowing, the computer 15 raises the height of the lance, reduces the flow rate of oxygen, and outputs a control signal to the converter control device 17 to reduce the flow rate of stirring gas, such as argon gas, blown in from the bottom of the furnace. do.
Furthermore, when it is necessary to input auxiliary materials, such as when making the P and S concentrations match the target values, blowing can be controlled more effectively by outputting a control signal for inputting the auxiliary materials to the converter control device 17. .

In addition, if the degree of slag is high, if slopping occurs, or if the P and S concentrations in the molten steel are higher than the target P and S concentrations, the calculator 15 adjusts the lance height to perform hard blowing in each case. A control signal is output to the converter control device 17 to lower the flow rate, increase the flow rate of oxygen, and increase the flow rate of the stirring gas.

Since blowing is performed in this way, in the case of the present invention, the situation of molten steel and slag in the furnace can be accurately grasped, and the blowing conditions can be changed appropriately based on this.
The occurrence of slopping and spitting can be suppressed, and the P concentration in molten steel can be reduced.
As shown in the figure, T and Fe in the slag, which has a certain relationship with the P concentration in molten steel, is not increased, and therefore the tapping yield is improved.

In addition, in the above example, when estimating P and S in molten steel, P and S are measured based on the relationship between the basicity of fume dust and the P removal rate, but the present invention is not limited to this. It may also be determined using an in-furnace reaction equation. For example, it can be determined by the following formula devised by Balajiva et al.

2 [P] + 5 (%FeO) = (P ₂ O ₅ ) + 5Fe ...... (1) Kp = (%P ₂ O ₅ ) / [%P] ²・(%ΣFeO) ⁵ ... (2) logKp = 10.78log(%ΣCaO)−C ...(3) However, [P]: P concentration in molten steel (FeO): Concentration of FeO in slag (P ₂ O ₅ ): P ₂ O ₅ in slag Concentration Kp: Equilibrium constant (CaO): CaO concentration in the slag In other words, Kp is determined from equation (3), and the obtained Kp value is approximated by (%P ₂ O ₅ ) and (%ΣFeO) in the slag. The P concentration in the molten steel can be determined based on the respective analysis values in the fume dust and equation (2). This can also be determined for the S value in molten steel using the reaction equation as before.

Further, in the above embodiment, a light scattering type densitometer is used to measure the amount of fume dust generated, but the present invention is not limited to this, and can also be implemented using an ultrasonic type densitometer, a radiation absorption type densitometer, or the like.

Furthermore, in the above embodiment, a plasma emission spectrometer is used to analyze the composition of fume dust, but the present invention is not limited to this; a fluorescent X-ray analyzer may also be used, and a magnetic sensor may be installed in the suction tube 7. Of course, it is also possible to measure the content of ferromagnetic Fe, FeO, etc. by attaching it.

Furthermore, although not specified in the above embodiments, it goes without saying that the present invention can be carried out even if fume dust for analysis samples is collected continuously or intermittently. In addition, if samples are to be collected intermittently, a collection filter such as a belt-type filter or a cylindrical paper-like filter may be provided and the fume dust for samples may be collected at regular intervals using this filter. Of course.

In addition, the present invention collects an analysis sample from the fume dust collection part of the wet type dust remover 5c such as water washing,
This can also be carried out by drying it once before use.

Furthermore, it goes without saying that the present invention can also be applied to top-blown converters and bottom-blown converters in which stirring gas is not blown into the furnace bottom.

〔effect〕

As detailed above, according to the present invention, the situation of molten steel and molten slag in the furnace can be accurately determined, and the blowing conditions can be appropriately changed based on this, so the occurrence of slopping and spitting can be suppressed, and the blowing conditions can be appropriately changed. The molten steel components P and S at the end of refining can be made to match the target components, thereby improving the tapping yield and preventing reblowing when the target components and temperature are not met.
Therefore, unnecessary energy is not wasted. In addition, since the molten steel P and S components at the end of blowing can be made to match the target P and S components, the frequency of re-blowing can be reduced, reducing the blowing time and the time from the end of blowing to tapping. The present invention has excellent effects, such as being able to suppress wear and tear on the refractories.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the implementation state of the present invention, Figure 2 is a schematic diagram showing the implementation state of the present invention.
The figure is a graph showing the amount of fume dust generated and the changes in each composition with converter blowing time. Figure 3 is a graph showing the relationship between the basicity of hume dust and the thickness of slag. Figure 4 is a graph showing the relationship between the basicity of fume dust and the thickness of slag. Figure 4 is a graph showing the relationship between the basicity of fume dust and the thickness of slag. Figure 5 is a graph showing the change in the basicity of hume dust with blowing time; Figure 6 is a graph showing the relationship between the dephosphorization rate and the basicity of hume dust. Figure 7 shows T/Fe in the slag.
It is a graph showing the relationship between P and P at the end of blowing. 1... converter, 2... lance, 13... hume dust concentration measuring device, 14... hume dust analyzer, 17... converter control device.

Claims (1)

[Claims] 1. Measure the amount and components of fume dust generated during converter blowing to determine whether slopping or spitting occurs, and adjust the lance height based on the determination results to prevent the occurrence of sloping or spitting. A blowing control method for a converter, comprising controlling the flow rate of oxygen supply, the flow rate of stirring gas for bottom blowing, or the amount of auxiliary raw material input. 2. Measure the amount and composition of fume dust generated during converter blowing to estimate the molten steel composition, and based on the estimation results, adjust the lance height and feed so that the molten steel composition at the end of blowing matches the target composition value. A blowing control method for a converter, characterized by controlling the acid flow rate, the bottom blowing stirring gas flow rate, the amount of auxiliary raw materials input, or the time point at which blowing ends.