JPS6312126B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a slag control method in a converter,
In particular, the purpose is to prevent slopping and to obtain an optimal slag state depending on the type of molten steel.

As methods for detecting the slag condition during converter blowing, methods using acoustics and furnace vibration, and exhaust gas analysis methods have been proposed, but in both cases, the furnace condition can be detected through an intermediate medium. It is difficult to say that the accuracy is satisfactory because it is only an indirect grasp of the information.

In other words, the method of using acoustics depends on the shape of the furnace body,
The variation is large because it is easily affected by metal adhesion at the furnace mouth and noise around the furnace.Furthermore, the furnace body vibration measurement method mainly detects vibrations due to metal flow, and it is difficult to separate detection of vibrations due to slag flow alone. In addition, the exhaust gas analysis method had problems with the temporal matching of the reactions in the furnace and the accuracy of the correspondence between the analytical values and the slag formation situation.

In comparison, the kinetic acceleration acting on objects such as main lances that are vertically suspended in the furnace and directly immersed in the forming slag is more effective in that it is less affected by fluctuations in furnace conditions because it does not involve an intermediate medium. This is excellent information, and we have already proposed a slag control method based on previous development results.

However, the control method that uses the horizontal acceleration acting on a vibration lance such as the main lance mentioned above as an information source is not effective when the vibration lance is freely suspended by a wire or the like and follows the flow of slag. However, when the lance suspension mechanism has a structure that restricts the movement of the lance body, such as a carriage type, the accuracy tends to be lower than that of the wire type, making it difficult to apply.

What is the carriage-type lance suspension mechanism?
As an example is shown in FIGS. 1 and 2, a roller 2 is installed inside a vertical guide frame 1 with a groove-shaped cross section.
A carriage 3, which can be raised and lowered freely, is housed therein, and a lance 5 is fixed by means of lance support fittings 4 protruding from the guide frame 1 above and below the carriage 3, and this carriage 3 is guided by a wire 6. It has a structure in which the lance 5 is raised and lowered by winding it up and unwinding it along the frame 1.As is clear from the figure, in this lance suspension mechanism, the horizontal movement of the lance is restrained. Even with an accelerometer attached, it was difficult to detect the lance's motion acceleration.

The present invention advantageously solves the above problems and proposes a slag control method that is useful when applied to a converter with a lance suspension mechanism in which horizontal movement is restricted.

Now, if the main lance is inserted into the furnace during blowing, whether or not this lance is restrained,
The tip of the lance, which is immersed in the foaming slag, is still subjected to intense kinetic energy due to the slag flow. Therefore, in a converter equipped with a lance suspension mechanism whose movement in the horizontal direction is restrained, such as the one targeted by this invention, since the lance is restrained, a considerable force is applied to the restrained portion. become.

Therefore, in the present invention, the kinetic energy of the slag applied to the main lance is measured as the strain produced in the lance restraint portion, and the slag-making condition in the furnace is controlled based on this measured value.

This is because as slag forming becomes more active, the strain generated in the restraint area also increases, so changes in this strain are constantly monitored and slag formation is controlled based on the relationship between its unique pattern and the slag formation stage that depends on it. can be done.

In other words, since the main lance directly receives the kinetic energy of the slag, it is very sensitive to changes in the slag formation situation, and especially after the level of formed slag reaches a height where it contacts the lance, the kinetic energy generated in the lance restraint area is extremely sensitive. resulting in an increase in the amount of strain,
Furthermore, as the slag level height increases and the amount of gas generated increases, the energy applied to the lance increases, and the strain generated in the lance restraint area becomes even greater, so slag forming occurs without any delay. This means that it can directly and accurately detect changes, and can faithfully follow even short-term changes.

In this invention, the main lance of the above-mentioned carriage type suspension mechanism is used as a detector for detecting the kinetic energy of the slag.

Therefore, the present invention is particularly advantageously applicable to a converter having a top-blowing function, that is, a top-blowing converter and a top- and bottom-blowing converter.

Further, as the strain gauge, a resistance wire strain gauge or a semiconductor strain gauge is suitable.

By the way, the direction of the kinetic energy applied to the main lance changes in various ways due to fluctuations in the reaction state in the furnace, and therefore there is a limit to the ability to accurately control the slag formation state by measuring strain only in a specific direction. In this regard, in order to control the slag with higher precision, the following procedure may be used.

In other words, when measuring strain, it is measured in two directions (referred to as x and y directions) that are perpendicular to each other on a horizontal plane, and from these values, the following formula (1) ε = √ ( _x ) ² + ( _y ) ² ... ...(1) Here, ε _x : The magnitude of the strain in the x direction on the horizontal plane ε _y : The magnitude of the strain in the y direction on the horizontal plane is used to find the true magnitude of strain, and this is used as control information. It is.

Next, an example of a measurement processing system for realizing this control method is shown in FIG.

This example shows a case where a carriage method is used as the lance suspension mechanism, a resistance wire strain gauge is used as the strain gauge, and the oxygen supply lance 5 is fixed at the top as shown in Figures 4 and 5. Two strain gauges 7 (x-axis) are placed on the horizontal plane of the metal fitting 4,
7' (y-axis) were arranged and mounted at right angles to each other.
The strain gauges 7 and 7' are used in the x-axis direction and the y-axis direction.
Strains in the axial direction are detected, and slag control is performed by a system comprising waveform converters 8, 8', a synthesis calculator 9, and a process computer 10. In FIG. 3, 11 is molten steel and 12 is slag.

In the process of actual operation of converter blowing under slag control based on the above-mentioned combined strain values, it is noted that the above-mentioned combined values acting on the lance depend on the oxygen flow rate and lance height under almost the same slag formation conditions. It was found that the sludge state fluctuated, and it was recognized that in order to further improve the sludge detection accuracy, it was necessary to make adjustments according to the amount of oxygen supplied and the lance height.

Therefore, the inventors installed an electrode-type probe with a detection circuit that is activated by contact with the top surface of the slag forming on a sub-lance during blowing operations, and measured the forming height by suspending the probe. This was carried out in conjunction with the detection of the strain acting on the support fitting 4 of the oxygen supply lance 5, and as a result of organizing the current values of the oxygen supply flow rate and the position of the lance 5 at that time, the following equation (2) was obtained.

ε=aF _O2 (S _H −L _H )+b ……(2) Here, F _O2 : Oxidation flow rate (Nm ³ /min) S _H : Slag forming height (m) L _H : Lance height (m ) In formula (2), a and b are respectively correction values determined in advance according to the characteristics of the converter, and can be treated as constant in an actual furnace.

In the above equation (2), the slag forming height S _H and the lance height L _H are both the heights from the stationary steel bath surface, and therefore (S _H −L _H ) in the above equation.
means the immersion depth of the lance in the forming slag, and it is clear from equation (2) that the following equation (2)′ S _H =ε−b/a・F _O2 +L _H ……(2)′ Accordingly, the slag forming height can be estimated, and this estimated value can be used immediately to determine the slag situation.
This is particularly useful for predicting the occurrence of sloping.

In other words, the slag phenomenon in converters generally occurs when the level of formed slag gradually rises and begins to overflow from the furnace mouth, or when a rapid reaction suddenly occurs, resulting in explosive slopping. While it is possible to make some predictions by visual observation of the scattering of slag droplets around the furnace mouth or by using conventional techniques,
The latter type of sudden sloping was extremely difficult to predict because the change occurred in a short period of time. However, with the method of the present invention, strain can be measured without delay time, and since the strain is directly transmitted from the motion of the slug, the response is quick, and therefore it is extremely advantageously suited for the purpose of predicting the occurrence of sloping.

Now, FIG. 6 shows an example of an embodiment in which the present invention is applied to the operation of a 200-ton top-blowing converter, and will be specifically described. In Fig. 6, the horizontal axis is the time axis showing the progress of blowing, and the vertical axis shows the original strain waveforms ε _x , ε _y in the x and y directions, and the waveforms ε _x , ε _y further every few seconds after being synthesized. The integrated and averaged average ε value, lance height, and oxygen delivery rate are taken. In addition, the lance height,
The broken line showing the progress of the oxygen supply rate shows the set value determined in advance according to the already established blowing program, whereas the solid line shows the slag production control by taking corrective action based on the strain detection results according to the present invention. Indicates the operating value.

First, according to the blowing program, the lance height L _H : 2.2
Start blowing with the setting of oxygen supply rate F _O2 : 700Nm ³ /min, and before entering the control range, set the lance height to 2.0m according to the above program, and when the lance height enters the control range. L _H 1.6m, oxygen flow rate F _O2
The blowing was performed according to the program at 650Nm ³ /min.

The middle point in the figure shows the bubbling during the desiliconization period, and in this case, the oxygen supply rate F _O2 was set to 500N to suppress gas generation.
When the pressure was reduced to m ³ /min, it returned to a stable state after a while, so it was returned to 650Nm ³ /min. As blowing continued, the slag height increased as the ε value increased, creating the risk of slopping. At that point, the lance height was lowered to 1.4 m and hard blowing was performed, resulting in the ε value shown in the figure. The slag height decreased with the decrease, and although only a slight sloping tendency occurred, it was successfully suppressed without any major problems. So again, the lance height L _H
I returned the lance height to 1.6 m, but after a while the lathering became insufficient, so I changed the lance height L _H at that point.
When I raised it to 1.8m and performed a soft blow, the lathering was good, so I raised it back to 1.6m, and
After that, I was able to finish blowing smoothly.

The above description has mainly been about the case where this invention is applied to a top-blown converter, but it is also certain that smooth slag control can be achieved in the same manner as described above when it is applied to a bottom-blown converter. being admired.

Thus, according to the present invention, in a converter with a lance suspension mechanism in which movement in the horizontal direction is restrained, slag production can be carried out to achieve the optimum slag state according to the type of molten steel without worrying about slopping throughout the entire blowing operation. The situation can be controlled, and the amount of strain can always be accurately measured regardless of changes in the direction of slag movement, so accuracy is highly reliable.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a carriage type lance suspension mechanism, FIG. 2 is a view taken along the line A--A, FIG. 3 is an explanatory diagram of an example of a measurement control system according to the present invention, and FIG.
Figure 5 shows the mounting position of the strain gauge,
FIG. 6 is a graph showing specific details of slag control according to the present invention.

Claims (1)

[Claims] 1 A main lance of a carriage type suspension mechanism whose movement in the horizontal direction is restricted is vertically suspended in the converter furnace, and the kinetic energy based on the forming slag acting on the main lance is transferred to the main lance. The strain produced in the lance restraint part is measured by a pair of strain gauges arranged perpendicularly to each other on the horizontal plane of the support fitting to be fixedly supported.
A method for controlling slag production in a converter that involves controlling slag production in the furnace based on this measured value.