JPH04191313A - Method for controlling immersed depth of immersion tubes in vacuum sucking-up degassing treatment - Google Patents

Abstract

PURPOSE:To easily control the immersed depth of an immersion tube in a vacuum degassing vessel by detecting the immersion of a tip part of a strain gage fitted to a temp. sensor holder into a molten steel to accurately detect the position of molten steel surface level. CONSTITUTION:A ladle 2 incorporating the molten steel M is ascended, and the immersion tube at the lower part of the vacuum degassing vessel 1 is immersed into the molten steel M. Simultaneously, the temp. sensor holder 4 for temp. measuring instrument 3 is lowered while keeping away from the immersed tube and the tip part 4a thereof is immersed into the molten steel M. In such a condition, the vacuum degassing vessel 1 is evacuated to execute vacuum sucking-up degassing to the molten steel M. Then, the molten steel surface level is detected from compressive displacement developed with buoyance at the time of immersing the tip part 4a into the molten steel M, with the strain gage fitted to the temp. sensor holder 4. Thus, the immersed depth of the above- mentioned immersed depth of the immersion tube can be accurately controlled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to the immersion depth of a immersion tube in a vacuum degassing tank when performing vacuum suction degassing treatment by immersing the immersion tube in molten steel in a ladle. This relates to a method of controlling the temperature.

[Conventional technology]

Vacuum suction degassing treatment of molten steel is a process in which molten steel in a ladle is sucked up into a vacuum degassing tank to degas or remove hydrogen, oxygen, non-metallic inclusions, etc. present in the molten steel. . The vacuum suction degassing equipment used for this type of treatment consists of a vacuum degassing tank with a dip tube protruding downward at the bottom and an exhaust port at the top, and a ladle installed below the vacuum degassing tank. It mainly consists of a temperature measuring device that measures the temperature of molten steel by immersing a temperature sensor holder, which moves up and down avoiding the immersion tube, into molten steel in a ladle from its tip side.

Such vacuum suction degassing treatment is carried out using the RH method, which uses a vacuum degassing tank with two immersion tubes and circulates the molten steel between the ladle and the vacuum degassing tank, and Using only one vacuum degassing tank, the molten steel is sucked up into the vacuum degassing tank for a while (several tens of seconds), then the molten steel is returned to the ladle, stirred, and sucked up again. D to repeat the rash
There are methods such as H method.

Below, the RH method will be explained with reference to the drawings as a representative example.

FIG. 4 is a cross-sectional explanatory view of one example of a vacuum suction degassing device used for carrying out the RH method, and FIG. 5 is a cross-sectional explanatory view of the implementation status of vacuum suction degassing by the device of FIG. 4.

As shown in FIG. 4, the vacuum suction degassing device for the RH method is also mainly composed of the vacuum degassing tank 1, the ladle 2, and the temperature measuring device 3 as described above. A discharge port 1c connected to a vacuum pump (not shown) is provided at the top, a ladle 2 is installed below the vacuum degassing tank 1, and a temperature measuring device 3 measures the temperature at the tip 4a. A temperature sensor holder 4 having a sensor moves from a predetermined position toward the inside of the ladle 2 avoiding the immersion pipe of the vacuum descaling tank 1 to measure the temperature of the molten steel M. . In the case of this vacuum suction degassing device for the RH method, two suction pipes 1a are used as immersion pipes for the vacuum degassing tank 1.
A gas suction pipe 1d is provided to protrude downward as a discharge pipe 1b, and a gas suction pipe 1d is opened on the inner wall of the suction pipe 1a. There are various types of temperature measuring device 3, one example of which is shown in FIG. It has a structure in which a sensor holder 4 is attached. In carrying out the vacuum suction degassing process, in order to smoothly suck up the molten steel M, the relative positions of the vacuum degassing tank 1 and the ladle 2 may be adjusted, such as by moving them closer together or separating them, or by maintaining them at an appropriate distance. Need to make adjustments. Therefore, in general, only one of the two is raised or lowered, and the one shown in Figure 4 is the ladle 2.
This is a device for raising and lowering a ladle, and is equipped with a ladle stand 8 that is moved up and down by a hydraulic bag [8a, and is equipped with a Saga transmitter 8b for knowing its position.

To carry out the RH method with such a vacuum degassing device, first transfer the ladle 2 into which the molten steel M has been transferred from the converter etc. onto the ladle stand 8 located at a low position, and then place the ladle 2 in the vacuum degassing tank. 1 and the ladle 2, that is, in the case of this device, the ladle 8 is moved upward by the hydraulic device 8a, and at least the tip portions of the suction pipe 1a and the discharge pipe 1b of the vacuum degassing tank 1 are removed. The relative positions of the vacuum degassing tank 1 and the ladle 2 are adjusted so that they are immersed in the molten steel M. Next, when the vacuum pump is activated and an inert gas such as argon gas is blown into the gas suction pipe 1d, the molten steel M passes through the suction pipe 1a and into the vacuum degassing tank 1 as shown in FIG. 5 due to the principle of a bubble pump. The gas is sucked up into the vacuum degassing tank 1, and returns to the ladle 2 via the discharge pipe 1b. The molten steel M is degassed in the vacuum degassing tank 1 while circulating in this way, and when the degassing is finished, the vacuum pump and inert gas injection are stopped, the ladle 2 is lowered, and the vacuum degassing tank 1 is removed. The molten steel M in 1 is discharged into the ladle 2. During such operations, the temperature sensor holder 4 of the temperature measuring device 3 is moved down -F at appropriate times as shown in FIG. 5 to measure the temperature of the molten steel, thereby controlling the temperature.

In the case of the DH method, molten steel is sucked up from one immersion pipe into a vacuum degassing tank, left to stay for a certain period of time, degassed, and then returned to the ladle from the same immersion pipe.Therefore, one immersion pipe is used as a suction pipe. and a discharge pipe), and repeat this process. Other than this point, it is basically the same as the RH method.

In such vacuum suction degassing treatment, in order to smoothly circulate (RH method) and suck up (DH method) the molten steel M, it is necessary to use the suction pipe 1a in the RH method and the suction pipe 1a in the DH method. so that at least the tip of the immersion pipe as a suction pipe (hereinafter, the description of the suction pipe 1a is also an explanation of the immersion pipe as a suction pipe in the DH method) is always immersed in the molten steel M. It is important to control the immersion depth of the suction tube 1a, that is, to adjust the relative position between the vacuum degassing tank] and the ladle 2. The above-mentioned relative positioning of the shoulders is performed by raising or lowering either the ladle 2 or the vacuum degassing tank 1. The vacuum suction degassing device shown above moves the ladle stand 8 up and down to raise and lower the ladle 2, thereby controlling the immersion depth of the suction pipe 1a.

Conventionally, the immersion depth of the suction pipe 1a has been controlled by adjusting the relative positions of the vacuum degassing tank 1 and the ladle 2 while visually observing the suction pipe 1a and the molten steel level.

However, the conditions at the work site do not always guarantee the accuracy of visual inspection, and if the molten steel level in the ladle 2 drops below the lower end of the suction pipe 1a during degassing, the molten steel M falls into the ladle 2 in an instant, and in some cases it may overflow outside the ladle 2, causing a serious accident. is provided at the same level as or below the level of the tip of the suction pipe 1a, so the tip of the discharge pipe 1b does not leave the molten steel level first).

[Problem to be solved by the invention]

The present invention solves the above-mentioned drawbacks of the prior art, and makes it possible to accurately detect the molten steel level without visual inspection and adjust the relative position between the vacuum degassing tank and the ladle, and at a relatively low cost. The object of the present invention is to configure a method for controlling the immersion depth so that it can be easily performed without the need for immersion.

[Means to solve the problem]

As a result of various studies, the inventor of the present invention found that a strain gauge was attached to the temperature sensor holder 4 using the temperature measuring device 3 provided in the vacuum suction degassing device, and that the tip of the temperature sensor holder 4 was connected to the molten steel. The present invention was completed by discovering that the level of molten steel can be accurately determined from the position of the temperature sensor holder by catching the signal obtained by the strain gauge when the steel is immersed in water.

Below, a method for controlling the immersion depth of the immersion tube in the vacuum suction degassing process according to the present invention will be explained in detail.

FIG. 1 is an enlarged explanatory view with a part cut away showing an example of a temperature sensor holder with a strain gauge used in the method of the present invention, FIG. 2 is an enlarged view of section A in FIG. 1, and FIG. B in Figure 2
-B sectional view.

The temperature sensor holder 4 of the temperature measurement bag W3 has a shape roughly as shown in FIG. That is, a thermal lightning pair is attached to the tip 4a as a temperature sensor, and the lead wire 4C connected to it passes through the temperature sensor holder 4 and is connected to the main wire by a metal connector 4d at the end on the base 4b side. be done. The cap nut 4e on the base 4b side constitutes a connection part with a cooling gas supply pipe for supplying cooling gas into the temperature sensor holder 4, and determines the position of the temperature sensor holder 4 on the base 4b side. A holding connector is attached to the chino 7 shown in FIG. In the method of the present invention, first, a strain gauge 9 is attached to the inner surface of the outer tube of the temperature sensor holder 4 as shown in FIGS. 2 and 3, and the amount of strain generated in the strain gauge 9 is measured by connecting the strain gauge lead wire. The signal is then input to a distortion detection device (not shown). Therefore, when the tip 4a of the temperature sensor holder 4 is immersed in the molten steel M, the buoyant force is transmitted to the outer tube of the temperature sensor holder 4, causing a sudden compressive displacement in the strain gauge 9, and generating an electrical signal. .

Once the strain gauge 9 has been installed as described above, the drive motor 6 is operated to lower the temperature sensor holder 4 from a predetermined position toward the ladle 2 on the ladle stand 8, and
The molten steel level is detected by catching the signal emitted by the strain gauge 9 with the strain detection device when a is immersed in the molten steel M, and the molten steel level is detected from the position of the temperature sensor holder 4 at that time and the first predetermined position of the temperature sensor holder 4. The location of the level of molten steel M is known. Then, it is determined how much the ladle 2 needs to be raised so that the suction pipe 1a is immersed in the molten steel M at an appropriate depth, and the hydraulic device 8a is operated accordingly.

One example will be specifically explained with reference to the drawings.

As shown in FIG. 4, the height of the tip of the temperature sensor holder 4 above the floor when it is in a predetermined position is Ho, and for example, the horizontal position of a fixed point P on Chesif is defined as Ho. shall be. The bottom of ladle 2 (
When the temperature sensor holder 4 is lowered by a vertical distance toward the inside of the ladle 2, where the upper surface of the ladle stand 8 is at a height D above the floor, and the fixed point P is located at the horizontal position L□. If the signal from the strain gauge 9 is caught, the level of the molten steel M in the ladle 2 will be at the height above the floor H2 (as shown in Fig. 4).
=H0-h). In the rotating device, the vacuum degassing tank 1 is fixed in position, so the height G above the floor of the tip of the suction pipe 1a is constant. Therefore, the suction pipe 1a is melted! II
An appropriate amount of rise d of the ladle 2 (therefore, its bottom surface) is required to not only ensure immersion into M but also to achieve the optimum immersion depth and smoothly perform vacuum suction degassing treatment. The amount of rise d differs depending on the size and operating conditions of the vacuum degassing tank 1 and ladle 2, so it is determined individually for each vacuum suction degassing device.The appropriate amount of rise d of the ladle 2 Once determined, raise the ladle stand 8 by the amount d as shown in Figure 5.
It is sufficient to perform the vacuum suction degassing treatment as described above. In order to measure and calculate the vertical movement of the temperature sensor holder 4 in the above-described operation, it is preferable to incorporate a cercin 10 into the drive motor 6 as shown in the figure. The Celsin 10 is a position transmitter, and functions to convert the amount of movement of the temperature sensor holder 4 into an electrical signal. Although the rotation is performed using the RH method, it can be performed similarly using the DH method.

〔Effect of the invention〕

As detailed above, the method of controlling the immersion depth of the immersion tube in the vacuum suction degassing process according to the present invention utilizes a temperature sensor holder that moves up and down in the vacuum suction degassing process. A strain gauge is attached to it, and the molten steel level is detected by catching the signal emitted by the strain cage when the tip of the temperature sensor holder is immersed in molten steel. By controlling the temperature of the molten steel, the position of the molten steel level can be accurately known, and the immersion tube can be reliably immersed in the molten steel. There is no fear of unexpected molten steel discharge or overflow, and since the existing temperature measuring device is used, the immersion depth of the immersion pipe can be easily controlled at relatively low cost. It is possible to do so, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is an enlarged explanatory view with a part cut away showing an example of a temperature sensor holder with a strain gauge used in the method of the present invention, FIG. 2 is an enlarged view of section A in FIG. 1, and FIG. B in Figure 2
-B line sectional view, Figure 4 is a cross-sectional explanatory diagram of an example of a vacuum suction degassing device used in the implementation of the RH method, and Figure 5 is an illustration of the implementation status of vacuum suction degassing using the device shown in Figure 4. It is a cross-sectional explanatory view. In the drawing 1... Vacuum degassing tank 1a... Suction pipe 1b... Discharge pipe lc... Exhaust port 1d... Gas suction pipe 2... Ladle 3. ...Temperature measuring device 4...Temperature sensor holder 4a...Tip portion 4b...Base 4c...Lead wire 4d...Metal connector 4e...Fall nut 5. ... Sprocket 6 ... Drive motor 7 ... Cheno 8 ... Ladle stand 8a ... Hydraulic system 8b ... Position transmitter 9 ... Strain gauge 10 ... ...Celsin D... Height above the floor of the bottom of the ladle d... Rise height of the bottom of the ladle G... Height above the floor of the suction pipe of the vacuum degassing tank Ho...
・Height above the floor of the tip of the temperature sensor holder when it is in the specified position H□...Height above the floor of the molten steel level h...Between the tip of the temperature sensor holder and the molten steel level when it is in the specified position Vertical distance M... Molten steel 2nd TA B f 3 Kasumi Fig. 4

Claims (1)

[Claims] 1. A vacuum degassing tank with a downwardly protruding immersion tube at the bottom and an exhaust port at the top, a ladle installed below it, and a temperature sensor holder that moves up and down avoiding the immersion tube. When performing vacuum suction degassing of molten steel using a vacuum suction degassing device that mainly consists of a temperature measuring device that measures the temperature of the molten steel by immersing it in the molten steel from the tip side,
A strain gauge is attached to the temperature sensor holder, and when the temperature sensor holder is lowered and its tip is immersed in molten steel, the signal obtained by the strain gauge is captured and the position of the temperature sensor holder at that time and the beginning of the temperature sensor holder are measured. 1. A method for controlling the immersion depth of a immersion tube in vacuum suction degassing treatment, characterized by adjusting the relative position of a vacuum degassing tank and a ladle by knowing the position of the molten steel level from the predetermined position of the molten steel.