JPS6355465A - Device and method for measuring molten steel flow velocity - Google Patents

Abstract

PURPOSE:To exactly derive a flow velocity in the measuring flow direction by allowing a plane determined by the center of a detector and an eccentric shaft to be opposed to said direction. CONSTITUTION:Molten steel in a tundish 1 flows into a mold 3 from a hole 2a of a dipping nozzle 2. Also, in the molten steel 4 in the mold 3, a detector 5 is immersed, and coupled to a torque converter 6 through an eccentric shaft 5a. This converter 6 consists of a strain gauge, and converts the torque which has been transferred through the eccentric shaft 5a from the detector 5, to a corresponding electric signal through a dynamic strain gauge 7. Also, the torque around the center line of the eccentric shaft for working on the detector 5 has magnitude corresponding to a flow velocity in a prescribed direction, to be measured. Accordingly, by allowing a plane determined by the center of the detector 5 and the eccentric shaft 5a, to be opposed to the measuring direction, the flow velocity in the prescribed direction can be derived exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus and method for measuring the flow velocity of molten steel flow. More specifically, the present invention relates to an apparatus and method for measuring the flow velocity of molten steel flowing into a mold during continuous casting by detecting the torque (rotational moment) applied to an immersion detector.

(Prior art) Quantitatively understanding the flow of molten steel in the mold in continuous casting equipment is one of the most important points in slab manufacturing, and is also useful for discovering unilateral flow from the immersion nozzle. This is a valuable piece of information. However, it is extremely difficult to understand the flow of molten steel, and it has rarely been measured in the past.

Recently, the following method for measuring molten steel flow in a mold has been proposed (lead powder, etc.: Iron and Steel 82-5920 r
Control of molten steel flow in a continuous casting mold using an electromagnetic brake").

That is, a rond or block made of refractory is immersed in the molten steel flow in a mold, and a strain gauge connected to the upper end of the rond via a plate is taken. This is a method for measuring changes in the magnitude of distortion over time.

(Problems to be Solved by the Invention) However, in this method, the flow velocity is only evaluated based on the amplitude of the change in strain over time, and the absolute value of the flow velocity in a predetermined direction cannot be determined. For example, E
MBR (Iielectro-Magnetic M
An increase or decrease in the amplitude of strain due to the presence or absence of the use of old nrFlking (electromagnetic braking of molten steel flow in the mold) was detected, but a difference in the absolute value of strain was not detected.

Theoretically, it is certain that as the flow velocity of molten steel increases, the strain also increases. However, the force that a strain gauge receives is the sum of fluid pressures from flows in various directions, so it is impossible to determine which direction of flow is causing the strain. Therefore, with this method, it is impossible to directly determine the flow velocity of molten steel in a predetermined direction.

Therefore, an object of the present invention is to provide an apparatus and method for directly determining the flow velocity of molten steel in a predetermined direction.

Note that Japanese Patent Application Laid-open No. 104512/1984 proposes a method for determining the absolute value of the flow velocity of molten steel. However, the value of the drag coefficient CD necessary for calculating the flow velocity in this publication cannot be accurately determined by a bench test, and can only be accurately calculated by actually measuring the actual flow. Therefore, the method according to this publication can only obtain an approximate value of the flow velocity. Further, it is extremely difficult to create a shape like the pressure receiving body 7a, and there is a problem in that it is difficult to achieve sufficient accuracy. Furthermore, since the strain gauge 7h is attached to the pressure receiving plate 7d, there is a larger error in the attachment. Therefore, it is also an object of the present invention to provide a device and a method that can accurately determine the flow rate of molten steel with a simple configuration.

(Means for Solving the Problems) Thus, the gist of the present invention is to provide a detector that is immersed in molten steel for measuring flow velocity and receives a torque from the molten steel corresponding to the flow velocity in a predetermined direction, and a torque applied to the detector. This is a molten steel flow rate measuring device comprising: a torque measuring means for measuring the magnitude of the molten steel flow rate;

The gist of the method of the present invention is a molten steel flow rate measuring method in which the molten steel flow rate is calculated from the magnitude of the torque corresponding to the flow rate of the molten steel in a predetermined direction, which is received by a detector immersed in the molten steel whose flow rate is to be measured.

In this case, in order to minimize melting loss, it is preferable that the detector consists of a cylindrical body attached to an eccentric shaft and immersed in molten steel.

Further, it is preferable that the torque applied to the detector be measured using a strain gauge.

(Function) According to the present invention, the detector receives a torque corresponding to the flow velocity of molten steel in a predetermined direction. This predetermined direction is, for example, a horizontal direction centered on a nozzle immersed into a mold from a tundish in continuous casting equipment.

For example, if an immersed cylinder attached to an eccentric shaft is used as a detector, the cylinder is placed in a plane defined by itself and the center line (central axis) of the eccentric shaft (i.e., on which the center of the cylinder and the eccentric shaft lies). It receives a torque corresponding to the flow velocity in the direction perpendicular to the plane on which the line rests. Therefore, in this case, the cylindrical body is positioned so that the direction perpendicular to the plane coincides with the predetermined direction in which flow velocity measurement is performed.

The torque experienced by the detector thus corresponds to the flow velocity in the given direction to be measured. Therefore, by measuring this torque with a strain gauge or the like, the flow velocity can be determined accurately.

(Example) Next, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic side view showing the overall configuration of an embodiment in which the present invention is used to measure the flow velocity of molten steel flow in a mold of continuous casting equipment.

The molten steel in the tundish l flows into the mold 3 through the hole 2a of the immersion nozzle 2. A detector 5 is immersed in the molten steel 4 in the mold 3 and connected to a torque converter 6 via an eccentric shaft 5a.

The torque converter attached to the bottom of the tanditshu 1 consists of a strain gauge, and is connected to the eccentric shaft 5 from the detector 5.
The torque corresponding to the molten steel flow rate transmitted through the dynamic strain gauge 7 is converted into a corresponding electric signal. That is, dynamic strain meter 7
is equipped with a bridge circuit to detect changes in electrical resistance due to strain gauge strain. Furthermore, the recorder 8 records changes over time in the electrical signal corresponding to the torque. Note that the torque converter 6 is generally not a high heat type. Therefore, in this embodiment, since the radiant heat from the molten steel is large, heat countermeasures are taken by installing a heat shield plate and air purging the inside.

Next, the detector 5 of the apparatus shown in FIG. 1 will be explained in detail with reference to FIGS. 2 and 3. FIG. 2 is a schematic plan view of the detector 5, and FIG. 3 is a schematic side view.

The detector 5 is composed of a cylindrical body made of cermet whose main components are metal molybdenum and high-purity zirconia. The detector 5 will have a large error if the amount of erosion is not small even when immersed in molten steel for a long time. Therefore, in order to minimize partial (local) erosion loss, it was made into a cylindrical shape. Of course, the flow velocity can be detected even if it is in the form of a flat plate. Furthermore, it is important to select a material that has minimal melting loss, and this device uses a cermet whose main components are metallic molybdenum and high-purity zirconia. As for the specific dimensions of the cylindrical body constituting the detector 5, for example, the height h is 270 m+.

Let the radius r be 15ml11.

The detector 5 is fixed to an eccentric shaft 5a having a center fl (center axis>A) eccentric from the center line (center axis) B of the cylindrical body,
Eccentric shaft 5a is coupled to an input shaft of torque converter 6. Therefore, the detector 5 rotates about the center line A from the mounting number position (shown by the solid line in Figure 2) (the broken line in Figure 2 indicates the state rotated by θ° clockwise in the figure). )
. Note that the eccentricity d of the eccentric shaft 5a is, for example, 14 mm.

The mounting position of the detector 5 is determined as follows. That is, with respect to the predetermined direction in which the molten steel flow velocity is to be measured (see the arrow V indicating the flow velocity in Figures 2 and 3), the plane determined by the center lines A and B (i.e., the plane on which the center lines A and B are placed) is The detector 5 and the eccentric shaft 5a are positioned so as to be perpendicular to each other. (If there are multiple measurement directions, multiple detectors 5 are provided for each direction.) The detector 5 is positioned as described above and rotates around the center line A of the eccentric shaft 5a. Therefore, the molten steel flow velocity V in a given direction
It receives a rotational force or torque T corresponding to . Specifically, this torque T is given as follows.

Assuming that the molten steel is flowing at an average flow velocity V, the force F that the detector 5 receives is given by F=(1/g)・r・v”・s (tl. However, γ is the molten steel density, g is gravitational acceleration, S
is the effective cross-sectional area of the detector 5 with respect to the molten steel flow. Also,
The torque T that the detector 5 receives in the state shown by the solid line in FIG.
If we rearrange the r r formula (2), we get T=21"r-d...+31Similarly, in the case of any position indicated by the broken line in Figure 2, T=2F-r -d -cos θ...(4) Therefore, when we calculate V from (4)2 and equation (1), we get:
From equation (5), the flow velocity V can be uniquely determined from the rotational torque T. Note that if the size of the detector 5 is as described above and the maximum flow velocity is 0.4 m/sec, the generated torque T will be approximately 144 g-cm at maximum.

(Effects of the Invention) In the present invention, the torque T acting on the detector 5 and centered on the center line of the eccentric shaft 5a has a magnitude corresponding to the flow velocity V in a predetermined direction to be measured.

Therefore, by arranging a plane determined by the center of the detector 5 and the eccentric shaft 5a to face the measurement flow direction, it is possible to accurately determine the flow velocity in that direction.

FIG. 4 shows the change over time in the torque T measured and recorded by the embodiment device shown in FIG.
The case where the position is changed to 5 cm is shown.

From the temporal average value (absolute value) of the torque T for each position of the detector 5 obtained in this way, the flow velocity of the molten steel 4 in a predetermined direction can be calculated using the above equation (5). Figure 5 is a graph showing the relationship between the horizontal molten steel flow velocity V centered on the nozzle 2 in the mold 3 and the distance from the center of the nozzle 2, which was determined in this way. With this method, it was impossible to accurately calculate the flow velocity in a predetermined direction.

1. FIG. 6 shows the temporal change in torque T due to the use of EMBR. At the arrow position in the figure, EMB R100^ is changed to EMBR50^, and the absolute value and amplitude of torque T change accordingly.

By introducing this device, proper use of EMBR can be established,
This greatly contributed to reducing surface defects that occur on slabs. 7th
The figure shows the effect of suppressing surface flaws by introducing the flow rate measuring device according to the present invention at the point indicated by the arrow.

In addition, as a result of using a cermet cylinder as the detector 5, even during continuous measurement for about 3 hours, although some corrosion damage occurred on the cylinder at the slag line, there was no damage to the part immersed in the molten steel. No melting loss occurred.

[Brief explanation of drawings]

FIG. 1 is a schematic side view or block diagram showing the overall configuration of an apparatus according to an embodiment of the present invention. FIGS. 2 and 3 are a schematic plan view and a side view of a detector of the apparatus shown in FIG. 1, respectively. Figure; Figure 4 is a graph showing an example of the measurement of torque corresponding to the melt flow rate using the apparatus shown in Figure 1; Figure 5 is a graph showing the measurement of the molten steel flow rate from the center of the nozzle determined by the measurement using the apparatus shown in Figure 1. A graph showing changes with distance; FIG. 6 is a graph showing changes in measured torque over time due to the use of EMBR in the device of FIG. 1; and FIG. 3 is a graph showing the effect of suppressing the occurrence of slag surface defects by introducing .

Claims (6)

[Claims] (1) Molten steel comprising a detector that is immersed in molten steel to measure the flow velocity and receives a torque from the molten steel corresponding to the flow velocity in a predetermined direction, and a torque measuring means that measures the magnitude of the torque applied to the detector. Flow rate measuring device. (2) The molten steel flow rate measuring device according to claim 1, wherein the detector is a cylindrical body attached to an eccentric shaft and immersed in the molten steel. (3) The molten steel flow rate measuring device according to claim 1 or 2, wherein the torque measuring means includes a strain gauge. (4) A molten steel flow velocity measuring method in which the molten steel flow velocity is calculated from the magnitude of the torque corresponding to the flow velocity of the molten steel in a predetermined direction, which is received by a detector immersed in the molten steel for measuring the flow velocity. (5) The method for measuring the flow rate of molten steel according to claim 4, wherein the detector comprises a cylindrical body attached to an eccentric shaft and immersed in the molten steel. (6) The molten steel flow rate measuring method according to claim 4 or 5, wherein the magnitude of the torque received by the detector is measured using a strain gauge.