EP2316594A1

EP2316594A1 - Device and method for detecting and controlling the slag in molten steel

Info

Publication number: EP2316594A1
Application number: EP09757099A
Authority: EP
Inventors: Zhiheng Tian
Original assignee: Tian Li; Tian Lu; Tian Zhiheng
Current assignee: RAMON SCIENCE AND TECHNOLOGY Co Ltd
Priority date: 2008-06-02
Filing date: 2009-07-10
Publication date: 2011-05-04
Also published as: CN101306466A; WO2009146665A1; CN101306466B

Abstract

Embodiments of the present invention provide an apparatus and method for detecting slag in molten steel. The apparatus includes: a sensor, adapted to obtain at least one kind of characteristic information of a surface of a molten steel coverage layer of the tundish and provide the characteristic information for a signal processor; and the signal processor, adapted to determine whether there is slag according to the characteristic information, and output, if there is slag, a slag alarm signal and a control signal used for stopping the molten steel and the slag from flowing from a ladle into a tundish via a long-nozzle; wherein the molten steel and slag flow from the ladle into the tundish via the long-nozzle, and density of the slag is smaller than that of the molten steel. The apparatus can be installed conveniently, has long lifetime and will not output erroneous alarm signal prematurely due to environment interference.

Description

FIELD OF THE INVENTION

The present invention relates to slag detecting and controlling techniques, and more particularly, to an apparatus and method for detecting and controlling slag in molten steel flowing into a tundish from a ladle via a long-nozzle.

BACKGROUND OF THE INVENTION

During a continuous casting procedure, at the end of the flowing of molten steel out of a ladle, there may be slag flowing into a tundish together with the molten steel. In order to ensure the purity of the molten steel in the tundish, it is required to detect and control the slag flowing into the tundish from the ladle. Among current popular detection techniques, there is an electromagnetic detection method and a vibration detection method. As to the electromagnetic detection method, one defect is that an electromagnetic sensor needs to be installed in a high temperature area around an upper nozzle of the ladle. Due to the high temperature, the lifetime of the electromagnetic sensor is relative short. And once the electromagnetic sensor is down, it cannot be replaced until medium maintenance of the ladle (the period is usually one week), which affects the continuous operation of detecting apparatus. Another defect of the electromagnetic detection method is that the installation of the sensor necessitates modification of a seat brick and a datum plate of the ladle and the workload of the modification is relative heavy. These two defects affect the application of the electromagnetic detection method. As to the vibration detection method, one defect is that there is serious vibration source interference in a continuous casting field. Even if the adjustment of a slider of the ladle and the working of many machines are restricted during the slag detection, a vibration slag detection apparatus may still output an erroneous alarm prematurely, which makes a lot of molten steel remained in the ladle and thus seriously affects the utilization ratio of the molten steel in the ladle. Another defect of the vibration detection method is that a difference between vibration signals in a vibration sensor which are respectively generated by the molten steel and the molten steel containing slag is not very large, which may result in missing an alarm. As a result, a slag layer in the tundish becomes too thick and the purity of the molten steel in the tundish is affected. These defects result in that slag alarm signals provided by the electromagnetic detection method and the vibration detection method can only prompt an operator to manually stop the flowing of the molten steel containing slag from the ladle into the tundish. But the delay of the manual operation with respect to the slag alarm signal further increases the amount of slag flowing from the ladle into the tundish.

SUMMARY OF THE INVENTION

In view of the above, embodiments of the present invention provide an apparatus and a method for detecting and controlling slag in molten steel flowing from a ladle into a tundish via a long-nozzle, so that the apparatus can be installed conveniently, has long lifetime and will not output erroneous alarm prematurely due to affection of environment interference.
According to one aspect of the present invention, an apparatus for detecting slag in molten steel is provided, where the molten steel and slag flows from a ladle into a tundish via a long-nozzle, and density of the slag is smaller than density of the molten steel. The apparatus includes:

a sensor, adapted to obtain at least one kind of characteristic information of a surface of a molten steel coverage layer of the tundish and provide the characteristic information for a signal processor; and
the signal processor, adapted to determine whether there is slag according to the characteristic information, and output, if there is slag, a slag alarm signal, and a control signal used for stopping the molten steel and the slag from flowing from the ladle into the tundish via the long-nozzle.

Preferably, the sensor is a common optical camera apparatus or a camera apparatus sensitive to infrared ray.
Preferably, the characteristic information includes at least one of: height information of a partial surface of the molten steel coverage layer around the long-nozzle in the tundish, and brightness information of the partial surface of the molten steel coverage layer around the long-nozzle in the tundish.
Preferably, the signal processor is adapted to output a brightness alarm signal when the brightness information exceeds a pre-defined brightness threshold, and/or the signal processor is adapted to output a height alarm signal when the height information exceeds a pre-defined height threshold.
Preferably, the sensor is adapted to detect the height information according to changes of a boundary position between the long-nozzle and the molten steel coverage layer in the tundish.
According to another aspect of the present invention, a method for detecting slag in molten steel is provided, where the molten steel and the slag flow from a ladle into a tundish via a long-nozzle, and the density of the slag is smaller than that of the molten steel. The method includes: obtaining at least one kind of characteristic information of a surface of a molten steel coverage layer in the tundish;
determining whether there is slag according to the characteristic information; and
if there is slag, outputting a slag alarm signal, and a control signal used for stopping the molten steel and the slag from flowing into the tundish from the ladle via the long-nozzle.
Preferably, the characteristic information includes at least one kind of: height information of a partial surface of the molten steel coverage layer around the long-nozzle in the tundish, and brightness information of the local surface of the molten steel coverage layer around the long-nozzle in the tundish. Preferably, a brightness alarm signal is output when the brightness information exceeds a pre-defined brightness threshold, and a height alarm signal is output when the height information exceeds a pre-defined height threshold.
Preferably, the height information is detected according to changes of a boundary position between the long-nozzle and the molten steel coverage layer in the tundish.
Embodiments of the present invention provide an apparatus and a method for detecting slag flowing from the ladle into the tundish which can be installed conveniently, has long lifetime and will not output erroneous alarm prematurely due to affection of environment interference.

BRIEF DESCRIPTION OF THE DRAWINGS

Drawings herein are used for facilitating further understanding of the present invention and form a part of the present invention. The exemplary embodiments and descriptions of the present invention are used for understanding the present invention and are not for use in limiting the protection scope of the present invention. In the drawings,

FIG.1 is a block diagram illustrating an apparatus for detecting and controlling slag in molten steel flowing from a ladle into a tundish via a long-nozzle according to an embodiment of the present invention;
FIG.2 is a flowchart illustrating a method for detecting and controlling slag in molten steel flowing from the ladle into the tundish via the long-nozzle according to an embodiment of the present invention; and
FIG.3 is a schematic diagram illustrating detailed applications of the apparatus for detecting and controlling slag in molten steel flowing from the ladle into the tundish via the long-nozzle according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in further detail hereinafter with reference to accompanying drawings and embodiments to make the technical solution and merits therein clearer.
In one embodiment of the present invention, a sensor is used to measure rising of height and intensifying of brightness of a partial surface of a molten steel coverage layer in the tundish near the long-nozzle of the ladle sticking into the molten steel in the tundish. A signal processor processes a sensor signal, and provides a slag alarm signal and a control signal used for driving a slider to close the nozzle of the ladle according to the degree that the local surface of the molten steel coverage layer in the tundish rises and its brightness intensifies.
In one embodiment of the present invention, the slag flowing from the ladle into the tundish is detected according to two parameters including height and brightness. A sensor is used for detecting signals of the two parameters, wherein the sensor is installed at an area faraway from a high temperature area, thus has long lifetime and can be installed conveniently. The signal processor respectively processes the two signals and gives out independent alarm signals according to respective processing results. The methods based on the two parameters respectively make up each other to increase an alarming ratio. Since the density of the slag is only 1/3 of that of the molten steel, the slag flowing into the tundish from the ladle will float upward around the long-nozzle of the ladle. Thus, a partial area of the molten steel coverage layer in the tundish will rise firstly. And the rising is much higher than fluctuation caused by the force of the flowing of the molten steel from the ladle into the tundish. Thus, a slag alarm signal can be given in real time. Then, the fiery-red slag breaks the surface of the molten steel coverage layer in the tundish, and the brightness is intensified suddenly. Therefore, a reliable slag alarm signal can be output. The rising of the surface of the molten steel coverage layer in the tundish may be detected 0.6s earlier than the intensifying of the brightness. When the slag alarm signal is given, a control signal which drives a slider to close the nozzle of the ladle is given at the same time. The high reliability of the height alarm signal, the high reliability of the brightness alarm signal, and a high alarm ratio brought out by the cooperation of the two methods are technical basis for closing the nozzle of the ladle by the slider under the control of the alarm signals.
Preferably, a traditional camera apparatus may be used to detect the rising of the height and the intensifying of the brightness of the local surface of the molten steel coverage layer in the tundish due to the floating of the slag flowing out from the ladle.
The brightness of the slag relative to that of the molten steel is more explicit in an infrared band. Therefore, recognizing ability of the ladle slag detecting apparatus can be improved when a camera apparatus which is sensitive to infrared ray is applied.
When a slag detection technique is adopted to reduce the slag flowing from the ladle, the molten steel coverage layer in the tundish may be relatively thin. Under this circumstance, due to the impact of the shaking of the long-nozzle, the molten steel coverage layer in the tundish may form a molten bright circle around the long-nozzle. The circle is a breach for the slag in the molten steel flowing from the ladle into the tundish to break through the molten steel coverage layer in the tundish under the buoyancy force of the molten steel. Therefore, the molten circle and its surroundings rise at first and then break through the local surface of the coverage layer, thus the brightness is intensified suddenly.
FIG.1 is a block diagram illustrating an apparatus for detecting and controlling slag in molten steel flowing from a ladle into a tundish via a long-nozzle according to an embodiment of the present invention. As shown in FIG.1 , according to the embodiment of the present invention, the apparatus for detecting and controlling the slag in the molten steel flowing from the ladle into the tundish via the long-nozzle includes: a sensor 102, adapted to obtain at least one kind of characteristic information of a surface of a molten steel coverage layer in the tundish and provide the characteristic information for a signal processor 104; the signal processor 104, adapted to determine whether there is slag according to the characteristic information and output, if it is determined that there is slag, an alarm signal and a control signal used for stopping the molten steel and the slag from flowing from the ladle into the tundish via the long-nozzle; wherein the molten steel and the slag flow from the ladle into the tundish via the long-nozzle, and the density of the slag is smaller than that of the molten steel.
The sensor 102 may be a traditional optical camera apparatus or a camera apparatus sensitive to infrared rays.
The characteristic information includes at least one kind of the following information: height information of a partial surface of the molten steel coverage layer around the long-nozzle in the tundish, and brightness information of the local surface of the molten steel coverage layer around the long-nozzle in the tundish.
The signal processor 104 gives out a brightness alarm signal when the brightness information exceeds a pre-defined brightness threshold.
The signal processor 104 gives out a height alarm signal when the height information exceeds a pre-defined height threshold.
The sensor detects the height information according to changes of a boundary position between the long-nozzle and the surface of the molten steel coverage layer in the tundish.
FIG.2 is a flowchart illustrating a method for detecting and controlling slag in molten steel flowing from a ladle into a tundish via a long-nozzle according to an embodiment of the present invention. As shown in FIG.2 , the method for detecting and controlling the slag in the molten steel flowing from the ladle into the tundish via the long-nozzle according to the embodiment of the present invention includes the following steps.
Step S202, at least one kind of characteristic information of a surface of a molten steel coverage layer in the tundish is obtained.
Step S204, it is determined whether there is slag according to the characteristic information.
Step S206, if it is determined that there is slag, an alarm signal and a control signal for stopping the molten steel and the slag from flowing from the ladle into the tundish via the long-nozzle are output.
The molten steel and the slag flow from the ladle into the tundish via the long-nozzle, and the density of the slag is smaller than that of the molten steel.
The characteristic information includes at least one kind of the following information: height information of a partial surface of the molten steel coverage layer around the long-nozzle in the tundish, and brightness information of the local surface of the molten steel coverage layer around the long-nozzle in the tundish.
In step S206, a brightness alarm signal is output when the brightness information exceeds a pre-defined brightness threshold. In step S206, a height alarm signal is output when the height information exceeds a pre-defined height threshold.
In step S202, the height information may be detected according to changes of a boundary position between the long-nozzle and the surface of the molten steel coverage layer in the tundish.
In one embodiment of the present invention, an apparatus for detecting slag in molten steel flowing from a ladle into a tundish via a long-nozzle is provided. The apparatus includes a sensor used for observing the surface of the molten steel coverage layer in the tundish and a signal processor, wherein the sensor detects the rising of the height and the intensifying of the brightness of the local surface of the molten steel coverage layer around the long-nozzle which sticks into the molten steel in the tundish from the ladle. The signal processor respectively processes a height signal and a brightness signal, and respectively gives out a height alarm signal and a brightness alarm signal indicating that there is slag and gives out a control signal used for driving the slider to close the nozzle of the ladle. The sensor used for observing the surface of the molten steel coverage layer in the tundish may be a traditional optical camera apparatus or a camera apparatus sensitive to infrared ray.
The sensor used for observing the surface of the molten steel coverage layer in the tundish may detect the rising of the local surface of the molten steel in the tundish according to changes of the boundary position between the long-nozzle and the surface of the molten steel coverage layer in the tundish.
FIG.3 is a schematic diagram illustrating detailed applications of the apparatus for detecting slag in the molten steel according to an embodiment of the present invention. As shown in FIG.3 , it is a system diagram of a detecting apparatus for detecting slag when molten steel 4 in a ladle 3 flows from bottom of the ladle 3 into molten steel 9 in a tundish 7 via a long-nozzle 6. When the molten steel containing the slag flows into the molten steel 9 in the tundish, the slag will float upwards due to buoyancy force, which makes the local surface of a molten steel coverage layer 8 in the tundish around the long-nozzle 6 rise and finally break through the local surface of the coverage layer 8. Thus, brightness is intensified. A camera (sensor) 1 observes the surface of the molten steel coverage layer 8 in the tundish around the long-nozzle 6 and the long-nozzle 6 near the molten steel coverage layer 8. A signal processor 2 processes an observed signal from the camera 1 and respectively gives out a height alarm signal and a brightness alarm signal, and gives out a control signal used for driving a slider 5 of the ladle to close the nozzle of the ladle in real time.
The shaking of the long-nozzle 6 makes the molten steel coverage layer 8 form a molten circle around the long-nozzle 6. When the slag flowing into the molten steel 9 floats upwards, the molten circle becomes a breach for the slag to break through the molten steel coverage layer 8 in the tundish. Thus, the circle and its surroundings will rise firstly and then become brighter. And a large area of fiery-red slag will emerge around the circle. The molten circle and the mixed liquid of the slag and the molten steel at the local surface of the coverage layer 8 are relatively bright whereas the long-nozzle 6 is relatively dark. Thus, the boundary P in FIG.3 between the long-nozzle and the circle can be recognized easily. When the local surface of the molten steel coverage layer 8 in the tundish around the long-nozzle 6 rises, an elevation angle α 10 of the boundary P observed by the camera 1 will become larger. The rising of the local surface of the molten steel coverage layer 8 may be detected according to the changes of the elevation angle α 10. At the same time, the camera 1 measures the intensifying of the brightness of the local surface of the coverage layer. The signal processor 2 respectively gives out alarm signals, and gives a control signal to drive the slider 5 of the ladle to close the nozzle of the ladle according to the rising of the height and the intensifying of the brightness.
The foregoing descriptions are only preferred embodiments of this invention and are not for use in limiting the protection scope thereof. Any changes and modifications can be made by those skilled in the art without departing from the spirit of this invention and therefore should be covered within the protection scope as set by the appended claims.

Claims

An apparatus for detecting and controlling slag in molten steel, wherein the molten steel and slag flows into a tundish from a ladle via a long-nozzle, and density of the slag is smaller than density of the molten steel, the apparatus comprises:
a sensor, adapted to obtain at least one kind of characteristic information of a surface of a molten steel coverage layer of the tundish and provides the characteristic information for a signal processor; and

the signal processor, adapted to determine whether there is slag according to the characteristic information, and output, if there is slag, a slag alarm signal, and a control signal used for stopping the molten steel and the slag from flowing into the tundish from the ladle via the long-nozzle.
The apparatus of claim 1, wherein the sensor is a common optical camera apparatus.
The apparatus of claim 1, wherein the sensor is a camera apparatus sensitive to infrared ray.
The apparatus of claim 1, wherein the characteristic information comprises at least one of: height information of a partial surface of the molten steel coverage layer around the long-nozzle in the tundish, and brightness information of the partial surface of the molten steel coverage layer around the long-nozzle in the tundish.
The apparatus of claim 4, wherein the signal processor is adapted to output a brightness alarm signal when the brightness information exceeds a pre-defined brightness threshold.
The apparatus of claim 4 or 5, wherein the signal processor is adapted to output a height alarm signal when the height information exceeds a pre-defined height threshold.
The apparatus of claim 4, wherein the sensor is adapted to detect the height information according to changes of a boundary position between the long-nozzle and the molten steel coverage layer in the tundish.
A method for detecting slag in molten steel, wherein the molten steel and the slag flow from a ladle into a tundish via a long-nozzle, and the density of the slag is smaller than that of the molten steel, the method comprises:
obtaining at least one kind of characteristic information of a surface of a molten steel coverage layer in the tundish;

determining whether there is slag according to the characteristic information; and

if there is slag, outputting a slag alarm signal, and a control signal used for stopping the molten steel and the slag from flowing into the tundish from the ladle via the long-nozzle.
The method of claim 8, wherein the characteristic information comprises at least one kind of: height information of a partial surface of the molten steel coverage layer around the long-nozzle in the tundish, and brightness information of the local surface of the molten steel coverage layer around the long-nozzle in the tundish.
The method of claim 9, wherein a brightness alarm signal is output when the brightness information exceeds a pre-defined brightness threshold.
The method of claim 9 or 10, wherein a height alarm signal is output when the height information exceeds a pre-defined height threshold.
The method of claim 9 or 10 or 11, wherein the height information is detected according to changes of a boundary position between the long-nozzle and the molten steel coverage layer in the tundish.