Electricity: measuring and testing – Magnetic – Fluid material examination
Patent
1986-06-24
1989-03-28
Eisenzopf, Reinhard J.
Electricity: measuring and testing
Magnetic
Fluid material examination
324232, 324226, 324243, G01N 2774, G01N 2772, G01R 3312
Patent
active
048167584
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for the detection of slag co-flowing within a stream of molten metal, more particularly, in molten steels as they are being poured from metallurgical vessels.
As steel is being poured from converters, ladles or tundishes, a layer of slag lies on the surface of the molten metal. For metallurgical reasons, an effort is made to pour out as little slag as possible. In general, the following methods for preventing the outflow of slag are known:
In a ladle, the approximate point in time at which the slag can flow out is determined. For this purpose, the ladle is weighed in its empty and full state in order to determine the amount of molten metal remaining in each case. After the reading on the scale indicates that the amount of material has dropped to critical levels, the outflow of slag is determined visually by the operating personnel.
Aside from the fact that the detection of the remaining quantity of molten metal can be determined only very imprecisely, since it depends on the degree of erosion of the ladle lining, this method is cumbersome, especially if the pouring is done under a protective gas, which is generally the case with high-grade steels. This is because part of the shielding needs to be removed so that the pouring stream can be observed. This requires a considerable effort in terms of mechanical engineering and is also detrimental to quality.
In another method, visual monitoring is eliminated, the pouring being discontinued when a certain filling level in the ladle is reached.
This method is uneconomical, because a residue of molten metal always remains in the ladle and later needs to be melted down.
SUMMARY OF THE INVENTION
Therefore, the invention has for its object the provision of a method by which the presence of a small quantity of slag in the molten metal flowing out can be detected and displayed without requiring the removal of the shielding for the pouring stream, or interference with the pouring.
The temperatures of the molten metal and of the measuring transducers must be continually monitored. Temperature measurements are old in the art. This determination is particularly simple if from the ohmic resistances of coils one can assess the temperatures of the measuring transducers and, hence, the temperature of the molten metal. Heat propagation in the system itself can be calculated once the material characteristics have been determined in the usual manner.
The value of the electrical conductivity, which is used to calculate the distribution of the slag from the measured values of the voltage spectrum, can be corrected with the measured temperature values.
By using a reference setup likewise consisting of a transmitter coil and a receiver coil, the two transmitter coils being series-connected and the two receiver coils being inverse-parallel, the sensitivity can be increased considerably.
Another embodiment of the invention provides for an additional winding on the transmitter coil of the reference setup, to which a current which varies in magnitude and phase position is applied frequency-selectively, so that the the total voltage of the receiver coil becomes or approximates zero for all frequencies.
Therefore, to further reduce the effect of temperature, another embodiment of the invention provides for the use of a coil arrangement coaxially surrounding the flow section and consisting of two transmitter coils and one receiver coil, which are spaced a radial distance from each other, or for the operation of a coil arrangement in such a way that the axes of the transmitter and receiver coils are arranged radially around the test item with the same radial distance from the test item and the transmitter coils lie outside the base corners of an isosceles triangle, the voltage induced in the receiver coil being adjusted to zero by appropriate feeding of the currents to the transmitter coil.
Preferably, the signals from the measuring coils are measured by means of phase-sensitive rectifiers, and the eval
REFERENCES:
patent: 4279149 (1981-07-01), Block
patent: 4529029 (1985-07-01), Block
Block Franz R.
Julius Edmund
Theissen Wolfgang
AMEPA Angewandte Messtechnik und Prozessautomatisierung GmbH
Eisenzopf Reinhard J.
Snow Walter E.
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