Thermal measuring and testing – Temperature measurement – Of molten metal
Patent
1998-08-26
2000-08-22
Bennett, G. Bradley
Thermal measuring and testing
Temperature measurement
Of molten metal
374121, 374140, 374157, G01K 112, G01K 108, G01K 104
Patent
active
061061506
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for measuring the melt temperature in a melt vessel by using optical pyrometry.
In the foundry industry it is often desirable to be able to determine in which matrix structure a certain molten metal alloy will solidify. One way of carrying out such determinations is to perform a thermal analysis of the melt. A small but representative sample of the molten metal alloy is taken and is allowed to solidify. During this process, the temperature is measured as a function of time. The final matrix structure is then determined by comparing the obtained cooling curve and its time derivative with reference curves. Such thermal analysis methods are disclosed in e.g. WO86/01755 (SC101), WO91/13176 (SC108) and WO92/06809 (SC104).
In the above mentioned method, a sample of molten metal is obtained by immersing the sample vessel into the bulk metal after which said sample is allowed to solidify. The thermal analysis is performed by using temperature responsive means, normally thermocouples. In order to improve the accuracy of the solidification analysis, WO 86/01755 teaches a method in which two thermocouples are used. One thermocouple is positioned in the centre of the vessel and the other near the vessel wall.
It is often difficult to perform accurate temperature measurments close to the wall of the sample vessel. The physical dimensions of thermocouples require that they be located at least 1.5 mm away from the wall to ensure that the molten iron can flow between the thermocouple tip and the vessel wall. Due to the presence of insulation surrounding the tip of the thermocouple (to protect the hot junction), the practical result is that the "wall" temperature is actually being measured at a location which is more than 2 mm away from the wall itself.
This constitutes a limitation to WO 86/01755, since it is known that the most accurate measurement of the undercooling of a melt is measured directly from the wall itself, where the iron first begins to solidify. The displacement of the conventional thermocouple from the wall surface results in the bulk-metal behavior influencing the temperature registered by the thermocouple and detracts from the accuracy of the measurement. Furthermore, the thermocouple itself constitutes both a heat sink and a wall surface which can influence the solidification behaviour relative to a pure sample.
Sometimes, it is desirable to at least partially coat the wall of the sample vessel with certain chemicals affecting the solidification behavior of the melt. Then, in order to thermally investigate the influence of the coatings on the melt, it is also necessary to be able to measure the temperature close to the wall and not 1-2 mm from the wall. If the measurements are performed too far away from the wall, the coatings can become diffused or diluted and hence, the thermal analysis will not have the required accuracy.
Also, because of the opaqueness of the molten metal, it is not possible to ensure that the thermocouple is reproduceably arranged in each sampling vessel. Another drawback of conventional thermal analysis using thermocouples is that the immersion thermocouples are destroyed during the measurements and hence, they can only be used once. In order to perform accurate measurements which can be reliably compared to reference values, it is necessary that the quality of the consummable thermocouples is very uniform. The destruction of these uniform quality thermocouples during measuring results in high costs. Furthermore, the avoidance of consumable thermocouples simplify the recycling of the sample vessel.
Consequently, there is a need for improved methods for carrying out the thermal analysis procedure.
EP-A2-0 160 359 relates to an apparatus for measuring the bath temperature of metallurgical furnaces through a tuyere. A periscope is used for inserting a fiber optic cable into a tuyere body. The cable is protected from the molten metal by letting air flow through the tuyere and out in the bath.
EP-A2-0 245 010 describes a submersible probe for
REFERENCES:
patent: 3446074 (1969-05-01), Thomas
patent: 3570277 (1971-03-01), Dorr et al.
patent: 3626758 (1971-12-01), Stewart et al.
patent: 3747408 (1973-07-01), Stanworth et al.
patent: 4002069 (1977-01-01), Takemura et al.
patent: 4216028 (1980-08-01), Kurita
patent: 4444516 (1984-04-01), Dostoomian et al.
patent: 4568199 (1986-02-01), Schmidt
patent: 4995733 (1991-02-01), Thomas et al.
patent: 5037211 (1991-08-01), Nakashima et al.
patent: 5577841 (1996-11-01), Wall
patent: 5733043 (1998-03-01), Yamada et al.
patent: 5839830 (1998-11-01), Young et al.
Lindholm Ragnar
Thoren Mikael
Bennett G. Bradley
Sinter-Cast AB
Verbitsky Gail
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