Measuring and testing – Sampler – sample handling – etc. – Sample holder
Patent
1997-07-25
1999-09-07
Williams, Hezron
Measuring and testing
Sampler, sample handling, etc.
Sample holder
374139, 374157, G01N 3700
Patent
active
059490004
DESCRIPTION:
BRIEF SUMMARY
INTRODUCTION
The present invention relates to a sampling device for thermal analysis of solidifying metal, comprising a container intended to contain a sample quantity of liquid metal during analysis, and at least one sensor for thermal analysis, the sensor(s) being intended to be immersed in the solidifying metal sample quantity during analysis. The invention also relates to the sample container of the sampling device. The device and container are primarily intended for thermal analysis in connection with production of cast iron, in particular in connection with production of Compacted Graphite Iron, below abbreviated as CGI.
TECHNICAL FIELD
Thermal analysis is a technique which monitors the variations in the temperature change of certain molten substances during solidification in order to determine the microstructure and hence properties of the substances in solid form. This is basically accomplished by taking a sample from a melt, bringing it into a test vessel and recording and evaluating the time-dependent temperature change in the sample during solidification, by means of temperature responsive means, such as thermocouples or pyrometers or other such devices known to a person skilled in the art.
When using thermal analysis for controlling solidification processes in molten materials such as cast-iron, e.g. CGI, or aluminium alloys, a most critical issue is to quickly bring the test vessel and the sample as close to thermal equilibrium as possible, and to provide for a controlled, even and reproducible rate of heat removal from the sample. The reason for this is to make it possible to measure temperature changes during phase transformations, e.g. supercooling and latent heat evolved during the nucleation and growth of primary and secondary solidification phases, the knowledge of which is essential in order to control certain solidification processes.
BACKGROUND ART
One technique to establish thermal equilibrium and to achieve a controlled heat removal rate is taught by SE 350,606 and comprises immersing the sampling vessel in a molten bath of the metal to be analyzed or heating the vessel in some other way, in order to establish thermal equilibrium between the sampling vessel and its contents at a temperature above the temperature of crystallisation prior to commencement of the cooling process of the thermal analysis. A sampling vessel adapted for this technique is also disclosed, that vessel being made of graphite, for use in aluminium melts, or made of a ceramic material, when intended for use in melt cast iron.
Another sampling vessel for thermal analysis, though only directed at aluminium alloys, is disclosed in DK-B-150,996. That vessel comprises a small crucible of steel sheet, provided with a plug of thermally insulating material, e.g. core sand, at the bottom.
Apart from the vessels mentioned above, there are several other sample vessels of the similar kind occuring in the art. A common drawback for these vessels is that they all are made of, or comprise as an essential part, materials such as graphite, furan sand, core sand or refractory cement; these materials are all known to be difficult to work. The available manufacturing techniques are slow and have considerable quality problems due to the nature of the material. Although it would be desirable to provide for various vessel features, giving a variety of different heat removal characteristics, in order to produce sampling vessels adapted for thermal analysis of different metals and alloys, this has hitherto not been possible, since the limited choice of materials for producing such vessels has seriously restricted the latitude to select among these characteristics. Likewise, it has been difficult to provide sampling vessels that give cooling rates that are sufficiently accurate and repeatable to fulfil the requirements of thermal analysis, due to the constricted selection of characteristics obtainable.
Regarding the sampling vessels of immersion type, i.e. the ones that are immersed in the bulk of the melt metal when sampling, a sp
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E. Schurmann, et al., "Prinzip Und Probleme Der Thermischen Analyse Einer Kleinen Im Sandtiegel Erstarrenden Legierten Metallprobe", Giesserei, vol. 76, No. 9, May 1989, pp. 287-297.
Lindholm Ragnar
Lindholm Torsten
Popelar Patrik
Thoren Mikael
Fayyaz Nashmiya
Sinter-Cast AB
Williams Hezron
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