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2011-Sustainable Industrial Processing Summit
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| Editors: | Florian K |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2012 |
| Pages: | 630 pages |
| ISBN: | 978-0-9879917-2-0 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
Comparison Of High Temperature Methods For The Investigation Of Melting And Crystallisation Behaviour Of Mould Powders
Nathalie Koelbl1; Irmtraud Marschall2; Harald Harmuth2; Bernd Buchberger3;1MONTANUNIVERSITAET LEOBEN, Leoben, Austria; 2MONTANUNIVERSITAET LEOBEN, 8700 Leoben, Austria ; 3RHI AG, 8700 Leoben, Austria ;
Type of Paper: Regular
Id Paper: 354
Topic: 6
Abstract:
Mould powders with a C/S-ratio between 0.61 and 1.34 were investigated with respect to their melting and crystallisation behaviour. Therefore the Hot Stage Microscope (HSM), Simultaneous Thermal Analysis (STA) and Single Hot Thermocouple Technique (SHTT) were used. With the STA differences in enthalpy according to the reactions taking place during heating and cooling are detected. Contrary the HSM enables the in-situ observation of a polished sample during heating. Crystallisation of transparent slags can be investigated with the HSM and the SHTT. For the SHTT the slag is stretched to a thin layer. Therefore the evaporation of alkalis and fluorine has to be taken into account.Some differences between the results of the methods applied are caused by the following circumstances: Thermocouple measures rather the furnace temperature in case of STA and the specimen temperature in case of HSM and SHTT. Furthermore for detection of effects in the DTA-curve more intense reactions have to take place. Also the higher magnification factor of the HSM compared to the SHTT for continuous cooling measurements has impact on the deviation of especially the crystallisation temperature.Using the HSM for some mould powders the formation of intermediate liquid with following crystallisation is observed during heating. This leads to the assumption of disequilibrium due to a too high heating rate. In contrast to this detection of intermediate phases by STA is hindered by overlap of peaks.Using the HSM during cooling diverse crystal shapes are observed. On the contrary the results of the SHTT show the crystallisation of denrites for continuous cooling and isothermal measurements at high temperatures. But for lower temperatures small crystals precipitate in the whole sample.Comparing results of these methods with mineralogical investigations of samples taken from service analogies are observed.