ISSUE 4/2013

/// 03
Polzin, H.; Tilch, W.; Strehle, M. The high temperature deformation behaviour of bentonite bonded sands

The methods for testing of moulding materials are working mostly at room temperature. Examples for these testing procedures are the different green strengths or the wet tensile strength. The results of these tests we are able to use for the controlling of the behaviour of the green sand moulds in the steps mouldmaking, transport and partly also pouring. For testing of properties at higher temperature (hot compression strength, residual strength…) we often don’t have suitable testing equipment or procedures. We also got no information to specific sand related casting defects from the steps pouring, cooling, solidification and shake out. The paper shows results of investigations in the field of high temperature deformation behaviour of bentonite bonded sand systems. We analyze the strength and the deformation of different sand mixtures in the temperature range between room temperature and 1000 °C. After the investigation of different heating procedures of the used samples the following points were observed: type of bentonite, amount of bentonite, type of additives and amount of additives. With the used testing equipment it is possible to show force-way-curves at different testing temperatures. The investigation shows, that the hot temperature deformation behaviour and also the hot and the residual strength depend from the used sand mix. With that knowledge we can affect or prevent some of the casting defects occurring in our foundries.




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