The High Temperature Deformation Behaviour of Bentonite Bonded Sands and Possibilities for their Influence - New Results

摘要

The methods for testing of moulding materials are working mostly nearly at room temperature. Examples for these testing procedures are the different green strengths or the wet tensile strength. The results of these tests we can use for control 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 haven't suitable testing equipment or procedures. We haven't also no informations to specific sand related casting defects from the important steps of the casting production 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. It analyzes the strengths and the deformation of different green sand mixtures (different binders and additives) in the temperature range between room temperature and 1000 °C. With the used testing equipment it's possible to show force - way - curves at different testing temperatures and to calculate the strengths. Images of the fracture behaviour of the samples give informations to the deformation and fracture type (more plastic or more brittle) of the different sand mixes. The investigations show, that the high temperature deformation behaviour and also the hot and the residual strengths are depend from the used sand mix. With these knowledge it's possible to influence the casting process, to avoid some casting defects and to have a better casting quality.