catalogue search
P. 01
P. 02
P. 03
|
|
|
You may also be interested in
Design software, Simulation software, CFD software, Management software, Software
Text version of the page
| | |||||
| Is.ESI Group IHE VIRTUAL TRY-OUT SfAtE' COHJ>ANY Influences of Solidification Length and Pressure Intensification on Gas Shrinkage Microporosity in Casting Components | |||||
| | |||||
| introduction | in the solid phase, solidification induces gas micro-segregation (thick curve) in the remaining liquid part. If the gas concentration in the liquid phase reaches the gas solubility limit decreasing with liquid pressure and temperature (thin curve), some micropores nucleate deeply in the mushy zone. If the situation is such that all these mechanisms are involved, the microporosity is called gas shrinkage microporosity. Gas shrinkage microporosity can not be modelled with the traditional approaches used in commercial softwares to calculate the fraction of pure shrinkage microporosity encountered in closed mushy zones: for this last porosity family, the final porosity fraction is locally simply equal to the solidification shrinkage volume, because no liquid flux can partially compensate the shrinkage (closed system). | ||||
| Porosity in castings is a major defect since it affects the mechanical properties. In particular porosities are sites for the initiation of fatigue cracks. Therefore, the reduction of porosity fraction and size, the control of porosity distribution and morphology are crucial for the optimization of mechanical resistance of as cast components. | |||||
| | |||||
| m Figure 1. Concomitantmechanismsresponsible for microporosityformation. As depicted in figures l.a and l.b, in general microporosity is the result of two concomitant mechanisms: (a) solidification shrinkage induces a suction and thus a liquid pressure drop (p| curve) in the permeable mushy zone (Darcy's law), (b) trace gaseous elements in the liquid being generally less soluble | New model As a consequence, the prediction of porosity is not straightforward in general. This is the reason that conducted CALCOM-ESI and the Swiss Federal Institute of Technology in Lausanne (EPFL) (in collaboration with several leading casting industries) to the development of a microporosity numerical model based on the previously described mechanisms (see the original scientific paper^). This model has been recently extended to all kind of industrial alloys (Al, Fe, Cu, Mg, Ni, Ti base alloys. See scientific paper*!) in order to predict all porosity families in complex geometrical situations: - gas-shrinkage microporosity, - pure-shrinkage microporosity, - macroporosity, - pipe-shrinkage. This work leads to a software customized for all casting processes: - gravity casting, - high pressure die casting, - investment casting, - continuous casting, | ||||
| ■ | |||||
| | |||||
| | www. esi-group.com www. calcom.ch | | |||
| | |||||