Livarski vestnik 54 / 2007 Nr. 1
Karel Rusín, David Hrazdira, Miroslav Ciganek, Jiří Beneš:
Processes of Oxidation in Bentonite Sands
P. Mrvar, J. Medved, A. Jaklič:
The State of the Melt Control in Mg-Al-Mn Alloys
Janez Pristavec, Mihael Nusdofer, Mathias Bodenburg:
Prediction of the Lifetime of Dies For Die Casting by Means of Numerical Simulation
Karel Rusín, David Hrazdira, Miroslav Ciganek, Jiří Beneš
Processes of Oxidation in Bentonite Sands
Summary
A new technology of physical and chemical treatment of green sand systems, which contain water with radical oxidants, is not yet used in Czech foundries. U.S. foundries have already started to exploit Advanced Oxidation technologies with very good results. Therefore the Department of Foundry Engineering of BUT investigated the influence of radical oxidants in green sand systems. The treatment is based on the effects of oxidants and external sources of energy reacting with water and components in molding sands. Organic compounds of pyrolytic reaction of seacoal, resin binders, deactivated bentonite and other substances contaminate the molding sands. The oxidants (ozone and hydrogen peroxide) in ultrasonically agitated water, added to bentonite sand by mulling, will react with and destroy these deposits. This „cleaning“ of the particles will allow for better clay and sand particle interaction and binding with increasing the sand strength. The green compressive strength of production bentonite sand was improved up to 23 %, the performance in the molding system became better.
The introduction of the complex oxidants technique for foundry sands enables the elimination of noxious combustion products and other material originating by contact with cast metal. The AO treatment induced the reduction of benzene by 77 %, of toluene by 73%, of ethylbenzene by 91%, of m + p-xylene by 94%, of o-xylene by 95%, of naphthalene by 95% and other polyaromatic molecules by 95%. A new process is presumed to be a part of the no-waste technologies acceptable from the point of view of environmentally benign conditions in the foundry workshop (priority in EU).
The introduction of the complex oxidants technique for foundry sands enables the elimination of noxious combustion products and other material originating by contact with cast metal. The AO treatment induced the reduction of benzene by 77 %, of toluene by 73%, of ethylbenzene by 91%, of m + p-xylene by 94%, of o-xylene by 95%, of naphthalene by 95% and other polyaromatic molecules by 95%. A new process is presumed to be a part of the no-waste technologies acceptable from the point of view of environmentally benign conditions in the foundry workshop (priority in EU).
P. Mrvar, J. Medved, A. Jaklič
The State of the Melt Control in Mg-Al-Mn Alloys
Summary
Beside the casting technology one of the main problems, which are connected with recycling and also re-melting, is presence of nonmetallic inclusions as well as no homogeneously and unbalanced chemical composition in blocs of magnesium alloys. The later have influence on a portion of intermetallic compounds such are for example in AM alloys Mg17Al12 and Al4Mn. It was find out that the different input materials with chemical composition within valid standards have consequences on different technological, thermal, physical and mechanical properties.
From foundryman point of view it is important to master and control the alloys on foundry input as well within. For those purpose recently the deep examinations are above all on AM60 alloy with different investigated methods such are chemical analyses, simultaneous thermal analyses (STA), electron microscopy (SEM), determination of mechanical properties, thermo dynamical calculations and “in situ” thermal analyses (ETA). Part of wide investigation going with purpose to develop controlling methods for state of the malt determination.
Key words: MgAlMn alloy, solidification process, the state of the melt control, non-metallic inclusions and inter-metallic compounds
From foundryman point of view it is important to master and control the alloys on foundry input as well within. For those purpose recently the deep examinations are above all on AM60 alloy with different investigated methods such are chemical analyses, simultaneous thermal analyses (STA), electron microscopy (SEM), determination of mechanical properties, thermo dynamical calculations and “in situ” thermal analyses (ETA). Part of wide investigation going with purpose to develop controlling methods for state of the malt determination.
Key words: MgAlMn alloy, solidification process, the state of the melt control, non-metallic inclusions and inter-metallic compounds
Janez Pristavec, Mihael Nusdofer, Mathias Bodenburg
Prediction of the Lifetime of Dies For Die Casting by Means of Numerical Simulation
Summary
Program packages for the simulation of casting processes cover more and more aspects of the production cycle of castings and their further treatment. During the last years the basic capabilities of simulation packages - visualization of filling of the mold cavity, solidification of the melt and evaluation of these two phases with different criterions - have been extended by various new possibilities of analysis, finally aiming at covering the complete development and production cycle from planning till the end of the product. One of these developments is the analysis of stresses and strains in dies and castings. By modelling the complete die and the heating and cooling channels including all process steps such as spraying and blowing of the die it is possible to monitor the thermal loads and the resulting stresses during the process of casting, solidification and further down-cooling. The obtained results of the simulation allow the prediction of optimal process parameters, assuring a suitable heat balance of the die throughout the process and in this sense of course a long lifetime of the die and lower costs of operation.
The presented case illustrated the application of the simulation of stress formation in the die to prevent early crack formation on the die surface. The analysis of the process showed that large stress oscillations appeared with large amplitudes that promote very much the formation of cracks, specially in the die regions with small radii. As this is very important for the quality of the casting surface, the goal was to find out a suitable solution.
Key words: Simulation of aluminium die casting, heat loads of dies, surface cracks of dies, MAGMASOFT ® - MAGMAstress.
The presented case illustrated the application of the simulation of stress formation in the die to prevent early crack formation on the die surface. The analysis of the process showed that large stress oscillations appeared with large amplitudes that promote very much the formation of cracks, specially in the die regions with small radii. As this is very important for the quality of the casting surface, the goal was to find out a suitable solution.
Key words: Simulation of aluminium die casting, heat loads of dies, surface cracks of dies, MAGMASOFT ® - MAGMAstress.