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Possibilities of Bifilm Amount Reduction in Al Castings by Gating System Design Optimization

Brůna Marek, Galčík M., Sládek A., Martinec D.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 2

549--559

EN

Submitted work deals with the possibilities of reducing reoxidation by improved gating system design. The result of the reoxidation is the of furled oxide layers - bifilms. During experimental works, non-pressurized and naturally pressurized gating systems designs were introduced and evaluated. Mechanical properties, fracture area, hot tearing index, bifilm index and EDX analysis were used during evaluation. Paper aim is also to clarify the reoxidation phenomenon by visualization with the aid of ProCAST numerical simulation software. Achieved results clearly confirmed the positive effect of the naturally pressurized gating system, main emphasis needs to focus on finding the proper way to reduce the melt velocity. By using vortex element extension at the end of the runner was achieved positive results in term of reoxidation suppression.

2

Using of Technology Semisolid Squeeze Casting by Different Initial States of Material

Martinec D., Pastirčák R., Kantoríková E.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 1

117--121

EN

The paper deals with the effect of heating of various prepared batch materials into semisolid state with subsequent solidification of the cast under pressure. The investigated material was a subeutectic aluminium alloy AlSi7Mg0.3. The heating temperature to the semisolid was chosen at 50% liquid phase. The used material was prepared in a variety of ways: heat treatment, inoculation and by squeeze casting. Also the influence of the initial state of material on inheritance of mechanical properties and microstructure was observed. The pressure was 100 MPa. Effect on the resulting casting structure, alpha phase distribution and eutectic silicon was observed. By using semisolid squeeze casting process the mechanical properties and microstructures of the casts has changed. The final microstructure of the casts is very similar to the microstructure that can be reached by technology of thixocasting. The mechanical properties by using semisolid squeeze casting has been increased except the heat treated material.

3

Application of Modular Die for Fluidity Test and Monitoring of the Pressing Force Flow by Semi-solid Squeeze Casting of AlSi7Mg0.3

Martinec D., Pastirčák R.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 3

69--73

EN

The fluidity is the term to determine the materials ability to fill the mold cavity properly. Fluidity is complex property with many variables. Up to this date, there is no methodology for defining the fluidity in a semisolid material state. Submitted paper deals with the proposal of a new method designed for aluminium alloy fluidity evaluation in semi-solid state trough the design of the layered construction die. Die will be primary used for fluidity tests of semi-solid squeeze casted aluminium alloy and to observe the pressing force flow by mentioned casting technology. The modularity consists of possibility to change each die segment. In the experiment the die design was evaluated by simulation in ProCAST 11.5 and by production of experimental castings. The die was made by laser cutting technology from construction steel S355JR. Experimental material was aluminium alloy AlSi7Mg0.3. The temperature of the semisolid state was chosen to achieve 35% of solid phase. The result of next study should be a selected parameters observation and their effect on the fluidity of aluminium alloy in semi-solid state. This will be very important step to determine the optimal conditions to achieve a castings with certain wall thickness produced by the method of semi-solid squeeze casting.