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Hajas Gergely

General manager, Alu-Öntő Ltd.

Prototypes Made of Sand Moulds for Thin-Walled and Detailed Die Cast Parts

| Author / Editor: Gergely Hajas / Alexander Stark

There is a new patented casting technology for the manufacturing of aluminum gravity sand mould casts with large geometries and thin walls.

Demand for cast aluminium products in the automotive industry remains high.
( Source: Pixabay / CC0 )

The demand for parts with large surfaces and thin walls produced by pressure casting technology is increasing. This is because the automotive industry is looking for ways to reduce the weight of the castings and, consequently, their wall thickness. At the same time, they demand increased strength properties. For example, aluminum castings for car body parts, require the same strength properties from the welding process as the pressure shaped components, in particular with regard to high residual deformability.

The castings of the body parts are characterized by uniformly thin, typically 2 mm thick rib-reinforced structures, which require the testing and optimization of prototype and pre-cast parts. Due to the high initial costs of pressure casts, it is more advantageous to produce the castings by means of gravity sand mould casting technology. A prerequisite is, however, that the required sizes, surface qualities and the strength properties can be produced. A patented casting technology (Registration number 230620 (EU: PCT/HU2016050019, US: US20170333981A1)) can meet these specifications. The results of the part processesing have been proven in several reference works as well as by the results of model experimentation and casting simulation [1].


The aim of the experiments during the manufacturing of a thin walled hpdc casting prototype is to investigate the effect of the factors influencing the forming conditions and the strength properties of the gravitational sand casting technology.

The automotive sector is looking for ways to reduce weight of the castings.
The automotive sector is looking for ways to reduce weight of the castings.
( Bild: gemeinfrei / CC0 )

During the experiments, furan resin sand molds with 1.5 to 2.0 to 2.5-3 mm to 3.5 mm wall thickness were cast and their technological properties, the casting temperature, the number and height of the standings, the geometry of the gating system, melt degassing treatment was determined. The chemical composition of the applied AlSi10Mg and AlSi10MnMg is shown in table no.1. During treatment of the melt degassing, a specific quantity of AlSr10 and AlTi5B1 auxiliary alloy was added.

Simulation and experimental results of mould filling

The mould-filling conditions were studied in the NovaFlow & Solid simulation software at the University of Miskolc's Faculty of Theoretical Engineering and compared with the cast samples. Figure 1 shows the simulation of a defective mould filling. Complete filling of the 1.5 mm thick layer was only reached when there was a direct connection to the stand (Figure 2).

Determination of strength properties

The strength properties of plate castings were determined using cast and heat-treated specimens with 2 mm thick walls.

Table 2. Strength properties of sample parts with 2 mm thick plates
Table 2. Strength properties of sample parts with 2 mm thick plates
( Source: Hajas )

Table 2 shows the effect of different casting parameters applied to the samples and the changes to the strength properties.

Characteristics related to the condition of the sample piece:

H-cast– resin-bonded sand form
K-cast– on one side using a coolant in resin-bonded sand form
Heat treated H– T7–1 480°C/160 min 230°C/120 min
Heat treated H–T7–2 510°C/300 min 150°C/60 min + 230°C/70 min

Summary

The test results showed that use of gating systems and casting technology for the production of thin-walled high pressure castings by means of sand casting requires a free-flowing filling process during short casting times.
The strength properties of thin-walled test castings using gravity sand casting comply with the requirements placed on pressure castings with alloys adapted to meet the requirements and the use of heat treatment technology.

The technological parameters of the patented process different noticeably from those of conventional gravity casting. This is because the pressure casting technology is different, too.
Typically, castings with low wall thickness and castings with large surface areas are not entirely suitable for compacting feeding, and the volume reduction occurring during solidification appears in even, flat-shaped areas in the form of center line pores, which do not significantly reduce the strength properties.

The direct economic advantage of this process is the possibility to manufacture sample casts by means of pressure casting as well as the long-term production of expensive metal tools, or small-series casts with low initial costs and during a fraction of the time required for comparable methods.


About the technology patent

Casting process for aluminum castings of divided, low wall thickness with sand casting technology, for the production by gravity casting technology

Patent owner: Alu-Öntő Kft., Gergely Hajas CEO

Hungary
Granting date of the patent in Hungary: 17. May, 2017
Classification of the patent: Category "A" - world novelty, registration number: 230620

Europe - USA
International patent published in PCT member states, publication ID: PCT/HU2016/050019, US20170333981A1
Classification of the international patent: Category "A" - world novelty
The number of international publications in the gazette of international marks, WIPO: WO 2016/181177 A3
The international patent publication on the internet:
https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2016181177&redirectedID=true

The author thanks Dr. Jenő Dúl (University of Miskolc, Hungary) and Dr. Pál Hatala (National Hungarian Mining and Metallurgical Association) who have contributed with their expertise and assistance in the development of the present process.

Literature

[1] G. Hajas: Surveying of the thin-walled gravity sand casting prototypes and the factors influencing their strength properties - New Hungarian casting patent

http://ombkenet.hu/images/2017/netre_2017_6_szam_kohaszat.pdf

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About the author

Hajas Gergely

General manager, Alu-Öntő Ltd.

Striko Westofen; Messe Stuttgart; Lost Foam Council; GF Casting Solutions; D.Quitter/konstruktionspraxis; Hajas; Pixabay; gemeinfrei; Meusburger; TUM; NuernbergMesse / Frank Boxler; Jaguar; Klaus Vollrath; ETHZ; Goldbbeck-Solar; Brembo