DE2746122A1 - CORE MATERIAL FOR CASTING CORES - Google Patents

Description

UOFFMANN · EITU ?. «& PARTNER

PATENTANWÄLTE DR.ING.E.HOFFMANN DIPL.-ING. W. E ITLE DR. RER. N AT. K. HOFFMAN N DIPL.-ING. W. LE H N

D-βΟΟΟ MÖNCHEN 81 - ARABEILASTRASS E 4 (STERNHAUS) TE LE FON (089) 911087 TELEX 05-29619 (PATHE)

Alcan Aluminumwerk Nürnberg GmbH in Frankfurt / Main

Core material for foundry cores

The invention relates to a core material for foundry cores Production of cast parts with largely closed cavities such as cooling channels in pistons for internal combustion engines, which core material contains water soluble salt. This water-soluble salt is used after the casting of the casting to be able to easily remove the core, which is largely surrounded by this, from the casting. When dissolving the salt content will be After casting, the compressive stresses present in the core are reduced and at the same time cavities are created in this, which cause shaking of the rest of the core material.

When producing cast parts with largely closed cavities Difficulties often arise from the fact that the cores used to form these cavities, which only have very few and very thin core supports can be held because of their relatively small size compared to the casting material for the casting specific gravity experience an undesirable buoyancy, which can lead to a change in the position of the core. aside from that

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the cores can suffer deformation because of the thermal expansion of the known core materials does not match the thermal expansion of the core support holder that occurs during casting. In addition to core breaks, this can also lead to an incorrect position of the cavities in the cast part produced.

The invention is therefore based on the object of creating a core material for the above-mentioned application, which
above-mentioned disadvantages of the previously known core materials
does not have, so has a specific weight that largely corresponds to that of the cast material, one of that of the core support holder largely the same thermal expansion and one
has good thermal conductivity with high heat storage capacity at the same time. Furthermore, the development of gas which occurs in known core materials when casting material around them should largely be generated
can be avoided, since such gases from castings with largely closed cavities can only be removed with difficulty.
The core material should be such that the core can easily be removed from the cast part that largely surrounds it.

According to the invention, this object is achieved in that the core material of the type mentioned at the beginning contains, in addition to the water-soluble salt, granules of a metal and synthetic resin.
The metal granulate gives the core material a specific weight which largely corresponds to that of the casting material, as well as a thermal expansion which is similar to that of the core support holder. This also results in good thermal conductivity and, at the same time, high heat storage capacity. The also provided proportion of synthetic resin in the core material
serves to ensure a good connection between the metal granulate and the
Ensure water-soluble salt by baking when heated.

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In a preferred embodiment of the core material according to the invention the metal granulate consists of a metal that has a lower linear thermal expansion coefficient is than that of the casting material, and in which the specific gravity of the metal granules is higher than that of the casting material is. As a result, a core material is obtained, which with its coefficient of thermal expansion and its specific weight that of the casting material is particularly close.

Appropriately, the metal granulate consists of individual spherical grains, which with the help of the synthetic resin with the water-soluble Salt are bound or can be bound. This causes the metal granulate to be shaken out of the cast part Particularly easily possible via the core support holes. The proportion of metal granules in the total core material should be between and 65%, but better between 25 and 50%. A proportion between 25 and 40% is particularly useful.

In the drawing is one made from the core material according to the invention produced annular cast core 1 with core holder 2, which are fastened in the core by tubular rivets 3.

Fig. 1 shows an oblique view, and Fig. 2 shows a cross section of this core.

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Claims (5)

HOFFMANN · RlT IΛΖ & VAIiTNKR PATENTANWÄLTE OR. ING. E. HOFFMAN N · DIPl.-ING. W. E ITlE DR. RE R. N AT. K. HOFFMAN N DIPL.-ING. W. LE H N D-8000 MÖNCHEN 81 · AR AB E IIASTRAS S E 4 (STERNHAUS) · TE LE FON (089) »11087 · TE LE X 05-29619 (PATHE) Alcan Aluminumwerk Nürnberg GmbH in Frankfurt / Main Core material for foundry cores Patent claims 1. Core material for foundry cores for the manufacture of cast parts with largely closed cavities such as cooling channels in pistons for internal combustion engines, which core material contains a proportion of water-soluble salt, characterized in that it also consists of a Granules of a metal and made of synthetic resin. 2. Core material according to claim 1, characterized in that the metal granules consist of a metal with a linear The coefficient of thermal expansion is lower than that of the casting material. 3. Core material according to claim 1, characterized in that the specific weight of the metal granules is higher than that of the casting material. 4. Kernamterial according to claim 1, characterized in that the metal granulate consists of individual spherical metal grains consists. 5. Core material according to one or more of claims 1 to 4, characterized in that the proportion of metal granules between 20 and 65%, in particular between 2 5 and 50% and particularly expediently between 25 and 40%. 0-'I B / 0338 ORIGINAL INSPECTED