US2065170A - Magnesium alloy - Google Patents

Description

Patented Dec. 22, 1936 ATENT OFFICE No Drawing. Application May 15,. 1936, Serial No. 80,015. In Switzerland May 15, 1935 ICIaim.

This invention relates to a magnesium alloy which is to be used more particularly in the construction of internal combustion engines.

The magnesium alloys hitherto known are not suficiently resistant to corrosion and are not sufficiently hard, especially at the operating temperatures of the engine amounting to 200-300", and this results in excessive wear and inutility, for example of pistons.

Such drawbacks and other disadvantages are avoided according to the present invention, according to which one starts out from a magnesium-aluminium alloy with small silicon content with hardness raising addition of antimony, nickel, chromium and molybdenum, and the brittleness brought about by the addition is removed by choosing the aluminium content comparatively high and admixing copper and titanium with the alloy.

The magnesium alloy according to the present invention has the composition given below:-

Per cent Aluminium 14 18 Silir-nn 0.1 1

Antimony 3 8 Nickel 2 5 Chromium 0.05- 0.5 Manganese 0.1 l Molybdenum 0.05- 0.5 Copper- 6 8 Titanium 0.1 2

the rest being magnesium.

If desired up to 5 per cent. of steel material may be added in addition to such an alloy.

According as to whether the magnesium content is lower or higher within the said limits the alloy can be used either for pistons for internal combustion engines or for engine blocks, aircraft construction and so forth, particularly in consequence of its resistivity to corrosion and its specific gravity of about 1.8.

Whereas the alloys hitherto proposed in the best cases attained at ordinary temperature Brinell hardness of about 50, which sank to about 5 at 200-3002 experiments have shown that an alloy according to the invention shows at ordinary temperature a Brinell hardness exceeding 100, e. g. 120-130, and at 300 C. the still satisfactory hardness of 30.

' scored or corroded, and that the engine almost immediately started up again. Pistons subsequently removed were of mirror-like smoothness and the cylinder walls also were not scored or corroded in the'slightest. The benzine consumption fell very largely and the oil consumption was equal to zero.

Example In a steel crucible a flux is melted which serves at the same time both as a cleansing and a covering agent and which consists of a mixture of one part of potassium chloride and one part of magnesium chloride; the whole is thoroughly mixedand is cast into slabs.

In the heated crucible fiuxing agent to the extent of 3 to 8 per cent. of the charge is fused and thereupon magnesium is added. until the crucible is filled up to 5 cm. below the edge. According as the magnesium melts down the rest of the same is added.

Previously preliminary alloys are made in a suitable manner from the remaining alloy constituents, which alloys are then melted together to the so-called main preliminary alloy. This latter, preheated to -100", is added to the magnesium melt, in which it slowly dissolves. The fluxing agent rises to the surface during the fusion operation and covers the melt.

When everything is, liquid the whole is thoroughly stirred and heated to 800-850. The crucible is then removed from the furnace and allowed to cool for some minutes down to casting temperature (700-750"). Before casting the salts and impurities are preferably taken off with the casting ladle. Casting is eifected directly from the crucible with great care with the ladle as well. Preferably the stream being poured or cast is dusted with sulphur powder in order to prevent oxidation.

In order to make sand castings a special sand for magnesium is used which is moistened with a 20 per cent. aqueous ammonium fluoride solution.

The casting mould is preferably provided with a filter of core sand. The cores are made from red core sand, if desired mixed with 2 to 3' per cent. sulphur powder, and with the lowest possible linseed oil content. Before drying the cores have a 20 per cent. ammonium fluoride solution blown on them. Whenever possible all pieces are to be cast with rising.

The material can also be used in chill moulds and in the die-cast process.

I claim;

A magnesium alloy of the following composition:

v the rest magnesium.

FRITZ CHRISTEN.