US2139246A - Castings of aluminium alloys - Google Patents

Description

Patented 6, 1938 UNITED STATES PATENT OFFICE CASTINGS F ALLOYS PaIul Spitaler, Bitterteld, Germany, assignmto Farbenindustrie Aktiengesellschait,

Frankiort-on-the-Main, Germany No Drawing. Application April 24, 1935, Serial No. 17,971. In Germany May 3 Claims.

rectly with the magnesium content of the alloy,

the higher themagnesium content, the larger being the amount of silicon needed to produce the desired eflect. On the other hand, however, higher percentages of silicon result in a considerable lowering of the strength and elongation of the alloys, so that, in order to obtain castings which will meet the usual commercial requirements in this respect, the addition of silicon .to alloys high in magnesium must remain below the optimum amounts for the attainment of compact texture. Bearing these conditions in mind, alloys that have been found suitable are those containing between about 4 and about 7% of magnesium and between about 0.8 and 1.5% of silicon (the latter increasing within the specified limits, with the magnesium content of the alloy). A very suitable alloy is one containing of magnesium and 1 to 1.2% of silicon. Manganese, in amounts up to 2.5% (preferably about 1%) may also be incorporated with the alloy.

It has also been observed that the siliceous alloys described above are notably superior, in respect also of their strength at high temperatures, to the corresponding alloys containing either no silicon at all, or such amountsof silicon, i. e. not more than about 0.3%, as are normally M present as impurity, inasmuch as, at higher temperatures, the tensile strength of the alloys diminishes to a less extent than that of the corresponding alloys free from silicon. For example, when an alloy containing 5% of magnesium, 1.1%

I of silicon and 0.1% of manganese, is heated to about 300 0., its tensile strength is only about 25% lower than at room temperature, whereas, inthecase oithesame alloy, containing only 0.2%

of silicon, the strength at 300 C. is already more than 35% lower.

This observation-probably ail'ords at least a partial explanation of the more compact texture of the castings made from the siliceous alloys, since, owing to the greater strength of these alloys at the higher temperatures through which they pass after solidification, the loosening of their structure is correspondingly slighter.

Castings made of the following aluminium alloys show the described qualities:

1. 5.0% Mg (2.) 7.0% Mg (3. 5.0 Mg

- 2.0 Si 0.3 Mn

1%: Si 1.5%, Si

4. 5.0 M s. '4. M a. a. M

Even castings with comparatively thin walls (for example about 5 mm.) made from alloys in accordance with the invention, are practically quite impervious under a positive pressure of at least 8 atmospheres.

- As the result of their greater compactness of texture, in conjunction with their known property of resisting corrosion, the alloys of the present invention are suitable for the production of a great variety of mould castings, such as fittings for pipes conveying liquids, carburetter parts, hydraulic control members, compressor casings, vessels for containing liquids and gases, and the like.

I claim: l 1. Castings of an aluminium alloy. containing of magnesium. 1.1% of silicon and 0.1% of manganese, balance aluminium having a compact texture and a high mechanical strength.

2. Castings of aluminium alloys consisting of 5 to 7% of magnesium, 0.8 to 1.5% of silicon, manganese in a quantity up to 2.5% the balance being aluminium, such castings having a compact tex- 'ture and a high mechanical strength at elevated temperatures.

3. .Castings of aluminum alloys consisting ofabout 5% of magnesium, between about 1.0 and about 1.2% of silicon, up to 1% of manganese, the balance being aluminium, such castings having a compact texture and a high mechanical strength at elevated temperatures.

, PAUL BPITALER.