US1747197A - Process for the production of aluminum-silicon alloys free from carbide - Google Patents

Description

Patented Feb. 18, 1930 UNITED, STATES PATENT OFFICE rnoonss FOR THEPRODUCTION or anummumsriacon ALLOYS FREE Fnom'canmnr.

No Drawing. Application filed May a, 1926,'Seria1 No. 107,788, and in Germany May 12, 1925.

10 owing to this high iron content, these alloys cannot be employed in the production of pure aluminum silicon alloys capable of being cast.

If however correspondingly pure i. e., almost iron-free initial materials are employed,

15 it is possible to produce by electro-thermic treatment, an aluminum silicon alloy which is almost free of iron. Nevertheless it is impossible to obtain in this manner an alloy which has the composition of commercial.

aluminum alloys containing for example 8 or 13% silicon. At the high reduction temperatures of the oxides prevailing in the electric furnace carbon is taken up and such large amounts of carbides are formed that the .alloy cannot be industrially employed as a casting alloy. If however the silicon content is increased up to 35% and over, by suitably proportioning the ingredients of the furnace charge, the surprising observation .is made,

that the formation of carbide disappears practically completely. It should be remarked that even a comparatively small proportion of carbon, is detrimental for the manufacture as well as for the employment of the alloy for casting purposes. 7

The alloys rich in silicon must be alloyed with pure aluminum in accordance with the purpose for which they are to be used. Nevertheless if the preliminary alloy contains for example 2 to 3% carbon, subsequent alloying is practically impossible. If however the preliminary alloy contains a smaller proportion, for example 1' to 2%, of carbon, then part of the alloy will proceed to alloy, but so much residue remainsin the form of carbon containing dross, that the process becomes uneconomical.

The discovery that an alloy of aluminum containing more than 35% silicon hardly 5 takes up any carbon is the more surprising,

as it is well known that both pure aluminum as well as pure silicon, form corresponding carbides with carbon at 1400 C.

The preliminary alloy produced according -to the present process can be alloyed with pure aluminum, and thereupon worked up to the known aluminum silicon alloys, the usual known additions being also employed if desired. It is immaterial whether these sub stances such asfor example, small amounts of copper, are addedduring the formation of the subsequent alloy or are already present in the preliminary alloy produced by electrothermic means.

What I mean by the expression practically iron-free in the appended claims is an alloy whose iron content does not exceed 2%, preferably an alloy containing less than 1% of iron. 1

I claim:

1. In a process for the production of practically carbide-free aluminum-silicon alloys by electro-thermic means, the step which com prises the production of a practically ironfree preliminary alloy containing upwards of 35% of. silicon. I

2. In a process for the production of practically carbide-free aluminum-silicon alloys by electro-thermic means the step which comrises the production of a practically ironree preliminary alloy containing between 35% to 47% silicon.

3. A process for the production of practically carbide-free aluminum-silicon alloys by electro-thermic means, which comprises the production of a practically iron-free preliminary alloy containing upwards of 35% of silicon and alloying said preliminary alloy with pure aluminum.

' 4. A process for the production of practically carbide-free aluminum-silicon alloys by electro-thermic means, which comprises the production of a practically iron-free preliminary alloycontaining upwards of 35% of silicon, alloying said preliminary alloy in admixture with other known metals, to aluminum.

5. In a process for the production of practically carbide-free aluminum alloys by electrothermic means the-step which comprises electrically heating to alloying temperature in the presence of reducing agents practically iron-free aluminum compounds with practically iron-free silicon compounds in such proportions that the resulting practically iron-free aluminum alloys contain not less than 35% of silicon.

6. In a rocess for the production of practically car ide-free aluminum alloys by electro-thermic means the step which comprises heating to alloying temperature in an electric furnace and in the presence of reducing agents practically iron-free aluminum compounds with practically iron-free silicon compounds in such proportions that the resulting practically iron-free aluminum alloys contain not less than 35% of silicon.

In testimon whereof I aflix my signature.

CO AY VON GIRSEWALD