US2290296A - Process for preparing lead alloys - Google Patents

Description

Patented My 21, 1942 s'mras rnocnss yon PREPARING Ln armors of New York No Drawing. Application February 10, 1949, Serial No.-3l8,368. in Germany February 29, 1939 10 Claims. (01. 75-157.

- kaline earth metals by reacting an alkaline earth metal carbide with molten lead, which requires less time than previously necessary.

It is a special object of the invention to provide a process for preparing lead alloys containing alkaline earth metals by reacting an alkaline earth metal carbide wherein a novel covering flux or slag is employed which increases the alloying speed.

In the specification and claims the term alkaline earth metals is employed to designate piagnesium, as well as calcium, barium and stronium.

It has already been proposed to prepare lead alloys containing alkaline earth metals by introducing an alkaline earth metal carbide into a molten bath of lead provided with a covering flux or slag composed of fused salts. Halides, such as, calcium fluoride, carnallite, calcium chloride, alkali metal chlorides and mixtures of alkaline earth metal halides and alkali metal halides, have been employed as the covering flux or slag. It was especially advantageous to employ mixtures of chlorides or fluorides of two or three alkaline earth metals so as to lower the melting point of the covering fluxor slag. I

It has now been found, in accordance with the present invention, that the addition of a relatively small quantity of metallic aluminum to the covering flux or slag causes an extraordinary increase in the speed of reaction when treating molten lead with alkaline earth metal carbides. The aluminum is preferably added in the form of granules and in quantities less than 1% by weight of the lead treated. The addition of the aluminum to the fused salt covering layer may take place either before or simultaneously with the addition of the alkaline earth metal carbides to the molten lead.

The following example serves to illustrate the invention, but the invention is in no way limited thereto:

Example A molten bath to 12 tons of lead is coving 88% of calcium chloride and 12% of calcium fluoride. To this layer to kg. of granular aluminum are'added. 1250 kg. of calcium carbide are added to the molten bath of lead and the mixture is stirred. After 3 to 4 hours thereaction is complete and a lead alloy is obtained containing 6% of calcium.

When carrying out the process under the same conditions but without the addition of aluminum, 8 to 9 hours are required to form a lead alloy containing only 4% to 5% of calcium. The addition of aluminum has been found advantageous with all types of iusedsalt mixtures suitable as covering fluxes for the lead bath during the reaction. For example, covering fluxes containing an alkaline earth metal halide, mixtures of alkaline earth metal halides and mixtures of alkaline earth metal halides with alkali metal halides may be employed in accordance with the present process. It is especially advantageous if the salt .mixtures were so selected that changes in the composition thereof occurring during the conversion of the alkaline earth metal carbide and the formation of the lead alloy would lower their melting points.

a mixture of 10% of CaCl2 and 90% BaCla may be employed with special advantage for the salt mixture of the covering flux, as during the treatment of the molten lead bath covered thereby with calcium carbide and the melting point of such salt mixture is lowered. This depression of the melting point is caused as a portion of the calcium obtained by the decomposition of calthe proportion of calcium chloride in the covering flux approaches that necessary for a eutectic mixture of 09.012 and BaCla. The free barium produced by this reaction is taken up by the lead.

When covering fluxes are employed containing one or more hygroscopic salts, the addition of aluminum thereto has still a ,further advantage in that it efiects dehydration of such covering fluxes. It is very important that the covering fluxes employed for the process are substantially dehydrated upon the addition of the alkaline earth metal carbide as any water which may be present decomposes the carbide to form an alkaline earth oxide and acetylene. The forma tion of the alkaline earth oxide is highly undesirable as such oxide no longer contains the alkaline earth metal in a form available for the formation of an alloy with the lead. Furtherered with 1700 kg. of. a fused salt layer containmore, the calcium oxide decreases the fluidity of the covering flux which renders it more difficult to separate the lead alloy from the covering flux after completion of the process and which renders the losses of the alloy higher as small globules thereof remain suspended in such 5' flux.

The addition of aluminum to covering fluxes containing alkaline earth metal salts which are very difiicult to dehydrate completely by the application of heat alone, such as calcium chloride, effects complete dehydration of such cov-' ering fluxes and therefore prevents the decomposition of the alkaline earth metal carbides to form oxides which would be caused by the presence of the water. The aluminum may be added to the covering fluxes before the introduction of the alkaline earth metal carbides into the molten lead bath or simultaneously therewith.

, While we have described herein some embodi- 'ments of our invention by way of example, we go wish it to be understood that we do not intend to limit ourselves thereby, except within the scope of the appended claims.

We claim:

1. In a .process for the preparation of leadalkaline earth metal alloys which comprises introducing an alkaline earth metal carbide into a molten bath of lead provided with a suitable fused salt covering flux, the improvement which comprises adding metallic aluminum to the covering flux.

2. In a process for thepreparation of leadalkaline earth metal alloys which comprises introducing an alkaline earth metal carbide into a molten bath of lead provided with a suitable fused salt covering flux, the improvement which comprises adding metallic aluminum to the covering flux before the alkaline earth metal carbide is introduced into the molten lead bath.

3. In a process for the preparation of lead- 40 alkaline earth metal alloys which comprises introducing an alkaline earth metal carbide into a molten bath of lead provided with a suitable fused salt covering flux, the improvement which com-prises adding metallic aluminum to the covering flux while simultaneously introducing the alkaline earth metal carbide into the molten lead bath.

4. In a process for the preparation of leadalkaline earth metal alloys which com-prises introducing an alkaline earth metal carbide into a molten, bath of lead provided with a suitable [fused salt covering flux, the improvement which comprises adding granular metallic aluminum to the covering flux.

5. A process for the preparation of lead-alkaline earth metal alloys comprising adding an alkaline earth metal carbide to a bath of molten lead provided with a fused salt covering flux containing a mixture of alkaline earth metal halides and metallic aluminum. I

6. A process for the preparation of lead-alkaline earth metal alloys comprising adding an alkaline earth'metal carbide to a bath of molten lead provided with a fused salt covering flux containing a mixture of alkaline earth metal halides and alkali metal halides and metallic aluminum.

7. A .process for the preparation of lead-alkaline earth metal alloys comprising adding an alkaline earth metal carbide to a bath-of molten lead provided with a covering flux containing a salt mixture of such composition that the change in its composition during the preparation of the lead alloy lowers its melting point, and metallic aluminum.

8. In a process for the preparation of leadalkaline earth metal alloys which comprises introducing an alkaline earth metal carbide into a molten bath of lead provided with a suitable fused'salt covering flux containing hygroscopic salts, the improvement which comprises adding metallic aluminum to the covering flux to dehydrate the covering flux. I

9. In a process for the preparation of leadalkaline earth metal alloys which comprises in-,'

troducing an alkaline earth metal carbide into a molten bath of lead provided with a suitable fused salt covering flux, the improvement which v comprises adding metallic aluminum to the covering flux in a quantity less than 1% by weight of the lead to be alloyed.

10. A process for the preparation of lead-alkaline earth metal alloys comprising introducing an alkaline earth metal carbide into a bath of 1000 to ,1200 parts by weight of molten lead provided with a covering flux containing parts by weight of a salt mixture containing 88% of calcium .chloride and 12% of calcium fluoride and 2.5 to 3 parts by weight of metallic aluminum.

JOHANN SIEGENS. OSKAR; RODER.