Solders for Aluminium.
—Hundreds of aluminium solders have been invented, naturally all claimed to be strong and durable, the alloys containing various metals, such as aluminium, antimony, bismuth, cadmium, chromium, copper, lead, manganese, silver, phosphor tin, tin, and zinc. A [table] of the most approved aluminium solders is here given.
Many of the best solders for aluminium contain a small proportion of phosphor tin. A molten alloy containing phosphorus placed on aluminium tends to absorb oxygen from the impure film as well as the surrounding air.
Compositions of Aluminium Solders
| Tin | Zinc | Silver | Alu- mi- nium | Cop- per | Bis- muth | Phos- phor Tin | Cad- mium | Lead | Anti- mony | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 72 | ·5 | 25 | -- | 1 | ·5 | -- | -- | 1 | -- | -- | -- | ||||||||
| 80 | 20 | -- | -- | -- | -- | -- | -- | -- | -- | ||||||||||
| 97 | -- | -- | -- | -- | 3 | -- | -- | -- | -- | ||||||||||
| 20 | -- | 10 | 70 | -- | -- | -- | -- | -- | -- | ||||||||||
| 90 | -- | -- | 10 | -- | -- | -- | -- | -- | -- | ||||||||||
| 65 | 27 | 5 | ·75 | 2 | ·25 | -- | -- | -- | -- | -- | -- | ||||||||
| 30 | 20 | -- | -- | -- | -- | -- | 50 | -- | -- | ||||||||||
| 99 | -- | -- | -- | 1 | -- | -- | -- | -- | -- | ||||||||||
| 90 | -- | -- | -- | 9 | 1 | -- | -- | -- | -- | ||||||||||
| 6 | 77 | ·5 | -- | 3 | ·25 | -- | -- | -- | -- | 3 | ·25 | -- | |||||||
| -- | 90 | -- | 6 | 4 | -- | -- | -- | -- | -- | ||||||||||
| -- | 80 | -- | 12 | 8 | -- | -- | -- | -- | -- | ||||||||||
| -- | 80 | -- | 20 | -- | -- | -- | -- | -- | -- | ||||||||||
| -- | 90 | -- | 5 | -- | -- | -- | -- | -- | 5 | ||||||||||
| 80 | 17 | -- | 2 | ·25 | -- | -- | ·75 | -- | -- | -- | |||||||||
| 75 | 22 | -- | 2 | ·5 | -- | -- | ·5 | -- | -- | -- | |||||||||
| 70 | 25 | -- | 3 | -- | -- | 2 | -- | -- | -- | ||||||||||
In making the solders here given, it is advisable to avoid loss of the more easily volatile of the metals by adopting the following precautions: The aluminium is melted first, the zinc is added in small pieces, then tin in small pieces, and lastly the phosphor tin.
Inasmuch as zinc alloys with aluminium more readily than does any of the common metals, solders that will readily “tin” aluminium generally contain zinc in varying proportions. The solders found most satisfactory contain zinc, tin, aluminium, and a very small proportion of phosphor tin; but they do not run very freely or fuse so readily as the ordinary tin and lead solders, and it is necessary to use a higher temperature, so high, in fact, that difficulty is found in using these solders with a soldering bit, and it is generally necessary to use a blowlamp.
While there is no solder that allows aluminium to be soldered with the facility and success experienced with other metals, that of Richard’s is extensively used, and seems to have given as good results as any. It consists of the following ingredients: Tin 29 parts zinc 11 parts, aluminium 1 part, and 5 per cent. phosphor tin 1 part—practically the same as that given in the last line of the table. This solder has withstood the test of time better than many of the patented solders, and can be used in jointing aluminium to aluminium, also aluminium to copper or brass, and without the use of a flux. In making the solder it is advisable to avoid loss of the more easily volatile of the metals. The aluminium should be melted first, then the zinc, tin, and phosphor tin in the order named.
When using phosphorus instead of phosphor tin in the making of aluminium solder, it will first be necessary to incorporate it with the tin, for which purpose take a length of 1-in. gas barrel, attach a screwed cap at one end, and close the opposite end with a tin (not tin-plate) plug. Remove the screwed cap, and, having carefully dried between blotting paper the proper proportion of phosphorus, insert the latter in the tube and replace the cap. Now put the plugged end of the tube into the molten tin; this will melt the plug of tin and so allow the phosphorus to come in contact with the molten metal. The ingot of phosphor tin formed is afterwards alloyed with the other ingredients, as already explained.