soldering aluminum and iron

Try uk.d-i-y it's far more appropriate and you *will* get many useful answers there (although not for another 6 or 7 hours or so!)

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You would probably get good results with a strong epoxy to cement the blade in and at the same time be able to fill the channel and finish it off better. I have cemented power hacksaw blades into aluminium tube to make knives, perhaps you might consider that method as neater than the channel?

Yes, but not in one operation. You can get 'aluminum solder' (actually a zinc alloy of some sort) that (after you abrade the aluminum) can be made to stick on aluminum with no flux. And tin/lead solder, with acid flux (I like the NoKoRode stainless formula), will work on steel.

After removing the acid flux, you can join the two solders together.

I've used fluxes that made the aluminum solder stick without the race from wire-brushing to heating (melt the solder within seconds of the 'cleaning' phase, or it doesn't stick), but they were covered with warning labels, kinda scary.

I've never tried (soft) soldering iron, but Aluminum and stainless steel just need the right flux. (Alco aluminum flux and Stay brite for SS.) Soft solder is kinda weak though... may not be good for a blade.

George H.

On May 8, 2019, whit3rd wrote (in article):

The classic dodge is to use a fiberglass or stainless steel brush to abrade the hot aluminum surface under a pool of molten solder. The solder excludes the atmosphere, allowing fluxes of ordinary aggression to work.

Joe Gwinn

Eutectic rod and MAP gas are your best bet, but that is too hot for silicon.

Many thanks for the answers and suggestions - lots to think about. If you don't hear from me again you know I tried one of the toxic chemicals without success!

Back in WW2 the RAF repaired airplanes by soldering aluminum with plumbing solder, under oil. No idea what they used for flux.

Cheers

Phil Hobbs

An airplane with structural soft solder :/

NT

Not a problem. Some surface defects and cracks on supersonic aircraft (F1-11, max speed mach 2.5 for example) are patched with a type of 'sticky tape' called 'instant air-frame'.