Aluminium braizing

[SL666]

I think i know the rods you are talking about.. they sell them in bundles of 10 etc at 4wd shows, with a bit of a demo on a coke can, can't remember their actual name, but you are paying 10x retail for them in that situation..

ben: brazing in general isn't particularly strong on anything except joins with a lot of surface area, like copper pipes where they slip into each other..

[Ben Wilson]

I've seen 1.6 steel brazed at 90 degrees tear before the braze failed, brazing is highly underrated in my opinion.

[TA22 GT]

I've seen 1.6 steel brazed at 90 degrees tear before the braze failed, brazing is highly underrated in my opinion.

brazing steel is a completley different story to brazing aluminium.....

Cheers,
Simon

[Ben Wilson]

Why? - I can't remember my metallurgy too well, but if you heat the base metal until the granular structure expands, then add a filler material with a lower melting point which capillaries between the grains of the base material. Once it cools the granular structure locks over the filler material creating a strong bond.

Theoretically it should work most metals - chrome molly doesn't like it as its granular structure expands too much and it cracks.

[SL666]

ive brazed copper to steel to stainless to ally.. at tech for a laugh.. but i just don't think it would be as stronger bond..

and as for those who suggested oxy welding ally.. you have fun with that..

[Ben Wilson]

I've done it (oxy welding alloy), with practice it does work, but it's never as pretty as a tig weld - and it's bloody hard.

[SL666]

i know i have enough trouble trying to keep out contaminants when im tigging.. let alone with an oxy

[ReQuieM]

Hasn't been too bad really. Because I'm learning as a go Its taken a bit to get the nak of but I think I'm close to having down pat.

As far as not as nice a bead, I've done a few runs that look better then tig. So I think it comes down to practice. Plus in the scheme of things its hella cheaper and it works wiht a little patients.

Just my 2c

[merc-blue]

better than tig? mate you need more tig practice,

[Ben Wilson]

They are stronger than tig a lot of the time. More even heat = less stress concentration.

[SL666]

They are stronger than tig a lot of the time. More even heat = less stress concentration.

okay, here we go i believe TIG is stronger for that exact reason.. smaller HAZ.

[Ben Wilson]

Smaller HAZ = more concentrated area of stress,,,

[SL666]

larger HAZ = larger area of weakness

[Ben Wilson]

- Exactly

A small weak area will serve to concentrate stresses and fail a lot faster than a larger area.

A simple engineering test for a Friday afternoon:
Cut two bits of paper like shown in the attached photo (make sure the thin bit is the same depth on both)
Pull on the ends and tell me which is stonger...

[SL666]

im not sure that takes into account the smaller HAZ would be re-enforced by the fillet of the weld..