Stress releaving aluminium

[quattro]

Good afternoon chaps

Im in the process of making an aluminum intake manifold, it has warped ever so slightly I now feel that the manifold needs the stress releaving from it, I came across some info saying that 350F for 2hrs should do it.

The question I have is that this will weaken the material, I'm sure of this.

Is it better to have the manifold under slight tension rather than loose the strength of the material or will the tension in the Alu make it weaker?

It will hold ITRO of around 2-2.2 bar.

 

[pedrobedro]

If it's the face of the manifold can't you just level it? A sheet of 60 grit on a piece of glass and rub it back and forward for a while should do it.

 

[TechnicAl]

It has to be a suck it and see answer but Id expect that the stress relief would lengthen the life. Im thinking that the most likely failure mode will be fatigue caused by the vibration of the engine. The as welded condition will be more susceptible to this than the SR condition.
I cant imagine that it would fail due to the lower strength.

 

[quattro]

Its not totally finished yet. I have constructed the plenum of the manifold and am waiting for the flange to be machined, the reason I know its under tension is that i cut 15mm off the end before shaping and capping off. After looking at the off cut it had splayed out around 8-9mm (its a 1/2 circle 100mm plenum with tapered side walls from 60mm to 35mm) and the plenum is slightly warped as stated before.

I came across cryogenic stress relief too, any info on this?

Don't really want to just give it a go as I hardly get time to fabricate parts like this due to work commitments.

 

[hotrodder]

Stress relief temp for ally is usually quoted as 650F which is in the annealing range... http://www.lincolnelectric.pl/en/18620.xml#faq18620
350F is in the range used for artifical aging (soak times would be longer though) and pretty close to some of the stabilizing treatments and soak times

As Al said i wouldn't worry about softening/weaking it, it'll be partially annealed from welding it together anyway. If it's moved 8-9mm i can't see a low temp bake correcting it. What's it made from (alloy and thickness), probably picturing it wrong but i'm thinking it's a job for hammers n dollies if the end has splayed out

 

[quattro]

Most is 3.2mm 6063 exept top and bottom flat parts, which are 6mm.
I have welded both sides of the seams, outer side first with full penetration and then on the inside just to fill the corners and any over penetration I had in 1 or 2 places to aid in smooth air flow.

Guess ill have just to test it to +3 bar then and see what happens.

 

[hotrodder]

With the shape and volume of a typical plenum it'll be fine, as Al said fatigue is what tends to kill these sorts of things rather than a lack of outright strength. Picture something like a header tank... typically made from 1.5mm 1050-H14, pressure is obviously lower but volume often larger. A well designed one won't change shape when hydro testing at 2 bar, a badly designed one (think no shape, outside corner welds) may 'balloon' a tiny bit and take a set after it's seen hot coolant for a while but 9 times out of 10 if/when it fails it'll be the badly thought out mounts succumbing to fatigue followed by a split seam