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Bionic Balls

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  3. How Long Will A Weld Last On A Koxx Sliver Sky?

    in Trials Chat

    Posted

    Again, no offence, but none of that would be viable on a bicycle frame.

    How could you heat different areas to seperate peak temperatures by wacking it in an oven (also know as precipitation hardening, the second stage of the heat treatment process of most alloys used in the manufacture of trials frames)? Im not having a go at you, but this kids about to spend how-ever much on a frame that he's being told, by you, he can fix easily, when in the real world, it's never going to be fully repairable.

    You may well do this for a job, but you sound like you've had no experience with frame repair or the practicle side of heat treatment, theory sounds great, but dosent always come through (Y).

    Cheers,

    Josh.

    Hello again..

    You've not quite followed what I meant there- you'd need to heat treat the frame as one (as you said you don't have enough control to do it locally), but the metal will have been affected differently at varying distances from the weld.

    I'm not saying it's easy to repair but it can be done and I believe it this was a very expensive frame! If heat treatment turns out to be too difficult then there are still other options to be considered.. Too many frames get shelved way too soon!

    Adam

  4. How Long Will A Weld Last On A Koxx Sliver Sky?

    in Trials Chat

    Posted · Edited by Bionic Balls

    No offence to you pal, but it sounds like you dont know too much about what the heat treating process does to aluminium.

    I do

    If your saying it's ok to put a previously heat treated aluminium section back through it's last stage then you've not quite thought it through, yes, the area around the weld may well return to its previous state, but what about the rest of the frame?

    You'd need a separate ageing treatment.. And no, it wouldn't be a local treatment- the whole frame would likely need heating.

    The only reason you can harden these series of aluminium is due to their composition and the way the alloyed elements react when heated to a solid solution, where the particals are rearanged, resulting in a greater resistance to shifting dislocations, so simply adding more heat will cause this structure to be broken down, ending in a softer material.

    Different areas will be heated at different rates and to different peak temperatures. Some areas could harden due to particulate coarsening. Normalising would only return the parent material to it's original properties if it was normalised to start with. No engineering aluminium alloy I can think of would be supplied like this.

    No offence to you- you sound like you know a fair bit, but I do actually do this for a job..

    Adam

  5. How Long Will A Weld Last On A Koxx Sliver Sky?

    in Trials Chat

    Posted

    Hi there- not posted on here for ages but people have some funny ideas about welding!

    theres no science when it comes to cracks, could crack straight away could last ages place your chips

    Yes there is. Lots. http://en.wikipedia.org/wiki/Fracture_mechanics http://en.wikipedia.org/wiki/Materials_science

    I'm pretty sure you can't heat treat a re-weld....but someone a little more into metallurgy may be able to shed some more light on the matter :)

    Yes you can. In an ideal world where there were no other complications we'd probably heat treat every weld if we could! Heat treatment gives restores the properties of the parent material before we welded it.

    Yes you can, but you'll have to find someone with an oven big enough!

    bingo.

    Nah, it f**ks with the original heat treating as far as I'd heard?

    yes it does. Welding makes it very hot..

    It should last forever if it's a good wield and you use the right material, but don't do it yourself get a professionial a to do it.

    some terrible spelling but near enough.. An aluminium frame will theoretically never last forever though (search for "fatigue limit" if you want to know why).

    Incorrect, the effect of the HAZ ( Heat Affected Zone) will soften the area and it will crack again, wether it be in a couple of days or a couple of months, it cant be repaired to its original state :).

    the heat affected zone will soften yes, but i'd be surprised if it's a non-heat treatable alloy. Chances are it's either 6 (Al-Mg-Si) or 7xxx (Al-Zn) series aluminium which can be heat treated quite easily if you have a big enough oven. If you want to know how, search for "precipitation hardening".

    Other big issues with welding aluminium are using the wrong filler (for 6xxx alloys use 4043A or 5356 and for 7xxx alloys use 5556A) and not cleaning the joint enough before welding (difficult on frames as you won't really be able to clean the inside of the tube easily- you should if you can though).

    Any more welding issues while I'm here?!

    Adam

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