6069 aluminum and welding

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does uncontrolled heating/melting of this aluminum weaken its
"structure"? does aluminum have a structure? can welding weaken a tube
if it's deformed a bit? why do i ask? i have a new mountian bike frame
and there's a bulge near one of the welds. the tube is not thin there,
as there is no defect on the inside of the tube. just a 1 cm by 3-4 mm
slight bulge on the outside of the tube. the manufacturer will exchange
it but i don't want to bother if it's just cosmetic. any opinions? i
have pictures if necesary. thanks



--

Absolutely. Pic's will help but I think you must accept the
replacement offer!! It gets serious especially on certain areas of the
frame where the stresses are at the max such as the joint between
downtube and headtube where many manufacturers add gussets at the
bottom. In addition, the joints on the tubes frames go through not
only tensile or compressive stresses, but also TORSIONS! The bulge
reduces the tube strength to withstand torsions. Remember how fatique
aluminum mat'ls are.

the blur <usenet-forum@cyclingforums.com> wrote in message news:<TvJfc.82897$pK2.81034@fe08.usenetserver.com>...
> does uncontrolled heating/melting of this aluminum weaken its
> "structure"? does aluminum have a structure? can welding weaken a tube
> if it's deformed a bit? why do i ask? i have a new mountian bike frame
> and there's a bulge near one of the welds. the tube is not thin there,
> as there is no defect on the inside of the tube. just a 1 cm by 3-4 mm
> slight bulge on the outside of the tube. the manufacturer will exchange
> it but i don't want to bother if it's just cosmetic. any opinions? i
> have pictures if necesary. thanks
>
>
>
> --

it's not really close to the actual weld-it's on the side of the top
tube about an inch from the head tube. it's below a gussett weld on top
of the top tube. i think its minor-probably cosmetic only. you can feel
it and see it if the lighting is right. there's no defect on the inside
of the tube(-i can feel through the head tube)



--

the blur wrote:
> does uncontrolled heating/melting of this aluminum weaken its
> "structure"?

yes

> does aluminum have a structure?

yes

> can welding weaken a tube
> if it's deformed a bit?

yes

> why do i ask? i have a new mountian bike frame
> and there's a bulge near one of the welds. the tube is not thin there,
> as there is no defect on the inside of the tube. just a 1 cm by 3-4 mm
> slight bulge on the outside of the tube. the manufacturer will exchange
> it but i don't want to bother if it's just cosmetic. any opinions? i
> have pictures if necesary. thanks

its not cosmetic, it's structural. take advantage of the manufacturers
generous offer & have it replaced. to perform a safe repair requires
substantial work, time & expensive equipment making it most unlikely to
be an economic exercise.

In article <2Oahc.24546$yr4.18934@newssvr27.news.prodigy.com>, jim beam <uce@ftc.gov> wrote:
>the blur wrote:
>> does uncontrolled heating/melting of this aluminum weaken its
>> "structure"?
>
>yes
>
>> does aluminum have a structure?
>
>yes
>
>> can welding weaken a tube
>> if it's deformed a bit?
>
>yes
>
>> why do i ask? i have a new mountian bike frame
>> and there's a bulge near one of the welds. the tube is not thin there,
>> as there is no defect on the inside of the tube. just a 1 cm by 3-4 mm
>> slight bulge on the outside of the tube. the manufacturer will exchange
>> it but i don't want to bother if it's just cosmetic. any opinions? i
>> have pictures if necesary. thanks
>
>its not cosmetic, it's structural. take advantage of the manufacturers
>generous offer & have it replaced. to perform a safe repair requires
>substantial work, time & expensive equipment making it most unlikely to
>be an economic exercise.

Just wanted to add my comments.
2 years ago I discovered a crach in my Cannondale bike in the right
chain-stay. The crach was about 3/4 around the tube about 4-5 cm from the
dropout, and was caused by an accident 5 years before that.

I got the frame welded by a friend, who works with metals at the university in
town. I know that the fram will never be as strong as before, but it is a lot
stronger compared it's state when I discovered the crack. After all, I have
been riding the frame with that crack... and not noticed it.

I now use the bike as a spare one when training in bad weather. The new bike
is only used during competition and training in good weather.

--
Jørn Dahl-Stamnes
http://spiderman.novit.no/dahls/