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PostPosted: Wed Jun 13, 2012 5:08 pm 
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Joined: Tue Dec 05, 2006 9:59 pm
Posts: 151
Location: UK
Hi everyone,

I've sent an e-mail to Pinarello but thought I'd ask here too. Does anyone know what inert gas was used whilst welding the Pinarello Dogmas from 2003? The magnesium/carbon ones. We've tried using Argon but the weld isn't great, our next option is Helium.

thanks

Xavier


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PostPosted: Wed Jun 13, 2012 7:08 pm 
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Joined: Sat Feb 25, 2012 4:23 am
Posts: 51
I've welded magnesium before and used Argon with no issues.

Are you using a TIG. Are you cleaning it properly? What welding experience do you have?


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PostPosted: Wed Jun 13, 2012 8:08 pm 
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Joined: Tue Dec 05, 2006 9:59 pm
Posts: 151
Location: UK
It's not me, it's one of the engineers in our chemical engineering department (university)
Our next step is to use a pure magnesium rod I think

Xavier


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PostPosted: Wed Jun 13, 2012 8:26 pm 
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Joined: Sat Feb 25, 2012 4:23 am
Posts: 51
If you're using rods then I think you're trying to stick weld. I don't stick weld but I think usually they embed gas within the rods.

I've only TIG welded magnesium. I don't see why you would attempt to weld anything like a bike frame with any other method.

MIG would be too messy and uncontrolled. Stick would be even messier.


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PostPosted: Wed Jun 13, 2012 11:59 pm 
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Joined: Thu Jan 03, 2008 6:14 am
Posts: 1299
Location: by Crystal Springs (Sawyer Creek Trail)
TIG weld is a must. Are you trying to fix the frame?


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PostPosted: Thu Jun 14, 2012 4:00 am 
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Joined: Wed Feb 02, 2011 3:48 am
Posts: 1413
rod = filler


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PostPosted: Thu Jun 14, 2012 7:18 am 
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Joined: Tue Dec 05, 2006 9:59 pm
Posts: 151
Location: UK
Thanks everyone. It is a TIG weld yes, just for some reason was cracking around the edge of the weld. The frame was cracked on the chainstay near the BB. It only cost me £85 for the frameset so we're trying anything!

Xav


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PostPosted: Thu Jun 14, 2012 7:54 am 
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Joined: Sat Feb 25, 2012 4:23 am
Posts: 51
I would make sure to clean the area thoroughly. Make sure any paint is gone.

Try fixing it with the torch only at first. Don't introduce filler metals yet. If you don't know the makeup or have the correct filler metal then you may just be compromising the weld.

I don't remember magnesium as being a hard metal to weld. I found it easy like stainless and def not as complicated as aluminum.

If you are cracking metal it may be too much heat. What you can do is equalize the temperature of the surrounding area with the torch before trying to fix your crack. In a sense you are warming the area prior to welding.

Also make sure you are blowing gas after you have stopped welding.


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PostPosted: Thu Jun 14, 2012 1:40 pm 
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Joined: Tue Dec 05, 2006 9:59 pm
Posts: 151
Location: UK
Thanks very much Podunk 8) fingers crossed it'll work!

Xav


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PostPosted: Fri Jun 15, 2012 2:04 am 
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Joined: Mon Mar 26, 2012 2:45 pm
Posts: 113
Location: Bali, Indonesia
It may also be necessary to use a diffuser/shield to provide argon flushing to the area being repaired. As mentioned by podunk, try to fuse without fill rod first and be sure that your tungsten is cleaned and sharpened. if you are welding up to the BB, be sure that the paint is removed inside first. I remember a (real :oops: ) welder telling me that with magnesium it is very important that the metal be cleaned and welded immediately so as to avoid impurities in the weld.

Monkeyburger

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...finding my inner Onoda-kun...


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PostPosted: Fri Jun 15, 2012 3:00 am 
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Joined: Wed Mar 28, 2012 3:16 pm
Posts: 205
Location: Utah, USA
I have never welded magnesium before but have found that back purging the weld is critical for best results with ti and stainless. Keep an extinguisher handy, MG is very reactive.

*edit*

Check THIS out. Looks like you need to use AC and 50/50 argon/helium mix.

_________________
Trek 5500 - 13.75lbs on a $1400 Budget
20 gram 1x10 chain guide


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