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Welding Aluminium Frame

Old 01-13-21, 04:22 AM
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Smeths
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Welding Aluminium Frame

Hello,

I have a Carrera bike with two small cracks in the headset.

I like to get them welded. I live in Birmingham UK. Anyone know a good bike welder?

Regards

John S
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Old 01-13-21, 04:48 AM
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dsaul
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It is most likely 6061 aluminum and can't be safely welded without post weld heat treatment. There is no cost effective method of doing that, so it is usually time to get a new frame, if they crack.
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Old 01-13-21, 04:56 AM
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Smeths
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Originally Posted by dsaul View Post
It is most likely 6061 aluminum and can't be safely welded without post weld heat treatment. There is no cost effective method of doing that, so it is usually time to get a new frame, if they crack.
Thanks we try and get more info about the frame
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Old 01-13-21, 04:57 AM
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Thanks will try and get more information about the frame. Is your point true about all aluminium frames or do they differ?
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Old 01-13-21, 06:18 AM
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Originally Posted by Smeths View Post
Thanks will try and get more information about the frame. Is your point true about all aluminium frames or do they differ?
It depends on where they crack, there are threads on here where people have welded the rear of their frames, but I am not sure whether they would do the same for the headstock.
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Old 01-13-21, 06:18 AM
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You might ask around some more. I see differing opinions on the "post weld heat treatment".
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Old 01-13-21, 06:31 AM
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Google metal fabrication, there might be a place near you.
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Old 01-13-21, 08:04 AM
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Originally Posted by Smeths View Post
Thanks will try and get more information about the frame. Is your point true about all aluminium frames or do they differ?
7005 frames can be welded and aged at room temperature for a month or so to recover most of its original strength. 6061 requires post weld heat treatment to return it to anywhere near its original strength. If the repair is in a low stress area or a low risk area, such as chainstay or rear dropout, a repair may be successful without post weld heat treatment. I would not risk welding anything in the head tube area. A failure of a chainstay or dropout may cause a crash or just an inconvenient walk home. A failure at the head tube is most likely a trip to the hospital or possibly death. This is not a place for opinions, metallurgy is a science and these things have been tested by people who specialize in that science.
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Old 01-13-21, 08:18 AM
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I've welded 6061-T6 and can guarantee you that the metal is much lower in strength after welding, in the heat affected zone. It's also easy to anneal this alloy, with a propane torch. It only requires around 700 degrees.
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Old 01-13-21, 08:36 AM
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I have seen posts from people that had a head tube failure. One in particular led to a month in the hospital and extensive facial reconstruction surgery. It's not just a figure of speech.
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Old 01-13-21, 10:25 AM
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Originally Posted by dsaul View Post
7005 frames can be welded and aged at room temperature for a month or so to recover most of its original strength. 6061 requires post weld heat treatment to return it to anywhere near its original strength. If the repair is in a low stress area or a low risk area, such as chainstay or rear dropout, a repair may be successful without post weld heat treatment. I would not risk welding anything in the head tube area. A failure of a chainstay or dropout may cause a crash or just an inconvenient walk home. A failure at the head tube is most likely a trip to the hospital or possibly death. This is not a place for opinions, metallurgy is a science and these things have been tested by people who specialize in that science.
note, @dsaul builds a lot of frames he knows of which he speaks.

More directly, trash the frame, the success factor of a fix is low, the injury factor of a failure is high.
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Old 01-13-21, 10:32 AM
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You should contact both Carrera and the place you bought the bike from. Especially if this is a relatively new bike. Some manufacturers will do something, some won't. If you don't ask them, for certain they won't do anything.
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Old 01-13-21, 10:38 AM
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The Halford's website claims a lifetime frame warranty on the Carrera frames that I looked at. It can't hurt to ask about warranty replacement of the cracked frame.
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Old 01-13-21, 11:06 AM
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I'd like to address something said above - that if the crack is in a 'low stress area' then a simple weld repair might be good enough... well there wouldn't be a crack if it were in a 'low stress area'. Any weld repair is unlikely to be as strong as the original build, and if it cracked, the original build was not strong enough.
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Old 01-13-21, 02:39 PM
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The frame is shot. In the past I tried to get my Aluminum BMX welded and it literally cracked again around the weld. The problem is Aluminum shatters and you get all these micro fractures. The only way it might be possible is to get a whole new head tube welded in, but I have a feeling that's more expensive then what you want to pay.
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Old 01-13-21, 03:07 PM
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I’d ask in the frame builders sub-forum. I’m sure there are people over who can give a definitive answer.

My guess is the entire frame will need to be annealed; not sure if prior or post weld repair.

Then the whole frame needs to be taken back to T6.

How much movement, or if a fixture is needed, will have to be answered by someone who has experience doing this.

Of course the paint will be stripped off first.

Needless to say, you probably need to really really like the frame.

John

Edit added: You do need to make sure there is a crack in the weld and not just the paint.

Last edited by 70sSanO; 01-13-21 at 03:11 PM.
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Old 01-13-21, 06:34 PM
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Unless the bike was raced by Pantani or something I doubt it is worth it and even then I would still just wall hang it. No need to kill yourself over any bike even if it were brazed, raced and signed by Eddy Merckx himself after being blessed by the Pope at the Colnago factory with Tulio Campagnolo also present with a special one off gruppo for the bike.

Any of the modern stuff they are selling on Halfords is most certainly not worth the risk. They are all low initial cost bikes and if they can replace it go for it if not just hang it on the wall or try and recycle it or toss it and get something steel, easier and safer to repair if need be.
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Old 01-13-21, 07:15 PM
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Please don't cross post in framebuilders, enough framebuilders have chimed in already
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