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BLACK BELT
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Discussion Starter · #1 · (Edited)
How Do I Weld 7020 Aluminum???

My swingarm is made of 7020 aluminum.

The swingarm wasn't made correctly and I had to cut some of it for clearance. Now I need to weld a plate in to fill the cutout.

Can I use a 6061 aluminum plate to fill the cutout, or does it need to be 7020?

Do I need to use welding rod specifically for 7020?

If I do use a 6061 plate to fill the cutout - will it look different than the 7020 aluminum after polishing?

THANKS!
 

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sickboy
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3,544 Posts
There is no 5150 aluminum.

In the 5000 series there is 5005, 5052, 5059, 5083, 5086, 5154, 5356, 5454, 5456 and 5754.

Do you mean 5154?

Honestly it doesnt really matter all that much exactly what particular alloy it is, yes you can use 6061 to patch, being that its a swingarm, use ER5356 filler as it will give you the most strength out of your 6061 patch.
 

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BLACK BELT
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Discussion Starter · #3 ·
Re: How Do I Weld 7020 Aluminum???

Sorry about that.

I guess my memory is going. The swingarm is 7020 aluminum.
 

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sickboy
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3,544 Posts
Re: How Do I Weld 7020 Aluminum???

Sorry about that.

I guess my memory is going. The swingarm is 7020 aluminum.
Oh ok, that makes more sense but still holds true with what I said above.
5xxx,6xxx and 7xxx series aluminum are all magnesium based alloys so a high magnesium based filler rod such as the 5356 will work well. You do want to use plenty of filler rod though as the 6061 patch is a magnesium/silicon (which makes it heat treatable if desired) based alloy so the 5356 filler will help dilute the silicon in the 6061 base metal and make for a more crack resistant weld.

After re-reading what I typed it sounds so convoluted so just to sum up... welding 6061 to 7020 = yes... Filler rod = 5356 and use plenty of it to reduce risk of cracking... Heat treating should not be necessary.
 

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CB350Cafe first build
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393 Posts
Not a welder but wondered if would you need any sort of backing gas for a purge while welding? Not trying to hijack...just curious. EDIT: also is there any preheat involved and special cooling rates/controls after welding?
 

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sickboy
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Not a welder but wondered if would you need any sort of backing gas for a purge while welding? Not trying to hijack...just curious. EDIT: also is there any preheat involved and special cooling rates/controls after welding?
Nope, you do not need to back purge aluminum. Only stainless and chromoly need to be back purged. And technically Ti, but Ti should really be vacuum welded with zero oxygen in any sort of structural scenario.

As far as preheat I doubt the swingarm is thick enough to need preheat. As for cooldown it will be fine to just cool naturally, no post heat/cooldown needed and no heat treating necessary.
 
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