Ask your WELDING questions here.

more a question about post welding treatment....

my kid has a scooter with a smallish crack in it. it is an expensive deck so I want to try and get it fixed rather than buy a new one. according to interwebs it is made from 6061T6. once it is welded will it need to be heat treated?

tia

g

I just today read a bit about someone repairing a motorcycle swingarm that was 6061. There were differing opinions from "throw it away if you value your life" to "depending on potential stress risers from where the weld is, as compared to the forces on the swinger, it should be OK"

Perhaps post a picture so the better-informed welders can help?

good idea. I'll try and get one soon.

If it was a trail bike, I wouldn't have a issue running that swingarm. O/a heating or not. Lots of welded swingarm extensions that are 12+ inches that have not failed.

Also Honda uses 7xxx series for their extrusions. Lots of guessing in that welding web thread.

Lots of guessing on that site in general not to say my welding projects don't have their fair share of speculation!

First question, why did it crack? From vibration/normal riding or a crash? Your as-welded area gives up a lot of strength--nearly half. The weld area will likely crack again, and sooner. You must use filler metal when welding 6061--no autogenous welding for that alloy. Use 4043.

I think it was general use and jumping it. It started out approx 10mm and is now about 50mm long. got it 4043 filler.
Do you have any experience with gas (oa) welding aluminium? lots of youtube videos showing it being done.....

No. I am much more of a welding engineer than a welder. I've never had the skill for the art of good welding. But there is a lot of science and engineering behind good welds. Yes, OA welding of alum. is fine, but you have to use flux. Many welders think the flux is to take care of impurities in the base metal, but the primary reason is to break down the tough alum. oxide that covers the surface.

If you do proceed to weld it and manage to do it without weld bead cracking, during riding it is very likely to crack again alongside the weld (the HAZ).

We have a compressor at work that started leaking oil. It was from a weld where a foot was welded on for mounting. Coupler went bad and it started vibrating, hence the crack. Tank is 1/2" thick and was full of oil. Curious to see how the person would go about repairing it.

We called a few people to get it repaired and a R stamp for inspection.

From personal experience in commercial applications- welded aluminum will crack again at the weld unless finished and welded correctly. Weld it,then grind off the weld so you don't make a stress point there and call it a day unless his scooter goes pretty fast. The picture will do good in determining stress points.

At one point in time I started welding perpendicular lines across our fender welds,they'd hold longer,but would eventually fail at a weld again and normally follow the thicker bead of repaired aluminum. Those that I ground back flat had much less of a failure rate. By design the fenders flex going down the road. While I'm not an engineer by trade,I'm assuming the thicker welded area was more rigid andthe added stiffness caused the cracks.

I have done a very little bit of gas welding Aluminum with a Henrob torch. the Henrob isn't magic, but the low pressure helps to not blow through the puddle. It works. But, it puts a lot of heat into the piece. This is great for aluminum bodywork, gastanks, stuff that is needs post weld forming as it comes out annealed.

I would think TIG would put a lot less heat into the piece.

Eric

I have a Henrob as well. Only used it a few times but really like it so far. Going out today to try and find the supplies I need.....

6061 T6 is a popular aluminum alloy. You can weld it with 4043 or 5356 filler metal. TIG or MIG weld it. You don't need to heat treat it.

thanks

finally got some time for photos. it's longer than I thought, close to 70mm plus found 2 off shoots as well.

Grind out so it is shinney and weld it.



Sent from my iPhone using Tapatalk

What happens is that the heat affected zone near the toes of the weld is the weak link and that is where the crack happens. Also if there is a thick to thin area it will create a stress riser and through fatigue will crack.


Sent from my iPhone using Tapatalk

Another consideration about weld repairing the 6061-T6 is that the T6 is a heat treated aluminum. The T6 heat treatment is for high strength. The 4043 filler metal is near pure aluminum (i.e. low strength). The 6060-T6, when manufactured, has a strength near mild steel. After heating, the strength of the 6061 drops - because the localized heating (heat affected zone) has removed the heat treatment.

So, after the weld repair a weaker material has a stronger material around the weld area. If that area is highly stressed, then the likely hood of forming another crack is very high. The only remedy for a permanent repair is to reinforce that area or get a new part. Since the original part failed and formed a crack, weld repairing with a weaker aluminum may not last long before failing. However, if the area is not highly stressed and the crack formed from a defect or corrosion, then the weld repair will be permanent. Good luck!

I think I've said it before, but T6 heat treatment isn't rocket science if you can find a temp controlled oven that is big enough & goes hot enough. See here. I looked it up years back after I had an MTB frame bracket welded up. The part didn't break again.

Cheers
Clint

Anyone know of a pair of Miller 5" X-Clamps going cheap? I'm in the middle of making my own welding table with 3/4" slits that will accept them (as I like the theory of them) but I'm buggered if I'm going to pay $40 a pop (and that's the discounted online price). Was pondering cannibalizing a cheap Harbor Freight C clamp (I can make the boss on my lathe) but I'm not sure how effective I'll be at welding cast iron.