alloy wheel welding

[SmartWerks]

Thanks for the info hotrodder.

You can cure at higher temps for a shorter duration but there isn't much in it really, getting the part to temp is the longest part of the cure process so no real advantages curing at a higher temp and I don't believe it is common practice as there isn't any benefits cost and production wise.

As for forged wheels, i believe they are treated at 800 then 400 degrees and the temp required to weaken the alloy is way above the temp required to cure powder. I can't speak for magnesium wheels, hit and miss with regards to war page but they shouldn't if the correct temp is used. But a lot of coaters rely on methylene chloride based strippers which will eat the mag. The blasting required to strip wheels prior to coating can cause heavy pitting which means a lot more prep work and the sort of job you will lose money. From what i have read on mag wheels I wouldn't be happy coating them, to risky and a lot of money to replace and don't have the necessary experience.

 

[SmartWerks]

reading this thread has got me thinking about heat treated wheels and powder coating temperatures, sorry for the hijack :-( I had some marchesini wheels on my last gsxr.. wanted them re finishing and contemplated powdercoat but after researching the process of the construction of forged wheels and learning they where treated at 800 degrees and then at 400 degrees I felt heating them up to around 300 deg wouldn't be a good idea everyone I spoke with said" oh its fine everyone does it " but I didn't like that answer emailed aftermarket wheel companies and they advised on paint so that's what I did.. any thoughts on this guys ?

ROTA had a big problem with their lightweight wheels cracking. A lot had been powder coated by custom coaters and the rumours started circulating that it was the heat of the oven weakening the alloy. It turned out it was a manufacturing fault, process adjusted and problem disappeared. It escapes me the reason, minds a bit off at the moment.

where did you get the figure of 300 degrees? Only 180 degrees to cure, although if not brand new, after stripping they should be out gassed at 200 degrees prior to blasting. Although you can use a red oxide primer if you don't want to outgas the alloy.

 

[hotrodder]

The solution annealing temperature for 6082 is usually quoted as in the range of 510 - 540ºC (950 - 1000ºF, 800ºF = 426ºC). 530ºC / 985ºF are the most common numbers for the various flavours of casting and forging alloys used for wheels. Aging temperatures vary from 150ish to 190ºC with higher temps typically being used for shorter soak times. As soon as you heat an artifically aged aluminium to/beyond it's final heat treatment temp the precipitation process starts up again (overaging). Take it above 230ºC and things start going south very quickly according to many sources... precipitation of coarse grains and a drop in mechanical properties http://www.aec.org/assets/pdfs/webinars/aec_thermaltreatmentswebinarsept2010revised.pdf has a rather complicated graph about 1/4 way down

Description of the production process used for MB wheels (i'm pretty sure the OE wheels on my w124 were made by Mahle, some AMG wheels were made by O.Z.) including temps and times for heat treatment http://media.daimler.com/dcmedia/0-921-1285724-1-1287085-1-0-0-0-0-0-11702-0-0-1-0-0-0-0-0.html

ROTA use a 356.2-T6 for castings and 6061-T6 for forgings IIRC. Stuff from the US & Asia tends to be 6061 where in Europe 6082 is more common, both flavours are very similar chemically, 6082-T6 is a little stronger with similar ductility

As a guess it's sounding like poor temp control from sloppy powdercoaters could maybe 'damage' wheels, on paper at least, and it's more likely to happen if they go nuts outgassing them than when curing powder?