Tig welding alloy wheels

[PhillipM]

It is not as strong as it originally was.
And you don't know exactly how strong it is, compared to how it should be, when you send it out of the door.
Dye-pen isn't going to help you there.

Okay, fair enough for a bit of kerb rash repair, but for me, now way, not on structural cracks.

 

[Rocketman]

Internal stresses aren't so much by design but just what happens when you make stuff. Differential cooling is more about trying to minimise these stresses as, left on its own, different areas of a casting or forging etc will cool at different rates due to variations in wall thickness etc

Bottom line is that the best and most experienced welder in the known universe cannot weld an aluminium wheel without locally ruining it metallurgically. Many (most?) alloy wheels ARE heat treated, both solution treated and artificially aged. As soon as they're heated above the artifical aging temps (ballpark of 180ish Celsius for the common flavours) the mechanical properties start to change, and not for the better. If the wheel in question was flowformed rather than a 'straight casting' then the properties will be reduced even more as flowforming is akin to forging i.e. it imparts a grain structure improving mechanical properties over the random grain structure of a raw casting or weld.

http://www.procast.ca/alloy-information-aluminum-a356-0.php lists mechanical properties for a common flavour of cast aluminium in the as cast condition as well as solution treated and aged. Note the yield strength more than doubles and the % elongation (ductility) increases after heat treatment...

Wheel specialists painters* with a TIG get away with repairing alloy wheels because 1) like everything they were designed with a safety factor and 2) if (often when) the repair fails the wheel usually just cracks again and said crack(s) are discovered when looking for the source of the slow puncture if they aren't picked up sooner (before the cracks grown into the bead seat) during a service or MOT etc

There's several threads about the subject scattered around the forum, here's one of them that goes into a bit more depth regarding the flavours of aluminium and common heat treatments used by various different manufacturers... http://www.mig-welding.co.uk/forum/threads/cracks.27163/#post-297002 I didn't include much in the way of links in that thread as the articles in question are always moving or disappearing as manufacturers tweak their sites but here's one from MB whose wheels are made by various different companies including O.Z. Austria AluGuss aka Borbet, Ronal, Mahle (i believe) and maybe only older/forged stuff Otto Fuchs. Basically the same suspects that make wheels for most of Europes car manufacturers http://media.daimler.com/dcmedia/0-921-1285724-1-1287085-1-0-0-0-0-0-0-0-0-1-0-0-0-0-0.html

Ignoring all of the above there are a couple of filler wire alloys specifically made for the repair of the common AlSiMg and AlSiCu castings. They're harder to find than unobtanium. From a metallurgical POV (solidification and liquation cracking) a 4xxx series AlSi wire is the best choice of the commonly available flavours. Not the lightest of reads but this explains why https://app.aws.org/wj/supplement/04-2005-CAO-s.pdf

* not having a pop at painters, i can't paint to save my life but many wheel 'specialists' are either totally ignorant or plain liars as it's not uncommon hear nonsense like the wheel is good as new or the weld is stronger Maybe they've never heard of a HAZ

This is why laser welding is becoming so popular because it has the lowest impact on the surround metal/alloy. If we can't laser weld steel or aluminium injection mould tools it's either insert or remake these days.

 

[Richard.]

So it's okay to bodge a safety critical item so long as it saves you enough money, is that what you're saying?

If so, I could push you some filler in the crack and paint it even cheaper than welding, I'm sure it'll stick the sides of it together somewhat.
No warranty though, of course.

No one mentioned bodge.
People who carry out weld repairs on wheels I'm sure they do it to an excellent standard and take care and pride in there work.
I don't have any doubt with people's welding ability who professionally take these jobs on. My concern is the fact as good as they may be they have no control over the unpredictable HAZ of which they have no choice but to generate if they weld. Even scuffs and scrapes. If it's weld repaired a HAZ is generated. This is where the problems (if any) are likely to come from.

 

[Maker]

This thread seems to be repeating itself now.

 

[Richard.]

This thread seems to be repeating itself now.

I know. 1 liners, smileys and jokes do seem quite appealing now.

 

[Rrunnach]

It is not as strong as it originally was.
And you don't know exactly how strong it is, compared to how it should be, when you send it out of the door.
Dye-pen isn't going to help you there.

Okay, fair enough for a bit of kerb rash repair, but for me, now way, not on structural cracks.

Oops, couple of typos, which should read, which should show up.....

Reason for using dye pen, has nothing to do with checking strength, you would require DT methods, which defeats the purpose of a weld repair.

 

[Richard.]

Ha ha yeah any form of testing regarding it's mechanical strength does kinda defeat the object of repair.
"Hi mate I've sorted that wheel and you'll be pleased to know it passed the bend test"

I'll stick to me nasty bike casings and clean Alu fabs.

 

[Chris Stevens]

No one mentioned bodge.
People who carry out weld repairs on wheels I'm sure they do it to an excellent standard and take care and pride in there work.
I don't have any doubt with people's welding ability who professionally take these jobs on. My concern is the fact as good as they may be they have no control over the unpredictable HAZ of which they have no choice but to generate if they weld. Even scuffs and scrapes. If it's weld repaired a HAZ is generated. This is where the problems (if any) are likely to come from.

Interestingly enough I have never ever seen a previously repaired alloy wheel cracked in the HAZ. If failure occurs a second time its always in the weld area itself. Filler material selection and joint preparation are both very important, and seem to have some bearing on the integrity of the finished repair.

 

[Rrunnach]

If it's weld repaired a HAZ is generated. This is where the problems (if any) are likely to come from.

Surely this applies to any weld, whether repair or not, Richard?

 

[Chris Stevens]

Oops, couple of typos, which should read, which should show up.....

Reason for using dye pen, has nothing to do with checking strength, you would require DT methods, which defeats the purpose of a weld repair.

I saw some Xrays of a repaired wheel a few years back, and the inclusions and defects in the part of the casting which hadnt been repaired were quite worrying to an untrained eye. Guy at the NDT place though said such defects very common, and not likely to affect safety at all, as things like wheels are always well over engineered...........

Very likely a dye pen test would produce the same result, and might be well worth carrying out just to check and see?

 

[Rrunnach]

Sand traps and inclusions are always a potential problem in the casting process, not just alloy wheels, O&G exotic valves I have seen scrapped prior to machining, returned to foundry for melt down.

Use of dye pen can help seeking out flaws after repair, of course several factors would apply, size of welded repair and, ones interpretation skill level.

 

[Richard.]

Surely this applies to any weld, whether repair or not, Richard?

Your exactly right it does. Some materials are more vulnerable than others to the effects caused by the HAZ. With alloy wheels I believe the manufacturing process plays a bigger part than the material itself. I'll be honest I don't know much about what goes in the various types of alloy wheel which is the biggest reason I don't bother repairing them. Yes cast Alu repairs can be just as much or even more so of a pain and I've had good results from doing them but if the day comes one does fail the worst that will happen is it may spring a drop of oil. And I'll re weld it

 

[Rrunnach]

One could also say, with filler wire manufacture ingredients are added to increase mechanicals within a HAZ area. Maybe Technic Al could offer input regarding alloy wheel repair, which would be interesting input from someone involved in rod design for many applications.

Fair enough not wanting to get involved with wheel repair.

 

[Richard.]

One could also say, with filler wire manufacture ingredients are added to increase mechanicals within a HAZ area. Maybe Technic Al could offer input regarding alloy wheel repair, which would be interesting input from someone involved in rod design for many applications.

Fair enough not wanting to get involved with wheel repair.

I would say a silicon based 4043 filler would be the best chance of a repair. Lower melting point and less sensitive to cracking. Not sure if the Si content would replenish strength in the HAZ but like you say Al and HR would be able to answer that.

 

[Richard.]

Well the prep will vary a lot depending on the defective area. Scuffs will be dished out cracks V'd out.
From a crack sensitive point of view an Si based filler I believe would be the safest bet.
This would be the method and filler I'd adopt purely on my limited knowledge about them.

Rrunnarch what filler do you use when you repair them ?

 

[Richard.]

I'm sure I just replied to a post from Chris S which has just been deleted. So my reply now makes no sense.

 

[Maker]

Sand traps and inclusions are always a potential problem in the casting process, not just alloy wheels, O&G exotic valves I have seen scrapped prior to machining, returned to foundry for melt down.

Use of dye pen can help seeking out flaws after repair, of course several factors would apply, size of welded repair and, ones interpretation skill level.

What are O&G exotic valves?

 

[Richard.]

What are O&G exotic valves?

I believe. Please correct me if wrong. Pressure valves used in petroleum/chemical industry.
I've heard of these refered to as exotic valves.

 

[Paul.]

What are O&G exotic valve

Oil and Gas,
A lot of the valves I use are marked "WOG" for Water, Oil, Gas
http://www.eng-tips.com/viewthread.cfm?qid=27676

 

[Maker]

How did I miss that. Interesting link there too.