I've been looking for ways to create 15x10 wheels for my Challenge car and remembered having some Cragar S/S wheels on my car 40 years ago. Those wheels have aluminum centers welded to steel rims. So, does anyone know what kind of sorcery is involved in doing that? I'm NOT considering doing it myself...it just came up as I was exploring other options.
I believe it can be done with gunpowder or some other 'flash-bang' type exothermic reaction, but that's it.
No idea what the real process or engineering behind it is called, but there's a reason it is not done often.
It would have to be an interference fit to keep them from separating. Probably a heated barrel and a chilled center with one shot to get it right, but that sounds like a really expensive way to make an inexpensive wheel. Are you sure there may not have been rivets or other fasteners thru the barrel into the center section. That sounds more cost effective...
In reply to stafford1500 :
Positive it's welded. You can still buy the same wheels today, advertised as two piece welded.
https://www.jegs.com/p/Cragar/Cragar-08-61-Series-S-S-Super-Sport-Wheels/755662/10002/-1
Looks like bimetallic inserts are the preferred method for structural applications but there's a couple other possibilities such as dip coating.
https://www.esabna.com/us/en/education/blog/can-i-weld-aluminum-to-steel.cfm
In reply to DeadSkunk (Warren) :
The advertising group may be playing a little loose with the definition of welding. Its possible it is chemically welded (adhesive) instead of mechanical welding (torch, filler, etc)
DeadSkunk (Warren) said:In reply to stafford1500 :
Positive it's welded. You can still buy the same wheels today, advertised as two piece welded.
https://www.jegs.com/p/Cragar/Cragar-08-61-Series-S-S-Super-Sport-Wheels/755662/10002/-1
Reading the description gives a clue: chrome plated steel and chrome plated aluminum. That gets you at least common material for the weld junction.
I just want to say that, in looking for an answer I found this discussion which includes this awesome comment:
Some stone cold badass said:
I used to machine explosively welded aluminum to steel plate. They were used for faying strips welded between the steel decks and aluminum superstructures of Naval vessels. They used to use a steel combing riveted to the aluminum strucure but that was unsat over time.
This aluminum welded to steel took place in the woods not far from Port Angeles, WA. They had a huge hunk of slavaged battleship armor 10 ft wide and 40 ft long and over a foot thick set up on timber cribbing. They lay the steel plate on it sprinkled on something granular to maintain the critical spacing, then the aluminum plate, then a sheet of high explosive. It was detonated from one end with a special arrangement of matched detonators to generate a plane wave that ran like a ripple to the other end of the aluminum plate. In the space of 0.020" five million PSI accelerated the aluminum plate to supersonic velocity and struck the steel. The clean, sand blasted surfaces semi-melted and stirred together in some way that formed a strong fusion bond.
Those explosive welding people had it down to a science. It went off with a hell of a bang, the big hunk of armor dipped and jumped, and the welded plate just sat there as a billow of reddish smoke rolled up and drifted off. The bonded joint had hard spots with a peculiar grainy undulation in the fusion line.
We parted it off on a planer into 1" wide strips 12 ft long. It was tough on parting tools and we'd break one or two every cut. Bandsaw blades wouldn't last over a foot in it. That was 1975. These days we have water jet metal cutting. supersonic garnet doesn't stop for anything.
Richter figured he could do better. Intending to use the Cragar name, he came up with a patented method of mating the wheel’s aluminum spokes and center with the steel rim through pressure casting. As Richter told biographer Art Bagnall, “We determined that a stock wheel was permanently distorted at 26,000 pounds (of pressure)…by changing spoke depth and rim location, we were able to attain a minimum static load strength of 41,000 pounds.”
Specifically, the manufacturing technique that Richter employed involved taking the chrome rim, which was selected for being impervious to high impacts and side-directed thrust forces, and making it the focus of the wheel’s overall strength. In a break with then-common industry practice, no rivets or drive screws were used to attach the rim to the wheel’s center section. Five steel locking clips, one for each of the wheel’s spokes, were cast into the center section. Each of the steel locking clips was then welded to the wheel’s steel rim.
In reply to No Time :
Simple, once you see it explained.
In reply to DeadSkunk (Warren) :
I really wish it was the explosive process ¯\_(ツ)_/¯ mentioned 
In reply to ¯\_(ツ)_/¯ :
So...when will you be trying it?
Not as cool as the explosive method, but Mazda has been joining steel and aluminum for about 14 years using a friction method:
the early wheels I have seen used cast aluminum centers with metal brackets cast in ,
that is what is welded to the steel outers
I have also seen steel rivets to connect the cast part to the steel outers ,
Wikipedia has a longer and more generic description of the Mazda process here https://en.m.wikipedia.org/wiki/Friction_stir_welding
californiamilleghia said:the early wheels I have seen used cast aluminum centers with metal brackets cast in ,
that is what is welded to the steel outers
I have also seen steel rivets to connect the cast part to the steel outers ,
This is the proper answer for the original question.
Rons said:Wikipedia has a longer and more generic description of the Mazda process here https://en.m.wikipedia.org/wiki/Friction_stir_welding
We've done this at work for fun with our CNCs.. it's a cool process.
Considering the reactants are already iron oxide and aluminum, I wonder if exothermic welding (thermite welding) would work. Probably would need some super custom one-off graphite moulds and I'm not sure how the aluminum oxide slag would react with the aluminum center.
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