"Here are a few shots of a 1936 Ford Tudor Sedan built for and owned by Allegheny Ludlum Steel. It was featured in a local parade with over 100 of our salaried, hourly and retired employees walking alongside. This is 1 of only 4 in existence and is the only one currently in running & in road worthy condition. The car is in exceptional condition, with the interior and even the frame looking great. All 4 cars each had over 200,000 miles on them before they removed them from service. These cars were built for Allegheny as promotional and marketing projects. The top salesmen each year were give
n the honor of being able to drive them for one year. The v-8 engine (max 85 hp) ran like a sewing machine and WA S surprisingly smooth and quite. I thought this was a much better looking automobile than the Ford Thunderbird that visited us last year. FYI, the car was insured (we were told) for the trip to Louisville via covered trailer for 1.5 million dollars. People were told that the dies were ruined by stamping the stainless car parts, making these the last of these cars ever produced. More information of the history on these automobiles can be found at Allegheny Ludlum's website."I think it looks nice, much better than if it had been chrome or something super-glossy like that.
Given that rust is always such a problem with cars, I wonder why stainless steel has not been used more? Too expensive? Too hard? (The post above hints at the latter.) (Bert?)
Very COOL!! I'm imagining a Bentley http://www.rrab.com/sep98.htm#top done up like that, right now!! :-)
ReplyDeleteOr...even a Corvette http://www.chooseyouritem.com/classics/files/80500/80766.html...for a newer, sportier look? :-)
Yes, the Bentley would be lovely. Is lovely too.
ReplyDeleteA metallurgist would be the right person to answer your question here, but here's my 2 cents worth.
ReplyDeleteIn general, steel does not lend itself nicely to deep drawing forming operations, such as those used to make automobile body parts. Relatively simple punch and die presses of humongous proportions are used to make such parts.
Basically, you just insert a steel sheet between the punch & die, and ram the punch into the die to shape the part. Things get a little more complicated in practice because of the intricate shaping required at the edges the part, thus requiring the punch & die to have many independently moving parts, etc. This makes the dies extremely expensive to manufacture and maintain. In fact, the set of dies required to make a given car model nowadays represent most of the investment in launching a new car model (the mechanical "platforms" are now often shared among many models).
Coming back to the issue of materials, as I mentioned above, steel is not the easiest material to form using such methods. Aluminum is pretty much ideal for this, as it enters a plastic state when submitted to extreme stresses and flows in the mold during the forming operation, easily yielding perfect parts time after time. Almost as easy to shape as plasticine, just a few orders of magnitude more pressure is required. Unfortunately, aluminum is generally too soft for automobile use, and comparatively much harder to repair.
Unfortunately, steel does not behave like aluminum at all. It tends to harden when heavily deformed, has a tendency to "remember" its previous shape, and will not "flow" nicely in the die. Because of this, specially prepared steel sheets are used for deep forming. Such material has undergone extensive heat treating, was formed with a very specific grain orientation, and is coated with zinc to enhance corrosion resistance and, perhaps more importantly, provide a softer lubricating layer between the steel and the die & punch.
I guess that you now have an idea of where I'm going with all this: making a bare stainless steel car would require forming the finished material in the presses. Without lubricating coatings & such, the stainless steel parts will come out requiring extensive polishing & finishing operations, something that is plainly unthinkable for mass production. The paint on your everyday car does hide an awful lot of what would otherwise be very ugly blemishes...
Add to this that stainless steels (there are dozens of different SS alloys) are generally much harder than plain steel. Many contain chrome, which is very hard and makes such alloys even less cooperative in cold shaping operations. I confess that I have little knowledge on the subject, but I suspect that most SS alloys could not be as easily heat treated and annealed as plain carbon steel.
In a nutshell, using SS is a whole different game. It is noted in the article that the dies for the Ford Sedan in question were destroyed after pressing only four sets of SS parts. This does not imply that such limited use with SS was enough to end the life of the dies, but it certainly did not help at all.
So, while it is possible to make a car out of stainless steel (such as the Sedans shown here, or the DeLorean), this is likely to remain a practice viable only for limited runs of luxury cars.
The distance between theory and practice is much greater in practice than in theory. ;-)
Perhaps I should add that there is a cost issue as well, SS generally being substantially more expensive than steel. I am however far from certain that, in some ideal world, this would be a real issue.
ReplyDeleteFirstly, the added cost of making SS would likely be much less if there was a massive demand for such material. Mass production tends to level out such differences.
Secondly, a car made out of SS would last much longer, thus further reducing the effect of the added cost.
But in this world, nobody seems interested in making longer lasting products... I wonder why? ;)
There is also a weight issue. Using SS would not reduce the weight of a vehicle (intuitively, I'd even expect the opposite). Since it is easier to achieve even better corrosion resistance using much lighter composite materials, it would be very surprising to see any evolution in the use of stainless steel in this day and age.
But naked sure looks good with cars too.
"But in this world, nobody seems interested in making longer lasting products... I wonder why? ;) "
ReplyDeleteHah, yeah.
Very few people, and me neither, ever buy anything at all to last more than five years. So it's hard to charge for such endurance.
"Since it is easier to achieve even better corrosion resistance using much lighter composite materials, it would be very surprising to see any evolution in the use of stainless steel in this day and age."
Oh yes, I agree. It would have been in the past if ever.
Thanks for the briefing, Bert.
ReplyDeleteMe, I'm amazed you can just press any metal into shape. I'd think it would crease like hell.
"Me, I'm amazed you can just press any metal into shape. I'd think it would crease like hell."
ReplyDeleteNot just any metal. Some soft metals like lead or aluminum alloys have a nice plastic behavior, while most steels don't. Hard metals like tungsten simply cannot be cold formed in a press.
In the case of materials like mild steel, extensive material preparation is usually required.
Mind you, it's mostly a matter of pressure. Just about any metal can be pressure shaped, but this often would require pressures impossible to achieve in practice. It is usually much easier and practical to melt and cast hard metals when needed. But there are very surprising machines out there, performing almost unbelievable operations. I once heard of a press in which a straight piece of wax-filled steel tubing was inserted inside a tee-shaped die. By controlling the extremely high pressures applied to both the steel and the wax, the piece would be formed into the shape of the mold (a pipe tee), with absolutely uniform wall thickness. And the finished part would come out of the press at a temperature barely above ambient.
At the other end of the spectrum, so-called exotic steels are used for their unique physical properties, many of which would be altered or even completely lost if subjected to stresses such as those encountered in cold forming operations. Such materials are thus never cold formed, but rather shaped by cutting or grinding operations (i.e. machined).
It is in fact much more accurate to say that only steels intended and prepared for cold forming can be used for such purposes. And even with those, doing so usually isn't easy. For instance, the shape of the die required to produce a given part is likely to be quite different from the shape of the finished part, as steel will spring back to some extent.
It is also worth noting that, especially in the case of steel, the atomic structure of the material can be strongly altered in high deformation areas such as sharp bends. The metal can be altered so significantly that it becomes a different material, from a chemical point of view, with a different electro-chemical potential. This can lead to galvanic corrosion in the presence of an electrolyte.
This is why cars tend to rust "at the seams", i.e. close to the edges of the body parts, where sharp bends are usually found. (Remember the squarish Hyundai Pony or VW Fox rust buckets?)
Such crevices not only tend to retain water, but the presence of "different steels" around the bend combined with water will form a battery, and the resulting electrical current will end up quickly eating through the stressed steel.
A lot of improvement has been observed in this area over the past 30 years, mainly through the introduction of "galvanneal" steels, in which a thin coating of zinc is alloyed to the underlying steel sheeting, providing a much better and more compliant protection against corrosion.
Steel working and forming is truly both a complex science and an art form.
No kidding.
ReplyDeleteI begin to understand why engineers are popular heroes as well as extremely highly paid. :-)
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I heard that wood, under very high pressure and heat becomes like putty, and you can shape it into anything, like tie a know on a plank.
Unfortunately not that well paid! :-(
ReplyDeleteEspecially compared to nose hackers & such. Heck, an independent plumbing contractor can do better than the average engineer.
But indeed, according to polls, engineering is one of the best regarded amongst the liberal professions. Small consolation...
From reading Dilbert, I got the impression that engineers are very low status.
ReplyDeleteBut then I always thought that Mr. Adams is much too cynical.
This is a cool car... but today we'd make the body panels out of either aluminum or plastic.
ReplyDeleteAluminum also doesn't corrode, it's much lighter for the same thickness than steel, and it's easy on dies.
The Land Rover Defender bodies are made from aluminum... what a great idea. That's why you see so many old ones in decent condition... unlike Toyota Land Cruisers or Jeeps, both of which tend to rust out after a couple of decades.