What are car springs made of?

Just to get some comments flowing, here's a comemnt Howard Clark made about this subject yesterday at the Guild of Metalsmiths Conference in
Hastings, MN:
"Since about the 1950's GM leaf springs have been made from 5160."
Then he goes on to say that "GM COIL springs of that same era are made from 9260". That part was a total surprise to me. 9260 has hardly any Chromium and about 2% Silicon. I asked him if that applied to torsion bars but he said he didn't know.
Howard appears to think of 5160 and 9260 as fairly similar materials (from a usage standpoint) though.
He calls the 5160 "fool proof" for reasons that are clear to many of you. It hardens up easily, whereas the 9260 has to be cooled somewhat faster and, I think, more carefully to get full hardness.
I ain't a knife maker, so I'm not trying to come on as an expert, it's just that I had assumed that "a spring is a spring" (GM-wise).
The only time I use junkyard steel for tools is when I'm not in my own shop. There, I stick to Atlantic 33, S1 and S7 for hot work, 4140 for die work, and W1 for cold working tools just because I got a LOT of it cheap.
Pete Stanaitis
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The story I've heard was that pre-war springs were made from carbon steel, but post-war a lower grade of steed was used and the "spring" was introduced mechanically by compressing the surface of the metal, leaving it in compression and the center in tension; *THOSE* springs could be drawn and worked, but *NEVER* hardened again.
John Kopf
spaco wrote:

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I read a book about suspension spring steels. :) They only talked about the two dozen most commonly used ones. :)
As a summary, 5160 is a real good approximation for everything except railroad car springs then those are more like 1070.
You hardly ever read where all ball bearings aren't 52100 but according to metallurgical sources only the largest balls need to have that much Cr.
The book on springs talked about how important it was for the spring to harden to very close to the same hardness all the way to the core. The spring working together as a whole prevents fatigue cracks. :)
Same with the rollers, balls and bearing races.
ASM's Tool Steels 4th edition... Table 8-2 Page 335 Chromium content versus ball size to obtain proper hardenability: 1/8 to 5/8" ----- 0.75 to 1.05% Cr 5/8 to 1+3/16" -- 1.05 to 1.35% Cr Over 1+3/16" ---- 1.35 to 1.65% Cr
The factory can work with what they get supplied by altering their methods. :)
The steels we see for sale with "designations" were made to fit what those designations call for. The "big boys" like GM don't have to pay for the need for the steel to fit neatly into a special "spec".
Somkeless powder for firearm cartridges is the same way. :) The factory uses straight un-blended powder and adjusts the load to suit the powder. Reloaders buy "canister powders" that are blended to match a preset range.
What do you think? :)
Howard Clark knows his stuff. :) But he was most right when he said "I don't know what it is". ;)
Alvin in AZ
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