Date: Mon, 11 Dec 2000 11:51:23 -0700
Reply-To: Keith Adams <keith_adams@TRANSCANADA.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Keith Adams <keith_adams@TRANSCANADA.COM>
Organization: TransCanada
Subject: Re: Stainless Steel Head Studs
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OK, Matt, now you've ticked me off... *kidding*
As a metallurgist, your statement is fraught with mis-truth.
Stainless steels, just like carbon steels, run the full gamut of strengths and hardnesses. Most stainless steels are in fact stronger than carbon steels and have a higher hardness. It's just their properties are
much different. Ever tried to cut stainless steel with a hacksaw? It'll take a month of Sundays to get through it. Just different than carbon steels, that's all.
Examples:
plain low carbon
AISI 1020 Carbon steel - UTS 55 ksi, YS 30 ksi, EL 25%
high strength low alloy (HSLA)
AISI 633 Grade E2 - UTS 75 ksi, YS 55 ksi, EL 23%
plain carbon, quench and tempered (Q&T)
AISI 1080 - UTS 116-190 ksi, YS 70-142 ksi, EL 13-24%
alloy steel, Q&T
AISI 4340 - UTS 142-284 ksi, YS -130-228 ksi, EL 11-21%
Stainless
ferritic
AISI 409 - UTS 65 ksi, YS - 35 ksi, EL 25%
austenitic
AISI 316L - UTS 80 ksi, YS - 35 ksi, EL 50%
martensitic
AISI 410 - UTS 70 ksi, YS - 40 ksi, EL 30%
precipitation hardenable
AISI 17-7PH - UTS 130 ksi, YS - 40 ksi, EL 35%
above is solution treated
AISI 17-7PH - UTS 215 ksi, YS 195 ksi, EL 9%
where:
UTS = ulitmate tensile strength
YS = yield strength (onset of plastic deformation)
EL = elongation in 2" gauge length
Hardness correlates with yield strength (hardness is merely a yield strength test in a localized and microscopic fashion). The higher the yield strength, the higher the hardness.
Now, I don't see anything in those numbers which explain that stainless is any worse than carbon steel. It's just that since stainless is more expensive, people tend to "cheap out" and get the lowest grade, rather
than the grade that is suitable. As noted above with the hacksaw example, stainless is very tedious to machine (I also used to work as a machinist) so tooling costs go up, and so does the time per part. Also more
tedious to weld. Stainless steels are more complicated than carbon steels for many reasons. For this reason, they are rather misunderstood.
Keith Adams
Metallurgical Engineer
Calgary, Alberta, Canada
1986 Vanagon GL Westfalia "Roxy"
Matthew Pollard wrote:
> Hey- wait a second here. Stainless is not as strong as steel! That is why you can't use stainless fastners when you build a house (but ok for the top of decks or fence boards). I would stick with what VW tested
> and knows about. The use of stainless is apealing but is actually a fairly weak and soft metal.
> Cheers
> Matthew
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