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4340 "forged" vs "billet" (and EN40B)

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Re: 4340 "forged" vs "billet" (and EN40B)

Postby Mark O'Neal » Wed Jul 25, 2012 12:24 pm

Forging dies are very, very expensive. Billets are not.
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Re: 4340 "forged" vs "billet" (and EN40B)

Postby Ratu » Fri Jul 27, 2012 2:31 am

What about a cast steel instead?
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Re: 4340 "forged" vs "billet" (and EN40B)

Postby clshore » Fri Jul 27, 2012 1:50 pm

Or maybe one of the nodular cast iron materials?
I have heard that some of these can have comparable properites to forged steel.

3D printing can now create cores and forms with excelent quality.

That still leaves the skill and experience of the foundry, to employ casting and processing technique that yields good parts.
(ie it might take several attempts before a 'good' one is created).

The Saturn 'lost styrofoam' crankshafts were a good example of what could be achieved.

None of these approaches appears to be inexpensive.

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Re: 4340 "forged" vs "billet" (and EN40B)

Postby Schurkey » Fri Jul 27, 2012 2:18 pm

Ratu wrote:What about a cast steel instead?

Folks that advertise automotive "cast steel" parts are lying to you. "Cast steel" is a fancy and expensive way of saying "cast iron" which SHOULD result in lawsuits and recalls, but doesn't.

Very much like General Motors "Armasteel" of years ago--a fancy grade of cast iron.

When someone tries to sell you "cast steel" parts, ask them what the carbon content is. Either you'll never get an answer, or they'll admit that it's over two percent--which is cast iron territory.
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Re: 4340 "forged" vs "billet" (and EN40B)

Postby DaveMcLain » Fri Jul 27, 2012 2:52 pm

I always thought that "cast steel" or "arma steel" was really a fancy way of saying nodular iron. The cast iron used in crankshafts is not the same stuff as is used in blocks, heads etc...
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Re: 4340 "forged" vs "billet" (and EN40B)

Postby Schurkey » Fri Jul 27, 2012 2:59 pm

DaveMcLain wrote:I always thought that "cast steel" or "arma steel" was really a fancy way of saying nodular iron. The cast iron used in crankshafts is not the same stuff as is used in blocks, heads etc...

Armasteel is (was?) a GM trademark for several grades of malleable iron.

"Cast steel" may or may not be a high-quality grade of cast iron. You're at the mercy of Communist integrity on that. Maybe it is, maybe it isn't. Maybe it was last week, but this week's shipment isn't. Maybe the prototypes were, but the production pieces aren't. For the most part, the consumer won't have the material tested...and so the suppliers of "cast steel" can produce whatever they want.

If our government cared about citizens instead of being owned by the Corporate World, the FTC would jump all over "cast steel". The fact that they haven't proves they aren't looking out for OUR interests.
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Re: 4340 "forged" vs "billet" (and EN40B)

Postby CREngines » Fri Jul 27, 2012 6:18 pm

I would say this question would really come down to the grain structure, orientation and purity of both raw pieces. Obviously any billet is superior to the old gm forgings as stated earlier. If the billet has been suitably hot worked (rolled or however they do it) to produce a denser grain that is more elongated and compressed similar to a forging then i would say the diffrence between it and high grade forging with no inclusions or other defects is minimal. If the billet crank is produced from a very poor quality feed stock like a poured ingot or continually cast piece then obviously it is going to be compromised in my opinion. Depends on the use of the word billet. In theory the forging should be stronger because the grain orientation follows the form of the crankshaft better. However i would be willing to bet that a good quality billet crank with like dimensions may be more rigid because it doesnt possess some of the springyness and residual stress of the forging.
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