Ued mild steel for years and years and have several that were crash tested
and kept everyone safe and healthy.`
----- Original Message -----
From: <portermd@zianet.com>
To: <Fot@autox.team.net>
Sent: Friday, May 14, 2004 9:46 PM
Subject: Re: Roll bar material
> MARK J WEATHERS writes:
>
> > low carbon steel and mild steel and 1020 etc are the same basic thing.
I
> > have no idea what chrome-moly steel is either but it sounds cool when
you
> > say it.
>
> Sounds like a need for a terminology post. You're correct that
low-carbon
> steel, mild steel and 1020 are roughly the same thing. But, 1020 is a
> specific grade of mild steel, just as 1010 and 1012 are. The 1000 series
is
> composed of all low-carbon, malleable steels, with slightly varying
amounts
> of carbon and alloying elements.
>
> "Chrome-moly" steel is usually the term for AISI 4130, although it can
also
> mean 4140. Ask for chrome-moly tubing and you'll likely get 4130, since
4140
> is normally used not for tubing (doesn't draw quite as well as 4130) but
is
> used in billet form for cranks, etc.
>
> ERW stands for electric resistance welded. This grade is probably
> permissible under some rules for roll bars, but will probably require a
> thicker wall to meet the rules than seamless. Seamless, of course, is
> considerable more expensive. If you can't afford the weight, check the
rules
> and see if a lighter wall seamless is equivalent to a heavier wall ERW.
ERW
> is rolled and the seam electrically welded--therefore, it's not quite as
> strong as seamless, if all other specifications are the same.
>
> I may have mentioned previously that while the rules may allow 4130 for
roll
> bars, it's not recommended, for a couple of reasons. Because of the
> extremely low elongation of the material, the difference between the
points
> of yield and failure is small--that means that if it fails, it doesn't
bend
> much--it snaps. Pieces of it can break loose and become spears. Not
> something I'd like in a roll cage. The other detriment in fabrication is
> that the material work-hardens with welding, and requires rather uniform
and
> precise annealing for at least a foot each direction from each weld.
> Difficult to do with a large piece such as a roll bar or cage, and
> especially so if some of the welding has to occur in the car.
>
> Mild steel, because of its malleability, yields much more easily, but it
> doesn't fail catastrophically--it gives, bends, bends some more, all the
> while absorbing energy. It welds easily and doesn't require extensive
> annealing because it doesn't have enough carbon in it to noticeably
> work-harden.
>
> Cheers.
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