On 12/27/12 10:19 AM, Mike Ryan wrote:
This is 4130 chrome molly steel tubing. The word tubing is the primary
descriptor I think, in that there is no seam such as you might find when
using some kind of pipe. I bought a half dozen or so 24 ft lengths from
the Dillsburg Aeroplane Works up in Pennsylvania back in the late '80s
when I was putting together a station in northern Virginia. I had them
galvanized before using them. These were 125,000 psi tubes very similar
to the materials used to build racing car safety cages as I recall.
I'm not a metallurgist, but wonder if the heat from the galvanizing (I
assume it was done hot-dip into molten zinc) affects the heat treatment.
While that might not change the alloy composition, it might change the
yield strength.
My little handbook says 4130 cold-drawn is tensile strength 85-110kpsi,
yield of 70-85kpsi.
My understanding is that non-heat treated CrMo is fairly soft (hence the
low yield strength) and not a whole lot "stronger" than 1XXX type
steels. However, if heat treated it's a whole lot stronger (and more
stiff/brittle, as well) so it gets used for suspension components,
axles, and the like.
I suppose that we're constrained by the OD to fit in clamps, bushings,
bearings and the like, but I wonder if a larger diameter tube of cheaper
thinner steel might not be an easier way to go (lifting a 20 foot stick
of 2" tubing with 1/4" wall is going to be a chore). That r^4 term
really helps a lot..
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