On Jan 1, 11:37 pm, wrote:
On Jan 1, 9:57 pm, wrote:

On Jan 1, 4:32 pm, "Phil" wrote:

Steels aren't hardenable under .40% carbon. 4130 is .30%.

Dan
.

I don't think this is quite true. The data from AR-MMPDS-03 for 4130
and 4135 says the following. It plainly gives the tensile strengths
and other data for 4130 and 4135 heat treated to several different
levels of strength, compared to normalized (no heat treat). This is
the guiding technical standard that all metals in the Space Shuttle,
Space Station, and many other high tech NASA projects are governed
by.
4130 is heat treatable to 180 ksi and 4135 to 200 ksi. The un-
heat treated strength is 75 to 90 ksi. It is true that higher carbon
content (to a point) allows for higher treat heat levels, as the
higher level for 4135 vs 4130 shows.

Regards,
Bud

Didn't say it wasn't heat-treatable. Said it wasn't hardenable.
Hardness is usually linked to crack tendencies. Tensile strength can
be changed with heat-treat, I know, but cracking on aircraft tube
structures, as I understand it, is more due to the cooling and
shrinking of the local area and consequent rise of tension in that
area.

Dan