I believe that the best material for torsion bars, half shafts and the like
is 300M VAR
which is similar to 4340 but is a higher quality material; less likely to
have inclusions that will initiate fatigue failure.
Heat treatment:
Normalize 1700 F
Austenitize 1660F
Quench in Oil at 140 F Max.
Temper 500 to 600F for 270,000 psi stress level
>From my experience, baking after plating is usually specified as 3 hr. at
375F as opposed to the data on the web site that I referred to earlier. I
suspect that the first 3 hours takes care of the bulk of the problem. Also,
any exposure to acid and electroless nickel processes can result in
embrittlement in very high strength steels, though not to the extent that
electroplating does.
Bill Watkins
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/vintage-race
|