maybe that helps

4340 High tensile steel
C Si Typical Analysis Mn Ni Cr Mo S P
(Ave. values %)
0.40 0.25 0.70 1.80 0.80 0.25 0.025 0.025

standards

DIN: 1.6565
34CrNiMo6
BS: ~En24
~ 817 M 40
AISI: 4340

APPLICATIONS
Components for the aircraft, automotive and general engineering industries eg.
Propeller shafts, connecting rods, gear shafts, and other automobile parts. Heavy
forgings, eg. Rotors, shafts, discs.
Forge 850-1050oC, slow furnace cool.
Normalize 850-880, air cool.
Anneal 650-700, Cool slowly in controlled furnace
Stress relieve
In the quenched and tempered condition, about 30-50oC
below the tempering temperature. Air cool.
In the annealed condition, 600-650oC. Air cool.
Harden 830-860oC, oil quench
Temper
540-680oC hold for 1 hour min. at temperature, air cool.

HEAT
TREATMENT
Nitride Suitable for both liquid and gas nitriding.