AISI 4340

Designation by Standards

Chemical Composition (in weight %)

Description
TORKA is a heat treatable, low alloy steel containing nickel, chromium and molybdenum. It is known for its toughness and capability of developing high strength in the heat treated condition while retaining good fatigue strength.

Applications
Permanently stressed machine, engine and vehicle parts when high strength and toughness are required. Typical applications are for structural use, such as aircraft landing gear, power transmission gears and shafts and other structural parts. 

Physical properties (avarage values) at ambient temperature
Modulus of elasticity [10³ x N/mm²]: 210 
Density [g/cm³]: 7.85

Soft Annealing
A full anneal may be done at 840^oC followed by controlled (furnace) cooling at a rate not faster than 10^oC per hour down to 300^oC. From 300^oC it may be air cooled.

Normalizing
Temperature: 890^oC

Hardening
Harden from a temperature of 830^oC followed by oil quenching.

Tempering
The temperature for tempering depends upon the strength level desired. Before tempering the alloy should be in the heat treated or normalized & heat treated condition. For strength levels in the 260 – 280 ksi range temper at 230^oC.

Forging
Hot forming temperature: 1100-850^oC. 

Machinability
Machining is best done with this alloy in the annealed or normalized and tempered condition. It can be machined by all conventional methods..

Corrosion Resistance 
This is a low alloy steel and not a corrosion resistant alloy. Protective coating should be used.

Welding 
The alloy can be fusion or resistance welded. Preheat and post heat weld procedures should be followed when welding this alloy by established methods.

Cold working 
The TORKA alloy may be cold worked, in the annealed condition, by conventional methods and tooling. It has good ductility.

Forms manufactured: Please see the Dimensional Sales Program. 

Disclaimer
The information and data presented herein are typical or average values and are not a guarantee of maximum or minimum values. Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to make his own evaluation and are not intended as warranties, either express or implied, of fitness for these or other puposes. There is no representation that the recipient of this literature will receive updated editions as the become available.