AISI 4340

Low alloy 4340: ASTM A29 (VO1.05)

General scope

AISI 4340 is a low alloy steel containing nominally 0.4% C, 0.8% Cr, 0.25% Mo and 1.8% Ni. Higher strength levels up to 150 KSI 0.2% PS may be achieved by suitable heat treatment. Often used in preference to AISI 4140 at the higher strength levels because of its better hardenability and improved CVN impact toughness.

Due to availability this grade is often substituted with European based standards 817M40, EN24 and 1.6528 34CrNiMo6; which are similar but have a slightly lower nominal nickel content of 1.5% and higher nominal chromium content of 1.3%.

The hardenability limitations of this grade (depth to which it will harden / obtain the specified mechanical properties after heat treatment) must always be taken into account when designing and selecting equipment.

Chemical composition

C Si Mn P S Cr Ni Mo Fe
Min 0.38 0.15 0.60 0.70 1.65 0.20 0.00
Max 0.43 0.35 0.80 0.035 0.040 0.90 2.00 0.30 0.00

Mechanical properties

Condition: Hardened and Tempered

The grade is not approved to NACE MR0175: the nickel content exceeds the 1% max limit specified in NACE MR1075.
U.T.S 150 KSI Min (1035 N/mm2)
0.2% Proof Stress 130 KSI Min (896 N/mm2)
Elongation 13 %
Red of Area 40 %
Size range: 3”∅ - 26”∅

Primarily manufactured in:

  • Dubai, UAE
  • Edmonton, Canada
  • Houston, Texas
  • Sheffield, England
  • Singapore