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4340 - 2% Nickel-Molybdenum-Chromium-Vanadium Through Hardening Steel

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4340 grade steel is a through hardening steel which in the quenched and tempering condition is capable of high strengths.

Its hardenability is excellent, allowing large section sizes to be heat treated with maintained through hardness.

While 4340 is normally oil quenched, due to the high hardenability, small sections may be air hardened.

4340 has good ductility allowing for hot forming operations to be carried out in the annealed condition.

This grade is not considered weldable by standard methods but it can be welded by more sophisticated methods such as EBW. Pre-heating and post-weld heat treatment is desirable to prevent cracking and compromised mechanical properties.

4340 is also suitable for nitriding which will result in improved fatigue strength.

Size Range

45mm - 405mm Dia

Typical applications of 4340 grade steel

  • Mandrel hanger bodies
  • Connectors
  • Drilling riser bolting
  • Nuts
  • Inserts
  • Tools


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