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4145 mod - 1.1% Chromium-Molybdenum Through Hardening Steel

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4145 mod grade steel is a chromium-molybdenum through hardening steel typically used for downhole applications.

Similar to 4140, except with a higher carbon level resulting in greater strength, hardenability and ruling sections, which makes this grade more suitable for applications with larger section size and higher strength requirements.

In the ‘as-quenched’ state, hardnesses of 55-62HRc are achievable.

This grade demonstrates good forgeability but must be controlled through cooling due to its susceptibility to cracking. Care should also be taken when quenching, ensuring control over the quench medium, for the same reasons.

Impact toughness is reduced due to the increased carbon content. Weldability is also poor and is often carried out by more sophisticated methods such as plasma arc or electron beam.

Size Range

32mm - 860mm Dia

Typical applications of 4145 mod grade steel

  • Drill collars
  • Drill bits
  • Crossover subs
  • Tool joints

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Similar Grades

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Grades for Potential Substitution (Greater)