Case Hardening Steel - 18CrNiMo7-6

Welding:

Readily welded in the annealed condition with correct procedure, but welding in the case hardened or through hardened condition is not recommended. 

Welding procedure:

Low hydrogen electrodes recommended.

Pre-heat at 250°C – 350°C and maintain during welding. Cool slowly in ashes, warm dry lime or sand etc, followed when possible with a stress relieve.

Welding details for guidance only

HEAT TREATMENT:  

Forging:

Heat to 1150°C Hold till uniform

Minimum forging temperature 850°C

Cool in ashes, warm dry lime or sand  

Annealing:

Heat to 830°C – 850°C

Cool in furnace  

Normalising:

Heat to 860°C – 890°C

Cool in still air  

Stress Relieving:

Heat to 630°C – 650°C

Cool in still air  

Carburising:

Pack, Salt or Gas carburise at 900°C – 950°C.  

Core Refining:

Heat to 830°C – 870°C

Cool in air or quench in oil or into a salt bath held at 150°C – 200°C and then air cool  

Case Hardening:

Heat to 780°C – 820°C

Quench in oil  

Single Refine:

Suitable for fine grained steels only  

Direct Quench:

Cool from carburising temperature to 820°C – 830°C and cool in air or quench in oil or into salt bath.

Alternatively cool from carburising temperature to room temperature.

Re-heat to 820°C – 830°C and cool in air or quench in oil or into salt bath. 

Tempering:

Tempering at 150°C – 200°C will improve the toughness of the case with minimal effect on its hardness and reduce the possibility of grinding cracks.

Heat treatment details for guidance only