Specification :

drill collars are manufactured from AISI 4145h or 36crnimo4 modified steel, and are supplied in the" as rolled" surface finish condition. alternative surface finishes can be provided.

trepanning and heat treatment :
drill collars are trepanned and drifted to API spec 7. full-length heat-treatment processes ensure that mechanical properties meet or exceed API spec 7 requirements. a hardness range of 285-341, Brinell hardness and Charpy # 129; gv# 129; h notch minimum impact strength of 40 ft-lb at 70of are guaranteed one inch below the surface.