Our drill collars are manufactured from 4145H modified steel.Drill collars are bored and drifted to API Spec7-1 and fully heated to meet or exceed the mechanical property requirements of API Spec7.Hardness range of 285-341HB and a charpy V  notch impact value of 54joules are guaranteed one inch below the surface.

Stress-relief grooves decease the frequence of fatigue failures by improving the bending strength of pin and box connections and reducing high stress concentrations.Sress-relief features are manufactured in compliance with API Spec7,unless otherwise specified by customers.

Shenlong offers optional elevator and slip recesses to improve handling efficiency and safety.The

upper radius of elevator recess is cold-rolled to increase product life.Slip and elevator recesses can be used together or seperately.Unless otherwise specified,slip and elevator recesses are machined in compliance with API RP7G guidline.