Materials:
Drill collars are manufactured from AISI 4145H modified steel, and are supplied
in the "as rolled" surface finish condition. Alternative surface
finishes are available.
Trepanning and Heat Treatment:
Drill collars are trepanned and drifted to API Spec 7-1. Full-length
heat-treatment processes ensure that mechanical properties meet or exceed API
Spec 7-1 requirements. A hardness range of 285-341, Brinell hardness and Charpy
"V" notch minimum impact strength of 40 ft-lb at 70 F are guaranteed
one inch below the surface.
Traceability:
Drill collar material and process traceability are maintained from receipt of
the mill's certified raw material to completion of manufacturing. Serial
numbers are die stamped on bar bodies.
Rigid Inspection Procedures:
We inspect all our drill collars to ensure compliance with API SPEC 7-1
standards. These inspections include visual dimensional checks as well as
ultrasonic inspections over the entire body of the drill collar.
Cold Rolling:
Drill collar thread roots, as well as elevator recess upper radius, are
cold-rolled. Cold rolling creates a compressive recess upper radius stress
condition that increases fatigue life by minimizing crack initiation.
Phosphate-coated or Copper Plating:
All connections are phosphate-coated or copper plated to improve resistance to
corrosion.
Slip Groove, Elevator Groove and Size:
Huanjie offers optional slip and elevator recesses to improve handling
efficiency and safety. Unless otherwise specified, slip and elevator recesses
are machined in compliance with API spec 7-1 guidelines.
Thread Protectors:
Our company offers steel, cast steel and plastic steel thread protectors for
its drill stem products.