Normal Drill Collars

Material Selected
The collars are made of AISI 4145H forging or finish rolling alloy structural steel.

Processing and thermal treatment of the pipe hole
The drill collar are trepanned and drifted to API Spec 7. Grinding crafts adopted finish boring technology eliminates regions of the weld stress concentration, making welding appearance more perfect, and increases their life. The full length thermal treatment ensure the mechanical performances fullfil even exceed API Spec 7 requirements. Its brinell hardness ranges from 285 to 341, moreover, charpy “v” notch minimum impact strength of 40 ft-lb at 70℃ are guaranteed one inch below the surface. 

Traceability
From receipt of mill’s certified raw material to the completion of all the processing, in each process of which complete traceablity mechanism workcraft. Serial numbers are die stamped on bar bodies.

Routine and strict inspection procedures
All our drill collars are inspected to comply with the API standards. These inspections include fluorescent magnetic-particle detection and inner ultrasonic flaw detection and hardness detection over the entire body of the drill collar as well as other mechanical performance detection.

Cold rolling process
The thread roots, as well as the elevator recess, shall be cold-rolled. Cold rolling creates such a compressive upper radius stress that increases fatigue resistance by minimizing crack initiation.

Phosphate-coated or copper plating
All connections shall undergo phosphate-coated or copper plating process to ensure corrosion resistance, so as to avoid galled thread.

Slip groove, elevator groove and size
Our company offers optional slip and elevate and accepts reprocesses orders,  improving the handling efficiency and guarantee safety. Unless special specification is required, slip and elevator are processed in compliance with API rp 7G guidelines.

Thread protectors
Steel, cast steel, and plastic steel thread protectors for the drill stem products are subject to your requirements.

Standard size for drill collars