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Drill collars for oil & gas drilling are manufactured from AISI 4145 modified chromium- molybdenum alloy 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 in accordance with 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 notch impact strength of 40 ft-lb at 70OF are guaranteed one inch below the surface
Drill collar material and process traceability are maintained from receipt of steel mill's certified raw material to completion of all the manufacturing. Serial numbers are die stamped on bar bodies.
Rigid Inspection Procedure
All drill collars are inspected to comply with API standards . These inspections include visual dimensional checks as well as ultrasonic inspections over the entire body of the drill collar
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 plating to improve resistance to corrosion.
Slip groove. elevator groove and size
Optional slip and elevator recesses to improve handling efficiency and safety are available and machined in compliance with API RP 7G guidelines.
Thread protectors are available too.