Non-magnetic Drill Collars
According to API Spec.7 and SY/T5144, the non-magnetic drill collars are made of low carbon stainless steel, which are researched and developed independently by our technical personnel, With excellent lower Magnetic permeability, high strength of mechanical properties and outstanding resistant to stress corrosion cracking and no tendency to galling.
All threads are cold rolled, and machined with CNC Lathes –Double –shouldered, including some special threads.
Standard size for non-magnetic drill collars
Mechanical property :
|
Range of outer diameter |
σ0.2 (Mpa) Yield intensity |
σb (Mpa) Tensile intensity |
σ4 (%) Elongation |
|
|
mm |
inch |
|||
|
79.4~171.4 |
3 1/8~6 3/4 |
≥758 |
≥827 |
≥18 |
|
177.8~279.4 |
7~11 |
≥689 |
≥758 |
≥20 |
Magnetic property ( magnetic field = 1 x 05/4πA/m)
Average : Ur < 1.010
Magnetic field gradient : ΔB≤0.05μT
Anti-Galling treatment:
Drill collar threads are phosphatized or copperized in order to lower the possibility of connection galling.
Cold rolling thread roots ：
Drill collar thread roots and stress relief features are cold rolled, which is helpful to reduce the fatigue failure of threads by minimizing crack initiation.
