Non-Magnetic Drill Pipes for Directional Drilling
Non-magnetic drill pipes are critical components in coal mine directional drilling systems, serving as the carrier for measurement-while-drilling (MWD) probes. By providing a magnetically neutral environment around the probe, they ensure the local magnetic field closely matches the earth’s natural field—enabling accurate determination of borehole azimuth and inclination.
These pipes also transmit rotary power from the surface rig and deliver hydraulic fluid to downhole motors, operating under complex combined loads of tension, torsion, and internal pressure.
Key Technical Properties
Relative permeability (μr): ≤ 1.005 — verified by third-party test reports
Non-sparking: Safe for use in gassy or explosive underground environments
High strength: Tensile strength ≥ 1035 MPa, yield strength ≥ 965 MPa
Excellent ductility: Elongation ≥ 36.5% — significantly higher than standard beryllium copper alloys
Corrosion resistance: Suitable for high-H₂S, acidic downhole conditions
Structural Types for Different Ground Conditions
|
Type |
Application |
|
Plain (external flat) |
Stable, competent formations |
|
Helical groove |
Soft, fractured, or water-bearing strata |
|
Triangular helical |
Extremely soft coal seams or highly heterogeneous ground |
Technical Specifications
|
Specification |
Value |
|
Material |
High-strength austenitic non-magnetic steel (P650 grade) |
|
Relative Permeability (μr) |
≤ 1.005 |
|
Tensile Strength |
≥ 1035 MPa (Typical: 1165 MPa) |
|
Yield Strength |
≥ 965 MPa (Typical: 1046 MPa) |
|
Elongation (A) |
≥ 36.5% |
|
Reduction of Area (Z) |
≥ 67% |
|
Impact Toughness (KV₂ @10°C) |
Avg. 154.7 J (Min. 142 J) |
|
Hardness |
38.1–38.9 HRC |
|
Grain Size (ASTM) |
6–8 |
|
Certification |
China Coal Mine Safety Mark (MA Certified) |
Note on Material Grades:
The standard offering uses P650-grade non-magnetic steel, which meets the demanding mechanical and magnetic requirements of deep directional boreholes. For applications with moderate load conditions, P550-grade variants are available upon request—offering a balanced combination of performance and cost efficiency.
Manufacturing Process & Quality Control
Forged on 1800-ton radial forging machine with precise temperature and pressure control
Full heat treatment ensures uniform microstructure and minimal hardness variation (≤55 HBW across section)
Every batch accompanied by material traceability documentation and third-party permeability/test reports (SGS/BV available)
As an OEM supplier for national coal mine safety programs, our non-magnetic drill pipes have been deployed in hundreds of directional gas drainage boreholes across major Chinese mining regions, demonstrating reliable performance in depths exceeding 1,500 meters.