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# Non-Magnetic High-Strength Drill Collar
The non-magnetic drill collar is crafted from low-carbon high-chromium manganese alloy steel that undergoes rigorous chemical composition control and special forging processes. These drill collars possess impressive mechanical properties, featuring high strength and low magnetic permeability. Additionally, they exhibit excellent resistance to intergranular corrosion cracking and abrasion. Non-magnetic drill collars are specifically designed for use in directional drilling alongside Measurement While Drilling (MWD) and Logging While Drilling (LWD) tools. They enable precise magnetic measurement of well trajectories by allowing instruments within the drill string to operate free from magnetic interference. A magnetic measuring device (MWD) functions inside the non-magnetic drill collar, ensuring accurate readings of the Earth's magnetic field without being affected by magnetic disturbances. The measuring instruments are isolated from any interference caused by the Bottom Hole Assembly (BHA) or other steel components in the drill pipe.
## Chemical Composition
Below is the detailed chemical composition of the three grades of non-magnetic drill collars:
| Grade | Carbon (C) | Silicon (Si) | Chromium (Cr) | Manganese (Mn) | Nickel (Ni) | Molybdenum (Mo) | Nitrogen (N) |
|-------|------------|--------------|---------------|-----------------|-------------|------------------|--------------|
| W-1 | ≤0.08% | ≤0.8% | 13.5–16.5% | 16.0–18.5% | 1.0–3.0% | 0.40–0.85% | 0.25–0.40% |
| W-2 | ≤0.03% | ≤0.8% | 13.0–16.0% | 18.5–22.0% | 1.0–3.0% | 0.40–0.80% | 0.30–0.45% |
| W-2 | ≤0.03% | ≤0.8% | 16.5–18.5% | 18.5–22.0% | 1.0–3.0% | 0.40–0.80% | 0.50–0.80% |
## Mechanical Properties
The mechanical properties of these drill collars vary based on their grade and outer diameter ranges:
| Grade | Outer Diameter Range (mm) | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Charpy Impact Work (J) | Hardness (HB) |
|-------|----------------------------|----------------------|------------------------|----------------|-------------------------|---------------|
| W-1 | 79.4–174.6 | ≥758 | ≥827 | ≥20 | ≥85 at 21°C | 285–400 |
| W-1 | 177.8–279.4 | ≥689 | ≥758 | | | |
| W-2 | 79.4–174.6 | ≥827 | ≥896 | ≥25 | ≥150 at -25°C | 285–365 |
| W-2 | 177.8–279.4 | ≥758 | ≥827 | | | |
| W-3 | 79.4–174.6 | ≥965 | ≥1034 | ≥20 | ≥100 at -25°C | 300–400 |
These specifications ensure that the non-magnetic drill collars not only meet but exceed industry standards for durability, strength, and performance under demanding conditions. Each grade is tailored to specific drilling needs, providing optimal solutions for various applications.