API SPEC 7-1 Drill Collars: High-Strength Chromium Molybdenum Alloy for Demanding Drilling.
Engineered for Extreme Downhole Conditions
API SPEC 7-1 drill collars are precision-manufactured from AISI 4145H chromium molybdenum alloy steel via rotary forging or rolling processes. With controlled trace elements (S≤0.015%, P≤0.020%), these collars deliver 1,200–1,400 MPa tensile strength and HRC 28-32 hardness (ISO 6508-1), making them ideal for directional drilling, geothermal wells, and ultra-deep oil/gas reservoirs (up to 25,000 ft TVD).
Certifications & Key Advantages
- API 7-1 & SY5144-2007 Certified: Compliant with ISO 11961 for sour service (H₂S ≤15 ppm).
- Precision Machining: OD tolerance ±0.005″, ID ±0.003″ (ASME B94.55M).
- Bending Strength Ratios: 2.38:1 to 2.58:1 for optimized weight-on-bit (WOB) transfer.
- Customization: NC23 to NC60 tool joints, 30–31 ft standard lengths.
Technical Specifications
Mechanical Properties
| Property | Value | Test Standard |
|---|---|---|
| Yield Strength | 965–1,100 MPa | ASTM E8/E8M |
| Impact Toughness | ≥50 J @ -20°C | ISO 148-1 (Charpy V) |
| Fatigue Resistance | 10⁷ cycles @ 550 MPa | ASTM E466 |
Material Composition:
- Chromium (Cr): 0.80–1.10%
- Molybdenum (Mo): 0.15–0.25%
- Carbon (C): 0.42–0.48%
Dimensional Tolerances
| Model | OD (in.) | ID (in.) | Weight (lb/ft) | Bending Ratio |
|---|---|---|---|---|
| NC 23-31 | 3-1/8 | 1-1/4 | 22 | 2.57:1 |
| NC 38-50 | 5 | 2-1/4 | 54 | 2.38:1 |
| NC 44-60 | 6 | 2-1/4 | 83 | 2.58:1 |
Thread Connections:
- API Regular/Full Hole: 4 TPI to 5 TPI (threads per inch).
- Torque Capacity: 12,500–35,000 ft-lbs (API RP 7G).
Applications
- Directional Drilling: Maintains trajectory in 12–25° dogleg severity.
- HPHT Wells: Stable in 400°F/30,000 psi environments.
- Geothermal: Resists chloride stress corrosion (Cl⁻ ≤150,000 ppm).
- Mining: Core barrel stabilization in hard rock formations.
Quality Assurance
- NDT Testing: Ultrasonic (ASTM E317) + magnetic particle (ASTM E1444).
- Straightness: ≤0.005″/ft (API 7-1 Sect. 8).
- Surface Finish: 125–250 µin RA for reduced friction.
Competitive Edge
- Lead Time: 20–35 days (MOQ 10 collars).
- Wear Resistance: 15% harder than 4140 steel.
- Traceability: Full heat treatment records (quench & tempered at 1,200°F).
Logistics & Compliance
- Packaging: VCI-coated wooden crates with RFID tracking.
- Certifications: API Q1, NACE MR0175, ISO 9001:2015.
- Export Docs: Mill test reports, NDE certificates, material traceability.
Logical Connectors:
- Comparison: While 4140 steel is common, 4145H offers 15% higher yield strength.
- Example: For instance, NC38-50 collars are used in Permian Basin shale.
- Cause-Effect: Controlled S/P content prevents sulfide stress cracking.
Performance Comparison
| Model | Max Torque (ft-lbs) | Dogleg Severity | Key Markets |
|---|---|---|---|
| NC 23-31 | 12,500 | ≤15°/100 ft | Geothermal, Coalbed |
| NC 38-50 | 25,000 | ≤20°/100 ft | Offshore Oil |
| NC 44-60 | 35,000 | ≤25°/100 ft | Ultra-Deep Gas |
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