Project Description
Introduction to P750 Non-Magnetic Drill Collar
The P750 non-magnetic drill collar is a high-strength, austenitic Cr-Ni-N stainless steel specifically engineered for extreme downhole environments. As a premium grade within the non-magnetic steel specifications, its advanced chemical composition guarantees exceptional mechanical strength, superior pitting corrosion resistance comparable to nickel-base alloys, and high fatigue endurance. The controlled high chromium, nickel, and nitrogen contents ensure robust austenitic stability under severe stress.
The material’s low magnetic permeability (μr < 1.001) eliminates magnetic interference, making it the definitive choice for directional drilling applications where MWD and LWD tools require a clean magnetic space. Achieving its robust yield strength through a specialized full-length cold-working process, P750 represents the pinnacle of high strength non magnetic austenitic steel collars, ensuring reliability and safety in the most demanding drilling operations.
Equivalent Grades and Trademarks
| Standard / System | Grade / Trademark |
|---|---|
| API Spec 7-1 | P750 |
| ASTM A1718 | P750 (Equivalent) |
| NACE MR0175 / ISO 15156 | Austenitic Cr-Ni-N Steel (S compliant) |
Applications of P750 Non-Magnetic Drill Collar
Specifically designed to minimize magnetic distortion near sensitive downhole electronics, P750 is utilized in the following downstream products and scenarios:
- MWD & LWD Drill Collars: Housing and structural components for MWD tools and LWD non-magnetic components.
- Non-Magnetic Stabilizers: Downhole stabilizing tools that require strict magnetic neutrality within the BHA.
- Non-Magnetic HWDP (Heavy Weight Drill Pipe): Transition pipes between standard drill pipe and drill collars in directional wells.
- Directional Drilling BHA Components: Primary structural string components for horizontal and extended-reach wells.
- Custom Cut NM Bars: Solid P750 material cut to length for bespoke downhole tool manufacturing.
Specifications and Standards
P750 non-magnetic drill collars and bars are manufactured and tested in strict compliance with the following international standards:
- API Spec 7-1: Rotary Drill Stem Elements (Primary standard for drill collars).
- ASTM A1718: Standard Specification for High-Strength Austenitic Stainless Steel Bars for Downhole Applications.
- ASTM A262: Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels (Practices A and E).
- ASTM E114: Standard Practice for Ultrasonic Contact Inspection (100% volume UT inspection).
- NACE MR0175 / ISO 15156: Sulfide Stress Cracking resistant material for sour gas environments.
Product Shapes: Solid Round Bars, Drill Collars, Heavy Weight Drill Pipe (HWDP).
Available Sizes and Delivery Options
As a single-source manufacturer, ShunFu Metal provides comprehensive dimensional flexibility for P750 non-magnetic drill collar materials. We supply forged round bars and drilled collars across a broad OD spectrum, accommodating yield strength requirements of 140 ksi (OD up to 9 1/4") and 130 ksi (OD 9 1/2" and larger).
Our manufacturing capabilities are supported by API-standard regularly calibrated heat treatment furnaces and advanced precision machining equipment, including BTA deep hole boring machines, CNC lathes and milling centers, and long-distance gunhole drilling systems—ensuring we meet the strict demands of precision machining non magnetic drill collars.
Lead Times and Minimum Order Quantities (MOQ)
- Ready Stock (Common sizes): Single-piece MOQ, approximately 7-day delivery.
- Custom Forgings / Rolled Bars: MOQ of 3 tons, approximately 30-day delivery.
- Small Batch Special Grades: 3–5 ton minimum, processed via our small induction furnace.
- Large Volume Orders: 30–60 tons via EAF, fast delivery turnaround available.
Chemical Composition
The controlled low carbon content combined with high nitrogen ensures austenitic stability and prevents sensitization during warm-forging, forming the foundation of ShunFu non magnetic drill string components.
| Element | P750 (%) |
|---|---|
| Carbon | max. 0.03 |
| Manganese | 1.50 – 3.00 |
| Chromium | 26.50 – 29.50 |
| Molybdenum | 2.00 – 4.00 |
| Nitrogen | min. 0.20 |
| Nickel | 28.00 – 31.50 |
Melting and Processing Routes
ShunFu Metal offers flexible melting routes tailored to project-specific purity requirements. For standard P750 production, we utilize EAF + AOD + LF + VD to ensure low carbon and precise nitrogen control. For enhanced cleanliness and homogeneity demanding higher corrosion resistance, ESR or PESR is available. For the most rigorous downhole applications requiring ultimate structural integrity, we provide VIM + VAR triple-melted material. Customers can negotiate directly with our metallurgical team to select the most efficient and compliant melting route.
Mechanical Properties
Properties are tested at room temperature and achieved by a special cold-working process over the full length of the collar.
| Property | OD up to 9 1/4" | OD 9 1/2" and larger |
|---|---|---|
| Yield Strength (min.) (0.2% offset) | 140 ksi (965 N/mm²) | 130 ksi (900 N/mm²) |
| Tensile Strength (min.) | 150 ksi (1035 N/mm²) | 150 ksi (1035 N/mm²) |
| Elongation (min.) | 15% | 15% |
| Reduction of Area (min.) | 50% | 50% |
| Impact Energy (min.) | 100 ft.lb (135 J) | 100 ft.lb (135 J) |
| Endurance Strength (N=10⁵ min.) | ± 80 ksi (± 550 N/mm²) | ± 80 ksi (± 550 N/mm²) |
| Hardness (Brinell) | 300 – 400 HB | 300 – 400 HB |
| Magnetic Permeability (μr max.) | < 1.001 | < 1.001 |
Heat Treatment Process
| Process Type | Temperature Range | Holding Time | Cooling Method | Purpose |
|---|---|---|---|---|
| Warm Forging + Quenching | Proprietary warm-forging range | Per cross-section thickness | Rapid Quenching (Water/Solution) | Prevent sensitization & intergranular SCC |
| Full-Length Cold Working | Ambient temperature | Continuous process | Air | Achieve yield strength (130/140 ksi) |
Exact warm-forging temperatures and durations are proprietary to ShunFu’s specialized manufacturing process to ensure maximum austenitic stability.
Surface Finish and Machining
ShunFu provides extensive surface processing for P750 collars, executed via CNC lathe and milling, BTA boring, and long-distance gunhole drilling to achieve precise internal diameters. External and connection surfaces are refined through roller burnishing and shot peening (or hammer peening), which induces beneficial compressive residual stress to prevent transgranular SCC and vastly improve fatigue life.
For extreme wear zones, we offer laser cladding at a 6-axis machine. Standard machined surfaces achieve an Ra value of ≤ 1.6 μm, while roller-burnished IDs reach ≤ 0.8 μm. Dimensional tolerances strictly adhere to API Spec 7-1 requirements.
Quality Assurance and Inspection
Operating under API Q1 and ISO 9001 certified quality management systems, ShunFu enforces rigorous pre-production, in-process, and final inspections for every P750 non-magnetic drill collar.
- Magnetic Inspection: 100% tested via proprietary probe-testing using a Forster Magnetomat 1.782 ("Hot Spot" test), certifying relative permeability < 1.001.
- Ultrasonic Testing (UT): 100% volumetric inspection according to ASTM E114 minimum standards.
- Corrosion Testing: Intergranular SCC resistance verified per ASTM A262 Practices A & E.
- Dimensional & Metallurgical: Mechanical tensile/impact testing, hardness mapping, and microstructure validation.
- Documentation: EN 10204 3.1 certificates standard; 3.2 certificates available upon request. Third-party inspection by SGS or TÜV can be arranged.
Packing and Shipping
Black-skin forged bars are securely fastened with steel wire bundling to prevent movement and container damage during transit. For bright-surface and precision-machined drill collars—particularly those with roller-burnished IDs and CNC-machined connections—we apply multi-layer protective wrapping to preserve surface roughness and dimensional integrity. All products are coated with heavy-duty anti-rust oil, guaranteeing complete protection against seawater corrosion throughout overseas shipping.
Frequently Asked Questions
Can you supply P750 drill collars strictly to API specification?
Yes. As certified API spec non magnetic drill collar suppliers, all our P750 collars fully meet API Spec 7-1 requirements. 100% magnetic permeability and ultrasonic volumetric testing are certified with printouts per API standards.
What is the minimum order quantity for P750 non-magnetic drill collars?
For standard sizes from our ready stock, we accept single-piece orders with a 7-day delivery. For custom non magnetic drill collar manufacturing or specific forged dimensions, the MOQ is typically 3 tons with a 30-day lead time.
How does P750 prevent intergranular stress corrosion cracking (SCC)?
Material sensitization is prevented by rapidly quenching immediately after warm-forging. Furthermore, transgranular SCC on connection threads is prevented by our mandatory surface compression treatments, including shot peening, roller burnishing, and hammer peening.
Do you offer laser cladding for non-magnetic drill collars?
Yes. We provide advanced wear protection via laser cladding executed on our 6-axis machining center, ideal for extending the service life of critical collar sections in abrasive directional drilling environments.
Request a Quote for P750 Non-Magnetic Drill Collars
Looking for reliable P750 non-magnetic drill collar solutions for your directional drilling projects? ShunFu Metal provides certified materials, precision machining, and comprehensive quality assurance to ensure your downhole operations succeed without magnetic interference.
Contact ShunFu Metal to Request a Quote