Project Description
Overview of N850 Nonmagnetic Steel
N850 nonmagnetic steel is a premium nickel-chromium-molybdenum alloy, equivalent to Hastelloy C-22HS, engineered specifically for the most demanding downhole environments. As a specialized non-magnetic steel, its core advantage lies in an exceptionally low relative magnetic permeability (≤ 1.005). This ensures absolute minimal interference with MWD and LWD directional sensors, preserving wellbore trajectory accuracy during complex directional drilling operations.
Beyond its magnetic transparency, N850 delivers exceptional mechanical strength. It achieves a minimum yield strength of 1035 N/mm² (150 ksi) through a proprietary cold-working process, while maintaining superior resistance to severe sulfide stress cracking and chloride-induced pitting. It conforms strictly to ANSI/NACE MR0175 / ISO 15156, making it a trusted corrosion resistant alloy for critical drilling operations where both magnetic neutrality and structural integrity are paramount.
Downhole Applications for N850
N850 nonmagnetic steel is specifically designed for downstream products in extreme-service drilling applications where magnetic interference and corrosive fluids are simultaneously present. Its high strength and low permeability make it the preferred material for sensitive directional surveying equipment. Typical applications include:
- Non-Magnetic Drill Collars (NMDC): Providing weight on bit without disrupting magnetic survey tools. Explore our full drill collar products for various downhole weights.
- MWD / LWD Sensor Housings and Mandrels: Protecting sensitive electronic payloads from magnetic distortion and external pressure.
- Non-Magnetic Stabilizers and Reamers: Maintaining wellbore geometry in directional wells.
- Non-Magnetic Drill Pipes and Heavy Weight Drill Pipes (HWDP): Transitioning string weight flexibly; view our standard drill pipe solutions.
- Downhole Logging Tools and Carrier Bars: Ensuring accurate data transmission in high-temperature reservoirs.
- Mining Exploration Drill Rods: Enabling precise directional surveying in mineral exploration.
- Corrosion-resistant Stress Joints: Deep-water Oil & Gas drilling components exposed to high H2S and chloride concentrations.
Specifications & Equivalent Grades
Because N850 and Hastelloy C-22HS are proprietary high-performance alloys, they are primarily governed by manufacturer and customer-specific specifications rather than broad ASTM structural codes. However, the material’s compliance and testing fall under critical industry standards, ensuring reliability in sour service.
| Alloy Designation | Equivalent Tradename | UNS Number |
|---|---|---|
| N850 | Hastelloy C-22HS | N07022 |
- ANSI/NACE MR0175 / ISO 15156: Qualification for sulfide stress cracking resistance in sour oil and gas environments.
- ASTM E114: Standard for ultrasonic inspection, ensuring 100% volume verification against internal defects.
- Product Shapes: Solid Round Bars, Hollow Bars, and Drill Collar Blanks.
Chemical Composition & Mechanical Properties
The carefully balanced chemistry of N850 nonmagnetic steel provides the foundation for its exceptional corrosion resistance and high mechanical strength. The high nickel and molybdenum content ensures resilience against the most aggressive downhole fluids.
| Element | Content (%) |
|---|---|
| C | max. 0.01 |
| Cr | 20.00 - 22.00 |
| Mo | 15.00 - 18.00 |
| Fe | max. 2.0 |
| Co | max. 1.0 |
| Ni | Remainder |
The mechanical properties of N850 are tested at room temperature following our specialized cold-working process. These properties ensure the structural durability required for heavy downhole loading while maintaining strict magnetic compliance.
| Property | Metric Value | Imperial Value |
|---|---|---|
| Yield Strength (min. 0.2% offset) | 1035 N/mm² | 150 ksi |
| Tensile Strength (min.) | 1104 N/mm² | 160 ksi |
| Elongation (min.) | 15% | 15% |
| Reduction of Area (min.) | 50% | 50% |
| Impact Energy (min.) | 135 J | 100 ft.lb |
| Endurance Strength (N=10⁵, min.) | ± 620 N/mm² | ± 90 ksi |
| Hardness Brinell | 300 - 430 HB | 300 - 430 HB |
| Relative Permeability (max.) | ≤ 1.005 | ≤ 1.005 |
Melting Routes, Heat Treatment & Surface Finish
Melting & Processing
For this critical nickel-based alloy, SHUNFU METAL offers flexible melting routes tailored to project criticality. The standard procedure is EAF + AOD + LF + VD. For enhanced homogeneity and purity, we offer ESR or PESR. For the most stringent aerospace or ultra-sour downhole requirements, the ultimate VIM + VAR route is available. Clients can consult with our metallurgists to select the optimal melting solution balancing performance and cost.
Heat Treatment Process
The exceptional mechanical properties of N850 nonmagnetic steel are achieved through a specialized cold-working process rather than conventional quenching and tempering associated with carbon steels. Stress relieving is applied per customer specification for dimensional stabilization prior to final machining. Specific aging or stress-relieving temperatures are determined based on final OD and customer requirements.
| Process Type | Parameters | Cooling Method | Purpose |
|---|---|---|---|
| Special Cold-Working | Applied over full length | Ambient / Controlled | Achieves min. 1035 N/mm² yield & target hardness |
| Stress Relieving | Per customer specification | Ambient | Dimensional stabilization prior to final machining |
Surface Finish & Machining
SHUNFU METAL provides comprehensive surface finishes and precision machining for N850 downhole components. External surfaces are processed via CNC turning and milling, achieving dimensional tolerances up to ±0.05mm and surface roughness down to Ra 0.8 μm. For hollow bars and drill collars, internal bores are refined using BTA deep hole drilling and long distance gunhole drilling, followed by roller burnishing to achieve superior inner surface smoothness. External shot peening can be applied to enhance fatigue life, and black skin (as-forged) surfaces are available for rough machining by end-users.
Available Sizes & Delivery Options
SHUNFU METAL supplies N850 nonmagnetic steel across a broad dimensional range to accommodate diverse downhole requirements. We provide solid forged round bars and hollow bars (up to 10" OD and larger based on custom requirements), utilizing our advanced manufacturing infrastructure. Our capabilities include API-standard calibrated heat treatment furnaces, CNC lathes, milling machines, and specialized deep hole drilling equipment.
| Order Type | MOQ | Lead Time | Processing Method |
|---|---|---|---|
| Common Sizes (Ready Stock) | Single piece | ~7 days | Existing inventory |
| Custom Forged / Rolled Bars | 3 tons | ~30 days | Standard forge/roll infrastructure |
| Small Batch Special Grades | 3-5 tons | Custom | Small induction furnaces |
| Large Volume Orders | Custom | Custom | 30-60 ton EAF |
Quality Assurance & Packing
Inspection and Certification
SHUNFU METAL, certified by API Q1 and ISO 9001, enforces rigorous quality control across pre-production, in-process, and post-production stages. All N850 nonmagnetic steel drill collars undergo 100% volume ultrasonic inspection per ASTM E114, alongside 100% proprietary magnetic probe testing to guarantee permeability compliance (≤ 1.005). We conduct comprehensive chemical analysis, mechanical property testing, dimensional verification, and metallographic examination. Corrosion testing per NACE MR0175 / ISO 15156 is verified. We issue EN 10204 3.1 certificates as standard; 3.2 certificates are available upon request. Third-party inspections by SGS or TÜV can be seamlessly arranged.
Packing & Shipping
Black skin (as-forged) N850 bars are securely fixed with steel wire strapping to prevent movement and container damage during transit. For bright-finished and precision-machined drill collars and hollow bars, we apply multi-layer protective wrapping—including VCI anti-corrosion paper and wooden crating—to safeguard surface roughness and dimensional integrity. All products are coated with rust-preventative oil, ensuring absolute protection against corrosion throughout maritime shipping.
Frequently Asked Questions
Can you supply N850 nonmagnetic steel to API specification?
Yes. As an API Q1 and ISO 9001 certified manufacturer, SHUNFU METAL produces N850 in full compliance with API standards for drill collars and ensures the material meets the stringent sour service requirements of ANSI/NACE MR0175 / ISO 15156.
What is the minimum order quantity for N850 hollow bars?
We offer flexible MOQs. For standard sizes, we have ready stock available for single-piece orders (delivery in ~7 days). For custom forged dimensions, the MOQ is typically 3 tons with a 30-day lead time. We also support small batch induction melting (3-5 tons) for specialized requirements.
How do you ensure the non-magnetic properties of N850 meet the ≤ 1.005 permeability requirement?
Every single N850 collar and bar undergoes 100% magnetic inspection using our proprietary probe-testing process, guaranteeing that relative permeability remains at or below 1.005 before shipment.
Is N850 suitable for environments with elemental sulfur and high H2S?
Absolutely. N850 is qualified for extreme sour service. It can safely operate in environments containing up to 1000 psia H2S and 180,000 mg/L chlorides at temperatures up to 288°C (550°F), and withstands 500 psia H2S with elemental sulfur present up to 204°C (400°F).
Partner with SHUNFU METAL for N850 Nonmagnetic Steel
Ensure the accuracy of your directional drilling and the longevity of your downhole tools with certified N850 nonmagnetic steel. Our metallurgists and manufacturing team are ready to support your project from specification to delivery.
Contact Our Engineering Team