Staballoy AG17 Cr-Mn-N Steel Round Bar

Product Description

Staballoy AG17® is a high-strength, premium nitrogen-alloyed austenitic stainless steel engineered by Schoeller-Bleckmann Oilfield Equipment (SBO). Produced via specific hot-forging routes and occasionally refined via electroslag remelting, it belongs to the specialized family of $\text{Cr-Mn-N}$ alloys designed specifically for downhole drill string components in the oil and gas industry.

The fundamental objective of Staballoy AG17 is to deliver an exceptionally high yield strength alongside absolute non-magnetic reliability, protecting sensitive downhole instrumentation from magnetic interference while resisting aggressive downhole corrosion.

Chemical Composition (Nominal % Limits)

Staballoy AG17 balances high manganese to stabilize the austenitic matrix, high chromium and molybdenum to combat chloride-induced pitting, and a rich addition of nitrogen for interstitial solid-solution strengthening.

• Chromium (Cr): 17.00 – 19.00% (Core pitting and general corrosion resistance)

• Manganese (Mn): 13.00 – 16.00% (Primary austenite stabilizer, replaces nickel)

• Molybdenum (Mo): 2.00 – 3.00% (Elevates resistance to localized crevice attack and chloride environments)

• Nitrogen (N): 0.50 – 0.70% (Interstitial strengthener and austenite stabilizer)

• Nickel (Ni): 1.00 – 2.00% (Improves toughness and structural stability)

• Carbon (C): $\le$ 0.05% (Minimized to prevent chromium carbide grain-boundary precipitation)

• Silicon (Si): $\le$ 0.80%

Critical Technical Specifications & Properties

• Magnetic Permeability ($\mu$): Guaranteeing a maximum $\mu \le 1.005$ (and often $\le 1.002$). The material is highly stable and does not form magnetic phases (like delta ferrite or strain-induced martensite) even after severe mechanical stress or cold surface working.

• Magnetic Hot Spot Suppression: Fully compliant with API specifications for non-magnetic drill string components, ensuring zero localized magnetic field distortions ("hot spots") that could compromise directional surveying tools.

• Corrosion Profile: It exhibits exceptional resistance to transgranular Stress Corrosion Cracking (SCC) in hot, oxygenated chloride-rich environments and drilling muds up to 150°C.

Mechanical Properties (At Room Temperature)

Because austenitic steels cannot be hardened via heat treatment, Staballoy AG17 achieves its high mechanical properties through a specialized, proprietary combination of thermal and mechanical processing (warm/cold work hardening).

The material is classified by its yield strength thresholds to match standard downhole drilling demands:

Manufacturing & Surface Enhancement

To significantly boost the fatigue lifespan of drill collars and connection threads, finished Staballoy AG17 bars often undergo localized surface treatments:

• Cold Thread Rolling: Compresses the roots of connection threads to combat mechanical fatigue propagation.

• ID Roller Burnishing / Shot Peening: Induces high compressive residual stresses along internal or external walls, significantly raising the material’s threshold against Stress Corrosion Cracking (SCC) and mechanical fatigue failures under alternating stress.

Primary Applications

Staballoy AG17 round bars are heavily utilized within directional drilling, oil & gas exploration, and specialized subsea marine engineering for:

• Non-Magnetic Drill Collars (NMDC): Providing weight on the bit without distorting directional measurement data.

• MWD, LWD, and Wireline Tool Housings: Safeguarding magnetometers, gyroscopes, and electronic logging arrays.

• Non-Magnetic Stabilizers and Drill Pipe Pup Joints

• Specialized Heavy-Duty Marine and Offshore Fasteners: High-load clamping hardware, studs, and heavy-duty shafting where non-magnetic properties and seawater compatibility are simultaneously required.