UNS N08031 Nickel Alloy Steel Seamles Tube

UNS N08031 Seamles Nickel Alloy Steel Pipe Summary

UNS N08031, also known as Alloy 31 or W.Nr. 1.4562, is a high-performance austenitic nickel-iron-chromium-molybdenum alloy with added nitrogen. It bridges the gap between super-austenitic stainless steels and traditional nickel-based alloys, offering exceptional resistance to corrosion, erosion, pitting, and stress-corrosion cracking. This makes it ideal for demanding environments involving acids (e.g., phosphoric, sulfuric, hydrochloric), chlorides, and seawater. Seamless pipes in this grade are produced without welds, ensuring uniform strength and integrity under high pressure and temperature. They are commonly used in chemical processing, flue gas desulfurization (FGD) systems, seawater heat exchangers, pulp and paper production, oil refining, mining, and environmental equipment.

Chemical

Element	Composition (%)
Carbon (C)	≤ 0.015
Silicon (Si)	≤ 0.3
Manganese (Mn)	≤ 2.0
Phosphorus (P)	≤ 0.020
Sulfur (S)	≤ 0.010
Chromium (Cr)	26.0–30.0
Molybdenum (Mo)	6.0–7.0
Nickel (Ni)	30.0–32.0
Nitrogen (N)	0.15–0.25
Iron (Fe)	Balance

Mechanical Properties

Tensile Strength (min)	650 MPa (94 ksi)
Yield Strength (0.2% offset, min)	300 MPa (43.5 ksi)
Elongation (min, 2”-gauge length)	40%
Hardness (Brinell, max)	217 HB
Density	8.1 g/cm³

Standards

ASTM B622	Seamless nickel and nickel-cobalt alloy pipe and tube (primary spec for seamless forms). Covers sizes up to 3.5" (88.9 mm) OD.
ASME SB622	Boiler and pressure vessel code equivalent of ASTM B622.
DIN/EN 1.4562	European standard for high-alloy steels.
ASTM B619	Sometimes referenced for welded variants, but seamless is B622.

Applications

Chemical Industry: Phosphoric acid production, sulfuric acid handling, and chloride-contaminated systems.
Environmental: FGD scrubbers and waste acid treatment.
Marine/Oil & Gas: Seawater exchangers, offshore platforms, and refining equipment.
Pulp & Paper: Processing lines exposed to corrosive liquors.
Other: Ore processing, evaporation/crystallization units, and heat exchangers up to 427°C (800°F).