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UNS N08811 (Alloy 800HT) Stainless Steel

N08811 stainless steel is a superaustenitic (highly alloyed) stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. N08811 is the UNS number for this material. Alloy 800HT is the common industry name.

This material is well established: the Further Reading section below cites a number of published standards, and that list is not necessarily exhaustive.

It has a very low tensile strength among wrought superaustenitic stainless steels. In addition, it has a moderately low base cost and a fairly low ductility.

The graph bars on the material properties cards below compare N08811 stainless steel to: wrought superaustenitic stainless steels (top), all iron alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

200 GPa 29 x 106 psi

Elongation at Break

33 %

Fatigue Strength

150 MPa 22 x 103 psi

Poisson's Ratio

0.28

Shear Modulus

77 GPa 11 x 106 psi

Shear Strength

340 MPa 49 x 103 psi

Tensile Strength: Ultimate (UTS)

510 MPa 74 x 103 psi

Tensile Strength: Yield (Proof)

190 MPa 28 x 103 psi

Thermal Properties

Curie Temperature

-120 °C -180 °F

Latent Heat of Fusion

300 J/g

Maximum Temperature: Corrosion

490 °C 920 °F

Maximum Temperature: Mechanical

1100 °C 2010 °F

Melting Completion (Liquidus)

1390 °C 2530 °F

Melting Onset (Solidus)

1360 °C 2470 °F

Specific Heat Capacity

480 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

12 W/m-K 6.6 BTU/h-ft-°F

Thermal Expansion

14 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

1.7 % IACS

Electrical Conductivity: Equal Weight (Specific)

2.0 % IACS

Otherwise Unclassified Properties

Base Metal Price

30 % relative

Density

8.0 g/cm3 500 lb/ft3

Embodied Carbon

5.3 kg CO2/kg material

Embodied Energy

76 MJ/kg 33 x 103 BTU/lb

Embodied Water

200 L/kg 24 gal/lb

Common Calculations

PREN (Pitting Resistance)

21

Resilience: Ultimate (Unit Rupture Work)

130 MJ/m3

Resilience: Unit (Modulus of Resilience)

94 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

18 points

Strength to Weight: Bending

18 points

Thermal Diffusivity

3.0 mm2/s

Thermal Shock Resistance

13 points

Alloy Composition

Among wrought stainless steels, the composition of N08811 stainless steel is notable for including aluminum (Al) and titanium (Ti). Aluminum is used to improve oxidation resistance. It can also enhance the effects of heat treatment. Titanium is used to broadly improve mechanical properties.

Iron (Fe) 39.5 to 50.6
Nickel (Ni) 30 to 35
Chromium (Cr) 19 to 23
Manganese (Mn) 0 to 1.5
Silicon (Si) 0 to 1.0
Aluminum (Al) 0.15 to 0.6
Titanium (Ti) 0.15 to 0.6
Copper (Cu) 0 to 0.75
Carbon (C) 0.060 to 0.1
Phosphorus (P) 0 to 0.040
Sulfur (S) 0 to 0.015

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM B408: Standard Specification for Nickel-Iron-Chromium Alloy Rod and Bar

ASTM B515: Standard Specification for Welded UNS N08120, UNS N08800, UNS N08810, and UNS N08811 Alloy Tubes

ASTM B409: Standard Specification for Nickel-Iron-Chromium Alloy Plate, Sheet, and Strip

ASTM B407: Standard Specification for Nickel-Iron-Chromium Alloy Seamless Pipe and Tube

ASTM B564: Standard Specification for Nickel Alloy Forgings

Machining of Stainless Steels and Super Alloys: Traditional and Nontraditional Techniques, Helmi A. Youssef, 2016

Nickel Alloys, Ulrich Heubner (editor), 1998

ASTM A240: Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications

Welding Metallurgy of Stainless Steels, Erich Folkhard et al., 2012

ASTM A959: Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Stainless Steels