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AISI 304H (S30409) Stainless Steel

AISI 304H stainless steel is an austenitic stainless steel formulated for primary forming into wrought products. Cited properties are appropriate for the annealed condition. 304H is the AISI designation for this material. S30409 is the UNS number. Additionally, the British Standard (BS) designation is 304S49.

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 moderately high thermal conductivity and a moderately low tensile strength among wrought austenitic stainless steels.

The graph bars on the material properties cards below compare AISI 304H stainless steel to: wrought austenitic 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

Brinell Hardness

180

Elastic (Young's, Tensile) Modulus

200 GPa 29 x 106 psi

Elongation at Break

40 %

Fatigue Strength

200 MPa 29 x 103 psi

Poisson's Ratio

0.28

Reduction in Area

51 %

Rockwell B Hardness

79

Shear Modulus

77 GPa 11 x 106 psi

Shear Strength

400 MPa 58 x 103 psi

Tensile Strength: Ultimate (UTS)

580 MPa 85 x 103 psi

Tensile Strength: Yield (Proof)

230 MPa 33 x 103 psi

Thermal Properties

Latent Heat of Fusion

290 J/g

Maximum Temperature: Corrosion

420 °C 790 °F

Maximum Temperature: Mechanical

960 °C 1760 °F

Melting Completion (Liquidus)

1430 °C 2600 °F

Melting Onset (Solidus)

1380 °C 2520 °F

Specific Heat Capacity

480 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

17 W/m-K 9.8 BTU/h-ft-°F

Thermal Expansion

16 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

2.4 % IACS

Electrical Conductivity: Equal Weight (Specific)

2.8 % IACS

Otherwise Unclassified Properties

Base Metal Price

15 % relative

Density

7.8 g/cm3 490 lb/ft3

Embodied Carbon

3.0 kg CO2/kg material

Embodied Energy

43 MJ/kg 18 x 103 BTU/lb

Embodied Water

150 L/kg 17 gal/lb

Common Calculations

PREN (Pitting Resistance)

19

Resilience: Ultimate (Unit Rupture Work)

190 MJ/m3

Resilience: Unit (Modulus of Resilience)

130 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

25 points

Strength to Weight: Axial

21 points

Strength to Weight: Bending

20 points

Thermal Diffusivity

4.5 mm2/s

Thermal Shock Resistance

13 points

Alloy Composition

Among wrought stainless steels, the composition of AISI 304H stainless steel is notable for containing comparatively high amounts of chromium (Cr) and nickel (Ni). Chromium is the defining alloying element of stainless steel. Higher chromium content imparts additional corrosion resistance. Nickel is primarily used to achieve a specific microstructure. In addition, it has a beneficial effect on mechanical properties and certain types of corrosion.

Iron (Fe) 66.6 to 74
Chromium (Cr) 18 to 20
Nickel (Ni) 8.0 to 10.5
Manganese (Mn) 0 to 2.0
Silicon (Si) 0 to 0.75
Carbon (C) 0.040 to 0.1
Phosphorus (P) 0 to 0.045
Sulfur (S) 0 to 0.030

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

Followup Questions

Similar Alloys

Further Reading

EN 10028-7: Flat products made of steels for pressure purposes - Stainless steels

ASTM A479: Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels

ASTM A182: Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service

ASTM A276: Standard Specification for Stainless Steel Bars and Shapes

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

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

Corrosion of Austenitic Stainless Steels: Mechanism, Mitigation and Monitoring, H. S. Khatak and B. Raj (editors), 2002

Pressure Vessels: External Pressure Technology, 2nd ed., Carl T. F. Ross, 2011

Austenitic Stainless Steels: Microstructure and Mechanical Properties, P. Marshall, 1984

Properties and Selection: Irons, Steels and High Performance Alloys, ASM Handbook vol. 1, ASM International, 1993