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N08904 (904L)

904L — high-alloy austenitic stainless with 4-5% Mo. PRE=34. Resistant to H2SO4, phosphoric acid and chloride pitting. For chemical plant, acid pickling and desalination.

Stainless Steels Super-Austenitic Stainless Steel EN1.4539 / N08904 UNSN08904 ASTMA240 / A276 N08904 BS EN904S13 +5
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Description

904L (UNS N08904 / EN 1.4539) per EN 10088. High-alloy austenitic with 4-5% Mo, low C and Cu addition. PRE=34 — between duplex 2205 (35) and standard 316L (25). Outstanding resistance to H2SO4 at all concentrations, HCl (dilute), wet process phosphoric acid and organic acids. Cu addition improves reducing acid resistance. More cost-effective than duplex for some acid service.

Key Properties — Solution Annealed
Rm (Tensile Strength)
490
MPa
Re / Rp0.2 (Yield)
220
MPa
A₅ (Elongation)
≥ 35.0
%
Hardness
— – 220
HB
E (Young's Modulus)
195
GPa
Density
7.95
g/cm³
Main Designations (9)
Standard BodyDesignationCountry / RegionNote
EN 1.4539 / N08904 EU
UNS N08904 USA (UNS)
ASTM A240 / A276 N08904 USA
BS EN 904S13 UK
JIS SUS890L Japan
GOST 03H20N16AG6 (nearest) Russia
ISO X1NiCrMoCu25-20-5 International
Trade Cronifer 1925 (ThyssenKrupp) / Nicrofer 2520 (ThyssenKrupp) Global
JUS 1.4539 equivalent Yugoslavia Super-austenitic stainless; JUS C.B2.040
Standards (9)
#Standard BodyDesignationCountry / RegionNote
1 EN 1.4539 / N08904 EU —
2 UNS N08904 USA (UNS) —
3 ASTM A240 / A276 N08904 USA —
4 BS EN 904S13 UK —
5 JIS SUS890L Japan —
6 GOST 03H20N16AG6 (nearest) Russia —
7 ISO X1NiCrMoCu25-20-5 International —
8 Trade Cronifer 1925 (ThyssenKrupp) / Nicrofer 2520 (ThyssenKrupp) Global —
9 JUS 1.4539 equivalent Yugoslavia Super-austenitic stainless; JUS C.B2.040
All values in wt.%
C
Carbon
≤ 0.0200
Si
Silicon
≤ 1.0000
Mn
Manganese
≤ 2.0000
Cr
Chromium
19.0000 – 23.0000
Ni
Nickel
23.0000 – 28.0000
Mo
Molybdenum
4.0000 – 5.0000
Cu
Copper
1.0000 – 2.0000
ElementSymbolMin %Max %Typical %
Carbon C — 0.0200 0.0100
Silicon Si — 1.0000 0.5000
Manganese Mn — 2.0000 1.0000
Chromium Cr 19.0000 23.0000 20.5000
Nickel Ni 23.0000 28.0000 25.5000
Molybdenum Mo 4.0000 5.0000 4.5000
Copper Cu 1.0000 2.0000 1.5000
Mechanical Properties
ConditionCode Rm min
MPa		Rm max
MPa		 Re min
MPa		Re max
MPa		 A₅ min
%		 Z
%		 KV
J		 HB minHB max HRC minHRC max E
GPa
Solution Annealed +AT 490 — 220 — 35.0 — — — 220 — — 195.0
Physical Properties
Density
7.950
g/cm³
Melting Point
1300–1350
°C
Young's Modulus
195.0
GPa
Poisson's Ratio
0.290
—
Thermal Conductivity
12.0
W/m·K
Thermal Expansion
15.50
×10⁻⁶ /K
Specific Heat
450
J/kg·K
Electrical Resistivity
0.9500
µΩ·m
Magnetic
No
 
Heat Treatment
Solution Annealing
Temperature:1100°C – 1150°C
Medium:Water quench
Duration:Sufficient
Cooling:Rapid quench
Hardness After:<=HB 220
Low annealing temp — avoids sigma phase formation.
Machinability
Machinability Rating
relative to AISI B1112 = 100%
38.0%
Very Difficult
Turning Speed (HSS)
15
m/min
Turning Speed (Carbide)
78
m/min
Feed Rate (Turning)
0.100
mm/rev
Drilling Speed (HSS)
9
m/min
Milling Speed (Carbide)
80
m/min
CoolantHigh-pressure flood coolant mandatory
Chip FormationLong gummy chips; severe work-hardening
Tool MaterialTiAlN carbide; very sharp; positive rake; reduce speed 20% vs 316L
Surface FinishRa 0.4-1.6 um
More difficult than 316L due to higher alloy content.
Applications
Chemical
H2SO4 service at all concentrations, H3PO4, organic acid processing equipment.
Pickling
Acid pickling tanks for steel strip, wire and tube pickling lines.
Desalination
Seawater desalination evaporator shells and heat exchanger bundles.
Pulp & Paper
Bleach plant wash press frames and filtrate systems.
Technical Notes
✅
904L vs 2205
PRE similar (~34 vs 35). 904L: better in H2SO4 (Cu+Ni effect) and reducing media. 2205: better strength (Rp0.2 450 vs 220 MPa), better pitting in seawater. Choose 904L for acid reducing service; 2205 for chloride oxidising service.
⚠️
Sigma Phase
904L is susceptible to sigma phase at 600-900 C — never use in this temperature range.