UNS N08904, commonly known as 904L with its DIN equivalent W.Nr. 1.4539, is a low carbon super austenitic stainless steel. It has superior corrosion resistance to that of conventional Cr-Ni stainless steels such as SS316L and SS317L resulting from the deliberate addition of copper content. Although the 904L stainless steel has limited use with hydrochloric acids, it has high resistance to pitting corrosion in chloride solutions, high resistance to both crevice and stress-corrosion cracking. The grade is non-magnetic and has excellent formability and weldability, as well as good toughness in cryogenic temperatures. 904L stainless steels have greater resistance to precipitation of ferrite and sigma phases on cooling and welding. The low carbon content reduces the risk of intercrystalline corrosion on cooling or welding processes. This super austenitic stainless steel is widely used in chemical processing, oil & gas, and pharmaceutical industries.

1. Chemical Composition of 904L

The Chemical Composition of 904L, %
C	≤0.020
Mn	≤2.00
P	≤0.045
S	≤0.035
Si	≤1.00
Cr	19.0-23.0
Ni	23.0-28.0
Mo	4.0-5.0
N	≤0.10
Cu	1.0-2.0

2. Mechanical Properties of 904L

Tensile Strength, min.		Yield Strength, min.		Elongation, min.
ksi	Mpa	ksi	Mpa	%
71	490	31	220	35

3. Physical Properties of 904L

Density	Specific Heat	Thermal Conductivity	Thermal Expansion	Modulus Elasticity	Electrical Resistivity
g/cm3	J/(kg*K)	W/(m*k)	mm/m/°C	Gpa	µohm/cm
7.95	450	11.5	15.8	190	9.52

4. Product Forms and Relative Standards

Product Form	Standard
Plates, Sheets & Strips	ASATM A240, A480
Bars, Rods, Billets	ASTM A276, A479
Forging(flanges, fittings, valve parts)	ASTM A182, A484
Seamless and welded pipes/ Tubes	ASTM A312, A269
Butt Welding pipe fittings	ASTM A403, ASME B16.9

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