Super Stainless Steel — Fully Austenitic 904L

2025-11-11

Chemical Composition (%)

Element	C	Si	Mn	P	S	Cr	Ni	Mo	N	Cu
ASTM	0.020	1.00	2.00	0.045	0.035	19.0-23.0	23.0-28.0	4.0-5.0	0.10	1.0-2.0
Typical	0.015	0.45	0.9	0.038	0.005	20	25	4.3	-	1.5

Physical Properties of 904L
• Density: 8.00 g/cm³
• Melting Point: 1300-1390 ℃
• Tensile Strength: σb ≥ 520 MPa
• Elongation: δ ≥ 35%

Mechanical Properties

Item	Rp0.2 (MPa)	Rp1.0 (MPa)	Rm (MPa)	A5 (%)	HRB
Standard	≤220	≤250	≤490	≥35	≤90
Typical	290	-	580	47	85

Physical Properties

Property	Unit	Value
Density	g/cm³	8.0
Elastic Modulus	GPa	195
Linear Expansion Coefficient	10⁻⁶/℃	15.8
Thermal Conductivity	W/m·℃	12
Heat Capacity	J/kg·℃	450
Electrical Resistance	μΩ·m	1.0

Corrosion Resistance

1) Corrosion Rate in HNO₃ 20% + HF 4% at 25℃

Grade	Corrosion Rate (mm/a)
316	>5
904L	0.51
254SMO	0.31

2) Performance in Fatty Acid at 260℃

Grade	Corrosion Rate (mm/a)
316	0.88
317LMN	0.29
904L	0.06
254SMO	0.01

Fabrication Characteristics

welding Performance
This material welds like standard austenitic stainless steels. Common methods include manual arc and gas-shielded welding. Use matching but purer filler metals. The molybdenum content should exceed the base metal. Preheat is generally unnecessary. For cold conditions, warm the joint area uniformly. Keep local temperature below 100°C. This prevents carbon issues. Apply low heat input with steady, rapid welding. Post-weld heat treatment is typically unnecessary. When required, heat to 1100-1150°C then cool rapidly.

Machining Performance
Machining behavior resembles other austenitic grades. It tends to gall and work-harden. Apply positive rake carbide tools. Use sulfur-chlorinated cutting fluids. Choose methods that minimize hardening. Maintain adequate speeds and feeds.

Typical Applications

Petrochemicals: Reactors, heat exchangers, piping systems. Handles aggressive media like sulfuric and phosphoric acid.
Flue Gas Systems: Ducting, absorber towers, spray headers in desulfurization units. Withstands hot corrosive gases.
Marine Equipment: Seawater handling systems, vessel components. Provides superior crevice and stress corrosion resistance.