904L Duplex stainless steel 1.4539 (UNS N08904）

What is stainless steel 904L?

904L is an austenitic stainless steel. Though notably softer than 316L, its molybdenum addition gives it superior resistance to localized attack (pitting and crevice corrosion) by chlorides and greater resistance reducing acids and in particular its copper addition gives it useful corrosion resistance to all concentrations of sulphuric acid. Its high alloying content also gives it greater resistance to chloride stress corrosion cracking, but it is still susceptible. Its low carbon content makes it resistant to sensitization by welding and which prevents intergranular corrosion.

904L stainless steel 1.44539 Products Form

• Pipes
• Tubing
• Pipe Fittings
• Flanges
• Valves
• Fasteners
• Plates
• Forgings

Applications for 904L stainless steel

1.4539 904L stainless steel is widely used in the chemical, pharmaceutical, oil and gas industries. Typical applications include tanks, valves, heat exchangers, flanges and manifolds. The addition of copper to the composition of 904L stainless steel aids its suitability for components such as tanks and other products used in handling sulphuric and phosphoric acid.

Equivalents of grade 904L

EU EN	USA –	France AFNOR	England BS	Sweden SS	Poland PN
X1NiCrMoCu25-20-5	904LN08904	Z2NCDU25-20	904S13	2562	00H22N24M4TC

Composition ranges for 904L grade of stainless steel

Grade		C	Mn	Si	P	S	Cr	Mo	Ni	Cu
904L	min.max.	-0.02	-2	-1	-0.045	-0.035	1923	45	2328	12

Mechanical Properties

Grade	Tensile Strength (MPa) min	Yield Strength 0.2% Proof (MPa) min	Elongation (% in 50mm) min	Hardness
				Rockwell B (HR B)	Brinell (HB)
904L	490	220	36	70-90 typical	150

Physical Properties

Grade	Density (kg/m3)	Elastic Modulus (GPa)	Mean Co-eff of Thermal Expansion (µm/m/°C)			Thermal Conductivity (W/m.K)		Specific Heat 0-100°C (J/kg.K)	Elec Resistivity (nΩ.m)
			0-100°C	0-315°C	0-538°C	At 20°C	At 500°C
904L	7900	190	15	–	–	11.5	–	500	952

Corrosion Resistance

Stainless steel type 904L is primarily fabricated to offer resistance to the sulfuric acid and it also possesses superior resistance to the various conditions. It has outstanding resistance to the hot sea water and chloride conditions. The significant content of nickel offers outstanding resistance to stress corrosion cracking as compare to the other stainless steel alloys. The copper content enhances the resistance to sulfuric acid and other reducing acids especially in the rigorous conditions.

In the various atmospheres, stainless steel 904L grade offers moderate corrosion resistance between the standard austenitic 316L alloy and highly alloyed 6% molybdenum and equivalent to super austenitic alloy types. In the presence of rigorous nitric acid, the lower resistance as compare to molybdenum-free alloys like 304L and 310L are used. To get the highest stress corrosion cracking resistance in the crucial conditions, the steel is recommended to solution treating subsequent to cold processing. 

Heat Resistance

Grade 904L stainless steels offer good oxidation resistance. However, the structural stability of this grade collapses at high temperatures, particularly above 400°C.

Heat Treatment

Solution annealing at 1050°C – 1150°C followed by rapid cooling in air or water.

Hot working

Hot work should proceed after uniform heating to 2000-2200 F. Doe not work the material at less than 1800 F. Full annealing should follow any hot work to reattain maximum ductility and corrosion resistance.

Cold working

Although higher forces are required, 904L will respond in a similar fashion to other austenitic stainless steels like 304, 316 or 317. Most common operations can be successfully performed.

Machinability

Slow speeds and positive feeds will minimize this alloy’s tendency to work harden and glaze. Use chip breakers where possible to overcome problems with long draggy chips.

Welding

Welding of grade 904L stainless steels can be performed using all conventional methods. This grade does not require pre-heat and post-weld heat treatments. Grade 904L can be subjected to hot cracking in constrained weldment. Grade 904L electrodes and rods are used for welding grade 904L steels according to AS 1554.6.

Fabrication

Stainless Steel 904L is high-quality steel with low sulphur content. They can be machined using any standard method. This grades can be quickly bent to a small radius under cold conditions. Even though subsequent annealing is not required in most cases, it should be performed when manufacturing under severe stress corrosion cracking conditions.