Stainless Steel 904L

Stainless Steel from Special Piping Materials

STAINLESS STEEL 904L

Stainless steel 904L is a super-austenitic stainless steel which is known for its corrosion and pitting resistance and can be used in a wide range of process environments.

While stainless steel 904L was originally designed withstand environments that had sulfuric acid, it has become increasingly used in other scenarios due to its good corrosion resistance in a wide range of process environments.

Its ability to withstand corrosion is due to its combination of high chromium and nickel, along with molybdenum and copper.

The blend of 25% nickel and 4.5% molybdenum allows stainless steel 904L to provide good chloride stress corrosion cracking resistance, pitting and general corrosion resistance. It is also easily welded and processed.

Interestingly, the quality and durability of stainless steel 904L means that it is the metal commonly used to produce Rolex watches.

To be considered a stainless steel 904L, the metal must have a unique chemical composition:

• Fe balance
• Ni 23-28%
• Cr 19-23%
• Mo 4-5%
• Mn 2%
• Cu S 1-2.0%
• Si 0.7%
• S 0.3%
• N 0.1%
• P 0.03%

Stainless steel 904L is often compared to stainless steel 316L, and there are some major differences to be considered. Each metal’s unique properties mean they have to be carefully chosen for different applications. Let’s take durability and hardness as examples:

• Durability: Both stainless steel 904L and 316L contain chromium which reacts with oxygen to form a thin, protective layer of chromium oxide on its surface. 904L has a higher amount of chromium and thus can withstand corrosion for longer.
• Hardness: According to the Rockwell Scale (which measures the indentation hardness of a material), both stainless steel 904L and 316L have a value below 95 which means both alloys are able to withstand most forces.

Stainless Steel 904L Properties

Stainless steel 904L is mainly known for its resistance to corrosion. Its high content of alloying elements means it can withstand environments containing dilute sulfuric acid and is also effective at resisting corrosion in temperatures up to 95°F (35°C).  It can also offer good resistance to a number of other inorganic acids, such as phosphoric acid and most organic acids. It also has very good resistance to chloride stress corrosion cracking (SSC), especially in comparison to stainless steel 304L and 316L which can be susceptible to chloride stress corrosion cracking.

Other properties of Stainless steel 904L are:

• Good strength and toughness at cryogenic temperatures
• Ease of cleaning
• Good formability and weldability
• Resistance to oxidation
• Prevention of product contamination
• Ease of fabrication
• High strength to relatively low weight
• Readily availability of a wide range of product forms
• Non-magnetic

Stainless Steel 904L applications

904L is widely used in the chemical, pharmaceutical, water treatment, desalination and oil and gas industries. It has a wide range of applications such as:

• Tanks
• Valves
• Heat exchangers
• Flanges
• Manifolds
• Cooling equipment for seawater
• Condenser tubes
• Control and instrumentation
• Pharmaceutical production
• Wiring in electrostatic precipitators
• Gas washing
• Scrubbers for coal-fired power plants
• Metallurgical processing such as pickling equipment using sulfuric acid
• Offshore process equipment
• Pharmaceutical process equipment
• Pulp and Paper processing equipment

Stainless Steel 904L products available from Special Piping Materials

• Sheet
• Plate
• Bar
• Pipe, welded and seamless
• Fittings (i.e., flanges, slip-ons, blinds, weld-necks, lap-joints, long welding necks, socket welds, elbows, tees, stub-ends, returns, caps, crosses, reducers, and pipe nipples)

To discuss the price of stainless steel 904L products, and to find out more about our competitive pricing and specialist services, please contact the Special Piping Materials sales team at one of our offices around the globe: https://specialpipingmaterials.com/contact/

Stainless Steel 904L ASTM specifications

The Stainless Steel 904L ASTM specifications are as follows:

• Pipe seamless: A312
• Pipe welded: A358
• Sheet/Plate: A240
• Bar: A276
• Flanges & forgings: A182
• Buttweld fittings: A403