What Is 904l Grade Material?

Features of stainless steel 904L

904L is a highly alloyed austenitic stainless steel with very low carbon content. The steel is designed for harsh corrosion conditions. The alloy was originally developed to resist corrosion in dilute sulfuric acid. This feature has been proven to be very successful in practical applications for many years. 904L is now standardized in many countries and has been approved for use in pressure vessels.

Grade 904L stainless steel is a non-stabilized austenitic stainless steel with low carbon content. This high alloy stainless steel is added with copper to improve its resistance to strong reducing acids, such as sulphuric acid. The steel is also resistant to stress corrosion cracking and crevice corrosion. Grade 904L is non-magnetic, and offers excellent formability, toughness and weldability. Grade 904L contains high amounts of expensive ingredients, such as molybdenum and nickel. Today, most of the applications that employ grade 904L are replaced by low-cost duplex stainless steel 2205.

904L, like other commonly used Cr Ni austenitic steels, has good resistance to point and gap corrosion, high resistance to stress corrosion fracture, good resistance to intergranular corrosion, good processability and weldability. The maximum heating temperature during hot forging is up to 1180 degrees Celsius and the minimum stopping temperature is not less than 900 degrees Celsius. This steel can be thermoformed at 1000 – 1150 degrees Celsius. The steel is heat treated at 1100 – 1150 degrees Celsius and heated and then quickly cooled.

904L may considered as a high performance austenitic stainless steel when compared with the general purpose austenitics such as 304 and 316. It has the characteristic high ductility and formability and good weldability of the austenitic grades, but its use is primarily a consequence of its corrosion resistance rather than its mechanical properties. Applications for the alloy range from the chemical and mineral processing industries to pollution control and water treatment. For many years it has been a useful upgrade to 316L but in more recent times the cost effectiveness of duplex grades has limited its use.

Chemical composition analysis of stainless steel 904L

UNS N08904 is an austenitic grade alloy containing roughly 23% chromium, 19% nickel, 4.5% molybdenum, and a small amount of carbon (less than 0.2%). It has low carbon content, which makes it highly resistant to intergranular corrosion following welding or stress-relieving operations.

Mechanical properties of stainless steel 904L

Resistance to Corrosion:

One of the most significant advantages of using 904L stainless steel pipes in marine environments is their high corrosion resistance. 904L stainless steel pipe is more resistant to pitting and corrosion than other types of stainless steel pipe. 904L stainless steel is a low carbon, high alloy austenitic stainless steel resistant to the crevice, stress corrosion cracking, and pitting. The high levels of molybdenum and nickel in the steel increases its resistance to chloride attack, making it ideal for use in seawater applications. Also, the addition of copper makes the steel even more resilient to harsh marine environments.

A primary feature of 904L is its very good corrosion resistance in dilute sulphuric acid across the full range of concentrations up to 35° C. It also has useful resistance to a number of other inorganic acids, but its performance may be limited when halide ions are present. Whilst the nickel content of conventional stainless steels is such that they are very susceptible to chloride stress corrosion cracking, the higher level of this element in 904L imparts good resistance to this form of corrosion. The nitrogen, molybdenum and chromium contents in stainless steels have a direct bearing on their resistance to pitting and crevice corrosion and in the case of 904L this parameter is good. However, the 6% molybdenum austenitic grades or super- duplex grades do display superior resistance to these forms of localised corrosion.

Weldable:

Another benefit of a 904L stainless steel pipe is that it is more weldable than other types of stainless steel. This is due to the alloy’s lower carbon content, making it less susceptible to carbide precipitation during welding. This makes 904L stainless steel pipe an ideal choice for use in welding applications. Can be welded with most standard workplaces. The austenite plate material has uniform austenite structure and uniform distribution of alloying elements, which may cause the redistribution of certain elements such as molybdenum, chromium and nickel after welding. And the separation of these elements retained in the welded casting tissue will influence the corrosion resistance in some environments. However, element separation is less evident in 904L, and this material is usually welded with filler metal of the same composition as the base metal, or even without filler metal.

High Strength and Durability:

The high strength and toughness of 904L stainless steel make it an ideal material for use in marine pipelines. This type of steel is known for its excellent fatigue strength, high tensile strength, and low thermal expansion coefficient, making it resistant to deformation under high loads. It can withstand high-pressure conditions, high temperatures, and the harsh marine environment without losing its mechanical properties.

Recyclability:

904L stainless steel is a sustainable material that is 100% recyclable and made of environmentally friendly materials. Its recyclability benefits the environment by reducing waste and minimizing damage to natural resources. Therefore, it is an eco-friendly alternative to using other less sustainable metals in marine environments.

Cost-Effective:

One final advantage of a 904L stainless steel pipe is its lower cost per pound than other types of stainless steel. This makes it an economical choice for use in marine environments where budget is a concern. Despite its high-grade quality, 904L stainless steel is cost-effective in the long run. The high corrosion resistance of 904L stainless steel ensures pipelines last longer, resulting in lower maintenance costs over time. Additionally, its ability to withstand harsh marine environments and high temperatures makes it a reliable and cost-effective choice for marine infrastructure.

Compatibility with Existing Systems:

Finally, 904L stainless steel pipes are easy to integrate with existing systems. They are compatible with most existing stainless steel systems, making them an easy and cost-effective replacement. The pipes’flexibility, durability, and resistance to corrosion make them a reliable and versatile material for marine pipelines.

Application of stainless steel 904L

Due to its superior corrosion resistance properties, Stainless steel 904L is often used in applications such as oil refineries, chemical processing plants, pulp & paper mills and desalination plants where there may be exposure to highly corrosive environments. It is also commonly used in marine engineering applications due to its excellent resistance to salt water corrosion and its non-magnetic properties, making it suitable for underwater applications such as sonar domes on submarines. Additionally, this alloy is often used in medical instruments due to its biocompatibility characteristics, making it safe for contact with human tissue or fluids without causing any adverse reactions.

1. Oil and gas sector machinery, including petrochemical reactors;

2. Acid storage and transport devices, specifically for sulfuric acid, like heat exchangers;

3. Equipment for flue gas desulfurization in power generation, particularly parts like the tower structure of the absorption tower, ductwork, access panels, internals, and spray systems;

4. Components like washers and blowers in systems for organic acid processing;

5. Equipment for processing seawater, including heat exchangers for seawater;

6. Machinery used in the paper production industry;

7. Biopharmaceutical production facilities, including separators, reactors, and more;

8. Equipment for handling sulfuric and nitric acid, used in acid manufacturing processes;

9. Various chemical processing equipment and pressure containers;

10. Culinary processing equipment, including containers for soy sauce, cooking wine, salt dispensers, and condiment containers;

11. Wristwatches