Views: 33 Author: Rachel Publish Time: 2024-07-24 Origin: Site
Stainless steel 904L, commonly called UNS N08904, is a low carbon high alloy austenitic stainless steel. Adding copper to this grade makes it more resistant to corrosion than regular chrome nickel stainless steels. This is especially true for sulphuric, phosphoric, and acetic acids.
However, there is limited use with hydrochloric acids. It also resists pitting in chloride solutions. It has a strong resistance to crevice and stress corrosion cracking. Alloy 904L performs better than other austenitic stainless steels due to the higher alloying of nickel and molybdenum.
The grade of 904L stainless steel is non-magnetic in all conditions and has excellent formability and weldability. The austenitic structure also gives this grade excellent toughness, even down to cryogenic temperatures.
This high alloy stainless steel has copper added to help it resist strong acids, like sulfuric acid. The steel is also resistant to stress corrosion cracking and crevice corrosion. And offers excellent formability, toughness and weldability.
The high chromium content promotes and maintains a passive film which protects the material in many corrosive environments. 904L is better at resisting the formation of ferrite and sigma phases during cooling and welding. This is true compared to other stainless steels with molybdenum, like 316L and 317L.
There is no risk of intercrystalline corrosion on cooling or welding due to the low carbon content. Its maximum service temperature is at 450°C.
JN Alloy is a distributor and manufacturer of stainless steel, duplex steel, and nickel-based alloy materials. The company benefits from strong access to raw materials and has many domestic and foreign steel mill resources. To find more information about stainless steel 904L, we advise you to visit JN Alloy.
Low carbon content: Prevents carbide precipitation and eliminates intergranular corrosion.
The most significant feature of 904L stainless steel is its low carbon design, typically with a carbon content of ≤0.02%. This effectively prevents carbide precipitation during welding and heat treatment. Carbide precipitation not only destroys the material's microstructure but also forms chromium-depleted zones at grain boundaries, triggering intergranular corrosion.
Intergranular corrosion is a hidden and very harmful type of corrosion. It can lead to sudden material failure without any visible damage. This poses a serious risk to engineering safety.
By strictly controlling its carbon content, 904L stainless steel successfully avoids carbide precipitation, eliminating the potential for intergranular corrosion.
High nickel content: Stabilizes the austenitic structure and enhances oxidation resistance.
The high nickel content in 904L stainless steel is its second most significant characteristic. Nickel is an important part of austenitic stainless steel. It helps keep the austenitic structure stable and makes the material stronger and tougher.
Furthermore, high nickel content enhances 904L stainless steel's oxidation resistance. At high temperatures, nickel creates a thick oxide layer. This layer stops oxygen from directly touching the material. As a result, it slows down the oxidation rate.
The stable austenitic structure of 904L stainless steel makes it less likely to bend or break under high stress. This improves its resistance to fatigue.
High chromium and molybdenum content: Improves acid resistance and localized corrosion resistance.
The high chromium content in 904L stainless steel is a key factor in its corrosion resistance. Chromium creates a thick oxide layer on the alloy surface.
This layer is very stable and resists corrosion. It protects against many types of acids and bases. In strong acid environments, 904L stainless steel has a high chromium content. This makes its corrosion resistance much better than regular stainless steel.
In addition to its high chromium content, 904L stainless steel also contains a high molybdenum content. Molybdenum is an element that effectively enhances the material's localized corrosion resistance in halide-containing and acidic media.
In harsh environments like seawater, pickling, and strong acid solutions, molybdenum creates a special protective film. This film stops direct contact between the corrosive substances and the base material. This characteristic makes 904L stainless steel widely applicable in fields such as marine engineering and chemical equipment.
Appropriate amount of copper: provides additional protection and enhances overall corrosion resistance.
In addition to the main alloying elements mentioned above, 904L stainless steel also contains an appropriate amount of copper. As an excellent corrosion-resistant element, copper can provide protection in reducing media.
When 904L stainless steel is in reducing environments, copper reacts with some components. This creates a protective film. This film further isolates the corrosive medium from the base material, thereby improving the material's corrosion resistance.
Adding the right amount of copper improves the corrosion resistance of 904L stainless steel. It also helps the material resist corrosion in many different environments. This feature makes 904L stainless steel very valuable in industries like chemical, petroleum, and pharmaceuticals. These industries deal with many corrosive materials.
904L Stainless Steel Applications and Future
In the chemical industry, 904L stainless steel is used. It is made into containers, pipes, valves, and other equipment. This steel is resistant to corrosion.
In the petroleum industry, it is used to make important parts. These parts include oil well casings, Christmas trees, and submarine pipelines.
In marine engineering, 904L stainless steel is a top choice. It is known for its great resistance to seawater corrosion. This makes it ideal for ship hulls, desalination equipment, and submarine cable sheaths.
In the future, the demand for high-performance stainless steel materials will continue to grow. With its special makeup and great resistance to corrosion, 904L stainless steel is likely to be used in many areas. At the same time, the performance of 904L stainless steel will continue to improve.
The carbon content of 904L is very low, at a maximum of 0.020%. This means there is no carbide precipitation during normal heat treatment and welding. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and welding.
Because it has a lot of chromium, nickel, molybdenum, and copper, 904L can be passivated. This is true even in reducing environments like sulfuric acid and formic acid. The high nickel content gives it a lower corrosion rate even in the active state.
904L can be used at temperatures up to 40 degrees Celsius. It works well in pure sulfuric acid with concentrations from 0 to 98%.
The corrosion resistance is excellent in pure phosphoric acid in the concentration range of 0 to 85%. In the industrial phosphoric acid produced by the wet process, impurities have a strong influence on corrosion resistance. 904L has better corrosion resistance than ordinary stainless steel of all phosphoric acid types.
In strong nitric acid, Alloy 904L does not resist corrosion as well as highly alloyed steels without molybdenum. In hydrochloric acid, users limit 904L to lower concentrations of 1-2%.
In this concentration range, 904L has better corrosion resistance than regular stainless steel. It also has a high resistance to point corrosion. The high nickel content of 904L reduces the rate of corrosion in pits and crevices.
Ordinary austenitic stainless steels can be sensitive to stress corrosion in chloride-rich environments. This is especially true at temperatures above 60 degrees Celsius. However, increasing the nickel content in the stainless steel can reduce this sensitivity.
Because it has a lot of nickel, 904L resists stress corrosion in chloride solutions. It also works well in strong hydroxide solutions and environments with hydrogen sulfide.
904L is easy to be elongated and shaped. Compared to 304 or 304L, more molybdenum and nitrogen means it needs stronger processing equipment.
The temperature for hot forming is recommended to be between 1562 and 2102°F (850-1150°C). Normally, next steps of hot forming are annealing and hardening. For 904L, if it stops forming when the temperature exceeds 2012°F (1100°C), it must be quenched right away. This allows the material to be used without further heat treatment.
More importantly, the entire workpiece can be quenched when temperature is higher than 2012°F (1100°C). When local heating or cooling is below 2012°F (1100°C), and cooling is too slow, hot forming will follow. This will happen after the processes of annealing and quenching. 904L shall be annealed between 1940 and 2084°F (1060-1140°C).
Stainless steel 904L can be welded with most standard workplaces. The austenite plate material has a uniform austenite structure. It also has a uniform distribution of alloying elements.
This can lead to the redistribution of some elements like molybdenum, chromium, and nickel after welding. The separation of these elements in the welded casting will affect corrosion resistance in some environments. Element separation is not as clear in 904L.
This material is often welded using filler metal that matches the base metal. Sometimes, it is welded without any filler metal at all.
Excellent Corrosion Resistance
A major advantage of 904L stainless steel is its corrosion resistance. Its high levels of molybdenum and chromium make it very resistant to pitting, crevice, and general corrosion. It works well in harsh environments like chemical processing and offshore settings.
Excellent Mechanical Properties
904L stainless steel not only offers excellent ductility but also possesses exceptionally high tensile strength. If you work in a high-stress job or need flexibility, this stainless steel will keep your parts strong during tough use.
Excellent Formability and Weldability
Another major advantage of 904L stainless steel is its formability and weldability. You will see that 904L can be bent into any shape. It can also be welded with other 904L materials.
This means it keeps its properties. Because of this, it is good for almost any use.
Resistant to Stress Corrosion Cracking
One benefit of 904L stainless steel is that it does not easily crack under stress. This is especially true in chloride environments. This is ideal for situations where material failure can lead to serious issues. This includes industries like oil, gas, and chemicals.
High Wear Resistance
If your environment requires toughness and you don't mind the higher cost, 904L stainless steel offers superior wear resistance. This material works well in situations where parts face wear and tear. It reduces the need for frequent repairs and replacements.
High-Temperature Stability
Finally, 904L alloy performs well at high temperatures. Its strength and resistance to corrosion stay the same, even when it gets hot. Whether you're working in power generation or chemical processing, this alloy is an excellent choice for high-temperature environments.
Stainless Steel 904L Pipe
904L pipes has exceptional corrosion resistance in aggressive environments, particularly against sulfuric acid, phosphoric acid, and chloride-induced stress corrosion cracking. These pipes have at least 23% chromium, 4% molybdenum, and copper. They perform better than 316L in acidic or polluted environments.
904L has seamless and welded forms, they serve critical roles in chemical processing, pharmaceutical, and offshore oil/gas systems. Standard sizes range from ½" to 24" NPS with schedules 10S to 80S.
Stainless Steel 904L Flanges
Designed for strong sealing in harsh environments, 904L flanges resist crevice corrosion well. This is due to their low carbon content and added molybdenum. These flanges withstand temperatures up to 400°F in sulfuric acid concentrators, seawater-cooled heat exchangers, and desulfurization scrubbers. Common types include weld neck, slip-on, and blind flanges, typically furnished with Ra ≤ 0.8 μm surface finish.
Stainless Steel 904L Fasteners
904L bolts, nuts, and studs provide unmatched reliability in acidic and saline environments where standard stainless fasteners fail. Their nickel-chromium-molybdenum-copper matrix resists chloride pitting at concentrations up to 100,000 ppm. Supplied in strength classes 70 or 80, these fasteners require anti-galling lubricants during torquing to prevent cold welding.
Stainless Steel 904L Pipe Fittings
904L elbows, tees, reducers, and caps enable leak-free routing of corrosive fluids. These fittings are cold-formed and solution-annealed at 1922°F.
They have uniform metallurgy and at least 45% elongation. This helps them resist vibration and fatigue. Their copper content helps resist reducing acids, like sulfuric acid, at levels below 20%. This makes them important in pickling lines, copper leaching plants, and coal gasification systems.
| Product | Size Range | Price per Unit (USD) |
|---|---|---|
| 904L Seamless Pipe | ½" SCH 40 – 24" SCH 80 | 25–180 /kg |
| 904L Welded Pipe | 6" SCH 10S – 36" SCH 40 | 18–120 /kg |
| 904L Flanges | Class 150 – 2500, DN15–600 | 50–1,200 /pc |
| 904L Fasteners | M6 – M48, Grade A4-80 | 1.50–85 /pc |
| 904L Butt-Weld Fittings | ½" – 24", Sch 5S–160 | 15–500 /pc |
Composition and Alloy
904L is a super-austenitic alloy containing high nickel (23-28%), molybdenum (4-5%), and copper (1-2%), with chromium at 19-23%.
316L is a standard austenitic grade with lower nickel (10-14%), molybdenum (2-3%), no copper, and chromium at 16-18%.
Corrosion Resistance
904L excels in aggressive environments, resisting pitting/crevice corrosion in high-chloride media, sulfuric acid, and phosphoric acid. Its copper content protects against reducing acids.
316L offers good general corrosion resistance but fails in chloride-rich settings and concentrated acids.
Mechanical Strength
904L has higher tensile strength and significantly better impact toughness, especially at subzero temperatures.
316L provides adequate strength for most structural applications but lacks 904L’s resilience in cryogenic or high-stress corrosive environments.
Cost and Availability
904L costs 3-4× more than 316L due to its nickel/molybdenum content and specialized manufacturing. Lead times are longer.
316L is widely available as a commodity stainless steel, with rapid delivery and extensive stock globally.
Fabrication and Weldability
904L requires specialized welding procedures and strict heat control to prevent sigma phase precipitation. Machining is challenging due to work hardening.
316L welds easily with common ER316L filler and machines well with standard tools.
Applications
904L: Offshore oil/gas piping, seawater heat exchangers, sulfuric acid reactors, flue gas desulfurization systems, and pharmaceutical CIP systems.
316L: Food/beverage equipment, architectural cladding, chemical tanks, medical devices, and general-purpose process piping.
