904L Super Austenitic Stainless Steel N08904, 00Cr20Ni25Mo4.5Cu

Overview of 904L (N08904, 1.4539) Super Austenitic Stainless Steel:

904L (N08904, 1.45390, 0Cr20Ni25Mo4.5Cu) super austenitic stainless steel contains 14.0-18.0% chromium, 24.0-26.0% nickel, 4.5% molybdenum. 904L super austenitic stainless steel is a low-carbon high-nickel, molybdenum austenitic stainless acid-resistant steel. It is a proprietary material introduced by the French company H · S. Has good activation-passivation transformation ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid, and good in neutral chloride-containing media Resistance to pitting corrosion, and has good resistance to crevice corrosion and stress corrosion. It is suitable for sulfuric acid of various concentrations below 70 ° C. It also has good corrosion resistance in acetic acid at any concentration and temperature under normal pressure, and mixed acids of formic acid and acetic acid.

Super austenitic stainless steel 904L (00Cr20Ni25Mo4.5Cu, N08904, 1.4539) is a high-carbon austenitic stainless steel with low carbon content. It has good corrosion resistance in dilute sulfuric acid, and is specially designed for harsh environments. design. It has a high chromium content and sufficient nickel content. The addition of copper makes it highly resistant to acids, especially highly resistant to chloride interstitial corrosion and stress corrosion cracking, and is not prone to corrosion spots and cracks. The corrosion ability is slightly better than other steels, and it has good processability and weldability, and can be used in pressure vessels.

 

Chemical composition of 904L (N08904, 1.4539) super austenitic stainless steel:

%	Ni	Cr	Mo	Cu	Fe	C	Mn	Si	P	S
Min.	23	19	4	1	margin
Max.	28	23	5	2		0.02	2	1	0.045	0.035

 

 

904L (N08904, 1.4539) Super austenitic stainless steel Mechanical properties:

Density	8.24 g/cm3
Melting point	1300-1390 ℃

 

904L (N08904, 1.4539) Minimum value of mechanical properties of super austenitic stainless steel:

tensile strength Rm N/mm2	yield strength RP0.2N/mm2	Elongation A5 %
520	216	35

 

Metallurgical structure of 904L (N08904, 1.4539) super austenitic stainless steel:

904L super austenitic stainless steel is a completely austenitic structure. Compared with austenitic stainless steels with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and α phase.

 

Corrosion resistance of 904L (N08904, 1.4539) super austenitic stainless steel:

Because the 904L carbon content is very low (0.020% max), no carbides will be precipitated under general heat treatment and welding conditions. This eliminates the risk of intergranular corrosion that typically occurs after heat treatment and welding. The high chromium nickel molybdenum content and the addition of copper elements, so 904L can be passivated even in reducing environments, such as sulfuric acid and formic acid. The high nickel content results in a lower corrosion rate in the active state. In the pure sulfuric acid in the concentration range of 0 ~ 98%, the operating temperature of 904L can be as high as 40 degrees Celsius. In pure phosphoric acid with a concentration range of 0 to 85%, its corrosion resistance is very good. In the industrial phosphoric acid produced by the wet process, impurities have a strong influence on the corrosion resistance. Among all kinds of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. Among the highly oxidizing nitric acid, 904L has lower corrosion resistance compared to the highly alloyed steel grade that does not contain molybdenum. In hydrochloric acid, the use of 904L is limited to lower concentrations of 1-2%. In this concentration range. 904L has better corrosion resistance than conventional stainless steel.

904L steel has high resistance to pitting corrosion. Its resistance to crevice corrosion is also good in chloride solutions. The high nickel content of 904L reduces the corrosion rate in pits and crevices. Ordinary austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees Celsius. This sensitization can be reduced by increasing the nickel content of the stainless steel. Due to the high nickel content, 904L has high resistance to stress corrosion cracking in chloride solution, concentrated hydroxide solution and hydrogen sulfide-rich environments.

 

904L (N0804 ,, 14539) Super austenitic stainless steel processing performance:

1. Welding performance: 904L (N08904, 1.4539, 00Cr20Ni25Mo4.5Cu) super austenitic stainless steel can be welded by various welding methods. The most commonly used welding methods are manual arc welding or inert gas shielded welding. The electrode or wire metal is based on the composition of the base metal and has a higher purity. The content of molybdenum is higher than the base metal. Pre-heating is generally not required before welding, but in cold outdoor operations, in order to avoid condensation of water vapor, joint parts or adjacent areas can be uniformly heated. Note that the local temperature should not exceed 100 ° C to avoid carbon accumulation and intergranular corrosion. Welding should use small linear energy, continuous and fast welding rate. Generally no heat treatment is required after welding. If heat treatment is required, it must be heated to 110 0 to 1150 ° C and then quickly cooled.

2. Machining performance: The machining characteristics of 904L (N08904, 1.4539, 00Cr20Ni25Mo4.5Cu) super austenitic stainless steel are similar to other austenitic stainless steels, and there is a tendency of sticking knife and work hardening during processing. It is necessary to use a positive rake angle carbide tool with sulfurized and chlorinated oil as the cutting coolant. The equipment and technology should be based on reducing work hardening. Avoid slow cutting speed and feed during cutting.

 

904L (N0804 ,, 14539) Super austenitic stainless steel supporting welding consumables:

Welding rod: E385-16 / 17, welding wire: ER385.

 

904L (N0804 ,, 14539) Super austenitic stainless steel applications:

Petroleum and petrochemical equipment, such as reactors in petrochemical equipment; sulfuric acid storage and transportation equipment, such as heat exchangers; power plant flue gas desulfurization equipment, the main use parts are: the tower body of the absorption tower, flue, and door panels , Internal parts, spray systems, etc .; scrubbers and fans in organic acid treatment systems; seawater treatment equipment, seawater heat exchangers, paper industry equipment, sulfuric acid, nitric acid equipment, acid production, pharmaceutical industry and other chemical equipment, pressure vessels , Food equipment; centrifuges, reactors, etc. in pharmaceutical factories; soy sauce tanks, cooking wine, salt tanks, equipment and dressing food machinery; equipment and components that are strongly corrosive to dilute sulfuric acid.