LEADS: What is Grade 904L Stainless Steel

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904L Features

904L super austenitic stainless steel finds its origin from a French company named H·S. it’s an acid resistant stainless steel containing low carbon, and high-nickel & molybdenum. Type 904L features good activation-passivation conversion ability, excellent corrosion resistance, which is especially pronounced in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid. Its pitting resistance is excellent when used for neutral chloride-containing media. Grade 904L is not only resistant to crevice corrosion and stress corrosion, suitable for sulfuric acid of various concentrations below 70 °C, it is also resistant to corrosion in acetic acid, mixture of formic acid and acetic acid at any concentration and at any temperature under normal pressure. 904L is a completely austenitic structure, insensitive to the precipitation of ferrite and α phase, compared with general austenitic stainless steel which has a high molybdenum content.

Since 904L is of low carbon content (0.020% at maximum), it is free from carbide precipitation when done with general heat treatment and welding. It thus eliminates the risk of intergranular corrosion that occurs after general heat treatment and welding. Due to the high content of chromium, nickel and molybdenum and the addition of copper, 904L can be passivated even in reducing environments such as sulfuric acid and formic acid. The high nickel content gives it a lower corrosion rate in the active state. In pure sulfuric acid of concentration ranging from 0 to 98%, the operating temperature of 904L can be as high as 40 degrees Celsius. Its excellent corrosion resistance is manifested in pure phosphoric acid with concentration range from 0 to 85%. In industrial phosphoric acid produced through wet processing, impurities can bear great impact on corrosion resistance. While among all the various phosphoric acids, 904L is superior to common stainless steel in corrosion resistance. In the highly oxidizing nitric acid, 904L features lower corrosion resistance compared with highly alloyed steel without molybdenum. In hydrochloric acid, the application of 904L is limited to a lower concentration of 1-2%, within which range, 904L features better corrosion resistance than traditional stainless steel. Alloy 904L embodies a high resistance to pitting corrosion and its resistance to crevice corrosion in chloride solutions is also good. The high nickel content of the 904L reduces the rate of corrosion at the pits and gaps. Common austenitic stainless steels are sensitive to stress corrosion in a chloride-abundant environment with temperatures above 60 ° C while increasing the nickel content of the stainless steel helps. 904L has high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments due to its high nickel content.

904L Workability

Like ordinary stainless steel, 904L can be welded by a variety of welding methods. The most common welding method is manual arc welding or inert gas welding. The welding rod or welding wire is up to the composition of the base metal and is of higher purity, but its molybdenum content is required to be higher than that of the base metal. Preheating is generally not required before welding, but in cold outdoor operations joints or adjacent areas can be uniformly heated in order to avoid condensation of vapor. Note that the local temperature should not exceed 100 °C to avoid carbon accumulation and intergranular corrosion. When doing welding, it is suggested to adopt a small line energy, continuous and fast welding rate. Generally, no heat treatment is required after welding. If heat treatment is required, it must be heated to 1100 to 1150 °C and then cooled rapidly.

Chemical Compositions of 904L

Chemical compositions of 904L

Mechanical Properties of 904L

Mechanical Properties of 904L

904L Applications

  • 1) Petroleum, petrochemical equipment, such as reactors in petrochemical equipment;
  • 2) Storage and transportation equipment for sulfuric acid, such as heat exchangers;
  • 3) Power plant flue gas desulfurization device with uses mainly for the parts such as tower body of the absorption tower, flue, door panel, internal parts, sprinkler system, etc;
  • 4) Washers and fans in organic acid treatment systems;
  • 5) Seawater treatment equipment, seawater heat exchangers;
  • 6) Paper industry equipment;
  • 7) Pharmaceutical industry, like pharmaceutical plants: centrifuges, reactors, etc.;
  • 8) Sulfuric acid, nitric acid equipment, acid production;
  • 9) Other chemical equipment, pressure vessels;
  • 10) Food equipment, plant food containers such as soy sauce cans, cooking wine, salt shakers, equipment and dressings;
  • 11) Others.

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Contact

CIVMATS produces stainless steel products, such as pipes & fittings, bars. If you are in demand, please contact us:

  • Company: CIVMATS CO., LIMITED
  • Phone: 86-519-81809659
  • Fax: 86-519-81809959
  • Email: [email protected]
  • Address: 10th Floor, Xin Cheng Nan Du, Wujin District, Jiangsu, China
  • Website: www.civmats.com

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