904L stainless steel pipe description

904L stainless steel pipe 904L stainless steel seamless pipe 904L stainless steel welded pipe 316L stainless steel pipe

Super austenitic stainless steel 904L (00Cr20Ni25Mo4.5Cu; UNS: N08904; EN: 1.4539) is a high alloy austenitic stainless steel with low carbon content. It has good corrosion resistance in dilute sulfuric acid and is specially designed for environments with severe corrosion conditions. It has high chromium content and sufficient nickel content. The addition of copper makes it have strong acid resistance, especially high resistance to chloride interstitial corrosion and stress corrosion cracking. It is not easy to appear corrosion spots and cracks. Its resistance to pitting corrosion is slightly better than that of other steels. It has good processability and weldability, and can be used for pressure vessels.
Brand and standard:
UNS N08904 (a standard jointly designed by the Society of Automotive Engineers and the American Society for Testing and Materials in 1967), DIN1.4539 (a German standard), ASTM A240 (an American Society for Testing and Materials standard; the new standard classifies it as a stainless steel series, and the original standard ASME SB-625 classifies it as a nickel base alloy series), SUS890L.

ASTM 904l stainless steel tube -1
316L hollow stainless steel tube -2

Metallographic structure of 904L stainless steel:
904L is a completely austenitic structure. Compared with ordinary austenitic stainless steel with high molybdenum content, 904L has a significant effect on ferrite and α The precipitation of phase is not sensitive.
Physical and mechanical properties:
Density: 8.0g/cm3. Tensile strength: σ b≥520Mpa. Elongation: δ ≥35%. Corrosion resistance of 904L stainless steel:

Because the carbon content of 904L is very low (maximum 0.020%), there will be no carbide precipitation under general heat treatment and welding conditions. This eliminates the risk of intergranular corrosion after general heat treatment and welding. Because of the high content of chromium, nickel and molybdenum and the addition of copper, the 904L can be passivated even in reducing environments, such as sulfuric acid and formic acid. The high nickel content makes it have a low corrosion rate in the active state. In the concentration range of 0~98% of pure sulfuric acid, the use temperature of 904L can be as high as 40 ℃. The corrosion resistance of pure phosphoric acid in the concentration range of 0~85% is very good. In the industrial phosphoric acid produced by wet process, impurities have a strong impact on the corrosion resistance. Among all kinds of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. In strong oxidizing nitric acid, the corrosion resistance of 904L is lower than that of high alloyed steel without molybdenum. In hydrochloric acid, the use of 904L is limited to 1-2% of the lower concentration. In this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has high resistance to spot corrosion. In chloride solution, its crevice corrosion resistance is also very good. The high nickel content of 904L reduces the corrosion rate in pits and crevices. When the temperature of ordinary austenitic stainless steel is higher than 60 ℃, it may be sensitive to stress corrosion in a chloride rich environment. This sensitivity can be reduced by increasing the nickel content of 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 environment.

The 904L is used in the following fields:
*Petroleum and petrochemical equipment, such as reactors in petrochemical equipment.
*Storage and transportation equipment of sulfuric acid, such as heat exchanger.
*The flue gas desulfurization device of the power plant is mainly used in the absorber body, flue, shutter, internals, spraying system, etc.
*Scrubber and fan in organic acid treatment system.
*Sea water treatment plant, sea water heat exchanger, paper industry equipment, sulfuric acid and nitric acid equipment, acid making, pharmaceutical industry and other chemical equipment, pressure vessels, food equipment.
*Pharmaceutical factory: centrifuge, reactor, etc.
*Vegetable food: soy sauce pot, cooking wine, salt pot, equipment and dressings.
*904L is a matching steel for dilute sulfuric acid strong corrosive medium.

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