904L stainless steel seamless pipe
904L (N08904, 14539) super austenitic stainless steel containing 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, which is a proprietary material introduced by French H·S company.
It has good activation-passivation conversion ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, phosphoric acid, and good in neutral chloride-containing media.
It is resistant to pitting and has good resistance to crevice corrosion and stress corrosion. It is suitable for various concentrations of sulfuric acid below 70 °C. It is resistant to any concentration, any temperature of acetic acid under normal pressure, and the corrosion resistance of formic acid and acetic acid.
Characteristics of 904L stainless steel seamless pipe
Since the 904L carbon content is very low (maximum 0.020%), there is no carbide precipitation in the case of general heat treatment and welding. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and soldering. Due to the high chromium-nickel-molybdenum content and the addition of copper.
It 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 the pure sulfuric acid range of 0 to 98%, the temperature of 904L can be as high as 40 °C. The corrosion resistance is very good in pure phosphoric acid in the range of 0-85%. In industrial phosphoric acid produced by the wet process, impurities have a strong influence on corrosion resistance. Among all the various phosphoric acids, the 904L stainless steel tube is superior in corrosion resistance to ordinary stainless steel tubes.
In the highly oxidizing nitric acid, the corrosion resistance is lower than that of the highly alloyed steel containing no molybdenum. In hydrochloric acid, the use of 904L stainless steel tubing is limited to a lower concentration of 1-2%. In this concentration range. The corrosion resistance of the 904L stainless steel tube is better than that of conventional stainless steel.
The 904L stainless steel tube is highly resistant to pitting corrosion. Its resistance to crevice corrosion in chloride solutions is also good. The high nickel content of the 904L stainless steel tube reduces the rate of corrosion at the pits and gaps. Ordinary austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 ° C.
This sensitization can be reduced by increasing the nickel content of the stainless steel. Due to its high nickel content, the 904L stainless steel tube has high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.
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