Two advantages of 904L super austenitic stainless steel

904L is a super austenitic stainless steel with low carbon and high nickel and molybdenum. It has very good activation and passivation transformation capabilities, and excellent corrosion resistance. It has excellent performance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid. Excellent corrosion resistance, excellent pitting resistance in neutral chloride-ion-containing medium, and excellent crevice corrosion resistance and stress corrosion resistance. The corrosion resistance is also very good in various concentrations of sulfuric acid at temperatures below 70°C, and in the mixed acid of acetic acid, formic acid and acetic acid at any concentration and at any temperature under normal pressure.

904L austenitic stainless steel has strong corrosion resistance. Because the carbon content of 904L is extremely low, carbides will not be precipitated during general heat treatment and welding. This eliminates the risk of intergranular corrosion which occurs after ordinary heat treatment and welding. Because of 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 higher nickel content can make it have a lower corrosion rate in the active state. In pure sulfuric acid in the concentration range below 98%, the service temperature of 904L austenitic stainless steel is as high as 40°C.
In pure phosphoric acid in the concentration range of 0-85%, its corrosion resistance is very good. In industrial phosphoric acid produced by wet process, impurities have a very strong influence on corrosion resistance. Among all kinds of phosphoric acid, 904L stainless steel has better corrosion resistance than ordinary stainless steel. In strong oxidizing nitric acid, 904L has lower corrosion resistance than high-alloyed steel grades without molybdenum. In hydrochloric acid, the use of 904L super austenitic stainless steel is limited to a lower concentration of 1-2%. in this concentration range. The corrosion resistance of 904L is better than conventional stainless steel. 904L steel has high resistance to pitting corrosion. Its crevice corrosion resistance is also very good in chloride solutions. The high nickel content of 904L reduces the corrosion rate in pits and crevices. Ordinary austenitic stainless steels may be susceptible to stress corrosion in a chloride-rich environment at temperatures above 60°C, and this sensitization can be reduced by increasing the nickel content of the stainless steel. Due to the high nickel content, 904L has a high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.
The welding performance of 904L super austenitic stainless steel is also good, the same as ordinary stainless steel, 904L stainless steel can be welded by various welding methods. The most commonly used welding method is manual arc welding or inert gas shielded welding. The electrode or wire metal is based on the composition of the base metal and has higher purity, and the content of molybdenum is required to be higher than that of the base metal. Preheating is generally not required before welding, but in cold outdoor operations, in order to avoid condensation of water vapor, the joints or adjacent areas can be evenly heated. Note that the local temperature should not exceed 100°C to prevent carbon accumulation and lead to intergranular corrosion.