904L (US UNS N08904 / German DIN 1.4539)

904L chemical properties:

904L mechanical properties:

904L solid solution state, mechanical properties of the alloy at room temperature:

This alloy has the following properties:

904L is a kind of austenitic stainless steel with low carbon content and high alloyed gold. The steel is designed for environments with severe corrosion conditions. As the carbon content of 904L is very low (0.020% at most), there will be no carbide precipitation under the condition of general heat treatment and welding. This eliminates the risk of intergranular corrosion after general heat treatment and welding. Because of the high content of Cr, Ni, Mo and the addition of Cu, 904L can be passivated even in reducing environment, such as sulfuric acid and formic acid. In the concentration range of 0 ~ 98%, the temperature of pure sulfuric acid can reach 40 ℃. In the concentration range of 0 ~ 85% pure phosphoric acid, its corrosion resistance is very good. In industrial phosphoric acid produced by wet process, impurities have a strong influence on corrosion resistance. Among all kinds of phosphoric acid, 904L is superior to ordinary stainless steel in corrosion resistance. In the strong oxidizing nitric acid, 904L has lower corrosion resistance than the high alloy steel without molybdenum. In hydrochloric acid, 904L is limited to a lower concentration of 1-2%. In this concentration range, 904L steel has high resistance to spot corrosion. In chloride solution, it has good resistance to crevice corrosion. 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

Metallographic structure:

904L is fully austenitic.

904L applications include:

904L alloy is a multi-purpose material, which can be applied in many industrial fields:

1. Petroleum and petrochemical equipment, such as reactors in petrochemical equipment

2. Sulfuric acid storage and transportation equipment, such as heat exchanger, etc

3. The main parts of FGD device in power plant are: absorber body, flue, baffle, internals, spray system, etc

4. Scrubber and fan in organic acid treatment system

5. Sea water treatment device, sea water heat exchanger, papermaking equipment, sulfuric acid, nitric acid equipment, acid making, pharmaceutical industry and other chemical equipment

6. Dilute sulfuric acid strong corrosive medium 904L is the matching steel

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