Duplex stainless steel is a corrosion-resistant stainless steel

Due to its special advantages, duplex 2205 pipe is widely used in petrochemical equipment, seawater and wastewater treatment equipment, oil and gas pipelines, papermaking machinery and other industrial fields. They are excellent stainless steel pipes. Duplex stainless steel has also been studied for use in the field of bridge load-bearing structures.

1. Neutral chloride environment

Duplex stainless steel is widely used in neutral chloride environments. In the process of manufacturing, a small amount of chloride ion-containing solution is usually used as cooling water, which causes stress in ordinary austenitic stainless steel (such as AISI 304/316). The tendency to corrode, and duplex stainless steel can solve this problem very well. The corrosion resistance is usually expressed by the pitting equivalent index PRE=Cr% +3.3Mo%+16N%, wherein the duplex stainless steel has a PRE value greater than 24 and an austenitic PRE less than 20.

2. Oil and gas industry

Since the 1980s, duplex stainless steel has been used more and more in the production of acid gas and oil, mainly used in the production of pipe linings, heat exchangers and pipeline systems onshore and offshore. Especially in the production of oil and natural gas, most of the duplex stainless steels face an acidic environment, that is, an environment containing a large amount of chloride ions, carbon dioxide and some sulfur dioxide. In the vicious environment of wet carbon dioxide containing chloride ions, duplex stainless steel is the first choice for an ideal material. It is resistant to high flow rate wear and corrosion and is more resistant to high flow rate wear and corrosion than carbon steel and stainless steel with corrosion inhibitor. It is also used in the uphole piping system to reduce the weight of materials.

3. Seawater environment

Seawater is one of the most corrosive media in the natural environment. In the case of hot sea water, super duplex stainless steel is mostly used. For example, a seawater exchanger made of SAF 2507 super duplex stainless steel has not been found to be corroded for 3 years, and the titanium tube can only be used for 3 months because it is not resistant to corrosion.

4. Pulp and paper industry

Duplex stainless steel has been in the development of pulp and paper industry for more than 40 years, and 3RE60 duplex stainless steel was first used in this field. In addition to 3RE60 steel, other duplex stainless steels such as UR45N (SAF2205), UR47N (00Cr25Ni6.5Mo3N), UR52N+ (00Cr25Ni6.5Mo3.5CuN) are used in various industrial fields.

5. Fertilizer industry

The urea industry is also one of the earliest departments to use duplex stainless steel. The heat exchange equipment containing chloride ion water in the device is used more. The original 304L austenitic stainless steel tube bundle was used, and the stress corrosion cracked one month later, causing leakage. Duplex stainless steel can be used for more than 5 years, and then the first and second stage coolers are also replaced with 18-5Mo or SAF2205 duplex stainless steel.

Due to the good corrosion resistance of the duplex stainless steel in the urea medium, it is suitable for the production of the key equipment of the urea production pump.

In addition, the domestic 0Cr25Ni6Mo3CuN aging strengthening duplex stainless steel has excellent wear and corrosion resistance.

6. Transportation industry

In recent years, the marine chemical transport ship industry is the largest duplex stainless steel user in foreign countries, accounting for about 50% of the hot rolled sheet. Chemical tankers carry a wide range of liquid cargoes, including chemical and petrochemical products, requiring cabin materials to be both corrosion resistant, high strength and excellent plasticity. At present, SAF2205 duplex stainless steel has replaced austenitic stainless steels such as 316L and 317L, making it the material of choice for marine chemical tankers.