The so-called d
uplex stainless steel has approximately half of the ferrite phase and half of the austenite phase in its solid solution structure. Generally, the minimum phase content needs to reach 30%, so it has the properties of both ferritic stainless steel and austenitic stainless steel. Features.
Compared with austenitic stainless steel, the advantages of duplex stainless steel are as follows:
①The yield strength is more than twice that of ordinary austenitic stainless steel, and it has sufficient plastic toughness required for molding. The wall thickness of storage tanks or pressure vessels made of duplex stainless steel is 30% to 50% lower than that of commonly used austenitic stainless steel, which is beneficial to reducing costs.
② It has excellent resistance to stress corrosion cracking, especially in environments containing chloride ions. Even duplex stainless steel with the lowest alloy content has a higher resistance to stress corrosion cracking than austenitic stainless steel. Stress corrosion is a common Austenitic stainless steel has outstanding problems that are difficult to solve.
③The corrosion resistance of 2205 duplex stainless steel, which is the most commonly used in many media, is better than that of ordinary 316L austenitic stainless steel, while super duplex stainless steel has extremely high corrosion resistance. In some media, such as acetic acid, formic acid, etc. It can even replace high-alloy austenitic stainless steel and even corrosion-resistant alloys.
④ It has good local corrosion resistance. Compared with austenitic stainless steel with a similar alloy content, due to the high strength and good corrosion resistance of duplex stainless steel, its wear corrosion resistance and corrosion fatigue properties are better than austenitic stainless steel. Stainless steel.
⑤The linear expansion coefficient is lower than that of austenitic stainless steel and close to that of carbon steel. It is suitable for connection with carbon steel and has important engineering significance, such as the production of composite plates or linings.
⑥Whether under dynamic or static load conditions, it has higher energy absorption capacity than austenitic stainless steel. For structural parts to cope with unexpected accidents such as collisions, explosions, etc., duplex stainless steel has obvious advantages and has practical application value.
Compared with austenitic stainless steel, the disadvantages of duplex stainless steel are as follows:
① The universality and versatility of applications are not as good as austenitic stainless steel. For example, the operating temperature must be controlled below 250°C for long-term applications.
② Its plastic toughness is lower than that of austenitic stainless steel, and its cold and hot processing technology and forming performance are not as good as austenitic stainless steel.
③ There is a medium-temperature brittle zone, and the process system of heat treatment and welding needs to be strictly controlled to avoid the appearance of harmful phases and damage to performance.
The disadvantage of duplex stainless steel compared with austenitic stainless steel is due to the large amount of ferrite structure in duplex stainless steel.
Compared with ferritic stainless steel, the advantages of duplex stainless steel are as follows:
①The comprehensive mechanical properties are higher than those of ferritic stainless steel, especially the plastic toughness. Not as sensitive to brittleness as ferritic stainless steels.
② In addition to stress corrosion resistance, other local corrosion resistance properties are better than ferritic stainless steel.
③Cold working process performance and cold forming performance are far superior to ferritic stainless steel.
④The welding performance is also much better than that of ferritic stainless steel. Generally, no preheating is required before welding, and no heat treatment is required after welding.
⑤The application range is wider than that of ferritic stainless steel.
The advantage of duplex stainless steel over ferritic stainless steel is that there is a large amount of austenite in duplex stainless steel.
Compared with ferritic stainless steel, another disadvantage of duplex stainless steel is its high alloying element content and relatively high price, and generally ferritic stainless steel does not contain nickel.
To sum up, we can generally see the overall performance and process performance of duplex stainless steel. It has won the favor of users with its superior mechanical and corrosion resistance comprehensive properties, and has become an excellent material that saves both weight and investment. Corrosion-resistant engineering materials.
