The so-called duplex stainless steel is that the ferrite phase and the austenite phase account for half in its hardened structure, and the general minimum phase content may reach 30%.
Due to the characteristics of the two-phase structure, through the correct control of chemical composition and heat treatment process, DSS has the advantages of both ferritic stainless steel and austenitic stainless steel.
Compared with austenitic stainless steel, the advantages of duplex stainless steel are as follows
1. The yield strength is more than double that of ordinary austenitic stainless steel, and it has sufficient plasticity and toughness for forming. The wall thickness of storage tanks or pressure vessels made of duplex stainless steel is 30-50% lower than that of commonly used austenite, which is conducive to reducing costs.
2. Has excellent resistance to stress corrosion cracking, even the lowest alloyed duplex stainless steels have higher resistance to stress corrosion cracking than austenitic stainless steels, especially in chloride-containing environments. Stress corrosion is a prominent problem that ordinary austenitic stainless steel is difficult to solve.
3. The corrosion resistance of the most commonly used 2205 duplex stainless steel in many media is better than that of ordinary 316L austenitic stainless steel, while the super duplex stainless steel has extremely high corrosion resistance, and in some media, such as acetic acid, formic acid 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, its wear corrosion resistance and fatigue corrosion resistance are better than austenitic stainless steel.
5. The coefficient of linear expansion is lower than that of austenitic stainless steel, which is close to that of carbon steel. It is suitable for connecting with carbon steel and has important engineering significance, such as the production of clad plates or linings.
6. No matter under dynamic or static load conditions, it has higher energy absorption capacity than austenitic stainless steel, which has obvious advantages for structural parts to cope with sudden accidents such as collision, explosion, etc., 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 application are not as good as that of austenitic stainless steel, for example, its use temperature must be controlled below 250 degrees Celsius.
2. Its plasticity and toughness are lower than that of austenitic stainless steel, and its cold and hot working process and formability are not as good as that of 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 the performance.
Compared with ferritic stainless steel, the advantages of duplex stainless steel are as follows
1. The comprehensive mechanical properties are better than that of ferritic stainless steel, especially the plasticity and toughness, which is not as sensitive to brittleness as ferritic stainless steel.
2. Except for stress corrosion resistance, other localized corrosion resistance is better than ferritic stainless steel.
3. The cold working process performance and cold forming performance are much better than ferritic stainless steel.
4. The 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.
5. The application range is wider than that of ferritic stainless steel.
Compared with ferritic stainless steel, the disadvantages of duplex stainless steel are as follows
The content of alloying elements is high, the price is relatively high, and generally ferrite does not contain nickel.
To sum up, the general view of the service performance and process performance of duplex stainless steel can be seen. It has won the favor of users with its superior comprehensive mechanical and corrosion resistance properties, and has become an excellent product that saves both weight and investment. corrosion-resistant engineering materials.
