What is duplex stainless steel? What are the characteristics of duplex stainless steel?

What is duplex stainless steel? What are the characteristics of duplex stainless steel?

1. Definition of duplex stainless steel

Under normal circumstances, the ferrite content in austenitic stainless steel is 50%-60%, while the ferrite content in duplex stainless steel is higher, up to more than 75%.

Since both austenitic stainless steel and ferritic stainless steel have good corrosion resistance and there is a large composition difference between them, the two stainless steels are not one material, but two materials with different properties.

Duplex stainless steel is a stainless steel in which austenite and ferrite coexist. It has good corrosion resistance, high temperature strength and plasticity, toughness and processability.

Since austenitic stainless steel has good mechanical properties at room temperature, it is often used to make structural parts that require high strength; while ferritic stainless steel has poor mechanical properties at room temperature and is generally used to make structural parts that require good high and low temperature properties. .

2. Composition and properties of duplex stainless steel

The composition (mass fraction) of duplex stainless steel is similar to that of ordinary austenitic stainless steel, but due to the different proportions of its two phases, it has the following characteristics:

1. Excellent resistance to intergranular corrosion;

2. It has good welding performance and can be welded below 600℃;

3. It has good resistance to stress corrosion cracking, and its corrosion resistance is better than that of austenitic stainless steel in environments such as pitting corrosion and crevice corrosion;

4. Has good high temperature antioxidant properties.

Due to the different proportions of the two phases, duplex stainless steel has significant differences in performance, so duplex stainless steel is more superior than ordinary austenitic stainless steel. Stainless steel with various properties can be obtained by adjusting the proportion of the two phases in production.