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Home / Bloglist / Advantages and disadvantages of duplex stainless steel

Advantages and disadvantages of duplex stainless steel

Duplex stainless steel has the characteristics of both austenitic and ferritic stainless steel, has excellent pitting corrosion resistance, and is also a nickel-saving stainless steel. The resistance to pitting corrosion, crevice corrosion, stress corrosion and corrosion fatigue of duplex stainless steel is obviously better than that of ordinary austenitic stainless steel, and can be comparable to high alloy austenitic stainless steel.


The basic advantages of duplex stainless steel are as follows:


(1) Duplex stainless steel with chromium content of 18%-22% has good resistance to neutral chloride stress corrosion under low stress. The 18-8 type austenitic stainless steel generally used in neutral chloride solutions above 70Y is prone to stress corrosion cracking cv548. Heat exchangers and evaporators made of this type of stainless steel are used in industrial media with trace chloride and hydrogen sulfide. Such equipment has a tendency to produce stress corrosion cracking, while duplex stainless steel has good resistance.


(2) Molybdenum-containing duplex stainless steel has good pitting corrosion resistance. With the same pitting corrosion equivalent value (PR5=cr%*3.3%Moll6%N), the critical pitting corrosion potential of duplex stainless steel and austenitic stainless steel is similar. The pitting corrosion resistance of duplex stainless steel containing 18% cr is comparable to that of AIsl316L. The pitting and crevice corrosion resistance of high-chromium duplex stainless steel containing 25% Cr, especially nitrogen, exceeds AISI 316L.


(3) It has good corrosion fatigue resistance and wear corrosion resistance, and is used in pumps, valves and other equipment under certain corrosive medium conditions.


(4) Good comprehensive mechanical properties, high strength and fatigue strength, and yield strength is twice that of 18-8 type austenitic stainless steel.


(5) The weldability is good, and the hot cracking tendency is small. Generally, no preheating is required before welding, and no heat treatment is required after welding. It can be welded with dissimilar steels such as 18-8 type austenitic stainless steel or carbon steel.


(6) The hot working temperature range of the low-chromium (18%cr) duplex stainless steel is wider than that of the 18-8 type austenitic stainless steel, and the resistance is small. c?) steel is more difficult to heat than austenitic stainless steel.


(7) Compared with austenitic stainless steel, the thermal conductivity is large and the linear expansion coefficient is small, and it is also suitable for making the tube core of the heat exchanger.


Duplex stainless steel has the following disadvantages:


(1) Compared with austenitic stainless steel, it has lower heat resistance and is generally used in a working environment below 300Y.


(2) Cold addition r has a greater effect of hardening than 18-8 type austenitic stainless steel. In the initial stage of deformation of the tube and plate, a large force is required to deform, and the internal stress generated by the tube and plate is also large. .


(3) There is a medium temperature brittle zone, which is unfavorable for heat treatment and welding.


(4) Duplex stainless steel containing 25% cr is more difficult to hot work than austenitic stainless steel.

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