What are the performance advantages of duplex stainless steel

Duplex stainless steel is a type of stainless steel that contains about 50% of ferrite and austenite in its structure. Generally speaking, even if the content of a certain phase is at least not less than 30%, duplex stainless steel has both Characteristics of both ferritic and austenitic stainless steels.

Compared with austenitic stainless steel, duplex stainless steel has greater advantages. First, its yield strength multiple is stronger than that of ordinary austenitic stainless steel, and it also has sufficient plasticity and toughness required for forming. The wall thickness of storage tanks or pressure vessels made of duplex stainless steel is 30% to 50% less than that of commonly used austenitic stainless steel, which greatly reduces costs.
Secondly, the stress corrosion cracking resistance of duplex stainless steel is very good, especially in the environment containing chloride ions, even the duplex stainless steel with the lowest alloy content has higher stress corrosion cracking resistance than austenitic stainless steel, while Stress corrosion resistance is an outstanding problem that is often difficult to solve for ordinary austenitic stainless steel.
The third point is that the 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. This is because super duplex stainless steel has extremely high corrosion resistance, and in some media , Such as acetic acid, formic acid, etc. can also replace high-alloy austenitic stainless steel, and even corrosion-resistant alloys.
The fourth point is that duplex stainless steel has good local corrosion resistance. Compared with austenitic stainless steel with equivalent alloy content, duplex stainless steel has better wear resistance and corrosion fatigue performance than austenitic stainless steel.
The fifth point is that the linear expansion coefficient of duplex stainless steel is lower than that of austenitic stainless steel, close to carbon steel, and can be connected with carbon steel, which is of great engineering significance. For example, it can be used to produce stainless steel clad plates or linings.
The last point is that the energy absorption capacity of duplex stainless steel is better than that of austenitic stainless steel no matter under dynamic or static load conditions. When dealing with emergencies such as collisions and explosions, the practical application value of duplex stainless steel is very obvious.
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However, compared with austenitic stainless steel, duplex stainless steel also has disadvantages. First of all, the application universality and versatility of duplex stainless steel is not as good as that of austenitic stainless steel. For example, in long-term application, its service temperature must be controlled below 250°C.
Secondly, its plasticity and toughness are lower than that of austenitic stainless steel, and its cold and hot processing technology and formability are not as good as austenitic stainless steel.
Duplex stainless steel also has a medium-temperature brittle zone, and it is necessary to strictly control the heat treatment and welding process system to avoid the appearance of harmful phases and damage performance.
The most obvious disadvantage of duplex stainless steel compared with austenitic stainless steel is that the former contains a large amount of ferrite.
Let's talk about the advantages and disadvantages of duplex stainless steel and ferritic stainless steel. The advantage is that the comprehensive mechanical properties are higher than those of ferritic stainless steel, especially the plasticity and toughness. Not as sensitive to brittleness as ferritic stainless steels. Secondly, in addition to the stress corrosion resistance, the other localized corrosion resistance is better than that of ferritic stainless steel. The cold working performance and cold forming performance of duplex stainless steel are much better than those of ferritic stainless steel. In addition, the welding performance of duplex stainless steel is far better than that of ferritic stainless steel. Generally, no preheating is required before welding, and no heat treatment is required after welding. Another point is that the application range of duplex stainless steel is wider than that of ferritic stainless steel.
However, compared with ferritic stainless steel, the disadvantage of duplex stainless steel is that it has a high content of alloying elements and a relatively high price, because ordinary ferritic stainless steel does not contain nickel.