Duplex stainless steel

Advantages of duplex stainless steels compared to austenitic stainless steels

 
  • It has excellent resistance to stress corrosion cracking. Even the duplex stainless steel with the lowest alloy content has a higher resistance to stress corrosion cracking than austenitic stainless steel, especially in an environment containing chloride ions. Stress corrosion is a prominent problem that ordinary austenitic stainless steel is difficult to solve.
 
  • 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, etc. can even replace high-alloy austenitic stainless steel, and even corrosion-resistant alloys.
 
 
  • It has good local corrosion resistance. Compared with austenitic stainless steel with equivalent alloy content, its wear corrosion resistance and fatigue corrosion resistance are better than austenitic stainless steel.
 
  • 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.
 
  • Whether under dynamic load 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 .

Weaknesses of duplex stainless steels compared to austenitic stainless steels

  •  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 °C.
 
  • Its plasticity and toughness are lower than that of austenitic stainless steel, and its cold and hot working processes and forming properties are not as good as that of austenitic stainless steel.

  • There is a medium temperature brittle zone, and it is necessary to strictly control the process system of heat treatment and welding to avoid the appearance of harmful phases and damage the performance.

Advantages of duplex stainless steels compared to ferritic stainless steels

  •  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.
 
  •  Except for stress corrosion resistance, other localized corrosion resistance is better than ferritic stainless steel.
 
  • The cold working process performance and cold forming performance are far superior to those of ferritic stainless steel.
 
  • 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.
 
  • The application range is wider than that of ferritic stainless steel.

Weaknesses of duplex stainless steels compared to ferritic stainless steels

The content of alloying elements is high, the price is relatively high, and generally ferrite does not contain nickel.