The Characterics of Stainless Steel

• Conventional reinforcement is made from ”black steel”, i.e. low alloyed carbon steel, with a content of about 0.2% of carbon, being the most essential alloying element.
  
  
• By adding alloy elements such as chrome, nickel and molybdenum a considerable improvement of the corrosion resistance of the steel is achieved.

  
  

  According to EN 10088-1 the classification of stainless steel is a minimum content of 10.5% chrome and maximum 1.2% carbon.

  
  

  Stainless steel alloys, used for reinforcement often have a higher content of chrome, as well as addition of nickel and maybe molybdenum to increase the corrosion resistance further.

  
  

  A large number of steel could rightly be defined as stainless due to the content of chrome, but the corrosion resistance differs a lot, depending on the composition of the specific alloy.

  
  

  Besides the mechanical characters of the stainless steel alloys are different, which primarily depend on the microstructures of the alloys.

  
  
• Stainless steel are divided into four main groups, depending on the microstructures of the steel:
  
  
  • Martensitic og Ferritic:
    

    Martensitic and ferritic stainless steels are not used for reinforcement, due to a proportional low corrosion resistance, and risk of a brittle fractures.

    
    
  • Austenitic:
    

    Austenitic stainless steels combine good corrosion resistance with a high strength and excellent post forming. Therefore they are very popular for a lot of applications, including reinforcement of concrete structures.

    
    
  • Duplex (Austenitic-Ferritic):
    

    Duplex alloys combine the best qualities of the austenitic and ferritic steels. This means that the duplex alloys offer an even better corrosion resistance and strength than the austenitic steel, and at the same time have a good weldability and post forming. The processing of the duplex steels is, however, more demanding.