What is the microstructure of alloy steel

What is stainless steel?

  • Traditional reinforcing steel is made from "black steel", that is, from low-alloy carbon steel with a carbon content of approx. 0.2% as the most important alloying element.

  • The addition of elements such as chromium, nickel or molybdenum significantly improves the corrosion resistance of the steel.

    According to EN 10088-1, steel with a chromium content of at least 10% and a carbon content of at most 1.2% can be described as rustproof.

    Stainless alloys including used for concrete reinforcement usually have a higher chromium content and often also contain nickel and molybdenum as an additional alloy in order to increase the corrosion resistance even further.

    Many steels can be classified as stainless because of their chromium content, but there are considerable differences in corrosion resistance depending on the specific alloy composition.

    In addition, the mechanical properties, which primarily depend on the microstructure of the alloy, are considerable.

  • Depending on the microstructure of the alloy, there are four main groups of stainless steel:

    • Martensitic and Ferritic:
      Steels of this group are not used as reinforcing steel because of their relatively low corrosion resistance and the risk of brittle fractures.

    • These steels combine good corrosion resistance with great strength and excellent formability.
      They are therefore well suited for a number of uses including: as reinforcing steel.

    • Duplex (austenitic-ferritic):
      Duplex alloys combine the best properties of austenitic and ferritic steel. This means that duplex alloys have even higher corrosion resistance and strength than austenitic steels. At the same time, they have good weldability and malleability.
      The processing of duplex steels is, however, demanding.