Author: S. Lundberg
AIST Conference 2010, Pittsburgh, USA, May 3-6, 2010
In later years the market for high strength rebar, with yield strength of 500 MPa and higher has increased dramatically. High strength is required in combination with specified ratio of tensile strength over yield strength, bending properties, elongation and weldability 1– 3. The traditional method to meet these requirements has been to manufacture low alloyed Si–Mn–, or Mn–Cr–steels, or especially for grades for welding, micro–alloyed steels, fine grain treated, with V, Nb or possibly Ti.
Due to the costs for alloys to make low– and micro–alloyed steels, a process for surface quenching and self tempering of low carbon steels was developed already during the late 1970s4–6. The method makes it possible to produce all rebar grades from one single chemical composition of the steel. Thus not only the alloy costs for high strength rebar is reduced, but also the planning situation in the melt shop is simplified.