Structural Steels
Low alloy steels are used for structural purposes. Such steels are required to possess high yield stress, good ductility and high fatigue resistance. The high yield stresses result in direct weight saving in part of the structure.
A typical low alloy structural steel will have following composition : C – 0.12%, Mn – 0.75%m Si – 0.25%, Cu – 0.3% .This alloy steel has a yield strength of 350 N/mm2 and about 15% elongation after hot rolling. The presence of Cu improves corrosion resistance while Mn and Si improve weldability by preventing weld embrittlement.
Small amounts of Ni, Cr and V added to these steels may improve the yield strength to 625 N/mm2 if used in quenched and tempered conditions. Additions of Ni, Cr and V do not effect the weldability.