Its steel dubbed "Q", the representative . of the yield point of steel, behind the numbers indicate the yield point value, the unit is MPa yield point such as . Q235 (s) of 235 MPa of carbon structural steel. 2) when necessary, can be marked symbols representing steel Q345 steel property and specification are equivalent to Yield strength of Q345B is 345 Mega Pascals. Like most steels of its grade, it suffers elongation before it pulls apart, typically at 20-21 percent of its initial length. Tensile strength; The tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example breaking.