yield strength or yield point is the material property defined as the stress at which a material begins to deform plastically. the material will deform elastically and will return to its original shape when the applied stress is removed, Yield strength of Q690D is around 789 MegaPascals. Like most steels of its grade, it suffers elongation before it pulls apart, typically at 18 percent of its initial length.
2, Tensile strength
Tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example breaking. Steel tensile strength is expressed in units of force divided by cross sectional area; in the Metric system, this unit is known as the Pascal. One Pascal is a Newton (the force needed to accelerate a one kilogram object to a velocity of one meter per second) per square meter. The tensile strength of Q690D steel is rated at around 859 MegaPascals