What does yield strength refer to in the context of steel?

Yield strength is a critical property of steel that defines the amount of stress or force that must be applied to the material in order to cause it to deform permanently. When the applied stress exceeds the yield strength, the steel will no longer return to its original shape after the load is removed, indicating that it has reached a point of plastic deformation. This property is essential in engineering and materials science because it helps determine how much load a structure can support before it begins to yield, ensuring safety and effectiveness in design.

The measurement of steel's ductility pertains to how much it can be deformed plastically without breaking, which is not directly what yield strength quantifies. Pressure needed to heat steel is irrelevant to the concept of yield strength and is more related to processing and manufacturing techniques. Lastly, tensile strength refers to the maximum amount of tensile stress that a material can withstand before failure, which conceptually differs from yield strength, focusing instead on the peak stress point rather than the transition to permanent deformation.