Mechanical property terms: yield, tensile, elongation and hardness
ReH/Rp0.2 is yield, Rm is tensile strength, A is elongation, HRB/HV is hardness. Understanding these symbols is essential to reading mill certificates and standards.
Mill certificates and standards use mechanical property symbols that determine whether material conforms:
• Yield strength: ReH (upper yield) or Rp0.2 (0.2% proof strength) — the stress at which noticeable plastic deformation begins. Austenitic grades usually specify Rp0.2; 304 is typically ≥205 MPa.
• Tensile strength Rm: maximum stress before fracture; 304 typically ≥515 MPa and 316L ≥485 MPa (varies with standard and thickness).
• Elongation A: elongation after fracture, a measure of ductility; 304 is usually ≥40% (50 mm gauge length).
• Hardness: HBW (Brinell), HV (Vickers), HRB/HRC (Rockwell); cold-worked tempers (e.g. half-hard 301) are much harder.
When reading a certificate:
1) Check the standard and test method (specimen orientation, gauge length).
2) Distinguish guaranteed values from measured values.
3) Mechanical values differ between cold-worked, deep-drawing and solution-annealed conditions — do not compare across conditions.
4) For high- or low-temperature service, also check high-temperature yield, impact toughness and other supplementary properties.
Knowing these symbols and units makes supplier communication much smoother.
