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.