Mechanical properties (t≤16mm)?
Yield strength **≥345MPa**; Tensile strength 470–630MPa; Elongation **≥21%**; Passes 180° cold bending test.
Does strength change with thickness?
Yes. The greater the thickness, the lower the yield strength:
16–35mm: ≥335MPa
35–50mm: ≥325MPa
50–100mm: ≥295MPa
Difference between Q345 and Q235?
Strength: Q345 yield strength is about 50% higher.
Composition: Q345 contains Mn (1.0–1.6%), Q235 is low in manganese.
Applications: Q345 is used for heavy-duty/dynamic loads (bridges, crane beams); Q235 is used for general structures.
Relationship between Q345 and Q355?
Q355 is an upgraded replacement for Q345 (effective from February 1, 2019). Main differences:
Q355 yield strength **≥355MPa**
S and P are more strictly controlled, resulting in better low-temperature toughness.
Is 16Mn the same as Q345?
Yes. 16Mn (old grade) = Q345 (new grade), with essentially the same composition and properties.