Typical composition of S355 (automotive grade)?
C≤0.22%, Si≤0.55%, Mn≤1.60%, P≤0.025%, S≤0.015%.
Mechanical properties (key automotive indicators)?
Yield strength: 355MPa (≤16mm)
Tensile strength: 470–630MPa
Elongation: ≥21% (JR); ≥25% (MC)
Impact: JR (≥27J at 20℃), J2 (≥27J at -20℃), MC (excellent for cold forming)
Hardness (HB)?
140–190HB, easy to cut/drill/stamp.
Fatigue performance (core automotive aspect)?
High-cycle fatigue ≈180–220MPa, about 40% better than Q235, suitable for chassis/suspension alternating loads.
Weldability (key automotive aspect)? Carbon equivalent ≤0.40%, no preheating required for conventional welding; for thick plates (>20mm), preheating at 100–150℃ is necessary to prevent cracking.