What is Q355 steel?
Q355 is a low-alloy high-strength structural steel specified in the Chinese national standard GB/T 1591-2018, replacing the older grades 16Mn and Q345.
What does the Q355 grade designation mean?
Q: The first letter of the pinyin for yield strength (Qu);
355: Minimum yield strength ≥ 355MPa for thickness ≤ 16mm;
A/B/C/D/E: Quality grades (different impact temperatures and P/S content).
What are the quality grades of Q355? What are the differences?
The standards are divided into five levels: A, B, C, D, and E. The core differences lie in the impact temperature and the upper limit of harmful elements (P/S):
A: No impact requirement, P≤0.045%, S≤0.045%;
B: Impact at 20℃ ≥34J, P≤0.040%, S≤0.040%;
C: Impact at 0℃ ≥34J, P≤0.035%, S≤0.035%;
D: Impact at -20℃ ≥27J, P≤0.030%, S≤0.025%;
E: Impact at -40℃ ≥27J, P≤0.025%, S≤0.025%.
What are the core differences between Q355, Q345, and Q235? Q235: Ordinary carbon structural steel, yield strength 235MPa, lowest strength and lowest price;
Q345: Older low-alloy high-strength steel, yield strength 345MPa, replaced by Q355;
Q355: New generation low-alloy high-strength steel, yield strength 355MPa, superior strength, toughness, and weldability.
What is the international equivalent of Q355?
Approximate equivalents: S355JR (European standard EN 10025), A572 Gr.50 (American standard ASTM), but the composition and impact requirements differ.