③ 标准/对比页
Q355B and ASTM A572 Gr50: Close, Not Interchangeable
Buyers moving between Chinese and American specifications keep asking for the Q355B equivalent in ASTM terms. The customary answer is A572 Gr50 — it sits in the same strength class — but the two grades are built by different standard systems, and treating them as interchangeable is where projects get stuck.
Why A572 Gr50 Is the Customary MatchQ355B under GB/T 1591 guarantees 355 MPa minimum yield with 470–630 MPa tensile; A572 Grade 50 occupies the same strength class on the ASTM side, which is why procurement teams reach for it first when translating a bill of materials. Similar class, however, is not equivalence — the standards verify chemistry, toughness and delivery differently.
What the Grade Card SaysOur grade data flags A572 Gr50 as a similar-strength counterpart, explicitly not a direct swap; the same caution applies to EN S355JR/J2 on the European side. Where drawings demand an ASTM designation, the clean route is ordering material certified to that designation rather than translating certificates across systems.
The Substitution ConversationReplacing A572 Gr50 line items with Q355B — or the reverse — is an engineering decision: the reviewer compares yield and tensile tables, impact requirements, carbon equivalence and the inspection regime. Bring the mill test certificate that states grade, standard edition and heat chemistry; that single document usually carries the discussion.
How We Ship ItYunhao supplies Q355B under GB/T 1591 in 8–100 mm, widths 1500–3200 mm, MOQ 25 t, 15–30 days from Tianjin or Qingdao. If the project runs on ASTM designations, tell us the target grade: we quote the practical route — GB-certified Q355B with full MTC, or ASTM-designated material where the specification demands it.
| Item | Q355B (GB/T 1591-2018) |
|---|---|
| Yield ReH (≤16 mm) | ≥355 MPa |
| Tensile Rm | 470–630 MPa |
| Charpy KV2 (B, +20 ℃) | ≥34 J |
| Yunhao supply thickness | 8–100 mm |
| ASTM counterpart | A572 Gr50 — similar class, substitution per design review |