Grade families
S275, S355, historical Q345 and St52 designations, ASTM A572 and JIS SM grades use different standards. JR, J2, K2, N, NL and M suffixes can materially change the requirements. Do not remove these suffixes in an order or substitute table.
Microstructure and processing
Rolling, normalizing and thermomechanical routes affect grain structure, precipitation and weld response. Higher strength does not automatically confer better corrosion resistance or a better welded fatigue category. Surface coatings protect exposure but do not increase the certified base-metal strength.
Acceptance evidence
Compare the appropriate thickness-dependent strength, impact temperature, gauge length and delivery route. If the application requires class hull approval, an ordinary structural certificate is insufficient without acceptance. Recycled steel content alone does not determine the final certified properties.
Information to record
- Exact product standard and edition; approved drawing or specification revision.
- Grade, dimensions, final condition and heat-to-piece traceability.
- Acceptance test, inspection document and responsible approving party.
Frequently asked questions
Can a surface treatment make a lower grade equivalent?
No. Protective coatings do not change the underlying grade certification or mechanical acceptance requirements.
Sources and reference scope
- Procurement and editorial guidance — Cross-checked against product terminology and the cited material rules
Guidance describes checks to request. It is not a claim of available stock, certificates or completed project engineering. - 钢材产品简介 — Slides 3, 5–6, 15–19
Product forms, units and grade vocabulary; not proof of current stock or class certification.