CN Quality Check
Standards Comparison Tool
EXECUTIVE SUMMARY
Scope: carbon structural steel Q235B (GB/T 700-2006) vs US ASTM A36/A36M and HSLA ASTM A572/A572M Gr.50, plus Chinese HSLA GB/T 1591-2018 (Q355). Landscape: NEQ — Q235B and A36 are close but not interchangeable (yield, tensile band, impact class differ); Q355 is the true A572 Gr.50 analogue. Key implication: A36 substitution for Q235B is acceptable only after re-checking yield (A36 higher) and impact grade (Q235B = +20 °C Charpy, A36 impact not mandatory).
APPLICABLE CHINESE STANDARDS
| Standard No. | Title (Chinese) | Scope | Mandatory/Recommended | Status |
|---|---|---|---|---|
| GB/T 700-2006 | 碳素结构钢 (Carbon structural steel) | Q195–Q275 plate/bar/section | Recommended | Current |
| GB/T 1591-2018 | 低合金高强度结构钢 (HSLA structural steel) | Q355–Q460 | Recommended | Current |
| GB/T 3274-2017 | 热轧钢板和钢带 (Hot-rolled plate & strip) | Plate dimensional/mechanical | Recommended | Current |
| GB 50017-2017 | 钢结构设计标准 (Design of steel structures) | Design (TIER 3) | Mandatory (design) | Current |
| GB 50205-2020 | 钢结构工程施工质量验收标准 (Acceptance of steel structure construction) | Installation/acceptance (TIER 3) | Mandatory | Current |
STANDARD TIER CLASSIFICATION
| Standard | Tier | Description |
|---|---|---|
| GB/T 700-2006 | TIER 1 — Product | Grade chemistry/mechanics |
| GB/T 1591-2018 | TIER 1 — Product | HSLA grades |
| ASTM A36/A36M-19 | TIER 1 — Product | US carbon steel |
| ASTM A572/A572M-21 | TIER 1 — Product | US HSLA |
| GB 50017-2017 / AISC 360-22 | TIER 3 — Design | Not compared numerically |
SCOPE BREAKDOWN
Q235B vs ASTM A36
Chinese standard: GB/T 700-2006 碳素结构钢 (Carbon structural steel)
International equivalent: ASTM A36/A36M-19 — ⚠️ verify newer edition
Equivalence: NEQ
Standard tier match: Both TIER 1 — valid comparison
| Parameter | Chinese Value (Clause) | International Value (Clause) | Deviation | Mutual Recognition | Procurement Impact |
|---|---|---|---|---|---|
| Yield ReH/Fy (t≤16 mm) | ≥235 MPa (GB/T 700-2006 Table 2) | ≥250 MPa (ASTM A36-19 Table 2) | +6.4% (A36 higher) | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Tensile Rm/Fu | 370–500 MPa (Table 2) | 400–550 MPa (Table 2) | Different band, non-overlapping lower bound | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Carbon | ≤0.20% (Table 1, grade B) | ≤0.26% (Table 1) | A36 permits higher C | 附加测试后互认 (Mutual recognition after additional testing) | LOW |
| P / S | ≤0.045% / ≤0.045% (Table 1, B) | ≤0.04% / ≤0.05% (Table 1) | Comparable | 直接互认 (Direct mutual recognition) | LOW |
| Impact (Charpy V) | +20 °C, ≥27 J (Table 3, B) | Not mandatory (unless ordered) | CN mandates, US optional | 不可互认 (Not mutually recognised) | HIGH |
| Deoxidation | Killed steel Z required (Table 1, B) | Not specified | N/A (only CN requires) | 附加测试后互认 (Mutual recognition after additional testing) | LOW |
Q355 vs ASTM A572 Gr.50
Chinese standard: GB/T 1591-2018 低合金高强度结构钢 (HSLA structural steel)
International equivalent: ASTM A572/A572M-21 Gr.50
Equivalence: NEQ (close analogue)
Standard tier match: Both TIER 1 — valid comparison
| Parameter | Chinese Value (Clause) | International Value (Clause) | Deviation | Mutual Recognition | Procurement Impact |
|---|---|---|---|---|---|
| Yield (t≤16 mm) | ≥355 MPa (GB/T 1591-2018 Table 2) | ≥345 MPa (A572-21 Table 2) | +2.9% (Q355 higher) | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Tensile | 470–630 MPa (Table 2) | ≥450 MPa (Table 2) | Different band | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Impact | +20 °C ≥34 J (grade B, Table 3) | Not mandatory | CN mandates | 不可互认 (Not mutually recognised) | HIGH |
KEY DIFFERENCES SUMMARY
- Yield — A36 +6.4% over Q235B; Q355 +2.9% over A572 Gr.50 → 附加测试后互认 (Mutual recognition after additional testing) — MEDIUM.
- Tensile band — non-overlapping lower bounds Q235B/A36 → 附加测试后互认 (Mutual recognition after additional testing) — MEDIUM.
- Impact testing — CN mandatory (+20 °C, ≥27 J for B); US optional → 不可互认 (Not mutually recognised) — HIGH.
- Carbon — A36 ≤0.26% vs Q235B ≤0.20% → 附加测试后互认 (Mutual recognition after additional testing) — LOW.
REGULATORY LINKAGE TABLE (法规联动)
| Compliance Scenario | Chinese Regulatory Basis | International Regulatory Basis |
|---|---|---|
| Mandatory product certification | Not CCC (steel exempt); mill 质保书 (Mill Test Certificate) per GB/T 700 | ASTM A6 / mill cert; no mandatory listing |
| Engineering acceptance | GB 50205-2020 | AISC 360-22 / local code |
| Import/export compliance | CCIB commodity inspection | Destination customs + ASTM cert |
| Designer obligation | GB 50017-2017 | AISC 360-22 / Eurocode 3 |
AUDIT FLAG RESOLUTION
- ✅ RESOLVED: Q235B C ≤0.20% (GB/T 700-2006 Table 1, grade B) — B draft's ≤0.22% applies to Q235A only.
- ✅ RESOLVED: Q235B killed steel (Z) required — B draft correct.
- ✅ FALSE POSITIVE (domain flag): GB 50017-2017 used only as TIER 3 design reference, not product comparison — valid.
- ⚠️ UNRESOLVED: ASTM A36/A36M edition — verify current edition before procurement.
- 🔴 CRITICAL CORRECTION: Do NOT label GB/T 700 as "GB 700" — correct designation is GB/T 700-2006 (recommended, not mandatory).
PROCUREMENT VERDICT
- Confirm grade + impact class (B = +20 °C) on mill cert.
- For A36 substitution, re-verify yield ≥235 MPa and request Charpy +20 °C ≥27 J.
- For A572 Gr.50 substitution, use Q355 and confirm impact grade.
- Verify ASTM edition year on cert.
- Require 质保书 (Mill Test Certificate) per GB/T 700.
- Cross-check design against GB 50017-2017 or AISC 360-22.
REFERENCE DOCUMENT CHECKLIST (配套调阅清单)
- GB/T 700-2006 §Table 1 — chemistry (C, P, S, deoxidation)
- GB/T 700-2006 §Table 2 — yield/tensile by thickness
- GB/T 700-2006 §Table 3 — impact energy
- GB/T 1591-2018 §Table 2/3 — Q355 mechanics/impact
- ASTM A36/A36M §5, Table 1/2 — chemistry/mechanics
- ASTM A572/A572M §Table 2 — Gr.50 properties
FIELD INSPECTION CHECKLIST
- Verify heat number matches mill cert.
- Confirm killed-steel (Z) designation for Q235B.
- Check Charpy test report at +20 °C ≥27 J.
- Measure plate thickness vs yield table band.
- Confirm grade stamping on sections.
CONFIDENCE RATING
🟡 MEDIUM — core values cross-verified; ASTM edition year and A572 impact clause flagged for official text confirmation.
Technical comparison report — CN Quality Check Standards Tool. Not a substitute for official standard texts or on-site verification. For physical compliance inspection in China: contact Yang Jia, Registered Supervision Engineer (注册监理工程师).
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