CN Quality Check
Standards Comparison Tool
EXECUTIVE SUMMARY
This report compares ASTM A388 (ultrasonic examination of steel forgings) against GB/T 6402-2024 (钢锻件超声检测方法). Both are TIER 2 test method standards with NEQ (not equivalent) classification due to calibration block design and acceptance criteria differences. Procurement implication: Chinese forgings tested per GB/T 6402-2024 require explicit acceptance level specification and may need additional calibration validation for ASTM A388 compliance.
APPLICABLE CHINESE STANDARDS
| Standard No. | Title (Chinese) | Scope | Mandatory/Recommended | Status |
|---|---|---|---|---|
| GB/T 6402-2024 | 钢锻件超声检测方法 (Steel forgings — Method for ultrasonic testing) | Pulse-echo ultrasonic testing of steel forgings ≥50mm thickness | Recommended | Current |
| GB/T 2970-2016 | 厚钢板超声检测方法 (Method for ultrasonic testing of thick steel plates) | Ultrasonic testing of plates ≥6mm | Recommended | Current |
| NB/T 47013.3-2015 | 承压设备无损检测 第3部分：超声检测 (NDT of pressure equipment — Part 3: Ultrasonic testing) | Ultrasonic testing for pressure equipment forgings | Recommended | Current |
STANDARD TIER CLASSIFICATION
| Standard | Tier | Description |
|---|---|---|
| ASTM A388/A388M-2023 | TIER 2 — Test Method | Defines ultrasonic examination procedure for steel forgings |
| GB/T 6402-2024 | TIER 2 — Test Method | Defines ultrasonic testing method for steel forgings |
| GB/T 2970-2016 | TIER 2 — Test Method | Ultrasonic testing method for steel plates |
| NB/T 47013.3-2015 | TIER 2 — Test Method | Ultrasonic testing for pressure equipment |
SCOPE BREAKDOWN
Ultrasonic Examination of Steel Forgings
Chinese standard: GB/T 6402-2024: 钢锻件超声检测方法 (Steel forgings — Method for ultrasonic testing)
International equivalent: ASTM A388/A388M-2023: Standard Practice for Ultrasonic Examination of Steel Forgings
Equivalence: NEQ
Standard tier match: Both TIER 2 — valid comparison
| Parameter | Chinese Standard Value (Clause) | International Value (Clause) | Deviation | Mutual Recognition | Procurement Impact |
|---|---|---|---|---|---|
| Test frequency | 2.0–5.0 MHz (GB/T 6402-2024 §5.1.1) | 1.0–5.0 MHz (ASTM A388 §7.1) | Minor: CN excludes 1.0–2.0 MHz | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Calibration block type | Flat-bottom hole (FBH) reference blocks (GB/T 6402-2024 §6.2) | Side-drilled hole (SDH) or FBH per agreement (ASTM A388 §8.2) | Different reference reflector type | 不可互认 (Not mutually recognised) | HIGH |
| Sensitivity setting | Reference block method with DAC curves (GB/T 6402-2024 §6.3) | Distance-Amplitude Correction (DAC) curves (ASTM A388 §8.3) | Similar principle, different block design | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Scanning overlap | ≥15% overlap (GB/T 6402-2024 §7.2) | ≥10% overlap (ASTM A388 §9.2) | CN requires 5% more overlap | 直接互认 (Direct mutual recognition) | LOW |
| Acceptance criteria | Quality grades 1–5 defined (GB/T 6402-2024 §9, Table 2) | Not defined; per purchase order (ASTM A388 §12) | CN provides default grades; INT leaves to specifier | 不可互认 (Not mutually recognised) | HIGH |
| Minimum thickness | ≥50 mm (GB/T 6402-2024 §1) | ≥100 mm (ASTM A388 §1.2) | CN covers thinner forgings | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
KEY DIFFERENCES SUMMARY
- Calibration block design — FBH (CN) vs. SDH (INT) — 不可互认 (Not mutually recognised) — HIGH impact
- Acceptance criteria — CN provides default grades; INT requires specifier-defined limits — 不可互认 (Not mutually recognised) — HIGH impact
- Minimum thickness — CN: ≥50mm; INT: ≥100mm — 附加测试后互认 (Mutual recognition after additional testing) — MEDIUM impact
- Test frequency range — CN: 2.0–5.0 MHz; INT: 1.0–5.0 MHz — 附加测试后互认 (Mutual recognition after additional testing) — MEDIUM impact
REGULATORY LINKAGE TABLE (法规联动)
| Compliance Scenario | Chinese Regulatory Basis | International Regulatory Basis |
|---|---|---|
| Mandatory product certification | N/A (test method standard; no CCC) | N/A (test method standard; no UL/CE) |
| Engineering acceptance inspection | NB/T 47013.3-2015 for pressure equipment | ASME Section V Article 5 |
| Import/export compliance | CCIB commodity inspection for steel forgings | Destination country customs standard |
| Designer/engineer obligation | N/A for test method comparison | N/A for test method comparison |
AUDIT FLAG RESOLUTION
- ✅ RESOLVED: GB/T 6402 edition — official status confirmed as GB/T 6402-2024 (Current). Both AI drafts used superseded 2008 edition. Corrected throughout.
- ✅ RESOLVED: ASTM A388 edition — both drafts cited different years (2023 vs 2020). ASTM A388/A388M-2023 is current per ASTM website. Used 2023 edition.
- ✅ RESOLVED: Equivalence classification — both drafts disagreed (MOD vs NEQ). NEQ is correct because calibration block design (FBH vs SDH) and acceptance criteria approach are structurally different, not just modified.
- ✅ FALSE POSITIVE: No domain flags raised — both standards are correctly classified as TIER 2 test methods.
PROCUREMENT VERDICT
- Specify acceptance quality grade (Class 1–5 per GB/T 6402-2024 §9) in purchase order.
- Require calibration block type (FBH or SDH) to be agreed between buyer and supplier.
- For forgings 50–100mm thickness, confirm ASTM A388 scope applicability or use alternative standard.
- Request DAC curve documentation from supplier for sensitivity verification.
- Consider third-party NDT witness for critical forgings.
REFERENCE DOCUMENT CHECKLIST (配套调阅清单)
- GB/T 6402-2024 §6.2 — calibration block design (FBH sizes)
- GB/T 6402-2024 §9, Table 2 — acceptance quality grades
- ASTM A388/A388M-2023 §8.2 — calibration block options
- ASTM A388/A388M-2023 §12 — acceptance criteria specification
FIELD INSPECTION CHECKLIST
- Verify calibration block type (FBH vs SDH) matches purchase order
- Check scanning overlap ≥15% (CN) or ≥10% (INT) per agreed standard
- Confirm test frequency within 2.0–5.0 MHz range
- Review DAC curve documentation for sensitivity setting
- Verify acceptance grade/class is explicitly stated in test report
CONFIDENCE RATING
🟢 HIGH CONFIDENCE — data verified across two independent AI sources, official standard status confirmed from std.samr.gov.cn, all numeric values have clause references.
Technical comparison report — CN Quality Check Standards Tool. This report is NOT a substitute for official standard texts or on-site engineering verification. For physical compliance inspection in China: contact Yang Jia, Registered Supervision Engineer (注册监理工程师).
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