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Standards Comparison Report
astm A 388
EXECUTIVE SUMMARY
This report compares ASTM A388/A388M-19 (ultrasonic examination of steel forgings) with Chinese equivalents GB/T 6402-2024 and NB/T 47013.3-2015. Both Chinese standards are TIER 2 test methods, but they are NEQ (not equivalent) to ASTM A388 due to fundamentally different calibration methods (DAC vs DGS/reference blocks) and acceptance criteria. Procurement implication: direct substitution is impossible; additional testing per destination standard is mandatory.
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) | Ultrasonic testing of ferritic/martensitic steel forgings | Recommended | Current |
| NB/T 47013.3-2015 | 承压设备无损检测 第3部分：超声检测 (Nondestructive testing of pressure equipment—Part 3: Ultrasonic testing) | Ultrasonic testing for pressure equipment forgings | Recommended (industry-specific) | Current |
| GB/T 26638-2011 | 液压机上钢质自由锻件 复杂程度分类及折合系数 (Classification and conversion coefficient for steel open die forgings on hydraulic press) | Classification of forging complexity | Recommended | Current |
| GB/T 17107-2025 | 锻件用结构钢棒 (Structural steel bars for forgings) | Material specification for forging steel bars | Recommended | Current |
STANDARD TIER CLASSIFICATION
| Standard | Tier | Description |
|---|---|---|
| ASTM A388/A388M-19 | TIER 2 — Test Method | Defines ultrasonic examination practice for steel forgings |
| GB/T 6402-2024 | TIER 2 — Test Method | Defines ultrasonic testing method for steel forgings |
| NB/T 47013.3-2015 | TIER 2 — Test Method | Defines ultrasonic testing method for pressure equipment |
| GB/T 26638-2011 | TIER 1 — Product Standard | Defines forging classification |
| GB/T 17107-2025 | TIER 1 — Product Standard | Defines material requirements |
SCOPE BREAKDOWN
Ultrasonic Testing Method
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-19: 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 |
|---|---|---|---|---|---|
| Calibration method | DGS diagram or reference blocks with flat-bottom holes (GB/T 6402-2024 §5.2) | Distance-Amplitude Correction (DAC) with basic calibration block (ASTM A388 §6.2) | Different methodology (no direct comparison) | 不可互认 (Not mutually recognised) | HIGH |
| Acceptance levels | Quality grades 1–5 based on equivalent flaw size (GB/T 6402-2024 §7.1) | Reference notch/notch sizes (ASTM A388 §9.1) | Different classification system | 不可互认 (Not mutually recognised) | HIGH |
| Scanning sensitivity | Set using DGS curve or reference block (GB/T 6402-2024 §5.3) | Set using DAC curve from calibration block (ASTM A388 §6.3) | Different sensitivity setting method | 不可互认 (Not mutually recognised) | HIGH |
| Frequency range | 2–5 MHz typical (GB/T 6402-2024 §4.1) | 1–5 MHz typical (ASTM A388 §5.1) | Minor overlap | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
| Couplant | Water, oil, or grease (GB/T 6402-2024 §4.3) | Water, oil, or glycerin (ASTM A388 §5.3) | Similar | 直接互认 (Direct mutual recognition) | LOW |
Pressure Equipment-Specific Testing
Chinese standard: NB/T 47013.3-2015: 承压设备无损检测 第3部分：超声检测 (Nondestructive testing of pressure equipment—Part 3: Ultrasonic testing)
International equivalent: ASTM A388/A388M-19: 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 |
|---|---|---|---|---|---|
| Calibration method | Reference blocks with flat-bottom holes (NB/T 47013.3-2015 §5.2) | DAC with calibration block (ASTM A388 §6.2) | Different methodology | 不可互认 (Not mutually recognised) | HIGH |
| Acceptance levels | Quality grades I–IV based on equivalent flaw size (NB/T 47013.3-2015 §7.1) | Reference notch/notch sizes (ASTM A388 §9.1) | Different classification system | 不可互认 (Not mutually recognised) | HIGH |
| Scanning pattern | 100% scanning with 10% overlap (NB/T 47013.3-2015 §6.1) | 100% scanning with 15% overlap (ASTM A388 §7.1) | Different overlap requirement | 附加测试后互认 (Mutual recognition after additional testing) | MEDIUM |
KEY DIFFERENCES SUMMARY
- Calibration method: GB/T 6402 uses DGS or flat-bottom hole reference blocks; ASTM A388 uses DAC with calibration block. → 不可互认 (Not mutually recognised). Impact: HIGH.
- Acceptance criteria: Chinese standards use quality grades based on equivalent flaw size; ASTM uses reference notch sizes. → 不可互认 (Not mutually recognised). Impact: HIGH.
- Scanning overlap: NB/T 47013.3 requires 10% overlap; ASTM A388 requires 15% overlap. → 附加测试后互认 (Mutual recognition after additional testing). Impact: MEDIUM.
- Frequency range: Chinese standard 2–5 MHz; ASTM 1–5 MHz. Minor difference. → 附加测试后互认 (Mutual recognition after additional testing). Impact: MEDIUM.
REGULATORY LINKAGE TABLE (法规联动)
| Compliance Scenario | Chinese Regulatory Basis | International Regulatory Basis |
|---|---|---|
| Mandatory product certification | CCC (for pressure equipment) or type approval per TSG 21-2016 | UL Listing, CE marking (PED 2014/68/EU), ASME BPVC |
| Engineering acceptance inspection | NB/T 47013.3-2015 for pressure equipment; GB/T 6402-2024 for general forgings | ASME Section V Article 5 (ultrasonic examination) |
| Import/export compliance | CCIB commodity inspection for pressure equipment | Destination country customs standard (e.g., ASTM, EN) |
| Designer/engineer obligation | GB 150-2011 (Pressure vessels) §10.2 references NB/T 47013 | ASME BPVC Section VIII Div. 1 references ASME Section V |
AUDIT FLAG RESOLUTION
- ✅ RESOLVED: GB/T 6402-2024 is current (2024 edition), not 2008. Correct title: 钢锻件超声检测方法 (Steel forgings—Method for ultrasonic testing).
- ✅ RESOLVED: GB/T 17107-2025 is current (2025 edition), not 1997. Correct title: 锻件用结构钢棒 (Structural steel bars for forgings).
- ✅ FALSE POSITIVE (domain flag): NB/T 47013.3-2015 is a TIER 2 test method standard, correctly used for ultrasonic testing comparison with ASTM A388. No misapplication.
- ✅ RESOLVED: ASTM A388 is a TIER 2 test method standard, not a product standard. Comparison with Chinese TIER 2 standards is valid.
PROCUREMENT VERDICT
- Do NOT assume direct equivalence between ASTM A388 and GB/T 6402-2024 or NB/T 47013.3-2015.
- Specify which standard (ASTM or Chinese) will govern acceptance in the purchase contract.
- If Chinese standard is required, confirm whether GB/T 6402-2024 or NB/T 47013.3-2015 applies based on product type (general vs pressure equipment).
- Require the supplier to provide calibration records and acceptance criteria documentation.
- Consider third-party testing per the destination standard to avoid rejection.
- Verify the edition year of the Chinese standard (GB/T 6402-2024 is current; NB/T 47013.3-2015 is current).
REFERENCE DOCUMENT CHECKLIST (配套调阅清单)
- GB/T 6402-2024 §5.2 — Calibration method (DGS or reference blocks)
- GB/T 6402-2024 §7.1 — Acceptance grades (1–5)
- NB/T 47013.3-2015 §5.2 — Calibration method (flat-bottom hole blocks)
- NB/T 47013.3-2015 §7.1 — Acceptance grades (I–IV)
- ASTM A388/A388M-19 §6.2 — Calibration method (DAC)
- ASTM A388/A388M-19 §9.1 — Acceptance criteria (notch sizes)
FIELD INSPECTION CHECKLIST
- Verify calibration block type (DGS vs DAC vs flat-bottom hole) matches specified standard.
- Check scanning overlap percentage (10% for NB/T 47013.3; 15% for ASTM A388).
- Confirm frequency range of transducer (2–5 MHz for GB/T 6402; 1–5 MHz for ASTM).
- Review acceptance grade/level documentation from supplier.
- Witness a test run to confirm procedure compliance.
CONFIDENCE RATING
🟡 MEDIUM CONFIDENCE (auto-downgraded from HIGH: 1 standard number(s) failed local DB validation)
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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