GB/T 6402-2024 PDF English
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| GB/T 6402-2024 | English | 440 |
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Method for ultrasonic testing of steel forgings
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| GB/T 6402-2008 | English | 85 |
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Steel forgings -- Method for ultrasonic testing
| Valid |
| GB/T 6402-1991 | English | 359 |
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Steel forgings--Method for ultrasonic examination
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GB/T 6402-2024: Method for ultrasonic testing of steel forgings---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT6402-2024
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040.20
CCS H 26
Replacing GB/T 6402-2008, GB/T 1786-2008
Method for Ultrasonic Testing of Steel Forgings
Issued on. SEPTEMBER 29, 2024
Implemented on. APRIL 1, 2025
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative References... 5
3 Terms and Definitions... 5
4 Terms of Agreement... 6
5 General Requirements... 6
6 Testing Equipment... 8
7 Comparison Test Block... 8
8 Testing... 9
9 Classification... 14
10 Assessment of Discontinuity... 17
11 Recording Levels and Acceptance Criteria... 17
12 Testing Report... 20
Appendix A (informative) Maximum Testable Depth of Circumferential Shear Wave
Scanning... 22
Appendix B (informative) Method of Sensitivity Adjustment Using Workpiece Bottom
Wave... 24
Appendix C (normative) Ultrasonic Testing of Forging Tortillas... 26
Appendix D (informative) Correspondence between DAC (%) Amplitude and dB Value
... 29
1 Scope
This document specifies the general requirements, testing equipment, comparison test block,
testing implementation, classification, assessment, recording levels, acceptance standards and
testing report of ultrasonic testing of steel forgings.
This document is applicable to ultrasonic pulse reflection testing of ferritic, martensitic and
ferritic-martensite steel forgings, austenitic and austenitic-ferritic stainless-steel forgings. It
also applies to the ultrasonic testing of forged high-temperature alloys and alloy steel tortillas.
Steel forgings with other structures may take this as a reference.
2 Normative References
The content of the following documents constitutes indispensable clauses of this document
through normative references in the text. In terms of references with a specified date, only
versions with a specified date are applicable to this document. In terms of references without a
specified date, the latest version (including all the modifications) is applicable to this document.
GB/T 9445 Non-destructive Testing - Qualification and Certification of NDT Personnel
GB/T 12604.1 Non-destructive Testing - Terminology - Ultrasonic Testing
GB/T 20737 Non-destructive Testing - General Terms and Definitions
GB/T 23905 Non-destructive Testing - Blocks for Ultrasonic Testing
GB/T 27664.1 Non-destructive Testing - Characterization and Verification of Ultrasonic Test
Equipment - Part 1.Instruments
GB/T 27664.2 Non-destructive Testing - Characterization and Verification of Ultrasonic Test
Equipment - Part 2.Probes
GB/T 39239 Non-destructive Testing - Ultrasonic Testing - Characterization and Sizing of
Discontinuities
GB/T 39242 Non-destructive Testing - Ultrasonic Testing - Sensitivity and Range Setting
3 Terms and Definitions
The terms and definitions defined in GB/T 12604.1 and GB/T 20737 are applicable to this document.
4 Terms of Agreement
When ordering, the supply-side and the demand-side shall reach a consensus on one or more of
the following items related to ultrasonic testing (if the demand-side does not specify, then, the
testing method shall be chosen by the supply-side).
---timing of testing (see 5.3);
---whether it is necessary to submit written testing procedures approved by the demand-
side (see 5.4);
---whether near-surface testing is required (see 6.2.5);
---other testing requirements for Category 4 complexly shaped forgings or complex parts
of forgings (see 8.2.3);
---sensitivity setting method (see 8.3);
---whether it is required to use angle probe for testing (see 8.3.3);
---the range to be tested, and whether to perform grid scanning or 100% scanning (see
8.6.1);
5 General Requirements
5.1 Personnel Qualifications
Personnel engaged in ultrasonic testing in accordance with this document shall comply with the
requirements of GB/T 9445 or other corresponding documents and obtain an ultrasonic testing
qualification certificate.
5.2 Coupling Agent
During sensitivity setting and review, scanning and discontinuity assessment, the same type of
coupling agent shall be used. After the testing is completed, if the coupling agent on the surface
of the workpiece under test has an adverse effect on the subsequent production, inspection or
the integrity of the finished product, then, it shall be removed.
5.3 Timing of Testing
Unless otherwise specified in the product standard, ultrasonic testing shall be performed after
final heat treatment. Forgings that cannot be tested after the final heat treatment shall be tested
at a certain suitable stage before that. For cylindrical and rectangular forgings that require
drilling, ultrasonic testing should be performed before drilling.
5.4 Testing Procedures
5.4.1 Ultrasonic testing shall be performed in accordance with testing procedures. When it is
specified by a product standard, the testing procedures shall be submitted to the demand-side
for approval before testing.
5.4.2 The testing procedures shall be one of the following.
5.4.3 The testing procedures shall at least include the following content.
6 Testing Equipment
6.1 Ultrasonic Testing Instrument
The ultrasonic testing instrument shall comply with the requirements of GB/T 27664.1.
6.2 Probes
6.2.1 Conventional straight probe and angle probe shall comply with the requirements of GB/T
27664.2.If further information is required, other probes may be used for supplementary testing,
but the supplementary probes cannot be used for the initial discontinuity testing.
6.2.2 The nominal frequency of the probes is between 1 MHz ~ 10 MHz.
6.2.3 The nominal diameter of the transducer shall be between 10 mm ~ 40 mm.
6.2.4 The refraction angle of the angle probe shall be between 35 ~ 70. The effective area of
the nominal transducer shall be between 20 mm2 ~ 625 mm2.
6.2.5 The near-surface testing may use double crystal probe.
6.2.6 The shape grinding method of the probe contact surface shall comply with GB/T 39242.
6.3 Combined Equipment Performance Inspection
The performance of combined equipment (ultrasonic testing instrument and probe) shall be
regularly inspected.
7 Comparison Test Block
7.1 The production and inspection of comparison test block shall comply with the requirements
of GB/T 23905.
7.2 When adopting the Distance Amplitude Curve (DAC) technique for sensitivity setting and
the amplitude of the reflector is referenced to determine the size of the discontinuity,
comparison test block shall be provided. The surface condition of the comparison test block
shall be the same or similar to that of the workpiece under test. Unless otherwise specified, the
comparison test block shall be able to cover at least 3 artificial reflectors throughout the entire
testing depth range.
7.3 The comparison test block can be made of one of the following materials.
7.4 The size of the artificial reflector of the comparison test block shall comply with the
requirements of the corresponding quality grade.
8 Testing
8.1 Surface Condition
8.1.1 The scanned surface shall be free of defects, such as. scale, dirt, paint and pits that may
affect coupling. If the above situation occurs, appropriate methods shall be used to remove or
machine them, so as to satisfy the testing requirements.
8.1.2 When forgings are delivered in forged surface condition, if they can satisfy the specified
quality grade inspection requirements, they can be directly tested.
NOTE. when it is difficult to conduct comprehensive testing of the forging surface, the method of
shot blasting, sandblasting or surface grinding can be used for surface treatment, so as to
ensure acoustic coupling. Usually, it merely applies to quality grade 1.
8.2 Testing Range
8.2.1 Classification of forgings
This document divides forgings into 4 categories in accordance with shape and production
method, see Table 1.Categories 1, 2 and 3 are simply shaped forgings, and Category 4 is
complexly shaped forgings or complex parts of forgings.
8.2.2 Simply shaped forgings
8.2.2.1 Table 2 provides the testing range of Categories 1, 2 and 3 forgings when scanning with
8.2.3 Complexly shaped forgings
For complexly shaped forgings or complex parts of forgings (Category 4) and small-diameter
forgings, the supply-side and the demand-side shall negotiate the scanning requirements, which
shall at least include. probe angle, scanning direction and scanning range (grid or 100%).
8.3 Testing Sensitivity
8.3.1 General requirements
The testing sensitivity shall ensure the testing of the minimum discontinuity required by the
recording level in the specified quality grade. The methods described in 8.3.2 and 8.3.3 shall be
used. The corresponding probe shall be used to set the testing sensitivity, and the setting
procedures shall comply with the requirements of GB/T 39242.
8.3.2 Straight probe
Testing sensitivity can be determined using one of the following methods.
8.3.3 Angle probe
Testing sensitivity can be determined using one of the following methods.
8.3.4 Sensitivity in repeated testing
If repeated testing is performed, the method of setting sensitivity is the same as 8.3.2 and 8.3.3.
8.4 Transmission Corrections
8.4.1 General requirements
When the comparison test block is used to assess indications, the ultrasonic material attenuation
and surface loss generated in the test block shall be consistent with that of the workpiece under
test. Otherwise, transmission corrections shall be adopted to compensate for material
attenuation and surface loss differences. When it is known that the attenuation is negligible, no
correction is required.
8.4.3 Angle probe
The comparison technology specified in GB/T 39242 can also be used for transmission
correction.
8.5 Pulse Repetition Frequency
If the pulse repetition frequency is adjustable, it should be high enough to ensure adequate
screen brightness and testing of all relevant indications. When testing materials with long sound
path and low attenuation, on the premise that no phantom waves are generated, the pulse
repetition frequency shall be as high as possible.
8.6 Scanning
8.6.1 General requirements
The minimum scanning range required shall depend on the category of forgings, and whether
grid scanning or 100% scanning is used shall be specified in the contract.
8.6.2 100% scanning
The overlap between two adjacent probe scan traces is at least 10% of the transducer size.
9 Classification
9.1 Classification of Indications
9.1.1 Type I diagram
9.1.1.1 As the probe moves, Type A display shows a single clear indication that smoothly rises
to the maximum amplitude, and then, smoothly drops to 0 (see Figure 1). In Type A display, the
X-axis is the time or sound path of the A-scan display at the fixed probe position. In the dynamic
waveform diagram, the X-axis is the probe scanning displacement corresponding to the
amplitude envelope curve, and the Y-axis is the echo amplitude.
9.1.1.2 Figure 1 is a dynamic echogram of the sound beam profile drawn with a transverse hole,
9.1.2 Type II diagram
As the probe moves, Type A display shows a single clear indication that smoothly rises to the
maximum amplitude, which is sustained with or without amplitude change, and then, smoothly
falls to 0 (see Figure 2). In Type A display, the X-axis is the time or sound path of the A-scan
display at the fixed probe position.
9.2 Classification of Discontinuities
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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