GB/T 2970-2026 Method for ultrasonic testing of thick steel plates
1 Scope
This document specifies the general requirements, reference specimens, testing instruments and equipment, testing conditions and methods, defect measurement and evaluation, quality grades of steel plates, and test reports for ultrasonic testing of thick steel plates.
This document applies to the piezoelectric and electromagnetic acoustic manual and automatic testing of steel plates for pressure parts, bridges, construction, shipbuilding, steel structures, pipelines and other applications, with a thickness of not less than 5 mm.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 8651 Flaw detection method by the ultrasonic plate wave for metal plates
GB/T 9445 Non-destructive testing - Qualification and certification of personnels
GB/T 11259 Non-destructive testing - Practice for fabrication and control of steel reference blocks used in ultrasonic testing
GB/T 12604.1 Non-destructive testing - Terminology - Ultrasonic testing
GB/T 27664.1 Non-destructive Testing - Characterization and Verification of Ultrasonic Test Equipment - Part 1: Instruments
JJG 746 Ultrasonic flaw detectors
3 Terms and definitions
For the purposes of this document, the terms and definitions given in JB/T 12604.1 and the following apply.
3.1
piezoelectric ultrasonic testing
ultrasonic testing in which ultrasonic waves are generated and received by means of the piezoelectric effect
3.2
electromagnetic ultrasonic testing
ultrasonic testing in which electromagnetic acoustic transducers (EMAT) are used as the core devices for ultrasonic wave excitation and reception
3.3
reference plate
steel plate with acoustic characteristics similar to those of the steel plate to be tested, containing reference reflectors, used to confirm the detectability of the testing system
4 General requirements
4.1 The surface of the steel plate to be tested shall be smooth, flat, and of uniform thickness, free from droplets, oil, corrosion and other contaminants that may affect the testing.
4.2 The internal structure of the steel plate to be tested shall not produce interfering echoes that affect the testing.
4.3 The testing site shall be free from strong light, strong magnetic fields, strong vibration, corrosive gases, heavy dust, and other factors that may affect the stability of the ultrasonic testing instrument or the reliable observation of the testing personnel.
4.4 Personnel engaged in ultrasonic testing of steel plates shall be trained and qualified in accordance with GB/T 9445 or the corresponding standards. Testing personnel shall be familiar with the steel plate manufacturing process, equipment performance and standards, and shall be authorised by the employer.
4.5 Piezoelectric ultrasonic or electromagnetic acoustic testing shall be used, and the scanning shall be manual or automatic. The ultrasonic wave modes used shall be normal‑incidence longitudinal waves, transverse waves, and plate waves. When oblique‑incidence transverse waves and plate waves are used as a supplement to normal‑incidence testing, this shall be agreed upon between the supplier and the purchaser at the time of ordering.
4.6 The couplant used for the actual steel plate testing shall be the same as that used for the calibration of the testing equipment. The couplant may be water, oil, or other media.
4.7 When the temperature of the steel plate is higher than 50 °C, process verification shall be carried out. When electromagnetic acoustic testing is used, the temperature of the steel plate to be tested shall be lower than the Curie temperature of the material.
5 Reference specimens
5.1 The manufacture of reference specimens shall meet the requirements of GB/T 11259. The material and acoustic properties of the reference specimens shall be identical or similar to those of the steel plate to be tested (the difference in acoustic attenuation shall be within ± 25 %), and its interior shall be free from defects that may affect the testing.
5.2 When testing steel plates with a thickness not greater than 20 mm using a piezoelectric ultrasonic dual‑element straight beam probe, the reference specimen shown in Figure 1 shall be used. The surface roughness of the reference specimen shall not exceed 3.2 μm. In case of electromagnetic acoustic testing for steel plates with a thickness not greater than 20 m, the reference specimen shall be designed and machined with a certain number of flat‑bottomed hole defects of 5 mm diameter and a hole depth of half the plate thickness. By agreement between the relevant parties, other types of reference specimens and equivalent reflectors may also be used.
Note: The type of reference specimen for steel plates with a thickness not greater than 20 mm is CB Type I.
In mm
Figure 1 Reference specimen for normal‑incidence testing of steel plates with thickness not greater than 20 mm
5.3 For the testing of steel plates with a thickness greater than 20 mm, the schematic diagram of the reference specimen is shown in Figure 2. The surface roughness of the reference specimen shall not exceed 6.3 μm. The reference specimen shall have at least 3 flat‑bottomed holes of 5 mm diameter at different depths. The distance from the testing surface to the flat‑bottomed hole (S) shall not exceed 15 % of the plate thickness or 15 mm, whichever is smaller.
Note: The type of reference specimen for steel plates with a thickness greater than 20 mm is CB Type II.
In mm
Key
1 - Testing surface;
2 - Flat‑bottomed hole;
s - Distance from the testing surface to flat‑bottomed hole;
b - Width of reference specimen.
Figure 2 Schematic diagram of reference specimen for normal‑incidence testing of steel plates with thickness greater than 20 mm
5.4 When using piezoelectric or electromagnetic acoustic automated testing methods, the long side of the reference plate shall be parallel to the rolling direction, and the end faces shall be straight. The schematic diagram of the reference plate (top view) is shown in Figure 3. The artificial flat‑bottomed slots shall be buried at a depth of half the plate thickness; the defect height shall not be greater than 0.3 mm, and its length and width shall be 50 mm and 10 mm respectively. The surface‑milled slot shall have a depth of 3 mm and a length and width of 50 mm and 10 mm respectively. The rectangular groove shall have a width of 3 mm and a depth machined according to requirements. Depending on the testing requirements, an appropriate number of flat‑bottomed holes of 5 mm diameter or other diameters may be added at suitable positions. The distance from the testing surface to the flat‑bottomed hole shall comply with the requirements of 5.3.
In mm
Key
1, 2 - Artificial flat‑bottomed slot;
3 - Surface‑milled slot;
4 - Rectangular slot.
Note: The horizontal direction is the rolling direction of the steel plate.
Figure 3 Schematic diagram of reference plate for automated ultrasonic testing (top view)
5.5 The reference specimen for oblique‑incidence testing shall comply with the requirements of Annex A.
Contents
Foreword Ⅲ
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Reference specimens
6 Testing instruments and equipment
7 Testing conditions and methods
8 Defect measurement and evaluation
9 Quality grade of steel plates
10 Test report
Annex A (Normative) Test method for transverse wave oblique incidence inspection of steel plates
Annex B (Normative) Performance requirements for dual‑element straight beam probes
GB/T 2970-2026 Method for ultrasonic testing of thick steel plates
1 Scope
This document specifies the general requirements, reference specimens, testing instruments and equipment, testing conditions and methods, defect measurement and evaluation, quality grades of steel plates, and test reports for ultrasonic testing of thick steel plates.
This document applies to the piezoelectric and electromagnetic acoustic manual and automatic testing of steel plates for pressure parts, bridges, construction, shipbuilding, steel structures, pipelines and other applications, with a thickness of not less than 5 mm.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 8651 Flaw detection method by the ultrasonic plate wave for metal plates
GB/T 9445 Non-destructive testing - Qualification and certification of personnels
GB/T 11259 Non-destructive testing - Practice for fabrication and control of steel reference blocks used in ultrasonic testing
GB/T 12604.1 Non-destructive testing - Terminology - Ultrasonic testing
GB/T 27664.1 Non-destructive Testing - Characterization and Verification of Ultrasonic Test Equipment - Part 1: Instruments
JJG 746 Ultrasonic flaw detectors
3 Terms and definitions
For the purposes of this document, the terms and definitions given in JB/T 12604.1 and the following apply.
3.1
piezoelectric ultrasonic testing
ultrasonic testing in which ultrasonic waves are generated and received by means of the piezoelectric effect
3.2
electromagnetic ultrasonic testing
ultrasonic testing in which electromagnetic acoustic transducers (EMAT) are used as the core devices for ultrasonic wave excitation and reception
3.3
reference plate
steel plate with acoustic characteristics similar to those of the steel plate to be tested, containing reference reflectors, used to confirm the detectability of the testing system
4 General requirements
4.1 The surface of the steel plate to be tested shall be smooth, flat, and of uniform thickness, free from droplets, oil, corrosion and other contaminants that may affect the testing.
4.2 The internal structure of the steel plate to be tested shall not produce interfering echoes that affect the testing.
4.3 The testing site shall be free from strong light, strong magnetic fields, strong vibration, corrosive gases, heavy dust, and other factors that may affect the stability of the ultrasonic testing instrument or the reliable observation of the testing personnel.
4.4 Personnel engaged in ultrasonic testing of steel plates shall be trained and qualified in accordance with GB/T 9445 or the corresponding standards. Testing personnel shall be familiar with the steel plate manufacturing process, equipment performance and standards, and shall be authorised by the employer.
4.5 Piezoelectric ultrasonic or electromagnetic acoustic testing shall be used, and the scanning shall be manual or automatic. The ultrasonic wave modes used shall be normal‑incidence longitudinal waves, transverse waves, and plate waves. When oblique‑incidence transverse waves and plate waves are used as a supplement to normal‑incidence testing, this shall be agreed upon between the supplier and the purchaser at the time of ordering.
4.6 The couplant used for the actual steel plate testing shall be the same as that used for the calibration of the testing equipment. The couplant may be water, oil, or other media.
4.7 When the temperature of the steel plate is higher than 50 °C, process verification shall be carried out. When electromagnetic acoustic testing is used, the temperature of the steel plate to be tested shall be lower than the Curie temperature of the material.
5 Reference specimens
5.1 The manufacture of reference specimens shall meet the requirements of GB/T 11259. The material and acoustic properties of the reference specimens shall be identical or similar to those of the steel plate to be tested (the difference in acoustic attenuation shall be within ± 25 %), and its interior shall be free from defects that may affect the testing.
5.2 When testing steel plates with a thickness not greater than 20 mm using a piezoelectric ultrasonic dual‑element straight beam probe, the reference specimen shown in Figure 1 shall be used. The surface roughness of the reference specimen shall not exceed 3.2 μm. In case of electromagnetic acoustic testing for steel plates with a thickness not greater than 20 m, the reference specimen shall be designed and machined with a certain number of flat‑bottomed hole defects of 5 mm diameter and a hole depth of half the plate thickness. By agreement between the relevant parties, other types of reference specimens and equivalent reflectors may also be used.
Note: The type of reference specimen for steel plates with a thickness not greater than 20 mm is CB Type I.
In mm
Figure 1 Reference specimen for normal‑incidence testing of steel plates with thickness not greater than 20 mm
5.3 For the testing of steel plates with a thickness greater than 20 mm, the schematic diagram of the reference specimen is shown in Figure 2. The surface roughness of the reference specimen shall not exceed 6.3 μm. The reference specimen shall have at least 3 flat‑bottomed holes of 5 mm diameter at different depths. The distance from the testing surface to the flat‑bottomed hole (S) shall not exceed 15 % of the plate thickness or 15 mm, whichever is smaller.
Note: The type of reference specimen for steel plates with a thickness greater than 20 mm is CB Type II.
In mm
Key
1 - Testing surface;
2 - Flat‑bottomed hole;
s - Distance from the testing surface to flat‑bottomed hole;
b - Width of reference specimen.
Figure 2 Schematic diagram of reference specimen for normal‑incidence testing of steel plates with thickness greater than 20 mm
5.4 When using piezoelectric or electromagnetic acoustic automated testing methods, the long side of the reference plate shall be parallel to the rolling direction, and the end faces shall be straight. The schematic diagram of the reference plate (top view) is shown in Figure 3. The artificial flat‑bottomed slots shall be buried at a depth of half the plate thickness; the defect height shall not be greater than 0.3 mm, and its length and width shall be 50 mm and 10 mm respectively. The surface‑milled slot shall have a depth of 3 mm and a length and width of 50 mm and 10 mm respectively. The rectangular groove shall have a width of 3 mm and a depth machined according to requirements. Depending on the testing requirements, an appropriate number of flat‑bottomed holes of 5 mm diameter or other diameters may be added at suitable positions. The distance from the testing surface to the flat‑bottomed hole shall comply with the requirements of 5.3.
In mm
Key
1, 2 - Artificial flat‑bottomed slot;
3 - Surface‑milled slot;
4 - Rectangular slot.
Note: The horizontal direction is the rolling direction of the steel plate.
Figure 3 Schematic diagram of reference plate for automated ultrasonic testing (top view)
5.5 The reference specimen for oblique‑incidence testing shall comply with the requirements of Annex A.
Contents of GB/T 2970-2026
Contents
Foreword Ⅲ
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Reference specimens
6 Testing instruments and equipment
7 Testing conditions and methods
8 Defect measurement and evaluation
9 Quality grade of steel plates
10 Test report
Annex A (Normative) Test method for transverse wave oblique incidence inspection of steel plates
Annex B (Normative) Performance requirements for dual‑element straight beam probes
