GB/T 4162-2022Method for ultrasonic testing of forged and rolled steel bars (English PDF)

4.1 Personnel qualifications

Personnel, who are engaged in ultrasonic testing of steel bars, shall participate in the training, according to the requirements of GB/T 9445 or corresponding documents, meanwhile obtain the ultrasonic testing qualification certificate. Anyone who issues a test report shall obtain a level 2 or above ultrasonic testing qualification certificate.

4.2 Couplant

4.2.1 The liquid immersion technique usually uses water as a couplant; however, oil can also be used. The couplant shall be free of air bubbles or foreign substances, that affect ultrasonic testing. A suitable rust inhibitor can be added to the couplant, to prevent corrosion of the steel bar.

4.2.2 Couplant, such as oil, grease, water, water-soluble gel should be used, for the contact technology. The viscosity and surface wettability of the couplant shall be sufficient, to ensure that the ultrasonic energy is well transmitted to the steel bar.

5.1 Ultrasonic detector

5.1.1 Performance test methods and requirements

The performance of the ultrasonic detector is tested, according to the method of JB/T 10061 or JJG 746.Its indicators shall meet the following requirements.

5.1.2 Alarms

Optical and/or audible alarms should be used. The triggering of the alarm shall be controlled, by adjusting the amplitude of the ultrasonic signal, which is received on the time baseline; the alarm threshold level is adjustable.

5.2 Probes

5.2.1 The frequency of the probe shall be able to meet the requirements of the ability to penetrate the steel bar to be inspected AND the resolution. It should be 2 MHz ~ 10 MHz. The diameter (side length) of the probe chip should not be greater than 28 mm. The liquid immersion probe should adopt the focusing method.

5.2.2 When the liquid immersion method is used for detection, the angle controller and mechanical control device of the probe shall be easy to adjust.

5.2.3 The parameters of the probe should be tested, according to the methods of GB/T 18694 and GB/T 18852.

5.3 Immersion tank (box) and probe regulator

5.3.1 The size of the liquid immersion tank (box), which is used for liquid immersion testing, shall ensure that the tested parts can be immersed.

5.3.2 The probe regulator shall provide adjustable angle and water layer, in two mutually perpendicular planes; it shall ensure that the probe angle and water layer are stable and reliable, during detection.

8.1 Testing method

In addition to the provisions of the contract or related documents between the supplier and the buyer, the testing method and technology of the steel bar to be tested shall be selected by the manufacturer. If shear wave testing is required, it shall be indicated in the contract or related documents.

8.2 Testing steps

8.2.1 Check the heat number, forging (rolling) number, quantity, etc. of the steel bars to be tested; understand the relevant technical requirements.

8.2.2 The surface of the steel bar to be tested shall be free of defects, such as oxide scale, dirt, paint and pits, that affect the coupling; if any, it shall be removed by pickling, grinding or machining.

8.2.3 Scanning shall be carried out 100% of the surface of the steel bar. When the signal- to-noise ratio cannot meet the requirements, it should use a distance-amplitude correction curve (DAC) or a time-gain correction curve (TCG), which can be detected in zones.

8.2.4 During the longitudinal wave testing by the liquid immersion method, the water path shall be adjusted, so that the second interface wave from the tested steel bar does not appear, before the first bottom wave of the steel bar. During the testing, it shall adjust the perpendicularity between the probe and the workpiece, to maximize the reflected signal at the interface. During the sensitivity setting, scanning, evaluation, the difference of the water path shall not exceed ±3 mm.

8.2.6 During shear wave testing, the probe shall generate shear waves of 35° ~ 70°, in the workpiece. The echoes from each reference reflector, on the comparative test block, shall not be lower than 80% of the full amplitude of the phosphor screen.

8.2.7 During automatic scanning, the setting of the gate width shall meet the requirements of the detection range.

8.2.8 The alarm level shall be set, according to the echo amplitude of the flat-bottom hole size of multiple reflectors, which have the corresponding quality level. The echo amplitude of the flat-bottom hole size of a single reflector shall be set for levels C and D.

8.2.9 The scanning spacing shall not exceed 80% of the effective sound beam width of the probe. The effective sound beam width should be determined by the -6 dB method, which is performed by the minimum value, as measured on the reference reflector, within the range of the detected metal sound path.

8.2.10 During manual scanning, the scanning speed should not exceed 150 mm/s.

During automatic scanning, when the scanning speed is the maximum, the echoes of the reference reflector, within the detection depth range in the comparative test block, can be found.

8.2.11 The sensitivity of the detection system shall be reviewed, when the following conditions are found.

8.2.12 When it is found that the scanning sensitivity is abnormal, within the detection range, all steel bars tested since the last review shall be re-inspected, OR all recorded signals shall be re-evaluated. If it can be proved that the detection system is reproducible, it may extend the sensitivity review interval of 8.2.11 c) and 8.2.11 d).

9.1 Recording of reflected signal

According to the highest sensitivity, which is specified by the quality level, during the scanning process, the reflected signal, which is greater than or equal to this sensitivity level, shall be recorded. The recording method is a coordinate diagram or a C-scan diagram, to indicate the position and size of the reflected signal.

9.2 Evaluation of back wave loss

Use direct wave to measure the bottom wave, at a lower gain; compare it with the bottom wave, in the normal position. If the bottom wave loses more than 50% AND is accompanied by an increase or decrease of the noise signal (at least twice the normal background noise), which is not due to surface state or non-parallelism, it is unqualified.

9.3 Evaluation of noise level

Noise levels above the alarm trigger level are considered unacceptable.

Note: When the tested titanium alloy bar is used as a reference, the alarm level slightly exceeds the noise level, BUT does not exceed 70% of the detection sensitivity level.

9.4 Evaluation of defects

9.4.1 Longitudinal wave testing

9.4.1.3 Elongated defects

The length of the elongated defect shall be evaluated, according to the following methods. If the length exceeds the provisions in Table 3, it shall be regarded as unqualified.

9.4.2 Shear wave testing

When the shear wave testing of defects is performed on the steel bar, the test block used for evaluation shall be as shown in Figure 2; the evaluation method shall meet the requirements of 9.4.1.The relationship, between the transverse hole and the flat-bottom hole, is as shown in Table 4.