Steel forgings ultrasonic inspection instructions
I. Scope and purpose
The implementation of the rules provides for the ultrasonic inspection of steel forgings, the method of comparison test blocks, inspection instruments and equipment, inspection conditions and sensitivity adjustment, defect assessment, quality classification, inspection reports. These rules apply to the pulse reflection ultrasonic inspection method of thickness or diameter greater than 100mm of carbon steel and low alloy steel general forgings ultrasonic inspection. The implementation of the rules include the scope of application and purpose, test basis, test principle, test conditions, test items and calculation of content, test procedures, inspection methods and precautions.
Purpose: through the ultrasonic inspection of steel forgings, analyze the degree of damage to the forgings in the process of use, according to the type of defects and the size of the equivalent size, determine the quality level of forgings.
Second, the test basis
GB/T6402-1991 "ultrasonic inspection of steel forgings"
Third, the principle of the test
Generally in the homogeneous material, the presence of defects will cause discontinuity in the material, this discontinuity is often caused by the acoustic impedance of the inconsistency of the reflection theorem that we know that the ultrasonic wave in two different acoustic impedance. Ultrasonic waves in two different acoustic impedance of the media interface will be reflected, reflected back to the size of the energy with the interface on both sides of the media acoustic impedance differences and interface orientation, size. When the bottom surface of the steel forging is smooth and parallel to the conditions of the detection surface, the detection graph only indicates the emission pulse T and the bottom echo B two signals, as shown in Figure 1 (a).
If there is a defect in the steel forging, due to the existence of this defect, caused by the defect and the steel material between the formation of a different medium between the interface, the acoustic impedance between the interface is different, when the emitted ultrasonic wave encountered the interface, it will be reflected back to the reflected energy is received by the probe, in the detection graph, the bottom echo before the echo of defects F, as shown in Figure 1(b). As shown in Fig. 1(b), a certain position of the horizontal coordinate in the graph will show a waveform of the reflected wave, and this position of the horizontal coordinate is the depth of the defect in the detected material. The height and shape of this reflected wave varies with different defects and reflects the nature of the defect.
Four, inspection conditions
Steel forgings ultrasonic inspection can be carried out both on-site inspection, can also be carried out in the laboratory, the requirements are as follows:
1) forgings should be inspected in the heat treatment and drilling, slotting, and other processing before the general;
2) contact method of inspection, the surface roughness of the forging Ra value should be less than 3.2um
2) the contact method of inspection, the forging surface roughness Ra value should be less than 3.2um, the liquid immersion method of inspection, the surface should be flat, no influence on the acoustic coupling of the oxidized skin, spoils and other attachments, and to meet the requirements of the inspection;
3) in the probe and the detection of the surface, the use of appropriate coupling agent;
4) according to the forging processing technology, select the most easy to find defects in the detection of the surface, generally should be from the two mutually perpendicular to the direction of the inspection, as shown in Figure 2.
5) transverse wave inspection, generally should be done from the outer surface of the clockwise and counterclockwise direction of the full inspection;
6) sweeping method of manual sweeping and automatic sweeping, the probe in the detection of the surface of the sweeping spacing should be ensured that there is a 15% acoustic beam coverage;
7) sweeping speed, that is, the probe relative to the movement of forging speed should be less than 150mm/s. The probe can be used to detect defects on the surface of the forging, but it can be used to detect defects on the surface of the forging.
8) The test equipment used should be accompanied by a report proving that its accuracy meets the requirements of this standard and calibration report, and can only be used within the calibration cycle, the list of equipment used in Table 1.
Serial No.
Name
Model
Performance indicators
Certificate of inspection No.
1
Ultrasonic Flaw Detector
TUD310
Detection Frequency Range: 1~5MHz
Horizontal Linear Error: ≦1%
Vertical Linear Error: ≦4%
Lsau2007-0445
2
Steel Tape Measure
0-5m
1mm
01GC20070252
3
Steel Straightedge
0-300mm
1mm
01GC20070256
4
Temperature and Humidity Meter
TES-1360<
Correction-0.3
02RC20070073
Inspection Items and Calculations
1. Recording and Evaluation of Defects
2. Determination and Calculation of Decay Coefficients
3. Evaluation of Quality Level
VI. Inspection Procedures
The inspection procedures are shown in Figure 3.
VII. Inspection Methods
1. Connection and Adjustment of Instrument
1) Connection of Instrument
Firstly, prepare the workpiece to be tested, and then insert the plug of the probe cable into the socket above the main unit, screw the plug tightly, and connect a suitable probe at the probe connector BNC. Note that when using the single probe method, both connector sockets are equally suitable (internal parallel connection), and when using the connection of a Twin Crystal (TR) probe (one wafer transmitting, one wafer receiving) or two probes (one transmitting, one receiving), take care to connect the transmitting probe to the left socket and the receiving probe to the right socket.
Press the key after connecting the instrument, the instrument emits a short "beep beep" sound, release the key finger, the instrument is automatically turned on;
2) Basic instrument settings
After the instrument is turned on, the first according to the needs of the actual test work to set up a good instrument scanning mode, display range, material, speed of sound, probe mode, gate and other parameters. Speed of sound, probe mode, gate width, gate start, gate height and other basic parameters.