JB/T 1581-1996 Ultrasonic flaw detection method for steam turbine, turbogenerator rotor and main shaft forgings
Some standard content:
Machinery Industry Standard of the People's Republic of China
JB/T1581-1996
Ultrasonic flaw detection method for turbine, turbo-generator rotor and main shaft forgings
1996-09-03 Issued
Ministry of Machinery Industry of the People's Republic of China
Implementation on 1997-07-01
JB/T1581-1996
This standard is a revision of JB1581-85 based on the requirements of six product technical conditions and related standards, with major changes in technical content and writing rules.
These six technical conditions are: JB/T7025-93 "Technical Conditions for Steam Turbine Rotor and Main Shaft Forgings Below 25MW", JB/T1265-93 "Technical Conditions for Steam Turbine Rotor and Main Shaft Forgings of 25-200MW", JB/T702793 "Technical Conditions for Steam Turbine Rotor Forgings of 300-600MW", JB/T7026-93 "Technical Conditions for Steam Turbine Generator Rotor Forgings Below 50MW", JB/T1267-93 "Technical Conditions for Steam Turbine Generator Rotor Forgings of 50-200MW", and BT7178-93 "Technical Conditions for Steam Turbine Generator Rotor Forgings of 300-600MW".
Since the contents of the six technical conditions have changed greatly from B1265-85 "Technical Conditions for Vacuum-treated Carbon Steel and Alloy Steel Forgings for Steam Turbine Rotors and Spindle" and JB1267-85 "Technical Conditions for Vacuum-treated Forgings for Generator Rotors", this standard has also been modified accordingly to make them consistent.
Since the specific evaluation standards for ultrasonic flaw detection in the six technical conditions are different, it is impossible for this standard to stipulate a unified evaluation standard. The flaw detection results of various forgings should be evaluated according to the corresponding clauses in the technical conditions. For the integrity and convenience of use of the standard, this standard summarizes the ultrasonic flaw detection technical requirements of the six technical conditions into Appendix A of this standard. From the date of implementation, this standard will replace B1581-85 at the same time. Appendix A of this standard is the appendix of the standard.
This standard was proposed and managed by Deyang Large Castings and Forgings Research Institute. The drafting unit of this standard: China Second Heavy Machinery Group Corporation. The main drafter of this standard: Tan Zhisheng.
1 Scope
Machinery Industry Standard of the People's Republic of China
Ultrasonic flaw detection method for turbine, turbine generator rotor and main shaft forgings
JB/T 1581—1996
This standard specifies the flaw detection personnel, flaw detection equipment, flaw detection operation essentials and flaw detection result record and evaluation for ultrasonic flaw detection of turbine, turbine generator rotor and main shaft forgings. This standard is applicable to ultrasonic flaw detection of various rotors and main shaft forgings in JB/T7025, JB/T1265, JB/T7027 and JB/T7026, JB/T1267 and JBT7178. Other shaft forgings with similar working conditions can refer to this standard. This standard is applicable to ultrasonic flaw detection of the outer cylindrical surface of rotors and main shaft forgings by longitudinal wave contact method using the pulse reflection ultrasonic flaw detection principle.
2 Cited standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB9445—88
JB/T1265—93
JB/T1267—93
JB4126—85
JB/T 7025—93
JB/T7026—93
JB/T 7027—93
JB/T 7178—93
ZBY 230—84
ZBY 231—84
3Nondestructive testing personnel
General rules for technical qualification appraisal of nondestructive testing personnel Technical conditions for rotor bodies and main shaft forgings of 25~200MW steam turbines Technical conditions for rotor forgings of 50~200MW steam turbine generators Manufacturing and control of steel test blocks for ultrasonic testing Technical conditions for rotor bodies and main shaft forgings of steam turbines below 25MW Technical conditions for rotor forgings of steam turbine generators below 50MW Technical conditions for rotor forgings of 300~600MW steam turbines Technical conditions for rotor forgings of 300~600MW steam turbine generators Technical conditions for type A pulse reflection ultrasonic flaw detector Performance test method for ultrasonic flaw detection probe
3.1 Personnel engaged in forging flaw detection should have certain basic knowledge of hot working and practical experience in ultrasonic flaw detection of forgings. 3.2 Ultrasonic flaw detection of forgings should be performed by personnel who have been assessed and appraised by relevant departments and obtained corresponding qualification certificates in accordance with GB9445. The person issuing the flaw detection report must hold a qualification certificate for ultrasonic flaw detection II or above. 3.3 The flaw detector personnel should be able to correctly understand and use this standard. 4 Flaw detection equipment
4.1 Ultrasonic flaw detector
4.1.1 The A-type pulse reflection ultrasonic flaw detector should have a frequency range of at least 1 to 5MHz. Approved by the Ministry of Machinery Industry on September 3, 1996
Implementation on July 1, 1997
JB/T1581—1996Www.bzxZ.net
4.1.2 The horizontal scanning linearity of the flaw detector shall have an error of no more than 2% within the full scale range, and the vertical linearity error shall be no more than 5%. The resolution shall be no less than 20dB.
4.1.3 The combined sensitivity of the flaw detector and the probe shall have an effective sensitivity margin of at least 10cB when reaching the flaw detection sensitivity at the maximum sound range of the forging being detected.
4.1.4 Other performance indicators of the flaw detector shall comply with the corresponding provisions of ZBY230 4.2 Probe
4.2.1 The probe usually adopts a longitudinal wave probe with a nominal frequency of 25MHz, and its frequency error is ±10%. 4.2.2 The probe chip size is mainly Φ20mm, and can also be selected in the range of Φ10～Φ30mm. 4.2.3 If necessary, effective probes of other frequencies and other specifications can be used. 4.2.4 The main sound beam of the probe should have no double peaks, no deflection, and stable and reliable performance. 4.2.5 All kinds of probes should be used at the rated frequency. 4.2.6 The test of probe performance shall be carried out in accordance with the provisions of ZBY231. 4.3 Coupling agent
The coupling agent used for forging flaw detection should have good sound permeability and wettability, and should not damage the surface of the workpiece, such as engine oil, glycerin, etc. Different coupling agents have different sound permeability, so the same coupling agent should be used when calibrating the instrument and actual flaw detection. 4.4 Test blocks
According to the provisions of B4126, corresponding test blocks shall be made as needed. 5 General requirements for forgings
5.1 For rotor and spindle forgings that need to be inspected, their outer shape should be processed into a simple cylindrical shape as much as possible to avoid geometric shapes such as cones, grooves, and arc-shaped transition zones that hinder the inspection. 5.2 The surface roughness R of the inspection surface of the forging should not be greater than 63μm, and foreign matter such as paint and dirt should not adhere to it. 5.3 Ultrasonic flaw detection performed by the manufacturer as a factory quality should generally be carried out after the final heat treatment; if it is necessary to process geometric shapes such as wheel discs, grooves, cones, etc. before the final heat treatment, it is also allowed to use the last flaw detection result before this processing step as the basis for evaluating the quality of the forging.
5.4 After the final heat treatment, the flaw detection to reflect the factory quality must be carried out when the material attenuation coefficient of the forging is not greater than 4dB/m, and the flaw detection frequency is 2~2.5MHz
5.5 For the parts that have not been flaw detected before the delivery of the forging, the ordering party can make up the flaw detection after delivery, and the flaw detection results will also serve as the basis for evaluating the quality of the forging.
6 Flaw detection operation essentials
6.1 Flaw detection sensitivity adjustment
6.1.1 The flaw detection sensitivity of the rotor and spindle forgings must be able to effectively detect the smallest equivalent defects specified in the technical conditions of the forgings. In order to facilitate the search for defects, it is allowed to increase the appropriate sensitivity (such as 6dB) for the initial scan and flaw detection during the flaw detection scan; when defects are found, various measurements must be carried out at the specified sensitivity. 6.1.2 For forgings whose thickness is greater than three times the near-field size of the probe, the bottom wave adjustment method is used to adjust the detection sensitivity; only when the thickness is equal to or less than three times the near-field size of the probe, the test block adjustment method is used. 6.1.3 First, use a high sensitivity that can display the reflection of the material structure to find the defect-free reflection area in each section of the forging, and then adjust the 2
bottom wave amplitude of the area to 40%~80% of the full screen height JB/T 1581-1996
6.1.4 According to whether the forging has a center hole, the instrument gain is increased by the following formula: a) When detecting solid forgings
4dB=201g
b) When detecting forgings with a center hole
4dB=20lg
Where: 4cB-the gain decibel number to be increased; A-ultrasonic wavelength, mm;
D-the outer diameter of the detected part, mm;
d-the diameter of the center hole of the detected part, mm; Yuan-pi β.14159)
Φ-the diameter of the flat bottom hole of the flaw detection sensitivity, mm; T-the thickness of the detected part of the forging, mm.
6.2 Scan line ratio adjustment
In order to facilitate the observation of certain signal conditions after the first bottom wave, the front position of the first bottom wave should be adjusted within 80% of the full scale of the scan line.
6.3 Flaw detection scanning surface
The entire outer cylindrical surface of the forging should be scanned continuously and the entire volume of the forging should be detected as much as possible. 6.4 Flaw detection scanning requirements
6.4.1 Two flaw detection scans should be carried out on the same flaw detection surface, and the directions of the two scans should be perpendicular to each other. 6.4.2 The moving scanning speed of the probe should not exceed 150mm/s. There should be a certain overlap between two adjacent scans, and the overlapping width should not be less than 15% of the scanning width
6.4.3 During the scanning process, it is necessary to pay attention not only to observe whether there are defect signals before the bottom wave, but also to observe whether there are defect signals after the bottom wave. 6.4.4 When the bottom wave signal or other non-defect signals (such as probe reflection signals, late signals, etc.) are significantly reduced or disappear, the cause of this phenomenon should be found out in time.
6.5 Recalibration of flaw detection sensitivity
6.5.1 In addition to calibrating the sensitivity before each flaw detection, the flaw detection sensitivity must be recalibrated in the following situations: a) When there is any change in the calibrated probe, coupling agent, instrument knob, etc.; b) When the external power supply voltage fluctuates greatly or the operator suspects that the sensitivity has changed; c) When working continuously for more than 4 hours and at the end of work. 6.5.2 When the sensitivity changes and decreases by more than 2dB, the forgings detected after the last calibration should be fully re-detected. When the sensitivity changes and increases by more than 2dB, all recorded signals should be re-evaluated. 6.6 When re-detecting or re-evaluating forgings, instruments, probes, frequencies and coupling agents that are comparable or the same as those used in the initial detection should be used. 6.7 Determination of material attenuation coefficient
6.7.1 According to the requirements of the technical conditions of forgings, three representative locations are selected in the defect-free area of the forging to be tested to measure the B-B, value, that is, the dB difference between the first bottom wave B, and the second bottom wave B,. The material attenuation coefficient is the average of the attenuation coefficients at the three locations. 3
JB/T1581-1996
6.7.2 Calculate the material attenuation coefficient (dB/m) according to formula (3): (BB,)- 6dB
Where: T—sound path, m.
7 Classification of defect signals
(3)
7.1 Single scattered defect signal: The distance between two adjacent defects is greater than the multiple of the larger defect equivalent diameter, reaching the specified value in the corresponding technical conditions in the appendix, and the minimum defect equivalent meets the specified value of the technical conditions. When the probe moves in any direction from the position of maximum signal reflection of the defect, the signal amplitude decreases normally without fluctuations. 7.2 Dense defect signal: In a cube with a side length of 50mm, there are not less than 5 defect signals with an equivalent diameter not less than the value specified in the technical conditions.
7.3 Continuous (strip) defect signal: The defect equivalent at a certain distance is not less than the value specified in the technical conditions, and the fluctuation range of its reflection amplitude is not greater than 2dB within the interval of continuous movement of the probe of 30mm or more. 7.4 Moving defect signal: Under the sensitivity specified in the technical conditions, when the probe moves in the detected part, the moving distance of the signal front position is equivalent to the defect signal of a workpiece thickness of 25mm or more. 8 Measurement and recording of defects
After the defect signal is found during the flaw detection, different methods should be used to measure the defect according to the type of defect signal. 8.1 Measurement and recording of single scattered defects
8.1.1 Determine the equivalent diameter of the defect using the "AVG\ curve or calculation method. If necessary, the test block method can be used.8.1.2 Calculate the defect equivalent. When the material attenuation coefficient exceeds 4dB/m, it should be corrected.8.1.3 Record the equivalent diameter of the defect that is not less than the starting record and its coordinate position on the forging.8.2 Measurement and recording of dense defects in solid forgings8.2.1 Determine the depth distribution range of the defect based on the position of the defect signal front on the scanning line8.2.2
Determine the axial distribution range of the defect based on the moving range of the defect detected by the probe center sound beam.8.2.3 Determine the maximum equivalent diameter of the defect according to 8.1.1.8.2.4 The boundary of the dense defect area is for geometric analysis. Corrected defect distribution range. 8.2.5 Record the size of the defect dense area, the maximum defect equivalent diameter and its coordinate position on the forging. 8.3 Measurement and recording of dense defects in hollow forgings 8.3.1 Determine the depth distribution range of the defect based on the position of the defect signal front on the scanning line. 8.3.2 Determine the axial distribution range of the defect based on the moving range of the defect detected by the central sound beam of the probe. 8.3.3 Determine the circumferential distribution range of the defect based on the moving range of the defect detected by the central sound beam of the probe and the geometric correction value based on the curvature of the detected part.
8.3.4 Determine the maximum equivalent diameter of the defect according to 8.1.1. 8.3.5 The boundary of the dense defect area is the range composed of the axial distribution boundary and the circumferential distribution boundary of the defect. 8.3.6 Record the defect The size of the densely-defected area, the maximum defect equivalent diameter and its coordinate position on the forging. 8.4 Measurement and recording of continuous (strip) defects 8.4.1 Use the half-wave height method to determine the axial indication length of the defect, and make a geometric correction based on the curvature of the measured part to determine the defect width perpendicular to the indication 4
length.
JB/T1581-1996
8.4.2 Determine the maximum equivalent diameter of the defect according to 8.1.1 8.4.3 Record the length, width, maximum defect equivalent diameter and its coordinate position on the forging of the continuous (strip) defect. 8.5 Measurement and recording of floating defect signals
8.5.1 Determine the minimum and maximum values of the signal floating on the scanning line to determine the signal floating range. 8.5.2 Use wave height elimination 8.5.3 Determine the axial length of the defect by the 6dB method. 8.5.4 Determine the equivalent diameter and position of the defect at the maximum signal according to 8.1.1. 8.5.5 Record the defect signal movement range, the probe movement arc length range, the axial length, the maximum reflection equivalent diameter and its coordinate position on the forging.
8.6 For the parts where the bottom wave is significantly reduced due to the defect, the degree of reduction of the bottom wave and the area of significant reduction should be measured and recorded. 8.7 When it is necessary to determine the nature of the defect, a comprehensive analysis should be conducted based on the defect size (equivalent, length, width, etc.), number, shape, orientation distribution, static and dynamic characteristics of the signal, and process factors such as smelting, forging, heat treatment, etc., and opinions on determining the nature of the defect should be put forward. If necessary, other inspection methods should also be adopted for collaborative verification. 9 Evaluation of flaw detection results
The flaw detection results of various forgings shall be evaluated in accordance with the provisions of JB/T7025, JB/T1265, JB/T7027, JB/T7026, JB/T1267 and JB7178, see Appendix A (Appendix to the standard). 10 Flaw detection report
10.1 After the flaw detection is completed, a flaw detection report shall be written. 10.2 The flaw detection report requires clear and neat handwriting, clear charts, and shall be completed in full according to the format specified in the report. The flaw detection report shall include the following contents: a) forging name, drawing number, material, dimensional diagram, heat treatment status; b) forging production number, furnace number, card number (workpiece serial number); c) commissioning unit, commission date, commission number, flaw detection standard, flaw detection conditions, and flaw detection location; d) defect location, defect depth, equivalent diameter, bottom wave reduction area, and defect distribution diagram; e) parts that have not been inspected and their reasons, and other situations that need to be explained; \ flaw detection evaluation results obtained through comprehensive analysis; g) flaw detection date, signatures of the flaw detector and reviewer. 5
JB/T 1581-1996
Appendix A
(Appendix to the standard)
Requirements for ultrasonic flaw detection evaluation (technical condition extract) The flaw detection results of various forgings shall be evaluated according to the following technical conditions. A1JB/T7025-93 "Technical conditions for turbine rotor and main shaft forgings below 25MIW" generally requires that forgings are not allowed to have defects such as cracks, white spots, shrinkage holes, folds, excessive segregation, etc. A1.2 Ultrasonic inspection
Unless otherwise specified, ultrasonic inspection shall comply with the following provisions. A1.2.1 Single scattered defects with an equivalent diameter less than 2mm are not counted. A1.2.2 No part of the rotor body shall have defects with an equivalent diameter greater than 5mm, and the blade root groove shall be deepened by 25mm. Defects with an equivalent diameter greater than 3mm are not allowed in the transmission end bearing and other parts. A1.2.3 Dense defects with an equivalent diameter greater than or equal to 2mm are not allowed. A1.2.4 No wandering signals and continuous defect signals are allowed. A1.2.5 Provide the measured data of the attenuation coefficient of the longitudinal wave of forging materials at 2 to 2.5MHz. A1.2.6
5 For single defects with an equivalent size greater than or equal to Φ2mm, their positions shall be marked with three-dimensional coordinates and indicated in the certificate of conformity. A1.2.7 Defects exceeding the above requirements shall be reported to the purchaser and handled by negotiation between the two parties. Note: Dense defect signals refer to defect signals with a quantity of not less than 5 and an equivalent diameter of not less than 2mm in a cube with a side length of 50mm. 2JB/T126593 "Technical Conditions for 25200MW Steam Turbine Rotor Body and Main Shaft Forgings" A2
General Requirements
Forgings are not allowed to have defects such as cracks, white spots, shrinkage holes, folds, excessive segregation, etc. A2.2 Ultrasonic Inspection
A2.2.1 Single scattered defect signals with an equivalent diameter of less than 2mm are not counted, but the noise height should be less than
50% of the amplitude of the equivalent diameter of 2mm1.
A22.2 Single scattered defects are defined as defects where the distance between two adjacent defects is greater than 10 times the equivalent diameter of the larger defect. A2.2.3 The equivalent diameter and number of single scattered defects shall not exceed those specified in Table A1. Table A1 Allowable number of defects
Equivalent range
Among them:
Allowable amount of parts
Transmission end
Non-transmission end
Allowable number of defects
Note: Both ends of the medium-pressure rotor body and the low-pressure rotor body are transmission ends, so the allowable number of defects at both ends is in accordance with the transmission end regulations6
JB/T1581—1996
A2.2.4 There should be no dense signal defects with an equivalent diameter of 1.6mm within 30mm from the center hole surface and within the range of 25mm of the outer circular groove depth on the shaft body. Single scattered defects with an equivalent diameter of less than 3mm are allowed. A2.2.5 When the bottom wave attenuation loss caused by the defect reaches 3dB, it shall be recorded and reported to the purchaser. A2.2.6 No wandering signals and strip defect signals are allowed. A2.2.7 The supplier shall provide the buyer with the material attenuation data measured at the two ends and three locations in the middle of the rotor body with 2-25MHz and 4-5MHz probes respectively.
A2.2.8 When the ultrasonic flaw detection results of forgings exceed the above provisions, the supplier and the buyer shall conduct re-inspection and discussion, but whether the forgings can be judged as qualified shall be determined by the buyer.
A3JB/T702793 "Technical Conditions for 300-600MW Steam Turbine Rotor Forgings" A3.1 General requirements
Forgings are not allowed to have defects such as cracks, white spots, shrinkage holes, folds, excessive segregation, etc. A3.2 Ultrasonic inspection
A3.2.1 Single scattered defect signals with an equivalent diameter of less than 1.6mm are not counted, but the noise height shall be less than 50% of the amplitude of the equivalent diameter of 1.6mm.
A3.2.2 A single scattered defect is defined as a defect in which the distance between two adjacent defects is greater than 10 times the equivalent diameter of the larger defect. A3.2.3 The axial, radial and circumferential positions of all defects with an equivalent diameter of 1.6 to 3.5 mm shall be recorded and reported to the purchaser. The total number of defects with an equivalent diameter of 1.6 to 3.5 mm shall not exceed 20, and any defect with an equivalent diameter greater than 3.5 mm is not allowed. A3.2.4 Three dense defect areas with an equivalent diameter less than 1.6 mm are allowed outside 75 mm from the center hole surface, but the size of the dense area in any direction shall not exceed 20 mm, and the distance between any two defect areas shall not be less than 120 mm. A3.2.5 When the bottom wave attenuation loss caused by the defect reaches 3 dB, it shall be recorded and reported to the purchaser. A3.2.6 No wandering signals or strip defect signals are allowed. A3.2.7 The supplier shall provide the purchaser with the material attenuation data measured at the two ends and three locations in the middle of the rotor body at the maximum diameter using 2~2.5MHz and 4~5MHz probes.
A3.2.8 When the ultrasonic flaw detection results of forgings exceed the above provisions, the supplier and the purchaser shall conduct re-inspection and discussion, but whether the forgings can be judged as qualified shall be decided by the purchaser.
A4JB/T702693 "Technical conditions for turbine generator rotor forgings below 50MW" The outer surface of the forging shall be subjected to ultrasonic flaw detection, and the test results shall comply with the following provisions: a) No defects such as cracks, white spots and shrinkage holes are allowed; b) Defects with an equivalent diameter of less than 2mm are not counted c) No continuous defect signals, dense defect signals and wandering signals are allowed; ①) Single defects with an equivalent diameter of 2 to 5mm are allowed to exist, but the distance between two adjacent defects shall not be less than 5 times the diameter of the larger defect, and the total number shall not exceed 56; e) In the area with greater stress (within the range of 25mm for the outer groove depth and 60mm for the center hole diameter of the rotor with a center hole), no defects with an equivalent diameter greater than 4mm are allowed;
f) When using 2 to 2.5MHz frequency for flaw detection, the material attenuation coefficient shall be less than or equal to 4dB/m. 74 Three dense defect areas with an equivalent diameter of less than 1.6 mm are allowed in the area 75 mm away from the center hole surface, but the size of the dense area in any direction shall not exceed 20 mm, and the distance between any two defect areas shall not be less than 120 mm. A3.2.5 When the bottom wave attenuation loss caused by defects reaches 3 dB, it shall be recorded and reported to the purchaser. A3.2.6 No wandering signals and strip defect signals are allowed. A3.2.7 The supplier shall provide the purchaser with material attenuation data measured at the two ends and three places in the middle of the maximum diameter of the rotor body using 2~2.5MHz and 4~5MHz probes.
A3.2.8 When the ultrasonic flaw detection results of forgings exceed the above provisions, the supplier and the purchaser shall conduct re-inspection and discussion, but whether the forgings can be judged to be qualified shall be decided by the purchaser.
A4JB/T702693 "Technical conditions for turbine generator rotor forgings below 50MW" The outer surface of the forging shall be subjected to ultrasonic flaw detection, and the test results shall comply with the following provisions: a) No defects such as cracks, white spots and shrinkage holes are allowed; b) Defects with an equivalent diameter of less than 2mm are not counted c) No continuous defect signals, dense defect signals and wandering signals are allowed; ①) Single defects with an equivalent diameter of 2 to 5mm are allowed to exist, but the distance between two adjacent defects shall not be less than 5 times the diameter of the larger defect, and the total number shall not exceed 56; e) In the area with greater stress (within the range of 25mm for the outer groove depth and 60mm for the center hole diameter of the rotor with a center hole), no defects with an equivalent diameter greater than 4mm are allowed;
f) When using 2 to 2.5MHz frequency for flaw detection, the material attenuation coefficient shall be less than or equal to 4dB/m. 74 Three dense defect areas with an equivalent diameter of less than 1.6 mm are allowed in the area 75 mm away from the center hole surface, but the size of the dense area in any direction shall not exceed 20 mm, and the distance between any two defect areas shall not be less than 120 mm. A3.2.5 When the bottom wave attenuation loss caused by defects reaches 3 dB, it shall be recorded and reported to the purchaser. A3.2.6 No wandering signals and strip defect signals are allowed. A3.2.7 The supplier shall provide the purchaser with material attenuation data measured at the two ends and three places in the middle of the maximum diameter of the rotor body using 2~2.5MHz and 4~5MHz probes.
A3.2.8 When the ultrasonic flaw detection results of forgings exceed the above provisions, the supplier and the purchaser shall conduct re-inspection and discussion, but whether the forgings can be judged to be qualified shall be decided by the purchaser.
A4JB/T702693 "Technical conditions for turbine generator rotor forgings below 50MW" The outer surface of the forging shall be subjected to ultrasonic flaw detection, and the test results shall comply with the following provisions: a) No defects such as cracks, white spots and shrinkage holes are allowed; b) Defects with an equivalent diameter of less than 2mm are not counted c) No continuous defect signals, dense defect signals and wandering signals are allowed; ①) Single defects with an equivalent diameter of 2 to 5mm are allowed to exist, but the distance between two adjacent defects shall not be less than 5 times the diameter of the larger defect, and the total number shall not exceed 56; e) In the area with greater stress (within the range of 25mm for the outer groove depth and 60mm for the center hole diameter of the rotor with a center hole), no defects with an equivalent diameter greater than 4mm are allowed;
f) When using 2 to 2.5MHz frequency for flaw detection, the material attenuation coefficient shall be less than or equal to 4dB/m. 7
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