1、Designation: A418/A418M 10Standard Practice forUltrasonic Examination of Turbine and Generator SteelRotor Forgings1This standard is issued under the fixed designation A418/A418M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice for ultrasonic examination covers turbineand generator steel rotor forgings covered by Specific
3、ationsA469/A469M, A470/A470M, A768/A768M, and A940/A940M. This standard shall be used for contact testing only.1.2 This practice describes a basic procedure of ultrasoni-cally inspecting turbine and generator rotor forgings. It doesnot restrict the use of other ultrasonic methods such asreference bl
4、ock calibrations when required by the applicableprocurement documents nor is it intended to restrict the use ofnew and improved ultrasonic test equipment and methods asthey are developed.1.3 This practice is intended to provide a means of inspect-ing cylindrical forgings so that the inspection sensi
5、tivity at theforging center line or bore surface is constant, independent ofthe forging or bore diameter. To this end, inspection sensitivitymultiplication factors have been computed from theoreticalanalysis, with experimental verification. These are plotted inFig. 1 (bored rotors) and Fig. 2 (solid
6、 rotors), for a trueinspection frequency of 2.25 MHz, and an acoustic velocity of2.30 3 105in./s 5.85 3 105cm/s. Means of converting toother sensitivity levels are provided in Fig. 3. (Sensitivitymultiplication factors for other frequencies may be derived inaccordance with X1.1 and X1.2 of Appendix
7、X1.)1.4 Considerable verification data for this method have beengenerated which indicate that even under controlled conditionsvery significant uncertainties may exist in estimating naturaldiscontinuities in terms of minimum equivalent size flat-bottom holes. The possibility exists that the estimated
8、 mini-mum areas of natural discontinuities in terms of minimumareas of the comparison flat-bottom holes may differ by 20 dB(factor of 10) in terms of actual areas of natural discontinuities.This magnitude of inaccuracy does not apply to all results butshould be recognized as a possibility. Rigid con
9、trol of theactual frequency used, the coil bandpass width if tunedinstruments are used, and so forth, tend to reduce the overallinaccuracy which is apt to develop.1.5 This practice for inspection applies to solid cylindricalforgings having outer diameters of not less than 2.5 in. 64mm nor greater th
10、an 100 in. 2540 mm. It also applies tocylindrical forgings with concentric cylindrical bores havingwall thicknesses of 2.5 64 mm in. or greater, within the sameouter diameter limits as for solid cylinders. For solid sectionsless than 15 in. 380 mm in diameter and for bored cylindersof less than 7.5
11、in. 190 mm wall thickness the transducer usedfor the inspection will be different than the transducer used forlarger sections.1.6 Supplementary requirements of an optional nature areprovided for use at the option of the purchaser. The supple-mentary requirements shall apply only when specified indi-
12、vidually by the purchaser in the purchase order or contract.1.7 This practice is expressed in both inch-pound units andin SI units; however, unless the purchase order or contractspecifies the applicable M specification designation (SI units),the inch-pound units shall apply. The values stated in eit
13、herinch-pound units or SI units are to be regarded separately asstandard. Within the practice, the SI units are shown inbrackets. The values stated in each system may not be exactequivalents; therefore, each system shall be used independentlyof the other. Combining values from the two systems mayres
14、ult in nonconformance with the standard.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory
15、limitations prior to use.2. Referenced Documents2.1 The reference is to the latest issue of these designationsthat appear in the Annual Book of ASTM Standards or areavailable as separate reprints. It shall also apply to productspecifications, which may be issued when specifically refer-enced therein
16、.2.2 ASTM Standards:2A469/A469M Specification forVacuum-Treated Steel Forg-ings for Generator Rotors1This practice is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current
17、edition approved Nov. 1, 2010. Published December 2010. Originallyapproved in 1957. Last previous edition approved in 2009 as A418/A418M 09.DOI: 10.1520/A0418_A0418M-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annua
18、l Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.A470/A470M
19、Specification for Vacuum-Treated Carbonand Alloy Steel Forgings for Turbine Rotors and ShaftsA768/A768M Specification for Vacuum-Treated 12 %Chromium Alloy Steel Forgings for Turbine Rotors andShaftsA940/A940M Specification for Vacuum Treated Steel Forg-ings,Alloy, Differentially Heat Treated, for T
20、urbine RotorsE317 Practice for Evaluating Performance Characteristicsof Ultrasonic Pulse-Echo Testing Instruments and Systemswithout the Use of Electronic Measurement InstrumentsE1065 Guide for Evaluating Characteristics of UltrasonicSearch Units2.3 Other Standards:Recommended Practice No. SNT-TC-1A
21、 Personnel Quali-fication and Certification in Nondestructive Testing33. Significance and Use3.1 This practice shall be used when ultrasonic inspection isrequired by the order or specification for inspection purposeswhere the acceptance of the forging is based on limitations ofthe number, amplitude,
22、 or location of discontinuities, or acombination thereof, which give rise to ultrasonic indications.3.2 The acceptance criteria shall be clearly stated as orderrequirements.3Available from American Society for Nondestructive Testing, PO Box 28518,1711 Arlingate Lane, Columbus, OH 43228.NOTESensitivi
23、ty multiplication factor such that a 10 % indication at the forging bore surface will be equivalent to a18 in. 3 mm diameter flat bottomhole. Inspection frequency: 2.0 or 2.25 MHz. Material velocity: 2.30 3 105in./s 5.85 3 105cm/s.FIG. 1 Bored ForgingsA418/A418M 1024. General Requirements4.1 As far
24、as possible, the entire volume of the forging shallbe subjected to ultrasonic inspection. Because of fillets at stepsand other local configurations, access to inspect some portionsof a forging may be limited.4.2 The ultrasonic inspection shall be performed after finalheat treatment of the forging. I
25、n those cases in which wheels,slots, or similar features are machined into the forging beforeheat treatment, the entire forging shall be inspected ultrasoni-cally before such machining, and as completely as practicableafter the final heat treatment.4.3 For overall scanning, the ultrasonic beam shall
26、 beintroduced radially. To conform with this requirement, externalconical surfaces of the forging shall be replaced by steppedsurfaces in order to maintain the ultrasonic beam perpendicularto the longitudinal axis. Such stepped surfaces shall be shownon the forging drawing.4.4 Forgings may be tested
27、 either stationary or while rotatedby means of a lathe or rollers. If not specified by the purchaser,either method may be used at the manufacturers option.Scanning speed shall not exceed 6 in./s 15 cm/s.4.5 To ensure complete coverage of the forging volume, thesearch unit shall be indexed no more th
28、an 75 % of thetransducer width with each pass of the search unit. Mechanizedinspection of the rotating forging wherein the search unit ismechanically controlled is an aid in meeting this requirement.4.6 Frequencies of 1, 2.25, and 5 MHz may be used foraccurately locating, determining orientation, an
29、d defining spe-cific discontinuities detected during overall scanning as de-scribed in 4.4.4.7 Axial scanning, if required, shall be performed at thatfrequency and transducer diameter which minimizes interfer-ing ultrasonic reflections due to forging geometry and whichNOTESensitivity multiplication
30、factor such that a 10 % indication at the forging centerline surface will be equivalent to a18 in. 3 mm diameter flatbottom hole. Inspection frequency: 2.0 or 2.25 MHz. Material velocity: 2.30 3 105in./s 5.85 3 105cm/s.FIG. 2 Solid ForgingsA418/A418M 103gives optimum resolution. (Axial tests are nor
31、mally used as asupplement to radial tests.)5. Personnel Requirements5.1 Personnel performing the ultrasonic examinations to thispractice shall be qualified and certified in accordance with awritten procedure conforming to Recommended Practice No.SNT-TC-1A or another national standard that is accepta
32、ble toboth the purchaser and the supplier.6. Pulsed Ultrasonic Reflection Equipment andAccessories6.1 Electronic ApparatusApulse-echo instrument permit-ting inspection frequencies of 1, 2.25, and 5 MHz is required.The accuracy of discontinuity amplitude analysis using thispractice involves a knowled
33、ge of the true operating frequencyof the complete inspection system. One of the best ways toobtain the desired accuracy is by use of a tuned pulser andnarrow band amplifier of known frequency response, witheither a broadband transducer, or a narrow-band tuned trans-ducer of known and matching freque
34、ncy.6.1.1 Apparatus Qualification and CalibrationBasicqualification of the ultrasonic test instrument shall be per-formed at intervals not to exceed 12 months or whenevermaintenance is performed that affects the equipment function.The date of the last calibration and the date of the next requiredcal
35、ibration shall be displayed on the test equipment.6.1.2 The horizontal linearity shall be checked on a distancecalibration bar using the multiple order technique (see PracticeE317). The horizontal linearity shall be 62 % of the metalpath.6.1.3 If the rotor has a coupling or similar thin axial sectio
36、nwith parallel sides, the accuracy of the linearity shall bechecked by ultrasonically verifying the thickness of the cou-pling or axial section. If necessary, minor adjustments fordifferences in the ultrasonic velocities between the calibrationbar and the forging shall then be made.6.2 AmplifierThe
37、amplifier and display shall provide lin-ear response within 62 %, up to 100% of full screen height.6.2.1 Amplifier CalibrationAn amplifier vertical linearitycheck shall be made prior to performing the test by observinga multiple order pattern from a calibration block using a 2.25MHz transducer (see
38、Practice E317). The first back reflectionshall be set at 100 % of full screen height. The higher orderback reflections, 10 % and higher in amplitude, shall also bepositioned on the screen and their amplitudes noted. The firstback reflection shall be reduced to 50 % and then 25 % of fullscreen height
39、. The amplitudes of the higher order back reflec-tions shall be noted at each step. The vertical linearity will beconsidered acceptable if the signal heights of the higher orderreflections decrease in proportion to the decrease set for thefirst back reflection. The maximum acceptable error for thede
40、crease of the higher order reflections is the greater of 65%of the expected back reflection height or 62 % of full screenheight.6.3 Signal AttenuatorThe instrument shall contain a cali-brated gain control or signal attenuator that meets the require-ments of Practice E317 (in each case, accurate with
41、in 65%)that will allow indications beyond the linear range of theinstrument to be measured. It is recommended that thesecontrols permit signal adjustments up to 25 to 1 (28 dB) (seeFig. 1 and Fig. 2).FIG. 3 Conversion Factors to Be Used in Conjunction with Fig. 1 and Fig. 2 if a Change in the Refere
42、nce Reflector Diameter isRequiredA418/A418M 1046.4 Search UnitsLongitudinal wave search units ofknown effective frequency should be used for radial scanning.A14 by 1 in. 6 by 24 mm, 2.0 or 2.25 MHz transducer, usedwith the 1-in. 24-mm dimension parallel to the forging axis,will give a desirable comb
43、ination of resolution and beam widthon large sections 15 in. 380 mm in diameter or larger if solidor 7.5 in. 190 mm or greater wall thickness if bored. A 1-in.24-mm diameter, 2.0 or 2.25 MHz transducer may be used. Ifa transducer with dimension circumferentially oriented to theforging, larger than14
44、 in. 6 mm is used, additional inspectionat lower frequency is recommended to provide a wide beam foroff-axis inspection. A 0.5-in. 10-mm diameter 2.0 or 2.25MHz transducer is suitable for solid sections under 15 in. 380mm in diameter and bored sections under 7.5 in. 190 mm inwall thickness. The mult
45、iplication factors given are valid forthe frequency and material velocity indicated provided they areused in the far field. (The near field is a characteristic that isdependent on the transducer frequency and size.) For otherfrequencies and material velocities, applicable sensitivity mul-tiplication
46、 factors shall be computed.6.4.1 Search Unit CalibrationThe transducers used inperforming the tests described in this practice shall be cali-brated in accordance with Guide E1065.7. Preparation of Forging for Ultrasonic Inspection7.1 Machine turn the forging to provide cylindrical surfacesfor the ra
47、dial test.7.2 The end faces of the shaft extensions and of the body ofthe forging shall be sufficiently perpendicular to the axis of theforging to permit axial test.7.3 The surface roughness of exterior finishes shall notexceed 250 in. 6.35 m and the surface waviness shall notinterfere with the ultr
48、asonic test.7.4 At the time of ultrasonic testing, the surfaces of theforging shall be free of tool tears, loose scale, machining orgrinding particles, paint, or other foreign material.8. Procedure8.1 Radial Scanning:8.1.1 Select the transducer to be used for the primaryinspection according to the f
49、ollowing criteria:8.1.1.1 Use a 0.5-in. 10-mm diameter, 2.0 or 2.25 MHztransducer to inspect solid cylindrical sections under 15 in.380 mm in diameter and bored sections having wall thick-nesses of less than 7.5 in. 190 mm.8.1.1.2 Use a14 by 1 in. 6 by 24 mm (or 1-in. 24-mmdiameter), 2.0 or 2.25 MHz transducer to inspect solid sections15 in. 380 mm or greater in diameter and bored sectionshaving wall thicknesses of 7.5 in. 190 mm or greater.8.1.2 The reference signal shall be the signal reflected fromthe di
