1、Designation: A 418/A 418M 09Standard Practice forUltrasonic Examination of Turbine and Generator SteelRotor Forgings1This standard is issued under the fixed designationA 418/A 418M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, t
2、he 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 Speci
3、ficationsA 469/A 469M, A 470/A 470M, A 768/A 768M, and A 940/A 940M. 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 asr
4、eference block 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 inspe
5、ction sensitivity 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 Fi
6、g. 2 (solid 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 o
7、f Appendix 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 th
8、e estimated 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
9、. Rigid control 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
10、 greater than 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 les
11、s than 7.5 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 spec
12、ified indi-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 st
13、ated in eitherinch-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 sys
14、tems mayresult 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
15、regulatory 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-en
16、ced therein.2.2 ASTM Standards:2A 469/A 469M Specification for Vacuum-Treated Steel1This 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 edition approved
17、May 1, 2009. Published May 2009. Originallyapproved in 1957. Last previous edition approved in 2007 as A 418/A 418M 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer
18、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.Forgings for Generator RotorsA 470/A 470M Specification for V
19、acuum-Treated Carbonand Alloy Steel Forgings for Turbine Rotors and ShaftsA 768/A 768M Specification for Vacuum-Treated 12 %Chromium Alloy Steel Forgings for Turbine Rotors andShaftsA 940/A 940M Specification for Vacuum Treated SteelForgings, Alloy, Differentially Heat Treated, for TurbineRotorsE 31
20、7 Practice for Evaluating Performance Characteristicsof Ultrasonic Pulse-Echo Testing Instruments and Systemswithout the Use of Electronic Measurement InstrumentsE 1065 Guide for Evaluating Characteristics of UltrasonicSearch Units3. Significance and Use3.1 This practice shall be used when ultrasoni
21、c inspection isrequired by the order or specification for inspection purposeswhere the acceptance of the forging is based on limitations ofthe number, amplitude, or location of discontinuities, or acombination thereof, which give rise to ultrasonic indications.3.2 The acceptance criteria shall be cl
22、early stated as orderrequirements.4. General Requirements4.1 As far 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 inspe
23、ction shall be performed after finalheat treatment of the forging. In 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 fina
24、l heat treatment.NOTESensitivity 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 ForgingsA 418/A 418M 0924.
25、3 For overall scanning, the ultrasonic beam shall 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 shown
26、on the forging drawing.4.4 Forgings may be tested 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 v
27、olume, thesearch unit shall be indexed approximately 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 f
28、oraccurately locating, determining orientation, and 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
29、 geometry and whichgives optimum resolution. (Axial tests are normally 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 P
30、ractice No.NOTESensitivity multiplication 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 ForgingsA 418/A 418M 093SN
31、T-TC-1A or another national standard that is acceptable 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 ampl
32、itude analysis using thispractice involves a knowledge 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
33、-band tuned trans-ducer of known and matching frequency.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 l
34、ast calibration and the date of the next requiredcalibration 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 PracticeE 317). The horizontal linearity shall be 62 % of the metalpath.6.1.3 If
35、the rotor has a coupling or similar thin axial sectionwith 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
36、 and the forging shall then be made.6.2 AmplifierThe amplifier and the cathode ray tube shallprovide linear response within 62 %, up to 100% of full screenheight.6.2.1 Amplifier CalibrationAn amplifier vertical linearitycheck shall be made prior to performing the test by observinga multiple order pa
37、ttern from a calibration block using a 2.25MHz transducer (see Practice E 317). 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 reflec
38、tion shall be reduced to 50 % and then 25 % of fullscreen height. 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
39、thefirst back reflection. The maximum acceptable error for thedecrease 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
40、 the require-ments of Practice E 317 (in each case, accurate within 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).6.4 Search UnitsLongitudinal wave s
41、earch 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,FIG. 3 Conversion Factors to Be Used in Conjunction with Fig. 1 and Fig. 2 if a Change in the Reference Refl
42、ector Diameter isRequiredA 418/A 418M 094will give a desirable combination 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 wit
43、h dimension circumferentially oriented to theforging, larger than14 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
44、 and bored sections under 7.5 in. 190 mm inwall thickness. The multiplication 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 otherfrequenc
45、ies and material velocities, applicable sensitivity mul-tiplication 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 E 1065.7. Preparation of Forging for Ultrasonic Inspection7.
46、1 Machine turn the forging to provide cylindrical surfacesfor the radial 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
47、in. 6.35 m and the surface waviness shall notinterfere with the ultrasonic 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 th
48、e transducer to be used for the primaryinspection according to the following 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 U
49、se 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 diametrically opposed surface for solid (unbored) forgingsand from the bore surface of bored forgings. The signalamplitude shall be set to 100 % full screen height whilescanning in an indication-free area.8.1.3 The required evaluation
