ASTM A418 A418M-2007 Standard Practice for Ultrasonic Examination of Turbine and Generator Steel Rotor Forgings.pdf

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1、Designation: A 418/A 418M 07Standard Practice forUltrasonic Examination of Turbine and Generator SteelRotor Forgings1This standard is issued under the fixed designationA418/A 418M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, th

2、e year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon (e) 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 293,A 469/A 469M, andA 470/A 470M. This standard shallbe used for contact testing only.1.2 This practice describes a basic procedure of ultrasoni-cally inspecting turbine and generator rotor forgings. It shall inno way restrict the use of other ultrasonic methods such asreference block ca

4、librations 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. The procedure utilizes different calibrationtechniques than had been used in previous issues. The fre-quency or amplit

5、udes of recordable indications should not beinterpreted necessarily as a change in quality of the productbeing examined.1.3 This practice is intended to provide a means of inspect-ing cylindrical forgings so that the inspection sensitivity at theforging center line or bore surface is constant, indep

6、endent 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 rotors), for a trueinspection frequency of 2.25 MHz, and an acoust

7、ic 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 X1.)1.4 Considerable verification data for this method have beengen

8、erated 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 mini-mum areas of natural discontinuities in terms of minimumareas

9、 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 control of theactual frequency used, the coil bandpass width if tunedi

10、nstruments 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 than 100 in. 2540 mm. It also applies tocylindrical forgings with con

11、centric 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 in. 190 mm wall thickness the transducer usedfor the inspection wil

12、l 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-vidually by the purchaser in the purchase order or contract.1.7 Thi

13、s 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 eitherinch-pound units or SI units are to be regarded separately assta

14、ndard. 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 mayresult in nonconformance with the standard.1.8 This standard does not

15、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 limitations prior to use.1This practice is under the jurisdiction o

16、f 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 May 1, 2007. Published May 2007. Originallyapproved in 1957. Last previous edition approved in 2005 as A 418/A 418M 05.1*A Su

17、mmary 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.2. Referenced Documents2.1 The reference is to the latest issue of these designationsthat appear in the Annual Book of ASTM S

18、tandards or areavailable as separate reprints. It shall also apply to productspecifications, which may be issued when specifically refer-enced therein.2.2 ASTM Standards:2A 293 Specification for Steel Forgings, Carbon and Alloy,for Turbine Rotors and Shafts3A 469/A 469M Specification for Vacuum-Trea

19、ted SteelForgings for Generator RotorsA 470/A 470M Specification for Vacuum-Treated Carbonand Alloy Steel Forgings for Turbine Rotors and ShaftsE 317 Practice for Evaluating Performance Characteristicsof Ultrasonic Pulse-Echo Testing Instruments and Systemswithout the Use of Electronic Measurement I

20、nstrumentsE 1065 Guide for Evaluating Characteristics of UltrasonicSearch Units3. 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, a

21、mplitude, or location of discontinuities, or acombination thereof, which give rise to ultrasonic indications.3.2 The acceptance criteria shall be clearly stated as orderrequirements.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.o

22、rg. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.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 fr

23、equency: 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 0724. General Requirements4.1 As far as possible, the entire volume of the forging shallbe subjected to ultrasonic inspection. Because of fillets atstepdowns and other local configurations,

24、it may be impossibleto inspect some small portions of a forging.4.2 The ultrasonic inspection 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 inspect

25、ed ultrasoni-cally before such machining, and as completely as practicableafter the final heat treatment.4.3 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

26、to maintain the ultrasonic beam perpendicularto the longitudinal axis. Such stepped surfaces shall be shownon 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 manufactur

27、ers 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 approximately 75 % of thetransducer width with each pass of the search unit. Mechanizedinspection of the rotating forging wherein the search unit ismechan

28、ically 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, and defining spe-cific discontinuities detected during overall scanning as de-scribed in 4.4.4.7 Axial scanning, if required, shall be performed

29、at thatfrequency and transducer diameter which minimizes interfer-ing ultrasonic reflections due to forging geometry and whichNOTESensitivity multiplication factor such that a 10 % indication at the forging centerline surface will be equivalent to a18 in. 3 mm diameter flatbottom hole. Inspection fr

30、equency: 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 073gives optimum resolution. (Axial tests are normally used as asupplement to radial tests.)5. Personnel Requirements5.1 Personnel performing the ultrasonic examinations to thispractice shal

31、l be qualified and certified in accordance with awritten procedure conforming to Recommended Practice No.SNT-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 instrum

32、ent permit-ting inspection frequencies of 1, 2.25, and 5 MHz is required.The accuracy of discontinuity amplitude 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

33、pulser andnarrow band amplifier of known frequency response, witheither a broadband transducer, or a narrow-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

34、 exceed 12 months or whenevermaintenance is performed that affects the equipment function.The date of the last 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 mult

35、iple order technique (see PracticeE 317). The horizontal linearity shall be 62 % of the metalpath.6.1.3 If 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 sect

36、ion. If necessary, minor adjustments fordifferences in the ultrasonic velocities between the calibrationbar 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 a

37、mplifier 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 Practice E 317). The first back reflectionshall be set at 100 % of full screen height. The higher orderback reflections, 10 % and

38、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. The amplitudes of the higher order back reflec-tions shall be noted at each step. The vertical linearity will beconsidered acce

39、ptable if the signal heights of the higher orderreflections decrease in proportion to the decrease set for 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

40、.3 Signal AttenuatorThe instrument shall contain a cali-brated gain control or signal attenuator that meets the require-ments of Practice E 317 (in each case, accurate within 65%)that will allow indications beyond the linear range of theFIG. 3 Conversion Factors to Be Used in Conjunction with Fig. 1

41、 and Fig. 2 if a Change in the Reference Reflector Diameter isRequiredA 418/A 418M 074instrument 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 search units ofknown effective frequency shou

42、ld 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 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

43、 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 in. 6 mm is used, additional inspectionat lower frequency is recommended to provide a wide beam foroff-axis inspection. A 0.5

44、-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 multiplication factors given are valid forthe frequency and material velocity indicated provided they areused in the far field. (T

45、he near field is a characteristic that isdependent on the transducer frequency and size.) For otherfrequencies 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

46、 shall be cali-brated in accordance with Guide E 1065.7. Preparation of Forging for Ultrasonic Inspection7.1 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

47、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 ultrasonic test.7.4 At the time of ultrasonic testing, the surfaces of theforging shall be free of tool tears, loose scale, machi

48、ning 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 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

49、 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 diametrically opposed surface for solid (unbored) forgingsand from the bore surface of bored forgings. The signalamplitude shall