1、Designation: A418/A418M 10A418/A418M 15Standard 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 r
2、evision, the 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 turbine and generator steel rotor forgings cover
3、ed by SpecificationsA469/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 ultrasonically inspecting turbine and generator rotor forgings. It does not restrictthe use of other ultrasonic methods such a
4、s reference block calibrations when required by the applicable procurement documentsnor is it intended to restrict the use of new and improved ultrasonic test equipment and methods as they are developed.1.3 This practice is intended to provide a means of inspecting cylindrical forgings so that the i
5、nspection sensitivity at the forgingcenter line or bore surface is constant, independent of the forging or bore diameter. To this end, inspection sensitivity multiplicationfactors have been computed from theoretical analysis, with experimental verification. These are plotted in Fig. 1 (bored rotors)
6、 andFig. 2 (solid rotors), for a true inspection frequency of 2.25 MHz, and an acoustic velocity of 2.30 105 in./s 5.85 105 cm/s.Means of converting to other sensitivity levels are provided in Fig. 3. (Sensitivity multiplication factors for other frequencies maybe derived in accordance with X1.1 and
7、 X1.2 of Appendix X1.)1.4 Considerable verification data for this method have been generated which indicate that even under controlled conditionsvery significant uncertainties may exist in estimating natural discontinuities in terms of minimum equivalent size flat-bottom holes.The possibility exists
8、 that the estimated minimum areas of natural discontinuities in terms of minimum areas of the comparisonflat-bottom holes may differ by 20 dB (factor of 10) in terms of actual areas of natural discontinuities.This magnitude of inaccuracydoes not apply to all results but should be recognized as a pos
9、sibility. Rigid control of the actual frequency used, the coil bandpasswidth if tuned instruments are used, and so forth, tend to reduce the overall inaccuracy which is apt to develop.1.5 This practice for inspection applies to solid cylindrical forgings having outer diameters of not less than 2.5 i
10、n. 64 mm norgreater than 100 in. 2540 mm. It also applies to cylindrical forgings with concentric cylindrical bores having wall thicknessesof 2.5 64 mm in. or greater, within the same outer diameter limits as for solid cylinders. For solid sections less than 15 in. 380mm in diameter and for bored cy
11、linders of less than 7.5 in. 190 mm wall thickness the transducer used for the inspection willbe different than the transducer used for larger sections.1.6 Supplementary requirements of an optional nature are provided for use at the option of the purchaser. The supplementaryrequirements shall apply
12、only when specified individually by the purchaser in the purchase order or contract.1.7 This practice is expressed in both inch-pound units and in SI units; however, unless the purchase order or contract specifiesthe applicable M specification designation (SI units), the inch-pound units shall apply
13、. The values stated in either inch-pound unitsor SI units are to be regarded separately as standard. Within the practice, the SI units are shown in brackets. The values stated ineach system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining value
14、s fromthe two systems may result in nonconformance with the standard.1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the
15、applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 The reference is to the latest issue of these designations that appear in the Annual Book of ASTM Standards or are availableas separate reprints. It shall also apply to product specifications, which may be issued when spe
16、cifically referenced therein.1 This practice is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.06on Steel Forgings and Billets.Current edition approved Nov. 1, 2010May 1, 2015. Published December 2010May
17、2015. Originally approved in 1957. Last previous edition approved in 20092010 asA418/A418M 09.A418/A418M 10. DOI: 10.1520/A0418_A0418M-10.10.1520/A0418_A0418M-15.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been
18、 made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.
19、*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 ASTM Standards:2A469/A469M Specification for Vacuum-Treated Steel Forgings for Generator RotorsA470/A470M Specificati
20、on for Vacuum-Treated Carbon and Alloy Steel Forgings for Turbine Rotors and ShaftsA768/A768M Specification for Vacuum-Treated 12 % Chromium Alloy Steel Forgings for Turbine Rotors and ShaftsA788/A788M Specification for Steel Forgings, General RequirementsA940/A940M Specification for Vacuum Treated
21、Steel Forgings, Alloy, Differentially Heat Treated, for Turbine RotorsE317 Practice for Evaluating Performance Characteristics of Ultrasonic Pulse-EchoTesting Instruments and Systems without theUse of Electronic Measurement InstrumentsE1065E1065/E1065M Practice for Evaluating Characteristics of Ultr
22、asonic Search Units2.3 Other Standards:Recommended Practice No. SNT-TC-1A Personnel Qualification and Certification in Nondestructive Testing33. Significance and Use3.1 This practice shall be used when ultrasonic inspection is required by the order or specification for inspection purposes wherethe a
23、cceptance of the forging is based on limitations of the number, amplitude, or location of discontinuities, or a combinationthereof, which give rise to ultrasonic indications.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For A
24、nnual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.NOTE 1Sensitivity multiplication facto
25、r such that a 10 % indication at the forging bore surface will be equivalent to a 18 in. 3 mm diameter flatbottom hole. Inspection frequency: 2.0 or 2.25 MHz. Material velocity: 2.30 105 in./s 5.85 105 cm/s.FIG. 1 Bored ForgingsA418/A418M 1523.2 The acceptance criteria shall be clearly stated as ord
26、er requirements.4. General Requirements4.1 As far as possible, the entire volume of the forging shall be subjected to ultrasonic inspection. Because of fillets at stepsand other local configurations, access to inspect some portions of a forging may be limited.4.2 The ultrasonic inspection shall be p
27、erformed after final heat treatment of the forging. In those cases in which wheels, slots,or similar features are machined into the forging before heat treatment, the entire forging shall be inspected ultrasonically beforesuch machining, and as completely as practicable after the final heat treatmen
28、t.4.3 For overall scanning, the ultrasonic beam shall be introduced radially. To conform with this requirement, external conicalsurfaces of the forging shall be replaced by stepped surfaces in order to maintain the ultrasonic beam perpendicular to thelongitudinal axis. Such stepped surfaces shall be
29、 shown on the forging drawing.4.4 Forgings may be tested either stationary or while rotated by 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
30、forging volume, the search unit shall be indexed no more than 75 % of the transducerwidth with each pass of the search unit. Mechanized inspection of the rotating forging wherein the search unit is mechanicallycontrolled is an aid in meeting this requirement.NOTE 1Sensitivity multiplication factor s
31、uch that a 10 % indication at the forging centerline surface will be equivalent to a 18 in. 3 mm diameterflat bottom hole. Inspection frequency: 2.0 or 2.25 MHz. Material velocity: 2.30 105 in./s 5.85 105 cm/s.FIG. 2 Solid ForgingsA418/A418M 1534.6 Frequencies of 1, 2.25, and 5 MHz may be used for a
32、ccurately locating, determining orientation, and defining specificdiscontinuities detected during overall scanning as described in 4.4.4.7 Axial scanning, if required, shall be performed at that frequency and transducer diameter which minimizes interferingultrasonic reflections due to forging geomet
33、ry and which gives optimum resolution. (Axial tests are normally used as a supplementto radial tests.)5. Personnel Requirements5.1 Personnel performing the ultrasonic examinations to this practice shall be qualified and certified in accordance with a writtenprocedure conforming to Recommended Practi
34、ce No. SNT-TC-1A or another national standard that is acceptable to both thepurchaser and the supplier.6. Pulsed Ultrasonic Reflection Equipment and Accessories6.1 Electronic ApparatusA pulse-echo instrument permitting inspection frequencies of 1, 2.25, and 5 MHz is required. Theaccuracy of disconti
35、nuity amplitude analysis using this practice involves a knowledge of the true operating frequency of thecomplete inspection system. One of the best ways to obtain the desired accuracy is by use of a tuned pulser and narrow bandamplifier of known frequency response, with either a broadband transducer
36、, or a narrow-band tuned transducer of known andmatching frequency.6.1.1 Apparatus Qualification and CalibrationBasic qualification of the ultrasonic test instrument shall be performed atintervals not to exceed 12 months or whenever maintenance is performed that affects the equipment function. The d
37、ate of the lastcalibration and the date of the next required calibration shall be displayed on the test equipment.6.1.2 The horizontal linearity shall be checked on a distance calibration bar using the multiple order technique (see PracticeE317). The horizontal linearity shall be 62 % of the metal p
38、ath.6.1.3 If the rotor has a coupling or similar thin axial section with parallel sides, the accuracy of the linearity shall be checkedby ultrasonically verifying the thickness of the coupling or axial section. If necessary, minor adjustments for differences in theultrasonic velocities between the c
39、alibration bar and the forging shall then be made.6.2 AmplifierThe amplifier and display shall provide linear response within 62 %, up to 100% of full screen height.6.2.1 Amplifier CalibrationAn amplifier vertical linearity check shall be made prior to performing the test by observing amultiple orde
40、r pattern from a calibration block using a 2.25 MHz transducer (see Practice E317). The first back reflection shall beset at 100 % of full screen height. The higher order back reflections, 10 % and higher in amplitude, shall also be positioned on thescreen and their amplitudes noted. The first back
41、reflection shall be reduced to 50 % and then 25 % of full screen height. Theamplitudes of the higher order back reflections shall be noted at each step. The vertical linearity will be considered acceptable ifFIG. 3 Conversion Factors to Be Used in Conjunction with Fig. 1 and Fig. 2 if a Change in th
42、e Reference Reflector Diameter is RequiredA418/A418M 154the signal heights of the higher order reflections decrease in proportion to the decrease set for the first back reflection. Themaximum acceptable error for the decrease of the higher order reflections is the greater of 65 % of the expected bac
43、k reflectionheight or 62 % of full screen height.6.3 Signal AttenuatorThe instrument shall contain a calibrated gain control or signal attenuator that meets the requirementsof Practice E317 (in each case, accurate within 65 %) that will allow indications beyond the linear range of the instrument to
44、bemeasured. It is recommended that these controls permit signal adjustments up to 25 to 1 (28 dB) (see Fig. 1 and Fig. 2).6.4 Search UnitsLongitudinal wave search units of known effective frequency should be used for radial scanning. A 14 by 1in. 6 by 24 mm, 2.0 or 2.25 MHz transducer, used with the
45、 1-in. 24-mm dimension parallel to the forging axis, will give adesirable combination of resolution and beam width on large sections 15 in. 380 mm in diameter or larger if solid or 7.5 in. 190mm or greater wall thickness if bored. A 1-in. 24-mm diameter, 2.0 or 2.25 MHz transducer may be used. If a
46、transducer withdimension circumferentially oriented to the forging, larger than 14 in. 6 mm is used, additional inspection at lower frequency isrecommended to provide a wide beam for off-axis inspection. A 0.5-in. 10-mm diameter 2.0 or 2.25 MHz transducer is suitablefor solid sections under 15 in. 3
47、80 mm in diameter and bored sections under 7.5 in. 190 mm in wall thickness. Themultiplication factors given are valid for the frequency and material velocity indicated provided they are used in the far field. (Thenear field is a characteristic that is dependent on the transducer frequency and size.
48、) For other frequencies and material velocities,applicable sensitivity multiplication factors shall be computed.6.4.1 Search Unit CalibrationThe transducers used in performing the tests described in this practice shall be calibrated inaccordance with GuidePractice E1065E1065/E1065M.7. Preparation of
49、 Forging for Ultrasonic Inspection7.1 Machine turn the forging to provide cylindrical surfaces for the radial test.7.2 The end faces of the shaft extensions and of the body of the forging shall be sufficiently perpendicular to the axis of theforging to permit axial test.7.3 The surface roughness of exterior finishes shall not exceed 250 in. 6.35 m where the definition for surface finish is asper Specification A788/A788M and the surface waviness shall not interfere with the ultrasonic test.7.4 At the time
