ASTM A418-99(2003)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
Designation: A 418 – 99 (Reapproved 2003)
Standard Test Method for
Ultrasonic Examination of Turbine and Generator Steel
Rotor Forgings
This standard is issued under the fixed designation A 418; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope should be recognized as a possibility. Rigid control of the
actual frequency used, the coil bandpass width if tuned
1.1 This test method for ultrasonic examination applies to
instruments are used, etc. tend to reduce the overall inaccuracy
turbine and generator steel rotor forgings covered by Specifi-
which is apt to develop.
cations A293, A469, and A470. This standard shall be used
1.5 This test method for inspection applies to solid cylin-
for contact testing only.
drical forgings having outer diameters of not less than 2.5 in.
1.2 This test method describes a basic procedure of ultra-
(63.5 mm) nor greater than 100 in. (2540 mm). It also applies
sonically inspecting turbine and generator rotor forgings. It
tocylindricalforgingswithconcentriccylindricalboreshaving
shallinnowayrestricttheuseofotherultrasonicmethodssuch
wall thicknesses of 2.5 (63.5 mm) in. or greater, within the
asreferenceblockcalibrationswhenrequiredbytheapplicable
same outer diameter limits as for solid cylinders. For solid
procurement documents nor is it intended to restrict the use of
sections less than 15 in. (381 mm) in diameter and for bored
new and improved ultrasonic test equipment and methods as
cylinders of less than 7.5 in. (190.5 mm) wall thickness the
they are developed.The procedure utilizes different calibration
transducer used for the inspection will be different than the
techniques than had been used in previous issues. The fre-
transducer used for larger sections.
quency or amplitudes of recordable indications should not be
1.6 This standard does not purport to address all of the
interpreted necessarily as a change in quality of the product
safety concerns, if any, associated with its use. It is the
being examined.
responsibility of the user of this standard to establish appro-
1.3 This test method is intended to provide a means of
priate safety and health practices and determine the applica-
inspectingcylindricalforgingssothattheinspectionsensitivity
bility of regulatory limitations prior to use.
at the forging center line or bore surface is constant, indepen-
dent of the forging or bore diameter. To this end, inspection
2. Referenced Documents
sensitivity multiplication factors have been computed from
2.1 The reference is to the latest issue of these designations
theoretical analysis, with experimental verification. These are
that appear in the Annual Book of ASTM Standards or are
plotted in Fig. 1 (bored rotors) and Fig. 2 (solid rotors), for a
available as separate reprints. It shall also apply to product
true inspection frequency of 2.25 MHz, and an acoustic
5 5
specifications, which may be issued when specifically refer-
velocity of 2.30 3 10 in./s (5.85 3 10 cm/s). Means of
enced therein.
converting to other sensitivity levels are provided in Fig. 3.
2.2 ASTM Standards:
(Sensitivitymultiplicationfactorsforotherfrequenciesmaybe
A293 Specification for Steel Forgings, Carbon and Alloy,
derived in accordance with X1.1 and X1.2 of Appendix X1.)
for Turbine Rotors and Shafts
1.4 Considerableverificationdataforthismethodhavebeen
A469 Specification for Vacuum-Treated Steel Forgings for
generated which indicate that even under controlled conditions
Generator Rotors
very significant uncertainties may exist in estimating natural
A470 Specification for Vacuum-Treated Carbon and Alloy
discontinuities in terms of minimum equivalent size flat-
Steel Forgings for Turbine Rotors and Shafts
bottom holes. The possibility exists that the estimated mini-
E 317 Practice for Evaluating Performance Characteristics
mum areas of natural discontinuities in terms of minimum
of Ultrasonic Pulse-Echo Examination Instruments and
areas of the comparison flat-bottom holes may differ by 20 dB
Systems Without the Use of Electronic Measurement
(factorof10)intermsofactualareasofnaturaldiscontinuities.
Instruments
This magnitude of inaccuracy does not apply to all results but
1 2
This test method is under the jurisdiction of ASTM Committee A01 on Steel, For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Stainless Steel and RelatedAlloys, and is the direct responsibility of Subcommittee contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
A01.06 on Steel Forgings and Billets. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2003. Published November 2003. Originally the ASTM website.
approved in 1957. Last previous edition approved in 1999 as A418–99. Withdrawn.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
A 418 – 99 (2003)
NOTE—Sensitivity multiplication factor such that a 10% indication at the forging bore surface will be equivalent to a ⁄8 in. (3.175 mm) diameter flat
5 5
bottom hole. Inspection frequency: 2.25 MHz. Material velocity: 2.30 3 10 in./s (5.85 3 10 cm/s).
FIG. 1 Bored Forgings
E 1065 Guide for Evaluating Characteristics of Ultrasonic 4.2 The ultrasonic inspection shall be performed after final
Search Units heat treatment of the forging. In those cases in which wheels,
slots, or similar features are machined into the forging before
3. Application
heat treatment, the entire forging shall be inspected ultrasoni-
3.1 This test method shall be used when ultrasonic inspec- cally before such machining, and as completely as practicable
tion is required by the order or specification for inspection after the final heat treatment.
purposes where the acceptance of the forging is based on 4.3 For overall scanning, the ultrasonic beam shall be
limitations of the number, amplitude or location of disconti- introducedradially.Toconformwiththisrequirement,external
nuities or a combination thereof, which give rise to ultrasonic conical surfaces of the forging shall be replaced by stepped
indications. surfacesinordertomaintaintheultrasonicbeamperpendicular
3.2 The acceptance criteria shall be clearly stated as order to the longitudinal axis. Such stepped surfaces shall be shown
requirements. on the forging drawing.
4.4 Forgingsmaybetestedeitherstationaryorwhilerotated
4. General Requirements
bymeansofalatheorrollers.Ifnotspecifiedbythepurchaser,
4.1 Asfaraspossible,theentirevolumeoftheforgingshall either method may be used at the manufacturer’s option.
be subjected to ultrasonic inspection. Because of fillets at Scanning speed shall not exceed 6 in./s (15.24 cm/s).
stepdownsandotherlocalconfigurations,itmaybeimpossible 4.5 To ensure complete coverage of the forging volume, the
to inspect some small portions of a forging. search unit shall be indexed approximately 75% of the
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
A 418 – 99 (2003)
NOTE—Sensitivity multiplication factor such that a 10 % indication at the forging centerline surface will be equivalent to a ⁄8 in. (3.175 mm) diameter
5 5
flat bottom hole. Inspection frequency: 2.25 MHz. Material velocity: 2.30 3 10 in./s (5.85 3 10 cm/s).
FIG. 2 Solid Forgings
transducerwidthwitheachpassofthesearchunit.Mechanized SNT-TC-1A or another national standard that is acceptable to
inspection of the rotating forging wherein the search unit is both the purchaser and the supplier.
mechanically controlled is an aid in meeting this requirement.
4.6 Frequencies of 1, 2.25, and 5 MHz may be used for 6. Pulsed Ultrasonic Reflection Equipment and
accurately locating, determining orientation, and defining spe- Accessories
cific discontinuities detected during overall scanning as de-
6.1 Electronic Apparatus—Apulse-echoinstrumentpermit-
scribed in 4.4.
ting inspection frequencies of 1 MHz, 2.25 MHz, and 5 MHz
4.7 Axial scanning, if required, shall be performed at that
is required. The accuracy of discontinuity amplitude analysis
frequency and transducer diameter which minimizes interfer-
using this test method involves a knowledge of the true
ing ultrasonic reflections due to forging geometry and which
operating frequency of the complete inspection system. One of
gives optimum resolution. (Axial tests are normally used as a
thebestwaystoobtainthedesiredaccuracyisbyuseofatuned
supplement to radial tests.)
pulser and narrow band amplifier of known frequency re-
sponse, with either a broad-band transducer, or a narrow-band
5. Personnel Requirements
tuned transducer of known and matching frequency.
5.1 Personnelperformingtheultrasonicexaminationstothis 6.1.1 Apparatus Qualification and Calibration—Basic
practice shall be qualified and certified in accordance with a qualification of the ultrasonic test instrument shall be per-
written procedure conforming to Recommended Practice No. formed at intervals not to exceed 12 months or whenever
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
A 418 – 99 (2003)
FIG. 3 Conversion Factors to Be Used in Conjunction with Fig. 1 and Fig. 2 if a Change in the Reference Reflector Diameter is
Required
maintenance is performed that affects the equipment function. decrease of the higher order reflections is the greater of 65%
Thedateofthelastcalibrationandthedateofthenextrequired of the expected back reflection height or 62% of full screen
height.
calibration shall be displayed on the test equipment.
6.3 Signal Attenuator—The instrument shall contain a cali-
6.1.2 Thehorizontallinearityshallbecheckedonadistance
brated gain control or signal attenuator that meets the require-
calibrationbarusingthemultipleordertechnique.SeePractice
ments of Practice E317 (in each case, accurate within 65%)
E317. The horizontal linearity shall be 62 % of the metal
that will allow indications beyond the linear range of the
path.
instrument to be measured. It is recommended that these
6.1.3 If the rotor has a coupling or similar thin axial section
controls permit signal adjustments up to 25 to 1 (28 dB). See
with parallel sides, the accuracy of the linearity shall be
Fig. 1 and Fig. 2.
checked by ultrasonically verifying the thickness of the cou-
6.4 Search Units—Longitudinal wave search units of
pling or axial section. If necessary, minor adjustments for
known effective frequency should be used for radial scanning.
differences in the ultrasonic velocities between the calibration
A ⁄4 by 1 in. (6.35 by 25.4 mm) 2.25 MHz transducer, used
bar and the forging shall then be made.
with the 1 in. dimension parallel to the forging axis, will give
6.2 Amplifier—The amplifier and the cathode ray tube shall
a desirable combination of resolution and beam width on large
providelinearresponsewithin 62%,upto100%offullscreen
sections15in.(381mm)indiameterorlargerifsolidor7.5in.
height.
(190.5 mm) or greater wall thickness if bored. A 1 in. (25.4
6.2.1 Amplifier Calibration—An amplifier vertical linearity
mm) diameter, 2.25 MHz transducer may be used. If a
check shall be made prior to performing the test by observing
transducer with dimension circumferentially oriented to the
a multiple order pattern from a calibration block using a 2.25 1
forging, larger than ⁄4 in. (6.35 mm) is used, additional
MHz transducer. See Practice E317. The first back reflection
inspection at lower frequency is recommended to provide a
shall be set at 100% of full screen height. The higher order
wide beam for off-axis inspection. A0.5 in. (12.7 mm) diam-
back reflections, 10% and higher in amplitude, shall also be
eter2.25MHztransducerissuitableforsolidsectionsunder15
positioned on the screen and their amplitudes noted. The first
in. (381 mm) in diameter and bored sections under 7.5 in.
back reflection shall be reduced to 50% and then 25% of full
(190.5 mm) in wall thickness.The multiplication factors given
screen height. The amplitudes of the higher order back reflec-
are valid for the frequency and material velocity indicated
tions shall be noted at each step. The vertical linearity will be
provided they are used in the far field. (The near field is a
considered acceptable if the signal heights of the higher order characteristicthatisdependentonthetransducerfrequencyand
reflections decrease in proportion to the decrease set for the
size.) For other frequencies and material velocities, applicable
first back reflection. The maximum acceptable error for the sensitivity multiplication factors shall be computed.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
A 418 – 99 (2003)
6.4.1 Search Unit Calibration—The transducers used in unit on the surface of the forging when indications are
performing the tests described in this test method shall be observed so that they may be investigated in accordance with
calibrated in accordance with Guide E1065. 8.1.7 and 8.2.2.
8.1.6 When the forgings are tested while they are rotated,
the maximum speed of rotation shall be calculated as follows:
7. Preparation of Forging for Ultrasonic Inspection
7.1 Machine turn the forging to provide cylindrical surfaces
for the radial test.
360/pd = maximum revolutions per min.
7.2 The end faces of the shaft extensions and of the body of
d = diameter of forging in inches.
the forging shall be sufficiently perpendicular to the axis of the 915/pd = maximum revolutions per min.
forging to permit axial test. d = diameter of forging in centimetres.
The search unit may be held by a suitable fixture attached to
7.3 The surface roughness of exterior finishes shall not
the tool post of the lathe and traversed mechanically for
exceed 250 µin. (6.35 µm) and the surface waviness shall not
scanning of the rotating forging or may be hand-held. If not
interfere with the ultrasonic test.
specified by the purchaser, either method may be used at the
7.4 At the time of ultrasonic testing, the surfaces of the
manufacturer’s option.
forging shall be free of tool tears, loose s
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