ASTM A388/A388M-23

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 made to the previous version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: A388/A388M − 19 A388/A388M − 23 Used in USNRC-RDT standards
Standard Practice for
Ultrasonic Examination of Steel Forgings
This standard is issued under the fixed designation A388/A388M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, 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 covers the examination procedures for the contact, pulse-echo ultrasonic examination of steel forgings by the
straight and angle-beam techniques. The straight beam techniques include utilization of the DGS (Distance Gain-Size) method. See
Appendix X3.
1.2 This practice is to be used whenever the inquiry, contract, order, or specification states that forgings are to be subject to
ultrasonic examination in accordance with Practice A388/A388M.
1.3 Supplementary requirements of an optional nature are provided for use at the option of the purchaser. The supplementary
requirements shall apply only when specified individually by the purchaser in the purchase order or contract.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.5 This specificationpractice and the applicable material specifications are expressed in both inch-pound units and SI units.
However, unless the order specifies the applicable “M” specification designation [SI units], the material shall be furnished to
inch-pound units.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A469/A469M Specification for Vacuum-Treated Steel Forgings for Generator Rotors
A745/A745M Practice for Ultrasonic Examination of Austenitic Steel Forgings
This practice is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.06
on Steel Forgings and Billets.
Current edition approved Sept. 1, 2019Nov. 1, 2023. Published September 2019November 2023. Originally approved in 1955. Last previous edition approved in 20182019
as A388/A388MA388/A388M – 19.–18. DOI: 10.1520/A0388_A0388M–19.10.1520/A0388_A0388M-23.
For ASME Boiler and Pressure Vessel Code applications see related Specification SA-388/SA-388M in Section II of that Code.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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
A388/A388M − 23
A788/A788M Specification for Steel Forgings, General Requirements
E317 Practice for Evaluating Performance Characteristics of Ultrasonic Pulse-Echo Testing Instruments and Systems without the
Use of Electronic Measurement Instruments
E428 Practice for Fabrication and Control of Metal, Other than Aluminum, Reference Blocks Used in Ultrasonic Testing
(Withdrawn 2019)
E1065/E1065M Practice for Evaluating Characteristics of Ultrasonic Search Units
E1316 Terminology for Nondestructive Examinations
2.2 Other Documents:
ASME Boiler and Pressure Vessel Code
Recommended Practice for Nondestructive Personnel Qualification and Certification SNT-TC-1A, (1988 or later)
3. Terminology
3.1 Definitions of Terms—For definitions of terms used in this standard that are not included in 3.2, refer to Terminology E1316.
3.2 Definitions:
3.2.1 indication levels (clusters), n—five or more indications in a volume representing a 2 in. [50 mm] or smaller cube in the
forging.
3.2.2 individual indications, n—single indications showing a decrease in amplitude as the search unit is moved in any direction
from the position of maximum amplitude and which are too small to be considered traveling or planar.
The last approved version of this historical standard is referenced on www.astm.org.
Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
www.asme.org.
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
A388/A388M − 23
3.2.3 planar indications, n—indications shall be considered continuous over a plane if they have a major axis greater than 1 in.
[25 mm] or twice the major dimension of the transducer, whichever is greater, and do not travel.
3.2.4 traveling indications, n—indications whose leading edge moves a distance equivalent to 1 in. [25 mm] or more of metal
depth with movement of the transducer over the surface of the forging.
4. Significance and Use
4.1 This practice shall be used when ultrasonic inspection is required by the order or specification for inspection purposes where
the acceptance of the forging is based on limitations of the number, amplitude, or location of discontinuities, or a combination
thereof, which give rise to ultrasonic indications.
4.2 The ultrasonic quality level shall be clearly stated as order requirements.
5. Ordering Information
5.1 When this practice is to be applied to an inquiry, contract, or order, the purchaser shall so state and shall also furnish the
following information:
5.1.1 Designation number (including year date),
5.1.2 Method of establishing the sensitivity in accordance with 9.2.2 and 9.3.3 (DGS (Distance Gain Size), Vee- or
rectangular-notch),
5.1.2.1 The diameter and test metal distance of the flat-bottom hole and the material of the reference block in accordance with
9.2.2.2,
5.1.3 Quality level for the entire forging or portions thereof in accordance with 12.3, and
5.1.4 Any options in accordance with 1.5, 6.4, 6.5, 7.1, 8.1, 8.2, 9.1.11, 10.1, 10.2, and 12.2.
6. Apparatus
6.1 Electronic Apparatus—An ultrasonic, pulsed, reflection type of instrument shall be used for this examination. The system shall
have a minimum capability for examining at frequencies from 11 MHz to 5 MHz. On examining austenitic stainless forgings the
system shall have the capabilities for examining at frequencies down to 0.4 MHz.
6.1.1 Apparatus Qualification and Calibration—Basic qualification of the ultrasonic test instrument shall be performed at intervals
not to exceed 12 months or whenever maintenance is performed that affects the equipment function. The date of the last calibration
and the date of the next required calibration shall be displayed on the test equipment.
6.1.2 The ultrasonic instrument shall provide linear presentation (within 5 %) for at least 75 % of the screen height (sweep line
to top of screen). The 5 % linearity referred to is descriptive of the screen presentation of amplitude. Instrument linearity shall be
verified in accordance with the intent of Practice E317. Any set of blocks processed in accordance with Practice E317 or E428 may
be used to establish the specified 65 % instrument linearity.
6.1.3 The electronic apparatus shall contain an attenuator (accurate over its useful range to 610 % (+1 dB) of the amplitude ratio)
which will allow measurement of indications beyond the linear range of the instrument.
2 2
1 1
6.2 Search Units, having a transducer with a maximum active area of 1 in. [650 mm ] with ⁄2 in. [13 mm] minimum to 1 ⁄8 in.
[30 mm] maximum dimensions shall be used for straight-beam scanning (see 9.2); and search units having a transducer with ⁄2
in. [13 mm] minimum to 1 in. [25 mm] maximum dimensions shall be used for angle-beam scanning (see 9.3).
6.2.1 Transducers shall be utilized at their rated frequencies.
6.2.2 Other transducers may be used for evaluating and pinpointing indications.
A388/A388M − 23
6.3 Couplants, having good wetting characteristics such as SAE No. 20 or No. 30 motor oil, glycerin, pine oil, or water shall be
used. Couplants may not be comparable to one another and the same couplant shall be used for calibration and examination.
6.4 Reference Blocks, containing flat-bottom holes may be used for calibration of equipment in accordance with 6.1.2 and may
be used to establish recording levels for straight-beam examination when so specified by the order or contract.
6.5 DGS Scales, matched to the ultrasonic test unit and transducer to be utilized, may be used to establish recording levels for
straight or angle beam examination, when so specified by the order or contract. The DGS scale range must be selected to include
the full thickness cross-section of the forging to be examined. An example of a DGS overlay is found in Appendix X3.
6.5.1 As an alternative to using DGS overlays, an ultrasonic instrument having DGS software, integral decibel gain or attenuator
controls in combination with a specifically paired transducer and DGS diagram may be used to evaluate ultrasonic indications.
7. Personnel Requirements
7.1 Personnel performing the ultrasonic examinations to this practice shall be qualified and certified in accordance with a written
procedure conforming to Recommended Practice No. SNT-TC-1A (1988 or later) or another national standard that is acceptable
to both the purchaser and the supplier.
8. Preparation of Forging for Ultrasonic Examination
8.1 Unless otherwise specified in the order or contract, the forging shall be machined to provide cylindrical surfaces for radial
examination in the case of round forgings; the ends of the forgings shall be machined perpendicular to the axis of the forging for
the axial examination. Faces of disk and rectangular forgings shall be machined flat and parallel to one another.
8.2 The surface roughness of exterior finishes shall not exceed 250 μin. [6 μm] where the definition for surface finish is as per in
accordance with Specification A788/A788M unless otherwise shown on the forging drawing or stated in the order or the contract.
8.3 The surfaces of the forging to be examined shall be free of extraneous material such as loose scale, paint, dirt, and so forth.
9. Procedure
9.1 General:
9.1.1 As far as practicable, subject the entire volume of the forging to ultrasonic examination. Because of radii at change of
sections and other local configurations, it may be impossible to examine some sections of a forging.
9.1.2 Perform the ultrasonic examination after heat treatment for mechanical properties (exclusive of stress-relief treatments) but
prior to drilling holes, cutting keyways, tapers, grooves, or machining sections to contour. If the configuration of the forging
required for the treatment for mechanical properties prohibits a subsequent complete examination of the forging, it shall be
permissible to examine prior to treatment for mechanical properties. In such cases, reexamine the forging ultrasonically as
completely as possible after heat treatment.
9.1.3 To ensure complete coverage of the forging volume, index the search unit with at least 15 % overlap with each pass.
9.1.4 For manual scanning, do not exceed a scanning rate of 6 in./s [150 mm/s].
9.1.5 For automated scanning, adjust scanning speed or instrument repetition rate, or both, to permit detection of the smallest
discontinuities referenced in the specification and to allow the recording or signaling device to function. At no time shall the
scanning speed exceed the speed at which an acceptable calibration was made.
9.1.6 If possible, scan all sections of forgings in two perpendicular directions.
9.1.7 Scan disk forgings using a straight beam technique from at least one flat face and radially from the circumference, whenever
practicable.
A388/A388M − 23
9.1.8 Scan cylindrical sections and hollow forgings radially using a straight-beam technique. When practicable, also examine the
forging in the axial direction.
9.1.9 In addition, examine hollow forgings by angle-beam technique from the outside diameter surface as required in 9.3.1.
9.1.10 In rechecking or reevaluation by manufacturer or purchaser, use comparable equipment, search units, frequency, and
couplant.
9.1.11 Forgings may be examined either stationary or while rotating in a lathe or on rollers. If not specified by the purchaser, either
method may be used at the manufacturer’s option.
9.2 Straight-Beam Examination:
9.2.1 For straight-beam examination use a nominal 2 ⁄4 MHz MHz search unit whenever practicable; however, 1 MHz is the
preferred frequency for coarse grained austenitic materials and long testing distances. In many instances on examining coarse
grained austenitic materials it may be necessary to use a frequency of 0.4 MHz. Other frequencies may be used if desirable for
better resolution, penetrability, or detectability of flaws.
9.2.2 Establish the instrument sensitivity by either the reflection, reference-block technique, or DGS method (see Appendix X3
for an explanation of the DGS method).
9.2.2.1 Back-Reflection Technique (Back-Reflection Calibration Applicable to Forgings with Parallel Entry and Back Surfaces)—
Use the back reflection from the opposite side of the part as a calibration standard to set the sensitivity for the test. The two surfaces
(entry surface and the reflecting surface) must be parallel to each other. Place the transducer in an area of the forging, when
possible, so that the geometry will not have an effect on the beam spread. Increase the gain to obtain a 75 % full screen height
back reflection, increase the gain by up to an additional 20 dB (10:1). If no indications are present (indication free) return the gain
to the original dB setting of the 75 % full screen height (1:1), this will be the reference level. Scanning should be done at a level
greater than the reference level, such as 6 dB (2:1). During the scanning, the back reflection shall be monitored for any significant
loss of amplitude not attributed to the geometry. Carry out the evaluation of discontinuities with the gain control set at the reference
level (75 % full screen height). Recalibration is required for significant changes in section thickness or diameter.
NOTE 1—High sensitivity levels are not usually employed when inspecting austenitic steel forgings due to attendant high level of “noise” or “hash” caused
by coarse grain structure.
9.2.2.2 Reference-Block Calibration—The test surface roughness on the calibration standard shall be comparable to, but no better
than, the item to be examined. Adjust the instrument controls to obtain the required signal amplitude from the flat-bottom hole in
the specified reference block. Utilize the attenuator in order to set up on amplitudes larger than the vertical linearity of the
instrument. In those cases, remove the attenuation prior to scanning the forging.
NOTE 2—When flat-surfaced reference block calibration is specified, adjust the amplitude of indication from the reference block or blocks to compensate
for examination surface curvature (an example is given in Appendix X1).
9.2.2.3 DGS Calibration—Prior to use, verify that the DGS overlay or electronic DGS curve matches the transducer size and
frequency. Accuracy of the overlay can be verified by reference blocks and procedures outlined in Practice E317. Overlays are to
be serialized to match the ultrasonic transducer and pulse echo testing system that they are to be utilized with. Instruments with
electronic DGS must use the specified ultrasonic transducer for that electronic curve.
(1) Electronic DGS—Modern test instruments with DGS software are particularly easy to calibrate. Most ultrasonic test
instruments with DGS software have 13 standard probes and corresponding DGS diagrams stored in the instrument. There are also
custom settings by which the operator may program their own data sets. The operator may choose from flat bottomed hole, side
drilled hole or back reflection to use for calibration. The instructions from the test instruments operator’s manual for DGS
calibration must be followed to properly calibrate the instrument. Operator errors are largely excluded due to the display of on
screen messages.
(2) Upon input of all necessary parameters for the flaw evaluation, the corresponding curve will be electronically displayed on
the instrument screen. This method of calibration may be used for longitudinal (single and dual) and shear wave examination.
9.2.2.4 Choose the appropriate DGS scale for the cross-sectional thickness of the forging to be examined. Insert the overlay over
A388/A388M − 23
the CRT screen, ensuring the DGS scale base line coincides with the sweep line of the CRT screen. Place the probe on the forging,
adjust the gain to make the first back-wall echo appear clearly on CRT screen. Using the Delay and Sweep control, shift the screen
pattern so that the leading e
...