ASTM A388/A388M-95(2000)
(Practice)Standard Practice for Ultrasonic Examination of Heavy Steel Forgings
Standard Practice for Ultrasonic Examination of Heavy Steel Forgings
SCOPE
1.1 This practice covers the examination procedures for the contact, pulse-echo ultrasonic examination of heavy 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 The values stated in either inch-pound or SI units are to be regarded as the standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
1.4 This specification 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.
1.5 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: A 388/A 388M – 95 (Reapproved 2000) Used in USNRC-RDT standards
An American National Standard
Standard Practice for
Ultrasonic Examination of Heavy Steel Forgings
This standard is issued under the fixed designation A 388/A 388M; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope ence Blocks Used in Ultrasonic Inspection
2.2 ANSI Standard:
1.1 This practice covers the examination procedures for the
B 46.1 Surface Texture
contact, pulse-echo ultrasonic examination of heavy steel
2.3 Other Document:
forgings by the straight and angle-beam techniques. The
Recommended Practice for Nondestructive Personnel Quali-
straight beam techniques include utilization of the DGS (Dis-
fication and Certification SNT-TC-1A, Supplement
tance Gain-Size) method. See Appendix X3.
C—Ultrasonic Testing
1.2 This practice is to be used whenever the inquiry,
contract, order, or specification states that forgings are to be
3. Ordering Information
subject to ultrasonic examination in accordance with Practice
3.1 When this practice is to be applied to an inquiry,
A 388/A 388M.
contract, or order, the purchaser shall so state and shall also
1.3 The values stated in either inch-pound or SI units are to
furnish the following information:
be regarded as the standard. Within the text, the SI units are
3.1.1 Method of establishing the sensitivity in accordance
shown in brackets. The values stated in each system are not
with 7.2.2 and 7.3.3 (Vee or rectangular notch),
exact equivalents; therefore, each system must be used inde-
3.1.1.1 The diameter and test metal distance of the flat-
pendently of the other. Combining values from the two systems
bottom hole and the material of the reference block in
may result in nonconformance with the specification.
accordance with 7.2.2.2,
1.4 This specification and the applicable material specifica-
3.1.2 Quality level for the entire forging or portions thereof
tions are expressed in both inch-pound units and SI units.
in accordance with 10.3, and
However, unless the order specifies the applicable “M” speci-
3.1.3 Any options in accordance with 6.1, 6.2, and 7.1.10.
fication designation [SI units], the material shall be furnished
to inch-pound units.
4. Apparatus
1.5 This standard does not purport to address all of the
4.1 An ultrasonic, pulsed, reflection type of instrument shall
safety concerns, if any, associated with its use. It is the
be used for this examination. The system shall have a mini-
responsibility of the user of this standard to establish appro-
mum capability for examining at frequencies from 1 to 5 MHz.
priate safety and health practices and determine the applica-
On examining austenitic stainless forgings the system shall
bility of regulatory limitations prior to use.
have the capabilities for examining at frequencies down to 0.4
MHz.
2. Referenced Documents
4.1.1 The ultrasonic instrument shall provide linear presen-
2.1 ASTM Standards:
tation (within 5 %) for at least 75 % of the screen height
A 469 Specification for Vacuum-Treated Steel Forgings for
3 (sweep line to top of screen). The 5 % linearity referred to is
Generator Rotors
descriptive of the screen presentation of amplitude. Instrument
A 745/A 745M Practice for Ultrasonic Examination of Aus-
3 linearity shall be verified in accordance with the intent of
tenitic Steel Forgings
Practice E 317. Any set of blocks processed in accordance with
E 317 Practice for Evaluating Performance Characteristics
Practice E 317 or E 428 may be used to establish the specified
of Ultrasonic Pulse-Echo Testing Systems Without the Use
4 6 5 % instrument linearity.
of Electronic Measurement Instruments
4.1.2 The electronic apparatus shall contain an attenuator
E 428 Practice for Fabrication and Control of Steel Refer-
(accurate over its useful range to 6 10 % (+1 dB) of the
amplitude ratio) which will allow measurement of indications
This practice is under the jurisdiction of ASTM Committee A01 on Steel,
beyond the linear range of the instrument.
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee
4.2 Search Units, having a transducer with a maximum
A01.06 on Steel Forgings and Billets.
Current edition approved Jan. 15, 1995. Published March 1995. Originally
published as A 388–55T. Last previous edition A 388–94.
2 5
For ASME Boiler and Pressure Vessel Code applications see related Specifi- Available from the American National Standards Institute, Inc., 11 West 42nd
cation SA-388/SA-388M in Section II of that Code. Street, 13th floor, New York, NY 10036.
3 6
Annual Book of ASTM Standards, Vol 01.05. Available from the American Society for Nondestructive Testing, 1711 Arlin-
Annual Book of ASTM Standards, Vol 03.03. gate Lane, P.O. Box 28518, Columbus, OH 43228–0518.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
A 388/A 388M
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active area of 1 in. [650 mm ] with ⁄4 in. [20 mm] minimum mechanical properties. In such cases, reexamine the forging
to 1 ⁄8 in. [30 mm] maximum dimensions shall be used for ultrasonically as completely as possible after heat treatment.
straight-beam scanning (see 7.2); and search units equipped 7.1.3 To ensure complete coverage of the forging volume,
from ⁄2 by 1 in. [13 by 25 mm] to 1 by 1 in. [25 by 25 mm] index the search unit with at least 15 % overlap with each pass.
shall be used for angle-beam scanning (see 7.3). 7.1.4 Do not exceed a scanning rate of 6 in./s [150 mm/s].
4.2.1 Transducers, shall be utilized at their rated frequen- 7.1.5 If possible, scan all sections of forgings in two
cies. perpendicular directions.
4.2.2 Other search units may be used for evaluating and 7.1.6 Scan disk forgings using a straight beam technique
pinpointing indications. from at least one flat face and radially from the circumference,
4.3 Couplants, having good wetting characteristics such as whenever practicable.
SAE No. 20 or No. 30 motor oil, glycerin, pine oil, or water 7.1.7 Scan cylindrical sections and hollow forgings by
shall be used. Couplants may not be comparable to one another angle-beam technique. When practicable, also examine the
and the same couplant shall be used for calibration and forging in the axial direction.
examination. 7.1.8 In addition, examine hollow forgings by angle-beam
4.4 Reference Blocks, containing flat-bottom holes may be technique from the outside diameter surface as required in
used for calibration of equipment in accordance with 4.1.1 and 7.3.1.
may be used to establish recording levels for straight-beam 7.1.9 In rechecking or reevaluation by manufacturer or
examination when so specified by the order or contract. purchaser use comparable equipment, search units, frequency,
4.5 DGS scales, matched to the ultrasonic test unit and and couplant.
transducer to be utilized, may be used to establish recording 7.1.10 Forgings may be examined either stationary or while
levels for straight beam examination, when so specified by the rotating in a lathe or on rollers. If not specified by the
order or contract. The DGS scale range must be selected to purchaser, either method may be used at the manufacturer’s
include the full thickness cross-section of the forging to be option.
examined. An example of a DGS overlay is found in Appendix 7.2 Straight-Beam Examination:
X3. 7.2.1 For straight-beam examination use a nominal 2 ⁄4-
MHz search unit whenever practicable; however, 1 MHz is the
5. Personnel Requirements
preferred frequency for coarse grained austenitic materials and
5.1 Personnel performing the ultrasonic examinations to this long testing distances. In many instances on examining coarse
practice shall be qualified and certified in accordance with a
grained austenitic materials it may be necessary to use a
written procedure conforming to Recommended Practice No. frequency of 0.4 MHz. Other frequencies may be used if
SNT-TC-1A or another national standard that is acceptable to
desirable for better resolution, penetrability, or detectability of
both the purchaser and the supplier. flaws.
7.2.2 Establish the instrument sensitivity by either the
6. Preparation of Forging for Ultrasonic Examination
reflection, reference-block technique, or DGS method (see
6.1 Unless otherwise specified in the order or contract, the
Appendix X3 for an explanation of the DGS method).
forging shall be machined to provide cylindrical surfaces for
7.2.2.1 Back-Reflection Technique (Back-Reflection Cali-
radial examination in the case of round forgings; the ends of
bration Applicable to Forgings with Parallel Entry and Back
the forgings shall be machined perpendicular to the axis of the
Surfaces)—With the attenuator set at an appropriate level, for
forging for the axial examination. Faces of disk and rectangular
example 5 to 1 or 14 dB, adjust the instrument controls to
forgings shall be machined flat and parallel to one another.
obtain a back reflection approximately 75 % of the full-screen
6.2 The surface roughness of exterior finishes shall not
height from the opposite side of the forging. Scan the forging
exceed 250 μin. [6 μm] unless otherwise shown on the forging
at the maximum amplification setting of the attenuator (attenu-
drawing or stated in the order or the contract.
ator set at 1 to 1). Carry out the evaluation of discontinuities
6.3 The surfaces of the forging to be examined shall be free
with the gain control set at the reference level. Recalibration is
of extraneous material such as loose scale, paint, dirt, etc.
required for significant changes in section thickness or diam-
eter.
7. Procedure
NOTE 1—High sensitivity levels are not usually employed when in-
7.1 General:
specting austenitic steel forgings due to attendant high level of “noise” or
7.1.1 As far as practicable, subject the entire volume of the
“hash” caused by coarse grain structure.
forging to ultrasonic examination. Because of radii at change
7.2.2.2 Reference-Block Calibration—The test surface
of sections and other local configurations, it may be impossible
roughness on the calibration standard shall be comparable to
to examine some sections of a forging.
but no better than the item to be examined. Adjust the
7.1.2 Perform the ultrasonic examination after heat treat-
instrument controls to obtain the required signal amplitude
ment for mechanical properties (exclusive of stress-relief
from the flat-bottom hole in the specified reference block.
treatments) but prior to drilling holes, cutting keyways, tapers,
Utilize the attenuator in order to set up on amplitudes larger
grooves, or machining sections to contour. If the configuration
than the vertical linearity of the instrument. In those cases,
of the forging required for the treatment for mechanical
remove the attenuation prior to scanning the forging.
properties prohibits a subsequent complete examination of the
forging, it shall be permissible to examine prior to treatment for NOTE 2—When flat-surfaced reference block calibration is specified,
A 388/A 388M
adjust the amplitude of indication from the reference block or blocks to
tion to obtain an indication amplitude of approximately 75 %
compensate for examination surface curvature (an example is given in
full-screen height from a rectangular or a 60° V-notch on inside
Appendix X1).
diameter (ID) in the axial direction and parallel to the axis of
the forging. A separate calibration standard may be used;
7.2.2.3 DGS Calibration—Prior to use, verify that the DGS
however, it shall have the same nominal composition, heat
overlay matches the transducer size and frequency. Accuracy
treatment, and thickness as the forging it represents. The test
of the overlay can be verified by reference blocks and
surface finish on the calibration standard shall be comparable
procedures outlined in Practice E 317. Overlays are to be
but no better than the item to be examined. Where a group of
serialized to match the ultrasonic transducer and pulse echo
identical forgings is made, one of these forgings may be used
testing system that they are to be utilized with.
as the separate calibration standard. Cut the ID notch depth to
7.2.2.4 Choose the appropriate DGS scale for the cross-
3 % maximum of the thickness or ⁄4 in. [6 mm], whichever is
sectional thickness of the forging to be examined. Insert the
smaller, and its length approximately 1 in. [25 mm]. Thickness
overlay over the CRT screen, ensuring the DGS scale base line
is defined as the thickness of the forging to be examined at the
coincides with the sweep line of the CRT screen. Place the
time of examination. At the same instrument setting, obtain a
probe on the forging, adjust the gain to make the first backwall
reflection from a similar OD notch. Draw a line through the
echo appear clearly on CRT screen. Using the Delay and
peaks of the first reflections obtained from the ID and OD
Sweep control, shift the screen pattern so that the leading edge
notches. This shall be the amplitude reference line. It is
of the initial pulse is on zero of the DGS scale and the backwall
preferable to have the notches in excess metal or test metal
echo is on the DGS scale value corresponding to the thickness
when possible. When the OD notch cannot be detected when
of the forging. Adjust the gain so the forging backwall echo
examining the OD surface, perform the examination when
matches the height of the DGS reference slope within 61 Db.
practicable (some ID’s may be too small to permit examina-
Once adjusted, increase the gain by the Db shown on the DGS
tion), as indicated above from both the OD and ID surfaces.
scale for the reference slope. Instrument is now calibrated and
Utilize the ID notch when inspecting from the OD, and the OD
flaw sizes that can be reliably detected can be directly read
notch when inspecting from the ID. Curve wedges or shoes
from the CRT screen. These flaw sizes are the equivalent flat
may be used when necessary and practicable.
bottom reflector that can be used as a reference point.
7.3.4 Perform the examination by scanning over the entire
NOTE 3—The above can be utilized on all solid forgings. Cylindrical
surface area circumferentially in both the clockwise and
hollow forgings, and drilled or bored forgings must be corrected to
counter-clockwise directions from the OD surface. Examine
compensate for attenuation due to the central hole (see Appendix X4).
forgings, which cannot be examined axially using a straight
7.2.3 Recalibration—Any change in the search unit, cou-
beam, in both axial directions with an angle-b
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