Designation:A388/A388M–03Used in USNRC-RDT standards
An American National Standard
Standard Practice for
Ultrasonic Examination of Heavy Steel Forgings1
This standard is issued under thefixed 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(e)indicates an editorial change since the last revision or reapproval.
1.Scope*
1.1This practice2covers 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(Dis-tance Gain-Size)method.See Appendix X3.
1.2This 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.
1.3The 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 inde-pendently of the other.Combining values from the two systems may result in nonconformance with the specification.
1.4This specification and the applicable material specifica-tions are expressed in both inch-pound units and SI units. However,unless the order specifies the applicable“M”speci-fication designation[SI units],the material shall be furnished to inch-pound units.
1.5This 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
2.Referenced Documents
2.1ASTM Standards:
A469Specification for Vacuum-Treated Steel Forgings for Generator Rotors3
A745/A745M Practice for Ultrasonic Examination of Aus-tenitic Steel Forgings3
E317Practice for Evaluating Performance Characteristics
of Ultrasonic Pulse-Echo Examination Instruments and Systems Without the Use of Electronic Measurement Instruments4
E428Practice for Fabrication and Control of Steel Refer-ence Blocks Used in Ultrasonic Inspection4
2.2ANSI Standard:
B46.1Surface Texture5
2.3Other Document:
Recommended Practice for Nondestructive Personnel Quali-fication and Certification SNT-TC-1A,Supplement C—Ultrasonic Testing6
3.Ordering Information
3.1When this practice is to be applied to an inquiry, contract,or order,the purchaser shall so state and shall also furnish the following information:
3.1.1Method of establishing the sensitivity in accordance with7.2.2and7.3.3(Vee or rectangular notch),
3.1.1.1The diameter and test metal distance of theflat-bottom hole and the material of the reference block in accordance with7.2.2.2,
3.1.2Quality level for the entire forging or portions thereof in accordance with10.3,and
3.1.3Any options in accordance with6.1,6.2,and7.1.11.
4.Apparatus
4.1An ultrasonic,pulsed,reflection type of instrument shall be used for this examination.The system shall have a mini-mum capability for examining at frequencies from1to5MHz. On examining austenitic stainless forgings the system shall have the capabilities for examining at frequencies down to0.4 MHz.
4.1.1The ultrasonic instrument shall provide linear presen-tation(within5%)for at least75%of the screen height (sweep line to top of screen).The5%linearity referred to is descriptive of the screen presentation of amplitude.Instrument linearity shall be verified in accordance with the intent of
1This practice is under the jurisdiction of ASTM Committee A01on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.06on Steel Forgings and Billets.
Current edition approved April10,2003.Published June2003.Originally published as A388–55T.Last previous edition A388/A388M–01.
2For ASME Boiler and Pressure Vessel Code applications see related Specifi-cation SA-388/SA-388M in Section II of that Code.
3Annual Book of ASTM Standards,V ol01.05.
4Annual Book of ASTM Standards,V ol03.03.
5Available from the American National Standards Institute,Inc.,25W.43rd Street,4thfloor,New York,NY10036.
6Available from the American Society for Nondestructive Testing,1711Arlin-gate Ln.,P.O.Box28518,Columbus,OH43228–0518.
1
*A Summary of Changes section appears at the end of this standard. Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
Practice E317.Any set of blocks processed in accordance with Practice E317or E428may be used to establish the specified 65%instrument linearity.
4.1.2The electronic apparatus shall contain an attenuator (accurate over its useful range to610%(+1dB)of the amplitude ratio)which will allow measurement of indications beyond the linear range of the instrument.
4.2Search Units,having a transducer with a maximum active area of1in.2[650mm2]with3⁄4in.[20mm]minimum to11⁄8in.[30mm]maximum dimensions shall be used for straight-beam scanning(see7.2);and search units equipped from1⁄2by1in.[13by25mm]to1by1in.[25by25mm] shall be used for angle-beam scanning(see7.3).
4.2.1Transducers shall be utilized at their rated frequencies.
4.2.2Other search units may be used for evaluating and pinpointing indications.
4.3Couplants,having good wetting characteristics such as SAE No.20or No.30motor 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.
4.4Reference Blocks,containingflat-bottom holes may be used for calibration of equipment in accordance with4.1.1and may be used to establish recording levels for straight-beam examination when so specified by the order or contract.
4.5DGS Scales,matched to the ultrasonic test unit and transducer to be utilized,may be used to establish recording levels for straight beam examination,when so specified by the order or contract.Th
e 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.
5.Personnel Requirements
5.1Personnel 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 or another national standard that is acceptable to both the purchaser and the supplier.
6.Preparation of Forging for Ultrasonic Examination 6.1Unless 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 machinedflat and parallel to one another.
6.2The surface roughness of exteriorfinishes shall not exceed250µin.[6µm]unless otherwise shown on the forging drawing or stated in the order or the contract.
6.3The surfaces of the forging to be examined shall be free of extraneous material such as loose scale,paint,dirt,and so forth.
7.Procedure
7.1General:
7.1.1As 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.
7.1.2Perform the ultrasonic examination after heat treat-ment 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.
7.1.3To ensure complete coverage of the forging volume, index the search unit with at least15%overlap with each pass.
7.1.4For manual scanning,do not exceed a scanning rate of 6in./s[150mm/s].
7.1.5For 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.
7.1.6If possible,scan all sections of forgings in two perpendicular directions.
7.1.7Scan disk forgings using a straight beam technique from at least oneflat face and radially from the circumference, whenever practicable.
7.1.8Scan cylindrical sections and hollow forgings radially using a straight-beam technique.When practicable,also exam-ine the forging in the axial direction.
7.1.9In addition,examine hollow forgings by angle-beam technique from the outside diameter surface as required in 7.3.1.
7.1.10In rechecking or reevaluation by manufacturer or purchaser use comparable equipment,search units,frequency, and couplant.
7.1.11Forgings may be examined either stationary or while rotating in a lathe or on rollers.If not specifi
ed by the purchaser,either method may be used at the manufacturer’s option.
7.2Straight-Beam Examination:
7.2.1For straight-beam examination use a nominal21⁄4 -MHz search unit whenever practicable;however,1MHz 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 of0.4MHz.Other frequencies may be used if desirable for better resolution,penetrability,or detectability of flaws.
7.2.2Establish the instrument sensitivity by either the reflection,reference-block technique,or DGS method(see Appendix X3for an explanation of the DGS method).
7.2.2.1Back-Reflection Technique(Back-Reflection Cali-bration Applicable to Forgings with Parallel Entry and Back Surfaces)—With the attenuator set at an appropriate level,for example5to1or14dB,adjust the instrument controls to obtain a back reflection approximately75%of the full-screen height from the opposite side of the forging.Scan the
forging
at the maximum amplification setting of the attenuator(attenu-ator set at1to1).Carry out the evaluation of discontinuities with the gain control set at the reference level.Recalibration is required for significant changes in section thickness or diam-eter.
N OTE1—High sensitivity levels are not usually employed when in-specting austenitic steel forgings due to attendant high level of“noise”or “hash”caused by coarse grain structure.
7.2.2.2Reference-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 theflat-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.
N OTE2—Whenflat-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).
7.2.2.3DGS Calibration—Prior to use,verify that the DGS overlay 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.
7.2.2.4Choose the appropriate DGS scale for the cross-sectional thickness of the forging to be examined.Insert the overlay over 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 thefirst backwall echo appear clearly on CRT screen.Using the Delay and Sweep control,shift the screen pattern so that the leading edge of the initial pulse is on zero of the DGS scale and the backwall echo is on the DGS scale value corresponding to the thickness of the forging.Adjust the gain so the forging backwall echo matches the height of the DGS reference slope within61Db. Once adjusted,increase the gain by the Db shown on the DGS scale for the reference slope.Instrument is now calibrated and flaw sizes that can be reliably detected can be directly read from the CRT screen.Theseflaw sizes are the equivalentflat bottom reflector that can be used as a reference point.
N OTE3—The above can be utilized on all solid forgings.Cylindrical hollow forgings,and drilled or bored forgings must be corrected to compensate for attenuation due to the central hole(see Appendix
X4).
7.2.3Recalibration—Any change in the search unit,cou-plant,instrument setting,or scanning speed from that used for calibration shall require recalibration.Perform a calibration check at least once every8h shift.When a loss of15%or greater in the gain level is indicated,reestablish the required calibration and reexamine all of the material examined in the preceding calibration period.When an increase of15%or greater in the gain level is indicated,reevaluate all recorded indications.
7.2.4During the examination of the forging,monitor the back reflection for any significant reduction in amplitude. Reduction in back-reflection amplitude may indicate not only the presence of a discontinuity but also poor coupling of the search unit with the surface of the forging,nonparallel back-reflection surface,or local variations of attenuation in the forging.Recheck any areas causing loss of back reflection.
7.3Angle-Beam Examination—Rings and Hollow Forgings: 7.3.1Perform the examination from the circumference of rings and hollow forgings that have an axial length greater than 2in.[50mm]and an outside to inside diameter ratio of less than2.0to1.
7.3.2Use a1MHz,45°angle-beam search unit unless thickness,OD/ID ratio,or other geometric configura
tion results in failure to achieve calibration.Other frequencies may be used if desirable for better resolution,penetrability,or detectability offlaws.For angle-beam inspection of hollow forgings up to 2.0to1ratio,provide the transducer with a wedge or shoe that will result in the beam mode and angle required by the size and shape of the cross section under examination.
7.3.3Calibrate the instrument for the angle-beam examina-tion to obtain an indication amplitude of approximately75% full-screen height from a rectangular or a60°V-notch on inside diameter(ID)in the axial direction and parallel to the axis of the forging.A separate calibration standard may be used; however,it shall have the same nominal composition,heat treatment,and thickness as the forging it represents.The test surfacefinish on the calibration standard shall be comparable but no better than the item to be examined.Where a group of identical forgings is made,one of these forgings may be used as the separate calibration standard.Cut the ID notch depth to 3%maximum of the thickness or1⁄4in.[6mm],whichever is smaller,and its length approximately1in.[25mm].Thickness is defined as the thickness of the forging to be examined at the time of examination.At the same instrument setting,obtain a reflection from a similar OD notch.Draw a line through the peaks of thefirst reflections obtained from the ID and OD notches.This shall be the amplitude reference line.It is preferable to have the notches in excess metal or test metal when possible.When the OD notch cannot be detected when
examining the OD surface,perform the examination when practicable(some ID’s may be too small to permit examina-tion),as indicated above from both the OD and ID surfaces. Utilize the ID notch when inspecting from the OD,and the OD notch when inspecting from the ID.Curve wedges or shoes may be used when necessary and practicable.
7.3.4Perform the examination by scanning over the entire surface area circumferentially in both the clockwise and counter-clockwise directions from the OD surface.Examine forgings,which cannot be examined axially using a straight beam,in both axial directions with an angle-beam search unit. For axial scanning,use rectangular or60°V-notches on the ID and OD for the calibration.These notches shall be perpendicu-lar to the axis of the forging and the same dimensions as the axial notch.
8.Recording
8.1Straight-Beam Examination—Record the following in-dications as information for the purchaser.These recordable indications do not constitute a rejectable condition unless negotiated as such in the purchase
order.
8.1.1In the back-reflection technique,individual indications equal to or exceeding10%of the back reflection from an adjacent area free from indications;in the reference-block or DGS technique,indications equal to or exceeding100%of the reference amplitude.
8.1.2An indication that is continuous on the same plane regardless of amplitude,and found over an area larger than twice the diameter of the search unit.The extent of such an indication shall be accurately measured along with variations in amplitudes of reflections.
8.1.2.1Planar indications shall be considered continuous over a plane if they have a major axis greater than1in.[25 mm].In recording these indications corrections must be made for beam divergence at the estimatedflaw depth.
8.1.3In the back-reflection technique,discontinuity indica-tions equal to or exceeding5%of the back reflection.In the reference-block technique,indications equal to or exceeding 50%of the reference amplitude providing that they travel,are continuous,or appear as clusters.
8.1.3.1Traveling indications are herein defined as indica-tions whose leading edge moves a distance e
quivalent to1in. [25mm]or more of metal depth with movement of the search unit over the surface of the forging.
8.1.3.2A cluster of indications is defined asfive or more indications located in a volume representing a2-in.[50-mm]or smaller cube in the forging.
8.1.4Reduction in back reflection exceeding20%of the original measured in increments of10%.
8.1.5Amplitudes of recordable indications in increments of 10%.
8.2Angle-Beam Examination—Record discontinuity indi-cations equal to or exceeding50%of the indication from the reference line.When an amplitude reference line cannot be generated,record discontinuity indications equal to or exceed-ing50%of the reference notch.These recordable indications do not constitute a rejectable condition unless negotiated as such in the purchase order.
9.Report
9.1Report the following information:
9.1.1All recordable indications(see Section8).
9.1.2For the purpose of reporting the locations of record-able indications,a sketch shall be prepared showing the physical outline of the forging including dimensions of all areas not inspected due to geometric configuration,the pur-chaser’s drawing number,the purchaser’s order number,and the manufacturer’s serial number,and the axial,radial,and circumferential distribution of recordable ultrasonic indica-tions.
9.1.3The specification to which the examination was per-formed as well as the frequency used,method of setting sensitivity,type of instrument,surfacefinish,couplant,and search unit employed.
9.1.4The inspector’s signature and date examination per-formed.
10.Quality Levels
10.1This practice is intended for application to forgings, with a wide variety of sizes,shapes,compositions,melting processes,and applications.It is,therefore,impracticable to specify an ultrasonic quality level which would be universally applicable to such a diversity of products.Ultrasonic accep-tance or rejection criteria for individual forgings should be based on a realistic appraisal of service requirements and the quality that can normally be obtained in the production of the particular type forging.
10.2Heavy austenitic stainless steel forgings are more difficult to penetrate ultrasonically than similar carbon or low-alloy steel forgings.The degree of attenuation normally increases with section size;and the noise level,generally or in isolated areas,may become too great to permit detection of discrete indications.In most instances,this attenuation results from inherent coarse grained microstructure of these austenitic alloys.For these reasons,the methods and standards employed for ultrasonically examining carbon and low-alloy steel forg-ings may not be applicable to heavy austenitic steel forgings.In general,only straight beam inspecting using a back-reflection reference standard is used.However,utilization of Practice A745/A745M for austenitic steel forgings can be considered ifflat bottom hole reference standards or angle beam exami-nation of these grades are required.
10.3Acceptance quality levels shall be established between purchaser and manufacturer on the basis of one or more of the following criteria.
10.3.1Straight-Beam Examination:
10.3.1.1No indications larger than some percentage of the reference back reflection.
10.3.1.2No indications equal to or larger than the indication received form theflat-bottom hole in a specific reference block or blocks.
10.3.1.3No areas showing loss of back reflection larger than some percentage of the reference back reflection.
10.3.1.4No indications per10.3.1.1or10.3.1.2coupled with some loss of resultant back reflection per10.3.1.3. 10.3.1.5No indications exceeding the reference level speci-fied in the DGS method
10.3.2Angle-Beam Examination—No indications exceed-ing a stated percentage of the reflection from a reference notch or of the amplitude reference line.
10.4Intelligent application of ultrasonic quality levels in-volves an understanding of the effects of many parameters on examination results.
11.Keywords
11.1angle beam examination;back-reflection;DGS;refer-ence–block;straight beam examination;
ultrasonic
SUPPLEMENTARY REQUIREMENTS
The following supplementary requirements shall apply only when specified by the purchaser in the inquiry,contract,or order.Details shall be agreed upon by the manufacturer and the purchaser.
S1.Reporting Criteria
S1.1Reference block calibration shall be performed using at least three holes,spaced to approximate minimum,mean, and maximum thickness as tested,and shall be used to generate a distance amplitude correction(DAC)curve.The following hole sizes apply:
1.1⁄16in.[1.5mm]flat bottom holes(FBH)for thicknesses less
than1.5in.[40mm]
2.1⁄8in.[3mm]FBH for thicknesses of1.5-6in.[40-150mm]
inclusive
3.1⁄4in.[6mm]FBH for thicknesses over6in.[150mm]
S1.2Reporting criteria include:
1.All indications exceeding the DAC curve
2.Two or more indications separated by1⁄2in.[12mm]or less
APPENDIXES
(Nonmandatory Information)
X1.TYPICAL TUNING LEVEL COMPENSATION FOR THE EFFECTS OF FORGING CURV ATURE X1.1The curve(Fig.X1.1)was determined for the follow-
ing test conditions:
Material nickel-molybdenum-vanadium alloy steel
(Specification A469,Class4)
Instrument Type UR Reflectoscope
Search unit11⁄8-in.[30mm]diameter quartz
Frequency21⁄4MHz
Reference block ASTM No.3-0600(aluminum)
Reflection area of refer-ence curve 0.010in.2[6.5mm2]in nickel-molybdenum-vana-dium alloy steel
Surfacefinish250µin.[6µm],max,roughness
X1.2To utilize curve,adjust reflectoscope sensitivity to
obtain indicated ultrasonic response on ASTM No.3-0600
reference block for each diameter as shown.A response of1in.
[25mm]sweep-to-peak is used forflat surfaces.Use attenuator
to obtain desired amplitude,but do testing at1to1setting.
X2.INDICATION AMPLITUDE COMPENSATION FOR TEST DISTANCE V ARIATIONS X2.1The curve(Fig.X2.1)has been determined for the
following test conditions:
Material nickel-molybdenum-vanadium alloy steeleditorial英文
(Specification A469,Class4)
Instrument Type UR Reflectoscope
Search unit11⁄8-in.[30mm]diameter quartz
Frequency21⁄4MHz
Couplant No.20oil
Reference block ASTM No.3-0600(aluminum)
Reflection area of refer-ence curve 0.010in.2[65mm2]in nickel-molybdenum-vana-dium alloy steel
Surfacefinish250µin.max,roughness
X2.2To utilize curve,establish amplitude from ASTM reference block to coincide with values from Appendix
X1.FIG.X1.1Typical Compensation Curve for Effects of Forging
Curvature
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