1、Designation: E2261/E2261M 12E2261/E2261M 17Standard Practice forExamination of Welds Using the Alternating Current FieldMeasurement Technique1This standard is issued under the fixed designation E2261/E2261M; the number immediately following the designation indicates the yearof original adoption or,
2、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 describes procedures to be followed during alternating current fie
3、ld measurement examination of welds forbaseline and service-induced surface breaking discontinuities.1.2 This practice is intended for use on welds in any metallic material.1.3 This practice does not establish weld acceptance criteria.1.4 UnitsThe values stated in either inch-pound units or SI units
4、 are to be regarded separately as standard. The values statedin each system might not be exact equivalents; therefore, each system shall be used independently of the other. Combining valuesfrom the two systems may result in nonconformance with the standard.1.5 This standard does not purport to addre
5、ss 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 applicability of regulatorylimitations prior to use.1.6 This international standard was developed in accordance
6、with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standard
7、s:2E543 Specification for Agencies Performing Nondestructive TestingE1316 Terminology for Nondestructive Examinations2.2 ASNT Standard:3SNT-TC-1A Personnel Qualification and Certification in Nondestructive TestingANSI/ASNT-CP-189 Standard for Qualification and Certification of Nondestructive Testing
8、 Personnel2.3 ISO Standard:4ISO 9712 Nondestructive TestingQualification and Certification of Nondestructive Testing Personnel3. Terminology3.1 DefinitionsFor definitions of terms relating to this practice refer to Terminology E1316, Section A, Common NDT terms,and Section C, Electromagnetic testing
9、. The following definitions are specific to the alternating current field measurementtechnique:3.2 Definitions:3.2.1 excitera device that generates a time varying electromagnetic field, usually a coil energized with alternating current(AC); also known as a transmitter.3.2.2 detectorone or more coils
10、 or elements used to sense or measure a magnetic field; also known as a receiver.1 This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.07 on ElectromagneticMethod.Current edition approved Nov. 1, 2012June 1, 201
11、7. Published November 2012June 2017. Originally approved in 2003. Last previous edition approved in 20072012 asE2261 - 07.E2261 - 12. DOI: 10.1520/E2261_E2261M-12.10.1520/E2261_E2261M-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceas
12、tm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.4 Available from International Organization f
13、or Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,Switzerland, http:/www.iso.org.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 previ
14、ous 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.*A Summary of Chan
15、ges section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.3 uniform fieldas applied to nondestructive testing with magnetic fields, the area of uniform magnetic field over the surfaceof the mat
16、erial under examination produced by a parallel induced alternating current, which has been passed through the weld andis observable beyond the direct coupling of the exciting coil.3.2.4 graduated fieldas applied to nondestructive testing with magnetic fields, a magnetic field having a controlled gra
17、dientin its intensity.3.3 Definitions of Terms Specific to This Standard:3.3.1 alternating current field measurement systemthe electronic instrumentation, software, probes, and all associatedcomponents and cables required for performing weld examination using the alternating current field measuremen
18、t technique.3.3.2 operational reference standarda reference standard with specified artificial slots, used to confirm the operation of thesystem.3.3.3 Bxthe x component of the magnetic field, parallel to the weld toe, the magnitude of which is proportional to the currentdensity set up by the electri
19、c field.3.3.4 Bzthe z component of the magnetic field normal to the inspected base metal/heat affected zone surface, the magnitudeof which is proportional to the lateral deflection of the induced currents in the plane of that surface.3.3.5 X-Y Plotan X-Y graph with two orthogonal components of magne
20、tic field plotted against each other.3.3.6 time base plotsthese plot the relationship between Bx or Bz values with time.3.3.7 surface plotfor use with array probes. This type of plot has one component of the magnetic field plotted over an area,typically as a color contour plot or 3-D wire frame plot
21、.3.3.8 data sample ratethe rate at which data is digitized for display and recording, in data points per second.3.3.9 configuration datastandardization data and instrumentation settings for a particular probe stored in a computer file.3.3.10 twin fieldsmagnetic fields generated in two orthogonal dir
22、ections by use of two excitersNOTE 1Different equipment manufacturers may use slightly different terminology. Reference should be made to the equipment manufacturersdocumentation for clarification.4. Summary of Practice4.1 In a basic alternating current field measurement system, a small probe is mov
23、ed along the toe of a weld. The probe containsan exciter coil, which induces anAC magnetic field in the material surface aligned to the direction of the weld. This, in turn, causesalternating current to flow across the weld. The depth of penetration of this current varies with material type and freq
24、uency butis typically 0.004 in. 0.1 mm deep in magnetic materials and 0.08 -to 0.3 in. 2 -to 7 mm deep in non-ferrous materials. Anysurface breaking discontinuities within a short distance of either side of the scan line at this location will interrupt or disturb theflow of the alternating current.
25、The maximum distance from the scan line to a target discontinuity, potentially detectable at aspecified probability of detection, is determined by the probe assembly size, but is typically 0.4 in 10 mm. Measurement of theabsolute quantities of the two major components of the surface magnetic fields
26、(Bx and Bz) determines the severity of thedisturbance (see Fig. 1) and thus the severity of the discontinuity. Discontinuity sizes, such as crack length and depth, can beestimated from key points selected from the Bx and Bz traces along with the standardization data and instrument settings from each
27、individual probe. This discontinuity sizing can be performed automatically using system software. Discontinuities essentiallyperpendicular to the weld may be detected (in ferritic metals only) by the flux leakage effect. However confirmation of suchtransverse discontinuities (and detection of the sa
28、me in non-ferritic metals) requires scans with the induced magnetic fieldperpendicular to the direction of the weld.4.2 Configuration data is loaded at the start of the examination. System sensitivity and operation is verified using an operationreference standard. System operation is checked and rec
29、orded prior to and at regular intervals during the examination. Note thatwhen a unidirectional input current is used, any decay in strength of the input field with probe lift-off or thin coating is relativelysmall so that variations of output signal (as may be associated with a discontinuity) are re
30、duced. If a thick coating is present, thenthe discontinuity size estimation must compensate for the coating thickness. The coating thickness requiring compensation is probedependent. This can be accomplished using discontinuity-sizing tables in the system software and an operator-entered coatingthic
31、kness or automatically if the equipment measures the coating thickness or stand-off distance during the scanning process. Usingthe wrong coating thickness would have a negative effect on depth sizing accuracy if the coating thickness discrepancy is too large.Data is recorded in a manner that allows
32、archiving and subsequent recall for each weld location. Evaluation of examination resultsmay be conducted at the time of examination or at a later date. The examiner generates an examination report detailing completeresults of the examination.5. Significance and Use5.1 The purpose of the alternating
33、 current field measurement method is to evaluate welds for surface breaking discontinuitiessuch as fabrication and fatigue cracks. The examination results may then be used by qualified organizations to assess weld serviceE2261/E2261M 172life or other engineering characteristics (beyond the scope of
34、this practice). This practice is not intended for the examination ofwelds for non-surface breaking discontinuities.6. Basis of Application6.1 Personnel Qualification:6.1.1 If specified in the contractual agreement, personnel performing examinations to this practice shall be qualified inaccordance wi
35、th a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNT-CP-189 or SNT-TC-1A or ANSI/ASNT-CP-189, SNT-TC-1A, ISO 9712, or a similar document and certified by the employer orcertifying agent, as applicable. The practice or standard used and its
36、applicable revision shall be identified in the contractualagreement between the using parties.6.2 Qualification of Nondestructive Evaluation Agenciesif specified in the contractual agreement, NDT agencies shall bequalified and evaluated as described in Practice E543, with reference to sections on el
37、ectromagnetic examination. The applicableedition of Practice E543 shall be specified in the contractual agreement.7. Job Scope and Requirements7.1 The following items may require agreement by the examining party and their client and should be specified in the purchasedocument or elsewhere:7.1.1 Loca
38、tion and type of welded component to be examined, design specifications, degradation history, previousnondestructive examination results, maintenance history, process conditions, and specific types of discontinuities that are requiredto be detected, if known.7.1.2 The maximum window of opportunity f
39、or work. (Detection of small discontinuities may require a slower probe scanspeed, or cleaning of surface, or both, which will affect productivity.)7.1.3 Size, material grade and type, and configuration of welds to be examined. If required by type of equipment chosen,thickness of coating and variati
40、on of coating thickness.7.1.4 A weld numbering or identification system.7.1.5 Extent of examination, for example: complete or partial coverage, which welds and to what length, whether straightsections only and the minimum surface curvature.7.1.6 Means of access to welds, and areas where access may b
41、e restricted.7.1.7 Type of alternating current field measurement instrument and probe; and description of operations referece standard used,including such details as dimensions and material.7.1.8 Required operator qualifications and certification.FIG. 1 Example Bx and Bz Traces as a Probe Passes Ove
42、r a Crack(The orientation of the traces may differ depending upon the instrumentation.)E2261/E2261M 1737.1.9 Required weld cleanliness.7.1.10 Environmental conditions, equipment and preparations that are the responsibility of the client; common sources of noisethat may interfere with the examination
43、.7.1.11 Complementary methods or techniques may be used to obtain additional information.7.1.12 Acceptance criteria to be used in evaluating discontinuities.7.1.13 Disposition of examination records and reference standards.7.1.14 Format and outline contents of the examination report.8. Interferences
44、8.1 This section describes items and conditions, which may compromise the alternating current field measurement technique.8.2 Material Properties:8.2.1 Although there are permeability differences in a ferromagnetic material between weld metal, heat affected zone and parentplate, the probe is normall
45、y scanned along a weld toe and so passes along a line of relatively constant permeability. If a probe isscanned across a weld then the permeability changes may produce indications, which could be similar to those from a discontinuity.Differentiation between a transverse discontinuity signal and the
46、weld signal can be achieved by taking further scans parallel tothe indication, or using an array probe. The signal from a discontinuity will die away quickly. If there is no significant change inindication amplitude at 0.8 in. 20 mm distance from the weld then the indication is likely due to the per
47、meability changes in theweld.8.3 Magnetic State:8.3.1 DemagnetizationIt must be ensured that the surface being examined is in the non-magnetized state. Therefore theprocedure followed with any previous magnetic technique deployed must include demagnetization of the surface. This is becauseareas of r
48、emnant magnetization, particularly where the leg of a magnetic particle examination yoke was sited, can produce loopsin the X-Y plot, which may sometimes be confused with a discontinuity indication.8.3.2 Grinding marksmagnetic permeability can also be affected by surface treatments such as grinding.
49、 These can causelocalized areas of altered permeability across the line of scan direction. The extent and pressure of any grinding marks shouldalways be reported by the probe operator, since these can give rise to strong indications in both Bx and Bz, which may be confusedwith a discontinuity indication. If a discontinuity is suspected in a region of grinding, further scans should be taken parallel butaway from the weld toe and perpendicular across the region of grinding. The indication from a linear discontinuity will die awayquickly away from the
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