1、Designation: E1312 18Standard Practice forElectromagnetic (Eddy Current) Examination ofFerromagnetic Cylindrical Bar Product Above the CurieTemperature1This standard is issued under the fixed designation E1312; the number immediately following the designation indicates the year oforiginal adoption o
2、r, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers procedures for eddy current exami-nation of hot ferromag
3、netic bars above the Curie temperaturewhere the product is essentially nonmagnetic, but below2100 F (1149 C).1.2 This practice is intended for use on bar products havingdiameters of12 in. (12.7 mm) to 8 in. (203 mm) at linearthroughput speeds up to 24 000 ft/min (122 m/sec). Larger orsmaller diamete
4、rs may be examined by agreement between theusing parties.1.3 The purpose of this practice is to provide a procedure forin-line eddy current examination of bars during processing forthe detection of major or gross surface discontinuities.1.3.1 The types of discontinuities capable of being detectedare
5、 commonly referred to as: slivers, laps, seams, roll-ins(scale, dross, and so forth), and mechanical damage such asscratches, scores, or indentations.1.4 This practice does not establish acceptance criteria.They must be specified by agreement between the usingparties.1.5 The values stated in inch-po
6、und units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.6 This practice does not purport to address all of thesafety concerns, if any, associated with its use. It is there
7、sponsibility of the user of this practice to establish appro-priate safety, health, environmental practices and determinethe applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-izatio
8、n established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestructiv
9、eTestingE1316 Terminology for Nondestructive Examinations2.2 Other Documents:SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive Testing3ANSI/ASNT-CP-189 Standard for Qualification and Certifi-cation of NDT Personnel32.3 AIA Standard:NAS 410 Certification
10、and Qualification of NondestructiveTesting Personnel42.4 International Standards:5ISO 9712 Non-Destructive TestingQualification and Cer-tification of NDT Personnel3. Terminology3.1 Standard terminology relating to electromagnetic testingmay be found in Terminology E1316, Section C: Electromag-netic
11、Testing.4. Summary of Practice4.1 PrincipleThe major advantage of examining ferro-magnetic bar product above the Curie temperature with eddycurrents is the enhanced signal-to-noise ratio obtained withoutthe need for magnetic saturation.1This practice is under the jurisdiction of ASTM Committee E07 o
12、n Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Method.Current edition approved June 1, 2018. Published June 2018. Originallyapproved in 1989. Last previous edition approved in 2013 as E1312 09(2013)1.DOI: 10.1520/E1312-18.2For referenced ASTM stan
13、dards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711
14、 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.5Available from International Organization for Standardization (ISO), ISOCentral Secr
15、etariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international s
16、tandard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14.
17、2 SensorsThis examination may be performed withvarious types or designs of encircling coils or with probe coilsthat are fixed or rotating.4.2.1 One or more exciter or sensor coils is used to encirclethe bar through which the product to be examined is passed.When the hot bar is in close proximity to
18、the sensing andexciting coils, eddy currents are induced in the hot product byan alternating current. The sensing coil detects the electromag-netic flux related to these currents. Changes or disruptions inthe normal flux pattern indicate the presence of discontinuities.This technique is capable of e
19、xamining the entire circumfer-ence without contacting the product.4.2.2 The surface can also be examined with probe coilshaving one or more exciters and sensors which are spaced inclose proximity to the product surface. The probe is usuallysmall and does not encircle the product, making it necessary
20、 torotate either the probes or the product to obtain 100 % coverageof the circumference. This is essentially a contact techniquebecause the coil is fixtured in a device that rides on thecircumference to maintain a fixed distance between the coil andproduct surface.4.2.3 Discontinuities cause either
21、a change in phase orsignal amplitude when detected by the sensing coil. Thesesignals are amplified and processed to activate marking orrecording devices, or both. Relative severity of the imperfec-tion can be indicated by the signal amplitude generated by theflux change or the degree of change in ph
22、ase.4.2.4 Caution must be exercised in establishing referencestandards because flux changes caused by natural discontinui-ties might differ significantly from those generated by artificialdiscontinuities.5. Significance and Use5.1 The purpose of this practice is to describe a procedurefor in-line-ed
23、dy-current examination of hot cylindrical bars inthe range of diameters listed in 1.2 for large and repetitivediscontinuities that may form during processing.5.2 The discontinuities in bar product capable of beingdetected by the electromagnetic method are listed in 1.3.1. Themethod is capable of det
24、ecting surface and some subsurfacediscontinuities that are typically in the order of 0.030 in.(0.75 mm) and deeper, but some shallower discontinuitiesmight also be found.5.3 Discontinuities that are narrow and deep, but short inlength, are readily detectable by both probe and encircling coilsbecause
25、 they cause abrupt flux changes. Surface and subsur-face discontinuities (if the electromagnetic frequency providessufficient effective depth of penetration) can be detected by thismethod.5.3.1 Discontinuities such as scratches or seams that arecontinuous and uniform for the full length of cut lengt
26、h bars orextend for extensive linear distances in coiled product may notalways be detected when encircling coils are used. These aremore detectable with probe coils by intercepting the disconti-nuity in their rotation around the circumference.5.3.2 The orientation and type of coil are important para
27、m-eters in coil design because they influence the detectability ofdiscontinuities.5.4 The eddy current method is sensitive to metallurgicalvariations that occur as a result of processing, thus all receivedsignals above the alarm level are not necessarily indicative ofdefective product.6. Basis of Ap
28、plication6.1 Personnel QualificationIf specified in the contractualagreement, personnel performing examinations to this practiceshall be qualified in accordance with a nationally recognizednondestructive testing (NDT) personnel qualification practiceor standard such as ANSI/ASNT-CP-189, SNT-TC-1A, N
29、AS-410, ISO-9712, or a similar document and certified by theemployer or certifying agency, as applicable. The practice orstandard used and its applicable revision shall be identified inthe contractual agreement between the using parties.6.2 Qualification of Nondestructive Testing AgenciesIfspecified
30、 in the contractual agreement, NDT agencies shall bequalified and evaluated as described in Practice E543. Theapplicable edition of Practice E543 shall be specified in thecontractual agreement.6.3 Acceptance CriteriaSince acceptance criteria are notspecified in this practice, they shall be specified
31、 in thecontractual agreement.7. Apparatus7.1 Electronic Apparatus, should be capable of energizingthe test coils or probes with alternating current at selectablefrequencies from 400 Hz to 100 kHz. Either manual orremotely operated switches can be used for frequency selec-tion. The equipment should i
32、nclude a detector display (CRT,meters), phase discriminator, filters, modulators, recorders, andalarming/marking devices required for particular applications.7.2 Sensors, whether probe or encircling coils, should op-erate through a frequency range from 400 Hz to 100 kHz.7.2.1 The sensor windings mus
33、t be cooled (such as waterjackets) to control the sensor operating temperature and pre-vent thermal damage to the sensors.7.2.2 Magnetic or electrostatic shields might be necessary tosuppress extraneous electrical transient noise. Electrostaticshields usually float above ground at the sensor and are
34、connected to a cable and then to the preamplifier shield.7.2.3 Constant spacing, ranging from116 in. (1.6 mm) to14 in. (6.4 mm) between the sensors and product surface isobtained with positioning mechanisms usually equipped withproduct guiding devices to prevent mechanical damage to thesensors.7.3 T
35、ransport MechanismA conveyor or other type ofmechanical device should be employed to pass the productthrough or past the sensors. It should operate at production (orsystem) speeds with a minimum vibration of the sensors orproduct, and should maintain alignment of the sensors andproduct within the sp
36、ecified tolerances. Some systems mayrequire the transport to rotate either the bar, the sensors, orboth.7.3.1 The mechanical tolerances for restraining the longitu-dinal centerline of the product relative to the coils are critical.Non-uniform sensitivity, the generation of erroneous signals orE1312
37、182poor signal-to-noise ratios result when the product and encir-cling coil are not concentric or the probe coil clearance changesduring examination. Therefore, the system passline mecha-nisms must be properly designed and maintained to achieve thespatial arrangement defined in 7.2.3. Product rollin
38、g tolerances,product straightness, and conveyor alignment or roll wear arefactors that may influence sensor and product spatial relations.The system sensitivity profile predicated on the passlinecapabilities can be determined by utilizing the standardizationprocedure in 8.4.7.4 Reference StandardIt
39、is impractical to use a referencestandard heated to the same temperature as the material beingexamined because of reoxidation, furnace time, etc. Therefore,a material with nonmagnetic properties, such as 304 stainlesssteel, is substituted. It should be of the same diameter as thematerial being exami
40、ned and of sufficient length to span thetransport system rolls while passing through or past the sensorsat the same speed and under the same conditions as theproduct. The standard usually has one of the following types ofartificial discontinuities on the circumference.7.4.1 Holes drilled are either
41、partially or completely throughthe diameter.7.4.2 Notches should be inserted on the circumference byelectric discharge machining, milling, or other methods. Theymay be either transverse or parallel to the longitudinal axis ofthe bar. Notch depths are usually given as a percentage of thediameter.7.4.
42、3 The dimensions of holes or notches (hole diameter anddepth, notch width length, depth) are either specified or agreedto between the using parties to establish sensitivity levelsand/or acceptance criteria.7.4.4 The notches or holes should be placed on the circum-ference and along the bar longitudin
43、al axis with sufficientspacing to ensure that each is detected without interferencefrom a neighbor.8. System Standardization8.1 Fabricate the reference standard in accordance with thespecification.8.2 Pass the standard through the system at speeds andconditions simulating production examination.8.2.
44、1 Adjust the apparatus to obtain a signal-to-noise ratiothat allows the operator to differentiate between the signalsfrom the system ambient noise and those produced by discon-tinuities. Although the minimum recommended signal-to-noiseratio is 2:1, system reliability improves as this ratio increases
45、.8.2.2 The amplitude or phase may be adjusted to trigger analarm from each artificial imperfection as it passes by thesensors.8.3 After the sensitivity adjustments are completed, thestandard should be traversed through the coils or probessimulating production conditions several times.8.3.1 If the ar
46、tificial discontinuities are located near one ofthe ends, the standard also should be passed through the systemby reversing the leading and trailing ends.8.3.2 The system alarm or markers, or both, should indicateevery specified artificial discontinuity during each pass.8.3.3 The electronic apparatu
47、s should include a suppressioncircuit to prevent system response from the ends of thestandard and cut-to-length bar product.8.4 The capability of the passline mechanism to maintainthe correct distance between the bar surface and coils can bedetermined by passing the standard through the system atpro
48、duction speeds a minimum of four times with the productrotated 90 degrees after each pass. If more passes are used, theangular rotation should be reduced accordingly. The responsesobtained from the artificial discontinuity can be used to plot asensitivity profile to determine if previously establish
49、ed toler-ances are satisfied.8.4.1 An alternative method is to fabricate the standard withfour or more duplicate artificial discontinuities distributedequally around the circumference and separated sufficientlyalong the longitudinal axis to produce signals without interfer-ence from a neighbor. In this case, the standard must be passedthrough the system one time at production speeds.8.5 If acceptable by specification and/or agreement betweenthe purchaser, manufacturer or supplier, electronically gener-ated signals simulating responses from artificial discontinuities
