1、Designation: E1312 09 (Reapproved 2013)1Standard 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 of
2、original adoption or, 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.1NOTEChanges were made editorially in July 2013.1. Scope*1.1 This pract
3、ice covers procedures for eddy current exami-nation of hot ferromagnetic 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 linearthroughp
4、ut speeds up to 1200 ft/min (366 m/min). Larger orsmaller diameters 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 discontinuitie
5、s.1.3.1 The types of discontinuities capable of being detectedare 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 ag
6、reement between the usingparties.1.5 The values stated in inch-pound 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
7、 thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this practice to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for A
8、gencies Performing NondestructiveTestingE1316 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
9、 Standard:NAS 410 Certification and Qualification of NondestructiveTesting Personnel43. Terminology3.1 Standard terminology relating to electromagnetic testingmay be found in Terminology E1316, Section C: Electromag-netic Testing.4. Summary of Practice4.1 PrincipleThe major advantage of examining fe
10、rro-magnetic bar product above the Curie temperature with eddycurrents is the enhanced signal-to-noise ratio obtained withoutthe need for magnetic saturation.4.2 SensorsThis examination may be performed withvarious types or designs of encircling coils or with probe coilsthat are fixed or rotating.4.
11、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 the sensing and1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of
12、 Subcommittee E07.07 onElectromagnetic Method.Current edition approved July 15, 2013. Published August 2013. Originallyapproved in 1989. Last previous edition approved in 2009 as E1312 09. DOI:10.1520/E1312-09R13E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
13、 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 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org
14、.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho
15、cken, PA 19428-2959. United States1exciting 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 techn
16、ique is capable of examining 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,
17、 making it necessary 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 Discontin
18、uities cause either 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 de
19、gree of change in phase.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 pro
20、cedurefor in-line-eddy-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. Themeth
21、od is capable of detecting surface and some subsurfacediscontinuities that are typically in the order of 0.030 in. (0.75mm) and deeper, but some shallower discontinuities might alsobe found.5.3 Discontinuities that are narrow and deep, but short inlength, are readily detectable by both probe and enc
22、ircling coilsbecause 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
23、 length of cut length 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 coi
24、l are important param-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 pr
25、oduct.6. Basis of Application6.1 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-
26、CP-189, SNT-TC-1A, NAS-410, or a similar document and certified by the employer orcertifying agency, as applicable. The practice or standard usedand its applicable revision shall be identified in the contractualagreement between the using parties.6.2 Qualification of Nondestructive Testing AgenciesI
27、fspecified 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
28、 specified 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 equipmen
29、t should include 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 wi
30、ndings must 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 sens
31、or and areconnected to a cable and then to the preamplifier shield.7.2.3 Constant spacing, ranging from116 in. (1.6 mm) to14in. (6.4 mm) between the sensors and product surface isobtained with positioning mechanisms usually equipped withproduct guiding devices to prevent mechanical damage to thesens
32、ors.7.3 Transport 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 with
33、in the specified 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
34、 orpoor 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
35、g tolerances,E1312 09 (2013)12product 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 Refe
36、rence StandardIt 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 themat
37、erial being examined 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 dr
38、illed are either 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
39、 thediameter.7.4.3 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 t
40、he bar longitudinal 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
41、 examination.8.2.1 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 thi
42、s ratio increases.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 time
43、s.8.3.1 If the artificial 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 el
44、ectronic apparatus 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
45、 the system atproduction 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 pre
46、viously established 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
47、 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 discontinuitiesmay be used
48、 to adjust the sensitivity or to standardize thesystem.9. Procedure9.1 Standardization should be performed near the start ofeach working period (or diameter, grade, and so forth, change)and rechecked every4hormore frequent intervals.9.1.1 If improper system function occurs, all material thatpassed t
49、hrough the system since the last satisfactory standard-ization should be re-examined. Because bar product is notreheated and recoiled, electromagnetic inspection of recoiledor cut length cold bars is the only practical method forre-examination. However, different results may be obtainedbecause of changes in metallurgical characteristics between hotand cold product with the exception of austenitic steels.9.2 Pass all the material through the system for examinationat the sensitivity levels adjusted in accordance with Section 8.9.3 Any piece with discontinuities produ
