1、Designation: E 1312 09Standard Practice forElectromagnetic (Eddy-Current) Examination ofFerromagnetic Cylindrical Bar Product Above the CurieTemperature1This standard is issued under the fixed designation E 1312; the number immediately following the designation indicates the year oforiginal adoption
2、 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.1. Scope1.1 This practice covers procedures for eddy-current exami-nation of hot ferroma
3、gnetic bars above the Curie temperaturewhere the product is essentially nonmagnetic, but below2100F (1149C).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 1200 ft/min (366 m/min). Larger orsmaller diameters
4、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 co
5、mmonly 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-pound
6、 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 therespo
7、nsibility 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:2E 543 Specification for Agencies Performing Nondestruc-tive TestingE 1316 Terminology for No
8、ndestructive 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 Certi-fication of NDT Personnel32.3 AIA Standard:NAS 410 Certification and Qualification of Nondestruct
9、iveTesting Personnel43. Terminology3.1 Standard terminology relating to electromagnetic ex-amination may be found in Terminology E 1316, Section C:Electromagnetic Testing.4. Summary of Practice4.1 PrincipleThe major advantage of examining ferro-magnetic bar product above the Curie temperature with e
10、ddycurrents 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.4.2.1 One or more exciter or sensor coils is used to encircle
11、the bar through which the product to be examined is passed.When the hot bar is in close proximity to 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 disrupti
12、ons inthe normal flux pattern indicate the presence of discontinuities.This technique 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 in1This practice is u
13、nder the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.07 onElectromagnetic Method.Current edition approved June 1, 2009. Published July 2009. Originally approvedin 1989. Last previous edition approved in 2004 as E 1312 - 99(2004)1
14、.2For referenced ASTM standards, 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 (
15、ASNT), P.O. Box28518, 1711 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Bo
16、x C700, West Conshohocken, PA 19428-2959, United States.close proximity to the product surface. The probe is usuallysmall and does not encircle the product, making it necessary torotate either the probes or the product to obtain 100 % coverageof the circumference. This is essentially a contact techn
17、iquebecause 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 a change in phase orsignal amplitude when detected by the sensing coil. Thesesignals are amplified and processed to activate
18、 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 phase.4.2.4 Caution must be exercised in establishing referencestandards because flux changes caused by natural discontinui-ti
19、es 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-eddy-current examination of hot cylindrical bars inthe range of diameters listed in 1.2 for large and repetitivediscontinuitie
20、s 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 detecting surface and some subsurfacediscontinuities that are typically in the order of 0.030 in. (0.75mm) and deeper, but some
21、 shallower discontinuities might alsobe found.5.3 Discontinuities that are narrow and deep, but short inlength, are readily detectable by both probe and encircling coilsbecause they cause abrupt flux changes. Surface and subsur-face discontinuities (if the electromagnetic frequency providessufficien
22、t 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 length bars orextend for extensive linear distances in coiled product may notalways be detected when encircling coils are used. T
23、hese 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 param-eters in coil design because they influence the detectability ofdiscontinuities.5.4 The eddy current method is sensitive t
24、o metallurgicalvariations that occur as a result of processing, thus all receivedsignals above the alarm level are not necessarily indicative ofdefective product.6. Basis of Application6.1 Personnel QualificationIf specified in the contractualagreement, personnel performing examinations to this prac
25、ticeshall be qualified in accordance with a nationally recognizednondestructive testing (NDT) personnel qualification practiceor standard such as ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, or a similar document and certified by the employer orcertifying agency, as applicable. The practice or standard use
26、dand its applicable revision shall be identified in the contractualagreement between the using parties.6.2 Qualification of Nondestructive Testing AgenciesIfspecified in the contractual agreement, NDT agencies shall bequalified and evaluated as described in Practice E 543. Theapplicable edition of P
27、ractice E 543 shall be specified in thecontractual agreement.6.3 Acceptance CriteriaSince acceptance criteria are notspecified in this practice, they shall be specified in thecontractual agreement.7. Apparatus7.1 Electronic Apparatus, should be capable of energizingthe test coils or probes with alte
28、rnating current at selectablefrequencies from 400 Hz to 100 kHz. Either manual orremotely operated switches can be used for frequency selec-tion. The equipment should include a detector display (CRT,meters), phase discriminator, filters, modulators, recorders, andalarming/marking devices required fo
29、r 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 must be cooled (such as waterjackets) to control the sensor operating temperature and pre-vent thermal damage to the sensors.7.2.2 Magn
30、etic or electrostatic shields might be necessary tosuppress extraneous electrical transient noise. Electrostaticshields usually float above ground at the sensor 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) betwe
31、en the sensors and product surface isobtained with positioning mechanisms usually equipped withproduct guiding devices to prevent mechanical damage to thesensors.7.3 Transport MechanismA conveyor or other type ofmechanical device should be employed to pass the productthrough or past the sensors. It
32、should operate at production (orsystem) speeds with a minimum vibration of the sensors orproduct, and should maintain alignment of the sensors andproduct within the specified tolerances. Some systems mayrequire the transport to rotate either the bar, the sensors, orboth.7.3.1 The mechanical toleranc
33、es for restraining the longitu-dinal centerline of the product relative to the coils are criticalto obtain an effective electromagnetic examination. Non-uniform sensitivity, the generation of erroneous signals or poorsignal-to-noise ratios result when the product and encirclingcoil are not concentri
34、c 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 rolling tolerances,product straightness, and conveyor alignment or roll wear arefactors that may in
35、fluence 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 is impractical to use a referencestandard heated to the same temperature as the material bein
36、gexamined 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 examined and of sufficient length to span theE1312092transport system rolls while passing through
37、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 partially or completely throughthe diameter.7.4.2 Notches should be inserted on the c
38、ircumference 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.7.4.3 The dimensions of holes or notches (hole diameter anddepth, notch width length, dep
39、th) 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 longitudinal axis with sufficientspacing to ensure that each is detected without interferencefr
40、om 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.8.2.1 Adjust the apparatus to obtain a signal-to-noise ratiothat allows the operator to d
41、ifferentiate 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.8.2.2 The amplitude or phase may be adjusted to trigger analarm from each artificial
42、 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 artificial discontinuities are located near one ofthe ends, the standard also should be
43、 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 apparatus should include a suppressioncircuit to prevent system response from the ends of the
44、standard 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 atproduction speeds a minimum of four times with the productrotated 90 degrees after each
45、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 established toler-ances are satisfied.8.4.1 An alternative method is to fabricate the standard
46、 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
47、.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 to adjust the sensitivity or to standardize thesystem.9. Procedure9.1 Standardization should be perfo
48、rmed near the start ofeach working period (or diameter, grade, and so forth, change)and rechecked at4hormore frequent intervals.9.1.1 If improper system function occurs, all material thatpassed through the system since the last satisfactory standard-ization should be re-examined. Because bar product
49、 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 producing responsesabove the alarm level should be marked and set aside forfurther evaluation or disposition, or bot
