1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (412) 772-8512 FAX: (412) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (412) 776-4970 FAX: (412) 776-0790http:www.sae.orgCopyright 1991 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001INFORMATIONREPORTSubmitted for recognition as an American National StandardJ349REV.FEB91I
4、ssued 1968-07Revised 1991-02Superseding J349 JUN80(R) DETECTION OF SURFACE IMPERFECTIONSIN FERROUS RODS, BARS, TUBES, AND WIRESForewordThis Document has not changed other than to put it into the new SAE Technical Standards BoardFormat.1. ScopeThis SAE Information Report provides a summary of several
5、 methods that are available for detecting,and in some instances detecting and measuring, surface imperfections in rods, bars, tubes, and wires.References relating to detailed technical information and to specific applications are enumerated in 2.2.2. References2.1 Applicable PublicationsThe followin
6、g publications form a part of the specification to the extent specifiedherein. Unless otherwise indicated the lastest revision of SAE publications shall apply.2.1.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J420Magnetic Particle InspectionSAE J425Eddy
7、Current Testing by Electromagnetic MethodsSAE J426Liquid Penetrant Test MethodsSAE J428Ultrasonic Inspection2.2 Related PublicationsThe following publications are provided for information purposes only and are not arequired part of this document.J. M. Mandula and E. S. Monk, “NDT Systems for Steel B
8、illets, Bars, and Tubes.“ Materials Evaluation,Vol. 34 (10), October 1976, pp. 230236.W. A. Black, “Evaluation of Surface Defects by Nondestructive Testing - A Progress Report.“ Journal ofMetals, October 1965, pp. 11361140.J. M. Mandula, “Billetscan - A New Eddy Current Device for Total Surface Insp
9、ection of Square Billets.“Materials Evaluation, Vol. 30 (3), March 1972, pp. 4954.T. W. Judd, “Orbitest for Round Tubes.“ Materials Evaluation, Vol. 28 (1), Jan. 1970, pp. 812.C. E. Betz, “Principles of Penetrants.“ Second Edition, Magnaflux Corporation, Chicago, IL.Metals Handbook, Ninth Edition, V
10、ol. 17, Nondestructive Evaluation and Quality Control, 1989, ASMInternational, Metals Park, OH 44073.W. J. McGonnagle, “Nondestructive Testing.“ Second Edition, Gordon and Breach, Science Publishers,Inc., New York, 1969.Copyright SAE International Provided by IHS under license with SAENot for Resale
11、No reproduction or networking permitted without license from IHS-,-,-SAE J349 Revised FEB91-2-R. C. McMaster, “Nondestructive Testing Handbook.“ Second Edition, Vol. 2, Liquid Penetrant Tests, 1982,ASM International, Metals Park, OH 44073.C. E. Betz, “Principles of Magnetic Particle Testing.“ Magnaf
12、lux Corporation, Chicago, IL, 1985.H. L. Libby, “Introduction to Electromagnetic Nondestructive Test Methods.“ John Wiley consequently, it will detect laps, seams, cracks, and similar surfaceimperfections without regard to their orientation. Good indications, however, are dependent upon surfaceclean
13、liness, and the ability of the imperfection to admit and retain the penetrating liquid.4.3 Magnetic Particle InspectionThe methods available, recommended usage for types of surfacediscontinuities, and inspection techniques are described in SAE J420. The sensitivity level to be achieved isdependent u
14、pon the system employed. Magnetic particle inspection is especially useful to find laps, seams,cracks, inclusions, and some mechanical flaws in ferromagnetic materials, but it has limited value wheninspecting for gouges and pits that are circular in nature or too broad to induce a magnetic leakage f
15、ield.Although a clean surface is important for satisfactory indications, the shape of the cross section andstraightness of the test specimens are inconsequential in obtaining satisfactory results. However, if magneticparticle inspection is to be applied to coiled materials, it must be performed on r
16、epresentative samples cut fromthe coils.4.4 ElectromagneticElectromagnetic methods are used for the detection of surface imperfections. Eddy currentand fringe flux techniques are discussed here. SAE J425 gives general information relative to the nature anduse of eddy currents in the broad field of n
17、ondestructive testing. This discussion gives additional informationon electromagnetic methods as they apply to the detection of surface imperfections in ferrous bars, tubes, rods,and wires.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking p
18、ermitted without license from IHS-,-,-SAE J349 Revised FEB91-3-A distinct advantage of electromagnetic testing is that it can give information as to the severity of surfaceimperfections. This makes it possible to establish a quality level of the material being tested by accepting thatwith imperfecti
19、on not detrimental to the end use of the material and by rejecting that with more severeimperfections. The minimum surface imperfection which can be detected by electromagnetic methods isdetermined by:a. The surface condition of the material;b. The type and size of the test coil used;c. The test fre
20、quency used;d. The discriminating capabilities of the test instrumentation;e. The smoothness of operation of the material handling equipment.4.4.1 EDDY CURRENTEddy current testing is a method of electromagnetic testing in which eddy current flow isinduced in the material under test by an exciting co
21、il energized with an alternating current. Changes in theflow caused by variations in the material are reflected into a sensing coil or coils for subsequent analysis bysuitable instrumentation and techniques.The principle of eddy current testing, simply stated, is mutual induction. Mutual induction i
22、s the developmentof an induced emf in one circuit by the change of current in another. Thus, if a piece of metal is placed in thefield of an exciting coil carrying alternating current, eddy currents will be induced in the metal.Testing is performed by passing the bar, rod, tube, or wire lengthwise t
23、hrough or near the inspection coil,which may contain separate exciting and sensing coils or a single coil that may be used for both purposes.The exciting coil is energized with alternating current of one or more frequencies. The electrical impedanceof the sensing coil is modified by the proximity of
24、 the material under test. The extent of this modification isdetermined by the distance between the coil and the material, and the electrical conductivity and magneticpermeability of the material. The presence of metallurgical or mechanical discontinuities on the surface ofthe material will alter the
25、 apparent electrical impedance of the coil. During passage of the material beingtested, the test coil induces eddy currents in the material and senses changes in amplitude and/or phase ofthese eddy currents. These changes produce electrical signals which are amplified and modified so as toactuate a
26、suitable signalling device. If variations in magnetic permeability exist in the test material, they maycause spurious signals with some types of eddy current tests. These signals are generally eliminated bysaturating the test piece with a uniform magnetic field at the test coil.Two general coil type
27、s will be discussed here. One coil type is the encircling or feed-through type where thecoil or coils are stationary while the material is fed through by means of a suitable transport mechanism.Either absolute or differential coil arrangements can be used. The differential coil arrangement is partic
28、ularlysensitive to short imperfections such as pits, silvers, or nicks. Longitudinal imperfections, such as cracks orseams, may be indicated if they are variable. The absolute arrangement is sensitive to variables such asmaterial properties, size, shape, and imperfections.The other type is the probe
29、 coil. This type can be made to rotate around the material, or the coil can be heldstationary while the material is rotated and traversed longitudinally in close proximity to the coil. The probecoil type is reliable and lends itself to mechanization of round product testing. The advantages are that
30、nomaterial saturation is necessary; that it is sensitive to continuous, uniform, longitudinal type imperfections;and that very shallow surface imperfections can be detected.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without
31、 license from IHS-,-,-SAE J349 Revised FEB91-4-4.4.2 FRINGE FLUXFringe (or leakage) flux testing is a nondestructive method for detecting cracks and otherdiscontinuities at or near the surface in ferromagnetic materials. The method consists of the following steps:a. The part is magnetized immediatel
32、y prior to or during the test to a proper level approaching saturation.b. A flux sensor containing magnetic transducers is placed on the surface in the magnetized area.c. The part or the magnetic flux sensor is moved progressively at a constant speed so the entire surfaceis scanned by the sensor.d.
33、Each magnetic transducer in the flux sensor is connected to an electronic console which amplifies,filters, and electronically processes the signals such that significant discontinuities are indicated(visually and audibly), then marked with paint or automatically removed from the production line, orb
34、oth.The fringe flux test is somewhat similar to a magnetic particle test with the flux sensor replacing the magneticparticles. It is somewhat similar to eddy current testing in the scanning and capability. The severity of thediscontinuity can be estimated and a rejection level set with respect to th
35、e magnitude of the electromagneticindication produced by the discontinuity.If properly applied, this method is capable of detecting the presence and location of significant discontinuitiessuch as pits, scabs, slivers, gouges, roll-ins, laps, seams, cracks, holes, and imperfections in welds.4.5 Ultra
36、sonicUltrasonic test methods, as described in SAE J428, can be used for the detection of surfacediscontinuities in bar and tube products. Various adaptations of the basic method are employed. The choice isinfluenced by factors such as cross-sectional area of the bar and the size and nature of the im
37、perfectionssought. Under proper conditions, ultrasonic waves can be propagated on and just below the surface of the bar.This test mode is particularly well suited to surface inspection. However, surface roughness and cleanlinessmust be controlled to prevent false determinations.In general, ultrasoni
38、c inspection is limited to bars and wires greater than 2.5 mm (0.1 in) in diameter.5. Methods of MeasurementElectromagnetic (eddy current or fringe flux) and ultrasonic testing may beconsidered quantitative in that acceptance standards can be established, and the equipment set to rejectmaterials hav
39、ing surface imperfections exceeding the predetermined acceptable conditions. Actual deviationsfrom an acceptance standard can be interpreted quantitatively, after acquiring experience with the materialbeing tested and gaining familiarity with the signal changes resulting from the type of imperfectio
40、n orimperfections being investigated.Only the surface length of an imperfection can usually be determined from liquid penetrant testing, magneticparticle testing, and visual examination and are usually interpreted qualitatively. However, some indication ofthe depth of surface discontinuities is some
41、times possible on hot rolled products if a fluorescent powder is usedwhen inspecting by the magnetic particle method (see Principles of Magnetic Particle Testing, p. 354).Methods of actual depth measurement that are easy to use will either destroy the initial evidence or are adestructive test method
42、. Those commonly used are as follows:5.1 File or Grind and InspectDepth is often determined by merely filing or grinding the imperfection until itdisappears visually. When using magnetic particle inspection, the material is ground or filed and thenmagnetic particle inspected again to determine if th
43、e imperfection is completely removed. The depth of theresulting groove to the point of complete removal of the discontinuity, can then be measured.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE
44、J349 Revised FEB91-5-5.2 MacroexaminationDepth can be determined by cutting and grinding a section perpendicular to the directionof the imperfection and macroetching the sample. The depth is measured by a suitable means which could bea scale, Brinell glass, or low power microscope.5.3 Microexaminati
45、onA very accurate method of measuring depth is by cutting and metallographically polishinga section perpendicular to the direction of the imperfection and measuring the depth microscopically.5.4 MacroetchingIf all conditions, including acid concentration, temperature, and time are controlled, a surf
46、acediscontinuity of a section can be exaggerated by macroetching. The depth of the etched imperfection can beestimated and a rough approximation made of the original imperfection depth since the amount of materialremoved can be determined by measuring the cross section before and after etching. Subt
47、racting thisdifference from the estimated depth of the etched surface imperfection gives the rough estimate.6. Notes6.1 Marginal IndiciaThe change bar (l) located in the left margin is for the convenience of the user in locatingareas where technical revisions have been made to the previous issue of
48、the report. An (R) symbol to the leftof the document title indicates a complete revision of the report.PREPARED BY THE SAE IRON & STEEL TECHNICAL COMMITTEECopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-
49、,-,-SAE J349 Revised FEB91RationaleNot applicable.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThis SAE Information Report provides a summary of several methods that are available fordetecting, and in some instances detecting and measuring, surface imperfections in rods, bars, tubes,and wires. References relating to detailed technical information and to specific applications areenumerated in 2.2.Re
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