1、BRITISH STANDARDBS ISO 24497-2:2007Non-destructive testing Metal magnetic memory Part 2: General requirementsICS 25.160.40g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g
2、44g42g43g55g3g47g36g58BS ISO 24497-2:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2007 BSI 2007ISBN 978 0 580 55670 8National forewordThis British Standard is the UK implementation of ISO 24497-2:2007.The UK participation i
3、n its preparation was entrusted to Technical Committee WEE/46, Non-destructive testing.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for
4、its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsReference numberISO 24497-2:2007(E)INTERNATIONAL STANDARD ISO24497-2First edition2007-11-01Non-destructive testing Metal magnetic memory P
5、art 2: General requirements Essais non destructifs Mmoire magntique des mtaux Partie 2: Exigences gnrales BS ISO 24497-2:2007ii iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Inter
6、national Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison wit
7、h ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technica
8、l committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to
9、 the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 24497-2 was prepared by the International Institute of Welding, Commission V, Quality control and quality assurance of
10、 welded products, recognized as an international standardizing body in the field of welding in accordance with Council Resolution 42/1999. Requests for official interpretations of any aspect of this part of ISO 24497 should be directed to the ISO Central Secretariat, who will forward them to the IIW
11、 Secretariat for an official response. ISO 24497 consists of the following parts, under the general title Non-destructive testing Metal magnetic memory: Part 1: Vocabulary Part 2: General requirements Part 3: Inspection of welded joints BS ISO 24497-2:2007blank1Non-destructive testing Metal magnetic
12、 memory Part 2: General requirements 1 Scope This part of ISO 24497 specifies the general requirements for the application of the method of metal magnetic memory of components, units, equipment, and structures for various application purposes. It covers non-destructive testing. The purposes of the m
13、ethod are the following. Determination of heterogeneity of the stress/strain state of equipment and structures and revealing of stress concentration zones as the main sources of damage. Determination of locations to perform metal sampling in stress concentration zones for assessment of the microstru
14、ctural-mechanical state. Early diagnostics of fatigue damage and evaluation of equipment and structure life. Reduction of testing and material costs with its utilization in combination with conventional methods of non-destructive testing. Quality control of welded joints of various types and embodim
15、ent (including contact and spot welding). Very quick sorting of new and used machine-building products by their microstructural heterogeneity. 2 Abbreviated terms The following abbreviations are used in this part of ISO 24497: IO: Inspection Object; SMLF: Self-Magnetic-Leakage Field; MMM: Metal Magn
16、etic Memory; NDT: Non-Destructive Testing; SCZ: Stress Concentration Zone. NOTE The Stress Concentration Zone (SCZ) is characterized by an abrupt local change of magnetization in the test object. Under examination SCZ is indicated as an abrupt local change of the SMLF. SCZ is formed in places of def
17、ect concentration, heterogeneity of metal microstructure; i.e., along welded joints or in zones of steady dislocation slip band caused by static or cyclic loads. BS ISO 24497-2:20072 3 General information 3.1 The MMM method refers to non-destructive magnetic-flux leakage testing by using magnetic-fi
18、eld-sensitive probes, but with no active magnetization of the IO. 3.2 The MMM method is based on measurement and analysis of the distribution of self-magnetic-leakage fields of metal components. Self-magnetic-leakage fields reflect the microstructural and technological history of metal components, i
19、ncluding welded joints. Natural magnetization formed in the Earths magnetic field during the process of the product fabrication is used during testing. For the equipment in operation, the magnetic memory appears in the irreversible change of the magnetization of the material in the direction of maxi
20、mal stresses due to working loads. 3.3 The MMM method determines SCZ, presence of imperfections, and heterogeneity of metal and welded joints microstructures. NOTE For components and machine-building products, SCZ in metal is conditioned by the technology of their fabrication (fusion, forging, rolli
21、ng, turning, press forming, thermal treatment, etc.). 3.4 For operating equipment in service, the MMM method gives the definition of SCZ specified by the complex action of technological factors, the units design philosophy, and operating loads. 3.5 The MMM method is used on products made of ferromag
22、netic and austenitic steels and alloys, and cast iron with unlimited test sizes and thicknesses, including welded joints. NOTE Austenitic steels can be inspected if their microstructure is sensitive for phase transformation under static or cyclic loads. 3.6 The temperature range of the MMM method ap
23、plication is according to the normal and safe working conditions of the operator (NDT inspector). Inspection tools shall be operable at temperatures from 20 C to +60 C. 4 Requirements of the inspection object 4.1 During the application of the MMM method, equipment and structures are inspected both i
24、n the in-service state (under load) and during maintenance (after removal of operating loads). 4.2 Surface dressing and preparation are not required. It is recommended to remove insulation. In individual cases, non-magnetic insulation is allowed during inspection. The maximum permissible insulation
25、layer thickness shall be determined experimentally. 4.3 The range of metal thicknesses in inspection zones is specified in techniques used for this inspection object. 4.4 The limiting factors for the application of the MMM method are the following: artificial magnetization of the metal; influence of
26、 foreign ferromagnetic products on the inspection object, near the inspection region of interest; presence of the source of an external magnetic field or an electric-welding current flow near (closer than 1 m) to the IO. 4.5 Acoustic noise from the IO and mechanical vibration of the IO do not influe
27、nce the inspection results. BS ISO 24497-2:200735 Requirements of the inspection means 5.1 For equipment inspection using the MMM method, specialized magnetometric instruments are used. The typical technique of the SCZ determination shall be documented in the manual of the instruments mentioned. 5.2
28、 The principle of the operation of these instruments is based on the registration of induced electrical voltage pulses in the sensor coil of a flux-gate meter at its placement into the self-magnetic-leakage field (SMLF) of the near-surface area of the IO. A flux-gate meter or other magnetic-sensitiv
29、e transformers (field meters or gradiometers) can be used as sensors for measuring the SMLF intensity. 5.3 Instruments shall have a screen for the graphical representation of the inspection parameters, a recorder based on a microprocessor, a storage unit, and scanner assemblies depending on the form
30、 of the individual specialized sensors. The possibility of an information swap from the instrument to an external computer and data printout shall be provided. Special software for computer processing of the inspection results should be supplied with the instrument. 5.4 Specialized sensors are suppl
31、ied with the instrument. The sensor type is determined by the method and the specific inspection tasks. The sensor shall have not less than two measurement channels, one of them for the instrument and another for tuning out the influences of the Earths external magnetic field. 5.5 The sensor housing
32、 shall be equipped with an electronic unit for the measured field amplification and a sensor for measuring the length of the scanned inspection path length. 5.6 On the IO, where it is difficult to use scanning devices, it is permitted to apply magnetometric instruments with a digital display of the
33、magnetic field intensity. 5.7 The following factors influence the error of SMLF measurements: IO surface finish; sensor lift-off from the IO surface; sensor scanning rate along the IO surface; sensor sensitivity; the permissible error of measurement shall be indicated in the techniques depending on
34、the individual inspection object. 5.8 The instruments should have the following metrological characteristics: the relative error of the measured magnetic field for each instrument channel not more than 5 %; the error of the measured length not more than 5 %; instrument measurement range not less tha
35、n 1 000 A/m; minimal scanning step (distance between the two adjacent inspection points) of 1 mm; electronic noise level conditioned by the processor and operation of the micro-electronics not more than 5 A/m. BS ISO 24497-2:20074 6 Pre-testing procedure 6.1 The pre-testing procedure is part of the
36、following basic stages: analysis of the technical documentation of the IO and preparation of the IO chart (logfile, inspection plan); selection of sensors and test instrument types; setting and calibration of the instruments and sensors according to the instruction indicated in the manual; segmentat
37、ion of the inspection object into individual inspection areas and inspection units having their own design philosophy and their indication in the IO logfile. 6.2 Analysis of technical documentation for the inspection object includes the following: indication of the steel grades and the dimensions of
38、 the selected inspection units; analysis of the IO operation modes and reasons of failures (damages); indication of the inspection units design philosophy, and locations of welded joints. 7 Inspection procedure 7.1 The normal and/or tangential component of the self-magnetic-leakage field, Hp, is mea
39、sured at the IO surface by continuous or spot scanning with the instrument sensor. At the same time, positions with extreme Hpfield changes are determined and registered at the IO surface. The zero value of the normal component corresponds to the maximal value of the tangential component of the fiel
40、d. 7.2 For quantitative assessment of the residual stress concentration level, the coefficient, Kin, indicating the intensity of the normal and/or tangential component of the magnetic field gradient, is determined by the formula: pinKHKl= , A/m2(1) where Hpis the difference of the Hpfields between t
41、he two adjacent scanning points; lKis the distance between these adjacent points. The zone of maximal concentration of residual stress corresponds to the maximum gradient of the normal and/or tangential component of the field. 7.3 The inspection results are recorded in the instruments memory unit an
42、d then, using the software, the SCZ with a maximum Kmax, invalue of the normal and/or tangential component of the field is determined. Then, using the software, an average value Kmed, inof the normal and/or tangential component of the field is determined for all SCZ revealed on the inspection object
43、. 7.4 After determination of Kmed, inand Kmax, invalues for all zones revealed during inspection, two or three SCZ with the highest Kmax, invalues are selected and the ratio m is calculated: max, inmed, inKmK= (2) At the same time, the value m is calculated separately for the ratio of gradients of t
44、he normal component of the field and separately for the ratio of gradients of the tangential component of the field. BS ISO 24497-2:20075If m, calculated for the ratio of gradients of the normal and/or tangential components of the field, exceeds a limiting threshold value, mlim, a conclusion is made
45、 about the material state in the next period of life preceding an IO damage. The magnetic index, mlim, characterizes the metal deformation capability by strengthening before failure and is determined in the laboratory and under industrial conditions using a special calibration method. 7.5 Additional
46、 testing by destructive and non-destructive methods is carried out in the SCZ with maximum Kin, maxvalues for normal and/or tangential components of the field, and the most representative material sample is selected for studying the material microstructure and its mechanical properties. 8 Recording
47、of inspection results 8.1 Inspection results are recorded in a report, and the following data shall be indicated: names of inspection units and segments where SCZ were detected; Hpfield values and the extreme values of the field gradient Kinin SCZ; results of additional inspection in SCZ by other ND
48、T methods; visual examination; IO non-failure operating time from its start-up; type of instrument used at inspection; rsum according to inspection results; date of inspection and name and surname of the inspector. 8.2 The IO logfile with indications of the inspection areas and detected SCZ shall be
49、 attached to the report. 8.3 The conclusion of the analysis of the results, characterizing the state of the IO, is made on the basis of inspection results. 8.4 Inspection results shall be stored till the next IO examination. 9 Safety requirements 9.1 Only persons trained in the MMM method and certified according to level I and II qualification levels are allowed to perform the inspection. 9.2 Persons performing the MMM inspection shall follow the safety requirement
