1、AWS A4.2M:2006 (ISO 8249:2000 MOD)An American National StandardStandard Proceduresfor CalibratingMagnetic Instrumentsto Measure the DeltaFerrite Content ofAustenitic and DuplexFerritic-AusteniticStainless SteelWeld Metal550 N.W. LeJeune Road, Miami, FL 33126AWS A4.2M:2006 (ISO 8249:2000 MOD)An Ameri
2、can National StandardApproved by theAmerican National Standards InstituteJuly 10, 2006Standard Procedures for CalibratingMagnetic Instruments to Measure theDelta Ferrite Content of Austenitic and DuplexFerritic-Austenitic Stainless Steel Weld MetalSupersedes ANSI/AWS A4.2M/A4.2:1997Prepared by theAm
3、erican Welding Society (AWS) A5 Committee on Filler Metals and Allied MaterialsUnder the Direction of theAWS Technical Activities CommitteeApproved by theAWS Board of DirectorsAbstractCalibration procedures are specified for a number of commercial instruments that can then provide reproduciblemeasur
4、ements of the ferrite content of austenitic stainless steel weld metals. Certain of these instruments can be furthercalibrated for measurements of the ferrite content of duplex ferritic-austenitic stainless steel weld metals. Calibrationwith primary standards (nonmagnetic coating thickness standards
5、 from the U.S. National Institute of Standards andTechnology) is the preferred method for appropriate instruments. Alternatively, these and other instruments can be calibratedwith weld-metal-like secondary standards.Reproducibility of measurement after calibration is specified. Problems associated w
6、ith accurate determination of ferritecontent are described.Key Words Instrument calibration, delta ferrite, stainless steel weld metal, austenitic stainless weld metal, duplex stainless weld metaliiAWS A4.2M:2006 (ISO 8249:2000 MOD)International Standard Book Number: 0-87171-044-7American Welding So
7、ciety550 N.W. LeJeune Road, Miami, FL 33126 2006 by American Welding SocietyAll rights reservedPrinted in the United States of AmericaPhotocopy Rights. No portion of this standard may be reproduced, stored in a retrieval system, or transmitted in anyform, including mechanical, photocopying, recordin
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9、hat the appropriatefee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, tel: (978) 750-8400; Internet:.iiiAWS A4.2M:2006 (ISO 8249:2000 MOD)Statement on the Use of American Welding Society StandardsAll standards (codes, specifications, recommended practices, methods,
10、 classifications, and guides) of the AmericanWelding Society (AWS) are voluntary consensus standards that have been developed in accordance with the rules of theAmerican National Standards Institute (ANSI). When AWS American National Standards are either incorporated in, ormade part of, documents th
11、at are included in federal or state laws and regulations, or the regulations of other govern-mental bodies, their provisions carry the full legal authority of the statute. In such cases, any changes in those AWSstandards must be approved by the governmental body having statutory jurisdiction before
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13、ment between the contracting parties.AWS American National Standards are developed through a consensus standards development process that bringstogether volunteers representing varied viewpoints and interests to achieve consensus. While AWS administers the processand establishes rules to promote fai
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20、nly be obtained by sending a request,in writing, to the Managing Director, Technical Services Division, American Welding Society, 550 N.W. LeJeune Road,Miami, FL 33126 (see Annex E). With regard to technical inquiries made concerning AWS standards, oral opinionson AWS standards may be rendered. Howe
21、ver, such opinions represent only the personal opinions of the particularindividuals giving them. These individuals do not speak on behalf of AWS, nor do these oral opinions constitute officialor unofficial opinions or interpretations of AWS. In addition, oral opinions are informal and should not be
22、 used as asubstitute for an official interpretation.This standard is subject to revision at any time by the AWS A5 Committee on Filler Metals and Allied Materials. It mustbe reviewed every five years, and if not revised, it must be either reaffirmed or withdrawn. Comments (recommenda-tions, addition
23、s, or deletions) and any pertinent data that may be of use in improving this standard are requiredand should be addressed to AWS Headquarters. Such comments will receive careful consideration by the AWS A5Committee on Filler Metals and Allied Materials and the author of the comments will be informed
24、 of the Committeesresponse to the comments. Guests are invited to attend all meetings of the AWS A5 Committee on Filler Metals andAllied Materials to express their comments verbally. Procedures for appeal of an adverse decision concerning all suchcomments are provided in the Rules of Operation of th
25、e Technical Activities Committee. A copy of these Rules can beobtained from the American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.This page is intentionally blank.ivAWS A4.2M:2006 (ISO 8249:2000 MOD)vAWS A4.2M:2006 (ISO 8249:2000 MOD)PersonnelAWS A5 Committee on Filler Metals and Alli
26、ed MaterialsD. A. Fink, Chair The Lincoln Electric CompanyJ. S. Lee, 1st Vice Chair CB the preparation and measurement of standard pads for shielded metal arc covered electrodes. Thegeneral method is also recommended for the ferrite measurement of production welds and for weld metalfrom other proces
27、ses, such as gas tungsten arc welding, gas shielded metal arc welding and submergedarc welding (in these cases, the way of producing the pad should be defined); the calibration of other instruments to measure FN.The method described in this standard is intended for use on weld metals in the as-welde
28、d state and on weldmetals after thermal treatments causing complete or partial transformation of ferrite to any non-magneticphase. Austenitizing thermal treatments which alter the size and shape of the ferrite will change the magneticresponse of the ferrite.The method is not intended for measurement
29、 of the ferrite content of cast, forged or wrought austenitic orduplex ferritic-austenitic steel samples.2 Normative referenceThe following normative document contains provisions which, through reference in this text, constituteprovisions of this standard. For dated references, subsequent amendments
30、 to, or revisions of, this publicationdo not apply. However, parties to agreements based on this standard are encouraged to investigate thepossibility of applying the most recent edition of the normative document indicated below. For undatedreferences, the latest edition of the normative document re
31、ferred to applies. Members of ISO and IECmaintain registers of currently valid International Standards.ISO/TR 15510:1997, Stainless steels Chemical composition.3PrincipleThe measurement of the ferrite content of largely austenitic stainless steel weld metal through the attractiveforce between a weld
32、 metal sample and a permanent magnet is based upon the fact that the attractive forcebetween a two-phase (or multiphase) sample containing one ferromagnetic phase and one (or more) non-ferromagnetic phase(s) increases as the content of the ferromagnetic phase increases. In largely austeniticand dupl
33、ex ferritic-austenitic stainless steel weld metal, ferrite is magnetic, whereas austenite, carbides,sigma phase and inclusions are non-ferromagnetic.1) The term “austenitic-ferritic (duplex) stainless steel” is sometimes applied in place of “duplex ferritic-austenitic stainlesssteel”.AWS A4.2M:2006
34、(ISO 8249:2000 MOD)24 Calibration4.1 Coating thickness standardsThe coating thickness standards shall consist of non-magnetic copper applied to an unalloyed steel base ofsize 30 mm 30 mm. The thickness of the unalloyed steel base shall be equal to or greater than theexperimentally determined minimum
35、 thickness at which a further increase of the thickness does not cause anincrease of the attractive force between the standard permanent magnet and the coating thickness standard.The thickness of the non-magnetic copper coating shall be known to an accuracy of 5 % or better. Thechemical composition
36、of unalloyed steel shall be within the following limits:The copper coating may be covered by a chromium flash. The force required to tear off a given permanent magnetfrom the copper coating side of such a standard increases as the thickness of the copper coating decreases.NOTE To ensure adequate rep
37、roducibility of the calibration, the coating thickness standards defined above should beused. In particular, coating thickness standards produced by the US National Institute of Standards and Technology(NIST, formerly National Bureau of Standards or NBS) may be used.4.2 MagnetThe standard magnet sha
38、ll be a permanent magnet of cylindrical shape, 2 mm in diameter and about 50 mmin length. One end of the magnet shall be hemispherical, with a 1 mm radius and polished. As an example,such a magnet can be made of 36 % cobalt magnet steel, 48.45 mm 0.05 mm long, magnetically saturatedand then diluted
39、to 85 %. The magnetic strength of the magnet shall be such that the force needed to tear offthe standard magnet from the different coating thickness standards is within 10 % of the relationship shownin Figure 1 (the weight of the magnet excluded). This is equivalent to a relationship between tear-of
40、f force andFerrite Number of 5.0 FN/g 0.5 FN/g.4.3 InstrumentsThe measurement by this method shall be made by an instrument enabling an increasing tear-off force to beapplied to the magnet perpendicularly to the surface of the test specimen. The tear-off force shall beincreased until the permanent m
41、agnet is detached from the test specimen. The instrument shall accuratelymeasure the tear-off force which is required for detachment. The reading of the instrument may be directly inFN or in grams-force or in other units. If the reading of the instrument is in units other than FN, the relationshipbe
42、tween the FN and the instrument reading shall be defined by a calibration curve2).4.4 Calibration curveIn order to generate a calibration curve, determine the force needed to tear off the standard magnet defined in4.2 from several coating thickness standards defined in 4.1. Then convert the thicknes
43、s of non-magneticcoating of the coating thickness standards into FN according to Table 1, or according to the equivalentequation (1), as follows:FN = exp1.8059 1.11886 ln(t) 0.17740 ln(t)2 0.03502 ln(t)3 0.00367 ln(t)4(1)where t is the non-magnetic coating thickness, expressed in mm.Element Limit%CS
44、iMnPS0.08 to 0.130.10 max.0.30 to 0.600.040 max.0.050 max.2) Many instruments used to measure the thickness of a non-magnetic coating over a ferromagnetic base are suitable(e.g. MAGNE-GAGE of USA origin) and some commercially available instruments are designed directly for measurementof ferrite cont
45、ent (e.g. ALPHA-PHASE-METER of former USSR origin). In addition, after suitable in-house alterations,some laboratory balances can be used.AWS A4.2M:2006 (ISO 8249:2000 MOD)3Finally, plot the calibration curve as the relationship between the tear-off force in the units of the instrumentreading and th
46、e corresponding FN.To calibrate the instrument for measurement of ferrite content within the range from 0 to approximately 30 FN,which is appropriate for nominally austenitic stainless steel weld metals, a set consisting of a minimum ofeight standards with copper coating thicknesses between approxim
47、ately 0.17 mm and approximately 2 mm isrecommended3). To extend the calibration from approximately 30 FN to 100 FN, which is appropriate forduplex ferritic-austenitic stainless steel weld metals, a set consisting of a minimum of five standards withcoating thicknesses between 0.03 mm and 0.17 mm is r
48、ecommended.4.5 Calibration of other instruments with primary standardsIn principle, instruments with other than a standard magnet, and instruments using an approach to magneticproperty measurement other than magnetic attractive force, can be calibrated with primary standardsproviding that sufficient
49、 statistical data is collected. This has been done only with two older “legacy”instruments see Annex C.3) This calibration procedure may give misleading results if used on instruments measuring the ferrite content in ways otherthan through the attractive force or on instruments measuring ferrite through the attractive force but employing other than thestandard magnet defined in 4.2. Instruments which cannot be calibrated by the coating thickness standards and by theprocedure specified in 4.2 to 4.4 may be calibrated as described in clause 7.Figure 1 Relatio
