1、Designation: A726 18Standard Specification forCold-Rolled Magnetic Lamination Quality Steel,Semiprocessed Types1This standard is issued under the fixed designation A726; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 specification covers cold-rolled carbon sheet steelused for magnetic applications. These products, commonlycalled
3、“cold-rolled magnetic lamination steel” (CRML) areusually intended for applications in which the stamped lami-nations or assembled core structures for electrical equipmentare annealed to develop the desired core loss and permeabilitycharacteristics.1.2 This steel is produced to maximum specific core
4、-lossvalues and is intended primarily for commercial power fre-quency (50- and 60-Hz) applications in magnetic devices.Specific core-loss and permeability characteristics in confor-mance with this specification are developed through heattreatment by the user.1.3 Non-guaranteed core-loss types, usual
5、ly made to con-trolled chemical compositions, are available but are not cov-ered by this specification.1.4 Higher quality core-loss types are low carbon, silicon-iron, or silicon-aluminum-iron alloys containing up to about2.5 % silicon and less than 1 % aluminum. These steels areusually given a crit
6、ical reduction on a temper-mill to yieldspecified magnetic properties after a suitable lamination an-neal. These products, typically called semiprocessed magneticlamination steel, are classified by the ASTM Code Letter D inaccordance with Practice A664.1.5 The values stated in SI units are to be reg
7、arded asstandard. The values given in parentheses are mathematicalconversions to customary (cgs-emu and inch-pound) unitswhich are provided for information only and are not consideredstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It
8、 is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on
9、standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2A34/A34M Practice for Sampling and Procur
10、ement Testingof Magnetic MaterialsA340 Terminology of Symbols and Definitions Relating toMagnetic TestingA343/A343M Test Method for Alternating-Current Mag-netic Properties of Materials at Power Frequencies UsingWattmeter-Ammeter-Voltmeter Method and 25-cm Ep-stein Test FrameA370 Test Methods and De
11、finitions for Mechanical Testingof Steel ProductsA664 Practice for Identification of Standard Electrical SteelGrades in ASTM SpecificationsA700 Guide for Packaging, Marking, and Loading Methodsfor Steel Products for ShipmentA717/A717M Test Method for Surface Insulation Resistivityof Single-Strip Spe
12、cimensA937/A937M Test Method for Determining InterlaminarResistance of Insulating Coatings Using Two AdjacentTest SurfacesA976 Classification of Insulating Coatings for ElectricalSteels by Composition, Relative Insulating Ability andApplicationE18 Test Methods for Rockwell Hardness of Metallic Ma-te
13、rialsE140 Hardness Conversion Tables for Metals RelationshipAmong Brinell Hardness, Vickers Hardness, RockwellHardness, Superficial Hardness, Knoop Hardness, Sclero-scope Hardness, and Leeb Hardness1This specification is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and is the d
14、irect responsibility of Subcommittee A06.02 onMaterial Specifications.Current edition approved Oct. 1, 2018. Published October 2018. Originallyapproved in 1976. Last previous edition approved in 2010 as A726 05 (2010).DOI: 10.1520/A0726-18.2For referenced ASTM standards, visit the ASTM website, www.
15、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis int
16、ernational standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) C
17、ommittee.13. Terminology3.1 DefinitionsSee Terminology A340.3.2 Definitions of Terms Specific to This Standard:3.2.1 cold-rolled sheetsheet manufactured from hot-rolleddescaled coils by cold reducing to the desired thickness,generally followed by annealing to recrystallize the grainstructure. In the
18、 case of magnetic lamination steels, particularlysemiprocessed lamination steels, temper rolling is used afterannealing to enhance flatness and optimize magnetic propertiesduring the users lamination anneal.3.2.2 magnetic lamination steelsspecialty cold-rolled car-bon sheet steel melted to controlle
19、d levels of carbon withadditions of manganese, phosphorus, silicon, and aluminum.Residual elements are generally held as low as possible. Theappropriate chemical composition combined with controlledmill processing results in a carbon sheet steel having mechani-cal properties and magnetic properties
20、(after a quality devel-opment anneal) desired for electrical applications.4. Classification4.1 The cold-rolled magnetic lamination steel types de-scribed by this specification are shown in Table 1.5. Ordering Information5.1 Orders for material under this specification shall includethe following info
21、rmation, as required, to describe the requiredmaterial adequately:5.1.1 ASTM specification number and date of issue.5.1.2 Core-loss type number.5.1.3 Surface texture (indicate typical profilometer range, asrequired) (see 11.2).5.1.4 Specify not oiled or oiled, as required (see 11.4).5.1.5 Dimensions
22、 (nominal thickness and coil width) andtolerances, if not standard (see 10.1).5.1.6 Coil size (must include limitations on inside diameterand maximum weight).5.1.7 Application (the user shall disclose as much pertinentinformation as possible about the intended application toenable the producer to pr
23、ovide material characteristics mostsuitable for specific fabricating practices).5.1.8 Special requirements or exceptions to the provisionsof this specification.5.1.9 Cast or heat analysis and magnetic test report (requestif required).NOTE 1A typical description is as follows: Cold-Rolled Sheet,Magne
24、tic Lamination Steel, ASTM A726 64D480, Surface Roughness1.3- to 2.0-m (50- to 80-in.) arithmetic average (RA), Not Oiled, 0.64 by1245 mm (0.025 by 49 in.) by coil, 610-mm (24-in.) inside diameter, 9000kg (20 000 lb) maximum, for fractional horsepower motors.6. Materials and Manufacture6.1 Melting P
25、racticeThese steels are typically made bythe basic-oxygen or electric-furnace process.6.1.1 These steels are characterized by low carbon, usuallyless than 0.060 %. For higher quality core-loss types, theTABLE 1 Core-Loss Types and Maximum Specific Core-Loss Values at 1.5 T (15 Kilogauss) and 60 HzNO
26、TE 1 Specific core-loss values are developed after quality development anneal (QDA) per the recommended practices in 13.3 of this specificationEpstein test specimens (with one half cut parallel and the other half cut perpendicular to the direction of rolling).NOTE 2Maximum specific core-loss values
27、at 50 Hz are 0.79 maximum core-loss values at 60 Hz.SheetThickness,mm (in.)Core-LossTypeMaximumCore Loss,W/kgMaximumCore Loss,W/lb0.36 (0.0140) 36D145 3.20 1.4536D155 3.42 1.550.47 (0.0185) 47D165 3.64 1.6547D175 3.86 1.7547D190 4.19 1.9047D215 4.74 2.1547D270 5.95 2.7047D330 7.28 3.3047D380 8.38 3.
28、800.56 (0.022) 56D230 5.07 2.3056D260 5.73 2.6056D310 6.84 3.1056D380 8.38 3.8056D440 9.70 4.400.64 (0.025) 64D260 5.73 2.6064D290 6.40 2.9064D360 7.94 3.6064D430 9.48 4.3064D490 10.8 4.900.71 (0.028) 71D410 9.04 4.1071D480 10.6 4.8071D550 12.1 5.500.79 (0.031) 79D450 9.92 4.5079D540 11.9 5.4079D610
29、 13.5 6.10A726 182carbon content is typically less than 0.04 % and may bereduced to less than 0.02 % by means of vacuum degassing,argon stirring, or other steel refining practices when suchlow-carbon contents are required to facilitate decarburizingduring annealing. Some magnetic lamination steels a
30、re pro-duced to carbon contents less than 0.005 %. In these steels,decarburization during annealing may not be required. Theprinciple alloying element is commonly silicon, but aluminumup to about 0.8 % is sometimes used instead of, or in additionto silicon, depending on mill processing practice for
31、the desiredmagnetic grade. Individual producers will often have differentsilicon or aluminum contents for a particular grade as a resultof intrinsic mill processing procedures. Manganese or phos-phorus may also be added to enhance punchability and improvemagnetic characteristics.6.1.2 Residual eleme
32、nts found in steels are generally held aslow as practical.6.1.3 In the past, the alloy additions to magnetic laminationsteels have been restricted such that the density of the steel wasmaintained above 7825 kg/m3(7.825 g/cm3). However, higherquality core-loss type magnetic lamination steels may have
33、alloy contents with density values less than 7825 kg/m3(7.825g/cm3) and subsequent testing for magnetic properties shall bein accordance with the procedure of Test Method A343/A343M (see Section 12).6.1.4 The producer is not required to report chemicalcomposition of each lot except where a clear nee
34、d for suchinformation has been shown. In such cases, the analyses to bereported shall be negotiated between the producer and user.6.2 Typical Rolling and AnnealingThe processing se-quence for magnetic lamination steel comprises hot rolling,pickling, cold rolling, annealing, and temper rolling. Anadd
35、itional annealing operation may precede or follow thepickling operation.6.2.1 Magnetic lamination steels (all types) are cold reducedto thickness and are usually temper rolled after box orcontinuous annealing to enhance magnetic property develop-ment during the users lamination anneal. In addition,
36、thetemper pass is used to improve sheet flatness and punchabilityand to obtain the required surface texture. Special emphasismay be placed on high extensions (2 to 10 %) during thetemper roll after annealing.6.2.2 When changes in the manufacture of the material arebelieved to exert possible signific
37、ant effects upon the usersfabricating practices and upon the magnetic performance to beobtained in the specified end use, the producer shall notify theuser before shipment is made so that user has an opportunity toevaluate the effects.7. Magnetic Property Requirements7.1 The magnetic properties of t
38、hese steels are optimizedwhen the stamped laminations or assembled core structures areannealed to reduce the carbon content to 0.005 % or less. Toavoid sticking of laminations and assure adequatedecarburization, the annealing temperature should be in therange from 730 to 845C (1350 to 1500F). Time a
39、t tempera-ture will vary with lamination dimensions, charge size, surfacefinish, and annealing furnace characteristics. A partially com-busted natural gas atmosphere with suitable dew point is oftenused. Also, some users of lamination steels use a hydrogen-nitrogen gas mixture with a suitable dew po
40、int. For steelcontaining manganese, silicon, and aluminum, annealing con-ditions shall be such that subsurface oxidation of these ele-ments is minimized.7.2 Specific Core LossEach core loss type is identified bymaximum specific core-loss limits as shown in Table 1.7.3 PermeabilityThe permeability at
41、 all magnetic fluxdensity levels shall be as high as possible consistent with therequired maximum specific core-loss limits that govern thegrade. The typical values of relative peak permeability forhigher quality core-loss types are given in Appendix X1.8. Surface Insulation Characteristics8.1 Unles
42、s otherwise specified, cold-rolled magnetic lami-nation steels are supplied with no mill-applied coating. Auser-formed oxide (coating Type C-1 in Classification A976)can be created at the end of the heat treating cycle and providesadequate insulation for most applications.8.2 Applied Coatings:8.2.1
43、Several types of thin, tightly adherent applied coatingscan be applied to magnetic lamination steels. If a coating willbe applied, the surface finish (see 10.2) may be altered toensure proper insulating characteristics and coating adherence.Most suitable for magnetic lamination steels are coatingsde
44、signed to withstand the heat treatment performed afterstamping (coating Type C-5 in Classification A976).8.2.2 The use of coatings as specified in ClassificationA976, or other coatings, as well as the test method (TestMethods A717/A717M or A937/A937M), minimum value ofinsulating ability and other co
45、nditions for evaluating theeffectiveness of the coating, shall be determined by agreementbetween the user and producer. Usage of such coatings shouldbe approached with great caution since the coatings may havean inhibiting effect on decarburization and thereby limit theattainment of the lowest speci
46、fic core losses in the users heattreatment.9. Mechanical Properties9.1 Hardness in the finished product depends on chemicalcomposition and mill processing. For the mill process annealedand temper rolled condition, hardness values typically rangefrom Rockwell 45 to 85 HRB.9.2 Specific ranges of hardn
47、ess are subject to negotiationand should be specified on the order.9.3 Rockwell hardness measurements are normally deter-mined by a superficial test (R30T and R15T) and converted toa B scale value in accordance with Test Methods E18 andTables E140.9.4 When mechanical tests are required, test specime
48、nsshall be prepared and mechanical tests conducted in accor-dance with Test Methods and Definitions A370.A726 18310. Dimensions and Permissible Variations10.1 Tolerances for thickness, width, and camber applicableto magnetic lamination steels are shown in Table 2, Table 3,and Table 4.10.2 Thickness
49、VariationsThe average thickness of thematerial supplied shall be as close as possible to the orderthickness. Measurements made with a contacting micrometerat points no closer than 10 mm (0.375 in.) from the edge of asheet or coil of specified width shall not differ from thespecified thickness by more than the value (which includestaper) shown in Table 2.10.3 TaperThe rolling of flat rolled sheets inherentlyproduces an edge which is thinner than the rest of the sheet.This characteristic is termed tapered edge or feather or gammaand occurs primarily within 25 o
