ASTM A726-05(2010)
(Specification)Standard Specification for Cold-Rolled Magnetic Lamination Quality Steel, Semiprocessed Types
Standard Specification for Cold-Rolled Magnetic Lamination Quality Steel, Semiprocessed Types
ABSTRACT
This specification covers the standard requirements for semi-processed cold-rolled magnetic lamination quality steels. These steels shall be made by the basic-oxygen or electric-furnace method and shall be processed by hot rolling, pickling, cold rolling, annealing, and temper rolling. Magnetic lamination steels shall have low-carbon contents and may have manganese, phosphorus, silicon, and aluminum additions to enhance punchability and to improve magnetic characteristics by increasing the electrical resistivity. There are no fixed chemical requirements for these steels only the requirement to meet the specified magnetic properties. These steels must be heat treated by the user to develop the specified magnetic properties. This specification covered steels with thicknesses of 0.0185 in. ( 0.47 mm), 0.022 in. (0.56 mm), 0.025 in. (0.64 mm), 0.028 in. (0.71 mm) and 0.031 in. (0.79 mm). For a given thickness there are three or more core loss types distinguished by maximum allowable core loss after a specified quality development anneal. Magnetic testing shall be done after the specified quality development anneal and shall use the Epstein test method. Magnetic testing shall be done at a test frequency of 60 Hz and a maximum flux density of 15 kG (1.5 T). Test methods to determine the magnetic and mechanical properties are listed. Other typical magnetic and physical properties are listed for reference.
SCOPE
1.1 This specification covers cold-rolled carbon sheet steel used for magnetic applications. These products, commonly called “cold-rolled magnetic lamination steel” (CRML) are usually intended for applications in which the stamped laminations or assembled core structures for electrical equipment are annealed to develop the desired core loss and permeability characteristics.
1.2 By using appropriate lamination annealing practices, the user can optimize magnetic properties for the various types.
1.3 Non-guaranteed core-loss types, usually made to controlled chemical compositions, are available but are not covered by this specification.
1.4 Higher quality core-loss types are made to controlled chemical compositions and are usually given a critical reduction on a temper-mill to yield specified magnetic properties after a suitable lamination anneal. These products, typically called semiprocessed lamination steel, are classified by the ASTM Code Letter D in accordance with Practice A664.
1.5 The values stated in customary (cgs-emu and inch-pound) units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units which are provided for information only and are not considered standard.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:A726 −05 (Reapproved 2010)
Standard Specification for
Cold-Rolled Magnetic Lamination Quality Steel,
Semiprocessed Types
This standard is issued under the fixed designation A726; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Wattmeter-Ammeter-Voltmeter Method and 25-cm Ep-
stein Test Frame
1.1 This specification covers cold-rolled carbon sheet steel
A370Test Methods and Definitions for Mechanical Testing
used for magnetic applications. These products, commonly
of Steel Products
called “cold-rolled magnetic lamination steel” (CRML) are
A664Practice for Identification of Standard Electrical Steel
usually intended for applications in which the stamped lami-
Grades in ASTM Specifications
nations or assembled core structures for electrical equipment
A700Guide for Packaging, Marking, and Loading Methods
are annealed to develop the desired core loss and permeability
for Steel Products for Shipment
characteristics.
E18Test Methods for Rockwell Hardness of Metallic Ma-
1.2 Byusingappropriatelaminationannealingpractices,the
terials
user can optimize magnetic properties for the various types.
E140Hardness Conversion Tables for Metals Relationship
Among Brinell Hardness, Vickers Hardness, Rockwell
1.3 Non-guaranteed core-loss types, usually made to con-
trolled chemical compositions, are available but are not cov- Hardness, Superficial Hardness, Knoop Hardness, Sclero-
scope Hardness, and Leeb Hardness
ered by this specification.
1.4 Higher quality core-loss types are made to controlled
3. Terminology
chemical compositions and are usually given a critical reduc-
tion on a temper-mill to yield specified magnetic properties 3.1 Definitions of Terms Specific to This Standard:
after a suitable lamination anneal. These products, typically
3.1.1 cold-rolled sheet—sheetmanufacturedfromhot-rolled
called semiprocessed lamination steel, are classified by the
descaled coils by cold reducing to the desired thickness,
ASTM Code Letter D in accordance with Practice A664. generally followed by annealing to recrystallize the grain
structure.Inthecaseofmagneticlaminationsteels,particularly
1.5 The values stated in customary (cgs-emu and inch-
semiprocessed lamination steels, temper rolling is used after
pound) units are to be regarded as standard. The values given
annealingtoenhanceflatnessandoptimizemagneticproperties
in parentheses are mathematical conversions to SI units which
during the user’s lamination anneal.
are provided for information only and are not considered
standard.
3.1.2 magnetic lamination steels—specialty cold-rolled car-
bon sheet steel melted to controlled levels of carbon with
2. Referenced Documents
additions of manganese, phosphorus, silicon, and aluminum.
Residual elements are generally held as low as possible. The
2.1 ASTM Standards:
appropriate chemical composition combined with controlled
A340Terminology of Symbols and Definitions Relating to
mill processing results in a carbon sheet steel having mechani-
Magnetic Testing
cal properties and magnetic properties (after a quality devel-
A343/A343MTest Method for Alternating-Current Mag-
opment anneal) desired for electrical applications.
netic Properties of Materials at Power Frequencies Using
3.2 Other terms and symbols used in this specification are
defined in Terminology A340.
This specification is under the jurisdiction of ASTM Committee A06 on
Magnetic Properties and is the direct responsibility of Subcommittee A06.02 on
4. Ordering Information
Material Specifications.
Current edition approved Nov. 1, 2010. Published December 2010. Originally
4.1 Ordersformaterialunderthisspecificationshallinclude
approved in 1976. Last previous edition approved in 2005 as A726–05. DOI:
10.1520/A0726-05R10. thefollowinginformation,asrequired,todescribetherequired
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
material adequately:
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.1.1 ASTM specification number and date of issue.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 4.1.2 Core-loss type number.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A726−05 (2010)
4.1.3 Finish (indicate typical profilometer range, as re- amounts may be used in the manufacture of these steels. In the
quired) (see 10.2). past, the alloy additions to magnetic lamination steels have
4.1.4 Specify not oiled or oiled, as required (see 10.4). beenrestrictedsuchthatthedensityofthesteelwasmaintained
3 3
4.1.5 Dimensions (nominal thickness and coil width) and above 7.825 g/cm (7825 kg/m ). However, higher quality
tolerances, if not standard (see 9.1). core-loss type magnetic lamination steels may have alloy
4.1.6 Coil size (must include limitations on inside diameter contents with density values less than 7.825 g/cm (7825
and maximum weight). kg/m ) and subsequent testing for magnetic properties shall be
4.1.7 Application (scroll slit for hermetic motors, and so in accordance with the procedure of Test Method A343/
forth). A343M (see Section 12).
4.1.8 Special requirements (indicate hardness range, mag-
6.3 Residual elements found in steels are generally held as
netic limitations, and so forth).
low as practical.
4.1.9 Cast or heat analysis and magnetic test report (request
if required).
7. Magnetic Properties
NOTE 1—A typical description is as follows: Cold-Rolled Sheet,
7.1 The magnetic properties of these steels are optimized
MagneticLaminationSteel,ASTMA72664D480,SurfaceRoughness50-
whenthestampedlaminationsorassembledcorestructuresare
to80-µin.(1.3-to2.0-µm)arithmeticaverage(R ),NotOiled,0.025by49
A
annealed to reduce the carbon content to 0.005% or less. To
in. (0.64 by 1245 mm) by coil, 24-in. (610-mm) inside diameter, 20000
avoid sticking of laminations and assure adequate
lb (9000 kg) maximum, for fractional horsepower motors.
decarburization, the annealing temperature should be in the
5. Materials and Manufacture
range from 1350 to 1500°F (730 to 845°C). Time at tempera-
ture will vary with lamination dimensions, charge size, surface
5.1 Melting Practice—These steels are typically made by
finish, and annealing furnace characteristics. A partially com-
the basic-oxygen or electric-furnace process.
busted natural gas atmosphere with suitable dew point is often
5.2 Typical Rolling and Annealing—The processing se-
used. Also, some users of lamination steels use a hydrogen-
quence for magnetic lamination steel comprises hot rolling,
nitrogen gas mixture with a suitable dew point. For steel
pickling, cold rolling, annealing, and temper rolling.
containing manganese, silicon, and aluminum, annealing con-
5.2.1 Magneticlaminationsteels(alltypes)arecoldreduced
ditions shall be such that subsurface oxidation of these ele-
to thickness. The non-guaranteed core-loss type product can
ments is minimized.
also be sold in the as-annealed condition or after a temper mill
7.2 Core losses of higher quality core-loss types are guar-
pass to flatten and to impart the required surface texture
anteed and shall conform to the limits given in Table 1.
(surface roughness). Magnetic lamination steels are usually
Relativepeakpermeabilityisadimensionlessquantitywhichis
temper rolled after box or continuous annealing to enhance
thesameinallunitsystems.Thetypicalvaluesofrelativepeak
magnetic property development during the user’s lamination
permeability for higher quality core-loss types are given in
anneal. In addition, the temper pass is used to improve sheet
Appendix X1.
flatness and punchability and to obtain the required surface
texture. Special emphasis may be placed on high extensions (2
8. Mechanical Properties
to 10%) during the temper roll after annealing.
5.2.2 When changes in the manufacture of the material are 8.1 Hardness in the finished product depends on chemical
compositionandmillprocessing.Forthemillprocessannealed
believed to exert possible significant effects upon the user’s
fabricating practices and upon the magnetic performance to be and temper rolled condition, hardness values typically range
from Rockwell 45 to 85 HRB.
obtained in the specified end use, the producer shall notify the
userbeforeshipmentismadesothatuserhasanopportunityto
8.2 Specific ranges of hardness are subject to negotiation
evaluate the effects.
and should be specified on the order.
8.3 Rockwell hardness measurements are normally deter-
6. Chemical Composition
mined by a superficial test (R30T and R15T) and converted to
6.1 Magnetic lamination steels have low-carbon contents.
a B scale value in accordance with Test Methods E18 and
For the non-guaranteed core-loss type, the carbon content is
Tables E140.
lessthan0.06%.Forhigherqualitycore-losstypes,thecarbon
8.4 When mechanical tests are required, test specimens
contentistypicallylessthan0.04%andmaybereducedtoless
shall be prepared and mechanical tests conducted in accor-
than 0.02% by means of vacuum degassing, argon stirring, or
dance with Test Methods and Definitions A370.
other steel refining practices when such low-carbon contents
are required to facilitate decarburizing during annealing. Some
9. Dimensions and Permissible Variations
magneticlaminationsteelsareproducedtocarboncontentsless
than0.005%.Inthesesteels,decarburizationduringannealing 9.1 Tolerances for thickness, width, and camber applicable
may not be required. to magnetic lamination steels are shown in Table 2, Table 3,
and Table 4.
6.2 Magnetic lamination steels may have manganese,
phosphorus, silicon, and aluminum added to enhance punch- 9.2 Thickness Variations—The average thickness of the
ability and to improve magnetic characteristics by increasing material supplied shall be as close as possible to the order
electrical resistivity. Other elements in small controlled thickness. Measurements made with a contacting micrometer
A726−05 (2010)
TABLE 1 Core-Loss Types and Maximum Core-Loss Values at 15 Kilogauss (1.5 T) and 60 Hz
NOTE1—Core-lossvaluesaredevelopedafterqualitydevelopmentanneal(QDA)atapproximately1450°F(790°C)toobtainthoroughlydecarburized
(<0.005% carbon) Epstein test
...
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