ASTM A726-00
(Specification)Standard Specification for Cold-Rolled Magnetic Lamination Quality Steel, Semiprocessed Types
Standard Specification for Cold-Rolled Magnetic Lamination Quality Steel, Semiprocessed Types
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 where 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 purchaser can optimize magnetic properties for the various types.
1.3 A non-guaranteed core-loss type is usually made to controlled chemical composition. However, magnetic properties are not guaranteed by the producer.
1.4 Higher quality core-loss types are made to controlled chemical composition and are usually given 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 Specification A664.
1.5 The values stated in inch-pound, cgs, and em units are to be regarded as standard. Note 1-A complete metric companion to Specification A726 has been developed-A726M; therefore, no metric equivalents are presented in this specification.
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Designation: A 726 – 00
Standard Specification for
Cold-Rolled Magnetic Lamination Quality Steel,
Semiprocessed Types
This standard is issued under the fixed designation A 726; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope A 664 Practice for Identification of Standard Electrical- and
Lamination-Steel Grades in ASTM Specifications
1.1 This specification covers cold-rolled carbon sheet steel
A 700 Practices for Packaging, Marking, and Loading
used for magnetic applications. These products, commonly
Methods for Steel Products for Domestic Shipment
called “cold-rolled magnetic lamination steel” (CRML) are
E 18 Test Methods for Rockwell Hardness and Rockwell
usually intended for applications in which the stamped lami-
Superficial Hardness of Metallic Materials
nations or assembled core structures for electrical equipment
E 140 Hardness Conversion Tables for Metals
are annealed to develop the desired core loss and permeability
characteristics.
3. Terminology
1.2 By using appropriate lamination annealing practices, the
3.1 Definitions of Terms Specific to This Standard:
purchaser can optimize magnetic properties for the various
3.1.1 cold-rolled sheet—sheet manufactured from hot-
types.
rolled descaled coils by cold reducing to the desired thickness,
1.3 A nonguaranteed core-loss type is usually made to
generally followed by annealing to recrystallize the grain
controlled chemical composition. Magnetic properties are not
structure.Inthecaseofmagneticlaminationsteels,particularly
guaranteed by the producer.
semiprocessed lamination steels, temper rolling is used after
1.4 Higher quality core-loss types are made to controlled
annealingtoenhanceflatnessandoptimizemagneticproperties
chemical composition and are usually given critical reduction
during the purchaser’s lamination anneal.
on a temper mill to yield specified magnetic properties after a
3.1.2 magnetic lamination steels—specialty cold-rolled car-
suitable lamination anneal. These products, typically called
bon sheet steel melted to controlled levels of carbon with
semiprocessed lamination steel, are classified by the ASTM
additions of manganese, phosphorus, silicon, and aluminum.
Code Letter D in accordance with Practice A 664.
Residual elements are generally held as low as possible. The
1.5 The values stated in customary (cgs-emu and inch-
appropriate chemical composition combined with controlled
pound) units are to be regarded as standard. The values given
mill processing results in a carbon sheet steel having mechani-
in parentheses are mathematical conversions to SI units which
cal properties and magnetic properties (after a quality devel-
are provided for information only and are not considered
opment anneal) desired for electrical applications.
standard.
3.2 Other terms and symbols used in this specification are
2. Referenced Documents defined in Terminology A 340.
2.1 ASTM Standards:
4. Ordering Information
A 340 Terminology of Symbols and Definitions Relating to
2 4.1 Orders for material under this specification shall include
Magnetic Testing
the following information, as required, to describe the required
A 343 Test Method forAlternating-Current Magnetic Prop-
material adequately:
erties of Materials at Power Frequencies UsingWattmeter-
4.1.1 ASTM specification number and date of issue.
Ammeter-Voltmeter Method and 25-cm Epstein Test
2 4.1.2 Core-loss type number.
Frame
4.1.3 Finish (indicate typical profilometer range, as re-
A 370 Test Methods and Definitions for MechanicalTesting
3 quired) (see 10.2).
of Steel Products
4.1.4 Specify not oiled or oiled, as required (see 10.4).
4.1.5 Dimensions (nominal thickness and coil width) and
This specification is under the jurisdiction of ASTM Committee A-6 on tolerances, if not standard (see 9.1).
Magnetic Properties and is the direct responsibility of Subcommittee A06.02 on
Material Specifications.
Current edition approved May 10, 2000. Published July 2000. Originally
published as A 726 – 76. Last previous edition A 726/A 726M – 99.
2 4
Annual Book of ASTM Standards, Vol 03.04. Annual Book of ASTM Standards, Vol 01.05.
3 5
Annual Book of ASTM Standards, Vol 01.03. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A 726–00
4.1.6 Coil size (must include limitations on inside diameter 7. Magnetic Properties
and maximum weight).
7.1 The magnetic properties of these steels are optimized
4.1.7 Application (scroll slit for hermetic motors, and so
when the stamped laminations or assembled core structures are
forth).
annealed to reduce the carbon content to 0.005 % or less. To
4.1.8 Special requirements (indicate hardness range, mag- avoid sticking of laminations and assure adequate decarburiza-
netic limitations, and so forth).
tion, the annealing temperature should be in the range from
1350 to 1500°F (730 to 845°C). Time at temperature will vary
4.1.9 Cast or heat analysis and magnetic test report (request
with lamination dimensions, charge size, surface finish, and
if required).
annealing furnace characteristics. A partially combusted natu-
NOTE 1—A typical description is as follows: Cold-Rolled Sheet,
ral gas atmosphere with suitable dew point is often used.Also,
Magnetic Lamination Steel, ASTM A 726 64D480, Surface Roughness
some users of lamination steels use a hydrogen-nitrogen gas
50- to 80-µin. (1.3- to 2.0-µm) arithmetic average (R ), Not Oiled, 0.025
A
mixture with a suitable dew point. For steel containing man-
by 49 in. (0.64 by 1245 mm) by coil, 24-in. (610-mm) inside diameter,
ganese, silicon, and aluminum, annealing conditions shall be
20 000 lb (9000 kg) maximum, for fractional horsepower motors.
such that subsurface oxidation of these elements is minimized.
5. Materials and Manufacture
7.2 Core losses of higher quality core-loss types are guar-
anteed and shall conform to the limits given in Table 1.
5.1 Melting Practice—These steels are typically made by
Relativepeakpermeabilityisadimensionlessquantitywhichis
the basic-oxygen or electric-furnace process.
the same in all unit systems.The typical values of relative peak
5.2 Typical Rolling and Annealing—The processing se-
permeability for higher quality core-loss types are given in
quence for magnetic lamination steel comprises hot rolling,
Appendix X1.
pickling, cold rolling, annealing, and temper rolling.
5.2.1 Magneticlaminationsteels(alltypes)arecoldreduced
8. Mechanical Properties
to thickness. The nonguaranteed core-loss type product can
8.1 Hardness in the finished product depends on chemical
also be sold in the as-annealed condition or after a temper mill
composition and mill processing. For the mill process annealed
pass to flatten and to impart the required surface texture
and temper rolled condition, hardness values typically range
(surface roughness). Magnetic lamination steels are usually
from Rockwell 45 to 85 HRB.
temper rolled after box or continuous annealing to enhance
8.2 Specific ranges of hardness are subject to negotiation
magnetic property development during the purchaser’s lami-
and should be specified on the order.
nation anneal. In addition, the temper pass is used to improve
sheet flatness and punchability and to obtain the required 8.3 Rockwell hardness measurements are normally deter-
surface texture. Special emphasis may be placed on high
mined by a superficial test (R30T and R15T) and converted to
extensions (2 to 10 %) during the temper roll after annealing. a B scale value in accordance with Test Methods E 18 and
Tables E 140.
6. Chemical Composition
8.4 When mechanical tests are required, test specimens
shall be prepared and mechanical tests conducted in accor-
6.1 Magnetic lamination steels have low-carbon contents.
dance with Test Methods and Definitions A 370.
Forthenonguaranteedcore-losstype,thecarboncontentisless
than 0.06 %. For higher quality core-loss types, the carbon
9. Dimensions and Permissible Variations
contentistypicallylessthan0.04 %andmaybereducedtoless
than 0.02 % by means of vacuum degassing, argon stirring, or
9.1 Tolerances for thickness, width, and camber applicable
other steel refining practices when such low-carbon contents
to magnetic lamination steels are shown in Table 2, Table 3,
are required to facilitate decarburizing during annealing. Some
and Table 4.
magneticlaminationsteelsareproducedtocarboncontentsless
9.2 Thickness Variations—The average thickness of the
than 0.005 %. In these steels, decarburization during annealing
material supplied shall be as close as possible to the order
may not be required.
thickness. Measurements made with a contacting micrometer
6.2 Magnetic lamination steels may have manganese, phos-
at points no closer than ⁄8 in. (10 mm) from the edge of a sheet
phorus, silicon, and aluminum added to enhance punchability or coil of specified width shall not differ from the specified
and to improve magnetic characteristics by increasing electri-
thickness by more than the value (which includes taper) shown
cal resistivity. Other elements in small controlled amounts may in Table 2.
be used in the manufacture of these steels. In the past, the alloy
9.3 Taper—The rolling of flat rolled sheets inherently pro-
additions to magnetic lamination steels have been restricted
duces an edge which is thinner than the rest of the sheet. This
such that the density of the steel was maintained above 7.825
characteristic is termed tapered edge or feather or gamma and
3 3
g/cm (7825 kg/m ). However, higher quality core-loss type
occurs primarily within 1 or 2 in. (25 or 50 mm) from the
magnetic lamination steels may have alloy contents with
as-rolled edge of the material. The thickness variation classi-
3 3
density values less than 7.825 g/cm (7825 kg/m ) and
fied as edge taper is often the major portion of the total overal
...
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