ASTM B298-99

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Designation: B 298 – 99
Standard Specification for
Silver-Coated Soft or Annealed Copper Wire
This standard is issued under the fixed designation B 298; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 2. Referenced Documents
1.1 This specification covers silver-coated, soft or annealed, 2.1 The following documents of the issue in effect at the
round copper wire, intended for use in electrical equipment, as time of reference form a part of this specification to the extent
follows: referenced herein:
1.1.1 Class A—Wire whose silver coating is at least 1.25 % 2.2 ASTM Standards:
of the total weight of the coated wire. B 4 Specifications for Tough-Pitch Lake Copper—Re-
1.1.2 Class B—Wire whose silver coating is at least 2.50 % finery Shapes
of the total weight of the coated wire. B 5 Specification for High Conductivity Tough-Pitch Cop-
1.1.3 Class C—Wire whose silver coating is at least 4.00 % per Refinery Shapes
of the total weight of the coated wire. B 193 Test Method for Resistivity of Electrical Conductor
1.1.4 Class D—Wire whose silver coating is at least 6.10 % Materials
of the total weight of the coated wire. B 258 Specification for Standard Nominal Diameters and
1.1.5 Class E—Wire whose silver coating is at least Cross-Sectional Areas of AWG Sizes of Solid Round Wires
10.00 % of the total weight of the coated wire. Used as Electrical Conductors
1.2 Silver-coated wire having different minimum percent- E 50 Practices for Apparatus, Reagents, and Safety Precau-
ages of silver by weight may be obtained by mutual agreement tions for Chemical Analysis of Metals
between the manufacturer and the purchaser. For information
3. Ordering Information
purposes the thickness of coating in microinches provided by
3.1 Orders for material under this specification shall include
the percentages listed above is shown in Table 1 (Explanatory
the following information:
Note 1).
1.3 The SI values of resistance and density are to be 3.1.1 Quantity of each size,
3.1.2 Wire size, diameter in inches (see 5.3 and Table 1),
regarded as standard. For all other properties values stated in
inch-pound units are to be regarded as the standard. The values 3.1.3 Class of coating (Section 1 and Table 1),
3.1.4 Type of copper, if special (see 4.2),
given in parentheses are provided for information purposes
only. 3.1.5 Place of inspection (see 9.1), and
3.1.6 Packaging and Package Marking (Section 10).
1.4 The following precautionary caveat pertains only to the
test method section of this specification: This standard does not 3.1.7 In addition supplementary requirements shall apply
only when specified by the purchaser in the inquiry, contract, or
purport to address all of the safety concerns, if any, associated
with its use. It is the responsibility of the user of this standard purchase order for direct procurement by agencies of the U.S.
Government (see S1, S2, and S3).
to establish appropriate safety and health practices and
determine the applicability of regulatory limitations prior to
use. For specific precautionary statements see 8.4.1.2 and
Explanatory Note 1.
This specification is under the jurisdiction of ASTM Committee B-1 on
Electrical Conductors and is the direct responsibility of Subcommittee B01.04 on Discontinued, see 1980 Annual Book of ASTM Standards, Part 6.
Conductors of Copper and Copper Alloys. Annual Book of ASTM Standards, Vol 02.01.
Current edition approved April 10, 1999. Published June 1999. Originally Annual Book of ASTM Standards, Vol 02.03.
published as B 298 – 55 T. Last previous edition B 298 – 94. Annual Book of ASTM Standards, Vol 03.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 298
TABLE 1 Tensile Requirements
Area at 20°C Thickness of Coating, μin. (For Information Only)
Elongation
Diameter,
in 10 in.,
Class A, 1.25 Class B, 2.50 Class C, 4.00 Class D, 6.10 Class E, 10.00
in.
cmils in.
min, %
% Silver % Silver % Silver % Silver % Silver
0.1285 16 510 0.01297 30 340 680 1 090 1 659 2 720
0.1144 13 090 0.01028 30 303 605 970 1 477 2 422
0.1019 10 380 0.008155 25 270 539 864 1 316 2 157
0.0917 8 230 0.00646 25 240 480 768 1 171 1 941
0.0808 6 530 0.00513 25 214 428 684 1 043 1 710
0.0720 5 180 0.00407 25 190 381 610 930 1 524
0.0641 4 110 0.00323 25 170 339 542 828 1 357
0.0571 3 260 0.00256 25 151 302 483 737 1 209
0.0508 2 580 0.00203 25 134 269 430 656 1 075
0.0453 2 050 0.00161 25 120 240 383 585 959
0.0403 1 620 0.00128 25 107 213 341 520 853
0.0359 1 290 0.00101 25 95 190 304 464 760
0.0320 1 020 0.000804 25 85 169 270 413 677
0.0285 812 0.000638 25 75 151 241 368 603
0.0253 640 0.000503 25 67 134 214 327 536
0.0226 511 0.000401 25 60 120 191 292 478
0.0201 404 0.00317 20 53 106 170 260 425
0.0179 320 0.000252 20 47 95 151 231 379
0.0159 253 0.000199 20 42 84 135 205 337
0.0142 202 0.000158 20 . 75 120 183 301
0.0126 159 0.000125 20 . 67 107 163 267
0.0113 128 0.000100 20 . 60 96 146 239
0.0100 100 0.0000785 20 . 53 85 129 212
0.0089 79.2 0.0000622 15 . 47 75 115 188
0.0080 64.0 0.0000503 15 . 42 68 103 169
0.0071 50.4 0.0000396 15 . . 60 92 150
0.0063 39.7 0.0000312 15 . . 53 81 133
0.0056 31.4 0.0000246 15 . . 47 72 119
0.0050 25.0 0.0000196 15 . . 42 65 106
0.0045 20.2 0.0000159 15 . . . 58 95
0.0040 16.0 0.0000126 15 . . . 52 85
0.0035 12.2 0.00000962 15 . . . 45 74
0.0031 9.61 0.00000755 15 . . . 40 66
0.0028 7.84 0.00000616 10 . . . . 59
0.0025 6.25 0.00000491 10 . . . . 53
0.0022 4.84 0.00000380 10 . . . . 47
0.0020 4.00 0.00000314 10 . . . . 42
4. Materials and Manufacture (Explanatory Note 2). The coated wire shall not vary from the
specified diameter by more than the following amounts:
4.1 The material shall be silver-coated copper wire (Ex-
Permissible Variations in
planatory Note 2), of such quality and purity that the finished
Nominal Diameter, in. Diameter, plus and minus
product shall have the properties and characteristics prescribed
Under 0.0100 0.0001 in.(0.1 mil)
in this specification. 0.0100 or over 1 %
NOTE 1—The following specifications define copper suitable for use:
5.4 Continuity of Coating—The coating shall be continu-
Specifications B 4 and B 5.
ous. The continuity of the coating shall be determined on
representative samples taken before stranding or insulating and
4.2 Copper of special qualities, forms, or types, as may be
shall be determined by the sodium polysulfide test, in accor-
agreed upon between the manufacturer and the purchaser, and
dance with 7.4. Wire whose coating weight corresponds to a
that will conform to the requirements prescribed in this
thickness less than 40μ in. (0.00004 in.) shall not be subject to
specification may also be used.
this test (Explanatory Note 3).
5. General Requirements
5.5 Weight of Coating—The weight of coating expressed in
percent of the total weight of the wire shall be not less than
5.1 Tensile Properties—The silver-coated wire shall con-
1.25 % for Class A; 2.50 % for Class B; 4.00 % for Class C;
form to the requirements for elongation prescribed in Table 1.
6.10 % for Class D; and 10.00 % for Class E. When coatings
No requirements for tensile strength are specified. For wire
other than these classes are required, the weight of the coating
whose nominal diameter is more than 0.001 in. (1 mil) greater
shall be not less than that specified. For ease of comparison, the
than a size listed in Table 1, but less than that of the next larger
thickness of coating for these classes has been included in
size, the requirements of the next larger size shall apply.
Table 1 (Explanatory Note 3).
5.2 Resistivity— The electrical resistivity of the coated wire
at a temperature of 20°C shall not exceed 875.20 V·lb mile . 5.6 Joints—Necessary joints in the wire and rods prior to
5.3 Dimensions and Permissible Variations—The wire sizes final plating and drawing shall be made in accordance with the
shall be expressed as the diameter of the wire in decimal best commercial practice. Joints made after plating shall not be
fractions of an inch to the nearest 0.1 mil (0.0001 in.) allowed to remain in the final product.
B 298
5.7 Finish—The coating shall consist of a smooth continu- tested, all of which shall conform to the weight criterion.
ous layer, firmly adherent to the surface of the copper. The wire However, any individual production unit, the specimen from
shall be bright and free from all imperfections not consistent which failed the weight criteria, shall be rejected.
with the best commercial practice. 6.6 Packaging—Conformance to the packaging require-
ments specified by the purchaser shall be determined in
6. Conformance Criteria (Explanatory Note 4)
accordance with Table 3. The number of units in the sample
showing nonconformance to the requirements shall not exceed
6.1 Any lot of wire, the samples of which comply with the
the allowable defect number, c, in Table 3. Failure to meet this
conformance criteria of this section, shall be considered as
requirement shall constitute failure to meet the packaging
complying with the requirements of Section 5. Individual
conformance criterion.
production units that fail to meet one or more of the require-
ments shall be rejected. Failure of a sample group from a lot to
7. Density
meet one or more of the following criteria shall constitute
cause for rejection of the lot. The conformance criteria for each 7.1 For the purpose of calculating weights, cross-sections,
etc., the density of the copper shall be taken as 8.89 g/cm
of the prescribed properties given in Section 5 are as follows:
6.1.1 Elongation—The lot shall be considered conforming (0.32117 lb/in. ) at 20°C (Explanatory Note 5). The density of
3 3
silver shall be taken as 10.5 g/cm (0.1 mil) (0.37933 lb/in. ).
if the elongation of each of the selected specimens is not less
than the elongation value in Table 1.
8. Test Methods
6.2 Resistivity— The electrical resistivity of each of the four
specimens shall conform to the requirements of 5.2. Failure to 8.1 Tensile Strength and Elongation:
meet these requirements shall constitute failure to meet the 8.1.1 No test for tensile strength shall be required.
resistivity conformance criterion. 8.1.2 The elongation of wire whose nominal diameter is
6.3 Dimensions—The dimensions of the first sample (Table larger than 0.0808 in. (2.052 mm) in diameter shall be
2) shall conform to the requirements of 5.3. If there are no determined as the permanent increase in length, expressed in
failures, the lot conforms to this requirement. If there are percent of the original length, due to the breaking of the wire
failures, but the number of these do not exceed the allowable in tension, measured between gage marks placed originally 10
defect number, c (Table 2), for the respective number of units in. (254 mm) apart upon the test specimen (Explanatory Note
in the sample, a second sample equal to n shall be taken and 6). The elongation of wire whose nominal diameter is 0.0808
the total defects of the n plus n units shall not exceed the in. and under may be determined as described above or by
allowable defect number, c . Failure to meet this requirement measurements made between the jaws of the testing machine.
shall constitute failure to meet the dimensional conformance When the latter method is used, the zero length shall be the
criterion. distance between the jaws at the start of the tension test and be
6.4 Continuity of Coating—The continuity of the coating of as near 10 in. as practicable, and the final length shall be the
each of the eight specimens shall conform to the requirements distance between the jaws at the time of rupture. The fracture
of 5.4. Failure of more than two specimens shall constitute shall be between gage marks, in the case of specimens so
failure to meet the continuity criterion. If not more than two marked, or between the jaws of the testing machine and not
specimens fail to meet the continuity criteria, eight additional closer than 1 in. (25.4 mm) to either gage mark or either jaw.
specimens from the lot shall be tested, all of which shall 8.2 Resistivity— The electrical resistivity of the material
conform to the continuity criteria. However, any individual shall be determined in accordance with Test Method B 193
production unit, the specimen from which failed to meet the (Explanatory Note 7). The purchaser may accept certification
continuity criteria, shall be rejected. that the wire was drawn from rod stock meeting the Interna-
6.5 Weight of Coating—The weight of coating of each of the tional Standard for Annealed Copper in lieu of resistivity tests
four specimens shall conform to the requirements of 5.5. on the finished wire.
Failure of more than one specimen shall constitute failure to 8.3 Dimensional Measurements—Dimensional measure-
meet the weight criteria. If only one specimen fails to meet the ments shall be made with a micrometer caliper equipped with
weight criteria, four additional specimens from the lot shall be a vernier graduated in 0.0001 in. Each coil shall be gaged at
TABLE 2 Sampling for Dimensional Measurements and Surface Finish
First Sample Second Sample
Allowable
Allowable
Number of
Number of Number of
Number of Units
Number of
Defects in
Units in Units in
in Lot
Defects in n + n
1 2
Both Sample
Sample, Sample,
First Sample,
c
n n
1 2
c
1 to 14, incl All 0 . . .
15 to 50, incl 14 0 . . .
51 to 100, incl 19 0 23 42 1
101 to 200, incl 24 0 46 70 2
201 to 400, incl 29 0 76 105 3
401 to 800, incl 33 0 112 145 4
Over 800 34 0 116 150 4
B 298
TABLE 3 Sampling for Packaging Inspection
8.4.3.2 Washing—After the immersion, thoroughly wash
Allowable the specimens in clean water and wipe dry with a clean, soft
Number of
Number of Units Number of
cloth.
Units in
in Lot Defective
Sample, n
8.4.3.3 Immersion in Hydrochloric Acid—After washing,
Units, c
immediately immerse the specimen 15 s in the HCl solution
1 to 30, incl all 0
31 to 50, incl 30 0 described in 8.4.2.2, thoroughly wash in clean water, and wipe
51 to 100, incl 37 0
dry with a clean, soft cloth.
101 to 200, incl 40 0
8.4.3.4 Examination of Specimens—After immersion and
201 to 300, incl 70 1
301 to 500, incl 100 2
washing examine the specimens to ascertain if copper exposed
501 t
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