ASTM B298-12 Standard Specification for Silver-Coated Soft or Annealed Copper Wire

In the "ASTM B298-12 Standard Specification for Silver-Coated Soft or Annealed Copper Wire" standard developed by the American Society for Testing and Materials (ASTM), silver-coated, soft or annealed, round copper wire designed for use in electrical equipment is classified as follows:

Class A: Wire with a silver coating of at least 1,25 percent of the total weight of the coated wire
Class B: Wire with a silver coating of at least 2,50 percent of the total weight of the coated wire.
Class C: Wire with a silver coating of at least 4,00 percent of the total weight of the coated wire.
Class D: Wire with a silver coating of at least 6,10 percent of the total weight of the coated wire.
Class E: Wire with a silver coating of at least 10,00 percent of the total weight of the coated wire.

Silver-plated wire with different minimum silver percentages by weight may be obtained by mutual agreement between the manufacturer and the purchaser. For informational purposes, the thickness of the coating in microinches given the percentages stated above is shown in the table entitled “Tensile Requirements” given in the standard.

The materials shall be copper wire with silver plating so that the finished product has the properties and characteristics specified in this specification. The standard “ASTM B49 Standard Specification for Copper Rods for Electrical Purposes” indicates that the copper is suitable for use. Special grades, forms or types of copper may also be used, as agreed upon between the manufacturer and the purchaser and which conform to other requirements specified in this specification.

The general requirements in this standard are described as follows:

Tensile properties: Silver-plated wires shall comply with the elongation requirements specified in the table. No requirements are specified for tensile strength. For wire having a nominal diameter greater than 0.001 in. (XNUMX in.) than the size listed in the table, but smaller than the next larger size, the requirements of the next larger size apply.
Resistance: The electrical resistance of the coated wire at 20 degrees should not exceed 875,20 ohms lb/mil2.
Dimensions and allowable variations: Wire dimensions are expressed in decimal fractions of an inch of the wire diameter to the nearest 0.0001 inch. Coated wires shall not vary from the specified diameter by more than specified amounts.
Continuity of coating: The coating shall be continuous. Continuity of coating shall be determined by the sodium polysulfide test in accordance with this standard on representative samples taken before bending or insulation. Wire with a coating weight corresponding to a thickness of less than 0,00004 in. shall not be subjected to this test.
Coating weight: The coating weight, expressed as a percentage of the total weight of the wires, shall not be less than 1,25 percent for Class A, 2,50 percent for Class B, 4,00 percent for Class C, 6,10 percent for Class D and 10,00 percent for Class E. Where coatings outside these classes are required, the weight of the coating shall not be less than that specified. For ease of comparison, the coating thickness for these classes is included in the table.
Connections: Necessary connections should be made in the wire and prior to final coating and drawings in accordance with best commercial practice. Connections made after coating should not be allowed to remain in the final product.
Finish: The coating shall consist of a smooth, continuous layer which adheres tightly to the surface of the copper. The wires shall be bright and free from all defects not consistent with best commercial practice.

Any batch of wire whose samples meet the conformity criteria of this section is deemed to comply with the requirements of this standard. Individual production units that do not meet one or more of the requirements are rejected. Failure of a group of samples from a batch to meet one or more of the following criteria will result in the rejection of the batch. The conformity criteria for each of the specifications specified in this standard are as follows:

Elongation: If the elongation of each of the selected samples is not less than the elongation value in the table, the batches are considered compatible.
Resistivity: The electrical resistance of each of the four samples shall comply with the other requirements of this standard. Failure to meet these requirements shall constitute failure to meet the resistance compliance criterion.
Dimensions: The dimensions of the sample shall comply with the other requirements of this standard. If there are no defects, the batch shall comply with this requirement. If there are defects but their number does not exceed the number of defects allowed, a second sample shall be taken for the corresponding number of units in the sample and the total defects shall not exceed the number of defects allowed. Failure to meet these requirements shall constitute failure to meet the dimensional conformity criterion.
Continuity of coating: The continuity of the coating on each of the eight samples shall comply with the other requirements of this standard. Failure of more than two samples constitutes failure to meet the continuity criterion. If more than two samples fail to meet the continuity criteria, eight additional samples from the lot shall be tested and all shall meet the continuity criteria. However, any individual production unit whose sample does not meet the continuity criteria shall be rejected.
Coating Weight: The coating weight of each of the four samples shall comply with the other requirements of this standard. Failure of more than one sample shall mean that the weight criteria are not met. If only one sample fails the weight criteria, four additional samples from the batch shall be tested and all shall meet the weight criteria. However, any individual production unit whose sample fails to meet the weight criteria shall be rejected.
Packaging: Compliance with the packaging requirements specified by the purchaser is determined according to the table. The number of units in the samples showing non-compliance with other requirements must not exceed the number of defects allowed in the table. Failure to meet these requirements means that the packaging compliance criterion is not met.

Test methods described in this standard include:

Tensile strength and elongation
Resistance
Dimensional measurements
Continuity of coating
Weight of coating

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