ASTM B742-90(2012) - 1.5.2012
 
1. Scope

1.1 This specification covers fine silver grade 99.9 % in fabricated form. The forms covered are tubing, rod, wire, strip, and sheet for electrical contact applications.

1.2 The electrical contact properties may vary dependent upon the method of manufacture (refer to 6.3).

1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards, including those identified in the appropriate Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use.

TABLE 1 Chemical CompositionA

ElementWeight %

Silver

99.90 min (by difference)

Silver and copper

99.95 min

Copper

0.10 max

Nickel

0.002 max

Cadmium

0.005 max

Zinc

0.005 max

Lead

0.025 max

Iron

0.005 max

Aluminum

0.002 max

Bismuth

0.001 max

Total others

0.05 max

Total of all impurities

0.10 max

A Elements, such as phosphorus, sodium, and lithium are not natural impurities in this grade of silver and thus are not normally found in any appreciable quantities. However, since they may be detrimental for certain electrical contact applications, limits for these and other elements may be established by agreement between the purchaser and manufacturer. Refer to 7.2.

TABLE 2 Mechanical Properties of Sheet and Strip

Note—These hardness values are listed as “Typical,” because of the difficulty in establishing a range meaningful for all the thicknesses possible. If the purchaser desires hardness specifications, rather than tensile strengths, he shall reach agreement with the supplier as to the proper and suitable hardness scale and range for the particular size and form ordered.

TemperReduction
in B & S
Numbers
(Reference)
Percent
Reduction
(Reference)
Ultimate Tensile
Strength, psi (MPa)
Minimum
Elongation
in 2-in.
(51 mm), %
Typical
(see Note 1)
Hardness
Rockwell,
15 T
MinimumMaximum

Annealed

0

0

24 000 (165)

30 000 (207)

25

59 max

½ H

2

21

30 000 (207)

37 000 (255)

8

72

Hard

4

37

37 000 (255)

44 000 (303)

3

76

Spring

8

60

44 000 (303)

51 000 (352)

1

80

TABLE 3 Mechanical Properties of Wire and Rod

TemperReduction
in B & S
Numbers
(Reference)
Percent
Reduction
(Reference)
Ultimate Tensile
Strength, psi (MPa)
Minimum
Elongation
in 2 in.
(51 mm), %
MinimumMaximum

Annealed

0

0

24 000 (165)

30 000 (207)

25

1/8H

½

11

26 000 (179)

33 000 (228)

15

¼ H

1

21

30 000 (207)

37 000 (255)

4

½ H

2

37

39 000 (269)

46 000 (317)

4

Hard

4

60

42 000 (290)

49 000 (338)

2

Spring

8

84

46 000 (317)

54 000 (372)

1

 
2. Referenced Documents

B413-26

Standard Specification for Refined Silver

B476-21

Standard Specification for General Requirements for Wrought Precious Metal Electrical Contact Materials