Precious Metal B477-A (Solution annealed)
Temper · default condition
GB B477
Softest mill condition for deep drawing, coining, cladding and riveting of contact blanks before any age hardening.
Values for the A condition
Other B477 tempers and conditions
B477 is listed in 4 conditions; see the grade overview at B477.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefaultThis page Solution annealed | Softest mill condition for deep drawing, coining, cladding and riveting of contact blanks before any age hardening. | 250 | 470 | 30 | 130 HV | 9 % IACS |
Temper B | Intermediate temper when the part still needs bending or staking but higher contact-face hardness than annealed. | 500 | 650 | 14 | 190 HV | 9.3 % IACS |
Temper C | Hard strip/wire for contact springs and low-wear sliding contacts where only mild forming is required. | 700 | 800 | 6 | 240 HV | 9.5 % IACS |
Temper D | Maximum hardness condition (cold work plus nickel age-hardening heat treatment) for self-sprung contact fingers and wear-critical low-level switching. | 890 | 980 | 3 | 300 HV | 11 % IACS |
What is B477-A?
B477-A is B477 in the A temper — softest mill condition for deep drawing, coining, cladding and riveting of contact blanks before any age hardening. B477-A has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 470 MPa (68.2 ksi) — stronger than 81% of precious metal grades. Elongation at break is 30% and the elastic modulus is 100 GPa (14.5 Msi). B477-A has a density of 15 g/cm³ (0.542 lb/in³), heavier than 75% of precious metal grades. It melts at 960°C (1,760 °F).
Advantages
- Polishes to a fine finish — 95/100, better than 86% of precious metal grades
- Good corrosion resistance — 95/100, better than 82% of precious metal grades
- High strength — 250 MPa (36.3 ksi), better than 81% of precious metal grades
Limitations
- Poor heat conductor — 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 85% of precious metal grades
- Low electrical conductivity — 9 % IACS, worse than 84% of precious metal grades
- Heavy — 15 g/cm³ (0.542 lb/in³), worse than 75% of precious metal grades
B477-A properties
Typical room-temperature values for B477-A; 15 are specific to this condition. Other listed values are B477 reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
B477-A has a density of 15 g/cm³ (0.542 lb/in³), heavier than 75% of precious metal grades. It melts at 960°C (1,760 °F).
Mechanical10
B477-A has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 470 MPa (68.2 ksi) — stronger than 81% of precious metal grades. Elongation at break is 30% and the elastic modulus is 100 GPa (14.5 Msi).
Thermal6
B477-A is rated for continuous service to 400°C (752 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 85% of precious metal grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
B477-A conducts electricity at 9 % IACS, worse than 84% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (95/100), better than 82% of precious metal grades.
Sustainability4
Producing a kilogram of B477-A takes about 150,000 MJ of energy and emits 11,000 kg of CO₂ — more than 73% of precious metal grades. Typical recycled content is 60%.
Manufacturability8
B477-A's machinability is fair (40/100, worse than 60% of precious metal grades); weldability good (65/100); formability excellent (90/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with B477-A
Is B477 easy to machine?
Machine with sharp, high-rake carbide or diamond tooling, light cuts and oil mist; soft tempers are gummy and chips must be recovered for refining.
Can B477 be welded?
Joined to substrates by resistance, percussion or laser welding and by brazing; conventional arc welding is not used.
Can B477 be formed, bent or molded?
Temper A strip stamps, coins, draws and rivets easily; harden by cold work plus a low-temperature nickel ageing treatment after forming for Temper D properties.
What surface finishes work on B477?
Used bare with a bright buffed or burnished contact face; optional hard-gold or Rh flash plating; no anodizing, and avoid sulfur-bearing polishing compounds.
B477 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Augold, principal element | 68.5 – 69.5 | 69 |
| Ag | 24.5 – 25.5 | 25 |
| Nihardening addition | 5.5 – 6.5 | 6 |
| Other (total impurities)per ASTM B477 impurity limit | ≤ 0.15 | — |
B477-A — frequently asked
What is B477-A used for?
B477-A is typically used for low-level signal contacts, connector contacts and precision relays. In short: nickel-hardened gold contact alloy; tarnish-free signal surface; formable in Temper A.
What is the yield strength of B477-A?
B477-A has a typical yield strength of 250 MPa (36.3 ksi) and a tensile strength of 470 MPa (68.2 ksi) — stronger than 81% of precious metal grades. Strength varies by condition: see the 4 listed tempers.
Is B477-A easy to machine?
Not especially — machinability is rated fair (40/100, worse than 60% of precious metal grades). Machine with sharp, high-rake carbide or diamond tooling, light cuts and oil mist; soft tempers are gummy and chips must be recovered for refining.
Can B477-A be welded?
Yes — weldability is rated good (65/100). Joined to substrates by resistance, percussion or laser welding and by brazing; conventional arc welding is not used.
What surface finishes work on B477-A?
Used bare with a bright buffed or burnished contact face; optional hard-gold or Rh flash plating; no anodizing, and avoid sulfur-bearing polishing compounds.
Can B477-A be formed, bent or molded?
Temper A strip stamps, coins, draws and rivets easily; harden by cold work plus a low-temperature nickel ageing treatment after forming for Temper D properties.
What is the maximum service temperature of B477-A?
B477-A is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between B477-A and B477-D?
A is the default condition — softest mill condition for deep drawing, coining, cladding and riveting of contact blanks before any age hardening. D: maximum hardness condition (cold work plus nickel age-hardening heat treatment) for self-sprung contact fingers and wear-critical low-level switching. Yield strength is 250 MPa in A versus 890 MPa in D.
Sources
- ASTM B477 Standard Specification for Gold-Silver-Nickel Electrical Contact Material — ASTM International (2019)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Precious Metals, Electrical Contact Materials) — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials (Precious Metals) — ASM International (2005)
- Precious-metal electrical contact alloy strip and wire datasheets (Au-Ag-Ni family) — Deringer-Ney / Heraeus (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.