Precious Metal B780-SPR (Spring)
Supply condition
GB B780
Highest strength and elastic limit — for self-sprung contact fingers, blades and clips where forming is limited to gentle radii.
Values for the SPR condition
Other B780 tempers and conditions
B780 is listed in 6 conditions; see the grade overview at B780.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Pick for deep drawing, cold heading of contact rivets and any severe forming before final assembly. | 125 | 310 | 30 | 38 HRB | 78 % IACS |
1/8-Hard | Use when annealed strip is too soft to handle/blank cleanly but full forming ductility is still required. | 240 | 360 | 18 | 55 HRB | 77 % IACS |
Quarter hard | Balanced blanking/bending temper for stamped contact carriers and light spring blades. | 300 | 400 | 12 | 63 HRB | 76 % IACS |
Half hard | Most common temper for stamped moving contacts needing moderate stiffness with some bendability. | 400 | 470 | 6 | 74 HRB | 75 % IACS |
Full hard | Choose for maximum wear resistance and stiffness on flat contacts, sliding rings and shear-cut parts with minimal forming. | 500 | 550 | 3 | 84 HRB | 74 % IACS |
SPRThis page Spring | Highest strength and elastic limit — for self-sprung contact fingers, blades and clips where forming is limited to gentle radii. | 690 | 760 | 2 | 98 HRB | 56 % IACS |
What is B780-SPR?
B780-SPR is B780 supplied in the SPR condition — highest strength and elastic limit — for self-sprung contact fingers, blades and clips where forming is limited to gentle radii. B780-SPR has a yield strength of 690 MPa (100 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 100% of precious metal grades. Elongation at break is 2% and the elastic modulus is 95 GPa (13.8 Msi). B780-SPR has a density of 10.2 g/cm³ (0.368 lb/in³), lighter than 57% of precious metal grades. It melts at 779°C (1,434 °F). ANN is the default condition FabDigit quotes; SPR is available on request or by drawing note.
Advantages
- High strength — 690 MPa (100 ksi), better than 100% of precious metal grades
- Easy to machine — 55/100, better than 86% of precious metal grades
Limitations
- Limited service temperature — 150°C (302 °F), worse than 100% of precious metal grades
- Limited ductility — 2%, worse than 98% of precious metal grades
- Limited formability — 15/100, worse than 97% of precious metal grades
B780-SPR properties
Typical room-temperature values for B780-SPR; 29 are specific to this condition. Other listed values are B780 reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
B780-SPR has a density of 10.2 g/cm³ (0.368 lb/in³), lighter than 57% of precious metal grades. It melts at 779°C (1,434 °F).
Mechanical13
B780-SPR has a yield strength of 690 MPa (100 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 100% of precious metal grades. Elongation at break is 2% and the elastic modulus is 95 GPa (13.8 Msi).
Thermal6
B780-SPR is rated for continuous service to 150°C (302 °F). It conducts heat at 195 W/m·K (112.7 BTU/hr·ft·°F), better than 69% of precious metal grades. Thermal expansion is 18.7 µm/m·K (10.4 µin/in·°F).
Electrical3
B780-SPR conducts electricity at 56 % IACS, better than 72% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), worse than 66% of precious metal grades.
Sustainability4
Producing a kilogram of B780-SPR takes about 1,200 MJ of energy and emits 95 kg of CO₂ — less than 66% of precious metal grades. Typical recycled content is 60%.
Manufacturability8
B780-SPR's machinability is good (55/100, better than 86% of precious metal grades); weldability fair (40/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with B780-SPR
Is B780 easy to machine?
Machines like soft copper — very gummy; use sharp, high-rake carbide or HSS tools, high speed, light feed and flood lubricant, and collect all chips for refining.
Can B780 be welded?
Joined almost exclusively by resistance/projection welding, laser welding or brazing of contact buttons to carriers; fusion arc welding is not practiced.
Can B780 be formed, bent or molded?
Excellent cold formability in the annealed temper (deep drawing, cold heading, wire-to-rivet upsetting); interanneal near 600–650 °C in a low-sulfur atmosphere between heavy reductions.
What surface finishes work on B780?
Bright-dip or electropolish; apply anti-tarnish passivation or a thin gold/rhodium flash for low-level signal contacts, and avoid sulfur-containing packaging elastomers.
B780 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 |
|---|---|---|
| Agsilver content per ASTM B780 | 74.5 – 75.5 | 75 |
| Nigrain refiner / hardener | 0.4 – 0.6 | 0.5 |
| Other (total impurities)typical total residual limit | ≤ 0.15 | — |
| Cubalance copper | balance | — |
B780-SPR — frequently asked
What is B780-SPR used for?
B780-SPR is typically used for switchgear contacts, relay contact tips and connector wear surfaces. In short: harder than coin silver; high-conductivity silver contact; tarnishes in sulfur air.
What is the yield strength of B780-SPR?
B780-SPR has a typical yield strength of 690 MPa (100 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 100% of precious metal grades. Strength varies by condition: see the 6 listed tempers.
Is B780-SPR easy to machine?
Reasonably — machinability is rated good (55/100, better than 86% of precious metal grades). Machines like soft copper — very gummy; use sharp, high-rake carbide or HSS tools, high speed, light feed and flood lubricant, and collect all chips for refining.
Can B780-SPR be welded?
With care — weldability is rated fair (40/100). Joined almost exclusively by resistance/projection welding, laser welding or brazing of contact buttons to carriers; fusion arc welding is not practiced.
What surface finishes work on B780-SPR?
Bright-dip or electropolish; apply anti-tarnish passivation or a thin gold/rhodium flash for low-level signal contacts, and avoid sulfur-containing packaging elastomers.
Can B780-SPR be formed, bent or molded?
Excellent cold formability in the annealed temper (deep drawing, cold heading, wire-to-rivet upsetting); interanneal near 600–650 °C in a low-sulfur atmosphere between heavy reductions.
What is the maximum service temperature of B780-SPR?
B780-SPR is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between B780-ANN and B780-SPR?
ANN is the default condition — pick for deep drawing, cold heading of contact rivets and any severe forming before final assembly. SPR: highest strength and elastic limit — for self-sprung contact fingers, blades and clips where forming is limited to gentle radii. Yield strength is 125 MPa in ANN versus 690 MPa in SPR.
Sources
- ASTM B780 Standard Specification for 75 % Silver, 24.5 % Copper, 0.5 % Nickel Electrical Contact Alloy — ASTM International (2020)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (precious metals & electrical contact materials) — ASM International (1990)
- ASM Handbook Vol. 3 — Alloy Phase Diagrams (Ag-Cu system) — ASM International (1992)
- Electrical contact material datasheets (Ag-Cu and Ag-Cu-Ni strip/rivet stock) — Precious-metal contact fabricators (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.