Precious Metal B540
GB B540
ASTM B540 covers high-purity palladium and palladium-alloy contact material, supplied soft-annealed, stress-relieved, dead-hard and age-hardened.
Reference datasheet — B540 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SA condition
B540 tempers and conditions
B540 is supplied in 4 conditions, soft to hard. SA is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SADefault Solution annealed | Standard stocked soft temper for stamping, drawing and cladding of contact strip and wire; maximum ductility and lowest contact resistance. | 55 | 195 | 35 | 44 HB | 16 % IACS |
Stress relieved | Pick when formed contact springs and rivets need dimensional stability and reduced springback distortion without losing all cold-work strength. | 170 | 260 | 22 | 68 HB | 15.5 % IACS |
Ductile hardened | Choose for sliding contacts, brushes and formed springs needing higher hardness and wear life while still permitting bending and riveting. | 280 | 330 | 10 | 100 HB | 14.8 % IACS |
Age (order) hardened Pd-Cu / Pd-Ag-Cu alloy grade | Use for high-wear, low-force sliding contacts, slip rings and probe tips where maximum hardness and erosion resistance are needed; applies to the ordering Pd-Cu/Pd-Ag-Cu alloy grades, not to pure palladium. | 550 | 750 | 8 | 22 HRC | 6 % IACS |
What is B540?
ASTM B540 covers high-purity palladium and palladium-alloy contact material, supplied soft-annealed, stress-relieved, dead-hard and age-hardened. It is used for tarnish resistance and stable low-current behaviour in dry-circuit switching, typically as strip, wire, stamped contacts and material clad to Ag or Cu carriers. The soft-annealed condition is very ductile but weak (55 MPa yield, 195 MPa tensile, 35% elongation, 44 HB), conductivity is 16% IACS with 71.8 W/m·K thermal conductivity, and service is limited to about 400 °C. Palladium can absorb hydrogen and can form organic surface films in dry circuits; the Pd-Ag-Cu alloy of ASTM B563 is the harder alternative. B540 has a density of 12.02 g/cm³ (0.434 lb/in³), heavier than 67% of precious metal grades. It melts at 1,554°C (2,829 °F). B540 has a yield strength of 55 MPa (7.98 ksi) and a tensile strength of 195 MPa (28.3 ksi) — weaker than 95% of precious metal grades. Elongation at break is 35% and the elastic modulus is 121 GPa (17.5 Msi).
What is B540 used for?
- telecom relays
- low-power switches
- dry-circuit contacts
Advantages
- Forms and bends easily — 95/100, better than 91% of precious metal grades
- Readily welded — 80/100, better than 87% of precious metal grades
- Ductile — tolerates forming and impact — 35%, better than 83% of precious metal grades
- Good corrosion resistance — 95/100, better than 82% of precious metal grades
- Stiff — 121 GPa (17.5 Msi), better than 80% of precious metal grades
Limitations
- Low strength — 55 MPa (7.98 ksi), worse than 95% of precious metal grades
- Difficult to machine — 30/100, worse than 86% of precious metal grades
B540 properties
Typical room-temperature values for B540-SA; bars are the position among precious metal grades.
Physical3
B540 has a density of 12.02 g/cm³ (0.434 lb/in³), heavier than 67% of precious metal grades. It melts at 1,554°C (2,829 °F).
Mechanical12
B540 has a yield strength of 55 MPa (7.98 ksi) and a tensile strength of 195 MPa (28.3 ksi) — weaker than 95% of precious metal grades. Elongation at break is 35% and the elastic modulus is 121 GPa (17.5 Msi).
Thermal6
B540 is rated for continuous service to 400°C (752 °F). It conducts heat at 71.8 W/m·K (41.5 BTU/hr·ft·°F), worse than 60% of precious metal grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
B540 conducts electricity at 16 % IACS, worse than 60% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (95/100), better than 82% of precious metal grades.
Sustainability4
Producing a kilogram of B540 takes about 55,000 MJ of energy and emits 3,900 kg of CO₂ — more than 62% of precious metal grades. Typical recycled content is 60%.
Manufacturability8
B540's machinability is poor (30/100, worse than 86% of precious metal grades); weldability very good (80/100); formability excellent (95/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the precious metal family
Yield strength against density for every precious metal grade FabDigit runs. B540 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with B540
Is B540 easy to machine?
Soft and gummy — use sharp positive-rake carbide/diamond tools, high speed, light feed and copious lubrication; collect all chips for refining.
Can B540 be welded?
Resistance, laser and micro-TIG welding of contacts to Cu/CuNi carriers is routine; avoid hydrogen-rich flames to prevent H absorption and embrittlement.
Can B540 be formed, bent or molded?
Excellent cold formability in the annealed temper (stamping, deep drawing, cladding to Ag/Cu strip); interanneal at 700–900 °C in clean inert or slightly oxidizing atmosphere.
B540 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.
| Element | Spec limit (wt %) |
|---|---|
| Ptimpurity limit, pure grade | ≤ 0.02 |
| Rhimpurity limit | ≤ 0.02 |
| Ir+Ruimpurity limit | ≤ 0.02 |
| Feimpurity limit | ≤ 0.01 |
| Cuimpurity limit, pure grade | ≤ 0.01 |
| Pbimpurity limit | ≤ 0 |
| Other elements, totalsum of impurities | ≤ 0.05 |
| PdPure palladium contact grade of ASTM B540; alloy grades of the same specification substitute Ag (up to ~40 %), Cu (up to ~40 %) or Ru (up to ~10 %) for part of the Pd | ≥ 99.95 (balance) |
What surface finishes work on B540?
No anodizing; finish by polishing, electropolishing or thin Au/Rh flash plating to suppress organic 'brown powder' formation in dry-circuit switching.
How much does B540 cost?
B540 is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
B540 — frequently asked
What is B540 used for?
B540 is typically used for telecom relays, low-power switches and dry-circuit contacts. In short: tarnish-resistant palladium contact; softest, most formable grade here; dry-circuit relay standard.
What is the yield strength of B540?
B540 has a typical yield strength of 55 MPa (7.98 ksi) and a tensile strength of 195 MPa (28.3 ksi) — weaker than 95% of precious metal grades. Strength varies by condition: see the 4 listed tempers.
Is B540 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 86% of precious metal grades). Soft and gummy — use sharp positive-rake carbide/diamond tools, high speed, light feed and copious lubrication; collect all chips for refining.
Can B540 be welded?
Yes — weldability is rated very good (80/100). Resistance, laser and micro-TIG welding of contacts to Cu/CuNi carriers is routine; avoid hydrogen-rich flames to prevent H absorption and embrittlement.
What surface finishes work on B540?
No anodizing; finish by polishing, electropolishing or thin Au/Rh flash plating to suppress organic 'brown powder' formation in dry-circuit switching.
Can B540 be formed, bent or molded?
Excellent cold formability in the annealed temper (stamping, deep drawing, cladding to Ag/Cu strip); interanneal at 700–900 °C in clean inert or slightly oxidizing atmosphere.
What is the maximum service temperature of B540?
B540 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 B540-SA and B540-AH?
SA is the default condition — standard stocked soft temper for stamping, drawing and cladding of contact strip and wire; maximum ductility and lowest contact resistance. AH: use for high-wear, low-force sliding contacts, slip rings and probe tips where maximum hardness and erosion resistance are needed; applies to the ordering Pd-Cu/Pd-Ag-Cu alloy grades, not to pure palladium. Yield strength is 55 MPa in SA versus 550 MPa in AH.
How much does B540 cost?
B540 is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B540 — Standard Specification for Palladium Electrical Contact Material — ASTM International (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Precious Metals & Electrical Contact Materials) — ASM International (1990)
- Precious Metal Contact Materials — Palladium and Palladium Alloys — Johnson Matthey (2020)
- CRC Handbook of Chemistry and Physics — Physical Properties of the Elements (Pd) — CRC Press (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.