Precious Metal B522 Class I Hard
Supply condition
ASTM B522 Class I
Hard = work Hardened
Choose for wiping/sliding contacts, spring fingers and slip-ring brushes where wear resistance and contact force retention matter.
Values for the Hard condition
Other B522 Class I tempers and conditions
B522 Class I is listed in 3 conditions; see the grade overview at B522 Class I.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault fully softened (ASTM B522 Class I) | Choose for maximum ductility when the contact must be drawn, coined, riveted or bonded to a carrier before service. | 180 | 390 | 30 | 100 HV | 10.5 % IACS |
Half hard | Compromise temper for strip and wire that still needs some bending but higher wear resistance than annealed. | 480 | 600 | 8 | 162 HB | 10 % IACS |
HardThis page Work Hardened | Choose for wiping/sliding contacts, spring fingers and slip-ring brushes where wear resistance and contact force retention matter. | 700 | 800 | 2.5 | 220 HV | 10 % IACS |
What is B522 Class I Hard?
B522 Class I Hard is B522 Class I supplied in the Hard condition — choose for wiping/sliding contacts, spring fingers and slip-ring brushes where wear resistance and contact force retention matter. B522 Class I Hard has a yield strength of 700 MPa (102 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 100% of precious metal grades. Elongation at break is 2.5% and the elastic modulus is 98 GPa (14.2 Msi). B522 Class I Hard has a density of 16 g/cm³ (0.578 lb/in³), heavier than 84% of precious metal grades. It melts at 1,005°C (1,841 °F). Annealed is the default condition FabDigit quotes; Hard is available on request or by drawing note.
Advantages
- High strength — 700 MPa (102 ksi), better than 100% of precious metal grades
- Good corrosion resistance — 98/100, better than 90% of precious metal grades
- Polishes to a fine finish — 95/100, better than 86% of precious metal grades
- Readily welded — 75/100, better than 78% of precious metal grades
Limitations
- Limited ductility — 2.5%, worse than 97% of precious metal grades
- Limited formability — 30/100, worse than 94% of precious metal grades
- Heavy — 16 g/cm³ (0.578 lb/in³), worse than 84% of precious metal grades
- Poor heat conductor — 43 W/m·K (24.8 BTU/hr·ft·°F), worse than 84% of precious metal grades
- High embodied carbon — 13,500 kg CO₂/kg, worse than 84% of precious metal grades
B522 Class I Hard properties
Typical room-temperature values for B522 Class I Hard; 15 are specific to this condition. Other listed values are B522 Class I reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
B522 Class I Hard has a density of 16 g/cm³ (0.578 lb/in³), heavier than 84% of precious metal grades. It melts at 1,005°C (1,841 °F).
Mechanical10
B522 Class I Hard has a yield strength of 700 MPa (102 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 100% of precious metal grades. Elongation at break is 2.5% and the elastic modulus is 98 GPa (14.2 Msi).
Thermal6
B522 Class I Hard is rated for continuous service to 250°C (482 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), worse than 84% of precious metal grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
B522 Class I Hard conducts electricity at 10 % IACS, worse than 79% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (98/100), better than 90% of precious metal grades.
Sustainability4
Producing a kilogram of B522 Class I Hard takes about 180,000 MJ of energy and emits 13,500 kg of CO₂ — more than 77% of precious metal grades. Typical recycled content is 80%.
Manufacturability7
B522 Class I Hard's machinability is fair (50/100, better than 74% of precious metal grades); weldability very good (75/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with B522 Class I Hard
Is B522 Class I easy to machine?
Soft and gummy — use sharp, polished-flute carbide or diamond tooling, light cuts, and capture every chip for refining.
Can B522 Class I be welded?
Contacts are attached by resistance, percussion or laser welding, or by brazing to Cu/Ni carriers; avoid open-arc processes.
Can B522 Class I be formed, bent or molded?
Excellent cold formability when annealed (drawn to <0.05 mm wire, coined into rivets); interanneal at ~700 °C after ~60 % reduction.
What surface finishes work on B522 Class I?
Takes a mirror polish and needs no protective plating; ultrasonic clean only, no anodizing (not applicable to noble metals).
B522 Class I 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 | 68.5 – 70 | 69 |
| Ptplatinum | 5.5 – 6.5 | 6 |
| Other (total)total impurities | ≤ 0.15 | — |
| Agsilver, balance | balance | — |
B522 Class I Hard — frequently asked
What is B522 Class I Hard used for?
B522 Class I Hard is typically used for slip rings, potentiometers and low-level signal contacts. In short: lowest, most stable contact resistance; drawable to fine wire; non-tarnishing noble alloy.
What is the yield strength of B522 Class I Hard?
B522 Class I Hard has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 100% of precious metal grades. Strength varies by condition: see the 3 listed tempers.
Is B522 Class I Hard easy to machine?
Reasonably — machinability is rated fair (50/100, better than 74% of precious metal grades). Soft and gummy — use sharp, polished-flute carbide or diamond tooling, light cuts, and capture every chip for refining.
Can B522 Class I Hard be welded?
Yes — weldability is rated very good (75/100). Contacts are attached by resistance, percussion or laser welding, or by brazing to Cu/Ni carriers; avoid open-arc processes.
What surface finishes work on B522 Class I Hard?
Takes a mirror polish and needs no protective plating; ultrasonic clean only, no anodizing (not applicable to noble metals).
Can B522 Class I Hard be formed, bent or molded?
Excellent cold formability when annealed (drawn to <0.05 mm wire, coined into rivets); interanneal at ~700 °C after ~60 % reduction.
What is the maximum service temperature of B522 Class I Hard?
B522 Class I Hard is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between B522 Class I Annealed and B522 Class I Hard?
Annealed is the default condition — choose for maximum ductility when the contact must be drawn, coined, riveted or bonded to a carrier before service. Hard: choose for wiping/sliding contacts, spring fingers and slip-ring brushes where wear resistance and contact force retention matter. Yield strength is 180 MPa in Annealed versus 700 MPa in Hard.
Sources
- ASTM B522/B522M Standard Specification for Gold-Silver-Platinum Electrical Contact Alloy — 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 (Noble Metals) — ASM International (2005)
- Precious-metal electrical contact alloy datasheets (Au-Ag-Pt series) — Deringer-Ney / Materion (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.