Precious Metal B522 Class I
ASTM B522 Class I
ASTM B522 Class I is a gold-silver-platinum precision contact alloy supplied annealed, in H02 and in hard tempers.
Reference datasheet — B522 Class I 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 Annealed condition
B522 Class I tempers and conditions
B522 Class I is supplied in 3 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
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 |
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?
ASTM B522 Class I is a gold-silver-platinum precision contact alloy supplied annealed, in H02 and in hard tempers. It is chosen for low and stable contact resistance in low-level, dry-circuit switching and is rolled to strip, drawn to fine wire below 0.05 mm and coined into rivets for slip rings and potentiometers. The alloy is soft in the annealed state (180 MPa yield, 390 MPa tensile, 30% elongation), conducts only 10.5% IACS, and is limited to about 400 °C service. Class II of the same specification gives a harder, more wear-resistant variant. B522 Class I 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). B522 Class I has a yield strength of 180 MPa (26.1 ksi) and a tensile strength of 390 MPa (56.6 ksi) — weaker than 59% of precious metal grades. Elongation at break is 30% and the elastic modulus is 95 GPa (13.8 Msi).
What is B522 Class I used for?
- slip rings
- potentiometers
- low-level signal contacts
Advantages
- 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
- Heavy — 16 g/cm³ (0.578 lb/in³), worse than 84% of precious metal grades
- High embodied carbon — 13,500 kg CO₂/kg, worse than 84% of precious metal grades
- Poor heat conductor — 45 W/m·K (26 BTU/hr·ft·°F), worse than 82% of precious metal grades
- Low electrical conductivity — 10.5 % IACS, worse than 77% of precious metal grades
B522 Class I properties
Typical room-temperature values for B522 Class I-Annealed; bars are the position among precious metal grades.
Physical3
B522 Class I 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 has a yield strength of 180 MPa (26.1 ksi) and a tensile strength of 390 MPa (56.6 ksi) — weaker than 59% of precious metal grades. Elongation at break is 30% and the elastic modulus is 95 GPa (13.8 Msi).
Thermal6
B522 Class I is rated for continuous service to 400°C (752 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), worse than 82% of precious metal grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
B522 Class I conducts electricity at 10.5 % IACS, worse than 77% 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 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's machinability is fair (35/100, worse than 73% of precious metal grades); weldability very good (75/100); formability excellent (90/100).
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. B522 Class I is highlighted; hover a dot for its name, or open the interactive family chart.
Working with B522 Class I
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.
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 | — |
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).
How much does B522 Class I cost?
B522 Class I 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.
B522 Class I — frequently asked
What is B522 Class I used for?
B522 Class I 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?
B522 Class I has a typical yield strength of 180 MPa (26.1 ksi) and a tensile strength of 390 MPa (56.6 ksi) — weaker than 59% of precious metal grades. Strength varies by condition: see the 3 listed tempers.
Is B522 Class I easy to machine?
Not especially — machinability is rated fair (35/100, worse than 73% 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 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?
Takes a mirror polish and needs no protective plating; ultrasonic clean only, no anodizing (not applicable to noble metals).
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 is the maximum service temperature of B522 Class I?
B522 Class I 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 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.
How much does B522 Class I cost?
B522 Class I 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 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; 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.