Precious Metal B522 Class II-H (Hardened)
Heat-treated state
ASTM B522 Class II
Choose for sliding/wiping contacts, brush wire and spring fingers where wear resistance and stable contact force matter more than formability.
Values for the H condition
Other B522 Class II tempers and conditions
B522 Class II is listed in 4 conditions; see the grade overview at B522 Class II.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Choose for stamping, deep drawing, wire drawing, clad-strip bonding and any part that is formed before final use. | 180 | 390 | 30 | 90 HB | 8 % IACS |
Half hard | Intermediate condition when a part must still be lightly bent but needs more contact-force stability than soft strip. | 420 | 560 | 10 | 155 HV | 7.8 % IACS |
HThis page Hardened | Choose for sliding/wiping contacts, brush wire and spring fingers where wear resistance and stable contact force matter more than formability. | 620 | 720 | 3 | 200 HB | 7.5 % IACS |
Spring temper | Maximum-strength drawn wire for instrument brushes, slip-ring wipers and low-force spring contacts. | 740 | 830 | 2 | 21 HRC | 7.4 % IACS |
What is B522 Class II-H?
B522 Class II-H is B522 Class II heat treated to H — choose for sliding/wiping contacts, brush wire and spring fingers where wear resistance and stable contact force matter more than formability. B522 Class II-H has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 98% of precious metal grades. Elongation at break is 3% and the elastic modulus is 92 GPa (13.3 Msi). B522 Class II-H has a density of 16 g/cm³ (0.578 lb/in³), heavier than 84% of precious metal grades. It melts at 1,035°C (1,895 °F). ANN is the default condition FabDigit quotes; H is available on request or by drawing note.
Advantages
- High strength — 620 MPa (89.9 ksi), better than 98% of precious metal grades
- Good corrosion resistance — 97/100, better than 88% of precious metal grades
- Easy to machine — 55/100, better than 86% of precious metal grades
Limitations
- Limited formability — 20/100, worse than 96% of precious metal grades
- Limited ductility — 3%, worse than 95% of precious metal grades
- Limited service temperature — 200°C (392 °F), worse than 89% of precious metal grades
- Low electrical conductivity — 7.5 % IACS, worse than 87% of precious metal grades
- Heavy — 16 g/cm³ (0.578 lb/in³), worse than 84% of precious metal grades
B522 Class II-H properties
Typical room-temperature values for B522 Class II-H; 16 are specific to this condition. Other listed values are B522 Class II reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
B522 Class II-H has a density of 16 g/cm³ (0.578 lb/in³), heavier than 84% of precious metal grades. It melts at 1,035°C (1,895 °F).
Mechanical12
B522 Class II-H has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 98% of precious metal grades. Elongation at break is 3% and the elastic modulus is 92 GPa (13.3 Msi).
Thermal6
B522 Class II-H is rated for continuous service to 200°C (392 °F). It conducts heat at 47 W/m·K (27.2 BTU/hr·ft·°F), worse than 80% of precious metal grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
B522 Class II-H conducts electricity at 7.5 % IACS, worse than 87% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (97/100), better than 88% of precious metal grades.
Sustainability4
Producing a kilogram of B522 Class II-H takes about 180,000 MJ of energy and emits 12,000 kg of CO₂ — more than 77% of precious metal grades. Typical recycled content is 85%.
Manufacturability7
B522 Class II-H's machinability is good (55/100, better than 86% of precious metal grades); weldability good (55/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with B522 Class II-H
Is B522 Class II easy to machine?
Gummy and smearing — use very sharp polished-flute carbide or diamond tooling, light depth of cut, high speed and generous coolant; capture all chips and swarf for refining.
Can B522 Class II be welded?
Joined by resistance, laser or micro-TIG welding and by brazing of contact rivets/clad strip; conventional arc welding is not used and any base-metal contamination degrades contact performance.
Can B522 Class II be formed, bent or molded?
Excellent cold formability in the annealed state — rolls, draws, coins and deep-draws readily; interanneal roughly every 50–70 % reduction at about 600–700 °C in a clean atmosphere.
What surface finishes work on B522 Class II?
Requires no protective plating — the natural non-tarnishing surface is the contact surface; burnish or lightly polish only, avoid abrasive media that can embed particles in the soft matrix.
B522 Class II 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 |
|---|---|---|
| AgClass II silver content; verify against current ASTM B522 revision | 24 – 26 | 25 |
| Ptplatinum addition for hardness and arc/wear resistance | 5.5 – 6.5 | 6 |
| Augold balance; total noble metal content essentially 100 %, base-metal impurities held to trace levels | balance | — |
B522 Class II-H — frequently asked
What is B522 Class II-H used for?
B522 Class II-H is typically used for slip rings, wiper contacts and precision switches. In short: harder wiping-contact variant; better wear than Class I; non-tarnishing sliding surface.
What is the yield strength of B522 Class II-H?
B522 Class II-H has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 720 MPa (104 ksi) — stronger than 98% of precious metal grades. Strength varies by condition: see the 4 listed tempers.
Is B522 Class II-H easy to machine?
Reasonably — machinability is rated good (55/100, better than 86% of precious metal grades). Gummy and smearing — use very sharp polished-flute carbide or diamond tooling, light depth of cut, high speed and generous coolant; capture all chips and swarf for refining.
Can B522 Class II-H be welded?
Yes — weldability is rated good (55/100). Joined by resistance, laser or micro-TIG welding and by brazing of contact rivets/clad strip; conventional arc welding is not used and any base-metal contamination degrades contact performance.
What surface finishes work on B522 Class II-H?
Requires no protective plating — the natural non-tarnishing surface is the contact surface; burnish or lightly polish only, avoid abrasive media that can embed particles in the soft matrix.
Can B522 Class II-H be formed, bent or molded?
Excellent cold formability in the annealed state — rolls, draws, coins and deep-draws readily; interanneal roughly every 50–70 % reduction at about 600–700 °C in a clean atmosphere.
What is the maximum service temperature of B522 Class II-H?
B522 Class II-H is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between B522 Class II-ANN and B522 Class II-SPR?
ANN is the default condition — choose for stamping, deep drawing, wire drawing, clad-strip bonding and any part that is formed before final use. SPR: maximum-strength drawn wire for instrument brushes, slip-ring wipers and low-force spring contacts. Yield strength is 180 MPa in ANN versus 740 MPa in SPR.
Sources
- ASTM B522 — Standard Specification for Gold-Silver-Platinum Electrical Contact Alloy — ASTM International (2020)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Precious Metals and Electrical Contact Materials) — ASM International (1990)
- ASM Handbook Vol. 3 — Alloy Phase Diagrams (Au-Ag-Pt system) — ASM International (1992)
- Precious-metal electrical contact alloy strip and wire datasheets — Specialty precious-metal refiners/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.