Precious Metal 24K-O (Annealed)
Temper · default condition
GB Au999 · ISO 9202
Default stocked condition for jewellery sheet/wire, coin blanks and forming stock; maximum ductility, minimum hardness.
Values for the O condition
Other 24K tempers and conditions
24K is listed in 5 conditions; see the grade overview at 24K.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Choose the as-cast state for poured investment bars, coin and ingot stock and traditional cast fine-gold jewellery before any working; strength is only 105 MPa tensile at 22 HB. | 25 | 105 | 30 | 22 HB | 71 % IACS |
ODefaultThis page Annealed | Default stocked condition for jewellery sheet/wire, coin blanks and forming stock; maximum ductility, minimum hardness. | 30 | 125 | 45 | 25 HB | 71 % IACS |
Quarter hard | Pick when soft gold is too limp to handle but deep forming is still required. | 70 | 145 | 30 | 34 HB | 70 % IACS |
Half hard | Compromise temper for bezels, findings and stampings needing some spring-back and dent resistance. | 120 | 170 | 15 | 43 HB | 69 % IACS |
Full hard | Maximum strength/hardness obtainable in pure gold — used for fine wire, contact springs and thin foil where handling strength matters. | 200 | 220 | 4 | 55 HB | 68 % IACS |
What is 24K-O?
24K-O is 24K in the O temper — default stocked condition for jewellery sheet/wire, coin blanks and forming stock; maximum ductility, minimum hardness. 24K-O has a yield strength of 30 MPa (4.35 ksi) and a tensile strength of 125 MPa (18.1 ksi) — weaker than 100% of precious metal grades. Elongation at break is 45% and the elastic modulus is 78 GPa (11.3 Msi). 24K-O has a density of 19.32 g/cm³ (0.698 lb/in³), heavier than 91% of precious metal grades. It melts at 1,064°C (1,947 °F).
Advantages
- Forms and bends easily — 100/100, better than 100% of precious metal grades
- Readily welded — 90/100, better than 99% of precious metal grades
- Good corrosion resistance — 100/100, better than 98% of precious metal grades
- Ductile — tolerates forming and impact — 45%, better than 97% of precious metal grades
- High service temperature — 600°C (1,112 °F), better than 85% of precious metal grades
Limitations
- Low strength — 30 MPa (4.35 ksi), worse than 100% of precious metal grades
- High embodied carbon — 20,000 kg CO₂/kg, worse than 97% of precious metal grades
- Heavy — 19.32 g/cm³ (0.698 lb/in³), worse than 91% of precious metal grades
- Low stiffness — 78 GPa (11.3 Msi), worse than 90% of precious metal grades
- Difficult to machine — 30/100, worse than 86% of precious metal grades
24K-O properties
Typical room-temperature values for 24K-O; 18 are specific to this condition. Other listed values are 24K reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
24K-O has a density of 19.32 g/cm³ (0.698 lb/in³), heavier than 91% of precious metal grades. It melts at 1,064°C (1,947 °F).
Mechanical12
24K-O has a yield strength of 30 MPa (4.35 ksi) and a tensile strength of 125 MPa (18.1 ksi) — weaker than 100% of precious metal grades. Elongation at break is 45% and the elastic modulus is 78 GPa (11.3 Msi).
Thermal6
24K-O is rated for continuous service to 600°C (1,112 °F). It conducts heat at 318 W/m·K (183.7 BTU/hr·ft·°F), better than 76% of precious metal grades. Thermal expansion is 14.2 µm/m·K (7.89 µin/in·°F).
Electrical3
24K-O conducts electricity at 71 % IACS, better than 76% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (100/100), better than 98% of precious metal grades.
Sustainability4
Producing a kilogram of 24K-O takes about 250,000 MJ of energy and emits 20,000 kg of CO₂ — more than 95% of precious metal grades. Typical recycled content is 28%.
Manufacturability8
24K-O's machinability is poor (30/100, worse than 86% of precious metal grades); weldability excellent (90/100); formability excellent (100/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 24K-O
Is 24K easy to machine?
Extremely gummy — use razor-sharp polished carbide or diamond tooling, high speed, light depth of cut and minimal or oil-based lubricant; collect all swarf for refining.
Can 24K be welded?
Laser or micro-TIG welds cleanly with no flux and no oxide problem; filler is normally the same 999 gold, and torch soldering with gold solders is routine.
Can 24K be formed, bent or molded?
The most malleable metal available: unlimited cold rolling, deep drawing, beating to sub-micron leaf and coining, with anneals at 500–700 °C whenever work hardening becomes inconvenient.
What surface finishes work on 24K?
Finished by burnishing, tumbling and rouge polishing to a mirror; no plating or anodising is needed or possible, but the surface scratches and dents very easily in service.
24K 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 |
|---|---|---|
| Agprincipal residual | ≤ 0.05 | 0.02 |
| Curesidual | ≤ 0.05 | 0.02 |
| Feresidual | ≤ 0.01 | 0 |
| Pbresidual; limited for hot-working ductility | ≤ 0.01 | 0 |
| Other impurities totalper GB/T 4134 / ISO 9202 | ≤ 0.1 | 0.05 |
| AuAu999 = 999 ‰ minimum fineness; investment grades are Au9999 (99.99 %) or Au99999 | ≥ 99.9 (balance) | — |
24K-O — frequently asked
What is 24K-O used for?
24K-O is typically used for gold bullion bars, coins, traditional Chinese jewelry and electrical contact plating. In short: most malleable metal available; highest-purity gold grade; no structural strength.
What is the yield strength of 24K-O?
24K-O has a typical yield strength of 30 MPa (4.35 ksi) and a tensile strength of 125 MPa (18.1 ksi) — weaker than 100% of precious metal grades. Strength varies by condition: see the 5 listed tempers.
Is 24K-O easy to machine?
Not especially — machinability is rated poor (30/100, worse than 86% of precious metal grades). Extremely gummy — use razor-sharp polished carbide or diamond tooling, high speed, light depth of cut and minimal or oil-based lubricant; collect all swarf for refining.
Can 24K-O be welded?
Yes — weldability is rated excellent (90/100). Laser or micro-TIG welds cleanly with no flux and no oxide problem; filler is normally the same 999 gold, and torch soldering with gold solders is routine.
What surface finishes work on 24K-O?
Finished by burnishing, tumbling and rouge polishing to a mirror; no plating or anodising is needed or possible, but the surface scratches and dents very easily in service.
Can 24K-O be formed, bent or molded?
The most malleable metal available: unlimited cold rolling, deep drawing, beating to sub-micron leaf and coining, with anneals at 500–700 °C whenever work hardening becomes inconvenient.
What is the maximum service temperature of 24K-O?
24K-O is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 24K-O and 24K-H04?
O is the default condition — default stocked condition for jewellery sheet/wire, coin blanks and forming stock; maximum ductility, minimum hardness. H04: maximum strength/hardness obtainable in pure gold — used for fine wire, contact springs and thin foil where handling strength matters. Yield strength is 30 MPa in O versus 200 MPa in H04.
Sources
- ISO 9202 Jewellery — Fineness of precious metal alloys — ISO (2019)
- GB/T 4134 (Gold ingots) — SAC (2015)
- ASM Handbook Vol. 2 — Properties of Precious Metals — ASM International (1990)
- CRC Handbook of Chemistry and Physics — Properties of the Elements — CRC Press (2022)
- World Gold Council technical & sustainability data (gold properties, emissions intensity) — WGC (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.