Precious Metal 24K
GB Au999 · ISO 9202
24K (Au999) is essentially pure gold, unalloyed and therefore the softest and most malleable material in the precious-metal group: 30 MPa yield, 125 MPa tensile, 45 % elongation and about 25 HB.
Reference datasheet — 24K 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 O condition
24K tempers and conditions
24K is supplied in 5 conditions, soft to hard. O is the default FabDigit quotes; the values on this page are for it.
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 |
ODefault 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 |
Supply forms, finishes and certifications
Ways 24K is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
BW | Bonding wire | Surface finish |
LEAF | Gold leaf / beaten foil | Surface finish |
SPT | Sputtering target / evaporation slug | Surface finish |
What is 24K?
24K (Au999) is essentially pure gold, unalloyed and therefore the softest and most malleable material in the precious-metal group: 30 MPa yield, 125 MPa tensile, 45 % elongation and about 25 HB. Engineers and refiners specify it for maximum purity, 71 % IACS electrical conductivity and complete corrosion immunity, and it is stocked as cast bars, coin blanks, rolled sheet, beaten leaf and drawn wire. It has no useful structural strength and scratches and dents in normal handling, so wear-facing parts should move to 22K or 18K. 24K 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). 24K 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).
What is 24K used for?
- gold bullion bars
- coins
- traditional Chinese jewelry
- electrical contact plating
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 properties
Typical room-temperature values for 24K-O; bars are the position among precious metal grades.
Physical3
24K 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 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 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 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 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'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. 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. 24K is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 24K
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.
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) |
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.
Equivalent designations
Standards and trade names that resolve to Precious Metal 24K in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ISO
- 9202
- GB (China)
- Au999
- Also called
- 999 Gold
How much does 24K cost?
24K 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.
24K — frequently asked
What is 24K used for?
24K 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?
24K 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 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 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?
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 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?
24K 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.
How much does 24K cost?
24K 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
- 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; 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.