Precious Metal 18K-H04
Supply condition
JIS K18 · GB Au750 · ISO 9202
H04 = full hard
Use for spring clasps, earring posts, watch bracelet links and any part needing wear and dent resistance.
Values for the H04 condition
Other 18K tempers and conditions
18K is listed in 10 conditions; see the grade overview at 18K.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
18K Green | Binary Au-Ag greenish-yellow alloy used for colour contrast and enamelling; very soft and not age-hardenable. | 90 | 250 | 45 | 57 HB | 18 % IACS |
As cast | Pick for cast jewelry bodies and settings straight out of the flask, before work-hardening or ageing. | 220 | 380 | 18 | 138 HB | 15.5 % IACS |
ODefault Annealed | Standard stock condition for 18K yellow sheet, wire, tube and chain — maximum ductility for forming, drawing and setting. | 240 | 450 | 38 | 143 HB | 16 % IACS |
18K Yellow | Classic yellow colour family — the default 18K alloy for chain, sheet and casting worldwide. | 240 | 450 | 38 | 143 HB | 16 % IACS |
18K Red/Rose | Copper-rich pink to red colour; hardest of the Au-Ag-Cu family and strongly age-hardenable, but most prone to fire-scale and tarnish. | 300 | 500 | 30 | 162 HB | 14 % IACS |
18K White, nickel-based | Low-cost, hard and springy white gold for stamped and machined parts; requires rhodium plating for true white and must meet EU nickel-release limits. | 350 | 620 | 25 | 190 HV | 45 W/m·K |
Half hard | Compromise temper for hinges, pin stems and stampings that must hold shape but still bend without cracking. | 480 | 600 | 12 | 176 HB | 15 % IACS |
18K White, palladium-based | Hypoallergenic, naturally grey-white and very ductile — premium white gold for high-end settings, but heavy, expensive and high-melting. | — | 480 | 35 | 130 HV | — |
H04This page Full hard | Use for spring clasps, earring posts, watch bracelet links and any part needing wear and dent resistance. | 680 | 760 | 3 | 17 HRC | 14.5 % IACS |
Age-hardened | Highest hardness route for Au-Ag-Cu yellow/rose grades — ordering of AuCu gives wear resistance for rings and watch cases without cold work. | 750 | 880 | 9 | 24 HRC | 15 % IACS |
What is 18K-H04?
18K-H04 is 18K supplied in the H04 condition — use for spring clasps, earring posts, watch bracelet links and any part needing wear and dent resistance. 18K-H04 has a yield strength of 680 MPa (98.6 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 100% of precious metal grades. Elongation at break is 3% and the elastic modulus is 81 GPa (11.7 Msi). 18K-H04 has a density of 15.5 g/cm³ (0.56 lb/in³), heavier than 77% of precious metal grades. It melts at 885°C (1,625 °F). O is the default condition FabDigit quotes; H04 is available on request or by drawing note.
Advantages
- High strength — 680 MPa (98.6 ksi), better than 100% of precious metal grades
- Easy to machine — 65/100, better than 100% of precious metal grades
- Polishes to a fine finish — 98/100, better than 98% of precious metal grades
Limitations
- Limited service temperature — 170°C (338 °F), worse than 100% of precious metal grades
- Limited ductility — 3%, worse than 95% of precious metal grades
- Limited formability — 30/100, worse than 94% of precious metal grades
- High embodied carbon — 15,000 kg CO₂/kg, worse than 94% of precious metal grades
- Heavy — 15.5 g/cm³ (0.56 lb/in³), worse than 77% of precious metal grades
18K-H04 properties
Typical room-temperature values for 18K-H04; 23 are specific to this condition. Other listed values are 18K reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
18K-H04 has a density of 15.5 g/cm³ (0.56 lb/in³), heavier than 77% of precious metal grades. It melts at 885°C (1,625 °F).
Mechanical16
18K-H04 has a yield strength of 680 MPa (98.6 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 100% of precious metal grades. Elongation at break is 3% and the elastic modulus is 81 GPa (11.7 Msi).
Thermal6
18K-H04 is rated for continuous service to 170°C (338 °F). It conducts heat at 143 W/m·K (82.6 BTU/hr·ft·°F), better than 65% of precious metal grades. Thermal expansion is 15.5 µm/m·K (8.61 µin/in·°F).
Electrical3
18K-H04 conducts electricity at 14.5 % IACS, worse than 68% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 73% of precious metal grades.
Sustainability4
Producing a kilogram of 18K-H04 takes about 190,000 MJ of energy and emits 15,000 kg of CO₂ — more than 81% of precious metal grades. Typical recycled content is 35%.
Manufacturability8
18K-H04's machinability is good (65/100, better than 100% of precious metal grades); weldability very good (70/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18K-H04
Is 18K easy to machine?
Soft and gummy in the annealed state — use sharp polished carbide or single-crystal diamond, high speed, light feed and oil mist; age-hardened or cold-worked stock chips far more cleanly, and all swarf must be collected for refining.
Can 18K be welded?
Laser and pulse-arc micro-welding are routine with matching 18K filler; torch work uses graded karat solders (easy/medium/hard) with fluoride flux, and boric-acid coating prevents fire-scale on Cu-rich colours.
Can 18K be formed, bent or molded?
Excellent cold formability when annealed (≥60 % reduction between 650 °C anneals); investment cast at 950–1050 °C flask/metal for yellow and rose, higher and under protective atmosphere for Pd whites.
What surface finishes work on 18K?
Takes a mirror polish easily; standard finishing chain is pumice/tripoli/rouge, then optional rhodium or ruthenium plating on white golds and matte/satin or sandblast textures for contrast.
18K 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 |
|---|---|---|
| Au750‰ minimum per ISO 9202 / GB 11887; producers aim 75.2–75.5 for assay margin | 75 – 75.8 | 75 |
| Ag12.5 in classic 3N yellow; 25 in green gold; 5–15 in Pd whites | 0 – 25 | 12.5 |
| Cuup to ~25 in 5N red gold; 0 in green and most Pd whites | 0 – 25 | 12.5 |
| Zndeoxidiser / colour and flow modifier, common in white and solder alloys | 0 – 5 | 0.5 |
| Niwhite-gold whitener; EU REACH nickel-release limit applies to skin contact | 0 – 15 | 0 |
| Pdwhitener in hypoallergenic white golds; also grain refiner at 0.1–1 % | 0 – 16 | 0 |
| Ir/Ru/Co/Sigrain refiners and deoxidisers in casting grain | 0 – 0.2 | 0.05 |
| Ag+Cu+otherbalance to 100 %, 250‰ nominal | balance | — |
18K-H04 — frequently asked
What is 18K-H04 used for?
18K-H04 is typically used for fine jewelry, watch cases, wedding rings and luxury goods. In short: most common international karat; age-hardenable gold alloy; widest colour range.
What is the yield strength of 18K-H04?
18K-H04 has a typical yield strength of 680 MPa (98.6 ksi) and a tensile strength of 760 MPa (110 ksi) — stronger than 100% of precious metal grades. Strength varies by condition: see the 10 listed tempers.
Is 18K-H04 easy to machine?
Reasonably — machinability is rated good (65/100, better than 100% of precious metal grades). Soft and gummy in the annealed state — use sharp polished carbide or single-crystal diamond, high speed, light feed and oil mist; age-hardened or cold-worked stock chips far more cleanly, and all swarf must be collected for refining.
Can 18K-H04 be welded?
Yes — weldability is rated very good (70/100). Laser and pulse-arc micro-welding are routine with matching 18K filler; torch work uses graded karat solders (easy/medium/hard) with fluoride flux, and boric-acid coating prevents fire-scale on Cu-rich colours.
What surface finishes work on 18K-H04?
Takes a mirror polish easily; standard finishing chain is pumice/tripoli/rouge, then optional rhodium or ruthenium plating on white golds and matte/satin or sandblast textures for contrast.
Can 18K-H04 be formed, bent or molded?
Excellent cold formability when annealed (≥60 % reduction between 650 °C anneals); investment cast at 950–1050 °C flask/metal for yellow and rose, higher and under protective atmosphere for Pd whites.
What is the maximum service temperature of 18K-H04?
18K-H04 is rated for continuous use to about 170°C (338 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 18K-O and 18K-AH?
O is the default condition — standard stock condition for 18K yellow sheet, wire, tube and chain — maximum ductility for forming, drawing and setting. AH: highest hardness route for Au-Ag-Cu yellow/rose grades — ordering of AuCu gives wear resistance for rings and watch cases without cold work. Yield strength is 240 MPa in O versus 750 MPa in AH.
Sources
- ISO 9202 Jewellery and precious metals — Fineness of precious metal alloys — ISO (2019)
- Introduction to Precious Metals: Metallurgy for the Jeweller & Silversmith (M. Grimwade) — Brynmorgen Press (2009)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Precious Metals) — ASM International (1990)
- Gold Bulletin / Santa Fe Symposium on Jewelry Manufacturing Technology proceedings — World Gold Council / Met-Chem (2020)
- Karat gold master alloy technical sheets (18K yellow/red/white) — Legor Group / Progold / Hoover & Strong (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.