Copper Alloy CC491K-GM
Finish state
EN CC491K · UNS C83600 · GB ZCuSn5Pb5Zn5 · BS LG2
GM = permanent mould (chill/gravity die) cast
Pick for medium-volume small parts needing finer grain, better surface and tighter dimensions than sand cast.
Values for the GM condition
Other CC491K tempers and conditions
CC491K is listed in 5 conditions; see the grade overview at CC491K.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
GSDefault Sand cast | Standard route for valve bodies, pump housings and one-off/short-run engineering castings. | 115 | 250 | 25 | 60 HB | 15 % IACS |
Investment / precision cast | Use for small, intricate near-net-shape parts where machining allowance must be minimal. | 115 | 250 | 18 | 62 HB | 15 % IACS |
GMThis page Permanent mould (chill/gravity die) cast | Pick for medium-volume small parts needing finer grain, better surface and tighter dimensions than sand cast. | 120 | 250 | 12 | 65 HB | 15 % IACS |
Centrifugally cast | Best for bushings, sleeves and rings where a dense, porosity-free tubular section is required. | 130 | 270 | 14 | 65 HB | 15 % IACS |
Continuously cast bar/tube | Stock-bar and hollow-bar form: highest and most uniform strength, ideal for machined bushings and fittings. | 140 | 275 | 15 | 70 HB | 15 % IACS |
What is CC491K-GM?
CC491K-GM is CC491K supplied in the GM condition — pick for medium-volume small parts needing finer grain, better surface and tighter dimensions than sand cast. CC491K-GM has a yield strength of 120 MPa (17.4 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 79% of copper alloy grades. Elongation at break is 12% and the elastic modulus is 100 GPa (14.5 Msi). CC491K-GM has a density of 8.83 g/cm³ (0.319 lb/in³), heavier than 65% of copper alloy grades. It melts at 854°C (1,569 °F). GS is the default condition FabDigit quotes; GM is available on request or by drawing note.
Advantages
- Easy to machine — 85/100, better than 93% of copper alloy grades
Limitations
- Hard to polish — 65/100, worse than 87% of copper alloy grades
- Low stiffness — 100 GPa (14.5 Msi), worse than 82% of copper alloy grades
- Low strength — 120 MPa (17.4 ksi), worse than 79% of copper alloy grades
- Limited formability — 15/100, worse than 79% of copper alloy grades
- Difficult to weld — 25/100, worse than 78% of copper alloy grades
CC491K-GM properties
Typical room-temperature values for CC491K-GM; 21 are specific to this condition. Other listed values are CC491K reference data and may not represent this condition. Bars are the position among copper alloy grades.
Physical3
CC491K-GM has a density of 8.83 g/cm³ (0.319 lb/in³), heavier than 65% of copper alloy grades. It melts at 854°C (1,569 °F).
Mechanical15
CC491K-GM has a yield strength of 120 MPa (17.4 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 79% of copper alloy grades. Elongation at break is 12% and the elastic modulus is 100 GPa (14.5 Msi).
Thermal6
CC491K-GM is rated for continuous service to 200°C (392 °F). It conducts heat at 72 W/m·K (41.6 BTU/hr·ft·°F), worse than 52% of copper alloy grades. Thermal expansion is 18 µm/m·K (10 µin/in·°F).
Electrical3
CC491K-GM conducts electricity at 15 % IACS, worse than 54% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (71/100), better than 80% of copper alloy grades.
Sustainability4
Producing a kilogram of CC491K-GM takes about 52 MJ of energy and emits 3.6 kg of CO₂ — less than 87% of copper alloy grades. Typical recycled content is 80%.
Manufacturability7
CC491K-GM's machinability is excellent (85/100, better than 93% of copper alloy grades); weldability poor (25/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with CC491K-GM
Is CC491K easy to machine?
Excellent free-machining behaviour (≈84 % of free-cutting brass) with short chips from the lead phase; use sharp, zero-to-positive rake tools, high speed and light feed, flood coolant.
Can CC491K be welded?
Essentially unweldable by fusion processes because lead causes hot cracking and porosity; repair by brazing/soldering or specialised low-heat braze welding, and never use for pressure-retaining welds.
Can CC491K be formed, bent or molded?
Cast-only alloy with wide freezing range — feed with generous risers and chills for pressure tightness; pour ~1100–1180 °C, degas and avoid excessive superheat to limit Zn/Pb loss.
What surface finishes work on CC491K?
Takes a good buffed bronze lustre and accepts nickel/chrome or tin electroplating after careful lead-smut removal; can be chemically patinated or lacquered, no anodizing.
CC491K 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 |
|---|---|---|
| CuEN 1982 CC491K; ASTM B62 C83600 gives 84.0–86.0 | 84 – 86 | 85 |
| Sn | 4 – 6 | 5 |
| Pb | 4 – 6 | 5 |
| Niincl. Co | ≤ 2 | — |
| Fe | ≤ 0.3 | — |
| Sb | ≤ 0.25 | — |
| S | ≤ 0.1 | — |
| P | ≤ 0.05 | — |
| Al | ≤ 0.01 | — |
| Si | ≤ 0.01 | — |
| Mn | ≤ 0.2 | — |
| Total impurities | ≤ 1 | — |
| Znbalance in EN 1982 | ≥ 4 (balance) | — |
CC491K-GM — frequently asked
What is CC491K-GM used for?
CC491K-GM is typically used for valve bodies, pump housings, plumbing fittings, bearings and general-purpose castings. In short: most castable gunmetal; best-machining cast bronze; lowest-cost general bronze.
What is the yield strength of CC491K-GM?
CC491K-GM has a typical yield strength of 120 MPa (17.4 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 79% of copper alloy grades. Strength varies by condition: see the 5 listed tempers.
Is CC491K-GM easy to machine?
Yes — machinability is rated excellent (85/100, better than 93% of copper alloy grades). Excellent free-machining behaviour (≈84 % of free-cutting brass) with short chips from the lead phase; use sharp, zero-to-positive rake tools, high speed and light feed, flood coolant.
Can CC491K-GM be welded?
Not readily — weldability is rated poor (25/100). Essentially unweldable by fusion processes because lead causes hot cracking and porosity; repair by brazing/soldering or specialised low-heat braze welding, and never use for pressure-retaining welds.
What surface finishes work on CC491K-GM?
Takes a good buffed bronze lustre and accepts nickel/chrome or tin electroplating after careful lead-smut removal; can be chemically patinated or lacquered, no anodizing.
Can CC491K-GM be formed, bent or molded?
Cast-only alloy with wide freezing range — feed with generous risers and chills for pressure tightness; pour ~1100–1180 °C, degas and avoid excessive superheat to limit Zn/Pb loss.
What is the maximum service temperature of CC491K-GM?
CC491K-GM 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 CC491K-GS and CC491K-GC?
GS is the default condition — standard route for valve bodies, pump housings and one-off/short-run engineering castings. GC: stock-bar and hollow-bar form: highest and most uniform strength, ideal for machined bushings and fittings. Yield strength is 115 MPa in GS versus 140 MPa in GC.
Sources
- EN 1982 — Copper and copper alloys: Ingots and castings (CC491K) — CEN (2017)
- ASTM B62 — Composition Bronze or Ounce Metal Castings (C83600) — ASTM International (2017)
- GB/T 1176 — (ZCuSn5Pb5Zn5) — SAC (2013)
- CDA Alloy Datasheet C83600 — Copper Development Association (copper.org) (2023)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
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.