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Gunmetal

What is Gunmetal (Red Brass)

Gunmetal, occasionally called ‘red brass’ in the US, is an alloy made from copper, zinc, and tin [1, 2]. Aside from its basic constituents, modified forms may have nickel and lead, which are classified as ‘nickel gunmetal’ and ‘leaded gunmetal’ [2]. Because of good strength, corrosion resistance, and ease of casting, gunmetal has been widely used for thousands of years [2].

Gunmetal Casting

Composition

The chemical composition of gunmetal can be varied [1, 2]. Here we have shared the components of Admiralty Gunmetal:

Copper 88% [3]
Tin 10% [3]
Zinc 2% [3]

Modified gunmetal may contain up to 7 percent lead and up to 6 percent nickel [2] while the copper alloy C90300 or G Bronze comprises 8 percent tin and 4 percent zinc [4].

Red Brass

Properties and Characteristics of Gunmetal

Physical Properties

Color/appearance Gray with bluish or purplish tinge [5]
Density 8.72 X 103 kg/m3 [6]
State of matter at room temperature Solid [7]
Electric resistivity 15.6 X 10-8 Ohm-m [6]
Modulus of elasticity 103 GPa [6]
Thermal expansion (at 20 °C) 19.8 X 10-6 °C-1 [6]
Thermal conductivity 74.8 W/mK [6]
Specific heat capacity 377 J/kgK [6]
Yield strength 152 MPa [6]
Tensile strength 310 MPa [6]
Elongation 25% [6]
Fatigue strength 90 MPa [6]
Liquidus temperature 999 °C [6]
Solidus temperature 854 °C [6]
Hardness 75 HB(500) [6]
Gunmetal Bushing

Uses

  • Intricate, pressure-tight castings like pipe fittings, valves, and pumps are made from gunmetal [8].
  • It is now commonly used for making statues [8].
  • Bearings, where speeds and loads are moderate, are manufactured from gunmetal and used in machinery [7, 8].

Cost

The scrap price is about $1.8 per pound of gunmetal [9]

References

  1. Gunmetal – Diracdelta.co.uk
  2. Gunmetals – Copperalliance.org.uk
  3. Red Brass/Gunmetals – Copper.org
  4. C90300 (SAE 620) Tin Bronze – Anchorbronze.com
  5. Gunmetal – Dictionary.com
  6. Cast copper alloy C90500 (Gun Metal) – Substech.com
  7. Gunmetal (CuSnZnPb) – Oecam.eu
  8. Gunmetals – Copperalliance.eu
  9. Red Brass Scrap Price – Scrapmonster.com

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