Introduction
Gun metal, also known as red brass or phosphor bronze, is a type of bronze alloy primarily composed of copper, tin, zinc, and lead. It has been used for centuries, originally in the manufacture of cannons—hence the name “gun metal.” Today, gun metal is widely used in engineering applications for its excellent corrosion resistance, strength, and machinability.
With growing awareness of sustainability and metal conservation, gun metal scrap has become an important material in the metal recycling industry. Recycling this alloy not only reduces environmental impact but also provides significant economic benefits.
Composition of Gun Metal Scrap
Typical composition of gun metal (by percentage):
- Copper (Cu): 85–88%
- Tin (Sn): 5–8%
- Zinc (Zn): 2–5%
- Lead (Pb): 2–5%
These proportions can vary depending on the specific grade or application. The high copper content gives the alloy its characteristic reddish-golden appearance and corrosion resistance, while tin and lead enhance strength and lubricity.
Sources of Gun Metal Scrap
Gun metal scrap is generated from various industries and applications, including:
- Old machinery parts such as bearings, bushings, valves, and pump components.
- Foundry and casting waste, including risers, runners, and rejected castings.
- Marine equipment like propellers, ship fittings, and bearings.
- Plumbing and sanitary fittings (valves, taps, connectors).
- Electrical and mechanical workshops where bronze components are machined.
Scrap is typically collected, sorted, cleaned, and melted for reuse in foundries or alloy plants.
Properties and Advantages
Gun metal offers a combination of properties that make it valuable both as a primary alloy and as recyclable scrap:
- High corrosion resistance, especially in marine and moist environments.
- Excellent casting and machining qualities.
- Good wear resistance and anti-friction properties.
- High strength and durability.
- Ease of recycling without significant loss of quality.
Because the alloy retains its properties even after multiple recycling cycles, gun metal scrap is a highly sought-after non-ferrous material.
Recycling Process of Gun Metal Scrap
- Collection & Sorting: Scrap is collected from industrial sources and segregated based on alloy composition.
- Cleaning: Removal of oil, grease, paint, or other contaminants.
- Melting: The cleaned scrap is melted in induction or crucible furnaces.
- Alloy Adjustment: Composition is checked and adjusted with pure copper, tin, or zinc to meet required standards.
- Casting: The molten metal is cast into ingots or directly used for manufacturing new products