Bronze vs Cast Iron

Bronze and cast iron are traditional materials that have been used for centuries to produce weapons, cooking vessels, parts for marine and locomotive vehicles, engineering structures, and decorative items like statues and architectural finishes.

But what makes these two materials different? And why would you decide to choose one over the other? Let’s look at some of the things that identify these materials and why they are better suited to particular applications…

First of all, we’ll take a look at the different types of bronze and cast iron…

Explaining the Different Types of Bronze

There are lots of different types of bronze, produced using different combinations of elements. The blend used will produce a material with distinct hardness, ductility and flexibility properties. The following are some of the more common types of bronze:

• Aluminium Bronze – 82.7% copper, 4% iron, 9-14% aluminium and offering advanced corrosion resistance and greater strength. This type of bronze is well suited to marine equipment.
• Phosphor Bronze – 95% copper, 0.5-11% tin, 0.01-0.35% phosphorous. Phosphor bronze has increased toughness, resistance and better casting capability.
• Silicon Bronze – 94-96% copper, 2.5-6% silicon, 0.3-1.4% iron, producing a bronze with a high corrosion resistance and smooth finish. The presence of silicon also improves its tensile strength.
• Nickel Aluminium Bronze – 79% copper, 8.5-9.5% aluminium, 3.5-4.5% nickel. Improved strength, good ductility and high resistance to corrosion make this type of bronze a common choice in marine, aerospace and other diverse applications.
• Bismuth Bronze – 87-91% copper, 1-6% bismuth, 1%nickel, 2-4% tina and zinc. This is a lead-free bronze which pairs well with industries linked to recycling and concerned with other lead-based issues.
• Bearing Bronze – 81-85% copper, 6-8% lead, 6.3-7.5% tin and 2-4% zinc. This type of bronze is more suited to light-duty purposes as it has a low tensile strength and fairly good machinability.
• Tin Bronze — 89% copper, 11% tin. This type of alloy is more expensive, but it offers good mechanical properties and is suitable for machine components.
• Manganese Bronze – 60-68% copper, 25% zinc, 3-7.5% aluminium, 2.5-5% manganese and 2-4% iron, and offering excellent strength and resistance. It is difficult to machine, but its advanced strength outweighs this and makes it crucial in many applications.
• Copper-Nickel Bronze – 90% copper, 2-30% nickel. Has superior corrosion resistance, durability and thermal properties.

Bronze and Cast Bronze

Bronze is an alloy made from copper and other metal(s) such as tin. The tin is mined and smelted and then mixed with hot copper. Traditionally, bronze was worked using a hammering method.

Cast bronze is heated in a furnace, after which the molten material can be cast into different moulds. Cast bronze is stronger, more durable and easier to shape into detailed designs. This type of bronze is often used to produce statues and other ornamental items.

What Are The Different Types of Cast Iron?

Cast iron is an alloy produced by smelting pig iron with a small amount of carbon, silicon and manganese. There are four types of cast iron:

• Gray Iron – Characterised by its graphite flakes, gray iron offers excellent compressive strength and damping capacity, making it suitable for applications such as engine blocks and machine bases.
• Ductile Cast Iron – Also known as nodular or spheroidal graphite iron, ductile cast iron exhibits improved ductility and toughness compared to gray iron, thanks to its nodular graphite structure. This makes it ideal for components requiring high tensile strength and impact resistance, such as automotive parts and pipes.
• White Cast Iron – With its absence of graphite, white cast iron boasts exceptional hardness and wear resistance, making it suitable for applications involving abrasion and high-stress conditions, such as crushing machinery and wear-resistant parts.
• Malleable Cast Iron – typically produced from white cast iron that is heated for two days and then cooled. The resulting material is easier to mould into different shapes and sizes.