Types of carbides in white cast iron

The Types of Carbon in Wrought Iron

Wrought Iron is an important form of iron mostly used in the late 18th and early 19th centuries. This type of iron was generally used in manufacturing items such as tools and furniture, and it is also a popular material for decorative railings, grilles and gates.

A key difference between wrought iron and cast iron is the presence of carbon. Wrought iron is heavily processed and manipulated, compared to cast iron which contains more impurities and a higher carbon content. The carbon in wrought iron provides strength and hardness to the material.

The carbon in wrought iron occurs in two distinct forms: free carbon and bound carbon.

Free carbon is the most abundant type of carbon found in wrought iron. This carbon is typically present in the form of graphite flakes. Free carbon is primarily used as a lubricant enabling iron to be hammered and bent, allowing it to be used for manufacturing items with intricate designs and shapes. However, free carbon is also responsible for reducing the durability of the material, making it vulnerable to corrosion and wear.

Bound carbon is different from free carbon as it is found within the matrix of the iron itself. This type of carbon is generally introduced into the wrought iron during the manufacturing process by the addition of carbon compounds such as charcoal and lime. The presence of bound carbon increases the hardness, strength and durability of the material but also makes it more brittle, making it less suitable for intricate shaping.

The type and amount of carbon found in wrought iron is highly dependent on its origin. Wrought iron produced in different parts of the world typically contains different ratios of free to bound carbon.

Historically, Britain was renowned for its superior quality wrought iron which contained almost solely bound carbon. This high-quality iron was heavily used in many notable British buildings such as the Houses of Parliament and Buckingham Palace.

American wrought iron was produced using lower temperatures, resulting in a material containing more free carbon and a lower level of strength and durability. American wrought iron is widely used in 19th-century American architecture, most notably in items such as the early skyscrapers of New York City.

Today, wrought iron can be found in a range of industries, both historically and modern. The presence of free and bound carbon helps to determine the suitability of wrought iron for various uses and applications, making it a popular choice for architects, engineers and designers.

Cast iron is a type of metallic alloy which contains more than 2.14 percent of carbon by weight. It is one of the most widely used ferrous materials in engineering, due to its relatively low cost, high strength, and machinability. At room temperature, cast iron consists of compounds of iron, carbon, and silicon in varying proportions. In the production of cast iron, the carbon and silicon content is greatly increased compared to regular steel. This increase of carbon and silicon content gives cast iron its unique properties.

The carbon content of cast iron can range anywhere from 2.14 up to 4.5 percent by weight, depending on the type of cast iron being produced. The most common type of cast iron is grey cast iron, which typically contains more than 3.0 percent carbon, giving it a characteristic grey colour. When grey cast iron is heated, spherical graphite structures form within the range of 2-4μm. The presence of graphite gives grey cast iron its distinctive properties such as greater strength, softer structure, and improved damping when compared to regular steel.

Another common type of cast iron is ductile or nodular cast iron. This type of cast iron has very little free carbon present and contains a significant amount of graphite present as nodules or spheroids. The presence of graphite nodules gives ductile cast iron superior ductility and greater strength when compared to regular steel. Ductile cast iron is typically used for applications where greater strength and ductility is required.

White cast iron is a relatively rare low-carbon cast iron containing less than 2.14 percent carbon by weight. In comparison to other cast iron types, white cast iron lacks graphite, resulting in a more hardened material with higher tensile and fatigue strength. Because of its increased strength, white cast iron is often used in applications such as cutting tools, ball mill liners, and pump impellers.

In summary, cast iron is a ferrous alloy consisting of iron, carbon, and silicon, with a carbon content ranging anywhere from 2.14 to 4.5 percent by weight. The type of cast iron used in most engineering applications is grey cast iron, which consists of more than 3.0 percent carbon, giving it a characteristic grey colour and spherical graphite structures. Ductile cast iron, with relatively little free carbon present, is often used for applications that require greater strength and ductility. Finally, white cast iron, containing less than 2.14 percent carbon, is commonly used for its increased strength, making it popular in applications such as cutting tools, ball mill liners, and pump impellers.