Differences Between Wrought and Cast Iron


Even though you probably think that cast iron refers to all work with iron, that is not true, and you are wrong. The basic idea is that cast iron is iron that has been melted, placed in a mold and that allowed it to cool.

On the other hand, wrought iron has been heated and worked with tools, which is the main reason for its name, because wrought was a principle of producing this particular type of iron.

That is why most manufacturers areusing this particular material to make wrought iron gates because they are much more efficientwhen compared with other iron types.

But let’s start from the very beginning:

Cast Iron

When it comes to cast iron, this is a generic term that refers to a wide range of iron alloys. In most cases, it is associated with gray iron, which is one of the most common ones in the market.

While it can sound that it is pure iron, it contains 2 to 4{c4b240ad2745788582b22e963ff2ce8ac972ba04ed67507b8ee2e426fe937f99} of carbon, as well as small amounts of manganese and silicon. It can include other impurities such as phosphorus and sulfur as well.

The formation of cast iron starts by smelting iron ore, as well as melting pig iron, and mixing it with alloys and scrap metals. Afterward, the idea is to pour the liquid into molds and let it solidify and cool down.

It features high carbon content, so it is a different alloy, which means that it features a wide array of materials that will affect its microstructure as well as physical properties in overall. For instance, cast iron features carbon particles that feature microstructure of graphite flakes that will combine with metal cools.

Since graphite is low in hardness and density, it won’t provide these properties, but it is high in lubricity, so it will offer structural advantage without compromising the iron matrix. When compared with wrought iron, cast iron is hard, brittle and non-malleable.

You cannot stretch, bend or hammer it into some shape you want. It also features weak tensile strength, which means that it will fracture before it distorts and warps. It features excellent power, and the most common usage is in building construction before the emergence of the steel industry.

It features low melting point when compared to steel, but it is less reactive and more fluid which means that it can mold with materials, so it is perfect for casting.

However, it requires less labor-intensive process than making wrought iron, so that was the main reason for its massive productive in 18th and 19th century. However, steel has replaced the cast iron in the construction industry, but it is still the main component for many industrial applications.

Wrought Iron

When it comes to wrought iron, it features pure iron in combination with 1 to 2{c4b240ad2745788582b22e963ff2ce8ac972ba04ed67507b8ee2e426fe937f99} of added slag, which is a byproduct of iron ore. In general, it is a mixture of phosphorous, aluminum, sulfur and silicon oxides.

During the manufacture, the idea is to remove the iron from the heat and work with it with a  hammer until it reaches the final form you intended in the first place. It features characterization due to its fibrous appearance, so it is way more ductile and softer when compared with cast iron.

Wrought iron is malleable, which means that you can heat it and reheat it and make various shapes. Have in mind that more you work on it, the stronger it gets as a result. It features more significant tensile strength when compared with cast iron, so it is more suitable for horizontal beams.

If you want to learn more onhistorical significance of wrought iron, you should check here.

It resists fatigue, but it can deform in case of overload beyond its capacity, or it can be distorted due to intense heat exposure. It is widely used in the 19th century for building construction, but in the 20th century, the steel replaced it entirely. Today, it is mostly made for decorative applications.

What About Corrosion?

Both wrought and cast iron are susceptible to corrosion as soon as bare surfaces get exposed to oxygen and moisture. Unlike other materials that are used on a daily basis, they do not have a protective oxidative coating, so it will be challenging to use them for humid outdoor environments.