Carbon steel is a metal alloy that combines iron and carbon. The various uses of carbon steel depend on the amount of carbon added to the alloy; for instance, carbon steel with the lowest amount of carbon is called wrought iron and is used for things like fencing. Medium-carbon steel, also called mild steel, is the type of steel that is used for structural purposes in buildings and bridges. High-carbon steel is used for springs and steel wires, while ultra-high carbon steel is called cast iron and is often used to make pots.
There are two types of steel alloy that are typically familiar to the average person: carbon steel and stainless steel. Carbon steel combines iron with carbon, while stainless steel combines iron with chromium. It is easy for most people to identify stainless steel, because the chromium creates a shiny coating over the metal that is reflective and nonporous, making stainless steel simple to clean and decorative. One of the common definitions of carbon steel is any steel that is not stainless.
The carbon in carbon steel makes the metal harder and stronger than stainless steel, but it is also less malleable. Adding greater quantities of carbon to the alloy mixture results in carbon steel that is increasingly harder and more brittle. There are four categories of carbon steel that are distinguishable by the amount of carbon added to the alloy mixture. The uses of carbon steel depend on this category classification.
Carbon steel with the lowest carbon content is typically called wrought iron; the metal is hard, but not brittle. This type of carbon steel is used for fences, chain links, gates and railings. Its lower carbon content means that it has the flexibility to be “worked” into designs for ornamental purposes.
The most commonly used carbon steel has a medium carbon content; uses of carbon steel in this category include structural steel to build buildings and bridges. It is also used for parts in consumer products like automobiles, refrigerators and washing machines. Ships use medium-carbon steel as a structural component.
High-carbon steel is hard but brittle and less easily worked. The uses of carbon steel in this category are typically for manufacturing purposes. This type of carbon steel is often used to create springs and high-strength wires. The increased hardness makes this category of steel ideal for cutting tools, punches, dies and industrial knives.
Carbon steel with ultra-high carbon content is commonly referred to as cast iron. This type of cast iron is very hard but highly brittle. It has little to no malleability and cannot be easily welded or tooled. Often, it is used for cast iron pots, hot water radiators and certain types of lamp posts. Industrially, this type of carbon steel is used for castings, because the high carbon content lowers the melting point.