How is Carbon Steel Made?

July 22, 2022
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The Characteristics of Steel


What is often misunderstood about carbon steel is that it is not a singular metal. The term carbon steel actually describes a range of steel with varying levels of carbon and other materials that provide the steel’s crystalline structure with certain properties. The most plentiful ingredient in any steel is Iron. Ratios of carbon, manganese, aluminum, and the like are added to give the steel the best characteristics and properties for its intended use. This range of metals is usually divided into three categories: low carbon steel, medium carbon steel, and high carbon steel.

Low Carbon Steel – It has 0.04 and 0.3 percent carbon and is extremely versatile. It’s easy to weld, cut, and shape, making it the perfect choice for tasks requiring strength and shaping. It has enough carbon to make it hard and durable, but not brittle.

Medium Carbon Steel – It has from 0.31 to 0.6 percent carbon. This yields a harder steel, more resistant to cutting and welding. This kind of steel is often formed and shaped before being heat treated, tempered, or cryogenically processed to further harden or refine the metal.

High Carbon Steel – It aside from a carbon percentage that can run as high as 1.5 percent, the alloys added to this steel are usually meant to further increase the hardness. Steel of this quality is commonly called “tool steel” and is incredibly hard and brittle. Further heat treatment makes it more so, but the tools made from this metal are durable and unyielding.


Production Process


Humans have been making steel for centuries.The current method of steel production is the Basic Oxygen Steelmaking Process (BOS).


The BOS process begins with recycled or scrap steel in the BOS furnace. Molten iron is poured over the scrap. This becomes the melt. An oxygen lance is lowered to just over the surface of the liquid metal, and almost pure oxygen is blown through at twice the speed of sound while compounds such as flux and lime are added. This causes impurities in the melt to oxidize, forming a frothy slag on top of the liquid metal. This process will continue for about twenty minutes. While in the furnace, data allows small adjustments to the formula to be made based on temperature and the material’s behavior.

Once complete, the metal is sampled to ensure it meets the needed specifications before being poured into another vessel called a ladle. The ladle will hold the steel while it heats in the ladle furnace and alloys are added to create the final steel composition. Once finished, the metal is poured into various shaping apparatus to create the basic form–sheet, bar, or tube–that is needed. Through this process, the labor requirements have been reduced a thousandfold, which is what has helped make steel one of the most economical metals available.