How the Bessemer Process Changed the World of Steelmaking

Bridges constructed after the mid-19th century benefited from the Bessemer process, which expedited steel production like never before. Ditto / Getty Images

The Bessemer process is a steelmaking technique invented during the Industrial Age. Skyscrapers, bridges and colossal machines all became possible thanks to the strength and versatility of steel produced by this technique. Even the rails that connected nations and facilitated the transportation revolution owe their existence to this innovative technique.

While there have been many advancements since the emergence of steelmaking, the Bessemer process sparked a wave of industrialization that continues to affect our lives.

What Was the Bessemer Process?

The Bessemer process was a steelmaking method developed by Sir Henry Bessemer in the 1850s that revolutionized the production of steel. The method involved steelmakers heating pig iron in a furnace to reach a specific temperature. Once the burning iron became molten, it was transferred to the Bessemer converter, which was like a fiery battleground where molten iron transformed.

The conversion process was rapid, typically taking around 20 minutes. The resulting steel had a low carbon content, making it suitable for the production of railroad tracks, bridges and machinery.

While the Bessemer process played a crucial role in the past, it has been replaced by more advanced and efficient techniques for making steel. Nowadays, the steel industry employs newer methods like the basic oxygen furnace and electric arc furnace, which offer better control and flexibility in producing various types of steel.

Who Invented the Bessemer Process?

In 1856, Sir Henry Bessemer, an accomplished inventor and engineer, invented the Bessemer process. After gaining experience from working with the open hearth process — which involved heating a mixture of iron and scrap steel in an open hearth furnace — the engineer came up with the idea for a new and improved steelmaking technique.

But he wasn't the only one trying to advance steel production during that time. Another notable figure in this pursuit was William Kelly, an American ironmaster. Independently, Kelly discovered a similar process involving blowing oxygen through molten iron to remove impurities.

However, there were differences between Kelly's and Bessemer's approaches. Kelly's method used a tilting converter, while Bessemer introduced a stationary converter. Additionally, Bessemer's process involved blowing air directly into the molten iron, while Kelly's process used a preliminary heating step before blowing oxygen. Despite these variances, it was Kelly's work that laid the groundwork for further advancements and served as a source of inspiration for Bessemer.

Bessemer built upon Kelly's discoveries and made significant progress in perfecting the steelmaking process. His most notable invention was the Bessemer converter, a crucial component in his method. By blowing oxygen through molten pig iron in the converter, Bessemer removed impurities and was able to transform wrought iron into high-quality steel. He also introduced innovative techniques to control airflow and temperature, making large-scale steel production more efficient and practical.

And last but not least, the skilled metallurgist Robert Mushet suggested the addition of spiegeleisen, an iron alloy, to the converter. This addition significantly enhanced the quality and strength of the resulting steel, further contributing to the effectiveness of the Bessemer process.

How the Bessemer Process Worked

A few crucial steps bring molten iron to life, culminating in the creation of high-quality steel. Here's a look at the Bessemer process in action:

First, the steelmaker heats the iron in a furnace until it reaches a molten state, transforming it from solid to liquid form. The intense heat within the furnace causes the iron to melt, preparing it for the subsequent steps of the Bessemer process.
Once the iron becomes molten, it is carefully poured into a specialized container known as the Bessemer converter. This vessel is designed to withstand the extreme temperatures and pressures involved in the process.
With the molten iron in the converter, a powerful blast of air is blown through it. This air initiates a chemical reaction that burns off impurities, such as excess carbon, present in the iron. The reaction releases intense heat, aiding in the elimination of impurities and the formation of steel.
As the impurities burn, they combine to form a layer of waste material called slag. This slag, being less dense than the molten iron, floats on top and is later removed from the surface. The separation of slag is similar to the way liquidized fat rises and can be skimmed from the surface of a pot of beans or soup.
To enhance the strength and quality of the steel, a small quantity of manganese is often added to the molten iron. Manganese serves multiple purposes, including improving the overall quality of the steel and helping to remove any remaining oxygen that could negatively impact its properties.

Steel Production and the Industrial Revolution

The invention of the Bessemer process brought about significant changes in the steel industry, revolutionizing steel production and its impact on various sectors:

Establishing the steel mill industry: After obtaining the first patent for his technique, Bessemer worked with various industrial partners and set up steel mills equipped with Bessemer converters to efficiently manufacture steel. These mills were specifically designed to implement the new process on a large scale and efficiently produce steel. The successful operation of these mills contributed to the widespread adoption of his steelmaking technique.
Efficiency and cost reduction: The Bessemer process dramatically increased the efficiency of steel production, reducing both time and costs. It eliminated the labor-intensive manual removal of impurities from heated iron ore, streamlining the process and making it more economically viable.
Advancements in construction: The availability of affordable steel transformed the construction industry. Compared to iron, Bessemer steel was stronger and more durable, making it ideal for building bridges, railways and skyscrapers. This advancement allowed for the construction of larger, taller, and more resilient structures, shaping the modern urban landscape.
Growth in manufacturing: The mass production of steel fueled the growth of the manufacturing sector. Steel became a vital material for machinery, tools, and consumer goods production. Industries flourished as the availability of steel facilitated increased productivity and expanded manufacturing capabilities.
Economic development: The accessibility of cost-effective steel played a pivotal role in economic development. Its widespread use in construction and manufacturing drove industrial expansion, technological innovation and urbanization. Steel laid the foundation for the development of transportation systems, enabling efficient trade and connecting regions on a larger scale.

This article was created in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.