What Is Steel? A Comprehensive Guide to the World’s Most Important Metal Alloy

Introduction

Steel is everywhere in our modern world. From the cars we drive to the buildings we live and work in, from the appliances in our homes to the tools we use every day, steel is an essential part of our lives. It’s no exaggeration to say that without steel, our world would be a very different place. But what exactly is steel, and why is it so important? In this post, we’ll dive deep into what steel is, how it’s made, its properties, types, uses, and more.

What is Steel?

Rank	Country	Crude Steel Production (million metric tons)
1	China	1,032.8
2	India	118.2
3	Japan	96.3
4	United States	85.8
5	Russia	75.6
6	South Korea	70.4
7	Turkey	40.4
8	Germany	40.1
9	Brazil	36.2
10	Iran	28.5

At its core, steel is an alloy of iron and carbon. An alloy is a mixture of two or more elements, at least one of which is a metal. In the case of steel, the primary metal is iron, and the key non-metal is carbon. For a material to be considered steel, it must contain between 0.2% and 2.1% carbon by weight. This carbon content is what distinguishes steel from pure iron and gives it many of its unique properties.

The addition of carbon to iron creates a material that is stronger, harder, and more durable than pure iron. The exact properties of steel can be fine-tuned by adjusting the carbon content and by adding other elements such as manganese, chromium, nickel, tungsten, and vanadium. These additional elements are used to create different types of steel with specific properties suited for various applications.

The History of Steel

The history of steel production dates back thousands of years. The earliest known production of steel dates back to around 1800 BCE in the Middle East. However, the steel produced in ancient times was not the same as the steel we know today. It was more akin to wrought iron, which has a very low carbon content.

The modern era of steelmaking began in the 19th century with the development of the Bessemer process. Invented by Henry Bessemer in 1856, this process allowed for the mass production of steel by blowing air through molten pig iron to remove impurities and add carbon. This process revolutionized steel production and paved the way for the widespread use of steel in construction, transportation, and manufacturing.

Since the Bessemer process, there have been numerous innovations in steelmaking, including the development of the open-hearth furnace, the basic oxygen furnace, and the electric arc furnace. These advances have made steel production more efficient, more precise, and more environmentally friendly.

The impact of steel on human civilization cannot be overstated. Steel has played a crucial role in the construction of modern infrastructure, from bridges and skyscrapers to railways and automobiles. It has also been instrumental in the development of modern machinery, tools, and appliances. In many ways, the story of steel is the story of modern industrial society.

How Steel Is Made

The modern steelmaking process is a complex and fascinating one that involves multiple steps and advanced technologies. It all starts with the raw materials: iron ore, coke (a high-carbon fuel made from coal), and limestone. These materials are fed into a blast furnace, which is a giant, cylindrical furnace that can reach temperatures over 1,500°C (2,732°F).

In the blast furnace, the coke is burned to produce carbon monoxide, which reacts with the iron ore to produce molten iron, also known as “pig iron.” The limestone acts as a flux, helping to remove impurities from the iron. The molten iron from the blast furnace is then transferred to a basic oxygen furnace, where it is combined with recycled steel (known as scrap) and small amounts of other elements.

In the basic oxygen furnace, oxygen is blown through the molten metal to remove excess carbon and other impurities. This process, known as “blowing,” takes about 20 minutes and results in liquid steel. The exact composition of the steel can be adjusted at this stage by adding other elements.

An alternative to the basic oxygen furnace is the electric arc furnace, which uses high-power electric arcs to melt recycled steel and is often used for producing specialty steels.

After the steel is produced in the furnace, it is cast into solid forms. Continuous casting is the most common method, where the molten steel is poured into a mold and cooled into a solid slab, bloom, or billet. These semi-finished products are then processed further by rolling, shaping, and heat treating to produce the final steel products.

The Properties of Steel

Steel is known for its remarkable properties, which make it suitable for a wide range of applications. Some of the key physical properties of steel include:

1. High strength-to-weight ratio: Steel is incredibly strong for its weight, which makes it ideal for construction and transportation applications where strength and lightness are important.
2. Ductility and malleability: Steel can be bent, shaped, and formed without breaking, which allows it to be used in a variety of manufacturing processes.
3. Magnetism: Steel is magnetic, which makes it useful for electrical applications.
4. Conductivity: Steel is a good conductor of heat and electricity, although not as good as pure metals like copper.
5. Melting point: Steel has a high melting point, typically around 1,370°C (2,500°F), which makes it suitable for high-temperature applications.

In addition to its physical properties, steel also has important mechanical properties, including:

1. Tensile strength: This is the maximum stress that steel can withstand before breaking when being stretched or pulled.
2. Yield strength: This is the stress at which steel begins to deform plastically, meaning it won’t return to its original shape after the stress is removed.
3. Hardness: This is the ability of steel to resist indentation and scratching.
4. Toughness: This is the ability of steel to absorb energy and deform plastically before fracturing.
5. Elasticity: This is the ability of steel to return to its original shape after stress is removed, provided the stress hasn’t exceeded the yield strength.

The exact properties of steel can be adjusted by changing its composition and by heat treating. Increasing the carbon content of steel increases its strength and hardness but reduces its ductility. Other alloying elements can be added to enhance specific properties. For example, chromium is added to create stainless steel, which is resistant to rust and corrosion.

Heat treating, which involves heating and cooling steel in a controlled way, can also be used to modify its properties. For example, quenching (rapid cooling) can be used to harden steel, while tempering (reheating hardened steel) can be used to reduce brittleness and increase toughness.

Types of Steel and Their Uses

There are many different types of steel, each with its own unique properties and uses. The two main categories are carbon steels and alloy steels.

Carbon Steels: Carbon steels are steels that primarily contain carbon as the alloying element. They are further categorized based on their carbon content:

Property	Low-Carbon Steel	Medium-Carbon Steel	High-Carbon Steel
Carbon Content	0.05% – 0.25%	0.25% – 0.60%	0.60% – 1.50%
Tensile Strength (MPa)	200 – 300	300 – 600	600 – 2000
Yield Strength (MPa)	100 – 200	200 – 400	400 – 1000
Elongation (% in 50mm)	25 – 40	10 – 25	1 – 10
Hardness (Brinell)	80 – 200	200 – 300	300 – 600
Weldability	Excellent	Good	Poor
Machinability	Excellent	Good	Poor
Ductility	Excellent	Good	Poor
Common Uses	Structural shapes, sheets, wire products	Gears, shafts, rails, machinery parts	Springs, tools, dies, cutlery

1. Low-carbon steels (also known as mild steels) contain up to 0.3% carbon. They are ductile, machinable, and weldable, but not very hard. They are often used for car bodies, pipes, and structural shapes.
2. Medium-carbon steels contain between 0.3% and 0.6% carbon. They are harder and stronger than low-carbon steels but less ductile. They are often used for railway tracks, gears, and crankshafts.
3. High-carbon steels contain between 0.6% and 1.0% carbon. They are very hard and strong but less ductile than lower-carbon steels. They are often used for springs, wire, and cutting tools.
4. Ultra-high-carbon steels (also known as tool steels) contain between 1.0% and 2.0% carbon. They are extremely hard but very brittle. They are used for special purposes like drill bits, files, and dies.

Alloy Steels: Alloy steels are steels that contain significant amounts of alloying elements other than carbon, such as manganese, silicon, nickel, titanium, copper, chromium, and aluminum. Some common types of alloy steels include:

1. Stainless steels: These contain at least 10.5% chromium, which forms a protective oxide layer on the surface, making the steel resistant to corrosion and rust. They are used for kitchen utensils, medical equipment, and architectural facades.
2. Tool steels: These are alloyed with elements like tungsten, molybdenum, and cobalt to increase their hardness, toughness, and wear resistance. They are used for cutting tools, dies, and molds.
3. High-strength low-alloy (HSLA) steels: These contain small amounts of alloying elements to increase their strength and toughness while maintaining good formability and weldability. They are often used for construction equipment, trucks, and bridges.
4. Advanced high-strength steels (AHSS): These are a newer class of steels that offer extremely high strength-to-weight ratios. They are often used in automotive applications to reduce vehicle weight and improve fuel efficiency.

Steel is used in a wide variety of applications across many industries. Some of the most common uses include:

1. Construction: Steel is used for structural beams, reinforcing bars, roofing, and cladding in buildings and infrastructure.
2. Automotive: Steel is used for car bodies, chassis, engines, and many other automotive parts.
3. Appliances: Steel is used in the manufacture of refrigerators, washing machines, ovens, and other household appliances.
4. Tools and machinery: Steel is used to make hand tools, power tools, and many types of industrial machinery.
5. Aerospace and defense: High-performance steels are used in the construction of aircraft, spacecraft, and military vehicles and equipment.

Advantages of Steel

Steel is the material of choice for so many applications because of its unique combination of properties and advantages, including:

• Strength and durability: Steel is one of the strongest materials available, with a high strength-to-weight ratio. It can withstand high stress and heavy loads without breaking or deforming.
• Versatility and adaptability: Steel can be manufactured in a wide range of shapes and sizes, from thin sheets to thick plates, from small wires to large beams. It can also be welded, bolted, or riveted to form complex structures.
• Recyclability and sustainability: Steel is 100% recyclable and can be recycled endlessly without losing its properties. In fact, steel is the most recycled material in the world, with a recycling rate of over 60% globally.

Fact	Data
Global steel recycling rate	> 60%
Steel recycling vs. other materials	Steel is the most recycled material in the world
Energy saved by recycling steel	60-70% compared to virgin steel production
CO2 emissions reduced by recycling steel	58% compared to virgin steel production
Steel recycling process	100% recyclable without loss of quality

• Cost-effectiveness: While steel is not the cheapest material available, it offers excellent value for money due to its durability, versatility, and recyclability. The cost of steel has also remained relatively stable over time compared to other materials.
• Aesthetics and design flexibility: Steel can be finished in a variety of ways, from shiny to matte, from painted to powder-coated. It can also be shaped into almost any form, allowing architects and designers great freedom in creating aesthetically pleasing structures.Challenges and Innovations in the Steel Industry

Despite its many advantages, the steel industry faces several challenges, particularly in terms of its environmental impact. Steel production is energy-intensive and is responsible for significant carbon dioxide emissions, contributing to climate change.

In response to these challenges, the steel industry is actively working to reduce its environmental footprint. Some of the efforts include:

1. Reducing carbon emissions: Steel companies are investing in new technologies to reduce their carbon emissions, such as carbon capture and storage, hydrogen-based steelmaking, and the use of renewable energy in steel production.
2. Recycling and circular economy: The steel industry is promoting the use of recycled steel (scrap) in production, which reduces the need for virgin raw materials and saves energy. The industry is also working towards a circular economy model, where steel products are designed for reuse and recycling at the end of their life.
3. Emerging technologies: Researchers and companies are developing new technologies to make steel production cleaner and more efficient. For example, “green steel” is a term used to describe steel produced using renewable energy and low-carbon methods. 3D printing of steel is another emerging technology that could revolutionize the way steel products are designed and manufactured.

Despite these challenges, the outlook for the steel industry remains positive. Steel demand is expected to grow in the coming years, driven by population growth, urbanization, and the need for sustainable infrastructure. The industry’s ability to innovate and adapt to changing demands and regulations will be key to its long-term success.

FAQs About Steel

• What’s the difference between steel and iron? Steel is an alloy of iron and carbon, while iron is a pure metal. Steel contains between 0.2% and 2.1% carbon, which gives it greater strength and hardness than pure iron.

Property	Iron	Steel
Composition	Pure metal	Iron alloy with 0.2% – 2.1% carbon
Strength	Low	High
Ductility	High	Varies based on carbon content
Magnetism	Magnetic	Magnetic
Melting Point	1538°C (2800°F)	1370°C – 1540°C (2500°F – 2800°F)
Corrosion Resistance	Low	Varies based on alloy composition
Common Uses	Cast iron products, pure iron is rare	Construction, automotive, machinery, tools

• How much steel is recycled each year? Globally, over 600 million metric tons of steel are recycled each year, more than all other materials combined.
• What are some common steel alloys? Some common steel alloys include stainless steel (contains chromium), tool steel (contains tungsten, molybdenum, or cobalt), and high-strength low-alloy (HSLA) steel (contains small amounts of various alloying elements).
• How has steelmaking evolved over time? Steelmaking has evolved from ancient methods like bloomeries to the Bessemer process in the 19th century, and to modern methods like basic oxygen furnaces and electric arc furnaces.
• What innovations are shaping the future of steel? Some innovations shaping the future of steel include “green steel” produced using renewable energy and low-carbon methods, 3D printing of steel products, and advanced high-strength steels (AHSS) for lightweight, fuel-efficient vehicles.

Fun Facts About Steel

1. Steel is the world’s most recycled material. More steel is recycled each year than all other materials combined, including aluminum, glass, and paper.
2. The Eiffel Tower is made of puddle iron, a type of wrought iron. It was constructed in 1889 and was the tallest structure in the world until 1930.
3. Steel is 1000 times stronger than iron in its purest form. This is due to the addition of carbon and other alloying elements that enhance its strength and other properties.
4. The world’s first skyscraper, the Home Insurance Building in Chicago, was supported by a steel skeleton. Built in 1885, it was 10 stories tall and marked the beginning of the era of the skyscraper.
5. Stainless steel can be recycled endlessly without degradation. This makes it one of the most sustainable materials available.

Conclusion

In this post, we’ve taken a deep dive into the world of steel. We’ve learned what steel is, how it’s made, its properties, types, uses, and more. We’ve seen how steel has played a crucial role in shaping our modern world, from the buildings we live and work in to the vehicles we use to get around.

Steel’s importance is not just a matter of history, but also of our present and future. As we face challenges like climate change and resource scarcity, steel’s strength, durability, and recyclability make it an essential material for building a sustainable future.

So the next time you see a steel structure or use a steel product, take a moment to appreciate the remarkable properties and versatility of this metal alloy. Steel truly is the backbone of our modern world.

This article presented steel, explained what it is, and discussed its various types and applications. To learn more about steel, contact a UTM representative.

UTM provides a wide range of steel products and services for all your needs. Visit our website to learn more or to request a free, no-obligation quote.