Your Every Day Metal: How It's Made
If you look around, you will see a lot of steel. Next to plastic and paper, it’s one of the most common materials in products used every day. From your car to your kitchen stove to the door locks, steel is everywhere. In fact, to really put into perspective how essential steel is to our modern world, think about this - it takes steel to make steel.
So how does this everyday metal come to be, i.e., how is steel made? There’s not just one answer, as it depends on a couple of factors - like what it’s made with and how. Although you probably aren’t as into steel as we are, you are reading this for a reason. Curiosity? Education? Research? Whatever it may be, we’re going to educate you on how iron is made into steel that surrounds us.
When you’re finished, you will know more than you probably ever wanted to about steel and have the power to confidently answer when anyone asks, “How is steel made?”
How Is Steel Made - Modern Processes
Before we get into today’s steel-making processes, let’s review a little history. The earliest indication of steel use dates back to 1400 B.C. and has since unarguably become a staple in the world’s industrial economy. However, steel use did not really flourish commercially until the 1850s when Sir Henry Bessemer, an English inventor, invented a steel-making process that would make mass steel production affordable. Before his discovery, steel production was costly and reserved for small and expensive items, such as knives, swords, and armor.
Today, steel is an instrumental building material with countless applications. The modern steelmaking processes have come a long way and fall into two categories: primary and secondary steelmaking.
Primary steelmaking involves a blower to force oxygen through molten iron, which lowers its carbon content while subsequently converting it into steel. There are three methods of primary steelmaking in use today.
Basic Oxygen Furnace Steelmaking
Basic oxygen steelmaking has many pseudonyms - BOS, BOP, BOF, OSM, the Linz–Donawitz-steelmaking, or the oxygen converter process. In all cases, basic oxygen furnace steelmaking is a method of primary steelmaking that blows oxygen through molten iron ore or coal to lower the carbon content of the alloy and change it into low-carbon steel.
The process was developed in 1948 by Robert Durrer, who refined Bessemer steel production by replacing air with oxygen. Blowing oxygen instead of air reduced the capital cost of the process and the smelting time, which increased labor productivity. This method became responsible for most of the steel manufactured globally, accounting for 70% of global steel output in 2011.
Electric Arc Furnace Steelmaking
How is steel made in an electric arc furnace (or EAF)? A more modern process, EAF steelmaking uses scrap or direct reduced iron rather than ore or coal. The scrap material is heated in a furnace with a prolonged electrical charge. Although it has been around since the 1900s, this type of steelmaking has gained popularity as a reduced carbon or “greener” process than BOF steelmaking - here’s why:
- EAF can make steel from a 100% scrap metal feedstock, which reduces the energy required to make steel (compared with primary steelmaking from ores).
- EAF steelmaking is more flexible than blast furnaces because they can be rapidly started and stopped for on-demand production.
- EAFs require large amounts of electrical power, and many companies schedule their operations to take advantage of off-peak electricity pricing.
- A typical steelmaking arc furnace is the source of steel for a mini-mill, which can be sited relatively near steel product markets, thereby reducing transport requirements.
As restrictions to limit the carbon footprints in production increase, more and more steelmakers will likely continue to turn to EAF steelmaking.
Open-hearth Furnace Steelmaking
Open-hearth furnace steelmaking is another type of production that burns excess carbon and other impurities out of iron ore to produce steel. Its main advantages at the height of its use were that it did not expose the steel to excessive nitrogen, which caused the steel to become brittle. Open hearth furnace steelmaking was also easier to control and permitted the melting and refining of large amounts of scrap iron and steel.
However, more modern processes have primarily replaced this type of steelmaking. Although it is still in use in India and some parts of Ukraine, Russia retired its last hearth furnace in March 2018 and considered preserving it as a museum artifact.
Secondary steelmaking involves refining the crude steel before casting, and the various operations are typically carried out in ladles. During this process, several things happen to ensure high-quality steel is produced, i.e., alloying agents are added, dissolved gases in the steel are lowered, and inclusions are removed or altered chemically.
HIsarna steelmaking is one of four processes developed within the ULCOS project, a European cooperative launched to conduct research and development centered on enabling CO2 reductions within the steel industry.
Hlsarna steelmaking is based around a type of blast furnace called a cyclone converter furnace, making it possible to skip manufacturing the iron ore pellets needed with the basic oxygen steelmaking process. Without it, the HIsarna process is more energy-efficient and has a lower carbon footprint than traditional steelmaking processes.
The Making of Specific Steel Types
How Is Damascus Steel Made
Damascus steel is highly recognizable for its wavy pattern, and it is very sharp and tough. Originally, Damascus steel was the forged steel of the blades of swords smithed in the Near East from ingots of Wootz steel either imported from Southern India or made in Sri Lanka or Khorasan.
Although the original Damascus steel forging treatment was lost centuries ago, many attempts are still being made to replicate Damascus steel - mainly for its aesthetic. There are various methods for making Damascus steel today. In most cases, “Modern Damascus" steel is made from different steel and iron slices welded together to form a billet (a semi-finished product). The billet is then drawn out and folded until the desired number of layers are formed.
How Is Stainless Steel Made
Stainless steel is an alloy of iron and several other elements (such as nickel, chromium, molybdenum, and carbon) that is more resistant to corrosion than plain iron or steel (which is simply iron and carbon). The differing ratios of these stainless steel components produce different types of stainless steel alloys, and each unique combination is referred to as a “grade” of stainless steel.
So how is steel made stainless? Somewhat similar to other steelmaking, this process involves heating the raw materials and removing the excess carbon. Next, the material is stirred or “tuned” to help distribute or remove specific components from the mixture. Then the cooling metal is formed and heat-treated (also called annealed). The last step is cutting and shaping the stainless steel to create the final product.
Medical Grade Stainless Steel
Medical grade stainless steel is known for its high formability and exceptional corrosion resistance. There are two common medical grade stainless steels, which are grades 304 and 316. These steels are ideal for the medical industry thanks to the additional chemical properties provided by high levels of nickel, which helps withstand intense sterilization processes.
Cutlery Grade Stainless Steel
The addition of chromium makes stainless steel ideal for cutlery, as it helps to form a passive film that protects against corrosion and staining. Most cutlery is made with martensitic stainless steel, which is characterized by high strength and hardness.
How Hot Rolled Steel Is Made
Hot rolled steel is the most basic carbon steel product and is used in making products where the surface finish is not critical, like agriculture equipment or guard rails.
Hot roll steel is made by heating slabs of steel to approximately 2,300 degrees Fahrenheit. Upon transfer from the furnace and cooling, the material is then high-pressure washed to remove any mill scale formed when the hot material met the air. Finally, the material is treated with cooling sprays before entering coolers.
How Cold Rolled Steel Is Made
Cold rolled steel is made by melting down raw steel, also called smelting. After the raw steel has smelted down to a liquid, it’s then cooled slightly before being fed through a series of rollers. As the steel is forced through the rollers at a low temperature, it becomes both thinner and stronger as it’s compressed, which is essential to how hardened steel is made.
Because the compression occurs at a lower temperature with cold forming than hot forming, cold-formed steel is stronger and more durable - although more difficult to produce.
How Hardened Steel Is Made
Hardened steel is used for making tools and heavy machine parts. Compared to standard steel, the hardened type offers greater wear resistance and durability to withstand heavy-duty applications.
The production process begins with high carbon steel heated at very high temperatures, then rapidly cooled in water or brine in a process known as quenching, which makes the steel very hard, yet also highly brittle. To counter the brittleness and maintain the strength, manufacturers will temper the metal by reheating it once again and cooling naturally.
How Is Mild Steel Made
Mild steel is a very general type of steel, and it’s also called carbon steel. Mild steel is commonly used for road signs, fencing, cars, and nails (and much more).
Like other carbon steels, mild steel is made with iron and coal melted together in a blast furnace, then solidified into a rectangular shape. Next, it is hot rolled or cold drawn to the desired size.
How Structural Steel Is Made
Structural steel is an essential element in building and necessitates adhering to very specific standards in production. It begins with crushing and sorting raw iron using a refining process designed to sort out the best grades of iron, usually around 60 percent.
Next, the iron ore is loaded into the top of a blast furnace to heat. At the same time, hot air is blown in from the bottom. This creates a reaction that removes impurities as pure iron sinks to the bottom of the furnace. The molten iron is then drawn off and further heated, and other substances, such as manganese, are added that deliver different properties to the finished steel product.
Finally, it is formed into the configuration needed, such as beams, plates, or hollow steel tubes.
How Much Steel Is Made In America?
Steel is produced all around the world, including the U.S. From 2009 to 2014, annual iron and steel manufacturing in the United States increased from more than 70 billion dollars to 101 billion dollars in revenue. One of the largest steel producers in the U.S. is North Carolina-based Nucor Corporation, which ranked 20th in global steel production.
Now that you’re more informed about the various types of steel and the many production processes, you can understand how crucial it is to buy from reputable and knowledgeable suppliers.
At Texas Iron & Metal, we’ve been in the business of steel for over 80 years. Our comprehensive inventory includes a wide range of products, and our staff is available to answer any questions. Whether you're buying or selling steel and pipe, we are your go-to resource for reliable and personalized service.