How Steel is Made, Step by Step

Steel is an integral part of our daily lives, whether you realize it or not. From the sturdy Frame of your car to the sharp edge of the kitchen knife you use to chop vegetables, steel is everywhere. Without it, the world as we know it would be drastically different. However, despite its omnipresence, few people truly understand how steel is made. Fortunately, the experts at Clickmetal are here to demystify the entire process for you. In the following guide, we’ll walk you through each step of steel production, from raw materials to the final product.

Before We Begin…

Steelmaking is a complex process that varies depending on the type of steel and the method employed. While this guide focuses on basic oxygen steelmaking (BOS), which is the most common technique, keep in mind that some steel is refined using electric arc furnaces or other processes. Now, let’s dive into the standard procedure.

1. Extracting Raw Materials

The journey of steel starts with sourcing its primary components: iron ore, coal, and limestone.

• Iron Ore: This is the main source of iron, the key ingredient in steel. Hematite and magnetite are the most widely used types of iron ore.
• Coking Coal: Coking coal is used to generate the intense heat required to transform iron ore into a usable form.
• Limestone: Limestone acts as a flux, helping to eliminate impurities such as silica, sulfur, and phosphorus during the smelting process.

Additional alloying elements, like nickel or magnesium, may also be collected for later stages of refinement. These raw materials are typically extracted from large deposits and transported to steel mills, where the transformation into steel begins.

2. Converting Coal to Coke

The next step involves converting coal into coke. This process occurs in a coke oven, where coal is heated in an oxygen-deprived environment to remove volatile substances. The result is coke, a carbon-rich fuel that burns hotter and cleaner than regular coal. Coke is vital because it provides the immense heat needed in the blast furnace to melt the iron ore.

3. The Blast Furnace

With the coke prepared, the next phase takes place in the massive blast furnace, which can tower between 100 and 200 feet. Here's how the process unfolds:

• Iron ore, coke, and limestone are layered within the furnace, which is lined with heat-resistant bricks.
• Superheated air, reaching temperatures of 1,500–2,200°C, is blasted into the furnace from the bottom. This extreme heat ignites the coke, producing carbon monoxide gas. This gas reacts with the iron ore, reducing it into molten iron.
• As the iron ore melts, impurities like silica form a liquid slag that floats atop the molten iron. The purified iron, now in liquid form, sinks to the bottom of the furnace and is collected.

This molten iron, known as pig iron, still contains a high concentration of carbon and impurities, making it brittle. It must undergo further processing to become steel.

Fun Fact: Pig iron earned its name due to the way molds were arranged during casting. The molds were shaped like a sow with piglets, with the larger mold receiving the molten iron and the smaller ones forming the "piglets."

4. Basic Oxygen Steelmaking (BOS)

The pig iron from the blast furnace is sent to a basic oxygen furnace for refining. This step reduces the carbon content and purifies the iron, transforming it into steel.

• Molten pig iron is poured into the furnace, followed by a high-pressure stream of pure oxygen. The oxygen reacts with the carbon in the pig iron, creating carbon dioxide and lowering the carbon content.
• Fluxes like limestone are added to remove impurities. The reaction between oxygen, fluxes, and impurities forms slag, which is subsequently removed.
• The amount of oxygen introduced and the timing of the process are meticulously controlled to achieve the desired carbon level for the specific steel type being produced (e.g., 0.3% for mild steel) while maintaining the steel's other essential qualities.
• At this stage, alloying elements such as manganese, chromium, or nickel can be added to impart specific properties like enhanced strength or corrosion resistance. This creates various types of steel, with stainless steel being among the most famous.

The outcome is high-grade liquid steel with significantly reduced carbon compared to the initial pig iron.

5. Casting

Once refined, the molten steel is prepared for casting. It is poured into molds to form slabs, billets, or blooms, depending on the intended application.

Most modern steel plants utilize continuous casting. In this method, molten steel is continuously poured into a water-cooled mold, where it solidifies as it descends. This produces long steel strands that are cut to the required lengths. Although ingot casting is still practiced in some instances, it is less common today.

6. Shaping and Forming

After solidifying, the steel undergoes further shaping to achieve the final product. This is usually done via hot or cold rolling:

• Hot Rolling: The steel is heated above its recrystallization temperature and passed through large rollers to achieve the desired thickness. This technique is used for products like steel sheets, beams, and rails.
• Cold Rolling: For certain applications, the steel is rolled at room temperature. This results in a smoother surface and more precise dimensions, making it ideal for products requiring a high-quality finish.

7. Finishing Treatments

The final stage of steel production involves a series of finishing treatments to prepare the material for construction, manufacturing, and other industries. These processes include:

• Acid immersion, known as pickling, to eliminate surface impurities such as rust or scale.
• Galvanization, which involves coating the steel with zinc to prevent rusting.
• Heat treatment to enhance strength, ductility, or toughness.
• Application of protective coatings or colorful paint finishes.
• Trimming to meet specific specifications.

8. Quality Control and Testing

Before steel products are dispatched, they undergo rigorous quality control checks to ensure compliance with mechanical properties, chemical composition, and dimensional tolerances. Common tests include:

• Tensile testing to evaluate the steel's strength.
• Hardness testing to assess resistance to indentation.
• Ultrasonic testing to identify internal flaws or cracks.

Once the steel passes these evaluations and meets the standards, it's ready to be utilized in a vast array of items—from tools and machinery to vehicle frames, furniture, medical equipment, and virtually everything else you can imagine!

Choose Clickmetal for Premium Steel and Aluminum

As a leading supplier of steel and aluminum in the UK, we at Clickmetal are committed to the role quality metal plays in constructing the world around us, from small DIY projects to large-scale developments. That’s why we source our metals exclusively from trusted suppliers and subject all custom-cut pieces to thorough quality control to uphold the highest standards. If you’re searching for premium-quality metal for your project, you can count on us to deliver precisely what you need—quickly and at some of the best prices in the UK. Browse our complete range here!