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Steel production process: what are the steps?

Author: CC

Mar. 07, 2024

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Steel production process: what are the steps?

The steel industry is responsible for the production of steel. This material is an alloy of iron and carbon used worldwide. In general, the industry uses iron oxide or iron ore mixed with fine sand, and mineral coal or charcoal for steel production. This charcoal is used in the production process with two functions. The first one is as a fuel and the second as a reducer.

Steel began to be used after the Industrial Revolution. It was during this period that ovens were developed to correct and add properties to iron. These properties, which are characteristic of steel, include: wear resistance, impact resistance, corrosion resistance, among others.

Both iron and carbon are found abundantly in nature. Consequently, this makes the product to be done on a large scale and at a low cost.

In this sense, for steel to be produced, there are four stages in the production process. The first is the cargo preparation, proceeding to the reduction, refining, and finally the lamination step. Below you will understand each step in more detail.

Step 1: Cargo preparation

In the steel industry, the raw material for steel production is iron ore. And in the first stage of the production process for this material, iron ore is agglomerated using lime and coke fines.

At the end of this step, the resulting product is called sinter. The charcoal used is processed in the coke oven plant and transformed into coke.

The production of coke from coal used in steel production is called coking. The coal used in this process is called coking coal, an essential substance in reducing iron ore to liquid metal, as it combines with oxygen in the presence of limestone, creating carbon dioxide, iron, and slag.

Step 2: Reduction

At this stage of the production process, the raw materials are loaded into the blast furnace, which serves to separate the iron from its ore. For this, a chemical reduction reaction takes place.

What happens is that the production of heat melts the metallic charge and makes a new process gain space, which is the reduction of iron ore into a liquid metal called pig iron.

The coke is physically and chemically degraded and is blown from the bottom of the blast furnace. Separation takes place when the carbon from the coke comes in contact with oxygen from the iron one.

Pig iron is an alloy of iron and carbon, but it has a very high carbon content. This is an intermediate product, but one that some industries in the metallurgical sector consider as a final product, as they do not continue the production process until steel is obtained.

Step 3: Refining

After the reduction, the next step is to refine the pig iron. For this purpose, oxygen or electric steelworks are used, which transform liquid or solid pig iron and iron and steel scrap into liquid steel.

To obtain this result, part of the carbon that is contained in pig iron is removed along with other impurities. Then, the liquid steel is solidified in continuous casting equipment that produces semi-finished products, ingots, and blocks.

Step 4: Lamination

Finally, the steel rolling step is when there is mechanical shaping of steel sheets or strips. This process is actually a physical deformation that two or more cylinders cause from constant rotation.

The objective of this step is to provide a new profile for the steel, as well as to refine its microstructures. During the steel rolling step, there is a reduction in the thickness of the workpiece, as well as an increase in its length and width.

Rolled steel parts are found in people’s daily lives, as they are used in the automotive, road, railway, civil construction, and mining industries.

Products obtained from steel and their applications

Many people don’t even realize it, but steel is present in the most varied occasions in everyone’s life.

Because of the wide range of applications steel has, there are many shapes and types of steel products. This variety is due to the fact that for each application there are changes in composition and shape that are necessary.

Housewares

Steel has characteristics that benefit its domestic use, such as resistance to low and high temperatures, a surface that reduces the accumulation of residues, a chemical composition that does not allow the material to peel, has high durability and low maintenance requirements.

Due to all these characteristics, it is used in restaurants, industrial kitchens, hospitals, laboratories, businesses, and in the homes of families.

Transport

Still considering the characteristics listed above, steel is widely used in the transport sector. The material is present in cars, trucks, buses, trains, subways, ships, bicycles, and motorcycles.

It is a product that is capable of transporting people and cargo, connecting cities, and distributing inputs and wealth from one place to another.

Construction

When used in constructive systems, steel allows the architectural design to have more freedom, flexibility, and compatibility with other materials. In addition, there is a lighter load in the construction foundations, a guarantee of the quality of the work, and shorter execution time.

To top it off, steel can be used as part of the production process, or even as the main material in some applications.

Packaging and containers

Steel is also widely used as packaging in general industries. Its main uses as packaging are for the conservation and transport of food, chemical, agricultural products, paints, and cooking or industrial gases.

The characteristics of the material also prevent food contamination, thus ensuring food quality.

Energy

In the energy sector, steel is used in various industries, such as hydroelectric, thermoelectric, nuclear power plants, transmission towers, transformers, electrical cables, platforms, pipelines, oil prospecting and extraction equipment, as well as in drilling rigs, mats, and buckets of coal mines.

Agriculture

In agriculture, steel is used to make the sector more efficient. Land preparation, for example, is done with plows that have steel. At the time of harvesting the plantations, the reapers and harvesters also have steel. And finally, at the time of storage, silos and bulk carriers also use the material.

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Steel is easily one of the most popular construction and production alloys in the world. It is a versatile product that blends durability with cost effectiveness and flexibility to work with. India happens to be one of the top five producers of steel in the world. But while steel is a highly preferred production material, have you ever wondered how steel itself is produced?

Iron Making

The first step to making steel is to make the iron from which it will be made. This is usually done with the help of coal. Raw bits of iron ore, coke, and lime are put into something called a blast furnace. Here, they result in molten iron (which is also called “hot metal

Steelmaking

Steelmaking is of two types – primary, and secondary.

The primary steelmaking process either involves a BOS method (basic oxygen steelmaking) or EAF method (electric arc furnace). In BOS, recycled scrap steel is added into the molten iron. At a really high temperature, oxygen is blown into this mixture to reduce the overall carbon content. In EAF, however, the recycled steel scrap is put through high-power electric arcs (of temperatures as high as 1650 C) in order to fully melt it and convert it to high quality steel.

Secondary steelmaking puts together both these processes. This is mainly done to fine-tune the composition of the steel being produced. Elements are added in specific temperature and environmental controls to create the perfect composition. These controls can include stirring, ladle-furnace, ladle injections, degassing, and CAS-OB (Composition Adjustment by Sealed Argon Bubbling with Oxygen Blowing).

Steel Casting

The molten iron is now put into a cooling mold, which sets the shape to a certain degree. It also causes the formation of a thin, hard shell. This shell is separated by the use of guided rolls. The strands of the shell are malleable, and can be worked into the desired shape, length depending on what they will be used for. Examples include flat sheets, beams, wires, or thin strips.

Primary Steel Forming

This is the final shaping process, where hot rollers are used to fine tune the cast. The defects of casting are removed, and the steel is molded into the exact desired shape and surface finish. This is the stage at which the rough shape of the steel transforms into definitive ones – like, pipes, wire rods, bars, rails, and more.

Manufacturing and Finishing

The final step to steel production is the secondary forming technique, which gives the steel products their final shape and properties. This is done by:

  1. shaping (cold rolling methods)
  2. machining (eg: drilling)
  3. joining (by means of welding)
  4. coating – galvanising with zinc, or cold coating and electro coating
  5. heat treatment (usually tempering)
  6. surface treatment (carburising).

In today’s world, steelmaking is trying to produce alternate and more sustainable methods that allow for this process to continue with minimal damage to natural resources. While steel remains a powerful and durable alloy, its production is massively carbon based. Steel companies in India are trying to find alternate routes to this.

For instance, a process called Pulverized Coal Injection is sometimes used in the primary steelmaking process. In this case, coal is directly injected into the furnace instead of coke. The coal used can be of low carbon content, which also reduces the cost of production.

Another fact is that steel is completely, 100% recyclable. The BOF process uses 30% of recycled steel, while EAF uses up to 90-100%. This is a far more sustainable option instead of mining more iron ore as a fresh ingredient in the steelmaking process.

There is also an alternate steelmaking process called HIsarna ironmaking. In HIsarna, iron ore is processed immediately into hot metal. The blast furnace used is a cyclone converter furnace, which skips the making of iron pellets. This skipped step makes the entire process far more energy-efficient and lowers the carbon footprint of steel production.

Steelmaking remains crucial in the industrialized world, an unavoidable process from massive scale infrastructure to the smallest kitchen utensils. It is simply a matter of finding a process that can be sustainable in the future, and cause minimal environmental damage while doing so.

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