The Steel Making Process

8/8/2019 The Steel Making Process

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Where Does the Steel We Use

Everyday Come From?

Jon Takosky

10/19/2010


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Audience and ScopeThe purpose of this article is to inform interested college students and other interested people

about the steel making industry. Although people use steel every day, few really know all thestages involved in the steel making process. This article will provide an inside look at the process

of making steel. Some of the steps are very technical and in-depth, so this paper will aim to give

the reader an overview of the entire process while touching on the technical steps. This paperwill allow a reader who has little or no experience about the steel industry to understand wheresteel comes from.

IntroductionPeople have been using steel for centuries. Today people

use steel in just about every aspect of their lives, but fewpeople fully understand the steel making process. Over

the years, the steel making process has evolveddrastically from the early technique first used to the

automated, large-scale processes used today. These

processes used today involve many steps, machines, andtechniques. The steel industry today also includes manydifferent, grades, and types of steel. One of the main

steel making processes is the production of carbon basedsteel-sheet coils. The making of many of the other

different grades of steel involves the same process, onlydifferent materials are used. This process takes scrap

metal and other materials and turns them into a coil ofsheet-steel weighing an average of two tons.

Process

The making of the steel sheet rolls begins the same way that most large scale metal makingprocesses start. The first step is to melt down the scrap metal and other materials down in ladles.The process of melting down the materials can be done using different techniques. The two main

techniques that are used in the steel factories today are the use of an electric arc furnace and theuse of an oxygen lance.

Melting ProcessesThe two main melting processes used in the steel industry today are an electric arc furnace and

an oxygen lance. The final product of each melting process is the same, but the size of the plantand the products it produces decide which process to use. An electric arc furnace is better for

larger more diverse companies, while an oxygen lance is used in more small-scale production

where the same product is produced.

Figure 1. A 2 ton coil of sheet steel


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Electric Arc Furnacey Consists of three main parts

o Shell- the sidewalls and the lower bowl ofthe furnace.

o Hearth- the refractory that lines the shell.o Roof- the cover of the furnace that is oftenremovable for operational purposes.

y The roof of the furnace is removed and the scrapmetal is loaded into the furnace.

y The furnace then begins to preheat, or charge, thescrap metal.

y The graphite electrodes then enter the furnace.y The electrodes then create an arc with the scrap metal.y The arc, combined with pumped in oxygen, then melts the contents of the ladle.y The chemical makeup of the metal is then tested, and material is added to reach the desired

chemical qualities.

Oxygen Lancey Scrap metal is taken to a blast furnace where it is preheated.y The preheated metal is then placed in a ladle.y A water-cooled oxygen lance is then lowered into the ladle.y The lance blows 99% oxygen into the metal, igniting the

carbon in the steel, which not only melts the metal, but alsoburns off impurities in the mixture.

y The lance continues to heat the metal until a temperature ofaround 1700C is reached.

y Chemical readings of the metal are taken and differentmaterials are added to create the desired chemical makeup.

After the metal is melted and the proper chemical measurements are

taken the furnace is emptied. The shells are tapped and the moltenmetal is emptied out of the ladles. The molten metal is then casted

into ingots. An ingot is basically a roughly shaped block of steel.The ingot is formed, creating an easy way to transport the steel.

Figure 2. Electric Arc Furnace

Figure 3. Oxygen Lance

Figure 4. Casted Steel Ingot.


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Creating a SlabThe casted ingots are now ready to be made into steel slabs.

Before the ingots can be made into slabs they head to thesoaking pits, an area where the ingots are heated up to the

desired temperature. The ingots need to be heated up so the

metal can be shaped into a slab. The ingots are then sentthrough the blooming mill. The blooming mill is a heavy dutyhydraulically controlled rolling machine that is used to form

the ingots in to rectangle slabs. The steel takes multiple passesthrough the blooming mill, after each pass the machine presses

the sides, creating flat uniform sides. After the desiredthickness is reached mill also uses a hydraulic press to shear

off the uneven ends of the red-hot slab.

The slabs of the metal are then transported by crane and train to the storage area. While the slabsare in this storage area the surfaces are often grinded, creating a uniform surface. The uniform

surface helps ensure the surface quality during the rolling process. The grinding is often doneusing two different methods. The first method implements a moving grinder wheel and thesecond implements a stationary grinding wheel that the slab moves under. Due to space

restrictions smaller steel mills often use the moving grinding wheels, while larger mills oftenimplement both techniques.

Hot-Strip MillWith the grinding complete the slabs move onto the hot strip mill. Cranes transport the slabs

to the hot strip mills pre heat furnace. In orderfor the slabs to be rolled down, the slabs have

to be heated to around 1000C. With the slabspreheated, the slabs begins passing through the

hot strip mill. The average hot strip mill hasmultiple rollers. Not only are there multiple

rollers, each roller is usually backed up,meaning there are multiple rollers stacked on

top of each other to increase the rolling force,producing a higher quality product. Each slabstarts off by passing back and forth under the

first roller; each time the thickness is decreased and the length is increased.

After the slabs thickness has been decreased the steel is sent through an average of six to sevenmore rollers. This time though the steel only makes a single pass under each roller. Each roller

once again decreases the thickness and increases the length. As the slab, which now is a long thinsheet of metal, exits the rolling mill it has an increased velocity due to the expansion in length.

At the end of the line the sheet hits the coiler, which guides the incoming sheet. The coilercombined with the increase in velocity causes the sheet to roll up into a coil. After the sheet is

rolled up, the coil is banned and the sent to storage where it waits to be shipped and finished.

Figure 5. A steel slab exiting theblooming mill.

Figure 6. Hot strip mill showing backup rollers and apiece of steel passing through the rollers.


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ConclusionPeople use steel in just about every aspect of their everyday lives. People sometimes take the

steel for granted and put little thought into where it comes from. The process of making steel is avery technological and work intensive process. The process involves not only mechanical

machines, but also chemical formulations and computer automations. Although the process

simply starts with scrap melts and ends with a simple coil of steel, the processes in between arevery intense. The steel making process involves many steps and stages, which have evolved overtime. As time goes on people will continue to use steel, and the steel making process will

continue to be one of the worlds most important processes.


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The Steel Making Process