Steel Production Process
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ScribdTranslationsSteel Production Process
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ScribdTranslationsSTEEL MANUFACTURING PROCESS
OBTAINING STEELS
How steel is produced.
Steel is primarily produced by the transformation of molten iron into
cast iron form. The task of transforming cast iron into steel is reduced
to the extraction of the remaining amounts of carbon, silicon, manganese, and
the harmful impurities it contains. This task can be carried out because
carbon and other impurities, under the action of high temperatures, combine
with oxygen in a more energetic way than iron and can be extracted with
insignificant losses of iron. The carbon from the pig iron when reacting with the
oxygen is transformed into carbon monoxide (CO) that volatilizes.
Other impurities are transformed into oxides (SiO2, MnO, and P2O5) that have
a density lower than that of molten metal and therefore they float forming the
scum.
Two general methods are used to transform pig iron into steel:
The method of converters.
The use of special ovens.
The converters
The essence of the converter method for steel production
consists of the liquid molten iron charged to the converter,
injects air, which bubbles inside the molten mass and whose oxygen oxidizes the
carbon and other impurities.
The converter (Fig 1) represents a pear-shaped vessel, welded with
thick steel plates and internally coated with refractory material. In
the central part of the converter, externally there are two cylindrical pins
stumps that serve as supports and allow the converter to rotate. One
The stump is hollow and connects with the air duct. From the stump the
air is conducted through a tube and through the air box to the bottom. At the bottom of
the converter are the nozzles through which air is supplied to the
pressure converter. It is also used for oxygen insufflation with which the
the process becomes faster and more efficient.
To load the converter, it is turned from the vertical position to the
horizontal, the molten pig iron is added and the converter is returned to its
vertical position, at that moment the blowing starts. The volume
the incorporated metal constitutes from 1/5 to 1/3 of the volume of the height of the
cylindrical part.
The heat necessary to raise the steel to high temperatures
necessary occurs at the expense of the oxidation of the impurities of the
arrabio, since all oxidation reactions generate heat.
Depending on the composition of the pig iron, the converters are divided into
two types:
Acid-lined converter: (Bessemer process) used for
the raw materials with a minimum amount of phosphorus (0.07%) and sulfur (0.06%).
Basic-coated converter: (Thomas process) used for
the ores with the highest abundance of phosphorus (up to 2.5%).
The production of steel in an electric furnace is based on the melting of scrap metal.
through an electric current, and the subsequent refining of the molten bath.
The electric oven consists of a large cylindrical container made of thick metal plate.
30 mm thick) lined with refractory material that forms the base and
houses the liquid steel and slag. The rest of the furnace is made up of
water-cooled panels. The vault is movable to allow loading
from the scrap through suitable baskets.
The vault is equipped with a series of openings through which the
electrodes, generally three, which are thick graphite rods of up to 700
mm in diameter. The electrodes move in such a way that they can be adjusted.
its distance to the load as it gets consumed.
The electrodes are connected to a transformer that provides a
appropriate voltage and current conditions to ignite the arc, with
variable intensity, depending on the operating phase of the furnace.
Another hole made in the vault allows for the capture of gases from
combustion, which are properly purified to avoid contaminating the
atmosphere. The oven is mounted on an oscillating structure that allows it
to basculate in order to proceed with the bleeding of the slag and the emptying of the bath.
The manufacturing process is basically divided into two phases: the melting phase
and the refining phase.
Fusion phase
Once the scrap is introduced into the furnace along with the reactive agents and
fluxes (mainly lime) move the vault until it closes the furnace
and the electrodes are lowered to the appropriate distance, creating the arc
until the loaded materials are completely melted. The process is repeated until
complete the capacity of the furnace, with this steel constituting a cast.
Refining phase
The refining takes place in two stages. The first in the furnace itself and the
second in an oven spoon. In the first refining, the composition of the
molten bath and the removal of impurities and elements is carried out
undesirables (silicon, manganese, phosphorus, etc.) and make an initial adjustment of the
chemical composition through the addition of ferroalloys that contain
the necessary elements (chromium, nickel, molybdenum, vanadium or titanium).
The obtained steel is poured into a ladle, lined with material
refractory, which serves as the vessel of a second refining furnace in the
that finishes adjusting the composition of the steel and giving it the temperature
suitable for the next phase in the manufacturing process.
Snack:
Once the steel itself has been obtained, it is necessary to bring it to a state
solid through its pouring or casting. Usually, two types are distinguished
of the colada
Casting into ingots: It is the conventional procedure. By means of
a spoon is pouring molten steel into molds, which once
Cooled down, they turn into manageable ingots to continue with the rest of the processes.
Continuous casting: The most commonly used method today,
procedure by which bars, profiles or sheets are produced
that solidify as the liquid metal is poured into a
endless trough, that feeds indefinitely. In the following animation
you can see the process Below I leave you another infographic, prepared by
Ternium Argentina, which can help you understand how the oven works
high.
Rolling
The billets are not usable directly and must be transformed into
commercial products through rolling or hot forging.
In simple terms, we could describe rolling as a process in which
the semi-product (bar) is passed between two rollers or cylinders, which
they spin at the same speed and in opposite directions, reducing their section
transversal thanks to the pressure exerted by them. In this process it
it takes advantage of the ductility of steel, that is, its ability to deform, both
the higher its temperature. Hence, hot rolling
is carried out at temperatures between 1,250ºC, at the beginning of the process, and
800°C at the end of it.
The rolling process only allows obtaining products of constant section, such as the
case of the corrugated bars.
The process begins by increasing the temperature of the billets by
reheating furnaces up to an optimal value to be introduced in the
rolling mill
Generally, these ovens are gas-powered and they are distinguished by three zones:
preheating, heating, and homogenization. The step of the
carrying beams from one area to another is done using different devices of
advance. The atmosphere inside the furnace is oxidizing, in order to reduce
to the maximum the formation of husk.
Once the desired temperature is reached throughout the mass of the billet, it is
guided through a roller path to the rolling mill. This
the train is formed by pairs of cylinders that reduce the section of the
palanquilla. First from square shape to oval shape, and then from
oval shape to round shape. As the section decreases, it increases.
the length of the transformed product and, therefore, the rolling speed.
The train is controlled automatically, in such a way that the speed of the
different boxes that compose it are increasing at the same rate in the
that the section was reduced in the previous one.
The rolling mill is divided into three parts:
Roughing train: where the billet undergoes a very light first pass
to break and eliminate the possible layer of husk formed during its
staying in the oven.
Intermediate train: made up of different boxes in which it is formed
through successive passes the section.
Finishing line: where the product undergoes its last pass and obtains its
geometry of corrugated
The already rolled bars are deposited on a large plate or bed of
cooling. From there, they are transferred to the custom cutting lines and
packaged and then move to the storage area and
expedition.
In the case of roll lamination, they come out of the finishing train in the form
from the coil, being transported by a cooling belt, from which the
spools are being deposited on a spindle, where they are compacted and tied to
its expedition, or is taken to a staging area, where they are formed
spools on a reel.
During the rolling process, the different parameters that will determine are controlled.
quality of the final product: the initial temperature of the billets, the degree of
deformation of each pass —to prevent excessive deformation from giving
place to breaks or cracks in the material—as well as the degree of reduction
final, which defines the degree of forging, and especially the cooling system
controlled.
conclusions
The process of obtaining steel allows us to see the complexity of the work.
What is required for a production to be well executed.
The steel production process is not isolated; in the factories there are
casting and rolling processes.
RECOMMENDATIONS
It is necessary to study these processes more in depth, in order to obtain a
greater amount of information that can help us understand
completely the acquisition.
When studying these processes, we must take into account each one of the
production details, such as costs, how the material is obtained,
impacts, etc.
BIBLIOGRAPHY:
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