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The steel of <a href="http://www.junguansteel.com/steel-plate/" target="_self">Steel
Plate</a> comes in many grades, specifications, shapes, and finishes - the World Steel
Association lists over 3,500 different grades of steel, each with unique properties. The
various types mean that steel can by widely used in infrastructure, appliances,
vehicles, wind turbines, and many more applications.
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Optimizing steel's properties for each application goes beyond changing the
chemical composition, however. The manufacturing processing of steel can also have a
significant impact on steel products - even when the grades and specifications are the
same. One key distinction among pre-fabricated steel products is the difference between
hot rolled and cold rolled steel.
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It's important to note that the main difference between hot rolled and cold
rolled steel is one of process. "Hot rolling" refers to processing done with
heat. "Cold rolling" refers to processes done at or near room temperature.
Although these techniques affect overall performance and application, they should not be
confused with formal specifications and grades of steel, which relate to metallurgical
composition and performance ratings. Steels of different grades and specifications can
be either hot rolled or cold rolled - including both basic carbon steels and other alloy
steels.
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It may seem obvious, but some types of steel are better suited for certain
applications. Knowing which to use can help avoid over-spending on raw materials. It can
also save time and money on additional processing. Understanding the differences between
hot and cold steel is integral to choosing one over the other.
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<a href="http://www.junguansteel.com/hot-rolled-steel/" target="_self">Hot rolled
steel</a> including <a href="http://www.junguansteel.com/hot-rolled-steel/hot-rolled-
steel-plate/" target="_self">Hot Rolled Steel Plate</a> and<a
href="http://www.junguansteel.com/hot-rolled-steel/hot-rolled-steel-coil/"
target="_self"> Hot Rolled Steel Coil</a> is steel that has been roll-pressed at very
high temperatures - over 1,700?F, which is above the re-crystallization temperature for
most steels. This makes the steel easier to form, and resulting in products that are
easier to work with.
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To process hot rolled steel, manufacturers first start with a large, rectangular
length of metal, called a billet. The billet is heated and then sent for pre-processing,
where it is flattened into a large roll. From there, it is kept at a high temperature
and run through a series of rollers to achieve its finished dimensions. The white-hot
strands of steel are pushed through the rollers at high speeds. For sheet metal, rolled
steel is spun into coils and left to cool. For other forms, such as bars or plates,
materials are sectioned and packaged.
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Steel shrinks slightly as it cools. Since hot rolled steel is cooled after
processing, there is less control over its final shape, making it less suitable for
precision applications. Hot rolled steel is often used in applications where minutely
specific dimensions aren't crucial. Railroad tracks and construction projects often
use hot rolled steel.
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Hot rolled steel can often be identified by the following characteristics:
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A scaled surface - a remnant of cooling from extreme temperatures
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Slightly rounded edges and corners for bar and plate products (due to shrinkage and
less precise finishing)
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Slight distortions, where cooling may result in slightly trapezoidal forms, as
opposed to perfectly squared angles
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<a href="http://www.junguansteel.com/cold-rolled-steel/" target="_self">Cold rolled
steel</a> including <a href="http://www.junguansteel.com/cold-rolled-steel/cold-
rolling-steel-sheets/" target="_self">Cold Rolling Steel Sheets</a> is essentially hot
rolled steel that has been through further processing. Once hot rolled steel has cooled,
it is then re-rolled at room temperature to achieve more exact dimensions and better
surface qualities.
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Cold "rolled" steel is often used to describe a range of finishing
processes, though technically "cold rolled" applies only to sheets that
undergo compression between rollers. Steel forms that are pulled, such as bars or tubes,
are "drawn", not rolled. Other cold finishing processes include turning,
grinding, and polishing - each of which is used to modify existing hot rolled stock into
more refined products.
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Cold rolled steel can often be identified by the following characteristics:
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Better, more finished surfaces with closer tolerances
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Smooth surfaces that are often oily to the touch
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Bars are true and square, and often have well-defined edges and corners
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Tubes have better concentric uniformity and straightness
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There are other kinds of steel made with different technology like Hot Dip
Galvanized Steel including <a href="http://www.junguansteel.com/cold-rolled-steel/hot-
dip-galvanized-steel-sheet/" target="_self">Hot Dip Galvanized Steel Sheet</a> and<a
href="http://www.junguansteel.com/cold-rolled-steel/hot-dip-galvanized-steel-coil/"
target="_self"> Hot Dip Galvanized Steel Coil</a>, and other <a
href="http://www.junguansteel.com/steel-application/" target="_self">Steel
Application</a> like <a href="http://www.junguansteel.com/steel-application/railway-
steel/" target="_self">Railway Steel</a>.
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