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Cold rolled sheet products have been available for many,
many years, and have been successfully used for a multitude of
applications. Today's cold rolled sheet products are much
improved over those used in the past. They offer better control of
thickness, shape, width, surface finish, and other special quality
features that compliment the emerging need for highly engineered
end use applications.
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Cold rolled sheet products are used in a wide variety of end
applications such as appliances - refrigerators, washers,
dryers, and other small appliances, automobiles - exposed as
well as unexposed parts, electric motors, and bathtubs. Cold rolled
sheet products are used in these and many other areas of
manufacturing. To meet the various end use requirements,
cold-rolled sheet products are metallurgically designed to provide
specific attributes such as high formability, deep drawability,
high strength, high dent resistance, good magnetic properties,
enamelability, and paintability. To assist the users of cold rolled sheet products, the steel producer needs to be aware of
the many specific attributes required for the intended
application. The following information is
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intended to provide users of cold rolled sheet products with
information to assist them in selecting and ordering the proper
product to meet their end application.
The first step in manufacturing U. S. Steel's Cold Rolled Sheet Products
involves cold reducing coils of hot-rolled, pickled product to a thinner
thickness. The cold reduction operation induces very high strains (work hardening) into the sheet; thus,
the sheet not only becomes
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thinner, but also
becomes much harder, less ductile, and very difficult to form.
However, after the cold-reduced product is annealed (heated to high
temperatures), it becomes very soft and formable. In fact, the
combination of cold reduction and annealing lead to a refinement of
the steel that provides very desirable and unique forming properties for subsequent use by the
customer.
The primary feature of cold reduction is to reduce the thickness
of hot-rolled coils into thinner thicknesses that are not generally
attainable in the hot rolled state. Clearly, controlling the
sheet thickness along the entire length of the coil is very
important to
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ensure that the product will perform consistently during the
processing by the end user. In addition, there are a number
of other product attributes that need to be controlled in the cold
reduction process. Flatness (deviation from a
flat plane) is one of the more important attributes. Very sophisticated strip-shape
controlling technology is used to maintain good flatness. Surface
finish is another product attribute that needs to be controlled
during the cold-reduction process.
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As one can see, there is much more to cold rolling than simply reducing the
thickness to meet a customer’s ordered thickness. In fact, the hot-rolled,
pickled coils incoming to
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the cold reduction mill have to have excellent quality
attributes. The pickling operation must be well-controlled to
assure that all the oxides formed during hot rolling are removed.
The thickness of the hot-rolled strip is important in that the
properties of the final cold rolled and annealed product is
influenced by the percent cold reduction. This means that the
thickness of each hot-rolled coil is carefully controlled to
provide the mill with
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a specific thickness to
achieve the proper percent cold reduction. Among other
things, percent cold reduction affects the forming behavior of the
product after annealing.
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The production of a specific thickness of cold rolled sheet to meet an end
user’s requirements involves very sophisticated processing from the melt stage
forward. Steel chemistry, hot strip mill processing variables, pickling
practices, cold-rolling mill practices, annealing practices, and finally, temper
rolling practices all have a role in achieving the manufacture of top quality
cold-rolled sheet products.
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U.S. Steel produces the following cold rolled sheet
products.
- Cold Rolled
Sheet Steel
– This product is manufactured
for a large number of applications that require a variety of properties from
fairly simple to very sophisticated. The product is typically available at
thicknesses as low as 0.0142 inch although lighter gauges may be
ordered. Thicknesses lighter than this are generally ordered as Black
Plate. Specific ordering practices allow the user to specify the
following:
- Sheet
dimensions
- Dimensional tolerances with respect to thickness,
flatness, width, etc.
- Surface
finish (Brushed Bright to Matte to Embossed)
- The
metallurgical designation, i.e., Commercial Steel, Drawing Steel,
Bake Hardenable Steel, Structural Steel, etc.
- Surface
treatment, i.e., Special Cleanliness, Oiled, Dry lube,
etc.
- Steel
chemistry
- Cold Rolled
Full Hard Sheet Steel – a product manufactured by U.S. Steel most often to be applied to
further processing for applications such as continuous galvanizing. Specific
ordering practices allow the customer to specify the following:
- Sheet
dimensions
- Dimensional tolerances
- The
metallurgical designation, i.e., Commercial Steel, Drawing Steel,
etc.
- The
steel chemistry
- Vitreous
Enamel Sheet (Vitrenamel) – a cold rolled steel sheet product specifically processed with
enhanced attributes for porcelain enameling. As with conventional cold rolled
sheet, Vitrenamel Sheet can be ordered to specific dimensions and tolerances.
There are three designations of Vitrenamel Sheet available from U.S. Steel:
- USS
Vitrenamel 1Steel
- USS
Vitrenamel 2 Steel
- USS Flexnamel Steel
Each of these grades
has special properties to allow their use for different types of
porcelain enameling.
- Cold Rolled
Motor Lamination Sheet – specific grades of steel sheet made to be used for
electro-magnetic core material for electrical equipment components.
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This includes motors, generators, and transformers. The primary
property that is controlled during the manufacture of these steels
is the core loss. Core loss is the energy loss in
electrical equipment as heat generated by alternately magnetizing
and demagnetizing the components. The magnitude of the core loss is
determined by the chemical composition of the steel and the
processing of the core material. The other important
attribute is permeability which defines the ease of
magnetization. U.S. Steel supplies the following products for
use by the electrical-sheet industry:
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Laminations take an
enormous variety of shapes, sizes, and designs |
- USS
Type 1
- USS Type 2-S
- USS
Q-Core
- USS Q-Core II
- USS
Q-Core P 21
- USS
Q-Core P 19
- USS Q-Core XL
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