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.

Metal Roof Specific Steel Parameters

To meet DML USA Metal Roofing System’s requirements,
cold-rolled steel is metallurgically designed
to provide specific attributes such as
high formability, deep drawability, high strength,
high dent resistance, good magnetic properties,
enamelability, and paintability.

Cold Reduction

The first step in manufacturing 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 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 DML USA.

 

Important attributes

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 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.

 

As one can see, there is much more to cold rolling than simply reducing the thickness to meet a DML USA’s ordered thickness. In fact, the hot-rolled, pickled coils incoming to 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 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.

The production of a specific thickness of cold rolled sheet to meet DML USA’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.