Cold Rolled Steel:

Cold Rolled Steel:

Cold rolling takes place below re-crystallization temperature of steel. Cold rolled sheet products have been available for many, many years, and have been successfully used for a multitude of applications. 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.

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. 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.

The primary feature of cold reduction is to reduce the thickness of hot-rolled coils into 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 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.

One of the important operations is the pickling operation, which 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.

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.