Colored Sheet Production Line

 Colored Sheet Production Line

 

The old houses along the roads of northern Iran, with their rusted gray and black roofs, significantly diminished the beauty of the landscape. However, such scenes have now become rare and can hardly be seen in most places.

These days, while passing through such routes, we encounter houses with colorful and beautiful sloped roofs that create sweet memories for us. In fact, ever since the use of colored galvanized sheets for sloped roofs became common, many houses have taken on a different appearance.

In this article, we aim to explore the production process of colored sheets and discuss the various types of these beautiful sheets and their applications.

What is a Colored Sheet?

A colored sheet is a product made of galvanized steel, covered with a layer of paint on its surface. In essence, with the production of these sheets, vibrant colors have been introduced into the previously rusted gray world.

 

The widespread use of these sheets in various industries has led to an increasing demand for colored sheet production, with new and diverse designs and colors continuously entering the market. Below, we briefly highlight some of the applications of these sheets:

  • Metal Industries: They are widely used in manufacturing cabinets and other metal structures.
  • Construction and Temporary Housing: Various types of colored galvanized sheets are used for the interior and exterior facades of buildings, warehouses, prefabricated structures, and container bodies.
  • Household Appliance Manufacturing: Colored sheets play a significant role in producing the bodies of computers, washing machines, refrigerators, and other home appliances.

To produce colored galvanized sheets, a metal ingot or a piece of alloyed metal must undergo multiple stages to be transformed into a finished colored galvanized sheet.

For this process, metal ingots and a set of machinery are required to transform the ingot into a steel sheet, shape it into the desired form, and finally coat its surface with the preferred color. Below, we outline the steps that a piece of metal must go through to become a colored sheet:

Hot Rolling

At this stage, slabs, ingots, and other raw materials are heated in continuous furnaces until they become molten steel paste. After undergoing various processes and passing through different production and leveling stages, they are converted into hot-rolled sheets, also known as black sheets.

Cold Rolling (Oiled Sheet)

Hot-rolled sheets are processed through leveling machines and rollers to be transformed into cold-rolled sheets.

Galvanized Sheet

Cold-rolled sheets go through a galvanization process and are dipped in molten zinc baths to become galvanized sheets.

Degreasing the Metal Sheet

To ensure that the desired paint adheres firmly to the sheet, the surface must be cleaned of any dust, grease, or impurities. Degreasing is done using either the electrical method or alkaline washing.

Since the electrical method is costly, the more common approach is using alkaline detergents. In this process, the sheets are immersed in alkaline solution baths, then washed with hot water, and finally dried with warm air.

Chromating the Metal Sheet

After washing and degreasing, the sheets undergo chromating to enhance their corrosion resistance and improve paint adhesion. This step ensures that the final product retains its color without peeling.

Primary Coating

At this stage, an initial layer of epoxy or polyester primer is sprayed onto the sheet, which is then passed through an oven. This primer serves as the base coat for the final paint. The coating thickness in this stage is typically 7 to 15 microns.

Final Painting and Curing

Finally, the sheet is coated with the main polyurethane, polyamide, acrylic, epoxy, or polyester paint using the electrostatic method. After painting, the sheet is passed through a curing oven to ensure the paint adheres permanently.

Typically, the final coating consists of two layers: a top layer and an underside layer. Additionally, the material used in each layer is selected based on the intended application of the sheet.