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What is cold rolled coil?

In general, to prepare products with good surface finish and accurate dimensions, such as galvanized sheet, belt, rod and metal pipe, they are cold rolled. Due to its smaller size and greater strength compared to hot rolling, the majority of cold rolling is made with 4-layer and cluster or satellite rollers. Therefore, cold sheet refers to sheets created by cold rolling.

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Application of cold sheet

Due to the good appearance quality, most of these sheets are used in appearance-related works. Among them, we can mention the automotive industry, office furniture, household appliances, making all kinds of shelves, making non-flexible panels, building materials.

Getting to know the cold rolling process:

Sheet thickness reduction in cold rolling is done by one or more reciprocating rolling racks or several tandem (chain) rolling racks. Each rolling rack includes a steel frame in which the roller bearings are placed and bears the force applied to the bearings and resulting from the rolling force. In order to reduce the force and power, increase the accuracy and uniformity of the thickness of thin sheets, four-roller racks are used.

These shelves include work rollers and support rollers. Working rollers with a smaller diameter are in direct contact with the sheet, and support rollers with a larger diameter are used to prevent the working rollers from deflecting and bending.

Types of cold sheets:

  • Galvanized sheet:

The iron on which zinc metal is coated is called galvanized sheet.

The amount of zinc coating on the sheets is different based on the mass of the metal on them and is in the range of 100 to 350 grams per square meter. Galvanized sheet is produced in two forms, roll form and fabric. The galvanized roll sheet has different thickness, which is available in the market from 0.18 mil to 6 mil with two widths of 100 cm and 125 cm.

Also, galvanized fabric sheets are produced with sizes of 2000*1000 mm and 2500*1250 mm.

The weight of each galvanized roll sheet is about 5 to 7 tons according to its width and thickness.

  • Color sheet:

Colored sheets are widely used in industries such as home appliance production, transportation industry and construction. The applications of colored galvanized sheets are also wide ranging from home appliance manufacturing industries to transportation and construction industry. But one of the most common uses of using colored sheets is the construction and installation of building roofs in geographical areas with high rainfall and humidity. In addition to the appearance of these sheets, resistance to rust and corrosion is also an important factor in choosing these sheets as the roof of the building.

  • Oiled sheet:

Cold rolled steel sheets are a type of steel sheet produced during the cold rolling process. These products have a smooth and uniform surface, and ductility and tensile strength are among their most important mechanical properties. The characteristics of these sheets have made traces of these products visible in every industry. It is enough to read this article until the end so that you become one of the millions of craftsmen who use these steel sheets in the world.

Types of oil sheets

Oil sheets are classified into the following three categories based on the alloy used in them (the percentage of carbon, manganese, silicon, phosphorus, sulfur, chromium, etc.) and also the heat treatment done to make them. Of course, there are other types of oil sheets, two of which can be mentioned as anti-wear sheets (EK2) and anti-rust sheets (QSTE).

Standard sheet ST12

It is the most widely used oil sheet and is used for all kinds of construction or industrial structures. This type of sheet, which is known as tensile sheet, can be bent up to 45 degrees. One of the advantages of this type of oil sheet is its high expiration date, which is up to 18 months.

Semi-stretch sheet ST13

This type of sheet is used in industrial and non-industrial structures with shallow pressing. This product, which is also called semi-stretch or semi-elastic sheet, can be bent up to 90 degrees and its expiration date is at most 8 months. This sheet has good welding ability.

Super tensile sheet ST14

Due to having a more flexible structure than other oil sheets, this sheet is used in industries such as automobile manufacturing where deep pressing is done. This product can be completely folded and its expiration date is 8 months.

Oil sheet specifications

Heat treatment on oiled sheets has completely separated the characteristics of these sheets from hot rolled sheets. The mechanical properties of oil sheets, which have made them more resistant to stretching and as a result of breakage, have made these sheets widely used in industries such as automobile manufacturing and home appliance manufacturing. Black sheet is the raw material for the production of oil sheets. During cold rolling heat treatment, oily sheets change their mechanical properties and become more malleable than black sheets. In addition, their tensile strength increases by 20%.

On the other hand, this heat treatment makes the surface of the sheet smoother, more uniform and of higher quality. This surface quality of oiled sheets has made them the best raw materials for making galvanized and colored sheets. In general, it can be said that in industries where only mechanical properties are important and appearance is not considered, the use of black sheets is preferred because their price is much lower compared to oiled sheets.

But in industries such as automobile manufacturing and home appliance manufacturing, where the appearance of the body as well as malleability is very important, the use of cold rolled sheets is necessary. These sheets are used to create delicate forms with high precision. In addition, the high resistance of these sheets against strain has made them retain their characteristics after manufacturing and do not undergo deformation.

The thickness of the oil sheet

Cold rolling machines usually have thickness gauges in the output section of the product. The rollers of these devices are designed so that the movement of the sheet can be reversed in them. In this way, if the thickness of the steel did not reach the desired level, the steel will move in reverse again and as the rollers get closer, the sheet will reach the required thickness. This process is repeated until the desired thickness is obtained. Some machines are also in such a way that the sheet should be re-entered from the beginning and the process of thinning the sheet should be done again as the rollers approach.

Usually, every time it passes through the rollers, it reduces the thickness between 50 and 90%. Due to the compressive forces and friction between the surfaces, the temperature of the surface may reach more than 250 degrees, as a result, a cooling agent is needed to cool the surface, which is usually oil or water. The thickness of the oil sheet can be between 0.12 and 3 mm. Of course, its standard sizes are 0.35 to 3 mm.

Standard width of oil sheet

The thickness of the oil sheet is in the range of 0.35 to 3 mm and the standard width is 100 to 125 mm. The following formula can be used to calculate the weight of the oil sheet:

Length (meters) * width (meters) * thickness (mm) * 85.7 = weight (kilograms)

The method of producing oiled sheets

Oil sheets are created through cold rolling process. Black sheets, as the raw material for the production of cold sheets, enter the acid washing stage. At this stage, the oxide layer on the black sheet is removed and the steel surface is prepared to enter the cold rolling process. The difference between oil and black sheets starts from this stage.

Producers of oiled sheets in Iran

Among the most important producers of oiled sheets in Iran, the following large companies can be mentioned:

  • Mubarake steel of Isfahan

  • Haft Almas Industries Co

  • Gharb Steel Factory

  • Arak Iron and Steel Industries Co

Application of oiled sheet in industries

As mentioned, cold-rolled steel sheets are used in industries that require formability, elegance and precision due to their high surface quality and suitable formability.

  • Automotive industry: production of car filters, car mudguards, exhaust pipes and other small and large car parts.

  • In the manufacture of electrical household appliances such as refrigerators, microwaves, gas stoves, in the manufacture of radiators, the manufacture of cabinets, wardrobes and all kinds of fittings.

  • Construction profiles such as: some door and window profiles

  • Plated tin plate:

Coated tin sheet is a type of oil sheet (cold rolled) that during the coating process, different thicknesses of tin are placed on its surface and usually the final surface is covered with a thin layer of chrome for protection. The most important feature of this sheet is the preservation of food and other products, as well as excellent formability and non-fragility during transportation, which has made it used in food, chemical, pharmaceutical, etc. packaging industries.