Cold-rolled coils

The standards applied in different countries to set the requirements for cold-rolled steel, such as EN 10130, EN 10268, EN 10209, ASTM A1008 / A1008M, DSTU 2834, GOST 16523, GOST 9045, GOST 17066 and others, specify steel grades and size ranges for cold-rolled coils, their application (profiling, cold forming, enamelling, general use, etc), mechanical properties, surface quality and other parameters.

Cold-rolled coils according to European standards

The most frequently followed European standards for producing cold-rolled coils are EN 10130, EN 10268 and EN 10209.

EN 10130 is applied to cold-rolled coils made of the low-carbon DC01, DC03, DC04, DC05, DC06 and DC07 steel grades for cold forming without coating, with a minimum width of 600 mm and a minimum thickness of 0.35 mm.

Cold-rolled steel manufactured in accordance with this standard is normally supplied skin-pass rolled, however, upon agreement, cold-rolled coils can be ordered without skin-pass rolling. The same is true of oiling used for rust protection. EN 10130 sets forth the requirements for surface quality (А, B) and finishing (gloss b, semi-gloss g, matte m, rough r) along with other parameters of cold-rolled coils. Acceptable size and shape tolerances should correspond to EN 10131.

EN 10268 relates to cold-rolled flat steel with a thickness of  3 mm or less and a high yield strength suitable for cold forming. These products are supplied in the form of sheets, wide strip, wide and narrow cut-to-length slit strip. The reference document applies to the following steel grades with different chemical compositions and mechanical properties:

• B – heat-treated steels (HC180B, HC220B, HC260B and HC300B), which demonstrate a certain increase in the reference yield strength after being heated to 170°С for 20 minutes
• LA – low-alloyed / micro-alloyed steels (HC260LA, HC300LA, HC340LA, HC380LA, HC420LA, HC460LA and HC500LA), which in their composition have one or several alloying elements, such as niobium, vanadium or titanium, to achieve the required yield strength
• Y – inclusion-free steels (HC180Y, HC220Y and HC260Y), whose composition is controlled to improve plastic deformation r and strain hardening n
• I – isotropic steel (HC220I, HC260I and HC300I), which has a minor parameter for plastic deformation r

Cold-rolled coils are supplied only as skin-passed material. Normally, rolled steel comes oiled. In this case, a homogeneous layer of neutral non-drying clean oil is applied to both sides for rust protection to avoid corrosion during three months of normal packing, transportation, handling and storage. Oil should be removable by alkaline solutions or common solvents. Cold-rolled coils are supplied with surface quality А or B as per EN 10130 , except for LA steel, which can have only А-type surface quality. Cold-rolled coils can be further used for metal coating by submerging the material into a metal bath, using electrolytic deposition, and/or applying organic and other types of coating. If such coating is required, this should be indicated in the request or order. The size and shape tolerances for products rolled to a thickness of 600 mm or more correspond to those indicated in EN 10131, while the tolerances for products rolled to a thickness of less than 600 mm correspond to EN 10140.

EN 10209 is used to manufacture cold-rolled coils from the low-alloyed DC01EK, DC04EK, DC06EK, DC03ED, DC04ED and DC06ED steel grades for vitreous enamelling of rolled steel with a width of 600 mm or more and a thickness of 3 mm or less, which is supplied in sheets or wide strip slit to several strips or cut-to-length. The standard specifies the key requirements for chemical composition, mechanical properties, surface quality and finishing, as well as the test methods for cold-rolled coils. The size and shape tolerances for such cold-rolled steel are specified in ЕN 10131.

Cold-rolled coils according to Ukrainian and CIS standards

In Ukraine and the CIS, the main standards for cold-rolled coils include:

• The DSTU 2834 and similar GOST 16523 standards are applied to thin-gauge material made from high-quality and regular-quality carbon steel for general applications, which is produced with a width of 500 mm or more and a thickness of up to 3.9 mm inclusive. Based on their ultimate strength, steel grades are classified into the following strength groups: K260V, K270V, OK300V, K310V, K330V, K350V, OK360V, OK370V, K390V, OK400V and K490V. Based on surface finish, products are classified into the following groups: I (super ultra finish), II (ultra finish) and III (extra finish). Based on drawing capacity, steel products are classified into products for deep drawing and normal drawing. The range of these cold-rolled products should correspond to GOST 19904.
• GOST 9045 specifies the requirements for thin-gauge, cold-rolled material made from low-carbon, high-quality steel with a thickness of up to 3.9 mm for cold forming. Based on surface finish quality, products are classified into the following groups: I (super ultra finish), II (ultra finish) and III (extra finish). Based on their drawing capacity (rolled products with a thickness of up to 2 mm), steel products are classified into products for super ultra complex, ultra complex, complex and deep drawing. The range of these cold-rolled products should correspond to GOST 19904.
• GOST 17066 describes the technical specifications for thin-gauge, high-strength rolled steel with a thickness of 0.5-3.9 mm and a minimum width of 500 mm manufactured in sheets and coils. Rolled steel is produced with a strength of 295, 315, 345, 355 or 390. The shape and size tolerances of cold-rolled steel should also correspond to GOST 19904.

Hot-rolled coils are used as feedstock to produce cold-rolled coils. The processing begins by pickling the feedstock in acid and washing on continuous pickling lines to remove scale and impurities from the strip surface. 

The coils are then transferred to continuous and reversing cold-rolling mills, where plastic deformation without pre-heating is applied until the cold-rolled coil reaches the customer’s required thickness. The external deformation force causes changes in the structure and, therefore, properties of the steel, which is called cold hardening. The structure of cold-hardened metal is characterised by the predominant orientation of crystals (texture) towards the rolling direction. While cold hardening promotes greater strength and hardness, as well as lower plasticity and viscosity, these properties may differ along the cross section of the coil. Therefore, once discharged from the rolling mill, most merchant cold-rolled coils go through heat treatment, ie annealing, in bell-type furnaces or on continuous lines. 

In the final production stage, the annealed cold-rolled coils are transported to coiling, skin-pass and straightening facilities, slitting or cutting machines, followed by inspection, packing and placing the cold-rolled coils in the finished goods storage area to be shipped to customers. 

Today, the following main equipment is used to produce cold-rolled coils:

• Modern continuous-rolling mills with 6-7 mill stands providing a rolling speed of up to 50 metres per second and a coil weight of up to 60 tonnes;
• Use of stiff mill stands with roll bending;
• A high level of process automation by using sensors for automatic in-line control of strip tension, gauge and width;
• Use of vertical or horizontal continuous heat-treatment lines.

The industries that primarily consume cold-rolled coils include construction, machine building, automotive, products with metal and organic coating, and white goods.

In the construction sector, cold-rolled steel is mainly used to produce tubes and closed sections, facade elements and steel structures. The key requirements for cold-rolled coils include minimum positive or negative thickness tolerances and a coil weight of up to 25 tonnes. High-strength, low-alloy steel grades are becoming more and more popular as they can reduce metal intensity and increase the load-bearing capacity of steel structures.

Most of the cold-rolled coil produced globally is used for further coating, the main types of which are metallic coating (zinc, zinc-aluminium, aluminium-zinc, aluminium, aluminium-silicon, silicon, magnesium, stannum , etc) and paint coating (polyester, polyurethane, plastisol, etc). The most important parameters for the sector include narrow thickness tolerances and minimum crown, which ensure smooth application of the coating along the strip length and width. The quality and purity of the cold-rolled coil surface should provide for smooth application of the coating material and prevent its exfoliation. Most customers need cold-rolled products with minimum oil film, which provides corrosion protection while also reducing degreasing costs.

For transport machine building and the manufacture of white goods, cold-rolled coils are predominantly used to manufacture cases, bodies and load-bearing elements of automobiles and other vehicles . The key requirements for rolled steel intended for bodies of white goods include high plasticity / formability, minimum crown, high quality and surface cleanness. The automotive sector sets further stringent requirements for geometry (thickness tolerance to be 1/2-1/4 of normal tolerances as per EN, special width tolerances, etc) and surface quality of cold-rolled coils (lustre finish and absence of any surface defects, marks or scratches). To achieve high formability when producing complex shaped items, limitations are imposed on chemical composition, as well as the level and uniform distribution of mechanical properties. Many body components must have high strength and plasticity at the same time, thus requiring the use of high-strength, multi-phase steels.

Large consumers of cold-rolled coils include service metal centres, which render their services to various sectors ranging from construction to precision engineering. At their sites, cold-rolled coils are subject to cut and slit to sheets and strips, also to laser cutting, bending, forming, etc. Therefore, requirements that are typical of end application may be set for products intended for metal service centres.

Buy cold-rolled coils from manufacturer

Metinvest produces cold-rolled coils in a thickness range of 0.35-2.0 mm from carbon and low-alloy steel in accordance with the requirements of international standards. Cold-rolled coils are available as heat-treated and cold-hardened. Cold-rolled coils can be purchased through the Group’s global sales network of 38 sales offices in Europe, Asia, Africa and North America, as well as 16 metal service centres in Ukraine and authorised dealers.