Cold rolled coil

   Products made mainly from hot rolled coils

Cold rolled coil is made of hot rolled coil and rolled at room temperature below the recrystallization temperature. It includes plates and coils. The ones delivered in sheets are called steel plates, also called box plates or flat plates; the ones delivered in long lengths in coils are called steel strips, also called coils.

Hot rolled coil

Basic Information

Cold rolled coil (annealed state) is obtained by hood annealing of the cold hardened coil before rolling. After annealing, the work hardening phenomenon and internal stress are eliminated (greatly reduced), that is, the yield strength is reduced to a level close to that before cold rolling.

Cold rolling is defined as rolling under recrystallization , but it is generally understood as rolling using room temperature rolled materials. Aluminum cold rolling is divided into plate rolling and foil rolling. Plates with a thickness of 0.15~ or more are called plates, and foils with a thickness of 0.15~ or less are called foils. Europe and the United States mostly use 3 to 6 continuous rolling mills as cold rolling equipment.

Since no heating is performed during the production process, there are no defects such as pitting and iron oxide scale that are common in hot rolling, and the surface quality is good and the finish is high. In addition, the dimensional accuracy of cold-rolled products is high, and the performance and organization of the products can meet some special use requirements, such as electromagnetic performance, deep drawing performance, etc.

Specifications: thickness 0.2-4mm, width 600-2 000mm, steel plate length 1 200-6 000mm.

Brand: Q195A-Q235A, Q195AF-Q235AF, Q295A (B)-Q345 A (B); SPCC , SPCD , SPCE , ST12-15; DC01-06

Performance: Mainly use low carbon steel grades, require good cold bending and welding properties, as well as certain stamping performance .

Chemical composition

The difference is that the coil is a type of steel plate , which is actually a long, narrow thin steel plate supplied in coils .

Rolls and flat sheets are almost the same as a cut package

Chilled coil is obtained by pickling and cold rolling hot rolled coil , which can be said to be a kind of cold rolled coil.

Cold-rolled coil (annealed): Hot-rolled coil is obtained by pickling, cold rolling, hood annealing , flattening , and (finishing).

There are three main differences between the two:

1. In appearance, the cold-hardened coil is generally a little dark.

2. The surface quality, structure, dimensional accuracy, etc. of cold-rolled plates are better than those of cold-hardened coils.

3. In terms of performance, the cold-hardened coil obtained directly from the hot-rolled coil undergoes work hardening during cold rolling , which increases the yield strength and leaves some internal stress . It appears to be "harder" externally, so it is called cold-hardened coil.

Therefore, the yield strength of the cold-hardened coil is greater than that of the cold-rolled coil (annealed state), which makes the cold-rolled coil (annealed state) more conducive to stamping.

Generally, the default delivery state of cold-rolled coil is annealed.

Mechanical properties

DC01、DC02、DC03、DC04

SPCC、SPCD、SPCE

Note: (a) For tensile test, transverse specimen is used; the specimen width b is 25 mm and the specimen gauge length L0 is 50 mm.

(b) When there is no obvious yield point , Rel can be replaced by Rp0.2; when the product thickness is less than 0.70mm and ≥0.50mm, the upper limit of yield strength can be increased by 20N/mm2, and when the thickness is less than 0.50mm, it can be increased by 40 N/mm2;

(e) When the product thickness is greater than 1.50 mm and less than or equal to 2.0 mm, the value of r90 or r is allowed to be reduced by 0.1 (absolute value); when the thickness is greater than 2.0 mm, the value of r90 or r is allowed to be reduced by 0.2 (absolute value);

(d) The values of r90 and n90 or r and n are only applicable to products with a thickness of ≥ 0.50 mm; r = (r0 + r45 + r90) / 4,

n=(n0+ n45+ n90)/4。

Market Conditions

In April, the domestic cold-rolled coil market price fell slightly, especially in the second half of the month. The first quarter economic data released by the National Bureau of Statistics on the 15th was lower than market expectations; electricity consumption in March also fell significantly, hitting a 46-month low, indicating that the domestic economic situation has not seen a solid recovery as the weather warms up, which has aggravated the market's cautious wait-and-see and even pessimistic mood to a certain extent. The pressure on capital recovery increased at the end of the month, and market prices loosened again. More importantly, high production capacity, high inventory and demand release speed are not proportional, so it is difficult to say that the domestic cold-rolled market has improved recently. However, it is rumored that Hebei Province will reduce 1/3 of its steel production capacity . If it is truly implemented, it will be a big boon to the market, and the decline in cold-rolled prices may slow down or even rise slightly.

Application Areas

Brand, supply standard, product size and use

Cold rolled strip

It has a wide range of uses, such as automobile manufacturing, electrical products, locomotives and rolling stock, aviation, precision instruments, canned food, etc.  Cold-rolled steel sheet is the abbreviation of ordinary carbon structural steel cold-rolled sheet , also known as cold-rolled sheet, commonly known as cold plate , and sometimes mistakenly written as cold-rolled sheet . Cold plate is made of ordinary carbon structural steel hot-rolled steel strip, which is further cold-rolled into a steel plate with a thickness of less than 4mm. Since it is rolled at room temperature and no iron oxide scale is produced , the surface quality of the cold plate is good and the dimensional accuracy is high. In addition , after annealing , its mechanical properties and process properties are better than those of hot-rolled steel sheet . In many fields, especially in the field of home appliance manufacturing, it has gradually replaced hot-rolled steel sheet.

Applicable grades: Q195 , Q215 , Q235 , Q275 ; SPCC (Japanese grade); ST12 (German grade)

symbol:

1. Q is the code for the yield point (limit) of ordinary carbon structural steel , which is the uppercase and lowercase of the first Chinese phonetic letter of "Qi"; 195, 215, 235, 255, 275 respectively represent the values of their yield points (limits), unit : MPa (N/mm2); Since the comprehensive mechanical properties of Q235 steel such as strength, plasticity, toughness and weldability are the best among ordinary carbon structural steels and can better meet general use requirements, it has a very wide range of applications.

2. S-Steel, P-Plate, C-cold rolled, and the fourth digit C-common.

3. ST-Steel, 12-Ordinary grade cold-rolled thin steel plate, Marking: Dimensional accuracy-Dimension-Steel plate variety standard  Cold-rolled steel plate : Steel grade-Technical conditions Standard marking example: B-0.57501500-GB708-88; Steel plate, standard number Q/BQB402, brand SPCC , heat treatment state annealing + flattening (S), surface processing state is pitted surface D, surface quality is FB grade trimmed edge (trimmed edge EC, untrimmed edge EM) Steel plate, thickness 0.5mm, B grade accuracy, width 1000mm, A grade accuracy, length 2000mm, A grade accuracy, unevenness accuracy is PF.A, then the mark is: Steel plate ECQ/BQB 402-SPCC-SD-FB/(0.51000A2000A-PF.A); '

Cold rolled steel sheet

Grade: Q225-GB912-89 Main production places: Baosteel, Ansteel, Benxi Steel, Wuhan Steel , Handan Steel, Baotou Steel, Tangshan Steel, Liangang Steel , Ji'nan Steel, etc.

Cold-rolled ordinary thin steel plate : It is made by cold rolling ordinary carbon structural steel or low alloy structural steel . The surface quality of cold-rolled plate is good. It has good stamping performance . It is required to ensure that the cold bending and cup tests are qualified. It is often used in industries such as automobiles and raw materials for coated plates .

Cold-rolled high-quality thin steel plates : mainly include various high-quality steel cold-rolled thin plates, the most commonly used are carbon structural steel plates , especially cold-rolled thin steel plates for deep stamping , which are thin plates cold-rolled from low-carbon high-quality steel 08Al. Steel plates are divided into three groups according to surface quality; Ⅰ, Ⅱ, Ⅲ, respectively representing special high-grade, high-grade, and high-grade finishing surfaces, and are divided into ZF, HF, and F grades according to drawing levels (representing the most complex, very complex, and complex parts used for punching and drawing). According to the allowable deviation of steel plate thickness, it is divided into A and B grades of accuracy, and is widely used in the automobile and tractor industries.

Cold-rolled steel sheet : With smooth surface and excellent processing, it is used in automobiles, refrigerators, washing machines and other home appliances, as well as industrial equipment and various building materials. With the development of the economy, cold-rolled steel sheet has been called an essential material in modern society.  Classification of cold-rolled products : hot-rolled pickling, hard-rolled coils , ordinary cold-rolled, galvanized ( electro-galvanized , fingerprint-resistant, hot-dip galvanized ), aluminum-zinc -plated , electro-tin-plated , color-coated, electrical steel ( silicon steel sheet ), etc.

Hot rolling pickling:

Hard rolled coil: hot rolled pickled coil is continuously rolled at room temperature .

Product features: Because it has not been annealed , its hardness is very high (HRB greater than 90), and its machining performance is extremely poor . It can only be bent in a simple direction less than 90 degrees (perpendicular to the coiling direction).