What are the materials and classifications of steel plates?
Common steel plates are made of ordinary carbon steel, stainless steel, high-speed steel, high-manganese steel, etc. Their main raw material is molten steel, which is a material made by mechanical pressing after the molten steel is poured and cooled. Most steel plates are flat or rectangular, which can not only be pressed mechanically, but also cut with wide steel strips.
So what are the types of steel plates?
Thickness
(1) Thin plate: thickness <4 mm
(2) Medium plate: 4 mm~20 mm
(3) Thick plate: 20 mm~60 mm
(4) Extra thick plate: 60 mm~115 mm
Production method
(1) Hot-rolled steel plate: Hot rolling is made from slabs (mainly continuous casting slabs) as raw materials, which are heated and made into strip steel by rough rolling mills and finishing mills. The hot steel strip coming out of the last rolling mill of the finishing rolling mill is cooled to the set temperature through laminar flow and rolled into a steel strip coil by the coiler. The cooled steel strip coil is processed into steel plates, flat coils and longitudinally cut steel strip products through different finishing lines (flattening, straightening, cross-cutting or longitudinal cutting, inspection, weighing, packaging and marking, etc.) according to the different needs of users. In simple terms, a piece of steel billet is rolled several times after heating, and then trimmed and corrected into a steel plate. This is called hot rolling.
(2) Cold-rolled steel plate:
Cold rolling uses hot-rolled steel coil as raw material, and after pickling to remove the oxide scale, it is cold-rolled continuously. The finished product is hard-rolled coil. Due to the cold work hardening caused by continuous cold deformation, the strength and hardness of the hard-rolled coil increase, and the toughness and plasticity index decrease. Therefore, the stamping performance will deteriorate and it can only be used for parts with simple deformation. Hard-rolled coil can be used as raw material for hot-dip galvanizing plants, because hot-dip galvanizing units are equipped with annealing lines. The weight of hard rolled coil is generally 6~13.5 tons. The steel coil is continuously rolled at room temperature for hot-rolled pickled coil. The inner diameter is 610mm.
The product features are that because it has not been annealed, its hardness is very high (HRB greater than 90), and its mechanical processing performance is extremely poor. It can only be simply directional and less than 90 degrees bending (perpendicular to the coiling direction). Simply put, cold rolling is processed and rolled on the basis of hot-rolled coils. Generally speaking, it is a process of hot rolling-pickling-cold rolling.
Cold rolling is processed from hot-rolled plates at room temperature. Although the steel plate will heat up during the processing process due to rolling, it is still called cold rolling. Because the cold rolling is formed by continuous cold deformation of hot rolling, the mechanical properties are relatively poor and the hardness is too high. It must be annealed to restore its mechanical properties. The unannealed one is called hard rolled coil. Hard rolled coil is generally used to make products that do not require bending or stretching.
According to the different needs of manufacturers, cold-rolled plates are usually divided into:
General cold-rolled plates, stamping grade cold-rolled plates, deep drawing, extra deep drawing and ultra deep drawing grade cold-rolled plates, generally delivered in coils and flat plates, thickness expressed in millimeters, width generally: 1000mm and 1250mm, length generally 2000mm and 2500mm.
Common grades of ordinary cold-rolled plates are:
Q195, Q215, Q235, 08AL, SPCC, SPCD, SPCE, SPCEN, ST12, ST13, ST14, ST15, ST16, DC01, DC03, DC04, DC05, DC06, etc.;
ST12: indicates the most common steel grade, which is basically the same as Q195, SPCC, and DC01 grades;
ST13/14: indicates stamping grade steel grade, which is basically the same as 08AL, SPCD, and DC03/04 grades;
ST15/16: indicates stamping grade steel grade, which is basically the same as 08AL, SPCE, SPCEN, and DC05/06 grades.
The grade and size representation method of ordinary cold-rolled plates:
For example, Anshan Iron and Steel produces ST12, 112502500/C, which is represented as: grade ST12 ordinary cold plate, thickness 1mm, width 1250mm, length 2500mm or C coil. The appearance is tinplate packaging, and the mechanical properties are the most common and basic steel grades. It can only be used for bending and forming, not for stamping. It is used for mechanical bites, such as refrigerator shells, vehicle fuel tanks, etc. Products above ST13 are used in industries that require deep drawing, such as automobile manufacturing, diesel engine fuel tanks, etc. Which one to use depends on the requirements of its deep drawing.
The difference between ST12 and SPCC: The mechanical properties of the two products are almost the same, but the annealing methods are different. The tensile properties of ST12 products are relatively stronger than those of SPCC.