Cold rolled steel plate
Steel plate produced by a cold rolling process
Cold rolling is made of hot rolled sheet coil as raw material, rolled at normal temperature and below the recrystallization temperature. Cold rolled steel plate is the steel plate produced by cold rolling process, referred to as cold plate. The thickness of cold-rolled sheet is generally between 0.1-8.0mm, and the thickness of cold-rolled sheet produced by most factories is below 4.5mm. The thickness and width of cold-rolled sheet are determined according to the equipment capacity of each factory and the market demand.
Introduction
Cold rolling is the further thinning of steel sheet to the desired thickness at room temperature and below the recrystallization temperature. Compared with hot – rolled steel, cold – rolled steel plate thickness is more accurate, and the surface is smooth and beautiful.
Development Overview
Hot strip rolling
1940s to 1950s, the first generation, annual output of 1 million to 2.5 million tons.
1960s, the second generation, annual output of 2 million to 3.5 million tons.
1970s, the third generation, annual output of 3 ~6 million tons.
Strip cold rolling
Generally with the weight of 40 t, individual to 60 t, increased by 30~50%.
The main measures to improve the productivity, increase the weight of roll, improve the rolling speed and operation rate.
Major differences
Hot rolled
Hot rolling is to make strip steel from roughing mill and finishing mill by heating slab (mainly continuous casting billet) as raw material. The hot steel strip from the last finishing rolling mill is cooled to the set temperature through laminar flow, and is rolled into steel strip coil by the coiler. The cooled steel strip coil is processed into steel plate, flat coil and longitudinal strip products by different finishing lines (leveling, straightening, cross-cutting or longitudinal cutting, inspection, weighing, packaging and marking, etc.) according to different needs of users. To put it more simply, a slab of steel is heated (the red, hot piece of steel that burns on TV), rolled several times, trimmed, and straightened into a steel plate. This is called hot rolling.
Cold rolled
Cold rolling: using hot rolled steel coil as raw material, after pickling to remove the oxide skin, cold continuous rolling, the finished product is rolled hard roll, because of the cold hardening caused by continuous cold deformation of the rolled hard roll strength, hardness, toughness and plastic index decreased, so the stamping performance will deteriorate, can only be used for simple deformation parts. Rolled hard rolls can be used as raw materials in hot-dip galvanizing plants because hot-dip galvanizing units are equipped with annealing lines. Rolled hard coil weight is generally 6~13.5 tons, steel coil at room temperature, hot rolled pickling coil continuous rolling. The inner diameter is 610mm.
Product features: Because it has not been annealed, its hardness is very high (HRB is greater than 90), the machining performance is very poor, can only be simple directional bending processing less than 90 degrees (perpendicular to the winding direction).
To put it simply, cold rolling is a process rolled out on the basis of hot rolled sheet rolls. Generally speaking, it is a process of hot rolling – pickling – cold rolling.
Cold rolling is made of hot rolled sheet at normal temperature. Although the steel sheet will be heated by rolling during the process, it is still called cold rolling. Because of the continuous cold rolling, the mechanical properties of cold rolling are relatively poor and the hardness is too high. Must be annealed to restore its mechanical properties, not annealed called rolled hard roll. Rolled hard rolls are generally used to make no bending, stretching products.
Allowable deviation of steel plate width
Table 5-13 Cold-rolled steel plates and strips
| Nominal width /mm |
Width permissible deviation /mm
|
|
≤l000
|
+6
|
|
>1000
|
+10
|
|
A strip of steel without cutting the longitudinal edge
|
+15
|
Table 5_14 Permissible widths of longitudinally cut steel strips
|
Nominal thickness /mm
Nominal thickness /mm |
Width permissible deviation /mm
|
|||
|
≤125
|
>125～250
|
>250～400
|
>400～
|
|
|
0.20～0.40
|
+0.3
|
+0.6
|
+1.0
|
+1.5
|
|
>0.40～1.0
|
+0.5
|
+0.8
|
+1.2
|
+1.5
|
|
>1.0～1.8
|
+0.7
|
+1.0
|
+1.5
|
+2.0
|
|
>1.8～3.0
|
+1.0
|
+1.3
|
+1.7
|
+2.0
|
Table 5-15 Permissible length deviations of cold rolled steel plates
|
Nominal length /mm
|
≤2000
|
>2000
|
|
Allowable deviation /mm
|
+10
|
+15
|
Table 5-16 Shapes of cold-rolled steel plates and strips
|
Flatness of sheet and strip per meter
|
Of steel belt Sickle blade bend
|
Steel plate Same plate difference
|
|||
|
Nominal width /mm
Nominal width /mm |
Flatness (mm/m)
|
||||
|
≤0.70
|
>0.70～1.50
|
>1.50～5.0
|
|||
|
≤1000
|
10
|
8
|
6
|
In every 2m
2 m |
Not more than half of the thickness tolerance
|
|
>1000～1500
|
12
|
10
|
8
|
||
|
>1500～2000
|
18
|
15
|
12
|
||
Note: The flatness listed in the table applies to steel plates and strips with ob lower limit not greater than 485MPa. The maximum flatness of steel plates and strips with a lower limit of ob greater than 485MPa but not greater than 585MPa is allowed to increase by 30% from the value specified in the table. The maximum flatness of steel plates and strips with a lower limit of ob greater than 585MPa is allowed to be 50% higher than the value specified in the table.
(3) widely used in the automobile industry, household appliances industry, building materials industry and small commodity production.
Application
Cold-rolled strip is widely used, such as automobile manufacturing, electrical products, rolling stock, aviation, precision instruments, food canning and so on. Cold rolled steel sheet is short for cold rolled plate of ordinary carbon structural steel, also known as cold rolled plate, commonly known as cold plate, sometimes mistakenly written as cold tie plate. Cold plate is made of ordinary carbon structural steel hot rolled strip, after further cold rolling to make a thickness of less than 4mm steel plate. Because of the rolling at normal temperature, no oxide sheet is produced, so the surface quality of cold plate is good, the dimensional precision is high, coupled with annealing treatment, its mechanical properties and technological properties are better than the hot rolled sheet steel, in many fields, especially in the field of home appliance manufacturing, has been gradually used to replace the hot rolled sheet steel.
Main producing area
The main producing areas are: Baosteel, Shougang, Angang, Bensteel, Wisco, Handang, Baotang, Tanggang, Lian Steel, Jinan Steel, Angang and so on.
