GNEE adopts cutting-edge cold-rolled pickling production technology to supply a full range of first-class pickled steel plates and cold-rolled steel plates. GNEE has a powerful pickling and cold-rolling combined unit with a rolling force of 3,500 tons.
What is the difference between pickled plates and hot-rolled plates?
Pickled plates: are made of high-quality hot-rolled thin plates. After the pickling unit removes the oxide layer, trims the edges, and finishes, the surface quality and use requirements (mainly cold bending or stamping performance) are intermediate products between hot-rolled plates and cold-rolled plates.
Hot-rolled plates: have relatively low strength, poor surface quality (oxidation, low finish), but good plasticity, and are generally medium and thick plates.
Features of pickled plates compared to hot-rolled plates:
1. Good surface quality. Compared with ordinary hot-rolled plates, hot-rolled pickled plates remove surface oxide scale, improve the surface quality of steel, and facilitate welding, oiling and painting.
2. High dimensional accuracy. After flattening, the plate shape can be changed to a certain extent, thereby reducing the deviation of unevenness.
3. Improve the surface finish and enhance the appearance effect.
Do you know the difference between cold-rolled steel plates and hot-rolled steel plates?
1. The surface of cold-rolled steel sheet has a certain glossiness and feels smooth to the touch, similar to the common steel cup used for drinking water.
2. If the hot-rolled steel sheet is not pickled, it is similar to the surface of many ordinary steel sheets on the market. The rusted surface is red, and the unrusted surface is purple-black (iron oxide).
Compared with hot-rolled steel sheet, the performance advantages of cold-rolled steel sheet are:
(1) Higher precision, the thickness difference of cold-rolled steel strip does not exceed 0.01~0.03mm.
(2) Thinner size, the thinnest cold-rolled steel strip can be 0.001mm; the thinnest hot-rolled steel strip can now reach 0.78mm.
(3) The surface quality is better, cold-rolled steel sheet can even produce a mirror surface; while the surface of hot-rolled steel sheet has defects such as iron oxide scale and pitting.
(4) Cold-rolled steel sheet can adjust its operating performance such as tensile strength and process performance such as stamping performance according to user requirements.
Cold rolling and hot rolling are two different steel rolling technologies. As the name implies, cold rolling is rolling steel at room temperature, and this kind of steel has high hardness. Hot rolling is rolling steel at high temperature.
Hot-rolled plates have low hardness, are easy to process, and have good ductility.
Cold-rolled plates have high hardness and are relatively difficult to process, but are not easy to deform and have high strength.
Hot-rolled plates have relatively low strength and poor surface quality (oxidation and low finish), but good plasticity, and are generally medium and thick plates.
Cold-rolled plates have high strength, high hardness, and high surface finish. They are generally thin plates and can be used as stamping plates.
The mechanical properties of hot-rolled steel plates are far inferior to those of cold processing and are also inferior to forging processing, but they have good toughness and ductility.
Cold-rolled steel plates have a certain degree of work hardening and low toughness, but can achieve a good yield strength ratio, which is used to cold-bend parts such as spring leaves. At the same time, because the yield point is closer to the tensile strength, there is no foreseeability of danger during use, and accidents are prone to occur when the load exceeds the allowable load.
By definition, steel ingots or billets are difficult to deform and process at room temperature. They are generally heated to 1100-1250℃ for rolling. This rolling process is called hot rolling.
Most steels are rolled by hot rolling. However, because the surface of steel is prone to generate iron oxide scale at high temperatures, the surface of hot-rolled steel is rough and the size fluctuates greatly. Therefore, steel with smooth surface, precise size and good mechanical properties is produced by cold rolling with hot-rolled semi-finished products or finished products as raw materials.
Rolling at room temperature is generally understood as cold rolling. From the perspective of metallurgy, the boundary between cold rolling and hot rolling should be distinguished by the recrystallization temperature. That is, rolling below the recrystallization temperature is cold rolling, and rolling above the recrystallization temperature is hot rolling. The recrystallization temperature of steel is 450-600℃.
As the name suggests, hot rolling has a high temperature of the rolled piece, so the deformation resistance is small and a large deformation amount can be achieved. Taking the rolling of steel plates as an example, the thickness of continuous casting billets is generally about 230mm, and after rough rolling and finishing rolling, the final thickness is 1~20mm.
At the same time, due to the small width-to-thickness ratio of steel plates, the dimensional accuracy requirements are relatively low, and plate shape problems are not easy to occur, and the main focus is on controlling convexity. For those with organizational requirements, it is generally achieved through controlled rolling and controlled cooling, that is, controlling the start rolling temperature, final rolling temperature and curling temperature of finishing rolling to control the microstructure and mechanical properties of the strip.
Cold rolling generally does not have a heating process before rolling. However, due to the small thickness of the strip, plate shape problems are prone to occur. Moreover, after cold rolling, it is a finished product. Therefore, in order to control the dimensional accuracy and surface quality of the strip, many very cumbersome processes are used.
The cold rolling production line is long, with many equipment and complex processes. With the improvement of users' requirements for strip dimensional accuracy, plate shape and surface quality, the control model, L1 and L2 systems, and plate shape control methods of the cold rolling unit are more than those of hot rolling. Moreover, the temperature of the rollers and strips is also one of the more important control indicators.
Generally speaking, cold-rolled products and hot-rolled products are the difference between the previous process and the next process. Hot-rolled products are the raw materials of cold-rolled products. Cold-rolling is to put the hot-rolled steel coils that have been pickled on the machine and roll them using a roller rolling mill. They are all cold-processed and formed. The main purpose is to roll thick hot-rolled plates into thin cold-rolled plates. Usually, 3.0mm hot-rolled plates can be rolled on the machine to produce 0.3-0.7mm cold-rolled coils. The main principle is to use the extrusion principle to force deformation.
Common steel hot and cold rolling situations:
Wire rod: 5.5-40 mm in diameter, coiled, all hot-rolled materials. After cold drawing, it belongs to cold-drawn materials.
Round steel: Except for bright materials with precise dimensions, they are generally hot-rolled, and there are also forged materials (there are forging marks on the surface).
Strip steel: Both hot-rolled and cold-rolled, cold-rolled materials are generally thinner.
Steel plates: Cold-rolled plates are generally thinner, such as plates for automobiles; there are more hot-rolled medium and thick plates, and there are similar thicknesses to cold-rolled ones, and the appearance is obviously different.
Angle steel: All hot-rolled.
Steel pipes: both welded hot-rolled and cold-drawn.
Channel steel and H-beam: hot-rolled.
Rebar: hot-rolled.
Contact us to get a customized solution for your project.
Email:gi@gneesteel.com
Whatsapp/Wechat：+86 15824687445
