Hot and cold rolling are processes used to form steel sheets or profiles and have a significant impact on the structure and performance of steel.
Hot rolling is the main method for rolling steel, while cold rolling is generally only employed for producing steel with precise sizes, such as small section steel and thin plates.
Wire machine
The diameter of 5.5-40mm, coil, is all hot rolled material.
After cold drawing, it is a cold drawing material.
steel rod
Generally hot-rolled, in addition to fine and bright materials with precise size, it also has forged materials (the surface has forging marks).
steel strip
Both hot-rolled and cold-rolled materials are generally thinner.
Steel sheet
Cold-rolled sheets are generally thinner, like automobile license plates;
Medium thickness hot rolled sheet, has similar thickness to cold rolled, the appearance is obviously different.
steel angle
Everything is hot rolled.
Steel tube
Including hot rolled welding and cold drawing.
U steel and H steel
Hot rolled.
Rebar
Hot rolled.
Definition of Hot Rolled
Appearance and surface quality
As cold rolled sheet is obtained after cold rolling process and cold rolling also provides better surface finish, cold rolled sheet has better surface quality (such as surface roughness) than hot rolled sheet.
Thus, if the finished product requires high coating quality, a cold plate is generally preferred.
Furthermore, hot-rolled sheet is divided into pickled and non-pickled sheet.
The surface of pickling board generally has a normal metallic color due to acid washing, but it is not cold rolled.
The pickling plate generally has a dark-colored oxide layer or a trioxide layer.
In simple terms, it is like roasting over a fire and will usually rust if not kept in good environmental conditions.
Performance
In general, the mechanical properties of hot-rolled sheets and cold-rolled sheets are considered similar in engineering, although cold-rolled sheets undergo a hardening process during cold rolling.
However, if rigorous mechanical performance is required, the plates need to be treated differently.
The yield strength of the cold plate is generally slightly higher than that of the hot plate, and the surface hardness is also higher, depending on the degree of annealing of the cold plate.
However, the annealed strength of cold-rolled sheet is still higher than that of hot-rolled sheet.
Formability
Since the performance of cold-rolled and hot-rolled sheets is similar, the factor influencing the forming performance depends on the difference in surface quality.
Because the surface quality of cold-rolled sheets is generally better than steel sheets of the same material, the forming effect of cold-rolled sheets is better than that of hot sheets.
