Do You Know the Hot Rolling Process?

Ⅰ. About the hot rolling process

The hot rolling process is a metalworking process in which the metal is heated above the recrystallization temperature, causing it to plastically deform during the processing or rolling operation. This process is used to create shapes with desired geometric dimensions and material properties, while maintaining the same metallic volume. The hot metal is passed between two rolls to flatten it, elongate it, reduce the cross-sectional area and obtain a uniform thickness. Hot rolled steel is the most common product in the hot rolling process and is widely used in the metal industry as a final product or raw material for subsequent operations.

Metal rolling beyond the recrystallization temperature is called hot rolling. The temperature at which new grains form in the metal is called the recrystallization temperature. This temperature cannot be too high; otherwise the metal will burn and become unfit for use. It consists of heating the ingot to about 1200°C in a soaking pit. The hot ingot then passes through the gap between the rolls in multiple stages to obtain flattening. The gap between the rolls is adjusted to match the desired thickness of the rolled product. The blooms are rolled into billets, which are rolled into desired cross-sections such as flat, square, rectangular, hexagonal, angle, I, U, etc. In the area where the rollers and metal come into contact, the bite angle is usually 40°. The rollers apply compressive stress while squeezing the metal. These lead to grain changes, grain breakage and lattice distortion.

During the hot rolling process, coarse grains are converted into smaller grains. Care has been taken to maintain the correct temperature range during this process. During this process, the velocity of the emerging metal is higher due to elongation. Rolling is generally a hot working process unless cold rolling is specifically mentioned. This is the fastest way to convert large sections into smaller stocks. Through the hot rolling process, we can produce bars, plates, plates, rails, angles, structural profiles, I, L, T, C, profiles, etc. Commonly hot rolled materials are steel, copper, magnesium, aluminum and their alloys. The surface of all hot rolled steel is reddish blue.

Ⅱ. The advantages of hot rolling process

1. The mechanical properties of the hot rolling process are improved: the mechanical properties such as toughness, impact resistance, ductility and elongation are improved.

2. Grain structure refinement: The grain structure of the metal is refined, that is, the coarse grains are converted into fine grains, thereby changing the properties of the metal.

3. Elimination of pores: The pores of the metal are eliminated, resulting in a strong and uniform structure.

4. Even distribution of impurities: impurities such as slag are evenly distributed throughout the metal. Otherwise, they are concentrated in one spot inside the metal, weakening the metal at that spot.

5. Low pressure is required: due to the high temperature of the rolled metal, the metal is easily deformed. This reduces pressure requirements.