Hot rolling is relative to cold rolling. Cold rolling is rolling below the recrystallization temperature, while hot rolling is rolling above the crystallization temperature. So, what is hot rolling? What is the production process and use of hot rolled stainless steel plates? Let's learn about it together!
Hot rolling is a metal processing process that refers to heating metal materials to a temperature higher than their recrystallization temperature (usually between 900°C and 1300°C), and then compressing and stretching them into the desired shape and thickness through rollers. The recrystallization temperature is a key parameter of metal materials. When the temperature exceeds the recrystallization temperature, the grains in the material will rearrange and become more uniform and fine, making it less likely for the material to break and stress concentrate during plastic deformation.
The hot rolling process can process a variety of metal materials. The most common applications include the production of steel plates, steel bars, steel pipes, etc. For stainless steel, hot rolling can not only improve its physical properties, but also improve its surface quality, thus laying the foundation for the subsequent cold rolling process.
During the hot rolling process, the metal billet is usually heated by a high-temperature heating furnace, and then enters the roughing mill and finishing mill for a series of rolling operations. This process will produce a large extension and deformation, so that the internal structure of the metal is reorganized, the grains are refined, and the mechanical properties of the material are improved.
High production efficiency：
Because hot rolling can process metal at high temperature, the plasticity of the material is good and can be greatly deformed in a short time. Therefore, hot rolling has high production efficiency and is suitable for large-scale industrial production.
Can process metals of large size and thickness：
The hot rolling process can process thicker metal billets, so that it can obtain thicker plates or other products after multiple rolling passes.
Uniform deformation of materials：
Hot rolling can eliminate the internal stress in metal materials through high temperature and avoid material fracture caused by stress concentration during cold rolling. During the recrystallization process, the material grains are rearranged to obtain a more uniform material structure.
Improved mechanical properties：
Because the internal grains of the material are refined during the hot rolling process, its mechanical properties are significantly improved. Specifically, the toughness of the material is increased, the tensile strength is improved, and the fatigue life is extended.
Reduced energy consumption：
The energy consumption of hot rolling is relatively low because it is carried out at high temperature. Compared with cold rolling, hot rolling requires less energy consumption.
The process of producing hot-rolled stainless steel plate can be divided into several main stages, from the initial heating of the metal, rolling to the final surface treatment, each step requires strict control and operation to ensure the quality of the product.
1. Billet preparation
The raw material of hot-rolled stainless steel plate is usually cast billet or slab. The preparation of the billet includes its cleaning treatment, removing the oxide scale or other impurities on the surface.
2. Heating
The billet is fed into a high-temperature heating furnace, and the temperature in the furnace is usually between 1100℃ and 1250℃. The purpose of heating is to improve the plasticity of the billet so that it can produce large deformation without cracking or breaking during the subsequent rolling process. The heating time is closely related to the size and material of the billet, and temperature control is crucial to avoid overheating and causing the material to be too soft or oxidized.
3. Rough rolling
After the billet is heated, it is fed into the rough rolling mill for preliminary rolling. The main purpose of rough rolling is to greatly compress the billet from the initial thickness to a rough processing size close to the final thickness. During the rolling process, the internal structure of the metal material gradually changes, the grains are compressed and extended, and the stress is evenly distributed.
4. Finishing
The finishing process usually includes multiple rolling passes, each of which further compresses the thickness of the material to achieve the desired size requirements. During the finishing stage, the control of temperature and pressure is particularly important to ensure the uniformity of the thickness and mechanical properties of the material.
5. Cooling and finishing
After finishing, the hot-rolled stainless steel plate will undergo a series of cooling operations to gradually reduce its temperature. The speed and method of cooling have a direct impact on the performance of the final material. In some cases, the hot-rolled stainless steel plate may also undergo subsequent straightening and cutting operations to obtain a flat, standard size.
6. Surface treatment
The surface of the hot-rolled stainless steel plate usually has an oxide scale. After surface treatment such as pickling or shot peening, the oxide layer can be removed and the surface quality can be improved. In some cases, further surface treatment such as polishing and coating will be performed according to customer needs.
Structural steel: general structural steel and welded structural steel are produced, mainly used in the production of steel structures, bridges, ships, and vehicles.
Weathering steel: special elements (P, Cu, C, etc.) are added, which has good corrosion resistance and atmospheric corrosion resistance. It is used in the production of containers, special vehicles, and building structures.
Automobile structural steel: high-strength steel plates with good DRAWING performance and welding performance are used in the production of automobiles.
Steel plates for steel pipes: with good processing performance and compressive strength, they are used to produce high-pressure gas pressure vessels with a volume of less than 500 filled with LPG, acetylene gas and various gases.
Steel plates for high-pressure vessels: with good processing performance and compressive strength, they are used to produce high-pressure gas pressure vessels filled with LPG, acetylene gas and various gases.
Stainless steel plates: stainless steel has good corrosion resistance and is mainly used in the food industry, surgical equipment, aerospace, petroleum, chemical industry and other industries.
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