I. Processing Temperature
- Hot Rolling : It is the rolling process carried out above the recrystallization temperature. The recrystallization temperature refers to the temperature at which the deformed microstructure of a metal is recovered and recrystallized through heating during plastic deformation. For example, the recrystallization temperature of carbon - steel structural steel is generally around 700 - 800℃. During hot rolling, the metal billet is rolled by the rolls at a high temperature, and its temperature is usually high, which makes the metal have good plasticity and can easily achieve a large deformation.
- Cold Rolling : It is the rolling process carried out below the recrystallization temperature. For example, rolling steel after hot rolling at room temperature is cold rolling. Since it is processed at a lower temperature, the plasticity of the metal is relatively poor. Therefore, in the cold rolling process, the deformation per pass is relatively small, and more passes are needed to achieve the required thickness or shape.
II. Product Performance Differences
- Mechanical Properties
- Hot - rolled Products : During hot rolling, metal undergoes recrystallization, which refines the metal grains and eliminates the effects of work hardening. Its products have good plasticity and toughness. For example, hot - rolled steel plates are not easy to break when subjected to bending, stretching and other deformations. However, the strength of hot - rolled products is relatively low because the grains after recrystallization are relatively large and there are fewer grain boundaries. Grain boundaries play a role in hindering the movement of dislocations in metal materials, thus affecting the strength of materials.
- Cold - rolled Products : After cold rolling, metal will produce work hardening. The metal lattice is distorted and the dislocation density increases, which significantly improves the strength of the material. For example, the yield strength and tensile strength of cold - rolled thin steel plates are obviously increased. However, the plasticity of cold - rolled products is reduced because work hardening makes the material more likely to break when further deformed.
- Surface Quality
- Hot - rolled Products : During hot rolling, due to the high temperature, the surface of the metal is easy to produce oxide scale. These oxide scales may partially fall off, resulting in a relatively rough surface of hot - rolled products. Moreover, in the hot rolling process, the cooling speed is relatively slow, and the surface quality of the products is difficult to control, and some surface defects such as pits and depressions may occur.
- Cold - rolled Products : There is no high - temperature oxidation problem during cold rolling. Through reasonable rolling and subsequent surface treatment processes, cold - rolled products can obtain a good surface finish. For example, the surface of cold - rolled metal strips is smooth and flat, like a mirror, which can meet the requirements of some applications with high surface quality requirements, such as household appliance shells and automotive panels.
III. Production Cost and Application Fields
- Production Cost
- Hot Rolling : The equipment for hot rolling is relatively simple, mainly heating furnaces and rolling mills. Because it is processed at high temperature, the energy consumption is large. It is mainly used for producing some products with not high requirements for dimensional accuracy and surface quality, such as steel sections and steel plates. Its production efficiency is high, and the unit production cost is relatively low.
- Cold Rolling : The equipment for cold rolling is more complex, and it needs high - precision rolling mills and supporting leveling, annealing and other equipment. Moreover, in the cold rolling process, the metal needs to be rolled and intermediate annealed many times to eliminate work hardening, and both energy consumption and equipment investment are large. However, cold - rolled products have high added value and are mainly used for producing some products with high requirements for dimensional accuracy and surface quality, such as precision strips for electronic equipment and high - quality metal plates.
- Application Fields
- Hot - rolled Products : They are widely used in building structures (such as I - beams and channels for building frames), shipbuilding (large steel plates for hulls), and bridge construction (hot - rolled steel sections for piers and bridge bodies). In these fields, the requirements for the plasticity and toughness of materials are high, while the requirements for surface quality and dimensional accuracy are relatively low.
- Cold - rolled Products : They are mainly used in automobile manufacturing (body panels, stamping parts), household appliance manufacturing (refrigerator and washing machine shells), and mechanical manufacturing (high - precision shafts, gear blank parts). These fields have strict requirements for the strength, surface quality and dimensional accuracy of materials.
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Company Name: Jiangsu Huiyu Alloys Technology Co., Ltd.
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Country: China
Website: https://www.huiyualloys.com/
