Steel is widely used in the manufacturing and construction industries. Among the various types of steel, hot rolled steel and cold rolled steel are two basic categories that determine the characteristics and performance of the material. Understanding the difference between hot rolled steel and cold rolled steel is essential for choosing the right material. Next, we will take a closer look at the difference between hot rolled steel and cold rolled steel to help us better choose the right steel.
What Is Hot Rolled Steel?
Hot rolled steel is a type of steel formed by processing at high temperatures, usually at temperatures above 1,700°F (927°C). Due to the high temperature, the steel is easier to form in a plastic state and can produce large-sized metal plates, bars, tubes and other products.
What Is Cold Rolled Steel?
Cold rolled steel is a type of steel formed by processing at or near room temperature. It is usually further rolled on the basis of hot rolled steel to improve its dimensional accuracy, surface quality and mechanical properties.
What Is The Difference Between Hot Rolled Steel And Cold Rolled Steel?
1. Production process:
Hot rolled steel: The billet or ingot is heated to the required temperature. After heating, the steel is fed into a series of rollers to reduce the thickness and shape it into the desired shape through multiple rolling. After rolling, the steel is cooled at room temperature, and the natural shrinkage during cooling may cause slight changes in size and shape.
Cold rolled steel: The production process of cold rolled steel includes pickling, cold rolling, annealing and leveling. First, the hot rolled steel coil is pickled to remove the oxide scale and impurities on the surface. Subsequently, the steel is compressed by rollers at room temperature to make it thinner and increase its strength. Next, it is annealed to improve the ductility and processing properties of the steel, and finally leveled to ensure that the steel has excellent surface finish and straightness.
2. Surface quality:
Since hot rolled steel is formed at high temperature, the surface is usually rough and may have oxide scale and tiny defects. Its edge and dimensional tolerances are relatively large, so further processing is required to obtain a smoother surface.
Cold-rolled steel is finely processed, with a smooth surface, high brightness and good aesthetics. This makes cold-rolled steel suitable for applications that require good appearance or precision processing, such as automobile manufacturing, home appliance housings, etc.
3. Mechanical properties:
Due to the characteristics of its production process, hot-rolled steel has good toughness and ductility and is suitable for structural applications. However, due to the internal stress that may be generated during the cooling process, the dimensional stability of the material is poor and deformation may occur during subsequent use.
Due to work hardening, cold-rolled steel has higher strength and hardness, but lower plasticity. If further processing (such as bending, stamping) is required, annealing is usually required to restore some ductility.
4. Application areas:
Due to its low cost and easy processing, hot-rolled steel is widely used in building structures, bridges, shipbuilding, railway tracks, large pipelines and other fields.
Due to its high dimensional accuracy and smooth surface, cold-rolled steel is suitable for manufacturing automobile bodies, home appliances, precision machinery parts and other fields.
5. Price and cost:
Hot-rolled steel has a lower production cost because its manufacturing process is simpler and does not require additional surface treatment and precise dimensional control. Cold-rolled steel has a higher cost because it requires additional processing steps such as pickling, annealing and leveling.
How To Choose?
Hot-rolled steel and cold-rolled steel each have their own advantages and disadvantages. The choice of which material should be based on specific usage requirements. If the project has high requirements for the dimensional accuracy and surface quality of the steel, cold-rolled steel is a better choice; if you are concerned about cost and do not need a particularly smooth surface, hot-rolled steel is more economical and practical.
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