Three differences between Cold Rolled and hot rolled processes
The difference between cold rolled and hot rolled is mainly the temperature of the rolling process. "Cold" is normal temperature, "Hot" is high temperature.
From the perspective of metallurgy, the boundary between cold rolled and hot rolled should be distinguished by recrystallization temperature. That is, rolling below the recrystallization temperature is cold rolled, and rolling above the recrystallization temperature is hot rolled. The recrystallization temperature of steel is 450-600°C.
1. Appearance and surface quality: Since the cold plate is obtained after the cold rolled process of the hot plate, and the cold rolled will also perform some surface finishing, the cold plate has a specific heat on the surface quality (such as surface roughness) The board comes well, so if there is a high requirement for the coating quality of the subsequent painting of the product, the cold board is generally selected. In addition, the hot plate is divided into pickled and unpickled plates. The surface of the pickled plate becomes normal metal color after pickling, but it is not cold rolled, so the surface is still not as high as the cold plate. The oxide layer is black. In layman's terms, it looks like it has been roasted on fire, and if the storage environment is not good, it will usually be rusty. 2. Performance: In general, the mechanical properties of hot plate and cold plate are considered to be indistinguishable in the project, although the cold plate has a certain work hardening during the cold rolling process, (however, the strict requirements on mechanical performance are not excluded , It needs to be treated differently), the cold plate usually has a slightly higher yield strength than the hot plate, and the surface hardness is also higher, depending on the degree of annealing of the cold plate. But no matter how the annealing cold plate strength is higher than the hot plate. 3. Formability Because the performance of cold and hot plates is basically not too bad, the influencing factors of formability depend on the difference in surface quality. Since the surface quality is better from cold plates, usually speaking, steel plates of the same material The forming effect of cold plate is better than that of hot plate.
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