The main difference: hot rolling is rolling above the recrystallization temperature, cold rolling is rolling below the recrystallization temperature; cold rolling sometimes has heating, but the temperature is relatively low, because after cold rolling will be processed Hard, if the molding requirements for the material are relatively high, annealing is also required.
Cold rolling and hot rolling are generally sheets or profiles, while cold drawing is generally a cylindrical section of wire. In addition, the hot-rolled sheet is generally a steel with a high alloy content and high strength, while the cold-rolled steel is a low-carbon low-alloy steel, which can be used to improve the strength and ensure the surface quality of the material by cold rolling.
Cold drawn (rolled) tubes are divided into two types: round tubes and shaped tubes:
Cold drawn steel tube generally need to be drawn multiple times, and there must be corresponding stress relief annealing between each drawing to ensure the next cold drawing smoothly. From the outside, cold-rolled seamless steel pipes are often small-diameter, and hot-rolled seamless steel pipes are often large-diameter. The accuracy of cold-rolled seamless steel tubes is higher than that of hot-rolled seamless steel tubes, and the price is also higher than that of hot-rolled seamless steel tubes. Cold drawn seamless pipes generally have a small caliber, mostly below 127 mm. Especially the outer diameter of the cold drawn seamless pipe is very high, and the length of the cold drawn seamless pipe is generally shorter than that of the hot rolled seamless pipe. In terms of wall thickness, cold drawn seamless tubes are more uniform than hot rolled seamless tubes.
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