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What is the difference between hot rolled steel and cold rolled steel?

May. 07, 2020

Each metal has its own advantages and uses. For example, some types of steel are very suitable for household appliances, while other types of steel are suitable for the automobile or shipbuilding industry, gas tanks, and construction.


In addition, material grades with the same chemical composition may have different qualities depending on the manufacturing method. Hot rolled steel and cold rolled steel are examples. So, how to choose hot rolled steel or cold rolled steel?


Hot Rolled Steel Coil

Hot working is more widely used because it requires less energy, and is usually used for compression molding, such as rolling, extrusion, forging, etc. Hot rolling occurs at a temperature higher than the material recrystallization temperature, raises the temperature of the slab above 1000 ° C, and then sends it to the rolling machinery. Continuous rolling can obtain the required metal sheet (3 mm and above) or profile.


Compared with cold-rolled steel, hot-rolled steel can be produced in large quantities, and its market price remains at a low level. After the steel is cooled at room temperature, it changes the microstructure of the material, thereby increasing ductility and toughness.


However, hot-rolled steel shrinks slightly during cooling, subjecting the metal to internal stresses, resulting in uneven and distorted dimensional measurements. The dimensional tolerance of the material can vary between 2-5%. Hot rolled steel has a scaly surface, which is an oxide formed at high temperature, so it is easy to identify the hot rolled product by touching the surface.


Hot rolled steel use


When the requirements for accuracy are not high, hot rolled steel is a good choice, and its huge advantage in price is more important than accuracy. Some common uses of hot rolled steel are: building construction, pipes, truck frames, doors and shelves, rails, tram parts, etc.


Cold Rolled Steel Coil

Cold working is a metal forming method that has many advantages over hot working. Technically speaking, cold working includes cold rolling and cold drawing. The former is used for sheet metal manufacturing, and the latter can be used for rectangular and round reinforcement.


In contrast to hot rolling, the metal temperature during cold rolling is lower than its recrystallization temperature. If low-carbon steel is used, the metal can be rolled to a thickness of 0.5-3 mm; if stainless steel is used, the metal can be rolled to a thickness of 0.5-5 mm. During the rolling process, oil is used to cool the material, which also acts as a lubricant. If there is no oil film, the material will wear and deform. Therefore, cold-rolled steel can be identified by its oily and smooth surface.


The main advantages of cold working are: accurate finished size, smooth surface, and higher strength performance.


Cold rolled steel use


Although cold-rolled steel is more expensive than hot-rolled steel, the above advantages make it useful in many scenarios. Since the surface is already smooth enough, the finished product does not require a large amount of additional surface finishing. Cold rolled / cold drawn steel uses include: metal furniture, structural parts, household appliances, water heaters, metal containers, fan blades, pans, computer cabinets, etc.


About HGB Industrial Group

HGB Industrial Group is an enterprise company, including (Hongkong) HGB Company Limited, and cooperating with Tangshan Shuixin Steelrolling Company Limited. Supplying products worldwide and make business easier is always our pursuit.


As a steel rolling mill, Shuixin Steelrolling mainly produce and export Steel Strip Coils, with width from 30mm to 900mm, and thickness from 0.12mm to 4.0mm, annual output about 1,000,000 metric tons.

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