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What Is The Difference Between Cold Rolled Steel And Hot Rolled Steel?

Oct. 18, 2019

In the daily life of automotive manufacturing, electrical products, rolling stock, aviation, precision instruments and mechanical parts and other products need to use cold-rolled steel or hot-rolled steel, then what is the difference between the two? As a Cold Rolled Steel Sheet Supplier, we will answer from a professional perspective.


First we need to know the characteristics of cold rolled steel and hot rolled steel:


Hot-rolled steel sheets By definition, steel ingots or billets are difficult to deform at normal temperature and are difficult to process. Generally, they are heated to 1100 to 1250°C for rolling. This rolling process is called hot rolling. The hot rolled sheet has a high temperature, so the deformation resistance is small, and a large amount of deformation can be achieved. Taking the rolling of the steel sheet as an example, the thickness of the continuous casting blank is about 230 mm, and after rough rolling and finish rolling, the final thickness is 1 to 20 mm. At the same time, due to the small width-to-thickness ratio of the steel plate, the dimensional accuracy requirement is relatively low, and the shape problem is not easy to occur, and the convexity is mainly controlled. For the requirements of the organization, it is generally achieved by controlled rolling and controlled cooling, that is, controlling the rolling temperature, finish rolling temperature and crimping temperature of the finishing rolling to control the microstructure and mechanical properties of the strip. Hot-rolled steel plate has low hardness, easy processing, good ductility, poor surface quality (low oxidation and smooth finish), but good plasticity, generally medium and heavy plate, mechanical properties are far less than cold processing, and secondarily forging processing, but better Resilience and ductility.


Cold Rolled Steel Sheet: high strength, high hardness, high surface finish, generally thin sheet, can be used as a stamping sheet, cold rolling is made by hot-rolled coil as raw material, and rolled at normal temperature below recrystallization temperature, cold rolling The steel plate is a steel plate produced through a cold rolling process, referred to as a cold plate. The thickness of the cold-rolled sheet is generally between 0.1 and 8.0 mm. The thickness of the cold-rolled steel sheet produced by most factories is 4.5 mm or less. The thickness and width of the cold-rolled sheet are determined according to the equipment capacity and market demand of each factory. Cold-rolled steel sheet has a certain degree of work hardening and low toughness, but can achieve a good yield ratio, used for cold-bending spring pieces and other parts, and because the yield point is closer to the tensile strength, there is no danger during use. Predictability, an accident is likely to occur when the load exceeds the allowable load.


Cold Rolled Steel Sheet


Cold Rolled Steel Sheet


The following will explain the difference between them.


1. cold-rolled steel allows partial buckling of the section, so that the bearing capacity of the bar after buckling can be fully utilized; and the hot-rolled steel does not allow local buckling of the section.

2. the residual stress of hot-rolled steel and cold-rolled steel is different, so the distribution on the cross-section is also very different; the residual stress distribution on the section of cold-formed thin-walled steel is curved, and the section of hot-striped steel or welded steel The upper residual stress distribution is a film type.


3. the free torsional stiffness of hot-rolled steel is higher than that of cold-rolled steel, so the torsional performance of hot-rolled steel is better than that of cold-rolled steel. Hot-rolling and cold-rolling are the processes of forming steel or profiles, and their microstructure and Performance has a big impact.


4. the surface of the cold-rolled plate has a certain degree of gloss. The hand is indeed smooth to the touch, similar to the very common steel cup for drinking water; if the hot-rolled sheet is not pickled, it has many ordinary steel plates on the market. The surface is similar, the surface with rust is red, and the surface without rust is purple-black (iron oxide scale).


5. The hot-rolled sheet has low hardness, easy processing and good ductility; the cold-rolled sheet has high hardness and is relatively difficult to process, but it is not easily deformed and has high strength.


6. The strength of hot-rolled sheet is relatively low, the surface quality is almost poor (having low oxidation and smoothness), but the plasticity is good, generally medium and thick plate; the cold-rolled sheet has high strength, high hardness and high surface finish, generally thin sheet, which can be used as stamping. Use the board.


7. The mechanical properties of hot-rolled steel sheets are far less than cold processing, and secondly to forging processing, but have good toughness and ductility; cold-rolled steel sheets have a certain degree of work hardening and low toughness, but can achieve better yield ratio. It is used to cold-bend spring parts and other parts. At the same time, because the yield point is closer to the tensile strength, the danger is not predictable during use, and accidents are likely to occur when the load exceeds the allowable load.


The above is about the difference between cold-rolled steel and hot-rolled steel, and I hope to help everyone. If you are interested in cold-rolled steel or hot-rolled steel, you can contact us. In addition to cold-rolled steel or hot-rolled steel, we also have Cold Rolled Steel Coil and hot-rolled steel coils. Welcome to come.

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