Difference between Q235 hot rolled steel plate and cold rolled steel plate
1. Hot rolled plate has low hardness, easy processing and good ductility.
Cold rolled sheet has high hardness and relatively difficult processing, but it is not easy to deform and has high strength.
2. Hot rolled plate has relatively low strength and poor surface quality (low oxidation finish), but good plasticity. It is generally medium thick plate.
Cold rolled sheet: it has high strength, high hardness and high surface finish. It is generally thin plate, which can be used as stamping plate.
3. The mechanical properties of hot-rolled steel plate are far inferior to cold working and forging, but it has good toughness and ductility.
Cold rolled steel plate has a certain degree of work hardening and low toughness, but can achieve a good yield strength ratio. It is used for cold bending spring leaf and other parts. At the same time, because the yield point is close to the tensile strength, the danger is not foreseen in the use process, and accidents are easy to occur when the load exceeds the allowable load.
4. Hot rolling is to roll the steel plate into a relatively thin steel plate at a higher temperature;
Cold rolling is the rolling of steel plates at room temperature.
5. Generally, hot rolling is carried out before cold rolling. When the steel plate is thick, it can only be hot rolled. After rolling into a thinner plate, it can be cold rolled.
6. Hot rolled steel plates are divided into thick plate (thickness greater than 4mm) and thin plate (thickness 0.35~4mm); There is only one kind of cold rolled steel sheet (0.2 ~ 4mm thick).
7. The termination temperature of hot rolling is generally 800 ~ 900 ℃, and then it is generally cooled in air, so the hot rolling state is equivalent to normalizing treatment. The metal materials delivered in hot rolling state have certain corrosion resistance because their surfaces are covered with a layer of oxide film. The requirements for storage, transportation and storage are not as strict as those for materials delivered in cold drawing (rolling). For example, large and medium-sized section steels and medium thick steel plates can be stored in the open freight yard or covered.
8. Compared with the hot rolling state, the cold rolling state has higher dimensional accuracy, better surface quality, lower surface roughness and higher mechanical properties. However, it is easy to be corroded or rusted, and its packaging, storage and transportation have strict requirements. It needs to be kept in the warehouse, and attention should be paid to the temperature and humidity control in the warehouse.