The difference between Q235 hot-rolled steel plate and cold-rolled steel plate

 The difference between Q235 hot-rolled steel plate and cold-rolled steel plate

        The hot-rolled sheet has low hardness, easy processing and good ductility. Cold-rolled sheet has high hardness and is relatively difficult to process, but it is not easy to deform and has high strength. The strength of the hot-rolled sheet is relatively low, and the surface quality is poor (with low oxidation finish), but the plasticity is good, and it is generally a medium-thick plate. The cold-rolled sheet: high strength, high hardness, and high surface finish. .

     The mechanical properties of hot-rolled steel sheets are far inferior to those of cold-worked and forged, but they have better toughness and ductility. Due to a certain degree of work hardening, the cold-rolled steel plate has low toughness, but it can achieve a better yield ratio, and is used to cold-bend parts such as spring sheets. At the same time, because the yield point is closer to the tensile strength, there is no risk of danger during use. Predictability, prone to accidents when the load exceeds the allowable load. Hot rolling is to roll the steel plate into a relatively thinner steel plate at a higher temperature; cold rolling is to roll the steel plate at room temperature. Generally, hot rolling is carried out first, and then cold rolling is carried out. When the steel plate is thicker, only hot rolling can be used, and after rolling into a thinner plate, cold rolling is carried out.

       Hot-rolled steel plates are divided into two types: thick plates (thickness greater than 4mm) and thin plates (thickness 0.35-4mm); cold-rolled steel plates are only thin plates (thickness 0.2-4mm). The termination temperature of hot rolling is generally 800-900°C, and then it is generally cooled in the air, so the hot rolling state is equivalent to normalizing treatment. The metal materials delivered in the hot-rolled state have a certain corrosion resistance because the surface is covered with an oxide film, and the requirements for storage, transportation and storage are not as strict as those delivered by cold drawing (rolling), such as large and medium-sized steel, Medium and thick steel plates can be stored in the open yard or after being covered with thatch. Compared with the hot-rolled state, the metal material in the cold-rolled state has high dimensional accuracy, good surface quality, low 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.