Hard Cold Rolled Coil

Hard Cold Rolled Coil, refers to the continuous rolling of hot rolled pickled coils at normal temperature,usually made of hot-rolled steel coils after cold-rolling process. Compared with normal cold rolled coils, cold rolled hard coils have higher hardness and surface quality.

Main Features：
The main feature is the use of greater pressure in the cold rolling process, as well as a greater number of cold rolling, resulting in a more uniform thickness of the coil and the formation of a hard oxide skin on the surface.
Cold Rolled Hard Coil is typically used in applications requiring high hardness and strength, such as automotive manufacturing, appliance manufacturing, electronic equipment, and metal containers. Its high surface quality and uniform thickness make Cold Rolled Hard Coil suitable for the production of products requiring high precision and quality.

Main Advantages ：
1. It is suitable for extremely thin strips that cannot be produced by hot rolling (the thinnest can be less than 0.001mm).
2. The surface quality of cold-rolled products is superior, and there are no defects such as pits and Suppression of iron oxide scale and other defects. According to the requirements of users, coils with different surface roughness (smooth surface or hemp rough surface, etc.) can be produced to facilitate the processing of the next process.
3. The mechanical and technological properties of cold-rolled hard coil are very good (such as high strength, low yield limit, good weight deep drawing performance, etc.).
4. It can realize high-speed rolling and full continuous rolling with high productivity.

Main Applications
The galvanizing unit with pre-annealing processing device processes galvanizing;
After annealing, it is processed into ordinary cold rolling; there is basically no need to process the panel.
Others: supermarket shelves, pipe making, filing cabinets, lamps, daily hardware and other industries;
In the stationery manufacturing industry, a small part uses full rigid board, that is, cold rolled hard coil;
The umbrella industry generally uses hard rolls with a specification of 0.2-0.5mm to make umbrella ribs.

Cold-rolled hard coil is a common metal product, and its national standards can vary from country to country. The following are some representative Chinese, British, American and Japanese national standards for hard cold rolled coil:

Chinese standard: 

My country's national standard for cold-rolled steel sheets is GB/T708--1988

Which specifies the technical requirements, dimensional tolerances, and surface quality of cold-rolled steel sheets.

British Standard:

BS EN 10130:2006. This standard specifies the technical delivery conditions for cold-rolled mild steel flat products intended for cold forming.

American Standard: 

ASTM A1008/A1008M-21. This standard specifies the standard specifications for cold-rolled carbon structural steel sheets, including various cold-rolled steel sheets including cold-rolled hard coils.

Japanese standard: 

JIS G 3141:2017. This standard specifies the technical delivery conditions for cold-rolled carbon steel sheets and strips.
These standards specify requirements such as chemical composition, mechanical properties, dimensions and allowable deviations of cold-rolled hard coils to ensure their quality and performance in specific applications.

Hard Cold Rolled Coil have good properties, and cold-rolled strips and steel plates with thinner thickness and higher precision can be obtained through cold rolling. High flatness, high surface finish, clean and bright cold-rolled sheet surface. It is easy to paint and process, and has the characteristics of high stamping performance and low yield point.

Therefore, cold-rolled hard coils are widely used, mainly in automobiles, building materials and other fields. It is also the substrate for the production of galvanized steel coils and galvanized steel coils.

The inner diameter of cold-rolled hard steel coil is 508mm or 420mm, and the weight is not more than 15.1 tons (actual weight or theoretical weight).
When the thickness is 0.30-0.80mm, the allowable thickness deviation is specified in Q/BQB 401--94 PT.B (advanced) precision;
When the thickness is 0.18-0.30mm, the thickness allowable deviation is ±10%.