Cold bending is a metalworking process in which metal sheets and strips are mechanically bent at room temperature to form profiles of specific shapes and dimensions. The resulting products are known as cold-bent profiles. The advantages of cold bending include: it enables the production of a wide range of ultra-thin, ultra-wide, and complex shapes that cannot be achieved through rolling; it helps conserve metal materials; and the finished products exhibit excellent mechanical properties.

Metal forming methods used to bend metal sheets and strips into shaped materials (or components) and welded pipe tubes at room temperature—see roll forming. Since continuous roll bending produces high volumes of profiled sections and welded pipe tubes, the term "cold bending deformation" in a narrower sense refers specifically to this type of bending process.

An open report on cold-formed sections dates back to 1855, when riveted I-beams were first used in the construction of office buildings in New York. By 1910, the U.S. had developed continuous roll-forming equipment, after which the production of cold-formed sections experienced significant growth. Compared to hot-rolled steel, cold-formed steel offers greater dimensional accuracy, smoother surface finishes, and the ability to produce complex cross-sectional shapes that cannot be achieved through hot rolling. Additionally, it provides superior bending and torsional resistance at the same weight. As a result, using cold-formed sections can lead to material savings of more than 30%. Moreover, the manufacturing process is straightforward, requiring relatively low capital investment in equipment. Consequently, the production of cold-formed sections has continued to advance steadily. Typically, in countries with advanced steel industries, cold-formed steel accounts for 2% to 4% of total rolled products—though in some cases, this figure can reach as high as 5%.

It can be categorized into three types: the single-sheet production mode, where individual sheets are bent into single-profile shapes; the coil-based production mode, which uses continuous strips of coiled steel as raw material to manufacture profiles; and the continuous production mode, where coils are used as input and the ends are butt-welded together for uninterrupted manufacturing. Among these, the continuous production mode has seen greater development due to its superior dimensional accuracy and higher productivity. A typical setup and arrangement of equipment for continuous cold-formed steel profiles are illustrated in Figure 3. Regardless of the production method chosen, the entire process is divided into three main stages: raw material preparation, forming, and finishing.

The typical process flow for open-type cold-formed profiles is as follows:

Steel coil → Slitting → Feeding → Uncoiling → Straightening → Head Cutting → Butt Welding → Material Storage → Forming → Straightening → Cutting → Inspection & Collection → Packaging → Weighing → Warehousing.

The process flow for closed-type cold-formed steel is as follows: Steel coil → Longitudinal shearing → Feeding → Uncoiling → Straightening → Head cutting → Butt welding → Material storage in an accumulator → Forming → High-frequency welding → Deburring → Cooling → Straightening → Cutting → Inspection and collection → Packaging → Weighing → Warehousing.

By adding auxiliary processes such as punching, creasing, and torsional bending to the production line, it becomes possible to manufacture a wide range of custom-shaped cold-formed profiles.