Steel and other metals can be shaped using a number of methods. Cold bending is one of the most frequently employed means of shaping steel into many different configurations.
Cold Bending Process
The process of cold bending steel is actually performed at what is considered room temperature. It is referred to as cold bending to differentiate the process from hot bending in which steel is heated by a torch or furnace before shaping. This process is generally performed using rollers to press a piece of steel against metal shaping tools called dies. It may also be referred to as cold rolling or pyramid rolling.
Benefits of Cold Bending
Cold bending does not require the use of fuel to heat the steel before processing, and the additional time and effort of heating and then cooling the steel are eliminated. Cold rolling results in a smoother, more finished surface and generally causes less deformation of the item being processed. One additional benefit is the increased strength imparted by working the steel while cold. When steel is manufactured at high heat and then allowed to cool it develops an internal crystalline arrangement. Working steel at ambient temperatures below the point of crystallization has been shown to enhance strength at a molecular level by compressing and distorting the crystalline structure. As the molecules become compacted they are unable to move as easily and, therefore, the steel becomes stronger. Working steel at high heat above the point of crystallization means that crystallization will occur after the steel has been worked and therefore the steel will not be any stronger than unworked steel. Heating steel that has already been cold bent or rolled will cause the material to lose the extra strengthening gained from the process by allowing the steel to regain its internal crystalline structure. The trade-off between cold and hot working processes is that in exchange for the added strength of cold working the steel can become more brittle, while heat worked steel generally retains greater ductility.
Cold Bending for Different Steel Configurations
Any cross-section and size of steel can be cold bent or rolled as long as it can fit into existing dies and rollers. Cold bending is most commonly applied to pipes of less than 10 inches diameter, channels, I-beams, angles and rectangular, round and half-round bars. Large scale steel products such as plates can also be worked but sizes are limited due to the force necessary and the size of the rolling equipment needed. The bending process can be used to create gentle, large-diameter curves, 90ｰ corners or long series of pipe coils in which the pipe bends in a succession of 360ｰ circular turns.
Uses for Steel Shaped by Cold Bending
Cold bent steel has many uses. Curved steel formed by cold bending is frequently used in the construction of buildings and bridges and is especially impressive when left exposed to view. Shipbuilders, railroads and automobile manufacturers also use cold bent steel products. The petrochemical industry uses curved and coiled piping for processing and transporting their products. Cold bent steel also has many other industrial and food-processing uses as well.
Cold bending is an excellent way to shape steel with minimal deformation during the bending process. Steel shaped by cold bending can be found in applications ranging from commonly used everyday items to highly technical specialized industrial applications.