Tube Bending and Curving

Metal tubing is a very versatile product. Curved, bent or straight, it is often used in any number of applications. Think of your bent shower curtain rod, wavy neighborhood bike stand, curved front-loader “bucket arms” or tubular arches used as structural supports for bridges. Metal tubing is virtually everywhere!

For an untrained eye, any steel tube that isn’t perfectly straight is either “bent” or “curved.” However, in our business, experts draw a subtle distinction. A “curved steel tube” is usually understood to have a relatively large radius. (Think of a longitudinal bridge support or a steel canopy arch). On the other hand, a “bent tube” has a sharp change in direction, i.e. a relatively tight radius. (Think of your bathroom towel rod–sometimes produced from an aluminum tube bending process–or think of a snake-like bike stand with 90 or 180-degree sharp bends). Because they are hollow (They are referred to as Hollow Structural Steel, or simply, HSS.), metal tubes lack solidity, if you will. Quality metal tube bending, therefore, requires the proper machine, the right tooling and the expertise of a skilled bender. The process of bending and curving is often prone to distortion, ovality, shrinkage and elongation of various kinds, making the above-mentioned pre-requisites all the more important.

Usually, an internal steel plug or mandrel is used to support the tube through the bending or curving process in the machine. Speaking generally, the tube bending or curving process – done in cold state –causes a “work hardening” of the material, wherein the yield and tensile strengths may rise approximately 10 percent —the material actually gets “stronger.” After the material has surpassed its yield point and crosses into its tensile range, prior to its “peak tensile point,” elongation may decrease approximately 15 percent —that is to say, the material has less “stretch” available before it breaks.
However, with the right machine, the right method, the right material and the right man bending the steel, superior tube bending can be accomplished.


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