Aluminum, Stainless, and Carbon Steel Square Tubing Bending
Square Tube Bending Machine
To bend your square tubes as accurately as possible, please choose the right square tube roller with our guidelines. BIT is proud to recommend the PBH Section Bending Machine for your square tube bending project.
Maybe you will like to check out our profile bending process page.
SHS Metal Square Tubing
Square hollow sections/SHS steel ( square tube/pipe ) are another popular type of structural steel tube. They are a kind of intermediate between RHS steel tubing and CHS beams in terms of appearance and structural behavior. Square section steel also has a flat surface and clean lines — which both make welding and joining very economical.
Square and rectangular tubing are always called out the same way. The first two numbers designate the size of the material (in inches). The last number (typically represented as a decimal) defines the thickness of the tubing. An example callout for standard rectangular tubing would be TS 8” x 6” x .375”. This tubing measures 8” long x 6” wide and has a wall thickness of 3/8”. You know this is rectangular tubing because the sides are not equal.
Carbon square and rectangular materials (mill produced) are classified as ASTM A500 resulting in a yield point (psi) of 39,000 minimum for Grade A and 46,000 minimum for Grade B.
Related Reading： Similarities Between Bending Round and Rectangular Tubing
Square and Rectangular materials can be used in virtually any application. Structural (roof trusses), ornamental (staircases), recreational (bike racks), manufacturing (various widgets), and artistic. Virtually, anything that needs to bend, can be and is designed out of square and rectangular materials (HSS materials).
Notes: Square section steel often provides the ideal balance between strength, aesthetic appearance, and functionality.
These three reasons are why square metal tubing is still so popular to this day. But like the RHS sections, steel tube squares are difficult to use. It is hard to bolt them to beams. Square steel tubing also comes in ‘hot’ and ‘cold’ forms. Another name for them is a “box section”.
Hot Bending And Cold Bending
There are many types of bending square tubing, but the simplest classification method is to divide them into hot bending and cold bending.
There are pros and cons to both hot and cold bending, depending on the type of material you need to be bent and the angle of the bend required.
Cold bending methods often rely on sheer physical force to help bring the pipe to its final shape, it is more suitable for bending iron tubes, stainless steel tubes, aluminum tubes and copper tubes; while hot bending methods use careful heating to reduce the force required. Read More: Nine steps of the square tube induction bending process
Hot Bending VS Cold Bending: Compared with hot bending, the cold bending of automatic square & rectangular tube bender needs more bending power, and the spring back and residual stress increase obviously. The full-automatic square & rectangular bending machine cannot bend sharp bends with a small radius of curvature. Hot bending can form a small radius elbow on the pipe. For carbon steel pipe and most alloy steel pipe, the bending radius of hot bending is much smaller than that of cold bending by automatic pipe bender, and the bending radius can be as small as 0.7-1.5 times of the outer diameter of the pipe. However, hot bending still has the following disadvantages: complex equipment, high processing cost, low production efficiency, and poor surface finish.
Four methods of bending square tube
BIT PBH/PBA series profile bending machine‘s ability to roll bending both round, square, and rectangular tubing. For rectangular tubing, it can bend both the easy way (against the weak axis) and the hard way (against the strong axis). It can even provide Multi-Plane bending where we are bending both the easy way and the hard way. Related Reading： Square and rectangular tubing is also known as HSS (hollow structural steel).
Square and rectangular tubing are also known as HSS (hollow structural steel), the name is always called out the same way( The first two numbers designate the size of the material in inches). it includes aluminum, stainless, carbon steel, copper, zirconium, and titanium tubing.
Cold roll bending square and rectangular tubing can be used with and without a mandrel. If the material with mandrels, the hollow material into a solid. This helps minimize distortion without increasing the thickness of the material.
Read More: Easy-Way vs. Hard-Way of Profile Bending
Three Notes For Bending Aluminum, Stainless/Carbon Steel Tubes
However, there is some troubleshooting to do when performing steel tube bending.
- Bends often require achieving a tight radius. Since the outer wall of the bend becomes thinner, the result may be a distorted bend. To prevent this, using a mandrel to give support is recommended. That is also why press or ram bending is not recommended in these situations. The most adequate bending method would be mandrel bending, which is the same as rotary draw bending but adds a mandrel to support the inside of the pipe.
- Sometimes the radius we need to achieve makes the steel to exceed its elastic limits. It can result in deformation in the form of a hump or wrinkles. To prevent the formation of humps and wrinkles, it is recommended to use rotary draw bending or three-roll bending.
- When bending stainless steel tubes and pipes, it is important to remember that some stainless steel requires around 50% more power for bending than carbon steel. Therefore, the machinery must be set accordingly.
Four Tips That Influence The Tubing Bending Process
Several tips can help to ease the bending of square or rectangular material and reduce the amount of distortion in bent tubes.
- Factors 1#: Wall Thickness. Bending round, square, or rectangular material involves stretching the outside diameter (OD) of the bend and compressing its ID. Consequently, a heavier wall thickness allows for a tighter bend radius and more material stretchability with less distortion.
Method of Bending. This is a key factor in controlling distortion. A correctly chosen procedure can help to produce consistent tolerances and accurate parts. Generally, smaller material requires rotary draw bending or compression bending, which can incorporate wiper dies and mandrels. Induction and increment bending should be used with larger material bent to a larger radius. Design distortion and material size are important factors for determining the bending method.
In many cases, there is no better factor than experience. Many trained bending artisans know what is required to produce an acceptable product.
- Factors 2#: Size of Material. Larger material bent to a smaller radius has a greater chance to distort than smaller material bent to a larger radius. Design and planning are necessary to help solve bending problems before they arise.
- Factors 3#: Tooling. After the parts have been designed, the method of bending has been chosen, and procedures to bend to proper tolerances are established, the machine must be set up with the proper tooling. Based on design conditions, tooling that can be used includes a bend die, clamp block, follower block, mandrel, and wiper die. All or some of this tooling may be required.
- Factors 4#: Internal and External Lubricant. Lubricants decrease the friction between the tooling and the material to be bent. When friction is reduced, material flows smoothly through the bending equipment, allowing the machinery to perform its designed operation efficiently.
:: Reference: Bending square and rectangular tubing
Six Parameters Of Bending Tubing
The basics of bending are the same for all materials in that certain information is required to produce an accurate part of a square pipe:
- Degree of bend
- The radius of the bent section
- Chord of the bent section
- Arc length
- The slope of the bent section
- Tangent lengths
It isn’t necessary to know all six parameters. However, at least three must be known to produce a bent section.
Read More: How Does Bending The Stainless Steel Tubing