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Bending stainless steel tube technology in profile bending

Profile bending machine bending tubes

Profile bending

Profile bending refers to the bending process of the profile, in which the profile passes through the forming pressure roller, resulting in continuous bending.

Profile bending machine bending tubes
Profile bending machine bending tubes

The profile workpiece is placed on top of the two lower rollers. The upper roller presses down the contour between the two rollers. This will cause plastic deformation and bending of the workpiece. The profile of the roller is adapted to the specific profile, thus offsetting the deformation of the cross section. The profile is then fed into the whole process by the drive roller and is continuously bent in this way. Repeat this process until the desired radius is reached.

Rolling controlled by PLC/CNC can achieve different radii.

Basic knowledge of metal tube bending

Tensile stress of profile bending

When the metal tube is bent, the cross-sectional material fiber is pulled on the outside of the bending area and compressed on the inside of the bending area. Due to tensile stress, the wall thickness of the outer cross-section of the bend will become thinner, because the outer wall tends to be pulled toward the centerline or neutral axis of the part.

Bending deformation

If the ultimate tensile stress of the material is exceeded, the tube will tear along the outer curved surface.
Due to the compressive stress, the wall thickness on the inside of the elbow will become thicker.
If the ultimate compressive strength of the material is reached, the tube will experience local buckling, causing ripples on the inner curved surface.

Deformation of round tube and square tube

In elbows, you can bend round or square pipes.
The round tube has less material in the high stress area.
The highest tension or compression plane is tangent to the cross section, so it is not easy to deform.
In a square tube, the entire tube wall is parallel to the plane, and therefore bears tensile and compressive stresses on the outside and inside of the bend.
This makes the square tube easier to deform.

The round tube allows the metal to flow evenly in all directions during the bending process, making it easier to control the deformation.
The square tube material inside the curved surface tends to expand vertically along the tube surface and flow horizontally.
These forces act in a certain way, pulling in the vertical edge of the tube, deforming the cross section into a concave shape. Compared with a round tube, the deformation in a square tube is physically more difficult to control.

A good rule of thumb when designing bends is that as the outer diameter increases and the wall thickness decreases, the tube becomes more difficult to bend.

Bending of stainless steel pipe/tube

Curved stainless steel

Although stainless steel is a very hard material, stainless steel has ductility and ductility, and can be formed into various shapes using various mechanical means.

Bent stainless steel tube

Bending stainless steel pipe/tube is a process that can be used to shape stainless steel pipe into many useful configurations.
The difficulty of bending a section of pipe depends on the thickness of the pipe.
Although thick-walled pipe requires more force to bend, it is less likely to fail during the bending process than thin-walled materials.
Pipes of different sizes need their own set of molds.

Bending seam stainless steel pipe

Although any type of steel pipe can be formed by bending, steel pipes without seams generally respond better to the bending process than welded or seamed pipes.

Even moderate bending can weaken or break the joint, although this problem can be slightly reduced by bending the tube in a way that reduces the stress directly applied to the joint.

Precautions for bending stainless steel pipe

In addition to weakening the joints, the bending process also weakens the structure of the pipe itself.

When the tube is bent, the steel along the outside of the curve is stretched, while the material on the inside of the curve is compressed.

If the pipe is bent too hard, the outside of the curve may become thinner than the rest of the pipe, making this area more prone to failure.

Another important consideration for stainless steel pipe is to maintain the inner diameter and structure of the pipe.

Even with the use of a mandrel, the pipe may be slightly deformed during the bending process.

Any deformation of the inner diameter of the liquid-carrying pipe or pipe will disrupt the flow pattern of the internal fluid.

This, in turn, will cause scour inside the tube, which can cause the tube to thin out and eventually fail. When the pipe is bent for structural or decorative purposes, the deformation of the internal dimensions of the pipe is less important.

Application of stainless steel pipe

Products made of stainless steel bending have a wide range of uses.

Stainless steel is an inert steel that is very suitable for food processing, food service and pharmaceutical production operations. Stainless steel pipes also have structural uses and can also be polished for decorative purposes, including railings, lamps, and works of art.

Stainless steel pipe requires special handling and tools to bend correctly.

However, when the bending is performed correctly, the finished product has many important industrial, structural and even decorative uses.