Stainless Steel Type 316L Pipes

These stainless steels require that the alloys be melted according to certain specifications. These specifications, in turn, depends on the grade as well as how it will be used. The stainless steel strips (from which the tube will ultimately be formed), is produced by either hot formed or cold formed coil.

Tube manufactured from cold formed stainless steel will ultimately have strong mechanical characteristics and a smooth surface finish. Furthermore, these types of tubing will also deliver closer tolerances as compared to stainless steel tubing manufactured from hot formed coil.

Note however that the welding process for both hot and cold rolled coil are the same. The process in short is as follows:

• The coils are first separated into designated widths, followed by forming processes.

• To seal the seams of each formed Stainless Steel Type 316L Pipes, welding rolls are used. These rolls also help to prevent the occurrence of tearing during welding processes.

• After the weld has been completed, the process will move on to the weld bead conditioning step. Weld roll down is commonly applied for thicker tube walls, whereas thinner tube walls will involve weld forging.

• Sizing will now occur. This entails that the tube meets the set requirements in terms of diameter, straightness and roundness.

• The tube is then cut to length - often called the cutoff step. Here the tube will be cut to meet length requirements by making use of several processes, the most common cutting processes being shear cutting and abrasive cutting.

Bending Stainless Steel Type 316L Pipes

In tube bending, it is the common objective to form a round bend that is smooth. Bending is a relatively easy process to complete if the tube has a heavy wall thickness and is bent to a large radius.

Determination of a heavy or thin wall thickness is determined by the wall factor. This calculation compares the wall thickness of the tube to its wall outside diameter as follows:

• Wall Factor = Tube Outside Diameter ÷ Tube Wall Thickness

 

In cases where the wall factor is more than 30, the tube will be categorized or classed as a thin wall tube. In order to determine the degree of the bend, the following calculation is applied:

• Degree of Bend = Bend Centerline Radius ÷ Tube Outside Diameter

 

These two calculations are crucial in order to determine the severity of the bend. With small tube diameters that have thick walls, very little to no interior support is necessary during bending processes, but as the diameter of the tube increases the tube itself becomes weaker.

In cases where tube walls are thinner and a tight bend radius is required, distortion as a result of bending may occur. The use of mandrels now become necessary.

Important factors to consider when bending tubes:

• Ductility

• Work Hardening

• Springback