Thick-walled spiral welded pipe cutting method

A spiral steel pipe (SSAW steel pipe) is a welded pipe produced by rolling a strip of low-carbon structural steel or low-alloy structural steel into a tubular shape at a specific helical angle (referred to as the forming angle), and then welding the seams. Different types of spiral welded pipes require different cutting methods, and the cutting methods for thick-walled spiral welded pipes are as follows.

1. Shearing Method

Shearing offers high productivity with no metal loss during the process. However, due to the flattening effect at the cut surface, it can lead to angled cuts, and this method struggles when cutting high-alloy steel. As a result, shearing is generally used for smaller units or products made from low-alloy steel and carbon steel, where precision is less critical.

2. Sawing Method

Sawing produces a straight end surface on the cut pipe blank, which simplifies centering and makes piercing easier. This method also ensures a relatively uniform wall thickness in the hollow blank (or capillary tube). Sawing machines can be used to cut pipe blanks of various steel grades. However, the main drawbacks are its low productivity and high saw blade wear.

3. Breaking Method

Breaking is a highly productive method, but it results in an uneven section at the cut, which may lead to uneven wall thickness when piercing. Additionally, breaking is difficult for low-carbon and alloy steels, making it less suitable for these materials. This method is mainly found in older production units, while newer units generally avoid using breaking techniques.

4. Flame Cutting Method

Flame cutting produces a smooth, flat section with a kerf width of about 6-7 mm and has a relatively low initial investment cost. It is a flexible cutting method that can handle both round and square billets and can be used on various steel grades for spiral welded pipes. However, flame cutting has some limitations, particularly with carbon steel and alloy steels that have a carbon content above 0.45%. Additionally, it involves metal consumption, requires significant oxygen and gas resources, and can lead to pollution in the workshop environment.

Each of these methods has its own advantages and disadvantages, and the selection of the appropriate cutting technique depends on the specific characteristics of the pipe and the requirements of the production process.