This type of rolled products is named according to the manufacturing technology - steel sheet or strip (steel tape) is bent to give the desired shape (circle, oval, square, rectangle) and edges are joined by electric welding with high frequency current. Such technology causes several advantages of an electrowelded pipe over other types of pipes. The main geometrical dimensions of this rental are:
- pipe diameter (measured on the outer surface);
- wall thickness;
- pipe length
For pipes of section other than circular, instead of the diameter of a circle, the lengths of the sides (for a square and a rectangle) or the dimensions of the major and minor oval axes are given. All measurements are carried out on the outer surface.
After welding, deburring is performed, cooling and bringing the pipe to the desired size by passing it through a calibration mill (cooling is performed for cold-forming pipes). Then is trimmed and cut into pipes of a certain length. After this, heat treatment, final dressing, inspection and packaging are performed.
Advantages of electrowelded pipes
If we talk about the strength characteristics, the electrowelded pipes are not inferior seamless seamless, as modern equipment provides equal strength of the weld and the base material. From the main, we can distinguish the following:
- Highly versatile. Such pipes are used everywhere - in construction, in industry (engineering, furniture industry, etc.), in agriculture, in everyday life.
- Ease of manufacture. This is especially true of non-circular pipes.
- The possibility of manufacturing large diameter pipes.
Types of ERW pipes
Longitudinal pipes are much easier to make, so they are the most common. Helix pipes are pipes for high pressure or large diameter. Since for larger sizes, the breaking longitudinal forces increase, and the spiral seam is subjected to smaller loads than the straight line. The main classification is by the type of weld:
- Longitudinal - the seam is placed parallel to the axis of the pipe;
- Spiral end - seam is put in a spiral about the pipe axis.
By way of finishing
- Hot-formed - after welding, the pipe is hot-driven through the final roll group. This is the most economical technology.
- Cold-deformed - after welding, the pipe is cooled, and only then it is driven through the final roll group. The pipe turns out more expensive, but 25% stronger and with great accuracy in diameter and wall thickness.
By production material
- Group A - St1, St2, St3 and St4 of any degree of deoxidation - cn, ps, kn. Normalized mechanical properties.
- Group B - St1, St2, St3, St4, St08, St10, St15 and St20 of any degree of deoxidation, steel 08U, 22GU. Normalized chemical composition.
- Group B - steel grades are similar to group B, but the chemical composition and mechanical properties are normalized.
- Group D - Steel grades are similar to Group B, but test hydraulic pressure is normalized.
The shape of the section
- round (thin-walled and thick-walled);