Production methods and applications of straight seam steel pipes

The diameter of straight seam steel pipes is between 89~1600mm, and can even be larger under special circumstances. The ratio of wall thickness to pipe diameter is about 0.06~0.08. Foreign modern pipe making technology can produce welded pipes with wall thicknesses up to 100mm.

Industrially, there are only a few ways to produce straight seam steel pipes with steel plates or strips. The difference in principle lies in the method of forming the steel pipe. The subsequent processing of the formed steel pipe is basically the same. In principle, the forming method depends on the distribution of the steel pipe welds. According to the distribution of welding seams, steel pipes are divided into two basic forms: straight seam steel pipes and spiral seam steel pipes. Correspondingly, the production of welded pipes is divided into the production of straight seam steel pipes and the production of spiral seam steel pipes.
Mainline pipelines for land and sea natural gas, water and oil transportation; stainless steel pipes for transporting chemical raw materials and products in the chemical industry; marine industrial pipes; boiler manufacturing pipes and special structural pipes.
Production of straight seam steel pipes: The production of straight seam steel pipes can be divided into two stages, namely the forming stage and the manufacturing stage after forming. The production of foreign large-diameter LSAW steel pipes is divided into four types according to the forming method:
UOE formation; roll forming; progressive compression forming; progressive bending forming.
Production of straight seam steel pipes:
Forming stage:
UOE formation:
This method has the highest productivity and is also the main production method of straight seam steel pipes. The short production process of this device is to first bend it into a U shape, then press it into an O shape, and then perform mechanical cold expansion after internal and external welding. The characteristics of this method The aim is to obtain extremely stable steel pipes with high production capacity, and can produce steel pipes with a length exceeding 18m.
Roll forming is a method in which a steel plate is bent into an open tube after several treatments on a roll bending machine, and the edges of the opening are straight without deformation. Then, the open tube is sent to the folding machine, and the two edges of the board are continuously rolled into shape. This method is characterized by strong adaptability, economical and suitable for medium production, but the minimum diameter and maximum wall thickness of the produced steel pipes are limited. The formation process of this progressive compression molding method is to first send the steel plate into compression molding, then send it to the bending position by the controller, and then go through a series of compression moldings that match the pipe diameter to form an open tube. There are two controllers during operation. One side of the board is first bent into a semicircle, then the second controller moves the board and the other side is bent into shape. This method has strong adaptability, good medium production economy, and can produce small-diameter, thick-walled steel pipes.
Gradually bend and shape. Steel pipes formed by this method were originally used in the marine industry. Since it is usually necessary to produce particularly thick steel pipes using controlled rolling plates in the cold state, this method has high forming accuracy and applied pressure and is therefore used to manufacture thick-walled steel pipes for the shipbuilding industry. It is suitable for small and large diameters, so it can be used for main pipes and marine structural pipes; the system equipment has low cost, strong adaptability and good economical performance, which can reduce costs even for small batch production.
Manufacturing stage after forming After completing the above forming stage, the subsequent manufacturing stage of large-diameter straight seam steel pipes includes a series of basically similar processes. The main processes are:
The edges of the plates are machined with welding grooves. There are two machining methods: milling and planing. On both sides of the board, there can be one or more milling heads, which, depending on the thickness of the board, can machine the grooves into I-shaped, single V or double V grooves with a certain blunt edge.
Butt welding is often called pre-welding. Typically, carbon dioxide gas shielded welding is used to stabilize steel pipes. This is particularly useful for subsequent submerged arc welding to prevent burn-through. Steel pipes should be visually inspected after spot welding to ensure that the weld is continuous and free of any defects.
The internal and external welding of steel pipes is called precision welding. After the spot welding of the steel pipe, the subsequent welding is mainly the internal and external welding of the steel pipe, which is an important part of the steel pipe manufacturing process. In order to avoid weld seam deviation, a special automatic weld seam centering device is installed on the welding head. Multi-layer welding is used on thick-walled steel pipes to reduce heat input and improve the physical properties of the weld