Views: 0 Author: Site Editor Publish Time: 2021-03-05 Origin: Site
A pipe in which the weld is helically distributed relative to the axis of the pipe body. Mainly used for conveying pipes, pipe piles and some structural pipes.
Product specifications: outer diameter 300～3660mm, wall thickness 3.2～25.4mm.
The characteristics of spiral welded pipe production are:
(1) Tubes with a variety of outer diameters can be produced with strips of the same width;
(2) The pipe has good straightness and precise dimensions. The inner and outer spiral welds increase the rigidity of the pipe body, so there is no need for sizing and straightening after welding;
(3) It is easy to realize mechanization, automation and continuous production;
(4) Compared with other equipment of similar scale, it has small dimensions, less land occupation and investment, and faster construction;
(5) Compared with the straight seam welded pipe of the same size, the weld per unit length of the pipe is longer, so the productivity is lower.
The production process of spiral welded pipe,the raw materials of spiral welded pipe are strip and plate, and the thickness is more than 19mm with plate. When using strip material, in order to ensure the continuous feeding of the front and rear plates during the butt welding of the front and rear coils, a looper device or a flying welding trolley can be used for butt welding connection. The flying welding trolley can operate the entire material preparation from uncoiling to butt welding along the track completed during the move.
When the tail of the front coil is bitten by the rear clamp of the butt welding machine, the trolley is pulled forward at a speed synchronized with the forming-prewelding machine. After the butt welding is completed, the rear clamp is released and the trolley returns by itself. In place. When using plates, a single steel plate needs to be butt welded into slats outside the work line, and then sent to the work flow line to be butt welded with a flying welding trolley. Automatic submerged arc welding is used for butt welding, which is carried out on the inner surface of the pipe. The incomplete weld is formed and pre-welded, and then repaired on the outer surface of the pipe, and then the spiral welds are welded inside and outside. Before the strip enters the forming machine, the edge of the plate must be pre-bent with a certain curvature according to the pipe diameter, wall thickness and forming angle, so that the deformation curvature of the edge and the middle part after forming is consistent, and the "slub" defect that protrudes in the weld area can be prevented.
After pre-bending, it enters the spiral former for forming (see spiral forming) and pre-welding. In order to improve productivity, one more formed and one pre-welded line is used to match multiple internal and external welding lines. This can not only improve the quality of the weld, but also greatly increase the output.
Pre-welding generally adopts faster welding speed shielding gas arc welding or high-frequency resistance welding, full-length welding, this welding adopts multi-pole automatic submerged arc welding.
The main development direction of spiral welded pipe production As the bearing pressure of pipelines is increasing, the use conditions are increasingly harsh, and the service life of the pipeline should be extended as much as possible, so the main development directions of spiral welded pipes are:
(1) Produce large-diameter thick-walled pipes to improve pressure resistance;
(2) Design and produce steel pipes with new structures, such as double-layer spiral welded pipes, that is, double-layer pipes are welded with strip steel half the thickness of the pipe wall, which not only has higher strength than single-layer pipes of the same thickness, but also does not cause brittle failure;
(3) Develop new steel grades, improve the level of smelting technology, and widely adopt controlled rolling and post-rolling heat treatment processes to continuously improve the strength and toughness of the pipe body and welding performance;
(4) Vigorously develop coated pipes, such as coating the inner wall of the pipe with an anti-corrosion layer, not only can extend the service life, but also improve the smoothness of the inner wall, reduce fluid friction resistance, reduce wax and dirt, reduce the number of pigs, and reduce maintenance cost.