The main development direction of spiral steel pipe is to produce large-diameter thick-walled pipe to improve the pressure resistance capacity, design and produce new structure for the spiral steel pipe unit due to the increasing load pressure of pipeline, the increasingly harsh conditions of use and the longest service life of pipeline. Of the steel pipe, such as double spiral steel pipe, that is, with half the thickness of the pipe wall welded double pipe, not only the strength of the same thickness than the single-tube high, and will not appear brittle damage; vigorously develop coating pipe, In the pipe wall coated with anti-corrosion layer, not only can extend the service life, and can improve the smooth wall, reduce fluid friction, reduce wax and dirt, reduce the number of pigging, reduce maintenance costs, the development of new steel, improve smelting process Technology, widely used to control the rolling and residual heat treatment after rolling to continuously improve the strength and toughness of the pipe and welding performance.
Spiral pipe unit from the welding process, the spiral steel pipe and straight seam steel pipe welding method is consistent, but the straight seam welded pipe will inevitably have a lot of T-shaped weld, so there is the probability of welding defects is also greatly improved, and the weld Of the welding residual stress is large, the weld metal is often in a three-way stress state, increasing the possibility of cracks.According to the provisions of the submerged arc welding process, each arc should be arc and arc Department, but each This condition can not be achieved when the welding of straight seam welded pipe is done, so that there may be more welding defects in the arc-extinguishing area.Using air plasma cutting machine to cut the steel pipe into single pipe. , While the spiral steel pipe is hot-rolled coil production. In this case,
The rolling process of the hot strip mill has a number of advantages, such as a metallurgical process capability to produce high quality pipeline steel, for example, a water cooling system is provided on the output stage to accelerate cooling, which allows the use of low alloy components to achieve special (carbon equivalent) is often lower than similar grades of steel, which also increases the strength of the spiral steel pipe of the steel grade, and the low temperature toughness, thereby improving the weldability of steel, but this system is not in the steel plate production plant. (The pinch depends on the helix angle of the steel pipe), and the rolling direction of the steel plate of the straight seam steel pipe is perpendicular to the axis direction of the steel pipe, so that the spiral steel pipe has the rolling direction of the steel pipe, The crack resistance of the material is better than the straight seam steel pipe.
