Characteristics of Large Diameter Straight Seam Welding and Spiral Welding

Large-diameter straight seam welded steel pipe with steel production, and large-diameter spiral welded steel pipe with hot-rolled coil production. Hot strip rolling process unit has a series of advantages, have access to the production of high quality metallurgical process pipeline capacity. For example, the output with the bench in order to accelerate the cooling water cooling system, which allows the use of low alloy composition to achieve the specific level of strength and low temperature toughness to improve the weldability of the steel. However, this system is basically no steel production plant. Groove on the principles for large diameter spiral welded pipe is not allowed to play again flame cutting angle grinder grinding, so that the pipeline would cause adverse thermal effects, but the scene was not the construction unit beveling machines, the endless flame cutting machine After playing 45-degree cut, angle grinder and then repair the phenomenon is very common. Generally, we will use the U-shaped groove or a groove complex, due to the U-shaped groove, groove processing complex time-consuming, labor-intensive pipe welding power constraints. V-shaped groove processing simple, saving time, effort, but the large-diameter, thick-walled pipes when the whole initiative V-groove weld, welding parameters, such as the selection of wrong, will lead soldering shortcomings occur. Large-diameter straight seam welding requires flaw detection, pipe inspection with flying saw after cutting off the required length by flip frame off the assembly line. Both ends of the pipe should be flat head chamfering, print mark, finished the hexagonal tubes bundled packaging factory. Welded steel mechanical tests should be done and flattening test, and flaring test, and to meet the requirements of the standard. Alloy content Coil (carbon equivalent) is often lower than a similar grade steel, which also increases the large diameter spiral welded steel pipe weldability. Since the coil spiral welded steel pipe rolling direction than perpendicular to the axial direction (the solution depends on its steel clip helix angle), and straight seam welded steel rolling direction perpendicular to the pipe axis direction, and therefore, crack resistance spiral welded materials better than the straight seam welded. Magnaflux straight seam welding defects can only be found Q235B Longitudinal magnetic surface and near surface, but only for quantitative analysis of the defect, the nature and depth of the defect can only be estimated based on experience. Magnetic flux leakage testing is the use of a magnetic field generated by ferromagnetic Q235B Longitudinal to discover defects. By measuring magnetic flux leakage methods can be divided into magnetic particle method, the magnetic induction method and magnetic recording method, in which the magnetic particle method most widely used. The spiral weld penetration testing is the use of physical characteristics such as permeability of certain liquids to discover and display defects, including two colored and fluorescent detection test used to detect defects ferromagnetic and non-ferromagnetic material surface.