Advantages and disadvantages of spiral steel pipe

Spiral pipe defects in the vast majority concentrated in the weld and heat affected zone, weld defects occur long it means that the probability of large, long-term constraints which is more widely used spiral welded main reason, but also has long vexed spiral pipe and straight seam pipe, especially when compared with the UOE steel pipe whose superior problem. Spiral pipe manufacturing technology development today, we should be fully and accurately evaluated and compared to rediscover long spiral weld problems. Also in use, the tube of the main stress direction, i.e. the axial direction of tube defects equivalent pipe length smaller than the straight seam; Second, because pipeline are rolled steel, impact toughness greater anisotropy, cis rolling CVN value of the direction perpendicular to the rolling direction than CVN value three times higher. Straight seam pipe stress suffered by the main shock resistance precisely perpendicular to the lowest pipe direction, and then staggered spiral steel pipe direction lowest impact resistance, so that the disadvantage of a long spiral weld transformed into advantage.

Although the spiral steel pipe is mainly used in water engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction, is the development of 20 key products. For the transport of liquids: water supply and drainage. For gas transportation: gas, steam, liquefied petroleum gas. For structural purposes: as piling pipe for bridges; docks, roads, buildings and other structures tube. However, the spiral in the welding process there are some inherent defects.

The specific requirements of the steel strip coil is forward weldability of steel, reducing the sulfur content in the steel pipe to improve the toughness and arrestability are beneficial. While also reducing sulfide inclusions to the swap, forward of steel crack resistance. The phosphorus content in the hot strip is as low as possible, because the phosphorus on the steel toughness and weldability are a hazard, thus reducing the phosphorus content can move weldability, can increase the amount of added titanium, vanadium niobium content spiral during welding weld defects may occur, so that welding defects affect the quality of the spiral, resulting in reduced service life or the spiral can be used. Generally, the spiral weld defects and porosity, and cracks undercut phenomenon.

Spiral bubble defect: During spiral welding, the weld bead in the center of bubble defects occur this situation, the main reason is that in the course of the welding of hydrogen is left in the form of bubbles within the metal. In the welding process, we need to remove the oil inside the weld, water and other ingredients, but also the need to do drying, removal of moisture, so that hydrogen gas will not remain in the inside seam. During the welding process the welding current can be avoided to increase the generation of bubbles.

Spiral undercut phenomenon: When the v-shaped groove weld edges appear, and along the weld centerline arise, it means there has been undercut. Generally undercut because of current, voltage and welding speed inappropriate, therefore, in the welding process requires control your speed, so as to effectively avoid undercut phenomenon.

Spiral cracks: spiral cracks may be produced due to the direction of the spiral seam problem spiral in order to effectively prevent the generation of cracks in the welding process, the welding process need to operate in strict accordance with the job.