Straight seam steel pipe refers to a steel pipe whose weld seam is parallel to the length of the steel pipe. Its production process is relatively simple. The strength of spiral steel pipe is generally higher than that of straight seam steel pipe. It can produce welded pipes with larger diameters from a narrower blank, and can also produce welded pipes with different diameters from a blank of the same width, but compared with a straight seam welded pipe of the same length, the weld length is increased by 30%-100%. The production speed has slowed down. According to its production process, it can be divided into high frequency straight seam steel pipe (erw steel pipe) and submerged arc welded straight seam steel pipe (lsaw steel pipe). The submerged arc welded straight seam steel pipes are divided into UOE, RBE and JCOE steel pipes according to their different forming methods. For most forming methods, the last process is to expand the full-length diameter of the welded pipe blank again to improve the shape of the welded steel pipe. Diameter expansion has become an important process to ensure the finished pipe in the production of longitudinal welded pipes. The mechanical method is simpler and more efficient than the hydraulic method. Several types of straight seam welded control pipelines are used internationally.
1. The initial round stage. The sector blocks are opened until all sector blocks are in contact with the inner wall of the steel pipe. At this time, the radius of the round pipe in the steel pipe is almost the same within the step size range, and the steel pipe reaches the initial circle.
2. Nominal inner diameter level. The sector block starts from the front until it reaches a predetermined position, which is the circumferential position required for the finished tube.
3. Flexible recovery and compensation stage. The position of the sector block in the second stage will be further reduced until it reaches the required position, that is, the circumferential position of the elastic front steel pipe required by the process design.
Heat treatment method of straight seam steel pipe:
First of all, the mold should be planned reasonably, the thickness should not be too wide, and the shape should be symmetrical. For molds with larger deformations, the deformation laws should be mastered and machining allowances should be reserved. For large, precise and messy molds, combination planning can be selected, and preheating can be used. Treatment, aging heat treatment and tempering nitriding heat treatment to control the accuracy of the mold. When repairing mold sand holes, pores, wear and other defects, use cold welders and other correction equipment with low thermal influence to avoid deformation in the repair process. Pre-heat treatment of the precision messy mold eliminates the stress attack of the rest of the machining process. For precision fluffy molds, vacuum heating and quenching after cryogenic treatment should be selected as far as possible. On the premise of ensuring the hardness of the mold, try to choose the pre-cooling, graded cooling quenching or temperature quenching process.
Thick-walled spiral steel pipe
is better than ordinary spiral pipe in mechanical properties such as compression and tension. In engineering, high requirements are put forward for the use of spiral pipes. The reason why thick-walled spiral pipes appear is because the pressure generated by some media that needs to be transported is unbearable by ordinary spiral pipes. If it is replaced with straight seam or seamless steel pipe, the project cost will be greatly increased. Spiral seam arc welded pipes are used for ordinary fluid conveying pipes. Part of technical requirements for steel pipes in the liquefied petroleum gas industry: steel pipes. The rust removal speed of the spiral steel pipe depends on the type of abrasive and the displacement of the abrasive. Generally, the abrasive with low loss rate should be selected, which is beneficial to increase the cleaning speed and long blade life. Pay attention to the importance of surface treatment in production, and strictly control the process parameters when removing rust. In actual construction, the peeling strength of the steel pipe anticorrosive layer greatly exceeds the standard requirements, ensuring the anticorrosive layer. On the basis of the same equipment, the process level is greatly improved and the production cost is reduced.