Straight seam steel pipe plant for you to distinguish the ssaw steel pipe, lsaw steel pipe, seamless steel pipe:
LSAW steel pipe production process is relatively simple, the main production process of high-frequency welding straight seam steel pipe and submerged arc welded straight seam steel pipe, straight seam pipe production efficiency, low cost and rapid development. The strength of spiral welded pipes is generally higher than that of longitudinal welded pipes. The main production process is submerged arc welding.
Spiral steel pipes can produce welded pipes with different pipe diameters using the same width of blanks, and narrower blanks can also be used to produce larger diameter pipes. However, compared with the straight seam pipe of the same length, the length of the weld seam increases by 30 to 100%, and the production speed is low. Therefore, the smaller diameter welded pipe mostly adopts the straight seam welding, and the large diameter welded pipe adopts the spiral welding. In the industry, large-diameter straight seam steel pipe will use T-welding technology, that is, a short length of straight seam steel pipe will be butt jointed to meet the length required by the project, the probability of T-shaped welding straight seam steel pipe defects is greatly improved, and T-welding The welding residual stress at the seam is large, and the weld metal is often in a three-dimensional stress state, increasing the possibility of cracking.
From the welding process, SSAW steel pipe and LSAW steel pipe welding method is the same, but the straight seam welded pipe will inevitably have a lot of T-
welding, so the probability of the existence of welding defects is also greatly improved, and the T-welded at the The welding residual stress is large, and the weld metal is often in a three-dimensional stress state, increasing the possibility of cracking. Moreover, according to the submerged-arc welding process specification, each weld should have an arc striking point and an arc extinguishing point. However, each straight-seam welding pipe cannot achieve this condition when welding a circumferential ring, and thus may have an arc extinguishing position. More welding defects.
The trend of pipeline development is large diameter and high strength. With the increase of the diameter of the steel pipe and the improvement of the grade of steel used, the tendency is greater that the ductile fracture develops steadily.
Pipeline due to the change in the amount of transport, in the actual operation, the steel pipe is subjected to a random alternating load effect. Understanding the low cycle fatigue strength of steel pipes is of great significance to determine the service life of pipelines.
According to the measurement results, the fatigue strength of the spiral welded pipe is the same as that of the seamless pipe and the electric resistance welded pipe. The test data is distributed in the same area as the seamless pipe and the resistance pipe, and higher than that of the ordinary submerged arc straight seam welded pipe.