The spiral welding steel pipe refers to the steel pipe with a steel tube with a seam with a seam with a steel belt or a steel plate bent to a round, square. According to the welding method, it can be divided into arc welded pipes, high -frequency or low -frequency resistance welded pipes, gas welding pipes, furnace welding pipes, and Bondi pipes. According to the shape of the weld, it can be divided into straight seam welded pipes and spiral welded pipes. Welding steel pipes are used for oil drilling and machinery manufacturing. The furnace welding pipe can be used as water gas pipes, etc., and large -diameter straight seam welded pipes are used for high -pressure oil and gas transportation, etc.; Spiral welded pipes are used for oil and gas transportation, pipe piles, and bridge pier. Welding steel pipes are lower than seamless steel pipes and high production efficiency.
When the strength characteristics of the steel pipe are affected by internal pressure, they usually generate two main stress on the tube wall, namely the radial stress Δy and axial stress Δx. The synthetic stress Δ = Δy (L/4SIN2α+COS2α) is synthetic at the weld.
The spiral angle of the spiral welded weld is generally 50-75 degrees, so the synthetic stress at the spiral weld is 60-85%of the main stress of the straight seam welded pipe. Under the same working pressure, the spiral tube of the same diameter can be reduced compared to the wall thickness of the straight welded pipe.
According to the above characteristics, we can see:
A. When the spiral pipe is blasting, due to the small stress and synthetic stress of the welds, the blasting port generally does not originate from the spiral welding seam, and its safety is higher than that of the straight seam welded pipe.
B. When the defects parallel near the spiral welds, because the spiral welds are less stressed, the risk of its expansion is not as large as the direct weld.
C. Because the radial stress is the maximum stress that exists on the steel pipe, the weld is in the direction of the vertical stress to bear the maximum load. That is, the load that is undertaken in straight seams is the largest.
