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A spiral tube is produced by winding a strip of low-carbon structural steel or low-alloy structural steel into a tube blank at a certain angle (called the forming angle) following a spiral line, and then welding the tube seams together. It allows the production of large-diameter steel pipes using relatively narrow steel strips. Its specifications are expressed as outer diameter * wall thickness. Welded pipes must ensure that the hydraulic test, tensile strength of the weld, and cold bending performance meet the specified requirements.
In terms of welding processes, the welding methods for spiral welded pipes and straight seam steel pipes are identical. However, straight seam steel pipes inevitably have many T-joint welds, which greatly increases the likelihood of welding defects. Moreover, the residual stress at the T-joint weld is relatively high, and the weld metal often experiences three-dimensional stress, increasing the possibility of cracking. Furthermore, according to the process specifications for submerged arc welding, each weld should have an arc strike and an arc blow-off point. However, this condition cannot be met when welding the circumferential seams of each straight seam steel pipe, which may result in more welding defects at the arc blow-off point.
Spiral pipes are primarily utilized in water supply projects, the petrochemical industry, the chemical industry, the power industry, agricultural irrigation, and urban construction. They are one of the twenty key products developed in China. For liquid transportation: water supply, drainage, sewage treatment projects, sludge transportation, and marine water transportation. For gas transportation: coal gas, steam, and liquefied petroleum gas. For structural purposes: as piling pipes, bridges, docks, roads, building structural pipes, and marine piling pipes.
product standard
Spiral submerged arc welded steel pipes for pressure fluid transportation SY5036-83 are primarily used for pipelines that transport oil and natural gas. Spiral high-frequency welded steel pipes for pressure fluid transportation SY5038-83, welded using high-frequency lap welding, are used for pressure fluid transportation. These steel pipes have strong pressure-bearing capacity and good plasticity, making them easy to weld and process into shape. Spiral submerged arc welded steel pipes for general low-pressure fluid transportation SY5037-83 are made using double-sided automatic submerged arc welding or single-sided welding, and are used for the transportation of general low-pressure fluids such as water, gas, air, and steam.
The commonly used standards for spiral steel pipes are generally divided into: SY/T5037-2000 (departmental standard, also known as Spiral Submerged Arc Welded Steel Pipes for Ordinary Fluid Transportation Pipelines), GB/T9711.1-1997 (national standard, also known as Technical Delivery Conditions for Steel Pipes for Oil and Natural Gas Industry Transportation - Part 1: Grade A Steel Pipes (with strict requirements for Grade B steel pipes specified in GB/T9711.2)), API-5L (American Petroleum Institute, also known as Line Pipe; which is further divided into two levels: PSL1 and PSL2), and SY/T5040-92 (Spiral Submerged Arc Welded Steel Pipes for Piles).
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