Spiral Steel Pipe Manufacturer: Some Basic Facts About Longitudinal Seam Steel Pipes

　　 Spiral steel pipe Manufacturers consider the corrosion resistance of thick-walled straight-seam steel pipes and the extension of their service life to be ongoing concerns for pipeline designers and constructors. Over nearly six decades of development, global pipeline corrosion‑protection technologies and theories have largely reached maturity and stability. Steel pipes with an outer diameter-to-wall-thickness ratio of less than 20 are classified as thick-walled straight-seam steel pipes. They are primarily used as drill pipes for petroleum and geological exploration, cracking tubes in the petrochemical industry, boiler tubes, bearing tubes, and high‑precision structural tubes for automobiles, tractors, and aerospace applications.

　　Spiral steel pipe manufacturers consider the primary distinction between thick-walled and thin-walled longitudinal seam steel pipes to lie in wall thickness. It is generally accepted that a wall‑to‑diameter ratio of 0.02 serves as the dividing line between these two categories. In piping applications, thin-walled pipes with a wall‑to‑diameter ratio below 0.02 are commonly used, while thicker‑walled pipes with a ratio exceeding 0.02 are employed for structural components and critical pressure‑bearing pipelines. Thick-walled longitudinal seam steel pipes are predominantly utilized as blanks for hollow parts and in critical pressure‑bearing pipelines.

　　Spiral steel pipe manufacturers define nonferrous metals—also known as non‑ferrous metals—as all metals and alloys other than ferrous metals, including copper, tin, lead, zinc, aluminum, brass, bronze, aluminum alloys, and bearing alloys. These metals are primarily used as alloying additives to enhance material properties; examples include tungsten, steel, titanium, and molybdenum. Hard alloys, mainly employed in the manufacture of cutting tools, are also classified as nonferrous metals. In addition to steel, there are precious metals such as platinum, gold, and silver, as well as other rare metals, including radioactive uranium, radium, and various other steels.

　　Spiral steel pipe manufacturers believe that various nondestructive testing methods are widely employed in the production of thick-walled steel pipes across sectors such as oil and gas, chemical engineering, and urban gas pipeline systems. Any leakage or fracture during transportation can result in immeasurable losses for straight‑wall steel pipes. Therefore, it is essential to utilize a range of inspection techniques and procedures to ensure the quality of longitudinally welded steel pipes used for oil and gas transmission. Large‑diameter, thick‑walled, longitudinally welded steel pipes are characterized by relatively simple manufacturing processes, including high‑frequency welding, submerged‑arc welding, resistance welding, electric‑arc welding, and spiral welding. These pipes can be produced rapidly and continuously, finding extensive applications in civil construction, petrochemicals, light industry, and other fields. They are commonly used for conveying low‑pressure fluids or for fabricating various structural components and light‑industrial products.

　　Spiral steel pipe manufacturers believe that thick-walled straight-seam steel pipes have the following advantages:

　　1. The dimensions of a longitudinal submerged-arc welding production line are significantly smaller than those of a longitudinal submerged-arc welded steel pipe production line, and the unit price of the finished steel pipes is also lower.

　　2. Steel strips of the same width can be used to produce steel pipes of varying diameters; the process is easy to adjust, and changing specifications is convenient. It is suitable for both large-scale and small-scale production, and the manufacturing process lends itself readily to mechanization, automation, and continuous operation.

　　3. Spiral steel pipe manufacturers contend that the weld seam of a straight‑seam welded steel pipe exhibits a principal stress direction. When the pipe is subjected to internal pressure, the dominant stress is hoop stress. In contrast, the angle between the weld and the pipe’s longitudinal axis is 45 degrees, thereby avoiding the principal stress; however, in straight‑seam welded steel pipes, the principal stress is precisely perpendicular to the weld.

　　4. Steel pipe manufacturers note that steel pipes exhibit higher impact toughness in the rolling direction and lower impact toughness perpendicular to the rolling direction, with the two differing by several times. In straight-seam welded steel pipes, the weak points in toughness are located away from the principal stress zones, whereas in these same pipes, the weak points coincide precisely with the regions subjected to principal stresses.