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Things You Never Knew About Seamless Steel Tubing

Global Seamless
Things You Never Knew About Seamless Steel Tubing

Seamless tubes and pipes are used in many applications. Manufacturers specializing in this field produce tubes ranging from one inch in diameter to finer than human hair. Now, this can have a continuous length that can exceed a mile. Seamless pipes are basically utilized in the flow of gas, steam, and liquid in harsh environments.


Manufacturing process


Typically, the manufacturing process includes extruding, gun drilling, or piercing. However, the extrusion process involves the most uniform OD and a concentric ID. However, extrusion is the only process that is suitable for long length seamless steel coil tubing. Here the raw materials begin in the form of hot extruded seamless pipe.


It is further cold. Additionally, the raw material is processed through the tube reducers, which are generally termed Pilger mills. This makes the tube straight. Cold Pilger involves maintaining uniform ODs and concentric IDs. It is a longitudinal cold-rolling process that reduces steel tubes' diameter and wall thickness in a single operation.


The addition of lubricants is an integral part of the OD and ID. Moreover, it is degreased in preparation for annealing. The process typically produces lengths from around 40 feet to 160 feet in length once reduced.


Drawing Types


Here seamless tubes and pipes manufacturers differentiate two primary drawing operations.


Floating Plug


Floating plug drawing is the process where the tubing is pulled through a conical die. Meanwhile, this process produces a more consistent, smoother product that can only be based on relatively light wall products.


Sink Drawing


The process of sink drawing is when the tubing is pulled through a conical die, and the resulting ID and wall thickness are determined based on the drawing and tubing parameters. This process is utilized when the heavy relative wall thickness is required for high-pressure applications. Here, seamless tubes and pipes manufacturers include an ID that's a bit rougher as compared to a floating plug drawing.


Vacuum Annealing


Seamless tubes and pipes manufacturers generally anneal long straight lengths and coils after cold reduction in order to remove internal stresses and restore the crystalline structure of the material. This further initiates cold working.


The rapid cooling of the annealing process transforms the cold-worked, brittle, and rigid material into ductile again. 




Once the tube is fully formed to the desired specification, seamless tubes and pipes manufacturers comprehensively test them hydrostatically. Testing determines and verifies that the lines meet the specification or the standard operating procedure. One can obtain several types of information through the verification process. Data that one can explore when choosing the products include


  • Material flaws
  • Mechanical properties
  • Hard spots that can fail when hydrogen is present


Final Product


Seamless coil tubing can be level wound on spools for shipment or straightened and cut to specific lengths as required by the customers.Seamless tubes and pipes can be further polished and stenciled for traceability and manufacturing identification.




The tubing of this type is generally manufactured to applicable ASTM standards. Also, manufacturers need to thoroughly test for potential defects before being shipped to the customers.



Global Seamless
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