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How is Seamless Stainless Steel Tubing Made(1)

How is Seamless Stainless Steel Tubing Made?

Stainless steel tubing is a widely-used metal alloy material for various applications due to its outstanding corrosion resistance, strength and toughness at various temperatures.

Tubing is available in various diameters and wall thicknesses, either seamless or welded. Ultimately, the best choice for your application will depend on its intended use.

Hollow/Mother Tube

Seamless stainless steel tubing is a widely-used material in the manufacturing industry. It can be produced using various methods, but welding is the most popular.

Welded tubing is created by rolling strips of stainless steel into a tube shape and then welding the seam longitudinally. This creates an extremely durable and strong tube that resists corrosion.

Hot forming and cold forming are both viable methods for producing metal products, with each producing distinct results. Cold forming offers smoother finishes with tighter tolerances than hot forming but requires additional steps in the production process which may add to product cost.

For small diameter tubing, drawing is often the preferred method to achieve size reduction. In this process, the mother tube is crimped on one end so it can be grasped easily, then pulled through a narrow die that has been specially tailored to meet predetermined dimensions.

Another method for fabricating seamless tubing is through a mandrel mill. This procedure utilizes multiple roller arrangements that keep the piercer in its central position during both piercing and elongation rolling of the billet.

After the piercing and elongation processes are completed, the billet is heated to form a hollow shell. This shell then inserts into a mandrel bar where it undergoes several sets of elongation rolls that reduce its wall thickness to the desired size.

Mandrel milling typically utilizes five roll stands in both upstream and downstream positions. As these materials pass through various elongation rolls, their temperatures decrease; this can cause the shell to adhere to the mandrel bar during movement.

This problem can be avoided by installing at least one 2-roll stand in both upstream and downstream stands, including a final stand that reduces the hollow shell’s wall thickness to desired length. Doing this ensures high precision when producing mother tubes from alloys with high thermal expansion coefficients.


Stainless steel tubing is the ideal material for structural applications due to its strength and corrosion resistance. It also looks good, making it suitable for transporting liquids, gases and chemicals. As it’s seamless, there are no weak spots which reduces the risk of leaks or tears.

When fabricating stainless steel tubing, several techniques are employed: extrusion, pistol grinding and cutting. Of these processes, extrusion produces the most standardized OD (outside diameter) and ID (inside diameter) tubes.

Extrusion is a manufacturing process wherein a continuous stream of hot metal is formed into a tube and drawn through a die, lengthening its diameter while decreasing its diameter.

This process can be employed to produce long, straight lengths of tubing or coils of tubing depending on the application requirements. It may also be employed in creating smaller parts for specific uses.

Another technique is rod drawing, which uses a hardened steel mandrel and tube that are drawn through a die to reduce their outside diameter and wall thickness. This method produces larger reductions than other methods.

Finally, cold reduction can be employed to create long straight lengths and coils that have been rolled down in the direction of their cross section. This method may be a cost-effective way to produce many identical straight pieces.

Pilgering is a process for producing stainless steel tubing that involves puncturing the hollow/mother tube with a piercer to give it a smooth exterior surface. After rolling down to its final form, this tubing is burnished inside and outside by means of a sizing mill.

This method can be an economical way to produce numerous straight lengths and coils. Typically, this produces long stretches of seamless tube in coil form.

Pilgering can be accomplished using various types of stainless steel, such as 304 and 347. 304 stainless steel is a mild carbon steel that stands out for its superior corrosion resistance and high strength. Furthermore, it’s highly ductile – making it suitable for various structural uses.

Cold Rolling

Stainless steel tubing is a widely-used product in various applications due to its superior corrosion resistance and ability to withstand extreme pressures. Furthermore, this strong material can be molded into various shapes with ease.

Seamless stainless steel tube is created through the extrusion process. This involves taking a solid billet of stainless steel from the machine and extruding it into a hollow form. This hollow billet then forms into oblong circular molds which are heated in a piercing mill before hollowing while hot for twenty times greater elongation of the molds, producing the seamless tube shape.

After this, further processing may be required to create the desired tube. Depending on its intended use, additional steps such as laser cutting or welding may be employed for optimal results.

Once stainless steel tubes have been formed into tubes, they must be checked to guarantee they meet all required dimensions (outside diameter, inside diameter and wall thickness). Once these dimensions have been confirmed, lubricating both outside and inside diameters with a specialized lubricant is applied; this lubricant then gets degreased during annealing preparations.

Next, the stainless steel tube is rolled in a continuous pipe rolling mill to reduce its outside and inside diameters and increase wall thickness. This saves money on long stainless steel tubes and coils as well as time spent annealing preparations.

Another method for decreasing the wall thickness and inside diameter of long lengths of tubing is cold reduction. This advanced process utilizes special machines with specially designed rolling dies to shrink stainless steel coils and long tubes to their required sizes using a one-step method rather than multiple steps, producing longer straight pieces.

Final step is to draw the tube over a mandrel to achieve desired shape and size. This step provides extra support during drawing, which prevents wrinkling during the procedure. This can be done using either an electromechanical or mechanical device known as a draw over mandrel machine – the most efficient and precise way to draw tubes for smaller sizes as well as larger ones.

Cold Drawing

Cold drawing is a manufacturing process that begins by piercing hot rolled steel bar stock to produce tubes with improved physical characteristics such as greater uniformity in outside diameter and inside diameter, increased machinability, higher strength, tighter tolerances and better microstructure uniformity. It finds applications in heat exchangers and bearings for automobiles, trucks, aircraft and construction projects alike.

For certain applications of stainless steel tubing, manufacturers may choose to cold draw it either before or after welding. Cold drawn tubes tend to have a cleaner surface finish and less risk of pitting or corrosion than their welded counterparts do.

The cold drawing process is an essential step in producing the finished product and can be utilized to create tubes with various diameters. Additionally, it’s employed for creating specialized tubing for various applications.

A stainless steel tube can be drawn using either a long or short mandrel. This small metal piece is inserted into the tube for extra support so it doesn’t wrinkle during drawing.

After inserting the mandrel into a tube, it is pulled through a die that is slightly smaller in diameter than the finished tube’s finished size. This process can be repeated several times to achieve the desired tube shape.

In order to reduce stress in a tube after it has been immersed in water, an annealing step is usually followed. This can be done either under controlled atmosphere or vacuum conditions and helps ensure the desired final product thickness is achieved.

Seamless stainless steel tubing is a popular choice for many industrial applications due to its durability, strength and resistance to corrosion. It often finds application in high-pressure or corrosive environments like oil and gas production or transport.

When it comes to stainless steel tubing, there are several types available. Welded tubes may be easier to work with due to their fine weld seam and tight tolerances; however, they have more limitations.

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