Stainless steel tubing is one of the most versatile metal alloy materials used in manufacturing and fabrication. The two common types of tubing are seamless and welded. Deciding between welded vs. seamless tubing primarily depends on the application requirements of the product. In choosing between the two keep in mind that first the tubing must be compliant with your project specifications and that secondly, it must meet the conditions for which the tubing will ultimately be used.

Seamless Tubing Manufacturing

Knowing that distinction can also help in determining which tubing is best for a given application, welded or seamless. The method of manufacturing welded and seamless tubing is evident in their names alone. Seamless tubes are as defined – they do not have a welded seam. The tubing is manufactured through an extrusion process where the tube is drawn from a solid stainless steel billet and extruded into a hollow form. The billets are first heated and then formed into oblong circular molds that are hollowed in a piercing mill. While hot, the molds are drawn through a mandrel rod and elongated. The mandrel milling process increases the molds length by twenty times to form a seamless tube shape. Tubing is further shaped through pilgering, a cold rolling process, or cold drawing.

Welded Tubing Manufacturing

A welded stainless steel tube is produced through roll forming strips or sheets of stainless steel into a tube shape and then welding the seam longitudinally. Welded tubing can be accomplished either by hot forming and cold forming processes. Of the two, cold forming results in smoother finishes and tighter tolerances. However, each method creates a durable, strong, steel tube that resists corrosion. The seam can be left beaded or it can be further worked by cold rolling and forging methods. The welded tube can also be drawn similar to seamless tubing to produce a finer weld seam with better surface finishes and tighter tolerances.

Choosing Between Welded and SeamlessThere are benefits and drawbacks in choosing welded vs. seamless tubing.

Seamless TubingBy definition seamless tubes are completely homogenous tubes, the properties of which give seamless tubing more strength, superior corrosion resistance, and the ability to withstand higher pressure than welded tubes. This makes them more suitable in critical applications in harsh environments, but it comes with a price.

Benefits

StrongerSuperior corrosion resistanceHigher pressure resistanceApplications

Oil and gas control linesChemical injection linesBelow sea safety valvesChemical processing plant steam and heat trace bundlesFluid and gas transferWelded TubingWelded tubing is generally less expensive than seamless tubing due to the simpler manufacturing process in creating welded tubing. It is also readily available, like seamless tubing, in long continuous lengths. Standard sizes can be produced with similar lead times for both welded and seamless tubing. Seamless tubing costs can be offset in smaller manufacturing runs if less quantity is required. Otherwise, though custom sized seamless tubing can be produced and delivered more quickly, it is more costly.

Benefits

Cost-efficientReadily available in long lengthsFast lead timesApplications

Architectural applicationsHypodermic needlesAutomotive industryFood and beverage industryMarine industryPharmaceutical industryCosts of Welded vs SeamlessCosts of seamless and welded tubing are also related to such properties as strength and durability. Welded tubing’s easier manufacturing process can produce larger diameter tubing with thinner wall sizes for less. Such properties are more difficult to produce in seamless tubing. On the other hand, heavy walls can be achieved more easily with seamless tubing. Seamless tubing is often preferred for heavy wall tubing applications that require or can withstand high pressure or perform in extreme environments.

A number of factors combine to make stainless steel tubing an excellent choice for structural applications in industries ranging from automotive and aerospace to medical and marine. If you’re still unsure which tubing is best for your application, as a point of reference, though seamless tubing can be substituted for welded tubing, welded tubing can never be substituted for seamless tubing.