AISI ASTM TP 304 304L 309S 310S 316L 316ti 321 347H 317L 904L 2205 2507 Inox Stainless Steel Seamless Tube

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 Seamless

There are benefits and drawbacks in choosing welded vs. seamless tubing.

Seamless Tubing

By 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

• Stronger
• Superior corrosion resistance
• Higher pressure resistance

Applications

• Oil and gas control lines
• Chemical injection lines
• Below sea safety valves
• Chemical processing plant steam and heat trace bundles
• Fluid and gas transfer

Welded Tubing

Welded 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-efficient
• Readily available in long lengths
• Fast lead times

Applications

• Architectural applications
• Hypodermic needles
• Automotive industry
• Food and beverage industry
• Marine industry
• Pharmaceutical industry

Stainless Steel Pipes Parameter