An engineer’s guide to selecting the right steel tube

The engineer has many options when it comes to selecting the ideal steel tube for any application. Grades 304 and 316 stainless steel tubing are the most commonly used. However, ASTM also provides engineers with the best solution for their applications. By following specification guidelines, it meets budget goals while still providing the required performance over the life of the product.

Whether to choose seamless or welded
When selecting the tube material, it is important to know whether it should be seamless or welded. Seamless 304 stainless steel tubing is made from a recognised high quality material. Seamless tubes are manufactured by either extrusion, a high temperature shearing process, or rotational piercing, an internal tearing process. Seamless tubes are often offered for high wall thickness so that they can withstand high pressure environments.
A welded tube is formed by rolling a length of steel strip into a cylinder, then heating and forging the edges together to form a tube. It is also often less expensive and has shorter lead times.

ECONOMIC CONSIDERATIONS
Prices vary greatly depending on the quantity purchased, availability and OD-to-wall ratio. The supply and demand of foreign materials has pushed prices all over the place. Nickel, copper and molybdenum prices have all risen and fallen dramatically in recent years, with a significant impact on steel tube prices. As a result, extra care should be taken when setting long term budgets for higher alloyed alloys such as TP 304, TP 316, cupro-nickel and alloys containing 6% molybdenum. Low nickel alloys such as Admiralty Brass, TP 439 and the super ferritics are more stable and predictable.