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Understanding Round Steel Tubing: Types, Grades, and Applications

Steel tubing is a versatile construction material with a wide range of shapes, sizes, and grades available for various applications. While its impossible to cover every detail about steel tubing comprehensively, well focus on some key aspects to help you navigate this essential building component.

Variety of Steel Tubing

The world of steel tubing is vast, with countless variations based on dimensions, grades, and manufacturing processes. The availability of specific types can vary significantly depending on your location and suppliers. In this article, well shed light on one of the most commonly used and frequently inquired-about steel products: round steel tubing.

Standard Sizes and Specifications of round steel tubing

Round steel tubing is widely accessible and adheres to industry-standard sizes, typically defined by its inside diameter (ID), outside diameter (OD), and wall thickness. To find precise information on these dimensions, consult the supply catalog provided by your local supplier or refer to their technical database.

Generally, round steel mechanical tubing is ordered and supplied based on specified OD and wall thickness, with the ID determined by these specifications. However, there are exceptions, primarily in the case of true seamless tubing.

Manufacturing Processes of round steel tubing

Steel tubing undergoes various manufacturing processes, resulting in different characteristics. Here are the key methods:

1. Continuous (Butt Welded) Pipe Process: This method produces a wide range of pipe sizes from a few widths of skelp. Skelp coils are joined and continuously fed into the mill. After heating, the strip is formed into an arc, welded, and then reduced in size. Finally, the pipe is cut to length and undergoes sizing and cooling processes.

2. Electric Resistance Welded (ERW) Tube Process: In this process, steel strip is unwound, side-trimmed, cold-formed into a circular shape, and welded using electric resistance at high temperatures. The weld is tested for integrity, and the tubes dimensions are precisely controlled.

3. Drawn Over Mandrel (DOM): DOM starts as ERW tubing, which is then drawn over a mandrel. This cold working process significantly improves mechanical properties. DOM tubes are known for their strength and dimensional precision.

4. Seamless Tube Construction: Seamless tubing is created by extruding a solid steel bar at high pressure, resulting in a seamless tube shell. Its then hot-rolled and processed to achieve the desired dimensions and properties.

Types of Round Steel Tubing

Steel tubing comes in various forms, including:

1. Cold Drawn Seamless Steel Tube:

Expensive and specialized, true seamless tubing is rare in automotive and 4x4 applications. Its manufactured through an extrusion process and is either Cold Drawn Seamless (CDS) or Hot Finished Seamless (HFS).

2. Electric Resistance Welded (ERW) Tube:

ERW is the most economical and readily available option, produced through electric resistance welding. Its available as Hot Rolled ERW (HREW) or Cold Rolled ERW (CREW), with CREW offering better dimensional accuracy and surface finish.

3. Drawn Over Mandrel (DOM):

DOM tubing, despite technically referring to a process, is commonly used to describe high-quality ERW tubing drawn over a mandrel. It offers superior mechanical properties and is a preferred choice for many applications.

How to Selecting the Right Steel Tubing?

When choosing steel tubing, its essential to consider factors like the intended use, strength requirements, and budget. Additionally, be aware of variations in chemical content, heat treatment, and mechanical properties among suppliers. Specialized products, such as proprietary offerings, might also be available, so consult your supplier for specific options.

Lastly, be cautious about the condition of the steel tubing you purchase. Most carbon steel tubing is available in the annealed condition, which may not be suitable for all applications. Ensure that you select the right type of tubing to meet your projects needs.

In conclusion, Round steel tubing is a crucial building material with diverse options to suit various applications. Understanding the different types, manufacturing processes, and specifications will help you make informed choices for your projects.

Drawn Over Mandrel (DOM) Tube