The Five Types of Carbon Steel Round Tube

The Five Types of Carbon Steel Round Tube

When it comes to steel manufacturing, one type has the lion’s share of the market: by volume, carbon steel accounts for 90% of the steel produced each year. The increasing growth of the oil and gas industry means carbon steel tube and pipe are in constant demand, with over 50% of all steel tube and pipe being used for petrochemical production. Carbon steel’s ability to withstand corrosion and extreme environmental conditions makes it an excellent choice for parts used in oil and gas processing, from drilling to refining and transport.

Round Tube
While tube may look similar to pipe, the two shapes are used for different purposes. Pipe is used to transport substances such as oil and gas, while tube is used as a structural element. For this reason, tube is generally made to be stronger and more robust than pipe. Tube can also come in a variety of shapes such as round, square, or rectangular. When carbon steel round tube is needed, there are five types available for use:

Electric Resistance Welding (ERW)
Produced from cold-formed coil made of low carbon steel, this method uses electric resistance welding to form it into round tube. The welding itself can be done in several ways, but most often through an automated process. This means high quality ERW tube can be produced at a low manufacturing cost, making it a very popular choice for customers.
ERW tube’s affordability and versatility leads to it being used in many applications including automotive frames, supports and stands, and internal machine components.

Cold Drawn Seamless (CDS)
CDS tube starts with steel billets, heated to an extremely high temperature and pierced with machinery to create the tube’s hole. The steel is then rolled to elongate the tube and shrink its diameter, and cooled once it has been formed to the desired shape. This process results in very sturdy tube with thick walls and a smooth surface.
Because CDS tube is not only strong but aesthetically attractive, it is often used for visible automotive parts such as roll bars and frames. Other common uses include hydraulic cylinders, infrastructure columns, and boiler tubing.

Drawn-Over-Mandrel (DOM)
This type of tubing is produced through machining with the use of mandrels. A mandrel is a taper bar, used to gradually increase the diameter of a part placed on it – such as the small mandrels used by jewelers to resize and widen rings. For round tubing, steel coil is sheared and joined by welding, then finished by using mandrels. This machining creates high-quality tube with excellent levels of hardness, strength, and consistency.
DOM tube is used extensively in the automotive industry, found in parts including shock absorbers, dampeners, and seat frames. It is also regularly used in hydraulic parts such as pumps and cylinders.

This type is manufactured to meet the necessary requirements of hydraulic lines, including the strength to withstand the stress of containing pressurized fluids. Similar to CDS, hydraulic starts with carbon steel bars which are heated, pierced, and rolled until it results in sturdy tubes. Hydraulic tube has a very shiny and bright finish which makes it appealing for its aesthetic quality as well as its overall strength and utility.
Due to its high degree of strength, hydraulic tube can also be used for applications where tubes will be bent or fitted together.

Hot Finished
Also known as seamless tube, this type is made by piercing and rotating an extremely hot piece of carbon steel. The rotation creates the shape, and it then goes through a series of mills to reduce the tube’s diameter and wall thickness. This fairly low-cost process creates a versatile, easily machinable tube. However, hot finished tube sizing tends to be less precise than other types, and its finish looks rougher. For this reason, hot finished tube is typically found in applications where aesthetics or size variance are unimportant.
Seamless tube can be found in heavy-duty uses such as construction and drilling equipment, pillars, and wind turbine components.