Stainless steel material consists of chromium, carbon, and steel alloys. Available in a very small amount, around 10.5%, chromium still serves a very important purpose by making the stainless steel corrosion-resistant. This is the quality for which stainless steel is popular. Apart from that, there are also many other qualities for which manufacturers use them in many applications. Some of these qualities include oxidation resistance, low-maintenance, and its harmless nature for other metals. Stainless steel is especially used for steel tube and steep pipes manufacturing.
There are different types of stainless steel tubing according to the final use of the tube. Today, we’ll discuss different types of steel tubes. We will also take a look at the application areas where steel tubing works. Let’s begin the discussion by talking about the different types of steel tubing.
Different Stainless Steel Tube and Steel Pipe Types
Sometimes, it is a little difficult to distinguish between a steel tube and a steel piping. However, you can classify them according to their function. Apart from the function, you can also distinguish stainless steel material by grade and type. Let’s take a quick look at the various types available.
304 Steel Pipes
304 stainless steel pipes are very popular for piping and tubing because of their corrosion and chemical resistance properties. But, a 304 steel pipe will not be compatible in areas where the temperature is anywhere around 800F - 1640F. This is because the 304 steel tube or pipe susceptible to the phenomena of carbide precipitation. However, the 304L type can evade this issue with its lower limit of carbon content. Therefore, you can consider 304L for higher temperature and welding applications.
Other stainless steel types often hold additives, like molybdenum or nickel, which strengthen the steel. Because of this, steel becomes a great option for many applications.
Steel Tubing/Piping for Corrosion Resistance
This steel category is suitable when you need a steel tube or pipe option that offers better corrosion resistance. Martensitic or ferritic steel types (those containing most chromium) can be heat-annealed or treated. Austenitic steels (steel with high nickel and chromium contents) offer superior resistance and can be a perfect alternative to Martensitic and ferritic steels.
Pressure Pipe
Stainless steel pressure pipes consist of a combination of nickel and chromium or solid chromium. Different types of steep pressure pipes are:
- Welded and seamless pipes
- Electrofusion Welded (EFW) steel pipes
- Welded large diameter pipes
- Welded ferritic and seamless and austenitic steel pipes
All these types of pressure steel pipes and tubes are appropriate for different applications. We will talk about these types in detail in our next article.
Stainless Steel Tubing for Sanitary Purposes
When a stainless steel tube or pipe comes in contact with sensitive products such as food and water, sanitation becomes important. Steel sanitary tubes and pipes are suitable for such applications because they resist corrosion, easy to clean, and do not tarnish. You can achieve different tolerances for certain applications. Typically, the ASTM A270 grade is appropriate for such applications.
Mechanical Stainless Steel Tubing
Mechanical stainless steel has its use in different applications, like bearings, cylinders, and hollow formed components. Various cross-sectional shapes can be made by manipulating tubing. Therefore, you can easily achieve shapes, like rectangular, square, and round tubing. Normally, A554 and ASTM A511 grades are the grades for applications that require mechanical tubing.
Steel Aircraft Tubes
Nickel and chromium-based steel types are suitable types to use in high-end aircraft applications. These tubes are suitable for such applications because of the traits like corrosion and heat-resistance. You can find these tubes in applications where high-strength is the primary trait.
Steel aircraft tubes can be welded or work-hardened. However, you cannot use work-hardened parts with corrosive substances. For a welded part, low-carbon steels are a traditional choice. For applications that need welded and seamless steel tube in bigger sizes, the manufacturers use structural aircraft tubes. This stainless steel type is made as per MIL Specs or AMS specifications.
Line Tubing – Aircraft Hydraulic
This is another aircraft tubing type you will see commonly in aircraft applications as hydraulic systems and fuel injection tubes. These tubes are usually smaller and made from a 304L or 304 stainless steel type. They are smaller due to their ductility, corrosion-resistance, and high strength.
Stainless Steel Tube Applications
A variety of plumbing applications are using stainless steel tubes. There are various reasons behind this. First of all, stainless steel material is very sturdy, which is made of 10-20% chromium and 80-90% steel. Steel tubes are capable of handling different water pressures on plumbing structures.
Furthermore, the steel surface doesn’t permit bacteria or particles to adhere. Therefore, the purification process would not allow unintentional detritus. Lastly, stainless steel doesn’t contaminate water. Steel tubing is also a popular ingredient of all structural applications, like residential and industrial construction. Instances include gates, playgrounds, athletic equipment, railings, and fences.
Steel is a better option than other metals, such as aluminum for construction tubing because such applications require additional stress resistance. Another common use of a steel tube includes the manufacturing of automotive and furniture parts.
Manufacturing of Stainless Steel Tubes
Various methods are available to manufacture steel tubing. Available methods also help classify different types of steel tubing. Those methods include seamless, ERW, and DOM. Let’s take a quick look at the three methods of stainless steel tubes manufacturing:
1. Seamless
Seamless steel tubing uses an extrusion method for production. You can form extruded tubes in a cold or hot process. The long section of steel bars forces the die that is blocking the desired tube shape.
2. ERW (Electric-Resistance-Welded)
In this method, a steel-rolled sheet passes through a couple of weld rollers. The circumference of weld rollers has a covering of the groove through which steel roll moves. The metal part in contact welds through heating using an electric current that melts the metal. ERW has extensive use in making steel pipes as well as assemblies of automobile bodies.
3. DOM (Drawn-Over-Mandrel)
The mandrel is the small metal piece that the manufacturer injects into the steel tube for defining a specific shape. It offers additional support to the tube for preventing unnecessary crumpling during drawing. The tube goes through the die, which has a comparatively smaller diameter as compared to the existing tube size. The tube shrinks and matches the die diameter size once drawn. This process permits tight specifications and tolerances. This is a highly adopted method for steel pipes and tube manufacturing.
All the above-mentioned manufacturing processes help manufacturers form different tube sizes and shapes. It is important to know that tubes or pipes are bound to be cylindrical. Manufacturers can make them in polygonal, square, or triangle shapes. A stainless steel pipe or tube intended for a specific application needs extra processes like laser tube cutting. Hydrogen has reactive properties that may cause explosions or metal embrittlement. So, applications that involve hydrogen need to be pre-cleaned or must be instrument grade.
In general, the manufacturing process of the steel tube is selected according to its communication with the steel type to use. There are specific steel types that poorly react to heat due to their carbon content. In that case, the steel welding will become hard. The type of steel also plays an important role in making decisions about their utilization in unstable applications.
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