Stainless Steel Tubes

STAINLESS STEEL TUBES

Material Specification	SS316 / TP316 SS316L / TP316L
Dimension Specification	ASTM A213/A269
Outer Diameter Size	4mm to 60mm 1/4"OD to 2"OD
Finishing	Polished 320 Grit Bright Annealed Annealed and Pickled (AP)

Stainless steel tubes are modeled after the American Society for Testing and Materials (ASTM) dimensional standards –ASTM A213 / A269. A213 tubes are made from a seamless process finished through a hot or cold process (based on specifications). These tubes are the standard specification used in heat-exchanger tubes, austenitic and Ferritic alloy-steel boilers, super-heaters, etc. Each tube produced is exposed to a series of tests after furnishing in a heat-treated condition. Some of the tests include hardness tests, flaring test, tension test, hydrostatic test, and nondestructive electric test.

The model dimension for welded austenitic and seamless stainless steel tubes used for general purposes is A269. The tubes' fishing is done in a heat-treated environment and, after that, subjected to mechanical tests like a nondestructive electric test, flange test, reverse flattening tests, hydrostatic test, flaring test, and hardness test.

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1. How is Stainless Steel Tubing made?

Stainless steel contains other elements such as manganese, silicon, molybdenum, nickel. Nickel and molybdenum are elements often added to the alloy to enhance the formability and anti-rust properties. It has a carbon content of less than 1.2% and a minimum of 10.5% chromium. Other elements are in various proportions depending on the chemical compositions of the steel. A thin layer of oxide is produced on the surface of the steel by chromium. This gives an anti-corrosion quality to the alloy.

Stainless steel types can be divided generally into four – Austenitic, Ferritic, Duplex, and Martensitic. Austenitic Stainless steel usually contains a high amount of nitrogen, molybdenum, chromium, and nitrogen. They are also very popular due to their strength, weld-ability, and flexibility. The combination of these elements increases the anti-corrosion quality in the alloy, and they are mostly used in the production of kitchen cutlery and others.

Ferritic Stainless Steel contains chromium and carbon content with the highest quantity of 0.10%. However, other elements are usually added to the alloy (especially molybdenum). They have a unique feature of being magnetic and are often used in making kitchen cookware and some industrial equipment.

SS316 / 316L Dual Specifications

2. What is the difference between Duplex and Stainless Steel Tube?

Matt Finish Stainless Steel Tubes Bundle

Stainless steel tubes are made from stainless steel, an alloy from iron and carbon. Tubes made from stainless steel have a lesser corrosion/rust rate even when exposed to water. Stainless steel tubes are produced in different thicknesses and shapes (rectangular, spherical, etc.), unlike many other tubes manufactured in circular form. Also, stainless steel tubes come with diverse surface finishes and grades to serve the customer or industry's needs.

Duplex Stainless steel combines both ferritic stainless steel and austenitic stainless steel. Also, they have less nickel, which makes it able to withstand saltwater for a long time. Thus, they are used in the underwater oil industry. Martensitic Stainless Steel has a carbon percentage of about 1% and is similar to ferritic stainless steel in the structure. Martensitic stainless steel is often used in the production of valves and pumps due to its high strength.

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3. What is Stainless Steel Tubes used for?

Stainless steel tubes are used for several purposes by different institutions. Here’s a list of some uses of stainless steel tubes (SS316/SS316L):

Household Equipment	Stainless steel tubes are used in some household equipment because of its anti-rust properties. For example, gas lines are often made from stainless steel as it prevents gas leaks. Also, stainless steel tubes can be found in refrigerators and other cooling appliances.
Automobiles	Stainless steel tube is gaining more relevance in the automobile industry due to its high corrosion resistance, durability, and dent performance. Also, it contributes to the overall weight of the finished automobile. From the Automotive Stainless Tube Market Size, Share & Trends Analysis Report, the market size for the global automotive stainless steel tube in 2015 was estimated as USD 3.37 million, and the growth level is predicted to be 3.9% from 2016 – 2024. It can be found in aircraft hydraulic lifts, diesel spark plugs, filter systems, fuel lines, motor block reheating, auto mufflers, and many more.
Industries	Stainless steel tubes are used in water corporation systems for purification purposes. For construction industries, these tubes are used to give structural support for buildings. Generally, stainless steel tubes are necessary for many milling machines, production lines, etc.
Weapons	Stainless steel tubes are also used in the production of some military and nuclear weapons.

4. What are the grades of Stainless Steel Tubes?

Stainless steel tubes can be finished using three different methods – Bright Annealed, Annealed and pickled, and Polished 320 grit.

Bright Annealed Stainless Steel tubes are tubes finished by exposing the steel to a closed furnace with gases such as hydrogen and others. After that, the material is rapidly cooled. These tubes are very high with anti-rust quality, smooth, and have a shiny surface area.

Annealed and Pickling Method (AP) is another form of finishing for stainless steel tubes. During Pickling, an acid material is produced for the material. This is done to remove oxides on the material constructed after the annealing process, thus restoring the natural anti-corrosion nature.

Pickled stainless steel has not less than a minimum molybdenum quantity of 2%, and the finished stainless steel has a shiny surface.

SS316 / SS316L Tubes

5. Tolerance chart for Stainless Steel Tube

The Stainless Steel tubes SS316/SS316L are of MO2.0 and MO2.5 specification. MO2.5 tubes have a minimum of 2.5% of Molybdenum, increasing the corrosion resistance of the material. The combination of these two tubes is used in the oil and gas industries.

Tube Outer Diameter	4mm to 35mm	> 35mm to 38mm	> 38mm to 60mm	> 60mm
Tolerance	+/- 0.08mm	+/- 0.15mm	+/- 0.20mm	+/- 0.25mm

.Above is a tolerance chart for the ASTM A213/A269 stainless steel tubes.

ASTM A213	Minimum Wall Thickness	Maximum Wall Thickness
Minimum Wall Thickness (MWT)	0 %	20 %
Average Wall Thickness (AWT)	10 %	10 %

The stainless tubes A269 and A213 have precise wall thickness tolerance. The permissible wall thickness variations for A269 are calculated as +/-10%. For the A213 steel tube, the table above shows its wall thickness tolerance.

Our standard value for wall thickness is +/- 10%, compliance with the ASTM standards. For the general market, average wall thickness is often opted for. However, values for minimum wall thickness can be provided upon request.

6. How can you bend Stainless Steel Tubes?

Matt Finish Stainless Steel Tubes

Stainless steel tubes can be bent using different methods. However, during this process, ensure proper care is taken to avoid contamination from carbon on the steel. One of the easiest ways of bending this material is using a section bender or three-roll bender. This method is mostly used when the metal has a large radius.

For stainless steel tubes with a tight radius, a rotary-draw bender can be utilized. The process of bending stainless steel tubes with the rotary-draw bender is called Mandrel Tube Bending.

You also have to take cognizance that an error during bending could affect the tubing surface area, leading to difficulty in installation.