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There are different types of stainless steel used in piping. After carbon steel, Stainless Steel is the second most widely used material in Process industries as it offers excellent corrosion resistance properties.

Stainless steel (SS) is a type of alloy steel with a minimum chromium content of 10.5% or more, and maximum carbon content of less than 1.20%.

SS has excellent resistance to corrosion and good ductility. Stainless steel becomes corrosion resistive due to the formation of non-reactive chromium oxide (Cr2O3) film on the surface. This film adheres tightly to the surface of the metal and this film acts as a barrier, therefore, protects metal from corrosion.

Types of Stainless Steel

Stainless Steel properties got changed when its microstructure changed. Based on this SS can be classified as follow;

  • Austenitic stainless steel
  • Ferritic stainless steel
  • Martensitic stainless steel
  • Precipitation Hardened stainless steel
  • Duplex / Super Duplex stainless steel

Austenitic stainless steel

  • Austenitic stainless steel is non-magnetic in nature and has very high corrosion resistance.
  • Excellent weldability, formability, fabricability and ductility.
  • High Corrosion resistance at temp up to 1500°F.
  • Usfull for both low and high temparture service.
  • This type of steel is hardenable by cold working.
  • It has a Face centered Cubic –FCC (fine grain structure) structure.
  • Possess high impact strength at low temp.
  • These types of SS are widely used in the process industry and a variety of industrial applications, cookwares are also manufactured from Austenitic stainless steel.
  • Type 304, 304L, 316, 316L are some of the examples of Austenitic stainless steel. Refer to the chart given below.
Grade Alloy Component Characteristics & Application
303 18Cr-8Ni-S Free cutting steel
304 18Cr-8Ni Basic steel grade. Use for general purpose steel for many applications in many fields
304H 18Cr-8Ni-High C
304L 18Cr-8Ni-Low C
304N 18Cr-8Ni-N High   strength
304LN 18Cr-8Ni-Low C-N lntergranular corrosion resistance
309 22Cr-12Ni Oxidation resistance. Use in Chemical plant pipes and tubes, Radiant tubes, Thermocouple protection tubes
309S 22Cr-12Ni
310 25Cr-20Ni
310S 25Cr-20Ni
312L 20Cr-18Ni-6Mo-0.2N Seawater resistance. Use in Seawater desalination plant pipes
316 18Cr-12Ni-2Mo Corrosion resistance. Use in LNG plant pipes, Boilers, nuclear power and chemical industry pipes and tubes
316H 18Cr-12Ni-2Mo-High C
316L 18Cr-12Ni-2Mo-Low C
316Ti 18Cr-12Ni-Mo-Ti lntergranular corrosion resistance
317 18Cr-12Ni-3Mo Pitting corrosion resistance. Use in Chemical tanker pipes
317L 18Cr-12Ni-3Mo-Low C
321 18Cr-9Ni-Ti Intergranular corrosion resistance. Use in Chemical plant pipes
321H 18Cr-9Ni-Ti-High C High-temperature strength. Use in Boiler heater tubes and reheater tubes
347 18Cr-9Ni-Nb lntergranular corrosion resistance. Use in Chemical plant pipes and tubes
347H 18Cr-9Ni-Nb-Low C High-temperature strength. Use in Boiler heater tubes and reheater tubes
310MoLN 25Cr-22Ni-2Mo-N lntergranular corrosion resistance. Use in Urea reactor tubes
Types of Stainless Steel

Ferritic stainless steel

  • Ferritic stainless steel is magnetic and contains high carbon, therefore it is brittle and relatively poor corrosion resistance than austenitic SS.
  • Non-hardenable by heat treatment.
  • Body-centered cubic -BCC (coarse grain structure).
  • Ferritic stainless steel has a high resistance to chloride stress corrosion cracking so it is used in marine, petrochemical, heat exchangers, furnace application, where high chloride content is there.
  • Type 409, 430, 439, 444, 446 are examples of Ferritic stainless steel. Refer to the chart given below.
Grade Alloy Component Characteristics & Application
430 18Cr Chloride corrosion resistance and stress corrosion crack resistance. Use in water heater pipes
444 19Cr-2Mo-Ti/Nb
446 25Cr-N

Martensitic stainless steel

  • Martensitic stainless steel has high hardness and poor corrosion resistance than austenitic SS.
  • Heat treatable to high hardness level.
  • Crystallographic form-distorted structure.
  • It used in the manufacturing of sports knives and multi-purpose tools.
  • Type 405, 410, 420 are examples of Martensitic stainless steel. Refer to the chart given below.
Grade Alloy Component Characteristics & Application
405 13Cr-AI Low thermal expansion. Use in automotive exhaust system pipes
410 13Cr
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Precipitation Hardened stainless steel

  • Precipitation Hardened stainless steel is magnetic and heat treatable to high strength, therefore it has a very high strength-to-weight ratio with good corrosion resistance.
  • It used in making aerospace components and springs.
  • 17-7PH, 17-4PH are examples of Precipitation Hardened stainless steel.

Duplex / Super Duplex stainless steel

  • Duplex and Super Duplex stainless steel contain both Austenite and Ferrite in the microstructure
  • Beacuse of it structure, this grade offers benefits of both Austenite & Ferrite stainless steel
  • Good resistance to pitting and crevice corrosion.
  • High strength and high resistance to stress corrosion cracking.
  • Used in the seawater system, heat exchanger, and structural application
  • EX- UNS S32205, S31803, S32760 are examples of Duplex and Super Duplex stainless steel. Refer to the chart given below.
Grade Alloy Component Characteristics & Application
329J3L 22Cr-5Ni-3Mo-0.15N High strength, high corrosion resistance. Use in various heat exchanger tubes
329J4L 25Cr-7Ni-3Mo-0.2N
S31500 18.5Cr-5Ni-2.7Mo
S32205 22.5Cr-6Ni-3Mo-0.2N
S32750 25Cr-7Ni-4Mo-0.3N High strength, high corrosion resistance. Use in seawater desalination plant pipes
Stainless Steel Heat Exchanger Tube Bundle and Tube Sheet

Commonly used stainless Steel ASTM Material Grades

  • ASTM A312 Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes
  • ASTM A358 Electric-Fusion-Welded Austenitic Chromium-Nickel Alloy Steel Pipe for High-Temperature Service
  • ASTM A376 Seamless Austenitic Steel Pipe for High-Temperature Central-Station Service
  • ASTM A409 Welded Large Diameter Austenitic Steel Pipe for Corrosive or High-Temperature Service
  • ASTM A451 Centrifugally Cast Austenitic Steel Pipe for High-Temperature Service
  • ASTM A790 Seamless and Welded Ferritic /Austenitic Stainless Steel Pipe
  • ASTM A813 Single- or Double-Welded Austenitic Stainless Steel Pipe
  • ASTM A814 Cold-Worked Welded Austenitic Stainless Steel Pipe
  • ASTM A872 Centrifugally Cast Ferritic /Austenitic Stainless Steel Pipe for Corrosive Environments
  • ASTM A928 Ferritic /Austenitic (Duplex) Stainless Steel Pipe Electric Fusion Welded with Addition of Filler Metal
  • ASTM A943 Spray-Formed Seamless Austenitic Stainless Steel Pipe
  • ASTM A949 Spray-Formed Seamless Ferritic /Austenitic Stainless Steel Pipe
  • ASTM A954 Austenitic Chromium-Nickel-Silicon Alloy Steel Seamless and Welded Pipe
  • ASTM A999 General Requirements for Alloy and Stainless Steel Pipe