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Stainless steel is recognized for its strength, beauty, and resistance to corrosion. However, not all stainless steel is alike. The metal comes in five distinct families and about 150 different grades.
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.
Use for both low and high-temperature 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; cookware is also manufactured from Austenitic stainless steel.
Type 304, 304L, 316, and 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 |
Ferritic stainless steel
Ferritic stainless steel is magnetic and contains high carbon; therefore, it is brittle and has relatively poor corrosion resistance as compared to 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, and furnace application, where high chloride content is there.
Type 409, 430, 439, 444, and 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 is used in the manufacturing of sports knives and multi-purpose tools.
Type 405, 410, and 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 |
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 is 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.
Because of its 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, and S32760 are Duplex and Super Duplex stainless steel examples. 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 |
Commonly used stainless Steel ASTM Material Grades
ASTM A1016-04a Standard specification for general requirements for ferritic alloy steel, austenitic alloy steel, and stainless steel tubes
ASTM A213 Seamless ferritic and austenitic alloy steel boiler, superheater and heat exchanger tubes
ASTM A240 Standard Specification for chromium and chromium-nickel stainless steel pipe for pressure vessels and for general applications
ASTM A268 Seamless and welded ferritic and martensitic stainless steel tubing for general service
ASTM A269 Seamless and welded austenitic stainless steel tubing for general service
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
