Stainless Steel Classifications
Stainless steels are in general grouped into
- martensitic stainless steels
- ferritic stainless steels
- austenitic stainless steels
- duplex (ferritic-austenitic) stainless steels
- precipitation-hardening stainless steels
Alloying metallic elements added during the making of the steel increase corrosion resistance, hardness, or strength. The metals used most commonly as alloying elements in stainless steel include chromium, nickel, and molybdenum.
Stainless steels are available in the form of
- plate
- sheet
- strip
- foil
- bar
- wire
- pipes
- tubes
Stainless steels are a iron-based alloy containing at between 10.5% to 30% Cr. Stainless steel achieve its stainless characteristic through the formation of an invisible and adherent chromium-rich oxide surface film.
Other alloying elements added to improve the characteristics of the stainless steel include nickel, molybdenum, copper, titanium, aluminum, silicon, niobium, nitrogen, sulphur, and selenium.
Carbon is normally in amounts from 0.03% to more than 1.0% in some martensitic grades.
Selection of stainless steels are in general based on
- corrosion resistance
- fabrication characteristics
- availability
- mechanical properties for specific temperature ranges
- product cost
Since stainless steel resists corrosion, maintains its strength at high temperatures, and is easily maintained, it is widely used in items such as automotive and food processing products, as well as medical and health equipment. The most common US grades of stainless steel are:
TYPE 304
The most commonly specified austenitic (chromium-nickel stainless class) stainless steel, accounting for more than half of the stainless steel produced in the world. This grade withstands ordinary corrosion in architecture, is durable in typical food processing environments, and resists most chemicals. Type 304 is available in virtually all product forms and finishes.
TYPE 316
Austenitic (chromium-nickel stainless class) stainless steel containing 2%-3% molybdenum (whereas 304 has none). The inclusion of molybdenum gives 316 greater resistance to various forms of deterioration.
TYPE 409
Ferritic (plain chromium stainless category) stainless steel suitable for high temperatures. This grade has the lowest chromium content of all stainless steels and thus is the least expensive.
TYPE 410
The most widely used martensitic (plain chromium stainless class with exceptional strength) stainless steel, featuring the high level of strength conferred by the martensitics. It is a low-cost, heat-treatable grade suitable for non-severe corrosion applications.
TYPE 430
The most widely used ferritic (plain chromium stainless category) stainless steel, offering general-purpose corrosion resistance, often in decorative applications.
| Type | Equivalent UNS |
|---|---|
| 201 | S20100 |
| 202 | S20200 |
| 205 | S20500 |
| 301 | S30100 |
| 302 | S30200 |
| 302B | S30215 |
| 303 | S30300 |
| 303Se | S30323 |
| 304 | S30400 |
| 304L | S30403 |
| 302HQ | S30430 |
| 304N | S30451 |
| 305 | S30500 |
| 308 | S30800 |
| 309 | S30900 |
| 309S | S30908 |
| 310 | S31000 |
| 310S | S31008 |
| 314 | S31400 |
| 316 | S31600 |
| 316L | S31603 |
| 316F | S31620 |
| 316N | S31651 |
| 317 | S31700 |
| 317L | S31703 |
| 317LMN | S31726 |
| 321 | S32100 |
| 330 | NO8330 |
| 347 | S34700 |
| 348 | S34800 |
| 384 | S38400 |
| Type | Equivalent UNS |
|---|---|
| 405 | S40500 |
| 409 | S40900 |
| 429 | S42900 |
| 430 | S43000 |
| 430F | S43020 |
| 430FSe | S43023 |
| 434 | S43400 |
| 436 | S43600 |
| 442 | S44200 |
| 446 | S44600 |
| Type | Equivalent UNS |
|---|---|
| 403 | S40300 |
| 410 | S41000 |
| 414 | S41400 |
| 416 | S41600 |
| 416Se | S41623 |
| 420 | S42000 |
| 420F | S42020 |
| 422 | S42200 |
| 431 | S43100 |
| 440A | S44002 |
| 440B | S44003 |
| 440C | S44004 |
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Related Documents
AISI 310 Stainless Steel - Properties
Thermal diffusivity, specific heat capacity, density and thermal conductivity of stainless steel AISI 310 vs. temperature.
ASME/ANSI B36.10/19 - Carbon, Alloy and Stainless Steel Pipes - Dimensions
Pipe sizes, inside and outside diameters, wall thickness, schedules, moment of inertia, transverse area, weight of pipe filled with water - U.S. Customary Units.
ASTM A312 Stainless Steel Pipes - Bursting and Collapsing Pressures
Theoretic bursting and collapsing pressures for stainless steel pipes ASTM A312.
Carbon and Stainless Steel Flanges - ASME/ANSI Class 150
ASME/ANSI B16.5-1996 Pipe Flanges and Flanged Fittings - Class 150 Flanges - outside and inside diameters, bolt circles, numbers and diameters of bolts.
Copper, Ductile Iron, Carbon Steel, Stainless Steel and Aluminum Piping Materials - Temperature Expansion
Thermal expansion of typical piping materials.
PVC, CPVC, Carbon Steel, Stainless Steel and Fiberglass Pipes - Thermal Expansion Diagrams
Thermal expansion of PVC, CPVC, Carbon and Stainless Steel and Fiberglass pipes.
Stainless Steel - Comparing International Standards
Comparing international stainless steel standards from America (US), France, Germany, Italy, Japan, Russia, Spain, Sweden, England (UK) and the European Union.
Stainless Steel Pipes - Allowable Pressure vs. Schedule and Size
Allowable pressure for standard seamless A312-TP316/316L stainless steel pipes - temperatures 100oF to 750oF.
Stainless Steel Pipes - American vs. European Standards
American - US - vs. European - German, British (UK) and Swedish - stainless steel pipe standards.
Stainless Steel Pipes - Dimensions and Weights
Dimensions, wall thickness and weights of stainless steel pipes according to ASME B36.19 Stainless Steel Pipes.
Stainless Steel Weld Fittings - ANSI/ASME B36.19
Dimensions of stainless steel weld fittings according ANSI/ASME B36.19.
Stainless Steels - Corrosion Resistance
Corrosion resistanse of AISI stainless steels in various environments.
Stainless Steels - Identification Tests
Magnetic, spark, hardness and acid identification tests for austenitic, martensitic and ferritic stainless steels.
Steel Tempering Colors
The tempering process of hardening steel.
UNS - Unified Numbering System
The Unified Numbering System - UNS - used for metals and alloys.