4. What stainless steel grades are recommended for your intended application?
Stainless steels are consisting of a huge variety of iron bases alloys with a variety of properties and applications.
Generally spoken, stainless steel alloys are defined by containing a minimum of 10.5% chromium. Chromium serves to build a natural surface passivation which works as barrier and make the stainless steel more resistant to corrosion attacks.
Other elements are added and the chromium content increased to further improve the corrosion resistance and heat-resisting properties, enhance mechanical properties and provide specific fabrication characteristics.
The following may help you to choose the suitable alloy from our standard selection.
a) General information to our stainless steel selection
- 201 sheets and coils
- 304 sheets and coils
- 316 sheets and coils
- 430 sheets and coils
Further stainless steel grades are available on request, but not further explained here.
201 grades sheets and coils:
201 grades are not standardized for sheets and coils. But there are several specific alloys such as 201L1, 201L4, 201LH, 201LJ and more available on the market.
The special feature of 201 grades is the substitution of nickel with manganese within the alloy which makes this grade cheaper to 304 and 316 grades, while it's still austenitic in character with mechanical properties similar or tougher to 304 and 316.
* Corrosion resistance:
201 grades have a high resistance to acid and alkali, but come with a somewhat lower pitting corrosion resistance to 430, 304 and 316.
* Mechanical properties:
201 features high toughness and hardness, ranging from values similar about 304 and 316 to higher values.
* Fabrication:
The aim of this grade is to feature similar properties to 304 and 316 while the price is lower. It's easily formed and machined.
* Application:
The application ranges from decorative tubes, tensile products and covers and watch cases. It's frequently requested for indoor architecture applications.
304 grades sheets and coils:
Grade 304 is the most commonly used stainless steel. It is an austenitic, corrosion resistant steel with excellent strength, toughness, fabrication characteristics and weldability.
* Corrosion resistance:
Grade 304 has excellent corrosion resistance. It gives good service in atmospheric conditions, resisting most environmentsexcept for marine conditions, or where industrial pollution is heavy.
304 grade steel may face stress corrosion under certain conditions.
* Mechanical properties:
304 features high toughness and hardness.
* Fabrication:
Grade 304 is readily workable by the standard methods of sheet metal working, with the exception that it cannot be oxygen cut. Plasma cutting is normal.
It is relatively easy to machine and has excellent weldability.
* Application:
Typical applications are transport and storage equipment, kitchen furniture, equipment and appliances, architectural panelling, railings and trims.It's possible to use 304 grades outdoors in mild climate areas which are located away from shores and factory sides.
316 grades sheets and coils:
Grade 316 is an improved version of 304. The addition of molybdenum and a slightly higher nickel content gives this grade a much increased corrosion resistance in many aggressive environments.
* Corrosion resistance:
Grade 316 has excellent corrosion resistance. It gives good service in atmospheric conditions, resisting most environments. It is often used in marine conditions, or where industrial pollution is heavy.
Similar to 304, 316 grade steel may face stress corrosion under certain conditions.
* Mechanical properties:
316 features high toughness and hardness.
* Fabrication:
Grade 316 is readily workable by the standard methods of sheet metal working, with the exception that it cannot be oxygen cut. Plasma cutting is normal.
It is relatively easy to machine and has excellent weldability.
* Application:
Typical applications are food processing equipment, laboratory equipment, architectural panelling, railings and trims, boat fittings and chemical containers. It's possible to use 316 grades outdoors in mild climate areas as well in harsh climate areas such as shores and factory sides.
430 grades sheets and coils:
Ferritic 430 grade is cheaper than any of the 300 series steels while it has good corrosion resistant, has resistance to heat and oxidation and is not susceptible to stress corrosion cracking.
* Corrosion resistance:
Grade 430 has good corrosion resistance in oxidizing acid solutions such as nitric acid. The resistance to pitting and crevice corrosion is a little lower than that of Grade 304. Thus 430 grade steels serve good in mild environments.
Grade 430 is resistant to stress corrosion cracking and may be used where grade 304 might fail in this mode.
* Mechanical properties:
Compared to 201, 304 and 316 grades 430 has a lower toughness and hardness, it has lower work hardening which enables easy bending and forming.
* Fabrication:
430 is readily workable by the standard methods of sheet metal working, with the exception that it cannot be oxygen cut. Plasma cutting is normal.
Grade 430 is slightly easier than the austenitic grade 304 to machine, but in contrast to 304 and 316 it has limitations in welding.
* Application:
430 is often used in interior appliances, including washing machine drums, kitchen sinks, and indoor panels such as refrigerator doors but also used in automotive.
As it is liable to brittle fracture at sub-zero temperatures it is not suitable in cryogenic applications.
b) Chemical composition data
Table 1: Chemical Composition of some standard alloys
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