Stainless steel is an iron alloy with resistance to staining and rusting in many environments where steel would typically degrade. The chemical composition of each grade creates a grain structure that falls into one of five classes: austenitic, duplex, ferritic, martensitic, and precipitation hardening. The austenitic class contains the most formable , weldable, and corrosion-resistant stainless steel grades.
TYPE
Describe
200 Series—austenitic
chromium-nickel-manganese alloys
201
austenitic
that is hardenable through cold working
300 Series—austenitic
chromium-nickel alloys
301
highly
ductile, for formed products. Also hardens rapidly during mechanical working.
Good weldability. Better wear resistance and fatigue strength than 304.
302
same
corrosion resistance as 304, with slightly higher strength due to additional
carbon.
304
the
most common grade;
the classic 18/8 (18% chromium, 8% nickel) stainless steel.
the Japanese equivalent grade of this material is SUS304.
304L
same
as the 304 grade but lower carbon content to increase weldability. Is
slightly weaker than 304.
316
the
second most common grade (after 304); for food and surgical stainless steel
uses; alloy addition of molybdenum prevents specific forms of corrosion. It
is also known as marine grade stainless steel due to its increased resistance
to chloride corrosion compared to type 304. 316 is often used for building
nuclear reprocessing plants.
316L
is
an extra low carbon grade of 316, generally used in stainless steel watches
and marine applications, as well exclusively in the fabrication of reactor
pressure vessels for boiling water reactors, due to its high resistance to
corrosion. Also referred to as "A4" in accordance with ISO 3506
321
similar
to 304 but lower risk of weld decay due to addition of titanium. See also 347
with addition of niobium for desensitization during welding.
630
is
most common PH stainless, better known as 17-4; 17% chromium, 4% nickel.
400 Series—ferritic and
martensitic chromium alloys
600 Series—originally created
for proprietary alloys, which are no longer given SAE grade number
1.Tensile strength, used to indicate the material’s overall strength, is the peak stress it can withstand before it breaks.
2.Corrosion resistance describes the material's ability to prevent deterioration caused by atmosphere, moisture, or other medium.
3.Toughness describes the material's ability to absorb energy before breaking.
4.Hardness (commonly measured as indentation hardness) describes its resistance to permanent surface deformation.
5.Formability indicates how easily the material can be permanently shaped. Magnetism characterizes how much the material is repelled by or attracted to a magnet.
