2018-02-28

Stainless Steel * Knowledge

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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.