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Discussion in 'Off Topic' started by zixxer, Apr 6, 2007.
curious if anyone knows how to tell if a part is stainless
put a magnet on it . most stainless isn't magnetic
one tip: stainless isn't magnetic
that's not true.
Types of Stainless Steel
The three main types of stainless steels are austenitic, ferritic, and martensitic. These three types of steels are identified by their microstructure or predominant crystal phase.
Austenitic steels have austenite as their primary phase (face centered cubic crystal). These are alloys containing chromium and nickel (sometimes manganese and nitrogen), structured around the Type 302 composition of iron, 18% chromium, and 8% nickel. Austenitic steels are not hardenable by heat treatment. The most familiar stainless steel is probably Type 304, sometimes called T304 or simply 304. Type 304 surgical stainless steel is an austenitic steel containing 18-20% chromium and 8-10% nickel.
Ferritic steels have ferrite (body centered cubic crystal) as their main phase. These steels contain iron and chromium, based on the Type 430 composition of 17% chromium. Ferritic steel is less ductile than austenitic steel and is not hardenable by heat treatment.
The characteristic orthorhombic martensite microstructure was first observed by German microscopist Adolf Martens around 1890. Martensitic steels are low carbon steels built around the Type 410 composition of iron, 12% chromium, and 0.12% carbon. They may be tempered and hardened. Martensite gives steel great hardness, but it also reduces its toughness and makes it brittle, so few steels are fully hardened.
Take a steel screw/bolt of identical proportions. Stick each in water and expose to air. See which one rusts first
As a general rule the types that are magnetic are mostly used for cutlery and knives. Nuts and bolts are made of the non-magnetic alloys.
for the most part if it is stainless it will be stamped as such. If it is not, it likely isn't.
If the screw/bolt/nut is brand new, it will typically have a darker appearance (slightly) than a zinc coated screw/bolt/nut. Galvanized will have a very dull finish.
Pour water on it and wait a few weeks.
UUGGHHH, I just took an exam on this stuff for my materials engineering class, but I got raped on it.
Just look at it. It's easy to tell.
However, with respect to the stainless most commonly used in screws, bolts, and nuts, it is true.
dip it in grapejuice and see if it stains.
Dont know if this will help, but I will give it to you anyway.