3 methods to identify the stainless steel 304 and 316

- Jun 14, 2019-

  1. Identification by color. 

ss 304 Identification by color

Pickled stainless steel, surface color silver-white clean: chromium-nickel stainless steel color silver-white jade color; chromium stainless steel color white slightly gray luster; chromium manganese nitrogen stainless steel color and chromium-nickel stainless steel similar light color. 

The surface color of stainless steel without pickling: chromium-nickel steel is brown and white, chromium steel is brown and black, chromium manganese nitrogen is black (these three colors relate to the color of heavy oxidation). 

Cold rolled unannealed chromium-nickel stainless steel makes a silver-white reflective surface. 


2.Identification by the magnet. 


ss 304 Identification by magnet

Magnets can basically make a distinction between two types of stainless steel. 

Because chromium stainless steel can be attracted by magnets in any state; chromium-nickel stainless steel is generally non-magnetic in the annealing state, and some will be magnetic after cold working. 

However, the high manganese steel with high manganese content is non-magnetic, and the magnetic situation of chromium-nickel-nitrogen stainless steel is more complex: some are non-magnetic, some are non-magnetic in the longitudinal plane and magnetic in the transverse plane. 

Therefore, the magnet method can basically distinguish between chromium stainless steel and chromium-nickel stainless steel, but cannot correctly distinguish some special properties of steel. 


3.Identification by copper sulfate. 

First, remove the oxide layer from the steel, and then put on a drop of water, wipe it with copper sulfate, if it does not change color, it is generally stainless steel; if it becomes purplish red, the non-magnetic one is high manganese steel, and the magnetic one is carbon steel or low alloy steel.