In various procurement scenarios, we often need to determine the authenticity of stainless steel, which may use chemical identification, grinding identification, visual identification, magnet identification, etc.
The variety of chemical identification is the easiest way. A stainless steel identification agent is available on the market and will display different colors under different steels. The discriminators can quickly distinguish the stainless steel grades by comparing their display colors to the corresponding color cards. Another mainstream method is the use of CuSO4. The discriminator needs to remove the oxide layer on the steel, put a drop of water, and rub it with CuSO4. If it does not change color after rubbing, it is generally stainless steel; if it turns purple red: non-magnetic is high manganese steel, and magnetic is generally ordinary steel or low alloy steel.
The identification of the grinding is to put the stainless steel on the machine to grind it, usually on the grinder and watch the shape and color of spark. If the spark is streamlined and has more dense forks, it is high manganese or manganese nitrogen steel with higher manganese content; if there is no fork, it is chrome steel or chrome nickel stainless steel.
Direct visual identification is less reliable, because the difference in appearance of various types of stainless steel is difficult to observe. Therefore, this method needs to be combined with other methods.
Since the austenite type is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic, you can use this method easily distinguish between the two. Other methods can be combined to further distinguish some stainless steels, such as the above chemical identification, or to identify chromium-nickel stainless steel by annealing test.
In general, using a variety of methods can only identify certain stainless steels, but it is not yet possible to determine the elemental content of the steel. Therefore, the best method is to go to the production site, inspect and ask the manufacturer to show the relevant materials to determine the specific element content.