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How To Identify Stainless Steel
Apr 23, 2018

A method for identifying high quality stainless steel

To distinguish stainless steel from imported or steel mills, it is generally necessary to check the signs on the steel or packaging according to the quality certificate of the import or steel works.

In the case of unknown steel grades (No.) of no quality certificate for bulk cargo, in-depth investigation should be carried out, or physical identification of stainless steel should be carried out.

1). The difference of color and lustre:

After the pickling of stainless steel, the color of the surface is silver and white. The chrome nickel stainless steel is white and white, and the chrome stainless steel is slightly gray and weak; the color of chromium manganese nitrogen stainless steel is slightly lighter than that of chrome nickel stainless steel. The surface color of stainless steel without pickling: chromni steel is white; chrome steel is brown black; chromium manganese nitrogen is black. (these three colors are the heavier color of oxidation). Cold rolled unannealed Cr Ni stainless steel has silver white reflection on the surface. Stainless steel is generally white after pickling.

2). Identify with copper sulphate:

The method is to remove the oxide layer on the steel, put up a drop of water, wipe with copper sulphate, and wipe it out, such as stainless steel, such as purple red: non magnetic for high manganese steel, and magnetic generally ordinary steel or low alloy steel.

3). Discriminate with the use of the magnet:

Magnets can basically distinguish two kinds of stainless steel. The chromium stainless steel can be attracted by magnets in any state, and the chromium nickel stainless steel is generally non magnetic in the annealed state, and some will be magnetic after cold processing. But the high manganese steel with high manganese is non magnetic; the magnetic condition of chromium nickel nitrogen stainless steel is more complex: some are non magnetic, some have magnetic, some longitudinal surface is non magnetic and the transverse surface is magnetic. Therefore, although the magnetic stone can basically distinguish between chromium and chromium nickel stainless steel, it can not correctly distinguish some special properties of steel, but can not distinguish the specific steel number.

For special properties of steel, we need to identify the following three ways:

1) grinding flower identification:

Mill identification is to wear stainless steel on the grinder and observe its sparks. If the spark is streamlined and has more dense flower joints, it is a high manganese steel or manganese nitrogen steel with high manganese content, such as chrome free steel or chrome nickel stainless steel.

2) the annealing method is identified:

The chromium nickel stainless steel of the cold working hand, if magnetic, can be cooled or placed in water (annealed) in a small piece of red in a fire. Generally, the magnetic properties will be significantly weakened or completely disappeared after annealing. However, some of the chromium nickel stainless steel, such as Cr18Ni11Si4AlTi steel and Cr21Ni5Ti steel, have many ferrite elements in the steel, and the internal structure of the steel is quite part of the ferrite. Therefore, even in the state of hot working, there is magnetism.

3) chemical qualitative identification:

Chemical qualitative method is a kind of identification method for identifying the nickel in the magnetic stainless steel. The method is that the small stainless steel is deeply dissolved in Wang Shuizhong, the acid is diluted with water purification, and then the ammonia is added to the neutralization of the ammonia water, then the nickel reagent is gently injected. If there is red velvet substance on the liquid surface, it means that nickel is found in stainless steel. If there is no red velvet substance, it is proved that nickel is not found in stainless steel.