Stainless steel is a kind of high-grade alloy steel, such as stainless steel tools, stainless steel kitchen utensils, stainless steel building materials, etc. in our daily life. It has the characteristics of rust free, acid resistance, high temperature resistance, wear resistance and general non magnetism of austenite. Let's all join us to see several simple identification methods of stainless steel, hope to help you!
Do you know the simple identification method of stainless steel?
In the case of unknown steel (No.), we can determine whether it is stainless steel or which kind of stainless steel is or not according to the inherent physical and chemical properties of commodities (including whole material, surplus material, waste material, etc.), and by means of simple instruments, we can determine whether it is stainless steel or which kind of stainless steel.
It should be pointed out that: sensory identification can not distinguish the specific steel (type) number, but can only basically distinguish three major categories: chromium stainless steel, chromium nickel stainless steel (sus303, 304) and chromium manganese nitrogen stainless steel (200 Series), and the identification methods are as follows:
1. Identification of color
The color changes before and after pickling of stainless steel were identified
After pickling, the surface color of stainless steel is silver white and bright: chrome nickel stainless steel color silver white is jade color; The color of chromium stainless steel is white and slightly gray, and the luster is weak; The color of Cr Mn n stainless steel is slightly lighter than that of Cr Ni stainless steel. The surface color of stainless steel without pickling: Inconel steel is brown white, chrome steel is brown black, chromium manganese nitrogen is black (these three colors refer to the color with heavy oxidation). Cold rolled annealed chromium nickel stainless steel, silver white surface reflective.
2. Identification by copper sulfate
The method is to remove the oxide layer on the steel, put a drop of water, and wipe with copper sulfate. If it does not change color after being wiped, it is generally stainless steel; If purple red: non magnetic for high manganese steel, magnetic generally for ordinary steel or low alloy steel.
3. Identification by using the iron absorption
The magnetic energy is basically different from two kinds of stainless steel. Because chromium stainless steel can be attracted by magnet in any state; Chromium nickel stainless steel is generally non magnetic in annealed state, some of which will have magnetism after cold processing. But the high manganese steel with high manganese content is non magnetic; The magnetic situation of Cr Ni n stainless steel is more complex: some are non magnetic, some are magnetic, some longitudinal surface is magnetic and the transverse surface is magnetic.
Therefore, although the magnet can basically distinguish chromium stainless steel from chromium nickel stainless steel, it can not distinguish some special steel types correctly, and can not distinguish specific steel grades.
For the special steel, we need to take the following three methods to identify.
1) Identification of grinding flowers
The identification of grinding flowers is to wear stainless steel on the grinder and observe its sparks. If the spark is in flow line and there are more dense flower saving, that is, the high manganese steel or Mn nitrogen steel with higher manganese content; If there is no flower, it is chromium steel or chromium nickel stainless steel.
2) Annealing identification
If the cold-processed chromium nickel stainless steel has magnetism, it is advisable to burn small pieces in the fire to cool or put it into water (annealed). Generally speaking, the magnetic properties will be significantly weakened or completely disappeared after annealing. But some chromium nickel stainless steel, such as cr18ni11si4alti steel and cr21ni5ti steel, have a lot of ferrite elements in the steel, and the internal structure of them is ferrite. Therefore, even in the state of hot working, there is magnetism.
3) Identification by chemical qualitative method
Chemical qualitative method is a method to identify whether there is nickel in magnetic stainless steel. The method is to dissolve small stainless steel in the water of Wang, dilute the acid solution with clean water, neutralize with ammonia water, and then inject nickel reagent gently. If red plush material is floating on the liquid surface, it indicates that the stainless steel contains nickel; If there is no Red Velour material, it is proved that there is no nickel in stainless steel（ However, because of the low nickel content in stainless steel, only a few percent of the total nickel content is not easy to be exposed or determined. Generally, it can be mastered after several times of standard sample experiments.
The above identification methods indicate that: sensory identification of stainless steel requires not only several methods of comprehensive test, but also the test results can only determine a certain type of stainless steel, which alloy elements and specific content in the steel can not be determined. Therefore, the sensory identification method is very imperfect, some may be wrong, there are many physical phenomena, but we only know it but do not know it, so it needs further discussion.
The best way to distinguish stainless steel grades correctly is to go deep into the investigation and research of relevant processing units, ask their material managers and workers' masters for advice, understand the steel conditions of materials, carefully check the steel mark on the steel, and consult the original data, etc., which is the basic method to distinguish the stainless steel grades and quality correctly.