The latest stainless steel method to identify the advantages and disadvantages = Xin Cheng stainless steel color to provide identification of the pickled stainless steel, the surface color silver white smooth: chromium nickel stainless steel color silver white jade; chromium stainless steel color white slightly gray glossy weak; chromium manganese nitrogen stainless steel color and Chrome-nickel stainless steel is slightly lighter. The surface color of stainless steel that has not been pickled: Chrome-nickel steel is brownish white, chrome steel is brownish black, and chromium-manganese nitrogen is black (these three shades are heavily oxidized). Cold-rolled unannealed chromium-nickel stainless steel with silver-white surface.
Discriminating magnets with magnets can basically distinguish two types of stainless steels. Because the chromium stainless steel can be attracted by the magnet in any state; the chromium nickel stainless steel is generally non-magnetic in the annealed state, and after the cold working, some are magnetic. However, manganese-rich steels with higher manganese content are non-magnetic; chromium-nickel-nitrogen-based stainless steels have more complex magnetic properties: some are non-magnetic, some are magnetic, and some have a non-magnetic vertical surface and a magnetic surface. Therefore, although magnets can basically distinguish between chromium stainless steel and chromium-nickel stainless steel, they cannot correctly differentiate some special-purpose steel grades, let alone distinguish specific steel grades.
Identification with copper sulfate will remove the oxide layer on the steel, put a drop of water, rubbing with copper sulfate, if not changed after rubbing, usually stainless steel; such as changing purple, non-magnetic high manganese steel, magnetic generally Ordinary steel or low alloy steel.
For steels with special properties, we need to adopt the following three methods for identification.
Grinding the flower to identify the grinding flower is to distinguish the stainless steel from the grinding wheel and observe the spark. Such as sparks are streamlined, and there are more dense section of the flower, that is, higher manganese containing high manganese steel or manganese nitrogen steel; if no flowers are chromium steel or chromium nickel stainless steel.
Annealing is used to identify cold-worked chromium-nickel stainless steels. If they are magnetic, they may be red-hot in the fire to allow them to cool naturally or be added to water (annealing). In general, after annealing, the magnetic properties are significantly reduced or completely disappeared. However, some chromium-nickel stainless steels, such as Cr18Ni11Si4AlTi steel and Cr21Ni5Ti steel, because the steel contains more ferrite elements, a considerable part of its internal structure is ferrite. Therefore, it is magnetic even in the hot working state.
Chemical Qualitative Method The Differential Chemical Qualitative Method is a method for identifying whether or not nickel in a magnetic stainless steel is contained. The method is to dissolve small pieces of stainless steel in aqua regia, dilute the acid solution with clean water, add ammonia water, and then gently inject the nickel reagent. If there is a red fluffy substance floating on the liquid surface, it means that stainless steel contains nickel; if there is no red fluffy material, it proves that there is no nickel in stainless steel (but because of the low nickel content in stainless steel, it is generally only a few percent, nickel The content is not easy to reveal or determine how much, in general, the standard sample must be used after many experiments.)
The above several authentication methods show that in order to identify stainless steel with a sense tube, it is necessary not only to use several methods for comprehensive tests, but also that the test results can only determine certain types of stainless steel, and it cannot be determined which kinds of alloy elements and specific contents the steel contains. Therefore, the method of sensory identification is currently extremely imperfect, and some may be erroneous. There are many physical phenomena. They only know it, but they do not know why it needs to be discussed further.
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