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  • Tel: +86-29-89636557

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  • How Do You Identify Which Grades Stainless Steel You Have?
    Jun 20, 2018

    stainless steel pipe/sheet/bar

    Stainless steel is a steel alloy that contains Chromium,Nickel and other elements, such as Ni, which can be alloyed with stainless steel, adding to the complexity of identifying stainless steel from other types of metal. Do you find that stainless steels is hard to identify?


    Sensory detecting methods can basically identify those three grades: Cr stainless steel (series 400), Cr-Ni stainless steel (series 300) and Cr-Mn-N stainless steel (series 200) , but it can't distinguish the specific steel grades. In the case of unknown steel grade, we can based on the physical and chemical properties of the steel, with the help of simple tools to determine if it is stainless steel and what kind of stainless steel it is. Here we will tell some simple identification methods for you:

     

    1. Observing the color of the item after picking process

    Generally speaking, the color of stainless steel after pickling will change on the surface:

    Grade of steel

    Color after pickling

    Color before pickling

    Cr-Ni stainless steel

    Silver-white

    Brown-white

    Cr stainless steel

    Gray-white,shiny

    Dark brown

    Cr-Mn-N stainless steel

    Silver-white

    Black


    2 Testing with copper sulfate

    copper sulfate test often come with good results. Dissolve about 8 grams of copper sulfate in about 500 ml of water. Swab that on to the item you tests. Carbon steel surfaces will immediately show a copper color as the iron dissolves and the copper replaces it. 300 series stainless shows no reaction, and 400 series usually won't show a reaction, or it'll be very limited.


    3 Testing with Magnet

    The alloy make-up of the stainless steel will determine if it is magnetic or non-magnetic. Although the magnet can basically distinguish the Cr stainless steel and the Cr-N stainless steel, it cannot distinguish the specific steel grades and concrete steel number accurately. 400 series are magnetic, 304,316, 201,202 is the the only stainless steel that is not attracted by magnet, However, 304 could become magnetic when cold worked. Because Cr stainless steel can be magnetized in any condition; Cr-Ni stainless steel is generally nonmagnetic in annealing, and some will be magnetic after cold processing; The magnetic condition of Cr-Ni-N stainless steel is more complicated: some are non-magnetic, some are magnetic, some are non-magnetic and the horizontal surface is magnetic. High manganese steel is completely nonmagnetic.  

     

    For special types of steel, more sophisticated methods are needed to identify them:

    1 Spark testing

    If you grind a bit of the item on a grinding wheel and it gives off sparks, the item is most likely made of a 300-series grade of Cr stainless steel. If it throws a “glow” of intensive sparks, then it is high manganese steel or Mn-N steel.

    2 Acid testing 

    Place a drop of strong Nitric acid/ Sulfuric acid on the steel surface, or the steel in acid solution at room temperature. Observing the changes of the surface color of the item: Strong attack , green crystals and dark surface:302,304; Slow attack, tan surface turns brown:316.


    Please Email to:sxthsteel@sxth-group.com to learn more .