Stainless steel surface color without pickling: chrome-nickel steel is brownish white, chrome steel is brownish black, and chrome-manganese nitrogen is black (three colors are heavier oxidized colors). Cold rolled, unannealed chrome-nickel stainless steel with a reflective white surface. After pickling stainless steel, the surface is silvery white: chrome-nickel stainless steel is silver-white; chrome-stainless steel is slightly gray; chrome-manganese-nitrogen stainless steel is similar in color to chrome-nickel stainless steel.
The magnet basically distinguishes between two types of stainless steel wire mesh. Because chrome stainless steel can be attracted to the magnet under any circumstance; chrome-nickel stainless steel is generally non-magnetic in the annealed state, and some may be magnetic after cold working. The high-manganese steel with high manganese content is non-magnetic; the magnetic condition of chromium-nickel-nitrogen stainless steel is complex, magnetic, longitudinally non-magnetic, and laterally non-magnetic. Therefore, although the magnet can basically distinguish between chrome stainless steel and chrome-nickel stainless steel, it is impossible to distinguish the steel grades of some special purposes correctly, and it is impossible to distinguish the specific steel grades.
Remove the oxide layer on the material, put a drop of water, rub it with copper sulfate, if it does not change after rubbing, it is generally stainless steel; if it turns purple, non-magnetic is high manganese steel, magnetic is ordinary steel or low alloy steel .
These are just basic identification methods. If you want to conduct an in-depth appraisal, please go to a special testing agency for testing.
For the difference between 304 and 316: First, the material is different, 316 contains more than 304 nickel, and nickel is an important component affecting the anti-rust properties of stainless steel. On the surface, there is no difference between stainless steel meshes of different materials, but the service life will be different during use. Nickel-free stainless steel rusts after wet or wet, and nickel-containing screens have a relatively long service life.
Compared with 304, the main chemical composition of 316 and 304 differs in that 316 contains Mo, so 316 is highly corrosive and rust-resistant. Therefore, when selecting a stainless steel wire mesh, it is more appropriate to select 316 if it is to filter corrosive materials.
Different performance: 304 steel can resist corrosion of sulfuric acid, phosphoric acid, formic acid, urea and the like. Applicable to general water, used to control gas, alcohol, milk, CIP cleaning fluid and other occasions with little or no contact with materials.
316 added molybdenum on the basis of 304, which significantly improved its resistance to intergranular corrosion, oxidative stress corrosion, reduced thermal cracking tendency during welding, and good chloride ion corrosion resistance. It is commonly used in high purity and medium corrosive environments such as pure water, distilled water, medicines, sauces and vinegar.
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