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Sheet metal processing materials judgment

Angelina Dong original 2015-10-14 10:29:31
Commonly used stainless steel materials, 201, 304, 316 l, between the price difference is bigger, mainly containing nickel content is different, the price of 201 and 304 by about 500 yuan/ton, 316 l price is expensive about 1000 304 yuan/ton.
201 is China's 1 cr17mn6ni5n 304 Chinese equivalent of the 0 cr18ni9 316 l 00 cr17ni14mo2 equivalent to China
201, 304, 316 l is American standard, the relative China: stainless steel GB1220-2007 standardStainless steel has the ability of resistance to atmospheric oxidation - namely, stainless, also has in the medium containing acid, alkali, salt is the ability of corrosion - namely, the corrosion resistance.
But the size of its ability to resist corrosion was with the chemical composition of steel itself, and each state, using conditions and environmental medium type and change. 
201 dry clean the atmosphere is not easy to rust, but in the wet or acid, alkali, salt material environment is easy to rust;
304 in a dry cleaner in the atmosphere, there is absolutely excellent corrosion resistance, but it will be moved to the coastal areas, in contains a great deal of sea salt fog, will soon be rusty;316 steel pipe is good;
So, not any kind of stainless steel, in any environment corrosion, no rust.Stainless steel is formed on the surface of a layer of a very thin and fine and stable solid rich chromium oxide film (protective film),
Prevent oxygen to seep into the, continue to oxidation, and ability to resist corrosion.Once you have some reason, this film has been continuously destroyed, air or liquid oxygen in the original child will constantly infiltration or metallic iron atom separation out unceasingly,
Forming loose iron oxide, gold Surface are also constantly rust.Many in the form of the surface film is damaged
See more in daily living has the following kinds:
1. The deposited on the surface of the stainless steel contain other metal elements of dust or heterogeneous metal particles with the content, in the humid air, attachments and condensed water between the stainless steel,Will both together as a micro battery, triggers the electrochemical reaction, protective film is damaged, to call the electrochemical corrosion. 
2. The stainless steel surface adhesion organic fluids (such as melon seeds, noodle soup, sputum, etc.), under the condition of water is oxygen, organic acids,For a long time, organic acid corrosion of the metal surface.
3. The stainless steel surface adhesion containing acid, alkali, salt substances (e.g., decorate the walls of caustic soda, stone splash water), cause local corrosion. 
4. Where there is pollution in the air (e.g., contains a lot of sulfur, carbon oxide, atmospheric nitrous oxide), encounter condensation water, formation of sulfuric acid, nitric acid, acetic acid, liquid, chemical corrosion.
inSheet metal processingHow to determine is that kind of stainless steel, 304, 201, 316 l stainless steel with your eyes is difficult to determine is the kind of stainless steel material, stainless steel stainless steel chemical composition detector test are available, andThis method accuracy is high, but more troublesome, general company has no such equipment, the market has a stainless steel testing medicine water droplets in the stainless steel surface will show color, contrast color to determine the relative material, convenient and practical, but the accuracy is not high.  

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