Stainless steel is resistant to air, steam, water and other weak corrosive media or stainless steel grades, such as 201 (1Cr17Mn6Ni5N), 202 and other 2 series steel grades, and the chemical corrosion resistant medium (acid, alkali, salt, etc.) corrosion of steel grades become acid-resistant steel, such as 304 (06Cr19Ni10), 316 (0Cr17Ni12Mo2) and other 3 series steel grades. Due to the difference in chemical composition of the two, their corrosion resistance is different, like the 2 series stainless steel is generally not resistant to chemical corrosion, while the 3 series stainless steel has the ability to resist chemical corrosion.
Common labeling methods on the market include chemical formula (06Cr19Ni10), SUS (SUS304), of which 06Cr19Ni10 generally indicates national standard production, 304 generally indicates American ASTM standard production, SUS 304 indicates Japanese standard production.
Of course, stainless steel is not completely rust-free, but compared with ordinary steel has better corrosion resistance, even if the same stainless steel corrosion resistance is also very different, like 2 series and 3 series is obvious. Sometimes we get a material without a long time of environmental testing before it is difficult to distinguish the material obtained is 2 series or 3 series, there are currently many detection methods on the market, briefly introduce two relatively simple methods, one is to look at the appearance, 201 for the representative of the 2 series contains higher carbon and manganese, the surface will be darker even if polished will be black and bright, the second is to see the cutting spark, 201 material is harder cutting when the spark will be more than large.
On the other hand, the 3 series represented by 304 will be brighter, the texture is relatively soft, and the cutting spark will be much smaller.
The largest amount of stainless steel is 201 and 304, 316 quality is higher, 304 and 316 are stainless acid-resistant steel, both are sanitary stainless steel, suitable for coastal use, but when the use of the environment chlorine content is relatively high, it is recommended to use 316, because 304 anti-corrosion is mainly the surface form of chromium oxide layer that is the bell layer, when the chlorine content in the environment is relatively high is to corrode the chromium oxide layer, so as to achieve the purpose of corroding the matrix, but 316 stainless steel contains platinum, The addition of platinum gives it a special corrosion-resistant structure. In some special occasions, such as strict requirements for thermal expansion, high-temperature precision parts should still choose 316 material, 316 basically does not have thermal expansion and contraction