The difference between 201 stainless steel and 304 stainless steel

A university chemistry teacher once told us that you must be careful when buying stainless steel thermos cups or other kitchen utensils. If you can't distinguish whether its material is 201 or 304, you'd better buy a brand name product. Because some on the market use non-food grade 201 as food grade 304 stainless steel. If it is a 201 stainless steel thermos cup, if it is used for a long time, the heavy metal elements in 201 will cause great harm to us. If you don't know the difference between 201 and 304, you may buy 201 stainless steel at the price of 304, which will not only cause economic losses, but more importantly, product quality will eventually go wrong, leading to more serious problems in the future. Therefore, it is extremely important to understand the characteristics of 201 and 304 and know how to distinguish them. The following will briefly introduce the characteristics of 201 and 304, and then introduce some methods to distinguish them. Which elements in stainless steel determine the corrosion resistance of stainless steel?

The first is the element chromium. The second is nickel element. Chromium alone is high enough to provide corrosion resistance, but nickel must be combined with chromium to provide corrosion resistance. The industry standard stipulates that in order to maintain the inherent corrosion resistance of 304 stainless steel, it must contain more than 18% chromium and more than 8% nickel. 201 stainless steel has weak corrosion resistance, and SUS201 stainless steel strip for non-food grade stainless steel contains (Cr) chromium: 16.0~18.0%, (Ni) nickel content 3.50-5.50% (JIS G 4304-). Most of the 200 series stainless steel sold in the Chinese market has little control of sulfur and carbon content in accordance with national standards, replacing part or all of nickel with manganese (and nitrogen) to produce lower nickel content austenitic stainless steel. The disadvantage of this series of materials is: the chromium content below 18% and the low nickel content cannot reach a balance and form ferrite. For this reason, the chromium content in the 200 series stainless steel is reduced to 13.5%~15%, some The situation has dropped to 13%~14%, and its corrosion resistance cannot be compared with 304 and other similar steels. In addition, manganese and in some cases copper reduce the effect of repassivation under acidic conditions common to corrosion sites in deposition zones and crevices.

200 series steel will fail at these conditions approximately 10-100 times faster than 304 stainless steel. 201 stainless steel is non-food grade and cannot be used to make thermos cups, kitchen utensils, etc. If 201 is used as a food-grade material, the human body will use such inferior products for a long time, which will be extremely harmful to the body. 304 stainless steel has better corrosion resistance, food grade stainless steel SUS304 stainless steel strip contains (Cr) chromium: 18~20%, (Ni) nickel content 8-10.5%. How to distinguish 201 and 304 stainless steel smart eye beads 1) 201 is harder and brittle than 304, and 304 has better toughness. 2) Moisture resistance: while 304 will not rust; but many people say that stainless steel 304 is rusted, it may not be stainless steel at all 304.3) Spectrometer detection method, this method is the fastest and most accurate, but the price of the spectrometer is expensive. Generally, individuals will not buy a spectrometer for testing to buy some materials; if the material is very important and the element content is very high, then the You can find a special testing company, they usually have a spectrometer