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Stainless steel is an alloy whose main component is iron. In addition to iron, stainless steel also contains chromium, nickel, manganese, carbon, silicon, molybdenum and other elements. According to the types and contents of different elements, stainless steel can be divided into various types. Interested students can check the contents of GB / T 13304 "classification of steel". 

As long as the stainless steel pot used in the title is produced by a regular manufacturer and passed the inspection, then the normal use of cooking and cooking will not lead to excessive release of heavy metals. But if you want to buy a pot from an unknown source, it's hard to say. For example, in the following figure:

 a workshop uses iron barrels filled with chemical raw materials to make a steel frying pan. The picture is from Netease News http://news.163.com/photoview/00AP0001/21147.html#p =7R3P6PMR00AP0001。 
 this kind of waste iron bucket used to hold chemical raw materials, if used in the production of kitchen utensils, I am afraid that it is not only the problem of excessive heavy metals. 

 also, if you buy a regular and qualified product, don't feel "at ease" 
, because if the stainless steel pot is dry burned due to improper operation or carelessness, it may lead to the precipitation of heavy metals. 
 this phenomenon is especially obvious in chromium rich stainless steel pots. 

This is because when the stainless steel pot is dry fired at high temperature, it will lead to the appearance of chromium rich σ phase and chromium poor area. In the process of cooking food, if the food medium is acidic, the chromium rich σ phase and chromium poor area will react with each other, and the chromium in the poor chromium area will form ions and precipitate into the food However, the metal chromium may fall off and transfer to food, which may lead to excessive chromium. 

 the SEM results showed that white massive particles (chromium rich compounds) appeared on the surface of the dry roaster. The picture is from Huang Zidong et al. The reason why the chromium ion precipitation exceeds the standard after dry firing of 430 stainless steel pot [J]. Mechanical engineering materials, 2019, 43 (4): 79-82 
 it doesn't matter if you don't understand the above principle, as long as you know that the stainless steel boiler may cause heavy metal precipitation when it is dry fired at high temperature. 

In addition, we also need to note that stainless steel products are corrosion-resistant, which does not mean that they will not corrode. Therefore, we should pay attention not to use them to hold acid, alkali, salt solution and other media for a long time. 

In short, in order to avoid the possible safety problems caused by the use of stainless steel pots, at least two points should be done: 
 one is to purchase qualified products; the other is to use them correctly and standardize, and try to avoid dry burning. 

 the comments section mentioned what to do if there is dry burning and whether to throw it away. I will update the answer here. If the stainless steel pot appears dry burning situation, do not easily go to extremes to make "throw the pot away". The results show that whether dry burning can lead to excessive heavy metals mainly depends on the fuel type and food medium. For example, the possibility of heavy metals exceeding the standard due to dry burning with natural gas is higher than that with gas, and the possibility of excessive heavy metals caused by cooking vegetable soup is higher than that of boiling water and porridge. 

 dry burning of natural gas is more likely to lead to excessive heavy metals than gas dry burning, and the possibility of heavy metals exceeding the standard caused by cooking vegetable soup is higher than that caused by cooking porridge and water. The picture is from Lin Junming et al. Study on the influence of dry firing on heavy metal migration in 304 stainless steel pot [J]. China standardization, 2019, 2019 (1): 167-170. 
 other factors such as dry firing time, times and fire power also affect the amount of heavy metals released, but they are not as big as the above two. 

Therefore, if the stainless steel pot at home has experienced dry burning phenomenon, it can be properly analyzed under what conditions the dry burning is not serious. If the dry burning has led to uneven bottom, deformation and serious color change, it is recommended to change the pot. Of course, if you don't want to be bothered by this kind of problem and have plenty of money, go straight to it. 

 the following two students 

 @ want to know 
 is more rational and professional. This is knowledge. The more the argument is, the clearer the truth is.


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