Stainless steel: 304 and 321

For the stainless steel 304 and 321, the main difference is that 304 does not contain Ti, and 321 contains Ti. Ti can prevent stainless steel from sensitizing. Generally speaking, Ti can improve the high temperature service life of stainless steel. That is to say, 321 stainless steel plate is better than 304 stainless steel plate under high temperature. Both 304 and 321 are austenitic stainless steels, and their appearance and physical properties are very similar, just very small difference in chemical composition.

First of all, 321 stainless steel is required to contain trace amounts of titanium (Ti) (according to the ASTM A182-2008 standard, the Ti content should not be less than 5 times the carbon (C) content, but not more than 0.7%, and 304 and 321 The carbon (C) content is 0.08%), and 304 does not contain titanium (Ti).

Secondly, the requirements for nickel (Ni) content are different. 304 is between 8% and 11%, while 321 is between 9% and 12%.

Third, the requirements for chromium (Cr) content are different. 304 is between 18% and 20%, while 321 is between 17% and 19%.

So that you can use metal material analyzer or chemical analysis method to verify the composition of these two materials and make judgments.