stainless steels replacement

[fazel1]

- what is the difference between 304H stainless steel and 304 stainless steel ?as I know the grain size of 304H shall be coarser than ASTM No.7. but all of the mechanical properties of these two kind of steels are the same.

- can we use 304ss instead of 316ss at 550 centigrade degree?
316ss has additional element such as Mo which is effective for creep resistance,but base on ASME SecII partD the maximum temperature for 304ss is 1500F and for 316ss is 800F.

 

[EdStainless]

You asked about 6 questions there.
The role of 'H' grade (controlled higher carbon levels) is to provide higher creep and stress rupture strengths. There will not be any real difference in strength at lower temperatures. There is also no real difference in corrosion resistance (such as oxidation), except that the H grades are more susceptible to sensitization. The coarse grain size is because it is expected that everyone using "H" will be working at creep limited temperatures (otherwise you would use a regular grade) and the larger grains help improve creep strength.

What is the environment that you are looking at switching from 316 to 304? Plain air?? 550C shouldn't a problem for either alloy. Give us more detail.


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