hello,
I have different reason for selection of the material however the recommendation is the same as suggested by Mr. Girish. if we see the ASTM composition of SS304 and SS302 then the difference is not in allowed max limits of Sulphur or Phosphorous. The code has given same limits for these two alloys. The basic difference is in % of C, Cr and Ni
1. %C: 302...0.15%
304...0.08%
2. %Cr: 302...17-19%
304...18-20%
3. % Ni: 302...8-10%
304...8-10.5%
4. %P & S same in both case.
So if we see the difference, it is basically in % of C with slight variation in % Ni & Cr (i.e. on lower side). If you are going to weld the material, there will be more chances of sensitization in case of 302 where as in case of 304 it will definitely be on lower side. As such, as far as sensitization is concerned, you should go for 304. However, the cost of 302 is low because of higher % of C (because of less processing of molten material during its melting) and of course because of slightly lower amount of alloying elements.
On the other hand, the mechanical strength of SS302 is on higher side because of higher C%. But, why don't you try for SS304L material which has max. C 0.03%. this is most suitable for the jobs where corrosive fluids are to be handled, and welding is involved. As it seems that you are going to give fillet welds, i would strongly suggest you to use 304L. if you go for 304, there will be 100% chance that the material will still be sensitized during the welding process and when you apply pickling solutions to clean it after welding or it is subjected to corrosive medium in its service, it will fail because of IGC. Hence, to achieve better equipment life go for SS304L in stead of 304
RK