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gpape (Mechanical) (OP)
1 Jun 05 15:10
Does anyone have any comments or history with these materials used for large, thick (14") ASME tube sheets?  Design 350 PSI @ 500°F - MDMT (-)20°F? I am interested in the toughness and the best material I can get.
Helpful Member!  metengr (Materials)
1 Jun 05 15:26
We have SA 350 LF2 forgings for our older high pressure and low pressure feedwater heater tubesheets. No problems to speak of - it is a very common forging material.

Today, I would probably recommend going with SA-765 Grade II only because it applies directly to carbon and low alloy steel forgings for use in heat exchanger and feedwater heater components, like tubesheets.
stanweld (Materials)
1 Jun 05 15:57
SA-350 LF1 and LF2 has a long history in both the petrochemical and power industries in similar thickness and thicker tubesheet applications. The primary differences between the two specs are SA-350 LF2 is made to fine grain melting practice and impact testing is required while fine grain melting and impact testing is optional for SA-765. There is also a subtle difference in impact test location for your thickness.
metengr (Materials)
1 Jun 05 16:11
Impact tests are required in ASME SA 765 - Table 3. The purchaser can recommend other test temperatures as optional but you need to conduct impact tests. For Grade II the impact test requirement is 12 ft-lbs at -50 deg F.

gpape (Mechanical) (OP)
1 Jun 05 16:28
Thanks metengr!  You have stated the same evidence that I had originally come up with. The only draw back that I can see, is the addition of Ni, Cr, Mo, V, Al & Cu to the chemical analysis. I do understand that this makes it tougher and more weldable that LF2. I also am happy with the required testing, since I have required even more tests than SA 765 requires when I bought SA 350 LF2.
stanweld (Materials)
1 Jun 05 16:48
Oops, misread 6.1. Going senile.
metengr (Materials)
1 Jun 05 16:54
Been there and have done that many times. Time for a beer!
unclesyd (Materials)
1 Jun 05 17:52

I call that a "senior moment" and it seems to happening more frequently.

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