SA-350 LF2 vs SA-765 GR 2 1

[gpape]

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.

 

[metengr]

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]

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]

Stanweld;
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]

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]

metengr,
Oops, misread 6.1. Going senile.

 

[metengr]

Stan;
Been there and have done that many times. Time for a beer!

 

[unclesyd]

stanweld

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