FCAW and SAW

[kissjxp]

I have a couple of questions about FCAW and SAW Welding process.

(1) The vessel (SA516-70N) MDMT is -50F.
Can I use F7XT-9 as the filler metal and do impact test for the weld at -50F on the PQR? I am worried about it because it is recommended to do impact test at -40F (ASME II PARTC SFA5.20). Does it means that this filler metal can not be used at a temperature lower than -40F?

(2)The vessel (SA516-70, No PWHT) MDMT is -20F.
Can I use Flux F7A4 and do impact test for the weld at -20F on PQR?

(3)The vessel (SA516-70N, No PWHT) MDMT is -50F.
Can I use Flux F7A4 and do impact test for the weld at -50F on PQR?

Thanks.

 

[weldtek]

kissjxp,
Consumables may be used for applications with a design temperature lower than that they're certifed for, but, there are some things you need to consider before deciding to do so.
Most important, if the vessel requires impact testing, with few exceptions, you must perform production impacts. So, you have to decide how big of a risk this poses, and, whether, or not, it's an acceptable one. Some fabricators regularly use CS FCAW for applications at -50 F. I'd suggest you talk to your wire manufacturer for advice. Using the correct parameters is important.
When it comes to SAW, there are several CS wires that are certified for temps below -50 F, so, why not just use one of them. LA-71 with 880M flux is the wire / flux combination we use most often, and it's an A6/P6 class.

 

[kissjxp]

weldtek

thanks!

Acctually, I am reviewing the vessel manufacturer's welding procedures. I have to check the suitability of their selection.