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Hamid,
even though speaking against your signature to not 'regret' in our short lifes, with this topic I must regret.
I am certainly far of being just the shadow of an expert with SAW, but being rather a true layman! You know, I would describe myself as an 'Open Arc Fanatic'.
Thus, I am sure that others who are using this interesting process daily and hereby knowing it inside out may share their experience with us.
However, I must confess that I was a bit uncertain when I read the options 'b' and 'd'.
As I know that a low hydrogen basic coated electrode type - all precaustions provided - leads to most outstanding impact strengths I was truly tempted on a first view, to tick answer 'd'.
But, by knowing the the very basics of SAW, I considered on a second view and would understand if it's really option 'b'.
This due to SAW under basic fluxes does not have the absolutely same effects as compared with basic stick electrodes - at least to the best of my knowledge. Therefore, it is - under the consideration that it is the electrode/flux combination but not the flux alone, which 'makes the result - it might truly be the case that SAW under acid flux gives you the
"...Highest impact strength in ferritic weld metal..." .
What I mean to know as well is, that the index of basicity - which is < 1 when speaking of an 'acid' flux - and what normally deteriorate the mechanical properties of the weld metal as it allows an oxygen addition to the liquid weld pool, is compensated by an appropriate filler metal. That is, the wire is making sure that the 'negative' influence of the flux does not determine the final material properties.
And finally, as we are speaking of 'ferritic' weld metal - whatever this means(!) - I assume that we are speaking of plain carbon steel base material. And by considering that an SAW weld seam consits by 60... 70% of the base material itself and is balanced by the filler metal, i.e. 30... 40%, I may assume that the very positive metallurgical reactions in SAW (protecting the metal-slag-gas reactions in the liquid weld pool against the direct influence of the sourrounding atmosphere) may lead finally to higher impact strengths even compared with basic coated SMAW electrodes.
Eventually this might be discussible, but by generalising the question by using a minimum of a minimum of a minimum of specific information it is really hard to decide whether a weld metal deposited from a bakened basic coated low-hydrogen SMAW electrode wouldn't eventually have yet a higher impact strength.
Like I say. I am very sorry to be unable to explain this in the certainly necessary depth, and look forward instead to what will come from the SAW experts in the forum!
Thanks for your understanding!
Stephan