Highest impact strength in ferritic weld metal

By Stephan (***)

Date 09-05-2009 13:47 Edited 09-05-2009 13:49

Hamid,

I did resist for a while but now I must yield the 'internal pressure'.

There was another topic - very interesting by the way - posted by you and dealing with 'heat input and distortion' and some of the best fellows have shared their expertise with you and us by explaining the reasons for the correct answer.

And then finally with this named thread you came with the following comment (quote):

"First of all I want to say that I read it in CSWIP 3.1 book. I explain this phenomenon as follow:" . (unquote)

You know, in my opinion, the issues in relation with heat input and distortion in welding are way to intricate to 'squeeze' them into one or two sentences. There is a universe of factors interacting for a particular material being welded and the leading elite of welding-scientists is researching by nowadays in order to find explanations - in particular - for the physics of 'heat input' and its interaction(s) with the solid/liquid matter.

Well, please don't get me wrong, since there is absolutely no offence intended, but please let me ask:

What does the CSWIP 3.1 book say about this phenomenon, i.e. answer "b", and how would you personally 'explain' this phenomenon?

You know, it's just to avoid investing time and willingness to explain it with our own words, just as been done with the 'heat input...' thread, and must reading afterwards what a particular 'CSWIP...' or 'TWI' handbook did mean on it.

Ahh, I almost forgot.

What do you mean..?

Are the SAW weld pool and droplet transfer directly affected by the surrounding atmosphere..?

And as soon as you've cosidered this and have come to a result, please let me quote what the 'AWS Welding Handbook, 2004, Ninth Edition, Volume 2, Welding Processes Part 1, Chapter 6, pp. 272' says on this.

Quote: "Fluxes are classified on the basis of the weld metal obtained when used with specific electrodes , the heat treatment conditions under which these weld metal properties are obtained and the chemical composition of the electrode."

By the way, the book mentioned above is - at least from my humble point of view - very recommendable.

Stephan

By hrezvany (*)

Date 09-06-2009 10:58

Don't be worry about my explanation about distortion.
I want to illustrate my main aim to discuss in this froum: I enroled in one CSWIP 3.1 coruse and with respect to my previous knowledge in the welding field, I am reading and surveying presented issues in the cswip book. I have to attend in a nearly difficult final exam and I have to be convinced regarding presented statements in this book. These statements are not true through and through and my main goal to present them is only for investigating elaborately.

You said that "Are the SAW weld pool and droplet transfer directly affected by the surrounding atmosphere..?"
As you are aware, the arc and weld pool are submerged in the flux and only after recycling the flux the weld pool is exposed to atmosphere.

I don't know why you ask this question because we want to survey impact strength of the weld metal. perhaps you want to mention to low cooling rate in this welding procedure due to existance of the flux which cover hot weld pool. But notice to this reality that SAW has the most heat input which can affect impact strength itself alone. Because impact strength is "The ability of a material to withstand shock loading" This caracteristic could be affected by heat input.
In my opinion, High heat input results in low impact strength not in high.
what's your opinion?

By Stephan (***)

Date 09-06-2009 17:05

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

By GRoberts (***)

Date 09-10-2009 00:12

Seems like a strange answer to me. I would have gone with d. Compare the ESAB literature on their run-of the mill Atom Arc 7018 (i.e. not 7018-1), and they say 168 ft-lb at -20F. Then take one of their active (acid) SAW fluxes. OK 350 claims 36 ft-lb at -20F with the best choice of the 3 wires listed. Other fluxes listed fair quite a bit worse. I'm sure you could find examples the other way if you look hard enough, but why such a subjective question on a test?

By Stephan (***)

Date 09-10-2009 09:40

Greg,

very good point(s).

And certainly, a very subjective and distinctive interpretable question.

Stephan

By OBEWAN

Date 09-12-2009 12:22

I would have voted for SAW. Way back in 1981 I was working for Union Carbide - Linde. I helped qualify some mullti-wire submerged arc processes that I think were for offshore drilling rigs or something that had to pass an ABS low temperature toughness impact test.

The corporate metallurgist helped develop a special proprietary flux that helped the process pass the impacts if I recall correctly, but then maybe the same thing could be put in a coated electrode. At the time, I was just a lab-rat though and was not privy to all the dark secrets. LOL

By GRoberts (***)

Date 09-13-2009 14:43

But was that acid slag flux? Most fluxes designed for impact properties are neutral/basic.

By OBEWAN

Date 09-13-2009 17:11

It was in 1981 and I do not remember. I have been doing all TIG, Plasma, Laser, and EB since then. I seem to remember not acid though. I think we were welding SSS 100 narrow groove stuff.