Ran some SST for fun today. Fit-up suggestions?

By Lawrence (*****)

Date 04-23-2014 13:28

My experience with STT is that root faces and gaps are very similar to short circuit GMAW... The STT is just more consistant in all positions due to the CC/CV type of arc.

STT will deal with thinner root faces or inconsistancies a little more nicely than Short Circuit...

By spgtti

Date 04-24-2014 00:19

Try that size land with a 5/32" gap, wire speed around 165ipm, downhill progression

By Stringer (***)

Date 04-24-2014 22:22

Seems like once we go too wide with the gap the overall weld and heat would increase unnecessarily but I guess with this new SST that it's so cold and fast it doesn't matter that the weld is 'wider'.

By Lawrence (*****)

Date 04-25-2014 13:32

STT has a number of advantages.

If you are doing high volume production runs, STT will allow for a thinner root face and a more narrow root gap... Even a slight change here will reduce weld volume, cycle time and consumable use in a way that can produce ROI to justify the cost of the machine in far less than the typical 2 year window.

With a two step gun/trigger system that open root pipe weld of any thickness can be welded all the way out with a combination of STT and Spray/Pulsed modes without ever stopping or very minimal stopping.

By Stringer (***)

Date 04-26-2014 03:11

Well, that's what I'm trying to get a handle on. Weld volume vs wide enough gap to get the root in. I was very impressed with the penetration/heat/narrow gap ratio watching a root go in by another welder (operator). I would have bet it was too cold and too narrow to do any good at all but I was wrong. Instead of immediately clogging the bevel and climbing out of the bevel like a 'too cold' short arc rig, the penetration seemed to stay deep and fused.

By Lawrence (*****)

Date 04-28-2014 20:59

If you are doing trials to get yourself in the right ballpark for PQR's and are asking yourself questions like.

Minimum included bevel angle to reduce weld volume?

Root face that can be most consistantly prepped?

Root opening that matches root face best for consistancy and volume?

Filler wire size to optamize cost per ton with STT/GMAWP ? (you might be surprised how well .045 does on open roots)

Lincoln has this data for just about every joint configuration, diamater and alloy available and are darned willing to share with folks who buy their stuff. Sometimes they just give it away... Sometimes they would like to do a seminar in Atlanta or Cleaveland.... I've done both and it has been well worth the time.... Some local Lincoln reps have this data in their back pockets and some don't..

They also have great spreadsheet formulae for estimates and backed by production monitoring via *CheckPoint* or just typical gathering methods.

So I guess I'm saying that a good bit of your work may be done. If your Lincoln guy seems unqualified or uninterested PM me and I'll give you a name :)

By js55

Date 04-29-2014 11:55

It has always been my opinion, and I have yet to hear an argument to dispute it, but if all you are doing is carbon steel and low alloys STT (or its variants) is a waste of money.
If you are rolling high alloys STT is a waste of money.
Where the process really shines is high alloy position pipe, and thin materials.

By spgtti

Date 05-01-2014 20:08

You speak from hands on experience or from an analytical/engineering standpoint? Just curious.

By js55

Date 05-01-2014 20:21 Edited 05-01-2014 20:43

Both.
The standard CV guys didn't just sit on their hands wondering about the future of their employment while Lincoln was out over-marketing STT.
Where it really shines is in the fast freeze characteristics of the wave form. If you are welding standard carbon steels and 1G pipe you don't need fast freeze, and you don't need that fancy wave form.

By fschweighardt (***)

Date 05-02-2014 01:12

I'm with Jeff on this one, if you are rolling pipes/vessels, plain old short-arc is hard to beat for the root pass on plain carbon steel. Its fast, and the quality can be as good as the operator. Not all customers will take it, but when conditions allow, its really slick

By js55

Date 05-02-2014 12:07 Edited 05-02-2014 12:09

Standard CV is such a easy effective process I literally, and I mean literally, fell asleep one time (after a particularly rough night) running a 36 inch root at about 9:00 on the pipe seated on a stool. I woke up when my head hit the pipe.
We demo'd one of the earliest production models of STT, perhaps a gamma prototype, I don't remember. In any case we recognized immediately what the technology could and could not do. It is awesome for position work for high alloys. But it should never be considered to completely replace standard CV.
Lincoln argues the plasma boost saves the current cut off. I disagree. The plasma boost is necessary to prevent lack of fusion, but it isn't enough to match the abilities of standard CV.

By spgtti

Date 05-03-2014 21:45

If CV is easy, STT/RMD just makes it easier. Welders don't have to have the skill level to keep the wire placed at the leading edge of the puddle. Roots show more reinforcement in the overhead position. All I have to do is press a button on The Miller Fieldpro or roll the dial on a Lincoln S350 past the standard CV MIG setting and I'm slamming in perfect roots in the field.
We have a couple of the old STT only systems, and I agree they're lacking in alot of areas. The new machines all run standard and modified short circuit, along with pulse MIG and any other manual process.
Given a choice on open butt MIG root pass welding, modified short circuit in whatever manufacturer name given is the way to go.

By js55

Date 05-06-2014 13:37

spgtti,
I would agree with your point about position work, as I stated above.
Also, "the skill level to keep the wire placed at the leading edge of the puddle"? I have trained hundreds of entry level welders short circuit GMAW over the years. We even had a program at one company I worked at that would have the office people come out into the shop and weld to have a better understanding. I have yet to see one single person that couldn't handle the process if it is carbon steel/low alloy in the 1G, which is probably >99% of the application out there. This hardly justifies the price.

By js55

Date 05-06-2014 14:02

And actually rolled GTAW can be even faster. Not to change the subject.

By spgtti

Date 05-07-2014 20:46

1G rolled is so yesterday for GMAW. It's heavy in the field now and only going to grow. Bring your office welders and we can put 'em to work!

By js55

Date 05-08-2014 11:59

spgtti,
LOL!!!
That's good.
Yeah, so yesterday however, that it is still 90%, at least, of the short circuit GMAW activity globally.
I suppose you would argue that SMAW is so yesterday as well since it has been around so long (might want to tell Lincoln since they mistakenly sell 10's of thousands of tons of the stuff every year). Or maybe alloys such as monel or duplex SS are so yesterday since they were first developed at the turn of the century and the late 20's.
And I suppose you sit riveted to the research sections of the Welding Journal as it churns out article after article about laser beams and electron beams sneering at the ancient big five processes, ignoring the fact that the Journal has been roundly criticized for such because these processes still rule the world of welding and will do so for the foreseeable future.
Actually it is soo yesterday to criticize the work horse processes as so yesterday.

By Lawrence (*****)

Date 05-08-2014 12:26

This is funny JS..........

I had a 90 minute phone talk with Ed Craig yesterday, he is retired, but we still chat and welding still dominates his thoughts.

He ruthlessly took me to the woodshed about several "whistles and bells" I have allowed salesmen to impress me with.

He spent the bulk of our talk, framing a set of trials and commanding me to put down my regular duties and carry them out so that he could be proven right about the chewy goodness of 45 year old CV GMAW technology.

He said something along the lines of this: Whether its Short Circuit Mig, Rapid Arc, STT or CMT, the amount of energy it takes to make the open root groove weld is exactly the same" "The energy required to fuse and fill the metal does not change !" I must concede his point is true.

What a wealth of knowledge and experience this guy has... Both on the scientific side (where the rubber meets the road) in shield gasses and foundational work on GMAWP, which he is warming to just a small fraction. Ed was one of the early pioneers of GMAWP, had his work stolen by a major (red) player and then came to the realization that for many reasons regular CV GMAW is the best way to go for most welding.

"So yesterday....." "Works good, lasts a long time" are things not to be taken lightly.

By js55

Date 05-08-2014 13:05

Lawrence,
I am looking at Ed's well worn book on Mig Welding sitting on my bookshelf as I type these words. I am not sure I agree with everything Ed argues but I am indebted to him for the very things of which you indicate. A little skepticism on bells and whistles, and gases. And he is a brilliant guy.
In the context of STT and other technologies it is not that these technologies do not have value and have not improved applications. The problem is the over aggressive/panacea marketing that follows after its introduction. I have no doubt it drives him as crazy as it does myself.
It is also an interesting coincidence that just yesterday I had lunch with a good friend that spends a great deal of time researching welding technology and he clued me in to even more problems with new technologies and applications wherein the machines of yesterday simply kick the new machines azzes.
Don't get me wrong, as in another thread wherein I stated my support for the CWEng certification with limitations, I herein support STT/RMD or whatever, with a sober understanding of what the technology is able, and unable, to do.