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Up Topic American Welding Society Services / Technical Standards & Publications / Need some help/advice with an odd situation
- - By jwright650 (*****) Date 01-27-2010 13:08 Edited 01-27-2010 13:12
I was trying to help someone develope a few welding procedures (D1.1) to satisfy one of their major customers and I ran up on a situation where I feel isn't per D1.1 perse'.

There is a weld on the fabrication(a very large transformer) that is about 10-12' long, a continuous seam where they have a formed 3/8" bent plate(non-structural so they say) that is square-butted together and welded (on just the outside)"as is" with a 3/16" E7024. They just want to seal this joint, so they have been using an E7024 because of two reasons:

1) fit-up is inconsistant due to the bent plate may or maynot be butted tight at the joint. E7024 accomadates this very well and the cap still looks good compared to a E7018 or E7028.

2) the welders want to use the E7024 for the appearance of the non-ground cap, and they have had porosity issues in the past(due to the poor fit-up) with other methods. This joint has to be 100% leak free because it contains a very thin oil that is used for cooling.

I've gotten them up to speed on everything except this issue. I've suggested two things so far, but I need to research some before continuing any further:

1) qualify the procedure with a PQR (not even sure what is involved until I dig into this one a bit deeper since it isn't lo-hy)
2) cut and etch a sample or two to verify the depth of penetration and get their engineer to sign off and seal this procedure.

Any advice or thoughts?

EDIT: I might add that they have been in business building these transformers for 50 years and have been doing it this way forever.(You guys know what I'm up against here with this one.(reluctance to change is a strong force)
Parent - - By spots (**) Date 01-27-2010 14:22
As they are using E70XX I am assuming their tensile strength is not an issue. Per table 4.12 7024 & 7028 are both group F1 filler materials.

The joint you describe sounds like prequalified joint BTC-P10 could be used if they seal their "tank" on the formed side and their root opening does not exceed 1/8".

The 3/8" plate is well over the 1/8" lower limit of D1.1.

So far I am not seeing a deal breaker for D1.1.
Parent - - By jwright650 (*****) Date 01-27-2010 14:47
The joint is more like B-P1c...rather than the BTC-P10. The max thickness is 1/4" for that joint, and materials are A36 and sometimes A572 gr50.

I'm thinking that I will need two tests for the PQR.

One per 4.11.3 consumables verification test that is similar to Fig. 4.21(except 10" long per Fig 4.23), to get the two side bends, and AWMTS specimen.

and the second test resembles the joint to be used in production per Fig 4.11.

Do you guys agree with this?
Parent - - By Lawrence (*****) Date 01-27-2010 16:45
Hey John,

Can't say as to the PQR's  sorry.

But if they are fabbing...  Why SMAW?

Wouldn't an E70T-X FCAW be a more productive and forgiving choice for 3/8".   Even with a bit of inconsistancy in the root opening, I bet the nice toes produced by an E70 FCAW would make welds as pretty as the SMAW and definatly have a deeper penetration profile.

If it could make the profiles you need it would sure be more productive/profitable.
Parent - - By jwright650 (*****) Date 01-27-2010 16:50
Lawrence,
You and I must be thinking alike...that was my first question when I saw that long joint. Like I said the reluctance to change is a strong force. I feel like I could weld circles around these guys with FCAW. They use 1/16" FCAW  for all of the fillet welds (single and multi-pass) and they all look great. They had porosity issues and tank leaks when they tried FCAW several years back.
Parent - By jwright650 (*****) Date 01-27-2010 16:58
Talked with the lab and they agree with me about the two tests required. So now I have some direction to get this PQR started and was able to let the fabricator know what the cost of the lab work would hit him for. Sit back and wait now to see where this leads me. I have a feeling that it might get cut short as soon as I make a few saw cuts and macro-etch. I can't imagine that they are getting the penetration that they think they are...but, I've been wrong before....LOL

Now, I need to get their engineer to pin down the depth of penetration that he needs.
Parent - - By jwright650 (*****) Date 03-01-2010 16:34 Edited 03-01-2010 16:41
Got back on this project and realized that I was mis-informed on the welding of this joint. It is indeed welded on both sides instead of how they originally described it.

Here are a couple pictures where I cut and etched the joint.....I'm having their engineer review these pictures due to the lack of penetration. Also it appears that there is a lamination about midway through thickness of one of these plates.



Parent - - By HgTX (***) Date 03-01-2010 17:35
What was the penetration supposed to be?  Or was that somehow supposed to be a CJP?

You really think that's a lamination and not just the more common "centerline accumulated yuck"?

Hg
Parent - - By jwright650 (*****) Date 03-01-2010 17:49
Not sure....speaking of the question about the lamination. I've etched alot of cross sections and haven't noticed a difinitive line like that one before, maybe it is just centerline accumulated yuck.

It is supposed to have 5/16" depth of pen per the engineer, and this is far from that.
Parent - - By HgTX (***) Date 03-01-2010 19:44
You must have better plate suppliers than I do.  I see lots of centerline yuck.  (I'm sure that is the proper technical term.)

Hg
Parent - - By jwright650 (*****) Date 03-01-2010 19:48
Hg,
Can you find "it" with straight beam UT?

I would try to look at these with my UT, but I met the guy at lunch and gave him the samples to take back to his shop.
Parent - - By HgTX (***) Date 03-01-2010 19:59
The yuck?  Not typically, unless it really is a yuck-filled lamination rather than relatively sound steel with a high concentration of impurities, which is usually what it is.  Laminations tend to blow out when they're cut through, so they look a little crusty.

Centerline yuck is pretty much the reason base metal charpies are taken from the quarter points rather than mid-thickness.  I believe also that non-laminated yuck can still be a source of delamination under through-thickess stress (like a cruciform joint) because it is a weaker area but I feel less secure in that assertion.

Hg
Parent - - By eekpod (****) Date 03-02-2010 12:34
John, what process was used to weld that?
Parent - By jwright650 (*****) Date 03-02-2010 13:47
SMAW, non-low high E7024
Parent - - By jwright650 (*****) Date 03-02-2010 14:08
How are you with SAW setups?

I might need a little help from the SAW savy folks, if SAW is feasible with this realitively thin material, 3/8" and talk of possible 1/2" in the future as these monsters are growing in size as this company gets further into this transformer market.

The weld shop is kinda resistant, but I think I might be winning them over slowly. I've answered some of their fears with (what I think) reasonable options for using FCAW or some other semi to automatic welding process. These joints are so long, and I feel like I can pick up some speed in this operation, especially now that I see that they weld inside and outside of this joint. It's hard to convince people that this E7024 isn't the best option when they have been doing this for in excess of fifty years this way. The etching I think will help move them away from that shallow penetrating rod. We'll wait and see.

I think they(the welders) just need a little coaching to get them to like the FCAW on the 3/8" or possible SAW for 1/2" material.
Parent - By 803056 (*****) Date 03-02-2010 15:07 Edited 03-02-2010 15:13
They might be more receptive the GMAW spray mode transfer because there is less capital investment required and minimal learning curve to switch from SMAW to GMAW. GMAW means less smoke than with SMAW and it will not require the need for flux and flux handling equipment. FCAW will be smokey with considerable spatter compared to E7024, E7028, or GMAW -spray mode transfer. Since these are relatively long joints, welded in the flat position, GMAW - spray would be a good fit.

You did mention the root was inconsistent and that may be why they opted for the shallow penetration of the E7024 electrode. The work around would be a root pass of (I hate to even type the words) gmaw - short circuiting transfer to close the root, followed by a pass of spray transfer.

If you go with a 90/10 argon carbon dioxide mix you can increase the penetration easily. If they use 0.045 inch diameter electrode they may even achieve close to CJP without having to back gouge. Argon / Oxygen may reduce the width of the weld while increasing the depth of penetration. I usually stay with the 98% / 2% mix with good results.

The major drawback will be the intense heat, but if the welders are given the appropriate gloves with aluminum-coated pads and heat resistant jackets (welding jackets) there should be minimal resistance. The danger of course is the welder's urge to reduce the heat by going into short circuiting mode. That can be prevented by purchasing a power supply that "locks" the parameters. I have gone as far as installing a potentiometer connected to nothing to give the welders something to adjust. Welders just love to turn knobs, do not know why. It must be in their genes.

We used GMAW -spray on the rebar last week (remember the photos), they easily achieved 3/16 inch penetration into the rebar. We used Miller CP-200's, but I would recommend something a little more robust for your application.  Do not go with a pulse capable machine. It is not needed for this application and will only lead to headaches down the road.

They may be more receptive of SAW and the capital investment once they see the improved productivity of the GMAW. The welders will appreciate the improved comfort of welding with SAW and will be less likely to see it as an attempt by management to eliminate their positions.

Best regards - Al
Parent - By Lawrence (*****) Date 03-02-2010 15:16 Edited 03-02-2010 15:26
Since we are talking about process control again..

A fellow I know has been having great succsess on similar joints using .045/.052 MCAW..

If you have the leisure to do some trials this may be something to look at.

It runs so much like traditional spray mig that your old dinosaurs may be more willing to look at it.  It runs a push rather than a drag agnle of FCAW so the operators can see what they are doing much more easily to track the joint.  MCAW penetrates just about as deep if not deeper than FCAW and way better than the SMAW your currently using.

If you are making a bunch of these things for a long time than maybe SAW might be worth the investment of time and equipment.

Anyhow ... Just a thought.

Edit:
I see Al is thinking along similar lines but with solid wire..... And said it alot better too  :)
Up Topic American Welding Society Services / Technical Standards & Publications / Need some help/advice with an odd situation

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