OK, let's turn our attention from dropped fusible plugs and associated things to another boiler matter--- welding of tube ends at the flue sheet.

Have any of you used MIG welding to perform this task? The question of weld penetration came up at our place recently, and I submit this exchange between one of our volunteers and Miller Welding-----


Question:
While working with the railroad museum I belong to recently, a fellow
told me that Stick gives better penetration than MIG.

This person has some background in the repair of steam locomotives and
may have been told this by an "Old Timer" years ago. He said that they
would never use MIG on any welds to the boiler.

Although I am sure it is not true, I am not knowledgeable enough to
respond with an intelligent answer, can you suggest why he might have said this ?

Thanx,

Bob E-------


Answer:
Dear Mr. E-------,

MIG will provide the same penetration as stick if the welding is done
properly. A poor technique with MIG will not penetrate like stick. Stick
has a wide arc cone that penetrates into the base metal. With MIG the
arc must be directed at the leading edge of the puddle to get good
penetration. When a MIG arc is directed on the puddle there is lack of
penetration. Another wire process choice is flux-cored arc welding.
Flux-cored wire provides good penetration.


Regards,
xxxx
Miller Welding

Now, I seem to recall a number of discussions with various steam jocks about this subject, and I do not remember anyone using MIG for what would seem to be an ideal use-- seal-welding tubes to the tube sheet. Lots of repetition on a job like that, it would seem to be much easier to do it with wire feed-gas shield--- no slag to chip, doesn't put too much excess heat into the tube sheet, etc. So, any MIG anywhere on boiler work? Penetration differences? Your thoughts, please??

Howard P.
ex-hull welder, Electric Boat Co. SSN 690, 692, 694, 696, 697
Groton, CT

Although I have a background in welding I will not profess to be an “expert” but, one of the problems you may encounter with solid core wire are. Whether you use E70S-3 or E70S-6 they both contain silicone that can become trapped in the weld and create small pin holes. The silicone is the clear glassy looking stuff left on the weld. I have made a number of tanks and usually found a weep hole when I was done. Like Miller suggested, I would be more inclined to use flux core like E71T-1, but maybe the “old timers” are right on this one and would be best off with stick. Only my two cents, maybe someone with more experience with boilers has had better luck.


The above is all based on single pass welds, the chances of a hole through milti-pass would be pritty slim.

I'm no expert but I have been told this by pro welders. If both pieces of steel are clean, no rust, paint, oil,ect. than mig is ok. Otherwise you need the flux on a stick to get a good weld.

Howie, when I was working under the ASME Boiler & Pressure Vessel Code mig welding wasn't allowed; that may well have changed in the 25 years since then. But I would still use stick, 6010 or '1109' wire. For one thing, seal welding of tubes doesn't need to be a very good weld - the seal is done by rolling the tube lightly after the welding. What the weld does is transfer the heat from the tube end to the tube sheet.
Also, with stick you can see what's going on in the weld. I've never been able to manage that with mig.

Marty is exactly correct. The weld is for heat transfer so that the rolled tube end isn't burnt off.

The correct weld procedure is 6010 rod downhand starting at the 12:00 position. Don't use to much current, it does not have to be a good weld. It does not seal anything from anything.

He might have some advice on this one.

The sealing of the tube to the sheet is accomplished by the rolling of the tube into the sheet (and we won't get into using copper ferrules vs. no copper ferrules right now!), that is understood. If the tube end weld does not have to be a "good weld", then why not use MIG? It would seem to be perfectly suited for this use-- low heat transfer, and rapid coverage on a very repetitive task. Weld 6:00 to 12:00 on one side of the tube, do the same on an adjacent one, and then skip back to complete the first one.

I know the recommended "old railroad shop" procedure for this was vertical down 6010; what about slag inclusion with that method? Most vertical welding that I'm familiar with has been vertical up, with the exception of running MIG.

And, what about MIG for filling beveled seams in firebox patches?

My background is in non-destructive testing. I learned about weld defects, and how to detect and correct them before I switched to a boilermakers job and was taught to weld to ASME standards. With stick a good welder can tell you exactly where any questionable areas are; he can see, hear, and feel it when he makes a pass. With mig you can't see what's going on in the weld; the most common defect is lack of fusion. You can end up with a nice looking weld that isn't holding anything together. Besides, it's often difficult enough to deal with the stick welding leads in a firebox - I wouldn't want to drag a mig machine in there!

Steel MIG wires contain Silicon, not Silicone. In steel MIG wire designations, for instance 70S6 - what I use in my shop, is 70 - 70,000 PSI tensile strenth, S is the level of silcon in the wire which ends up as that little glassy bump in the end of the weld. In my mind, MIG welding can be a gamble as it can look good on the surface but not be good below. I was told this by a certified welder who did some museum work for us years ago who is also an instructor.

When boiler welding was done on our locomotive (restoring staybolt openings) , E7018 was used. It is a low Hydrogen x-ray quality rod. Penetration is important, but is only part of the story. The welder wanted it quiet while he welded so he could hear as well as see how well the rod was running. I could hear the difference while I was looking over his shoulder.

I have heard somewhere of using TIG to make a root pass.

I am not certified, but from what I know, I personally would not use MIG on a boiler repair unless the code approved it and called out the allowable filler wires. It certainly is easy and cleaner to use, easy way out is not always the best. People have died from using MIG in confined spaces - the cover gas sinks and diplaces the oxygen.

Dear Howard:
The weld on flues (read tubes and flues) at the rear flue sheet is to be a seal weld, not a structural weld. The purpose of the weld is to keep the products of combustion from getting between the bead (or flue end if not beaded) and the sheet. Good penetration is not necessary or desireable.
I have heard of people using MIG, but in my experience, stick is much easier to manipulate, especially on the top and side rows.
The last set of flues that I helped seal weld were on your locomotive, No. 1246. As I recall, Benevolent Bob Carlson and I did them in one night in Scranton prior to opening day in 1985...
J.David
P.S. Who put in your roots at "The Boat"?

JDC:

My roots at the Boat-- did my own. This was on the pressure hull, using HY80 steel with 110-18 1/8" wire. We used a double bevel with a good tight fit-up, and back-gouged the root pass from the other side once there was sufficient weld metal in the joint, and put a good root pass in on the "new" side. Then the Radiological Testing Dept. took the pictures on the third shift. They never did give us prints....

Was the seal welding using MIG that you were aware of, successful or not?

And, is the consensus of those responding so far that MIG welding generally gives less weld penetration than stick, as I originally thought, or is the Miller rep simply blowing smoke? (because they like to sell MIG equipment)

And, I do think very highly of MIG for freight car and coach body repairs; on the Chessie System P70 coach project, we used it to great and rapid advantage on window post and sill replacement work.

Howard, how much did the 1246 operate after receiving new flues? (if you know...)
http://www.railpictures.net/viewphoto.php?id=101899

SH:

Without getting out the copies of the old 30-day inspection reports, I recall a few month's service at Scranton in 1985, and about three months in 1986. Then it was parked for firebox work that never was done. The auction was in October 1988. I don't remember if that 1981-85 work included flues and tubes; in any event, they would have to come out as part of any current overhaul.

HP

Seal welding of tubes/flues can be done with mig, 6010, or 7018. As the name implies we are looking to seal not make a structural, load carrying weld. The main goal is to tie the tube end to the sheet, to help transfer heat away from the projecting tube. This is especially useful when tubes are beaded. Concerns with mig welding is that process does not work well with dirt or oil, while 6010 and to a lesser extent 7018, will tolerate oil/dirt. The oil coming from whatever lube is used on the tube roller. Running 6010 down hill is my preference, but either direction works. It comes down to what the welder is comfortable with.