Heavy weld

[Sberry]

Last night I welded a 2 1/2 inch bar stock on end to a 1 inch plate using my feeder and 035 short arc. It is also gussested. I warmed it first and drilled a hole in the backside for venting. Is there a problem welding these pieces this thick like that? It sure looked good to me and he hasnt called back yet. It was a hitch on a big bulldozer. I was wishing I had a camera for this monster.

[Mike Sherman]

Yes, there is a high potential for lack of fusion on thick members when using short arc mig. Do yourself a favor and use flux core or SMAW when fabricating anything over .375" The rate of return for broken welds will be dramatically reduced if you do. You did a couple of things right in gusseting it and preheating, but given a choice and circumstances permitting I would never weld thick steel with short arc mig.

[deere_x475guy]

Mike....I was wondering about the short arc on that thick of material myself. Being fairly new to mig I was curious about an answer from a pro. I have done that stuff with smaw before on some of my iron hauling trailers years back.

Bob

[Seldom]

Yes, Mike is absolutely correct. In the construction codes and standards I’ve used, GMAW in the short-circuit transfer has far more limitations applied to it then anyother process or mode of transfer. All because of the fundamental characteristics of it’s low heat input and lack of the operators ability to see fusion and to verify it.

I passed my first ASME, Sec IX pipe test (5”xhy 2G & 5G) back in 1968 and can tell you since that time I’ve witnessed and observed some absolutely scary failures attributed to GMAW-SC by “experienced” pipe welders! These by experienced pipe and boiler welders not home hobbyist that seem to be buying these machines like crazy in the last 10 years. I’ll tell you this and I’m dead serious, when I find myself driving behind a homemade utility trailer today, I get the heck around him darn quick!

As an example of what can and does happen when an “experienced” welder makes a mistake in technique with GMAW-SC- Take a simple 3/8” fillet test in the flat position, I watched the fella clean his plate to bright metal, put in a root bead and add two stringer to finish. He pointed out how great his weld looked and it did except I informed him it would fail. I took it out of his fixture and dropped it on the test both floor. It broke apart on two pieces by dropping it 4’! Absolutely NO penetration in to one leg! I had watched him during the whole weld sit back on his puddle about a 1/16-3/32” and float the weld on. With GMAW-SC, a 1/16” difference will make the weld or break it!

GMAW is the easiest to run but the it’s the hardest common welding process to run correctly

[deere_x475guy]

Seldom..where are you in central MI..I am in Holt and a couple of other guys...(Will in Grand Ledge and Aaron in Jackson).

More Mi guys...

Bob

[Sberry]

I could see it burn into the base really well and was concerned from what I read here so I watched to make sure,, as Seldom said,, so I didnt float it on. It must have churned up 3/32 into the base and I look into and in front of the puddle for fusion as it was happn. It was put on stress test this morn and no problems under use. It was way heavier than the connection it was bolted to. If I was doing much of it I would probably have another machine set up with innershield for it. I do very little heavy work since I quit Ironworking but I could count on one hand easily the weld failures in the last 20 yrs. One was 7018 on a violently vibrating pumping unit but I had blew a couple holes and put a couple 7/8 structural bolts in just in case as I wasnt the designer of that managerie anyway. I later corrected the underlying reason when they were not there to "help". Given the chance I try to eleminate hi joint stress in the design to start with. Is there much other metalurgical concern besides fusion? My bud was working for tiling company and said they had some impact failures with common wire but in my stuff it certainly hasnt been a problem.

[Seldom]

Originally posted by deere_x475guy
Seldom..where are you in central MI..I am in Holt and a couple of other guys...(Will in Grand Ledge and Aaron in Jackson).

More Mi guys...


Bob

Hi Bob, I'm born and raised in Midland Co. My profile states who I worked my career with.

Sberry27,
You said- “Is there much other metallurgical concern besides fusion? My bud was working for tiling company and said they had some impact failures with common wire but in my stuff it certainly hasn’t been a problem.”
I’m not a metallurgist but from what I’ve learned, observed, read about, and been told by my old employers’ metallurgist, the GMAW-SC weld deposit itself is a nice fine grain microstructure structure typical of most other low-hydrogen weld deposits.

The chronic problem of GMAW-SC isn’t exactly its inability to penetrate; it’s the low arc heat it produces that limits fusion. Heavy weldments act as a heat sink and literally prevent fusion by rapidly pulling the heat away from the arc before fusion can take place. Mill scale, rust, paint, etc. actually prevent fusion because they reflect the heat away from the base metal thereby preventing fusion form taking place. By simple virtue of sitting back on the puddle disallows what little arc force SC has in addition to acting as its own shield/insulator between the arc and the base metal from fusion. On top of all of these things I’ve mentioned there’s still the problem with weldments that aren’t normally considered “heavy”. It is a proven and documented fact that base metal thickness of differences as little as a 10% increase requires an increase in the Volt/Amp ratio. Many welders either doesn’t know, understand, or really care, and will weld a variety of thickness without regard to readjusting their machine in order to compensate.

Penetration and fusion are two different animals (terms) and sometimes folks get them confused. GMAW-SC doesn’t penetrate (depth of fusion) as deeply into a base metal surface as say an E7018 electrode but as long as each process accomplishes a melting of filler metal and base metal, there’s fusion and therefore a weld happens. Just because SC doesn’t have a pronounced depth of fusion as our example doesn’t make it a less strong or substandard weld because fusion is still fusion regardless of the depth. It’s just that GMAW-SC has so many more things that negatively impact that fusion.

These are great questions for a welding process that is chronically misunderstood.

[deere_x475guy]

Seldom...do you know Will Lane? He was an electrical engineer for Dow at one time I believe. He is on this board often.

Bob

[Sberry]

I certainly agree with the statement about penetration and fusion and have actually made that statement on this forum a couple of times. When I did this job last night I did take the advice from this forum under consideration and made a point of paying attn that there was not a cold joint and had the power cranked as well as wanting to finish in record time. Thanks for the input.

[Seldom]

Hi Bob,
Nope, I don't think I've run across him. When I left the welding ranks in the mid-80's and was hired into the Welding Engineer Dept. I usually worked with Mechanical (piping & pressure vessels), Civil (structural steel) and Material (Metalurgist) Engineers.

[Seldom]

Hi Sberry27,
You're welcome.
By the way, you did absolutely the right things to help achieve a fully fused and strong weldment.