Solutions for underpowered MIG?

[shenion]

It made a big difference on my 1/8" with the 130. Diff between weld with little penetration even with a small gap to full penetration.

Then again I was just pushing the thickness up by 25%. It does also help fusion.

You won't see it in industry as it is non productive. Much better to just get a better MIG.

Yeah, arc is nice as it puts more heat and you have more control.

 

[snowcat]

You won't see it in industry as it is non productive. Much better to just get a better MIG.

.

Ahhh but it would surely be a "procedure" then in large structural welds, It would be no less productive than putting multiple stringers in to aid pen, Or grinding massive J preps... In my experience welds following a WPS, often are not production orientated.. more about best practice for the job

 

[Drains]

Got to say...
You can't do a valid bend test of a 3mm weld on 6mm plate. Obviously the weld will give before the plate does.

See with the preheating thing. Taking the chill off the metal will certainly help, and may lower the chances of cold lapping. On very thin sheet, we all know that as the sheet heats, you must travel faster or burn through, or if stick welding, do something, like shortening the arc, flicking, changing electrode angle etc
I would have to agree, on the whole, that a preheat will help an underpowered set get the penetration required.

Snowy, your test was so gay.

 

[ozzman]

course pre-heat makes a difference, as they grain structure of the metal starts to grow, so when you start welding the welder hasnt got to put as much heat in at the start of the weld to get decent pen.

i would of thought the reason why pre-heat is not used is beacuse it could lead to more distortion of a welded part, unless you could pre heat the whole part before welding commences.

oh yea my tutor at college always goes on about pre-heating to aid pen. and it makes a hell of a lot of difference of T-fillets.

on 1 of the first fillets i ever done it was 6mm plate and i got zero root fusion, there was actually a worm hole the entire lenth of the root. got lovely side wall fusion tho,
then seconf attemp i pre-heated it and got perfect pen and a much nicer profile as it burned in loads better.
also when doing our 10mm t-fillet test peices the paperwork that with it specifies that the joint is pre-heated to aid penetration.

its just not practical to pre-heat at work tho due to the time and gas required unless your welding proper thick sections with a Mig. which lets be honest who would wana do that, as we all know Migs are crap for heavy work.

MMA is far superior for heavy stuff, and i personally think its easier, as you aint got to think have i got pen? you just know you have.

 

[snowcat]

Got to say...
You can't do a valid bend test of a 3mm weld on 6mm plate. Obviously the weld will give before the plate does.



Snowy, your test was so gay.

The bend test was really a red Herring not valid in any shape or form, I just wanted to see If it welded differently Hot, Hmmm 3/8" 6mm??????? maybe with Scottish verniers..

The problems I have are the complexity of the subject, and as far as I can understand, LCMS is only ever heated to avoid HAZ cracking from the welds and to de stress, and reduce hydrogen content, Thus down to the shock from cold to hot, and also keeping intercept temperatures slow to cool allowing hydrogen release, Exceptions to the rules are normally high carbon steels, used within the nuclear industry....

I know this to be FACT as preheat and intercept temperatures are AWS books in there own right, I can only work at a very much a layman's level and the more I read the less I understand..

I am more than willing to be proved wrong on the matter, but Intel I find a TWI/or AWS case study on the effects of x amount of heat/ achieving X amount of improvement, on LCMS then I find the proof hard to swallow.....

and Dude I am the only Gay in the Village.....

 

[snowcat]

After spending far too long getting my moneys worth out the TWI membership, and the AWS site, there seams little evidence that preheat effects penetration to any sinificance....

However thats not to say preheat does not improve the attributes of a weld.. but again heating temperatures, materials, applications all have there own recommendations, case study and experiments are all different, the problem seams and some guys were preheating at an interpass temperature of a 1000c for rooting pipes with the TIG this will aid pen but problems were occurring with HAZ cracking further along the pipe, at an average interpass temperature of 89C-200C the material still has another 1400degress to go to become fluid.......
Really It will aid the weld but simply the reasons are to prevent stress, HAZ Cracking and Hydrogen, and too create proper fusion all other parameters need to be correct as well including OVC.......

and ozzman preheat is very common in industry, often part of the WPS, and often set by the Institute, according to material.......and is used as part of preventing HD...large thick lo-Hi joints ARC'd joints often require the most attention to preheat.......

So IMHO Yes and No preheat does kinda work, If your really want to go into detail then join the TWI, and confused read the AWS stuff......

Right, I'm off for a pint......

 

[Drains]

Hmmm 3/8" 6mm??????? maybe with Scottish verniers..

Aaaaargh

I got it wrong again dad.

 

[ozzman]

yea i know the feeling with the confusion!!! i always am!!

and yea i would say your more than right, i just go on what my tutor and AC davis says at that moment, not that i looked in ac davies about pre-heat.

but as i say my tutor runs on abit and does seam to think he's the best welder in world and knows everything, so i just usually on what he says, and he wreckons pre-heat makes loadsa difference

but well he does seam a bit of an idiot
anyways im off for my sunday lunch

 

[Drav]

Oh God what have I started?!

 

[snowcat]

yea i know the feeling with the confusion!!! i always am!!

and yea i would say your more than right, i just go on what my tutor and AC davis says at that moment, not that i looked in ac davies about pre-heat.

but as i say my tutor runs on abit and does seam to think he's the best welder in world and knows everything, so i just usually on what he says, and he wreckons pre-heat makes loadsa difference

but well he does seam a bit of an idiot
anyways im off for my sunday lunch

If i was a mythbuster ozz, id say plausable?...

Your tutor certainly wouldn't be completely wrong whatever, and maybe lack of HAZ cracks and hydrogen can be directly linked to penetration??? He could well know far more than me (not hard)

Best welder in the world, hmmm know pleanty like that...........

Anyway I give in on this subject, It's got me thinking far too hard about some of my own procidures.....

and Drav your get used to it although I'm sure theres only a few on here that are normally in the thick of disagreement and getting far to technical for no good reason......Il stick myself in that catogary.....Il leave you to decide who else Gets involved......

 

[malcolm]

Preheat is a work around for when you don't have suitable equipment. Should imagine the books and weld procedures start off assuming you have suitable equipment, and don't offer workarounds. They'll never say "Ideally weld at 27 OCV.... but if your welder doesn't go up that high then preheat a bit and go for it at 24 OCV and it might be good enough". That's just not the sort of thing these books are going to say.

The workarounds come about with hobby welding where you often don't have the right kit. We can share experiences but none of us are going to follow a procedure or write a book.

Snowcat - Try welding some 2mm sheet. Set your welder up so even with your best technique you only just can't get decent penetration until you've welded an inch along. Then try again with preheat and see whether it still takes an inch of welding for you to be happy with the weld.

We've got a bit UKW on this which stifles imagination.

 

[snowcat]

Snowcat - Try welding some 2mm sheet. Set your welder up so even with your best technique you only just can't get decent penetration until you've welded an inch along. Then try again with preheat and see whether it still takes an inch of welding for you to be happy with the weld.

We've got a bit UKW on this which stifles imagination.

Nahhh il take your word on it Really iv got no machine I can set for anything as thin as that other than the TIGs,

As I say I'm sure its possible, just with a high enough preheat temp, thin plate would be easy to get really hot quick, I'm normally on preheats of 200C max......So thats the ball park I was working on.......

The TWI and the AWS do some interesting studys and field work some of it very odd ball, with parameters way outside a normal comfort zone.....not just "best practice" type stuff........Intresting reading some of it.....

Personally If id had those set of options the flux core would be my weapon of choice.........

If you say it works for thin plate that'll do IL bow down gracefully, and rejoin the ARC and TIG sections, where I'm in the comfort zone.......

 

[novaweld]

I think I've got some 2-3mm plate bits in the garage somewhere, If I can find them I might have a go at butting them together with my 90EN.