cassidym
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| posted on 15/7/04 at 09:55 PM |
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Mig welding technique
Guys, I have read thro the archives and am happy to say that I have picked up a lot of tips.
My 1st question is should I use the push or pull technique when Mig welding? I know all the literature recommends pushing - my problem with this is
that I find it very difficult to look into the weld pool as it is obscured by the torch. Actually I do'nt know whether to look in front of the
gun/torch or behind it for the weld pool. I've read somewhere that the weld pool is about 10 mm behind the tip of wire - which may be bollocks.
I've been to a few shops and the guys all use the pull technique, which is what I'm currently doing - having a nagging feeling that it is
wrong.
I always feel very calm and in control when I can clearly see the weld pool - that is why I sometimes fire up my oxy set - but with MIG sometimes I
see it, most of the times not.
My 2nd question - in a few posts there was mentioned that the gun should be held at 90 degrees to the material. I think 90 degrees will be much better
as the weld pool would be more visible. Currently I always use a 70 degree angle and some other guys recommend even 45. Should I try 90 degrees?
I also appreciate Mark's tip on using the thumb to steady the gun/torch.
Thanx.
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Mark Allanson
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| posted on 15/7/04 at 10:23 PM |
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90° is the ideal angle for the weld quality, just look at an automated CNC controlled MIG in action. The various torch angles are to optimise gas
coverage, the problem with drawing the torch is that you are flowing gas over the weld you have already laid down. Most users have the gas turned up
too high, not a problem, if a little wasteful, so drawing the torch is not a problem as long as the angle is not too acute (as this would deflect the
penetration into the existing pass and not the workpiece).
If you are having trouble seeing the weld pool, move your head! or get an EW9 filter which is ideal for the level of power used in chassis welding.
Try doing a dummy run on the pass before you do it for real, just to check you can twist your arms/wrists to the required angles!
The best thing is practice, many beginners are nervous of the whole thing and shakey welds are never good! Familiarity with the process breeds good
welds
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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spunky
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| posted on 15/7/04 at 10:51 PM |
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Everything that Mark said is how I was taught. What Iv'e found to be the most important is a really good pair of gauntlets, so you can get close
to the gun tip and hold everything steady throughout the pass.
John
The reckless man may not live as long......
But the cautious man does not live at all.....
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cassidym
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| posted on 15/7/04 at 11:10 PM |
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90 degree it is then. I usually try to get as close to weld as possible - thought I was crazy.
Mark, forgive me if I'm being silly, but it seems to me at 90 degrees it really does'nt matter whether you push or pull coz 50% of the
gas is blown onto the existing weld and 50% on the preheated area either way.
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derf
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| posted on 16/7/04 at 02:39 AM |
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I find that the push produces better quality welds, and I do my best to get my eyes level with the weld surface so I can look at the puddle, sometimes
the weld position is uncomfortable, but the welds usually look real good.
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Mark Allanson
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| posted on 16/7/04 at 06:59 AM |
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Gauntlets, screwfix do a great set of kidskin ones for £3.99 (useless info if you are in South Africa or New Jersey!!).
I usually 'push' at about 80°, just to give greater vision of the weld pool, on thinner metal (20g or less) a greater angle can be a good
idea if you want to reduce the penetration without stopping to alter the power.
Cassidym, yes 90° is neither, its just good welding
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Browser
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| posted on 16/7/04 at 07:15 AM |
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Teh thing I find helps me is getting your eyeballs as close as the work area & headscreen will allow to the weld area, allowwing you the best
possible view of what you are doing. Welding is like many hand skills, practice practice practice. I've been dabbling now for the best part of
17 years and ma only just reaching an acceptable standard (to me anyway).
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BradW
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| posted on 16/7/04 at 03:15 PM |
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Cassidym.. Check out Makro for the pig skin gloves, I got a lovely pair, I think they were Eurasia, and they were pretty cheap too...
Just don't get hold of metal too close to the weld as they do brun through :-), good job they are cheap....
Brad
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NS Dev
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| posted on 27/7/04 at 04:54 PM |
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probably just repeating stuff from above which I havent read properly, but the key things for me with MIG welding are start really slow until you know
what you are doing, just keep the feed really steady and build up speed, rather than the other way around, then definitely use a shade 9 lens, I am
used to using these and anything darker gives me trouble now! Lastly I find that push or pull depends to some extent on what you are welding, I tend
to find that I pull on thin stuff which helps avoid burning through, but push on thicker stuff to help penetration. I nearly always work with two
hands on the torch (right hand on the trigger and left hand steadying the shroud), with the shroud pointing to the left at about the 70-80 degree
mark, and class push as moving left with it like this and pull as moving right with the torch held exactly the same.
[Edited on 27/7/04 by NS Dev]
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Mark Allanson
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| posted on 27/7/04 at 06:28 PM |
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I usually use my torch like a snooker cue, torch in right hand, left hand fingers guiding on the work and thumb or back of left hand steadying the
torch
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Tigers
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| posted on 28/7/04 at 09:09 AM |
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Hi MIG welding gurus!
May be you have a suggestion to me...
It seems that my welds have slightly too much metal over the surface. I mean - seam is not flat, it's quite rised. Is it very bad?
I have read that you get better penetration if you use CO2, less if you use Argon - CO2 mix (I use it - 80% argon 15% CO2 and other addititons). May
be I'm going to slow along the seam or the wire feed is too high (but it should be quit high to put more energy into the weld to get better
penetration). Or maybe gass flow is too high (currently 9l/min).
I don't know should I worry about that. Probably it's not a problem in 90 degree joints, but in places where I have to grind off the weld
flat (where I have to put body panels over it), it might become quite week, right?
Thanks,
Janis
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NS Dev
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| posted on 28/7/04 at 04:30 PM |
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Tigers, you don't get better penetration from CO2. CO2 conducts heat better than Argon or a CO2/Argon mix, therefore will take heat out of the
weld and give less penetration, not more. I use CO2 for thin sheet work as it takes heat away from the weld making it easier to control without
burn-through.
To get a "flatter" weld with more penetration, turn current up and wire feed down. This is not always easy on cheap MIG sets with not many
current settings but it is the correct approach.
To take this to the extreme, and Mark Allanson will no doubt sometimes have use for this technique, when welding really heavy sections with a big mig
set, you can turn the wire down low and the current up to the point where you get "spray" transfer (instead of normal MIG
"short-circuit" transfer) where the mig wire is vaporised by the reflected heat from the arc and the weld pool and the steel vapour is
literally sprayed at the workpiece. You will know when this happens as it makes a lovely smooth hissing sound. We used to do this when welding 30mm
plate with a 700 amp mig to make prototype pressbrake tooling where I used to work. For this sort of work a water cooled torch becomes a definite
advantage!!
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Tigers
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| posted on 29/7/04 at 03:37 PM |
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Thanx! I will try to reduce wirefeed and increase amps then.
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Mark Allanson
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| posted on 29/7/04 at 05:38 PM |
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You wont get true spray transfer at anything less than 300A, but you can get close with about 140A and reducing the wire feed progressivly until the
weld sounds like a hiss rether than a crackle, you can produce excellent welds using this technique, but can produce spectacular distortion. The only
problem is that you are a knats scrotal hair away from balling the wire back into the contact tip, so try it out on scrap first, and have a few spare
tips handy
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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