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MIG Welding


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  #1  
Old 12-06-2017, 01:34:00 AM
cobbadog cobbadog is offline
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Default MIG Welding

Hi guys,
I'm new to this section of this great Forum as I usually hang out in the magneto and Smokstak down under.
I own a welder and it has been set up and used as a gasless continuous wire welder. Whether it was me or simply the type of welding, gasless, that was giving poor results. So right now I am converting to run the mixed/blended argon gas and the correct welding wire. So soon I should be up and running. I have the gas bottle now and a new gauge and supply tube arriving soon so I can then give it a run.
I have 2 questions please.

1 - What pressure should I set the gauge to when welding? This is the tube with the floating ball in it.

2 - Why did I have to reverse the polarity on the work lead and earth? Gasless works on + earth and gas works on - earth.

Incase it makes a difference to your replies I am going to be using 0.9mm wire.
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Old 12-06-2017, 07:52:28 AM
oldgoat oldgoat is offline
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Default Re: MIG Welding

The tube with the ball is usually calibrated in litres/min I used to set mine between 6 and 8 except on a windy day when I just gave up. Dont know the scientific reason why it has to be reversed but try it without and you will see why.
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Old 12-06-2017, 10:18:21 AM
Ray Freeman Ray Freeman is offline
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Default Re: MIG Welding

Inner shield (self shielding) always runs wire negative. Outer shield (fluxcore with gas ) and hardwire run wire positive. I run my gas at 15 litres a minute and up to 20 if its a bit breezy. Nothing wrong with running it less if you don't get porosity.
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Old 12-06-2017, 11:12:54 AM
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Default Re: MIG Welding

With the floating ball you are running a flow metering system as opposed to setting to a "pressure" I have always preferred flow metering. Set it as low as you can to maintain a clean pass, dial it up a bit if you are dealing with wind. Mine normally floats at about 1/4 to 1/3 of the gauge height. Diameter of your gas nozzle will affect your results somewhat.

You should be much happier with the results from gas shield. Much cleaner job.
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Old 12-06-2017, 06:27:45 PM
sunshineman sunshineman is offline
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Default Re: MIG Welding

Hi cobba
As already stated run your flow rate so you get clean bubble free welds .experiment on scrap start 4 litres min and work up .
Polarity change -heat transfers in a different direction I believe, eg I think the flux cored is hot .
Regards sunshineman
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Old 12-06-2017, 11:34:28 PM
cobbadog cobbadog is offline
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Default Re: MIG Welding

Thank you to all who replied, I have taken it on board so I am now waiting for the gauge and hose to arrive and away I go.

When I was altering the polarity I have to read the translated Chinese to Australian wording a few times to understand what they were saying but I got it sorted to set up gasless so I simply reversed the set up.
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Old 12-08-2017, 01:55:55 AM
cobbadog cobbadog is offline
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Default Re: MIG Welding

Hi again guys,
Been waiting for the post to arrive at the post office and unfortunately I missed out on getting the gauge in time for the weekend. So that should be here Monday now, I also have been watching YouTube clips to get more tips on using the gas set up ad something popped up that made me think about the settings on the mig set up with gas.

My loosely translated booklet claims that I should use negative earth for welding with gas. Does this sound right to you?

The clip I was watching was a young bloke from the States for clearly stated to set it to positive earth when welding with gas.
So what is the general view here please?

Cheers cobba
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Old 12-08-2017, 06:44:13 AM
Ray Freeman Ray Freeman is offline
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Default Re: MIG Welding

Its not the gas that determines polarity. Its the wire. Solid wire is electrode/wire positive.
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Old 12-09-2017, 12:40:33 PM
dkamp dkamp is offline
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Default Re: MIG Welding

Hey Cobba!

The reason why polarity is reversed:

Because of the presence of flux core, wire has less material in it, so it responds to welding current differently from solid-core.

When welding, polarity affects where the heat is focused- electrons moving from one side of the arc to the other makes one side of the arc slightly hotter than the other.

When using flux core, heat is directed more toward the bead, which causes the flux to gasify AT the bead, promoting gas shielding and flux dispersal over the top of the weld.

When using solid wire with shielding gas, shielding starts at the nozzle, and FLOWS over the arc and bead. The wire requires a little more heat, but as a side effect, wire speed can go much higher, resulting it better welding performance.

SO... you can run it with polarity backwards for the application, and it WILL weld, but it performs much better if you set it properly.

If you're experiencing windy conditions and REALLY need to get a bead down, use shielding gas, but with flux-core wire and polarity. Yeah, you'll have to chip off the flux, but it'll get it done well.
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Old 12-09-2017, 08:49:33 PM
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Default Re: MIG Welding

Since I prefer to do my welding outside, I run fluxcore, exclusively. I've dabbled with running positive electrode and the beads were pretty crappy. MUCH better running positive earth.
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Old 12-10-2017, 12:23:16 AM
Ray Freeman Ray Freeman is offline
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Default Re: MIG Welding

People probably need to specify exactly what type of wire they are running. There are two main types of fluxcore. One runs with gas and welds wire positive. The other is inner shield which normally runs with no gas and is self shielding.It runs wire negative.
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Old 12-12-2017, 01:11:39 AM
cobbadog cobbadog is offline
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Default Re: MIG Welding

Thanks Ray and I agree with your comment except the polarity going by my booklet. At this stage I will own up to knowing 3/5 of stuff all in this area and is why I am asking all the silly questions but my booklet claims welding with flux core wire it is positive earth. Welding with gas it is negative earth.
I also just printed off a sheet for Volts to metres/minute as a guide to set up welder. It also claims to set it up as my booklet says. I am not trying to be a smart ass but I can only read or listen to what I see and hear.
So I am a bit confused which is the correct way.
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Old 12-14-2017, 01:30:22 AM
Ray Freeman Ray Freeman is offline
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Default Re: MIG Welding

Quote:
Originally Posted by cobbadog View Post
but my booklet claims welding with flux core wire it is positive earth. Welding with gas it is negative earth.

So I am a bit confused which is the correct way.
And they are correct but what they will be referring to is flux core INNER SHIELD gasless wire.
I'm presuming your welder is a smaller unit? The outer shield gas wires are usually used in industrial size welders. The flux core outer shield wires that I run usually run at 350 amps or so. The inner shields gasless wires in 1.2 diameter I run at 160 amps (3.5 mts/min) and around 17 volts.
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Old 12-15-2017, 01:41:35 AM
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Default Re: MIG Welding

Yes Ray, it is a small hobby welder. My fault for not mentioning that.
Anyway, since connecting the gas, changing the polarity and wire I now am getting good results for a beginner. So more practice with various thickness metals and voltage and wire feed and I will improve over time. I tend to write down what works with the settings on different thickness metals. NExt step is to buy some 0.8mm wire to use on lighter metals like the tin ware on the tractor. Currently, no pun intended, I am using 0.9mm wire on the heavier steel like 3mm thick.

I would like to thanks everyone here for their helpful tips, I appreciate it very much,
Cheers Cobba
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Old 12-22-2017, 02:37:10 AM
cobbadog cobbadog is offline
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Default Re: MIG Welding

Here is a sample of my first attempts. Some were vertical up on a diagonal and the fillet is down hand. I am happy with the result and it has already improved somewhat.
Don't know why I waited so long to go to gas.
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  #16  
Old 12-22-2017, 07:16:57 AM
I like oldstuff I like oldstuff is offline
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Default Re: MIG Welding

I was taught by a pro welder that is certified to work in nuke power plants so I trust that's a good thing!

MIG is a production tool and as you have found out doesn't penetrate well. It is good at filling gaps so the melt puddle can fill the gap for a good root strength.

As it doesn't have much 'power' compared to stick welding it needs all the help it can get. It often won't cut through the mill scale or rust on the metal so a weld zone that has been cleaned off with an angle grinder goes a long way to making a good joint.

Today there are a lot of good you tube videos that serve well to teach technique and how to set up the machine. On a lot of machines the settings are printed on the inside of the side cover. For example, a good starting point for .9mm wire is 19V and 127cm feed rate. As taught, you want to hear it welding with the sound of eggs frying in a hot pan. Have a mate vary the volts and feed as you weld. When it's a perfect weld you'll then know the sweet spot for your machine.

Last edited by I like oldstuff; 12-22-2017 at 07:27:24 AM.
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