MIG Welding questions

Drunkskunk

100 GW
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Apr 14, 2007
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Dallas, Texas. U.S.A.
I have a few dumb@ss questions for those who weld MIG. :D

I'm setting my Welder up for MIG for the first time. Its only been used for Flux core up untill now, and I have almost no experience with MIG. Also I lost the instructions in a flood 7 years ago, and the online instructions from Hobart are only for the newer revisions. Not sure how much applies to what I have. If it helps, this is a 120V Hobart Handler 140.

Whats the right pressure for the Argon tank? I bought a new tank with the welder, and even welded up a cart to hold both, but that was 14 years ago. I never hooked up the valve until now. No clue if it's still full or leaked down. It shows 800lbs

Whats the right flow rate for the gas when welding?

Any tips for practicing welds with MIG? I played with it a little, seems to make cleaner welds but getting good penetration seems harder than Flux-core.
 
Our tank has a pressure gauge on the output and we only ever adjust it between 5 and 10psi. Not a guru, but this has worked really well for us.

I couldn't get flux core to do anything useful - tape works better. :lol:
 
Disconect the wire feed so you can place your hand infront of the torch shroud and pull the trigger, set the gas flow so that you can just feel a slight draught on your hand and hear the gas coming out, this will be fine for welding indoors, outdoors will require more due to it being blown away by the wind. Always lead when using mig, point the torch straight at the joint at an equal angle to each of the faces to be welded if they are of equal thickness (bias the torch towards the thicker material if they are different) then lean it back about 10 deg and weld in the direction the torch is pointing with exception of welding vertically down when you would point the torch upwards but move downwards, on thin material anyway.
The actual output pressure setting on your regulator will be dependant on how restrictive the gases passage from the bottle to the torch is so it is best set by feel at the shroud, if you only have a single stage reg the output flow will increase as the bottle pressure goes down, if the reg is getting wet with condensation on the outside you are flowing too much gas.

play with the power and wire feed to find the best setting for the job you are doing on a similar thickness scrap peice, with experience you will be able to set it just about right straight away.
A 140a machine should be quite capable to weld steel upto 4mm thick, much thicker and the heat wont be high enough to cope with the amount being dissipated in the material resulting in poor welds.

That should get you going, now lots of practice!


Cheers Simon.
 
Thanks for the advice, it got me started, and I've been practicing.

But I'm finding MIG just doesn't have the penetrating power of Fluxcore. I'm practicing on .065" barstock Chrome-moly and I can make some great looking welds that seem to flow well into the base metal, but looking at the back side of the joint, I don't seem to get much penitration even on the highest amp settings.

Am I doing it wrong? Or is MIG just less able to penitrate?
 
The lack of penetration may be the gas. Argon is more for Ali and other non ferrous metals. I once used some argon left over from an Ali job and it was not good for steel welds. Migshield is the common gas used here and is a blend of carbon dioxide (around 20%) and argon. Sometimes there are other gases like oxygen added in.
 
Drunkskunk said:
Thanks for the advice, it got me started, and I've been practicing.

But I'm finding MIG just doesn't have the penetrating power of Fluxcore. I'm practicing on .065" barstock Chrome-moly and I can make some great looking welds that seem to flow well into the base metal, but looking at the back side of the joint, I don't seem to get much penitration even on the highest amp settings.

Am I doing it wrong? Or is MIG just less able to penitrate?

I use straight argon for Al or Steel to 3/4" thick, BUT here is some good info.
http://en.wikipedia.org/wiki/Gas_metal_arc_welding

My buddy has 42 welding tickets and is paid $1000 a day, so he must be good at what he does. He uses straight Argon to TIG (NOT MIG) SS pressure vessels up to 2" thick. After reading the Wiki info on argon/carbon dioxide mix of 90:10 to 75:25, I phoned him to check AGAIN, because I asked him about C02 when he set my system up. 100% Argon does not penetrate as well as the GMAW, but you just turn the heat up a little with MIG or TIG.
I know nothing about the theory of welding, I've just done it all my life until something fails and then go find a guy who knows why. The main reason I have stuck with straight argon is to not have the cost of a 3rd bottle. With O2/propane for cutting and brazing plus the argon, I pay already pay $200 a year for bottle rent, plus the gas used. Enough for a hobby-shop.
 
I'm going to give away my mig gas bottle soon. $200 per bottle just for rent and over $100 for a D size fill, which is not a big tank. We get screwed for this sort of stuff.

I'll keep the O2 for the red'n'black spanners tho.... I use an LPG tank with the oxygen and it is almost as good as Acetylene.
 
andynogo said:
I'm going to give away my mig gas bottle soon. $200 per bottle just for rent and over $100 for a D size fill, which is not a big tank. We get screwed for this sort of stuff.

I'll keep the O2 for the red'n'black spanners tho.... I use an LPG tank with the oxygen and it is almost as good as Acetylene.

Hi Andy,
I am always puzzled about the "almost as good as". I happened to see guys cutting up old steam locomotives when I was a teenager in the 1960's. 8" thick steel. That is when I bought my first propane cutting setup. Much later, contrary to all current wisdom, I found you can braze very well with it. Where does it come up short?
 
Drunkskunk said:
So CO2 makes it penetrate better? I've got 100% Argon, but from my Beer keggging days I've got a 20LBS bottle of CO2.. I wonder what a valve body for blending them would cost?


Gordo, I'm curious why your friend uses 100%? I was told to go with 100% when I started, but no idea why.
Don't know, but I will certainly ask. He is one very studious welder. If he is off work for a month, he puts a full week in the booth at the college before doing pressure vessels. One failure can ruin his career and some lives, if the x-ray misses a void. He is the guy they call when the other guys welds fail. He is always after me to go audit some TIG coarse at the College. Probably to get away from my questions. :mrgreen:

CO2
Simple setup. 2 demand regulators with flow meters and a "T" Set the CO2 for 15% of the argon FLOW and fiddle from there. Assuming you have 1000psi of CO2? Look for rebuilt regulators from a service shop. We have a local lady who is a wiz at rebuilds.
 
Gordo said:
andynogo said:
I'm going to give away my mig gas bottle soon. $200 per bottle just for rent and over $100 for a D size fill, which is not a big tank. We get screwed for this sort of stuff.

I'll keep the O2 for the red'n'black spanners tho.... I use an LPG tank with the oxygen and it is almost as good as Acetylene.

Hi Andy,
I am always puzzled about the "almost as good as". I happened to see guys cutting up old steam locomotives when I was a teenager in the 1960's. 8" thick steel. That is when I bought my first propane cutting setup. Much later, contrary to all current wisdom, I found you can braze very well with it. Where does it come up short?

Oxy propane (near enough to lpg) burns at 2500 celcius. Oxy acetylene burns at 3500 celcius. Some jobs- big cutting jobs for example- need the extra heat. For most of us hobbyists, 2500 celcius is plenty! Not to mention the cost savings- $0 for bottle rental and $25 for a 9kg refill. Just makes sense. Shame I can't source O2 cheap as well!
 
I always thought that CO2 produces a colder weld than an argon/co2 mix, specific mig welding gas is a mixture of the 2.

http://www.mig-welding.co.uk/welding-gas.htm
 
When I was welding at work, I only had 8 certs. but those were rated as to be able to weld on a atomic sub, not pressure vessels. or pipes. I thought that I forget how to weld SS when the gas supplyer dropped off a new 330cufoot tank where the tank was filled without purging, vacuuming, out the ambent air before filling with argon, used with TIG. The right gas mixture can be important.
 
Getting off topic.
Steel burns at 1500C. Once it begins to burn, you can shut the other gas off altogether. All the acetylene does over propane is get the steel up to burning temperature quicker. I've never cut anything thicker than 2" so I have never been concerned with speed. Once you get the corner burning, you are away.

I always thought a submarine was a pressure vessel, requiring a pressure ticket? :mrgreen:
 
Drunkskunk said:
Any tips for practicing welds with MIG? I played with it a little, seems to make cleaner welds but getting good penetration seems harder than Flux-core.

Hey Drunkskunk,

I'm a welder/fabricator for a living and might be able to help a little :?:

I assume your pushing the weld (correct way with GMAW) rather than pulling it as you would with flux :?: That will make a difference to the peno you will get.
Clean the surface well and make sure your arc length is no more than about 10mm (tip to steel).

You could also try turning your wire speed down a bit and slowing down the weld to build up the heat a bit more. 8)

Of course this could all be irrelevant having not actually seen you weld :D
 
Drunkskunk said:
I have a few dumb@ss questions for those who weld MIG. :D

I'm setting my Welder up for MIG for the first time. Its only been used for Flux core up untill now, and I have almost no experience with MIG. Also I lost the instructions in a flood 7 years ago, and the online instructions from Hobart are only for the newer revisions. Not sure how much applies to what I have. If it helps, this is a 120V Hobart Handler 140.

Whats the right pressure for the Argon tank? I bought a new tank with the welder, and even welded up a cart to hold both, but that was 14 years ago. I never hooked up the valve until now. No clue if it's still full or leaked down. It shows 800lbs

Whats the right flow rate for the gas when welding?

Any tips for practicing welds with MIG? I played with it a little, seems to make cleaner welds but getting good penetration seems harder than Flux-core.

Note you change the polarity when you switch from Flux to GMAW;

This video might be helpful?
http://www.weldingtipsandtricks.com/how-to-mig-weld.html
 
Drunkskunk said:
So CO2 makes it penetrate better? I've got 100% Argon, but from my Beer keggging days I've got a 20LBS bottle of CO2.. I wonder what a valve body for blending them would cost?


Gordo, I'm curious why your friend uses 100%? I was told to go with 100% when I started, but no idea why.

I checked and he does use 100% argon for MIG or TIG in their shop. Steel or SS. He has no idea why anyone would claim lack of penetration. He repeated that he welds pipe and pressure vessels, from 5/8" to 2" thick.
 
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i'm now getting half-decent results w/ flux-core wire but i wanna try MIG. is it that much better?

specifically i'm getting tired of the cleanup needed w/ flux-core. and the smoke :flame:
 
Novice MIG welder here (hobby only) but I've been doing my own automotive body work repairs for a few years now. I mostly have been welding on crappy (very thin and corroded) sheet metal (20 GA to 24 GA). The switch to shielding gas from flux core was well worth it for me; it gave me more control and confidence. My welds with flux core were burning through say 70-80% of the time; switching to MIG instantly reduced it to around 30-40% burn through. After about 40-60 more hours experience I've got my sheet metal tac welds only burning through about 10% of the time with MIG.

I imagine the difference would be a bit less dramatic if you are are more experienced welder; also with thicker gauge steel; you wound't run into the same issues I had. Just make sure you select the correct size welding wire and right mix of gas for the job. My little welder came with all the gas fittings so I just had to buy a cylinder of "autoweld" shielding gas and solid core wire; total cost was around $100 CAD.
 
You still have to clean everything well.....if any smoke, contaminates or oxygen get in your shielding gas it will make your welds porous. Sheilding gas keeps oxygen out to control the weld burn.....add oxygen and just like a cutting torch it will blow holes in it.

Biggest mistake most do going from flux core to mig is forgetting (or not knowing!) to switch the polarity on the ground/wire.

Tom
 
so a few months back i went ahead and got a 20lb tank of co2 and regulator. didn't cost much. in retrospect MIG is actually "cheaper" than flux-core since good fluxcore wire is expensive and not copper coated so it rusts, you can't keep it for a long time :evil:

just as the OP said MIG does have a "soft" arc that doesn't penetrate as well as fluxcore which is both good and bad. good for thin material, less likely to blow through. bad for thick material if your machine doesn't have a lot of amps (i'm using a relatively weak Cigweld 135)

fluxcore still great to use outdoors on a windy day. and you can remove your gas nozzle for welding in tight spaces. each process has its own pros and cons.

PS if you're going to MIG mostly thin material get 0.6mm wire (0.023")
 
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