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  1. #1
    Join Date
    Sep 2007
    Posts
    13

    Default Questions about Mig welding metal thickness?

    I am thinking of buying a Millermatic 252 that is rated at up to one half inch thick welding with one pass. I have some questions.

    1. On the small 120 volt mig machines they say that you can weld thicker metal with flux cored wire then gas shielded welding. Is that true of the bigger welders such as the Millermatic 252 as well?

    2. Let's say that I want to make a outside corner weld putting two pieces of half inch flat steel together edge to edge so that I have a large fillet weld. Would the Millermatic 252 to up the the task? If I were to weld a half inch fillet weld with stick I would use more than one pass.

    3. I am going to be repairing some 3/4 inch brackets from a farm disc. The brackets are made of 6"flat steel 3/4 inch thick. I need to add about 2 inches to the brackets. If I bevel a butt joint halfway through from either side for full penetration would the MM252 be up to the task? Normally I would weld something like that with 7018 stick rod.

    Thanks, Rick

  2. #2
    Join Date
    Jan 2007
    Location
    Alberta Red Deer
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    373

    Default

    first of all being a experienced welder u maybe able to weld 1/2" in one pass but i would ever ever do this. groove it out then filler back up, this is the correct way. your second question do the same as u would for stick. your question about the farm discs the 252 is up for the task, just do what u said groove it out then weld it up. i have welded much thicker with my 252 with out problem, you just have to make a few passes.
    trail blazer 302
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  3. #3
    Join Date
    Dec 2007
    Location
    alabama
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    745

    Default

    a little pre-heat will be beneficial on the heavy stuff.
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  4. #4
    Join Date
    Dec 2007
    Location
    southern California
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    1,783

    Default

    The 200-amp and up machines have the power to weld a joint that thick in one pass, But... the puddle from a 1/2" weld in one pass is alot of liquid metal to keep under control at one time.

    It can be done with MIG in the flat position with full penetration in a groove-prepped butt joint or outside corner turned on it's side facing up (I don't know the proper name for that). Although I have done that before, I normally use more than one pass to weld anything thicker than about 5/16, it's alot easier for me to control the weld.

    Fillets and laps much thicker than 1/4" in one pass, for me anyways, usually result in undercut of the top plate and convexity at the toe of the bottom one, so I use multiple passes instead. Possibly I'm moving too slow, weaving it wrong, or don't have enough wire going into it. As for out of position that thick in one pass? I don't even attempt it.

    Maybe with alot more practice I could get it down, but I just don't have much need to weld stuff that heavy. Most of my welding is done in the 1/16 to 5/16 range, except for the thin aluminum I weld at work (.040-.080 mostly) and occasional gauge-thick steel at the home shop. Structural steel thicknesses are not my area of experience.
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  5. #5
    Join Date
    Sep 2007
    Posts
    13

    Default

    Great help guys. Thanks. Most of my projects will be less than 1/2 inch but I do have those projects that are of heavy steel. Besides, I would rather have a machine that is more than enough than just barely enough. You can always turn it down if you don't need it but if you do need it it would be nice to have it. One will soon forget the higher price but if you are not happy with your choice you will have to live with it from now on or spend even more money and buy the machine you should have bought in the first place.

    Maybe I missed it but did somebody answer the question about welding thicker metal with flux cored wire than you can with gas shielded wire? Some times I will have to use flux cored wire anyway because I live where it is often breezy. If I am building a trailer that will not fit in the garage then I'll have to use flux cored wire. But still, wire feed even with flux cored wire seems like a much better way to go than the stick after stick after stick way.

    Thanks, Rick

  6. #6
    Join Date
    Nov 2007
    Location
    Southern Louisiana
    Posts
    421

    Default Mm252

    Rick,

    The MillerMatic 252 is rated at 250 amps at 60% duty cycle. meaning that for regular semi-automatic welding it will do fine for what you are talking about, (duty cycle is arc time per 10 minute period. 60%= 6 minutes in 10).

    The flux cored wire you can run is typically one size larger than the solid wire, this will hold true for metalcore wires as well. So what ever your settings for 0.045 solid wire is it is where you should start with 0.052 cored wire. The difference is in the net cross section of the solid part of the wire, effectively they are the same(take the core out of the wire and measure the cross sections). Just make sure you follow the manufacturers recommendations for shielding gas. The shielding gas is critical to arc stability and transfer mode and can make or break a quality weld.

    Remember also that with wire feed welding that energy is much higher than with stick and therefore your arc manipulation is different. If you whip cored wire you are likely to cause entrapments and a weave is likely to cause lack of fusion. For wire feed welding a good straight stringer bead will usually be terrific. The rule of thumb for bead size ranges from 7 to 9 times the diameter of the filler. I have found 7 to be very good but the 9 has followed the stick process and can be ok at times for wire, of course the bead size is regulated by the size of your puddle and therefore to a point your voltage. As any welder is aware you have to keep an eye on the transition point where puddle becomes bead to ensure proper build size.

    To check your energy input use:

    (voltage X amperage X 60) / travel speed = energy input in Joules

    I have found a good range for mild steel generally is to target 16,000 to 20,000 Joules. I have had good results with penetration and distortion. This has been my experience generally of course there are exceptions to any "rule". You should do the testing also to find out for yourself where to be. Obviously the lower the energy input into the material the better to minimize your heat affected zone.

    Material size will also play a big role in what settings to use.

    Take care

  7. #7
    Join Date
    Jan 2008
    Posts
    21

    Default

    [QUOTE=diamondback;110376]Rick,

    The MillerMatic 252 is rated at 250 amps at 60% duty cycle. meaning that for regular semi-automatic welding it will do fine for what you are talking about, (duty cycle is arc time per 10 minute period. 60%= 6 minutes in 10).

    The 252 is rated for 250A @40%, or 200A @60%

  8. #8
    Join Date
    Oct 2006
    Posts
    694

    Default

    Quote Originally Posted by Rik View Post
    I am thinking of buying a Millermatic 252 that is rated at up to one half inch thick welding with one pass.
    Right and wrong... it will weld it in one pass, but it's not going to have much success getting full penetration in one pass...which you won't want anyway.

    When they say it can weld up to 1/2", they're NOT saying it can get full penetration. What they mean is that it will put out enough heat to get a solid bead on material that thick.

    Quote Originally Posted by Rik View Post
    2. Let's say that I want to make a outside corner weld putting two pieces of half inch flat steel together edge to edge so that I have a large fillet weld. Would the Millermatic 252 to up the the task?
    WIthout any problem at all.

    Quote Originally Posted by Rik View Post
    3. I am going to be repairing some 3/4 inch brackets from a farm disc. The brackets are made of 6"flat steel 3/4 inch thick. I need to add about 2 inches to the brackets. If I bevel a butt joint halfway through from either side for full penetration would the MM252 be up to the task?
    Yes, it can do it.

  9. #9
    Join Date
    Nov 2007
    Posts
    184

    Default

    If you can run the beads more or less in the flat position, the machine
    has plenty of zip to go into spray mode. Get a bottle of 90/10 or
    your choice of spray mix and go to it, I think you will still
    like maybe 3 passes though.
    Dave P.

  10. #10
    Join Date
    Sep 2005
    Location
    northern NJ
    Posts
    1,821

    Default

    Look into Lincoln innershield NR-211 (single pass) or NR-212 (multi pass). 045. should run sweet on that machine. A good wire to use without gas. I've also heard good things about the Hobart innershield wires but have not used them personally.
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