General welding information

Discussion in '<a href=http://www.lawnsite.com/buttons/jump.php?i' started by Lance Takara, Apr 23, 2002.

  1. Lance Takara

    Lance Takara LawnSite Member
    Posts: 73

    I've welded with arc and am currently using a miller 250 MIG welder for all around welding - thick and thin. My welding is more than satisfactory, however, I don't quite understand the strengths of the different types of welders.

    Basic question here. May sound stupid but here goes.
    Is the strength of a MIG welder for thin material? While the strength of an arc welder for thick material? Or are there other reasons? If that is true, where is the transition from thin to thick metal? Also, does that mean a good setup would be 2 welders, a line voltage MIG and a 220v arc to cover thin to thick material?

    I have searched, but seems all previous discussions have skirted this direct question.

    Thanks in advance for all replies
     
  2. chip hayden

    chip hayden LawnSite Member
    Posts: 29

    I'll give it a try to answer your questions. Realistically, it's a matter of available equipment and what people feel the most comfortable with if they use gmaw[mig] or smaw[stick]. Personally, i use gmaw as much as possible. it's faster, deposition rate is greater, and less clean-up afterwards.
    Strength-wise, all gmaw wire has a tensile of 70,000psi or greater[ER70s-6]. smaw electrode[stick] have a 60,000 tensile or greater.Be careful if you opt for low hydrogen coated electrodes[i.e.7018]. if they aren't kept at 240F. after the seal is broken on the package hydrogen will be absorbed by the flux coating and get trapped in the weldment. this is very serious.
    One of the few times i will use smaw over gmaw is when it's a field weld and i can't maintain the gas shield around my weld pool. this happens at about 10 mph breeze.
    one of the most common mistakes i see with gmaw is a cold lap weld. most everone who has a cv machine[wire-feeder] welds in the short circuit mode. it sounds like bacon frying. the welding wire melts easily because of the diameter being so small but incomplete fusion occurs with the base metal. it can look like a great weld to the untrained eye but when it is under tension it will fail. it's almost impossible to get a good looking cold lap in smaw[stick].
    If you have a 250 amp Miller mig machine i would suggest using that as much as possible. use a 75-25 ar/co2 mix with er70s-6 .035 dia.. this will cover any mild steel application from about .062 thick steel to over .500 thick. any thing over .250 thick i try to weld in the spray mode. This will be in the upper range of the power supply. the wire speed will be near the top also. the machine will sound completely different. kind of a whooshing noise as the filler metal is "atomized" as it comes out of the contact tip. once you become proficient in the spray mode nothing will hold you back. have fun!
     
  3. Lance Takara

    Lance Takara LawnSite Member
    Posts: 73

    Chip, thanks for the response but please excuse the ignorance on my part . . . .


    mig welder

    I've been using flux cored wire thus I end up having to chip my welds afterwards

    Are flux cored wire welds on the mig machine comparable to arc welds? If so, wouldn't using the flux cored wire solve the problem of using a shielding gas when faced with windy field conditions?

    On the other hand, the shielding gas prevents the slag formation. Correct? No chipping? Does the shielding gas also make for a better weld?

    Cold lap

    If i'ts common for c-v mig welders to produce cold laps (and incomplete fusion with the base metal) while your "spray mode" does not, what is the reason for not using the "spray mode" for metal under 1/4" thick? Is it to prevent burnthrough?
     
  4. chip hayden

    chip hayden LawnSite Member
    Posts: 29

    those are good questions and i'll try my best to answer them.
    1.fcaw[flux cored] also has a tensile strength of 70,000psi and the process is less susceptible to windy conditions. i would say it's no better or worse than smaw[stick]. maybe just easier?
    2. yes. with solid core wire there is no slag so less post-weld cleanup. my preference in order is as follows;
    A.solid core .023-.062 dia., -6 for additional cleaning action with a 75-25 ar/co2 shielding gas.
    B.metal cored .045 and up dia., M6 for manual operation with same shielding gas mix. this is for heavy sections .750 and thicker and long welds like wrapping a bucket. if you still have the original miller gun i wouldn't run metal cored for long. the heat generated by this wire will fry that little gun. my preference is a bernard gun.
    C.dual shield wire for dirty, scaly steel. same gas.
    D.gasless flux cored when i can't pay my gas bill.
    3.Yes. the high arc voltage and amperage makes it difficult to weld thin sections in the spray mode without burnthru. this is addressed with new technology power supplies[ inverters and pulsers].
    hope this helps. best regards, chip.
     
  5. 75

    75 LawnSite Senior Member
    Posts: 992

    Going by my own experience at work and the home shop, I like MIG for light material simply because with small wire and the heat/wire speed turned down, sheet metal work is a breeze. I have a Lincoln SP100 at home (110V MIG) that I use .023 solid wire and Co2 gas with for bodywork.

    Regarding the fluxcore/stick comparison (FCAW/SMAW) fluxcore is comparable as far as finished weld goes, fluxcore's advantage is the higher deposition rate. Not having to stop and put in new sticks makes a big difference, plus on larger welds you can "turn up the heat and go".

    Depending on where you have to reach, stick is still common for field work - it's what I use the majority of the time.

    I tend to consider anything under 1/8" to be "light" or "sheet" metal, and will either use the MIG or small (3/32" or even 1/16") rod if I have to use the stick machine on it.
     
  6. Lance Takara

    Lance Takara LawnSite Member
    Posts: 73

    Chip & Rob, thanks for your time in sharing information. Hope there are more guys like you on the list.
     

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