wire welder polarity

[reb1]

As I remember, the instructions for my wire welder state one polarity ( I don't remember which) is to be used for flux core wire and the other is specified for use with shielding gas. I use only flux core wire--it's too far to the welding shop for refills of a gas bottle. I haven't tried it yet, but wonder what is wrong with changing polarities?

reb1

[RJohnson]

Flux cored welding wire can be used with either gos or be self-shielding like a stick rod. The wire manufacturer manufactures the wire to a published specification. If you look on the box your wire comes in it will state the specification and the wire classification. For example in our shops we use a wire called Fabco TR70, this is a trade name, the AWS (American Welding Society) classification for this wire is E70T-1 made to AWS/ASME SFA-5.20. This is a CO2 shielded FCAW wire made to run in reverse polority (DCEP). What does this mean to you? Well depending upon which self-shielded wire you are using.
An E70T-3, E70T-4, and E70T-6 are all made to run without an external gas shielding in revierse polarity (DCEP). If you have a E70T-7, E70T-8, E70T-10 or an E70T-11 these are wires which do not require gas shielding either <font color="red"> but </font color> are run in straight polarity (DCEN).
So match your machines polarity to the type of wire you are using. Your welding supply house should be able to give you a product data sheet on your wire and it will tell you the recommended setting for the wire. I hope my long winded explaination did't bore you.
Oh, by the way, as a general rule of thumb the reverse polarity wires (DCEP) give you better penetration and are usually used on thicker material. The straight polarity wires are usually used on thinner materials and do not pentrate as deep. Hope this helps.

Randy

[gauthier]

I agree with every thing mr. johnson said,some f.c.a.w. wires are designed for straight,and some are design for reverse polarity,[- +],and a welding supply place should be able to show you the wire specs showing this.Now m.i.g.ing,you almost always use reverse polarty,I would say always.The theory is to my way of thinking,reverse polarty puts more force or juice than does straight into your puddle,so you get a deeper penatrating weld with d.c.e.p. than with straight,there is a more complicated way of saying this,does electricity flow from positive to negative,or vise versa,who cares,the way I can rember it ,is the way I said above.But in anycase,you run m.i.g. in d.c.e.p. F.C.A.W.,It depends on the wire,whether you need gas as additional shielding and which polarity you use. So,for use without shielding,that run on d.c.e.n.,you got several to choose from,exxt-7,exxt-8,exxt-10 and exxt-11 are some,exxt-11 is considered a general purpose wire,all postion,but the welding supply place SHOULD be at least able to tell you which one he sells the most of for home type use.What would happen if you used d.c.e.p. on the wire designed to be run on d.c.e.n.?I'm not sure,try it if you are that interested,it probably won't do more than make a little mess,I mean it won't blow up your machine. RICHARD GAUTHIER

[Handyman]

Mr Johnson, can you answer this for me..?

What is the advantage of using a gas sheild with a M.I.G. welder over a flux core wire ?

[GaryM]

I'm not Mr. Johnson, but flux cored wire leaves slag to chip off and using a gas shield doesn't.

[reb1]

Thanks, Randy and Richard. You answered the question and some others I had.

reb1

[RJohnson]

The term "MIG" is more appropriately called GMAW (gas metal arc welding), where as FCAW (flux cored arc welding) is closer to a SMAW(shielded metal arc welding), which people refer to as stick, turned inside out. Both FCAW and SMAW welding processes produce slag as a by product of the welding process. I like to think of FCAW as a stick rod turned inside out and this way you can rolled in up in a coil and not break all the slag off. FCAW is replacing SMAW in the work place due to increased efficencies. AND now GMAW is starting to replace FCAW to a large extent due to less fume generation. GMAW is a welding process that requires an external gas shielding because the wire is usually solid and the metalurgy of the wire does not allow for the manufacturer to add alot of fluxing agents that would create slag.
Picking FCAW or GMAW for your primary welding process depends upon many factors, both processes can reguire an external gas shield. Many people like the self-sheilded flux core wires because you do not have to have gas bottles, regulators, hoses, etc. Both processes will require a wire feeder and the appropriate power source.
GMAW does have some limitations for the home user, what you weld on does have to be cleaner. The flux core wire will tolerate more rust, mill scale and other contaminates more than GMAW. (Not that you ought to be welding on rusty steel without cleaning it up [img]/forums/images/icons/tongue.gif[/img] ). But like I said earlier GMAW does not produce the fumes that a FCAW process would, this is becoming an important issue for work place safety of the worker. With some of the new pulsed mig power sources you can reduce your heat input substantiality and this is important where you are welding on thin material and trying to control distortion. Well I see I am getting long winded again [img]/forums/images/icons/blush.gif[/img] , hope this helps.

Randy