Flux polarity question

admin

I don't use flux in a mig but a buddy of mine wants to know what is it about flux that it has to run negative polarity?We couldn't really couldn't find a good answer on the web. I thought I'd toss it out to you guys. ThanksRegards,RobGreat Basin WeldingInstagramBlue weldersRed weldersMy luscious Table DIY TIG Torch cooler
Reply:Where did he come up with that. I've never heard of it, yet. Will be interesting to learn more.Sent from my iPhone using Tapatalk
Reply:It may have been I took his word for it. I could be completely off base. As I said I don't use it.  Do I have the idea of polarity wrong on it?Regards,RobGreat Basin WeldingInstagramBlue weldersRed weldersMy luscious Table DIY TIG Torch cooler
Reply:I honestly don't know. I've been in shops and know probably 25 professional welders of different areas of expertise and I've not heard of it yet. Let's wait and see.Sent from my iPhone using Tapatalk
Reply:The more common off the shelf at the big box store self shielding flux cores run DCENhttp://www.esabna.com/EUWeb/AWTC/Lesson7_15.htm"The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:While there are exceptions, most self-shielding flux-core wires are DCEN. Most, if not all, gas-shielded wires are DCEP. I have read quite a lot on the subject, but I'm still not sure of the reasons why.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:If its self shielding wire like Innershield 211 which is what I run in my Lincoln Pro-Core 125 then the polarity is DC electrode negative. I think what your asking is why does flux core need DCEN polarity and my guess to that may be the flux and the way the electrons that flow through it may affect the weld,now keep in mine i'm not a professional in the wires chemistry I just happen to burn a lot of wire Lincoln pro core 125 14''chop saw7 inch grinder,2-4.5 inch grinders,electric die grinder.Half inch drillAnd alot of hand tools
Reply:Not a solid state Chemist, but a few comments.All FCAW-S electrodes are not created equal.  Assuming FCAW-S is DCEN is incorrect (Ref, Table 3.1, p.5., www.jflf.org/pdfs/papers/fabguide.pdf).  There are many exceptions that result in DCEP for self-shielded, flux-cored wires. Insight into slag chemistry, courtesy Lincoln Electric,"The slag systems in self-shielded flux cored arc welding are unique. They predominantly use an aluminum-magnesium deoxidizing and de-nitriding system. These elements enter the weld pool and form aluminum oxide and magnesium oxide, two compounds with high melting temperatures. Combine these with low-melting-temperature elements in the flux, and you get an effective slag system. The slag elements–aluminum oxide and magnesium oxide–melt first and float to the top of the molten weld pool, protecting the process from atmospheric contamination.FCAW-S has a very high tolerance for nitrogen, and the slag systems make this possible. The aluminum and magnesium molecules attract oxygen and nitrogen atoms, which connect to form those aluminum and magnesium oxides. These high-melting-point (that is, fast-freezing), lightweight compounds float to the weld surface quickly. In effect, the slag system transforms oxygen and nitrogen–potential contaminants–into chemical compounds that protect the weld.Many FCAW-S wires use one of two types of slag systems: basic and acidic. In basic systems, calcium fluoride works together with the aluminum and magnesium compounds, creating a system that somewhat resembles the slag produced when welding with some SMAW electrodes, such as E7018. Acidic systems, on the other hand, use iron oxide instead of calcium fluoride.The basic systems have good cleaning action and tend to be suited for structural-critical work, meeting low-temperature toughness and other stringent mechanical-property requirements. Acidic systems promote smooth, fast welding. The reason behind this has a lot to do with how the acidic and basic elements react with other weld metal elements. It comes down to how easily chemical reactions occur. During welding, molecules are ionized, meaning atoms leave certain molecules to join others, and specific slag systems require different levels of heat to accomplish this. In fluoride systems, a lot of heat goes into breaking up these molecules to form fluoride bonds. Meanwhile, it doesn’t take quite as much heat to break up the acidic, iron-oxide molecules. The quick reaction leads to fast slag-freezing and, ultimately, high deposition rates." - (Ref, http://www.lincolnelectric.com/en-us...ws-basics.aspx)Thinking that optimizing the direction of electron (--->) and ion (<---) flow into/from the parent materials is the black magic.To the curious, recommend devouring anything written by Blodgett and Miller (of Lincoln).Last edited by ManoKai; 01-18-2014 at 08:58 AM."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:My thoughts on the OP's question are based on the eloquent information posted by ManoKai.I was told way back in time that DCEP (reverse polarity) will provide for the greater amount of arc heat to occur at the surface of the base metal being welded on.  By the same rationale, when welding DCEN (straight polarity), the greater amount of arc heat occurs at the ELECTRODE side of the arc.  In seeing that some of the chemical processes needed for best performance with certain flux makeups, I would say that the ones requiring the higher heat (for the specific chemical reactions) would be specified to run on DCEN.Those are my interpretations of the data provided.
Reply:Walkerweld, you are on the right track. When using a gasless flux, which means a shielding gas is not required, the additional heat is required in the puddle, using DCEN, it helps the flux with its specific chemistry, to help burn, to produce its own shielding gas. Just the non-in depth detail.