MIG, Flux-Core, Dual Shield question

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On another forum, a long-time welder suggested using C02 gas with regular flux core wire as a way to keep the tip cooler and produce a better weld on mild steel than you would with solid wire and C25.  I was under the impression that the flux core wires intended for dual shield welding were not the same as the ones for ordinary flux core welding.  Am I right about this?I've also never heard of a need to keep the tip cool -- I wasn't aware that shielding gas had any function other than displacing the oxygen-laced air with a neutral gas to improve the quality of the weld.  Does shielding gas play a role in cooling anything?Thanks for any input.Jack OlsenMy garage website
Reply:The gas or no gas with gasless flux core has been discussed over and over. If someone wants to run gas then why not run dual shield.I guess theoretically any gas moving over the weld tip would help draw some heat away. I can't imagine it making even a slight difference let alone one worth considering. But hey I have been wrong before and I will be wrong again.Ken
Reply:Jack,self-shielded fluxcore(FCAW-S) is not meant to be used with shielding gas.period.gas-shielded fluxcore(FCAW-G)  and metal cored wires(MCAW) are only to be used with shielding gas. period.  Which shielding gas varies from product to product.  Some FCAW-G and MCAW wires can be used with more than one type of gas or gas mixture.  Others are designed only to work with 1 specific type of gas or gas mixture.  You have to consult the manufacturer's technical data sheets and comply with their recommendations.Shielding gases, particularly those with large CO2 content or 100% CO2 play a role in the weld deposit chemistry.  The Europeans refer to welding with CO2 as MAG, not MIG.  The A in MAG stands for active, to reflect the fact that CO2 alters the weld deposit chemistry to a much greater extent than Ar or He.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:I know a welding instructor that swears using 100% CO2 with self shielding flux core (NR 211 MP I think) does wonders to make the weld better...better penetration and better look.  I was surprised, but his assessment is it makes self shielding flux core look less like welding with a 6010 rod and approaches the look of a 7018.  That said, dual shield flux core is about like 7018 on a roll, at least to my eye.   I have yet to bend test a dual shield weld, but on heavy plate, it seems to penetrate really well! He's using self shielding flux core in a Lincoln 135  or 140 (I think).  At least it's a 120V Mig.  I have not tried 100% CO2, and personally keep self shielded wire on hand to use when I have to weld outside and cannot use a shielding gas.  If I can bring it into the garage, I'll use solid wire or dual shield, depending on application.Just my .02...YMMV!Tracker401
Reply:It would be nice , if all would learn to use the correct terminology and it would be easier to answer some of these questions.  More if all want to know.  JGSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Dual shield is like a metal caulk gun; absolutely awesome when you really need to lay down some metal.
Reply:Hello Jack, when you are discussing flux-cored arc welding you can be speaking of basically the gas shielded variety(dual shield) and the self-shielded type. Self-shielded flux-core wires should never be used with a shielding gas, the components that make up the flux core are designed to provide all of the necessary deoxidizers/puddle formers/gaseous shielding cloud/alloying agents that need to be there. You will run the risk of not allowing these agents to work properly by using an external shielding gas which could also cause a hard, crack prone deposit or other detrimental issues with the weld.      Gas-shielded flux core wires need to be shielded with the correct type of gas because they are engineered with a specific gas in mind. Some of these wires will specify a specific gas, others will possibly state a maximum of argon percentage to be used. Even in this situation, using an improper or unapproved shielding gas can cause metallurgical issues with the completed weld deposit. The AWS wire designation on a particular wire will spell out which gas or gases are approved for use.      Another poster had included a statement about reactive gas, CO2 is indeed considered a reactive gas and is used to promote penetration in many applications by either exclusive use or mixed with Argon or other shielding gases. CO2 also has some very unique properties, when it is used in the short-circuiting transfer mode with solid wire it can somewhat help to "cool" the puddle and prevent excessive burn through(light gauge sheetmetal or autobody use). On the other end of the spectrum, if it is used in the globular transfer mode(cannot achieve true spray transfer at high voltage/current levels) it will provide deeper penetration than most other shielding gases. Main thing here is to consider that operator appeal and weld deposit aestetics are terrible for straight CO2, solid wire welding at high voltage/current levels. My $.02 for your consideration on this topic. Best regards, Allanaevald
Reply:Dual Shield was a trade name of Alloy Rods (Atom Arc) and not a process name and should be treated as such.  JGSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Hello weldgault, for the purist out there, you are absolutely correct. In a similar fashion, innershield was a lincoln trade name for self-shielded wire, Heli- arc was a trade derivitive of Union Carbide to describe the GTAW process and there are certainly others that could be more "correctly" described. Have a great day and best regards, Allanaevald
Reply:Use the right shielding gas, or no gas, as specified by the wire maker.Otherwise you are changing the chemistry of the actual weld.FCAW-S = self-shielding fluxcore wire, use NO shielding gasFCAW-G = use the specified shielding gas(es)solid wire = use the specified shielding gas(es)Use the 'correct' materials and the 'correct' process parameters in order to achieve known results.Jack, yes the flow of the shielding gas does have an effect on cooling the torch/gun a bit.  But for high-amp processes, you still might have to use a water-cooled gun.  The best laid schemes ... Gang oft agley ...
Reply:Amen to water cooled.  JGSMAW,GMAW,FCAW,GTAW,SAW,PAC/PAW/OFCand Shielding Gases.  There all here. :
Reply:Shielding gas definitely has an effect on cooling the mig gun.  If you check it out, most guns are rated based on using CO2.  Using C25 or some other mix, generally results in a lowered duty cycle.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.