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PostPosted: October 27, 2012, 6:31 am 
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Hey guys, I've been given a flux core welder by the guy we just bought a house from. I have zero flux core experience... plenty of standard MIG, but no flux. How much different is it? Heat/speed settings, strength of weld? Haven't had a chance to fire it up in my garage yet; hopefully I'll have time this weekend.

Thanks in advance for advice/info!


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PostPosted: October 27, 2012, 7:21 am 
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Greater penetration apples to apples, since the shielding gas flow cools the welding area. More difficult to see what your doing, but it just takes a little practice. Overlapping passes require chipping the slag off. It is also much messier. Much easier to carry around than with a gas bottle hanging off the end, and small bottle are not very practical since they don't last long and cost abotu the same to refill as a large bottle.

If it is a small job that is easy to access to clean, such as tacking a chassis, flux is fine. For a big job such as final welding a chassis, use gas to save a lot of cleanup.

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PostPosted: October 27, 2012, 7:39 pm 
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Miata..the sheilding gas cools the weld?.. could you please put a link to information on this .


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PostPosted: October 28, 2012, 9:13 am 
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Sorry, no documentation, just my theory, FWIW as to why penetration is not as good with gas blowing on the outside of the puddle, which is documented by Lincoln and experienced by many.

viewtopic.php?f=35&t=3054&p=81763&hilit=penetration+flux#p81763

The linked page has been moved since it has been a few years, but I do not believe they get into the theory about why penetration is not as good.

Obviously, blowing on anything, especially with such a very large temp differential (ambient gas to welding temp) is going to produce a cooling affect. The extent of the cooling affect varies with the type of gas and flow.

I'm talking about basic flux core versus external gas shielded and not addressing the various combinations that are out there for the pros.

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PostPosted: October 28, 2012, 9:58 am 
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Dont forget that gasless flux core wire uses a DC electrode negative as compaired to DC electrode positive in a solid wire Mig weld. DCEN directs more of the arc energy into the work and there for gives better penetration.


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PostPosted: October 28, 2012, 10:30 am 
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I found this:

http://www.esabna.com/EUWeb/AWTC/Lesson2_17.htm

Here (and subsequent pages) they talk about current density and the resultant penetration.

If you keep going on thru the exercise you eventually get to page 28 that says,
Quote:
2.5.1.1 A major drawback of the self shielded process is the metallurgical quality of the deposited weld metal. In addition to gaining its shielding ability from gas forming ingredients in the core, the self shielded electrode contains a high level of deoxidizing and denitrifying alloys, primarily aluminum, in its core. Although the aluminum performs well in neutralizing the affects of oxygen and nitrogen in the arc zone, its presence in the weld metal will reduce ductility and impact strength at low temperatures. For this reason, the self shielding method is usually restricted to less critical applications.


Interesting info.


Most say that flux core gets more penetration "when all other things are equal" due to higher current density. Unfortuantely, comparing .032 fluxcore to .032 solid is not an equal comparison. Compare .030 flux core with .023 solid and you'll get different results. Everything is related to setup and you'll use different setups for these different wires. So "all other things equal" virtually never applies.

for more info comparing solid to fluxcore wires, take a look at the recommended setups here: http://www.airgas.com/documents/pdf/MIGWire.pdf

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PostPosted: October 28, 2012, 11:37 am 
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I didn't forget to switch polarity.

Thanks for the link. We are talking about the capacity of a machine, which is limited to tip size and amperage. I think our definition of critical weld also differs. There should be no critical welds in the construction of a locost, critical meaning minimal bead thickness and length for the applied load, butted and loaded purely in tension.

This similar to a dicussion about single shear versus double, where single is not as good as double but is acceptable under certain conditions.

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PostPosted: October 28, 2012, 5:15 pm 
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Sweet, thanks for the info, guys! Looks like I've got some reading to do... but tonight is for sleeping... I've been up for almost 3 days!


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PostPosted: November 6, 2012, 2:26 pm 
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I likely wouldn't put alot of stock in it, probably do whatever is most comfortable, but I've heard the phrase "When with slag, drag". I think it has something to do with less splatter on the surface your trying to weld.

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