Flux Properties?

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What about it's flux gives 7018 it's great impact qualities?
Reply:Don't know, but each company I'm sure has their own proprietary secret recipe of flux.  Each electrode type is also a different mix of various alloys, giving different and unique characteristics.Lincoln Power Mig 216Lincoln AC/DC-225/125Miller  625 X-Treme PlasmaMiller 211 Forney 95FI-A 301HF 91110Victor Journeyman O/PMilwaukee DaytonMakita  Baileigh NRA Life Member
Reply:Here are the deposit compositions for 6013, 7014, and 7018, maybe you can draw some conclusions from them?Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Here are the deposit compositions for 6013, 7014, and 7018, maybe you can draw some conclusions from them?Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:The fact that the flux contains almost no hydrogen has a direct effect on the weld deposit.
Reply:Chemistry of the weld deposit is the primary reason for E7018's toughness.  Manganese is a strong contributor in this electrode.  But the pH of the flux is also a factor.  E7018 is what the experts call a basic electrode.  This characteristic affects not only the chemistry of the weld deposit, but also affects the number, size and type of beneficial oxide/carbide/nitride particles that become incorporated into the weld deposit.  Imagine that a steel weld deposit is similar in some respects to concrete.  Concrete has a mixture of large and small particles, stone aggregate and portland cement.  The stone are what give concrete it's strength, to a large degree.  The portland cement acts like a glue or matrix that holds everything together.  But too much stone and the concrete falls apart, too little and it's weak, soft, and crumbly.  This is a gross generalization, but hopefully you get the idea.On a microscopic scale, the structure of steel is similar to concrete.  You have a matrix, Iron, that contains lots and lots of extremely small additions.  Small additions of Carbon for example can sit in between the iron atoms, and mechanically the carbon atoms act like a wedge.  It makes it more difficult for neighboring atoms to slide past it.  At the atomic level this is what is happening when you bend a piece of steel.  A slight bend causes the space between the atoms to stretch.  The steel springs back to it's original shape when the small load is removed.  A larger load causes the material to permanently change shape; this is atoms sliding past one another.  Anything that discourages this from happening makes the steel stronger.Other additives, like Chromium, Manganese, Nickel, and Silicon, sit in the matrix in place of iron atoms, rather than being squeezed in between like small additions of carbon.  These alloying additives also act to discourage the slip of neighboring atoms under load.  Think about a childs ball pit.  Lots of small round, yellow plastic spheres.  Now throw a basketball into the mix and stir.  The smaller yellow spheres will slide around the basketball.  Same general idea when you insert a larger atom into the iron matrix that makes up steel.Last idea.  Now add a bunch more of these alloying ingredients....What happens?  As an analogy, what happens when you pour too much sugar into your iced tea or coffee.  Some dissolves and at a point the rest just settles on the bottom of the glass.  The same principle applies to adding alloying ingredients to steel.  Evenually those additives won't sit neatly in between the iron or in place of the iron atoms.  They can gather in larger clumps.  The analogy breaks down here.  Generally speaking, in steel, lots of very small, scattered clumps can be beneficial.  The serve as a barrier to the motion of the surrounding iron atoms.  This translates into a stronger material.  But eventually, as more and more alloying ingredients are added to the steel, the clumps grow larger and more numerous.  They thin out the iron matrix to the point that it can no longer support as much load.  The 'clumps' become weak points; think back to the idea of too much stone added to concrete.All of this circles back around to E7018 because the flux chemistry and the alloying ingredients act together to produce the ideal structure.  A mix of iron with lots of alloying atoms jammed in between and in place of the iron atoms in the overall matrix of the steel.  AND just the ideal number and size of these clumps of oxides, carbides, and nitrides scattered throughout the steel to further resist the movement of iron atoms under load.If you look at the entire class of EXX18 electrodes, you'll see a pattern.  As you increase the strength of the weld deposit from 70, to 80, to 110 Ksi, you'll see the %elongation decrease in a corresponding way.  % elongation is a measure of how far a standard test specimen will stretch, permanently deforming, before it breaks.  The higher strength comes from increasing amounts of alloying additives; but in trade for toughness and ductility.  think about the difference between rubber and glass.  Rubber has low strength but very high toughness and ductility.  Glass has extremely high strength but virtually no toughness; if you apply enough load it shatters rather than bending.  Steel has the same basic properties and behavior, just not to the same extremes as the two examples.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector