Posted this to a web board but didn't get the answer I was looking for so
here it is...
What is it that makes 6011 and 6010 electrodes solidify quickly? Is it the
fact that there's only a little slag (blanket) covering the pool so it
loses heat quickly? Or is it something in the coating that conducts heat
out faster? Composition of the metal? Does the deeper penetration put it
into contact with more of the base metal which conducts heat out faster?
These electrodes are coated with cellulose, in other words a sawdust. It
burns producing carbon dioxide. There is no mineral product like rutile so
the slag or glass you see on the surface is a bit of silicon oxide and ash.
You are correct that it cools rapidly because there is no blanket covering
the weld metal.
The arc characteristics of the rod are determined by the composition of
the gases at the arc. Carbon dioxide tends to be a relatively "hot" gas.
The correct term is a more active gas than say argon which is less active.
I am guessing that the gas composition of burning 6010 might have someting
to do with the rate of freezing of the molten metal.
With cellulose going into the arc, carbon and oxygen are not the only
atomic species going into the arc. There's hydrogen as well. That's
what's crucial. You get a lot of hydrogen. And hydrogen raises the
arc voltage and therefore the forcefulness and heat of the arc.
Randy has responded with the main point. There is very little slag, so
the heat radiates away fast, making a fast-freezing weld-pool. I do
wonder for root runs whether, with being a penetrative arc and you
using it in that way, there is something about a tall narrow weld metal
volume losing heat fast into big conduction paths of the plate on
either side of the weld.
I have to declare that I am a dreamy scientific type and express
interest having been amazed by handling these rods at a technical
college. And as a scientist I have followed-up and studied them. I
have made other posts on the subject, which may be looked on in askance
but may also have some value.
I have commented previously on the molecular toughness of cellulose
("wood") in surviving intact to get into the arc and release its
hydrogen there. This is the issue about don't exceed the current
recommendation of the rod, otherwise you will char the cellulose before
it gets into the arc and the rod will go "flat".
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