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Up Topic Welding Industry / Technical Discussions / slag.......
- - By JA (**) Date 10-14-2007 21:26
so your welding in the flat position , the flux and all the contaminates float to the surface because there lighter than the molten metal , so why is it that when welding in the overhead position , the slag does not float upward (due to gravity) and into the bottom of the weld , in this case , the root.............?
Parent - - By fbrieden (***) Date 10-15-2007 00:21
Material density (steel) allows lesser dense material (slag) to precipitate to the surface as solidification takes place. This process may be in any position.
Parent - - By DaveBoyer (*****) Date 10-15-2007 04:28
That is similar to how a Thermos knows weather to keep things hot or keep things cold. :-)
Parent - - By Tommyjoking (****) Date 10-15-2007 05:59
well  lets say you just run a flat groove weld with a generous gap with a 7018...you have flux on the backside as well right?   Its a density and chemical process that causes this to happen....I do not think gravity has anything to do with it.  
Parent - - By 803056 (*****) Date 10-15-2007 16:55
I would place my money on surface tension.

Al
Parent - - By js55 (*****) Date 10-15-2007 20:23
Slags are also designed to be the last constituents to solidify. Therefore, when the weld metal is forming a solidification front it is pushing molten slag out of it.
Parent - - By 803056 (*****) Date 10-15-2007 20:35
It that always the case? Consider some of the FCAW slag systems where the solidifying slags help "shape" the weld bead such as when welding vertical using upward progression.

I believe some of the slag systems used by Lincoln utilize slags that solidify before the weld metal.

Best regards - Al
Parent - - By js55 (*****) Date 10-15-2007 21:55
To be honest Al, I don't know. But higher temp slags have a tendency to be very difficult to deslag. Deslagging is one of the criteria requiring slags with lower solidification temps. Or at least a method of such. If memory serves (puttin my brain in the Wayback Machine) this is one of the primary difficulties in FCAW for aluminum. The slag solidification is just too close to the weld metal solidification temp. And if slags were to solidify first then slag entrapement it seems to me would be more problematic. But I ain't no ceramic engineer nor no flux guru thats for sure.
Wish we had more filler metal guys in here.
Parent - By 803056 (*****) Date 10-15-2007 22:16
I agree with that.

I remember welding with some of the Lincoln self-shielding flux cored wires, we used to point the gun downward and we would watch the slag solidify before the weld did while welding vertical up. It was as if the slag gave the weld bead the shape and held it in place until the metal solidified. It was much different than welding with an E71T-1 electrode where we would point the gun up slightly.

You're right about the slag removal, it was more difficult to remove completely than the other fluxes.

Best regards - Al
Up Topic Welding Industry / Technical Discussions / slag.......

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