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Up Topic Welding Industry / Technical Discussions / Worm holes in flux core welding
- - By - Date 06-30-2000 12:56
What causes worm holes while using flux cored wires. I've heard lack of gas, but changing gas pressures hasn't fixed the problem. Cleaning the base material hasn't made much difference either. When I say worm holes I'm not talking about porrosity. It's more of a concave look on the face. Normally long like a worm.
Parent - - By - Date 06-30-2000 14:27
Well TB, here's what I think you've got. It's been my experience that a gas bubble has been trapped at the molten/solidified slag interface at the back edge of the puddle. It gets dragged (like plowing a furrow)along until which time some change affects the cooling rate of the slag. A change would be that the welder slowed down and let the bubble escape or his arc length changed alittle and it either escaped or froze, stopping the "worm-tracking".

Over the years I've experienced several causes/effects for "worm-tracking" to occur and remedies for correction.
1) If the wire has been out of the package for quite a period of time and the humidity levels are high, it'll draw mosture into the flux which leads to porosity.
2) If the welder is running with too short of a "stickout". I've observed this when the welder has been using GMAW for a while and switches to FCAW and forgets to lenthgen his "stickout".
3) Voltage is too low!
4) The welder could be traveling too fast and not allowing time for the deoxidizers to completely do their job because his puddle (slag) is freezing too fast and not giving the gas a chance to escape.
Hope I've helped you. Good luck!
Parent - By ADK (*) Date 07-06-2000 14:46
Traditional folded wires also use lubricants that can be trapped in the folded seam and these lubricants are usually hydrocarbons and they can form porosity in the molten weld puddle. There is an article in "Practical Welding Today" Jan/Feb 1998 which addressed this form of porosity. Unfortunately the suggestion was to rebake the wire. This solution burns off the lubricant and causes wire feeding problems and is an expensive step: taking wire out of feeder each day, storing in oven, re-issue the wire before each shift. You can imagine the cost for ovens, energy, administration, manpower and the loss of productivety to incorporate such a procedure. Seamless flux cored wires such as those from STEIN are not succeptable to moisture pickup through sheath that forms a tube (there is no seam) and these wire are copper coated. The coating improves wire feeding, current carrying capability and the source of hydrogen has been eliminated.
Parent - By - Date 08-04-2000 07:24
Just seen your 'worm holes' question. I,ve seen this many times. The most common reason for worm tracks is too high a voltage. Reduce your voltage by 2 volts as a starter. Always set up your arc length on FCAW with a 'zero arc length' ie the tip of your wire appears to be level with the plate surface & the arc is below the level of the plate.
If this does not work e-mail and I can give other tips

Regards

Keith Temperley
Parent - By wld (*) Date 11-10-2000 02:32
all these replies have very good info,
i was having the same problem welding flat useing allposition (AP)fluxcore wire and found out that AP was not good for that.
Up Topic Welding Industry / Technical Discussions / Worm holes in flux core welding

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