Howdy,
On Wed, 19 Nov 2003, Scott Correa wrote:
> Heat controls fusion, not spatter..................... Spatter is a weld
> defect caused by lack of material prep, the wrong wire, or insufficient
> gas flow. It is basically excessive oxidation of the base metal. My
> guess is that you are using general purpose wire, ER70S3. Spend a bit
> more and go to ER70S6. It is a more highly refined de-oxidised wire.
> Secondly, clean the metal of impuritys. Especially mill scale. Hot
> rolled low buck steel has an oxide coating you must remove for pretty
> welds. Ever wonder why it doesn't rust until after you weld it? GRIND
> it off. Wire brushing is iffy. The same can be said for rolled sheet.
> Insufficient gas flow makes for poruous (sp) welds that have gas bubbles
> in them and is easily ID'd visually. A second clue is a brown slimy
> crap film left after the weld is finished. A good weld will have bead
> in the center that melts into the base metal, a cleaning zone of bright
> metal outboard/touching the weld/base metal junction and some heat
> related shit outside the cleaning lines.
Well, I am using ER70S6 (Lincoln's L-56 actually).
I do frequently see a bit of a brown film on the top of the end of the
weld bead, and I mostly don't grind off the mill scale in the weld area
(though any rust I do typically clean up). Does the mill scale cause a
poor weld or just more spatter?
Seems like I see porosity problems only when I'm filling an area and need
to pulse the trigger a bit to control the weld puddle. Sometimes the
resultant weld looks pretty porous. I'd been thinking that was more due
to the gas not flowing during the off cycle of pulsing the trigger...
Something I'd thought about doing was rigging up a way to keep the gas
flow going but not the wire feed / current, so that I could pulse away
without the gas shutting off.
> Good wire welding (long arc) sounds like frying bacon........... a nice
> sizzle sound. Short circuit welding happens in pulses as the wire hits
> the work, melts and moves back into contact with the base metal. Spray
> transfer/globular transfer is the use of a slow wire speed to allow the
> wire to melt prior to dropping into the puddle. The polarity of the arc
> transports the material.
>
> Have a good day
> Read the basic welding books or
> go to a welding supply shop for a lesson.
> They are really good about troubleshooting little problems
> and if they tell you they don't do that, go to a better shop.
Do you have a recommendation for a good book on MIG/GMAW short circuit
welding? The welding class I took and most of the basic books I've seen
focus on arc welding, which doesn't seem to have a ton to do with MIG
welding and certainly hasn't helped me to learn when/how to set the
machine.
It seems everyone can tell you that you want a frying bacon sound... but
few people can explain how you adjust the machine based on what you're
actually hearing.
Mark
|