Al 5/8 thick carbon steel 65000 tensile, FCAW with 75/25 .052 dia wire parameters 145-215 amps 23-29 volts travel speed 250-350 stickout 3/4 inch. joint configuration 45 degree included. gap varies from 3/16 - 1/2 inch. appreciate any info or input.
Voltage sounds a bit low for 0.052". Try bumping it up to 26V minimum. I assume 75/25 gas means 75% argon/25% CO2, which is the correct gas for E71T-1. What gas flow rate are you running? What is the electrode classification? Are you grinding weld preps to clean metal before welding? How thick is each weld layer?
40 CFH electrode 71T-1 metal is clean . layers 1/8 inch average
By CHGuilford 
Date 03-06-2007 02:03
Edited 03-07-2007 10:14
Actually, your amperage is a bit on the low side for 0.052" FCAW. Using Lincoln Outershield 71M as an example (mainly because that is what I have handy at the moment), 0.052" wire should be between 150 and 405 amps. You are running on the low side so are probably freezing your puddle a bit too soon. Generally wires run better at the middle or upper/middle ranges.
I'm not sure what you mean by 250-350 on the travel speed; that sounds more like your wire feed speed range.
You also didn't say how many passes you need to fill the joint so it's difficult to tell how large your passes are.
Assuming you are running passes equivalent to a 1/4" fillet in cross sectional area, you should be running a heat input of about 30 kilojoules/ inch.
That would mean about 6.7 ipm travel at 23V/145A or 12.5 ipm at 29V/215A (29V sounds a bit high for C25 gas). I suspect you would have trouble with slag rolling ahead if you run 6.7 ipm at the low end. More of the arc energy would be dissipated on the puddle rather than penetrating the base metal and mixing with the base metal. Naturally, pushing instead of dragging would make the problem worse.
The higher travel speed at higher ranges would mean slag and gas have less time to "boil out".
If it were me, I'd try 24-25 volts, 270 - 330 amps, 10 - 13 ipm travel with that wire size.
The first thing I would do is go to the manufacturer's web site to see what their recommended welding parameters are. Lincoln has the information presented in the most usable format. ESAB does a fair job of it. For the most part, the optimum welding parameters are different for each manufacturer. Set the welding machines using the voltage, amperage, and wire feed speed recommended. If they do not list the electrode stick-out, vary it until the amperage and voltage agree with the manufacturer's recommendations.
Electrode stick-out can have a pronounced affect on the weld, yet most welders do not appreciate the importance of the distance maintained between the contact tip and the work piece. Once the electrode stick-out has been established, the welder must hold it constant in order to maintain the proper amperage/wire feed speed relationship. As the electrode stick-out increases, the amperage with decrease. Likewise, if the electrode stick-out is decreased, the amperage will increase. Each electrode classification and diameter has a small range of electrode stick-outs that produce the best results.
The three variables that can be set, using a conventional constant potential power supply, are the voltage, wire feed speed, and electrode stick-out. The amperage is going to fluctuate as the welder varies the electrode stick-out, so that is a variable that is difficult to control, but easy to monitor via the ammeter.
The slag inclusions can be there result of incomplete cleaning between weld passes or improper technique. In some instances, I have seen "porosity" with slag entrapped in the porosity when the arc voltage is too high. Porosity can also result if the contact to work distance is too great or the welder is near a door that is opened or closed allowing the shielding gas to be blown away be sudden gusts of air.
Other than a shielding gas problem, precleaning and interpass cleaning is the next area I would look at to reduce porosity. Are you using compressed air drive tools for cleaning? Compressors are lubricated with oil. If you do not have a filter on the system to remove the water and oil, you could be depositing a mist of contamination on the surface of the plate or weld each time you use the grinder or needle gun.
Change the contact tip frequently. It is a consumable that is intended to be changed on a regular basis. I've had welder tell me how they have used the same contact tip for a week or more. That tells me that they haven't been welding very much during that week or the contact tip is so worn that it is no longer making good electrical contact with the electrode and the welding voltage and amperage is most likely fluctuate while welding.
I hope this helps.
Best regards - Al
