Pre-flow Argon gas for Mig on Aluminum

By daedoo62 Date 10-22-2004 03:32

I have a Lincoln Pro Mig 175 with the Aluminum kit. It seems to be feeding just fine. I can make a pretty good weld with it but noticed that the start of the weld is uglier than the rest. Some of this is due to the material getting hoter as I go, but I think part of it is due to there being a delay in the shielding gas forming a pool around the weld.

I have tried to purge the line prior to starting a new weld to make sure there is pure Argon in the line.

I'd like to set up a separate foot switch that provides power to the gas solenoid manually. I would hit the switch and hold the torch close to the plate to be welded for 3 or 4 seconds and then start the weld.

Has anyone tried this? I know the more expensive machines have variable settings for pre & post flow of the gas, but has anyone tried operating the gas manually?

This way I could also allow gas to flow for a few seconds after I cut the arc.

The solenoid seems to be rated at 208 volts and running at 220, while the input is at 244 volts at my home. I don't think I should try to operate the solenoid on the straight 244 volts as it might overheat and burn it out.

By daedoo62 Date 10-24-2004 02:48

Any suggestions would be appreciated.

By brande

Date 10-24-2004 03:15

Wish we knew more details about your problem. Just what is the "ugly" you describe??

A few thoughts in no particular order.

You really shouldn't have gas problems at the start after your gas system is purged. A few welds should purge your gas system, as would loosening your drive rolls (so not to waste wire) and pull the trigger for 12-20 seconds at the begining of your weld session. Your weld power (contactor) and gas solenoid do operate at the same time. There is no delay between them on the type machine you are using.

Unless, of course, the solenoid is bad and is "hanging up" when power is applied.

Fabricating a preflow control would not be all that difficult.
A delay relay, appropriate pot to set timing, and some wire is all that would be needed. A schematic diagram of your machine would be a necessity.

Another cheaper and easier fix might be-start your arc appx 1/4-1/2"
ahead of your intended starting point. Run back to your intended start area (quickly-to avoid build up of weld metal) and then continue as originally planned. This technique can give some preheat to your start, reducing the mig start "lump" and get your gas going by the time you reach your starting point. It may cause some surface porosity-but that may be better than your original problem.

Also-look at your weld. If you see a tan-brown smoke or soot around it-get another cyl of argon. You may have some wet gas. Not uncommon in cylinders filled in mid-late summer. A loose connection, leaking hose,
etc. can give similar results.

Keep us posted.

Good Luck

brande

By daedoo62 Date 10-24-2004 20:09

Thanks. I'll try starting my weld a little inside the start point as you suggested and then run to start and back and see if that helps.

It just seemed to me that if the gas starts to flow at the same time the arc starts, then the gas wouldn't have had time to surround the base metal yet and might effect the quality of the weld.

Do you see any problem with operating the gas solenoid manually?

If I did this, I would install a switch on the back of the welder so I could operate the gas solenoid via a foot switch or have it come on with the torch trigger as normal. If my project was large I might just use the automated system as the welder came, but if I were trying to weld a smaller Aluminum bracket that I wanted to look a pretty as possible, I would use the foot switch and allow pre and post flow of gas.

I will also check for the tan-brown smoke or soot as you suggested.

Thanks.

By brande

Date 10-27-2004 01:06

Operating the solenoid manually would not be a big problem. A little wiring is all that would be needed.

I guess my point is that there are many welding aluminum without such a modification-successfully.

Yes some do have pre/post flow devices on their feeders. Many do not.

I wish I could see what you describe-perhaps your problem might be somewhere other than gas flow. Metal contamination, improper weld prep, bad gas, bad wire, wrong wire, are but a few things that can make your aluminum welding difficult.

Any more detailed info you could provide would help tremendously.

Keep in touch

brande

By daedoo62 Date 10-27-2004 15:30

I am welding with .35 4041 aluminum wire.

I tried a weld last night on 6061 aluminum square tube and 6061 flat bar. Both are about 1/8 " thick.

Can you use 4041 wire on 6061 material?

I have been using scraps of different kinds of aluminum that I had lying around.

I did the wiring and now can trigger the gas via a foot switch or flip a switch on the back of the welder to use the normal setup with gas flow from the torch trigger.

I like being able to start the gas to purge the line or depressurize the regulator when I'm done without having to release the drive roller etc..

To prep my aluminum for welding I have been using a Stainless wire brush that I have only used for cleaning aluminum.

When I tried to weld the 6061 material last night I found that the wire would melt straight through the flat bar. I couldn't get the aluminum to pool at all. Again, is this because of the material I was trying to weld?

When I first got the alum kit for my welder I tried to weld a thick piece of 6061 plate ( 2 pieces together ) The material was too thick to get much penetration but the weld bead looked pretty good and when I ran a bead down both sides of the plate It ended up being pretty strong.

I know I have a lot to learn and will need to practice a lot.

Any suggestions are appreciated.

Thanks.