TIG Welding Problems
 

Hey everyone, I have a question for you...

First, here's the background....
-The welder in question is a brand-spankin' new Miller Syncrowave 200
-I know (as I have checked the entire gas delivery system) that the argon is making it to the gun
-I am attempting to weld 6061-T6 aluminum in DCEN (direct current electrode negative)
-I am using 7" long, pure tungsten electrodes (green band) in 3/32 dia.
-The gun (electrode holder and gas/electical line) is a Weldcraft (can't remember the model)
-I have the ground clamp postioned as close as possible to my workpiece, which is on a steel bench.
-I have tried to clean the elecrode in AC, but the problem persists...

Here's the problem...

In order to get a puddle, I have to strike an arc on the metal. But with this machine (I have used the same model before), that should not be necessary. As soon as the electrode gets within 1/4 to 1/8 of an inch of the metal, the arc should show up, no matter how much I'm on the pedal. By striking the arc, I am in turn contaminating the elctrode, and ruining the weld before I have even formed a puddle. The puddle does not appear shiny, and the electrode ends up black, without a properly balled tip. I have checked my settings time and time again, and have practically memorized all the literature that was shipped with the machine. I have also read the welding process books at my school almost religiously for the last three years, and am a pretty experienced TIG welder for my short 17 years, especially with 6061 aluminum.

Is it me or the machine? What in the world am I doing wrong? I think it may possibly be a current problem with the machine, as a group of my colleagues set up the machine without my supervision.

:confused: Thank you so much for your help! :)

Re: TIG Welding Problems
 

It cannot hurt to perform the setp again as per the book, as a double-check.

Remember, an arc needs voltage to form (as in "jump across the gap"), not current. Current only comes into play once the plasma arc is formed.

Having no experience with TIG I really can't answer the question directly, but I hope what I wrote helps.

Don

Re: TIG Welding Problems
 

sounds to me like you are not getting gas flow. Are you sure you have your regulator set high enough and that you have the correct flow nozzle on your gun for the size of the material. Also check to see if your gas ports on your gun are clogged.

Also how fine of a point do you have ground on your tungsten?

Re: TIG Welding Problems
 

It does help, as you brought up a good point. Thanks!

I had originally suspected such a problem, and was told over and over by peers that the gun was getting gas. I'm not so sure if they know what they are talking about, since I can't hear the afterflow. I thought it may have just been a quiet gun:rolleyes: Stupid me...

I had ground the tungsten to a sharp point, but isn't the tip supposed to ball up while welding aluminum?

Re: TIG Welding Problems
 

it should be a fat sharp point, something like the geometry of a golf pencil (but smaller obviously)

Re: TIG Welding Problems
 

I'm Dick's son. I think your main problem is that you need to be using AC high frequency continuous. Gas flow should be about 10-15 CFH, mainly depending on your cup size. I don't think that particular machine has a preflow so you need to hold the torch in the air, depress the pedal so it goes into postflow mode and before it turns off go to where you want to strike up. With the gas flowing press the pedal about a quarter of the way down and wait for the high frequency to start the arc (it ionizes the argon and then goes to welding amps). The electrode should be tapered and will ball up on its own when you weld. You should not have to scratch start hold the electrode about 1/8" away from your work. With aluminum clean the work with a STAINLESS brush for aluminum only, and clean your filler with a scotch brite for aluminum only. Keep your filler very low (about 10-15 degrees off work). Try connecting the ground clamp to the workpiece at least once or make sure the table actually makes good contact with the aluminum. Also, before I forget make sure it is in TIG mode! Use the tig weld calculator on the miller website to adjust your max amps and pay attention to the duty cycle!

Once again make sure it is clean. When you are done cleaning it, clean it some more. Aluminum tends to get "sucked" onto the tungsten so if that happens just break it off with pliers carefully and either point it or let it ball if its a clean break.

I've welded aluminum up to 260 amps (not fun) and spent the summer welding Inconel turbine blade tips (also not fun).
Wordy I know but these are the basics.

Re: TIG Welding Problems
 

Whoah:ahh: Thanks!

One question...
I was taught how to TIG with this same machine (at LOLHS), and IIRC, we were welding in DCEN... Am I just mistaken? (I haven't TIGed since the 2008 build season:( )

Re: TIG Welding Problems
 

Steel is welded in DCEN, but when welding aluminum, use AC. Also, to prep your tungsten tip, put the unit on DCEP and strike a short arc on your work piece. This will melt the tip to a nice ball w/ a dia. of about 1 1/2 the thickness of the tungsten. Don't forget to put it back on AC though when your done, or you'll melt the torch.

Re: TIG Welding Problems
 

If you were TIG welding aluminum it couldn't have been DCEN or DCEP. TIG welding aluminum is only possible with AC high frequency with that machine because DCEP pulls oxides from the aluminum surface but will melt the tungsten with 2/3 heat on it. DCEN provides 2/3 heat to the work without melting the tungsten. AC changes between the two 60 times a second but the HF is required to maintain the arc between cycles.

DCEN welding aluminum is only for stick welding which is recommended for 1/4" and thicker.

Hope this helps. Sounds like someone set the machine up and didn't really explain everything. If all else fails there's the machinist's response, "the answer is in a book somewhere". I would recommend finding a copy Welding Principles and Applications by Larry Jeffus.

Edit: I've tried Spazdemon's suggestion many times for balling the tungsten but really only to save time or guarantee a good tip.

-Tan Linn

Re: TIG Welding Problems
 

There is a wealth of knowledge on the Miller site (www.millerwelds.com) that gives you basic settings for all welding processes including TIG as well as technique suggestions. There is even a TIG calculator which helps you set up your machine for different materials and thicknesses. Check out

http://www.millerwelds.com/resources...ur-skills/tig/

It tells you that you need to use AC High Frequency for Aluminum as well as the initial settings to use for the thickness and type of weld you want to make.

Welding is Fun!

Re: TIG Welding Problems
 

Sounds like you got it fixed. One thing that happened to me was the petal was too close to the welding table and was getting caught, so I couldn't push it down all the way.

Re: TIG Welding Problems
 

DCEN is sometimes used for TIG welding of thick aluminum, with lab-grade helium used as a shielding gas. Here's a forum thread about it:

http://hobartwelders.com/weldtalk/sh...ad.php?t=25034

Re: TIG Welding Problems
 

Is your high frequency on continuous, or is it just on start? Start is only for steel and stainless, you need Continuous to help break the oxide layer along with the DCNeg current flow.

Re: TIG Welding Problems
 

Thank you for all of your advice, everyone. I do appreciate it. But I have come to the conclusion that the machine is not getting gas to the gun. Is there any way to clear the lines? They are brand new, so I wasn't expecting this problem. I have already made sure that the gas is atleast getting to the back of the machine, since when the tank is opened slightly, gas comes out of the end of the tank line. :confused:

Re: TIG Welding Problems
 

Replace the lines and or gun/line

Re: TIG Welding Problems
 

"Brand new"? Then call Miller. They are known to have good tech support. It could be a pinched line, bad connection to the gas solenoid due to shipping shakeup, etc.

Re: TIG Welding Problems
 

Yes, brand new. The welder has been set up for less than a month, and still hasen;t successfully laid a bead in TIG mode. The arc welder works just fine.

Re: TIG Welding Problems
 

The welder is fixed... It turned out to be a clogger gas soleniod, just as I had suspected... Now I need to relearn the settings. Thanks for all the advice, especially thos who to the time to PM me such exhaustive explainations. It really helped. You guys are great!:D

Re: TIG Welding Problems
 

One quick way I've seen to put a Clean Ball on the Tip of your electrode is to grind the electrode to a "blunt pencil" point and use a copper Plate about a 1/4" thick as your first target. This is less likely to contaminate your electrode than your actual aluminum work piece. Also you should grind your electrode axially (along its length) not radially across its diameter. This produces a more directed first strike and allows you to better control the ball formation.

Re: TIG Welding Problems
 

Thank you for the tips. I have benn grinding the tip axially, I just didn't know about the copper plate thing. :D

Re: TIG Welding Problems
 

To weld aluminum, use AC for the actual welding and DC positive
prepare the electrode. Use a pure tungsten (green) electrode.

You use DC positive to prepare the electrode because
you want to melt it a little without forming a puddle.
You always use a separate thick plate for this and
a 1/4 thick (or thicker) aluminum plate will work fine.
Copper is better, but I have never had access to one.

To prepare (ball) the electrode, grind it flat on the end, and then
debur just enough to remove any flash left from the grinding.
Debur it at about 45 degrees, but just enough to remove any
flash. The basic geometry of the ground electrode should
still be flat on the end. To ball (really hemisphere) the electrode,
set the welder to DC positive and then light an arc on a thick
aluminum plate placed so that it is level and the torch is pointed
straight down. Use about 1/8 inch clearance
between the electrode and the plate, or just a little closer. Crutch
your hand to avoid contact between the electrode and the plate.
Watch the end of the electrode carefully as you do this and
you will see the edges melt and the hemisphere end form. Your
goal is to get a hemisphere on the end of the electrode without
having a "ball" form that has a larger diameter than the electrode
itself. You have to be careful with the heat as it is easy to overheat
the electrode with DC positive. With experience, you will notice
that you get a little extra flare of light when the heat it just enough
to melt the end of the electrode and you will start judging things by
watching for this flare as you increase the heat. Once the heat is
right the end of the electrode melts and develops the right shape
in just a couple of seconds.

Since you need to make adjustments to the welder to prepare
electrodes, and electrodes come in packages of 10, it pays to
prepare them all so you can just change out electrodes
without having to switch setups when you contaminate one.

You will be turning the current down when preparing
electrodes as DC positive puts a lot of heat on the electrode,
and then turning the heat back up for AC welding of aluminum.
Don't forget to turn the welder off before changing polarity.


Have fun,
Eugene

Re: TIG Welding Problems
 

One possible source for "scrap" copper plate is the offcuts of bussbars in high current industrial electrical installations. try to find an industrial electrical contractor and the might be able to donate a piece or at least let you buy it at scrap pricing $3-4.00 per pound. A 3X3" piece is what we've used at several fabricators I've worked at.