[klwright]

I have been working on a project for the last few months where I am using hardware store bought 1/8" thick flat bar. The Problem I am having is it seems when I stop a bead, let it cool for a bit, and start again, I get a bunch of porosity in the weld with color flashes from the arc. I have religiously removed the mill scale and cleaned these parts with Acetone.

Seems like if I continue the bead and do not stop, this problem does not occur. Otherwise the beads look great. Has anyone else seen this? What am I doing wrong? Is this just crappy steel?

[dave powelson]

A picture of the actual problem would detail much more than you've actually said
and eliminate having to guess at what's going on.

Did you sand or grind the steel, then acetone wipe?

At the end of the weld bead is there a 'suck hole' a.k.a.--'crater'?

This is caused by abruptly stopping the arc, rather than fading it out thru pedal control and/or 'long arcing' while still fading out on the pedal. Craters are porosity.

Torch technique/angle/distance, gas flow, puddle control can all contribute to hidden or intermittent porosity.

[dynasty200sd]

As mentioned above, more information is needed to better understand what may be happening. Some things that come to mind are;

What type of tungsten are you using?
What is the size of the tungsten?
What cup size are you using?

Are you using a standard collet body or a gas lens?
What flow rate is your shielding gas set to?
What type of shielding gas is being used?

What type of filler wire is being used?
What is the size of the filler wire?
What is the material you are welding?

How much amperage is the machine set to?
Are you using a foot pedal, torch switch, etc..?
Are you using scratch start, lift start, or high frequency to initiate the arc?
What are you using to sharpen the tungsten?
Are you using the abrasive to sharpen the tungsten for anything else?

How close are you keeping the tungsten tip to the workpiece?
What type of joint are you trying to weld?
What is the torch's travel angle?
What is the torch's work angle?

[Poland308]

Do you have an adjustable pre purge?

[LtBadd]

As mentioned above, more information is needed to better understand what may be happening. Some things that come to mind are;

What type of tungsten are you using?
What is the size of the tungsten?
What cup size are you using?

Are you using a standard collet body or a gas lens?
What flow rate is your shielding gas set to?
What type of shielding gas is being used?

What type of filler wire is being used?
What is the size of the filler wire?
What is the material you are welding?

How much amperage is the machine set to?
Are you using a foot pedal, torch switch, etc..?
Are you using scratch start, lift start, or high frequency to initiate the arc?
What are you using to sharpen the tungsten?
Are you using the abrasive to sharpen the tungsten for anything else?

How close are you keeping the tungsten tip to the workpiece?
What type of joint are you trying to weld?
What is the torch's travel angle?
What is the torch's work angle?

I realize this is the TIG forum, but this is the OP's first post. It would be helpful for them to confirm the process, machine settings and such.

['Stang]

[quote="klwright"]I have been working on a project for the last few months where I am using hardware store bought 1/8" thick flat bar. The Problem I am having is it seems when I stop a bead, let it cool for a bit, and start again, I get a bunch of porosity in the weld with color flashes from the arc. I have religiously removed the mill scale and cleaned these parts with Acetone.

Seems like if I continue the bead and do not stop, this problem does not occur. Otherwise the beads look great. Has anyone else seen this? What am I doing wrong? Is this just crappy steel?[/quo

Are you cleaning the weld before you restart? Contamination floats to the surface. If you don't clean before you restart a weld-you are lighting up on dirty material.

[chillrich]

As a beginner I am having similar issues TIGing mild steel. I grind but do not acetone/clean. Sometimes at the end of my weld during postflow you can see the contaminants bubble up out of the weld pool, like a volcano. Is it possible or likely that my slow rate of travel causes contaminants to be pulled in from the bottom side of the base material?

[Oscar]

As a beginner I am having similar issues TIGing mild steel. I grind but do not acetone/clean. Sometimes at the end of my weld during postflow you can see the contaminants bubble up out of the weld pool, like a volcano. Is it possible or likely that my slow rate of travel causes contaminants to be pulled in from the bottom side of the base material?

If you puddle a single spot on mild steel, do you get a whitish-orangish-browninsh patina around the weld bead? Also, how many seconds is your postflow?

[chillrich]

I just did 8 tacks on freshly ground new steel. All mill scale and finish removed. One of the tacks spattered and did exactly what you are describing. I ground that area again and it work perfect. I will clean this piece with acetone or alcohol and TIG the joints and see if there are problems.

Postflow is torch valve 3-6 seconds usually, just until the melting is no longer molten.

[klwright]

Successful

339.JPG (47.29 KiB) Viewed 633 times

As mentioned above, more information is needed to better understand what may be happening. Some things that come to mind are; ANSWERS BELOW

What type of tungsten are you using? 2% Ceriated
What is the size of the tungsten? 3/32
What cup size are you using? #8

Are you using a standard collet body or a gas lens? Gas Lens
What flow rate is your shielding gas set to? 18-20cfh
What type of shielding gas is being used? Argon

What type of filler wire is being used? 70ers
What is the size of the filler wire? 1/16
What is the material you are welding? Flat plate (hdwr store hot roll to motorcycle frame tubing)

How much amperage is the machine set to? 175
Are you using a foot pedal, torch switch, etc..? Foot pedal
Are you using scratch start, lift start, or high frequency to initiate the arc? HF start
What are you using to sharpen the tungsten? Sanding disk
Are you using the abrasive to sharpen the tungsten for anything else? yep (know I shouldn't but hasn't caused problems that I can see)

How close are you keeping the tungsten tip to the workpiece? 1/8
What type of joint are you trying to weld?fillet
What is the torch's travel angle? 10-20degress
What is the torch's work angle? ???

My machine is a Dynasty 300SD, preflow is .5s postflow is 5 sec

Answering some of the other comments on this thread, I completely grind the surface to shiney metal and clean with acetone. I have not cleaned it after welding a bead has been run but sometimes the porosity shows up in the middle of the weld, never at the start. I have attached three pictures, one of a successful weld, over 11" long. The other, porosity began to sputter at about the 6" mark. You can also see on the outline on the plate from a weld on the backside, covered with scale. If I need to clean the steel AGAIN before I restart, OK, I leaned something today!

Most of my TIG welding is on Aluminum, I usually MIG steel.

Thanks you all for jumping in, I am overwhelmed with the input