"hot crack" issue. tacks are a dull flat grey color and are porous and brittle

[chart102]

Hello my name is Casey. At my job I use a Miller Syncrowave 250 DX with the added water-cooling unit. I am a self tought TIG welder with about 4 years of experience with mild steel, SS, alum, and even brass (not for anything structural on the brass, just lightweight aesthetic applications). I feel as if I've come along pretty well with my skills but at the moment i am stumped.(with my luck its something simple that I've overlooked, haha) Basically, when welding mild steel I am running into problems with porous, discolored welds. Currently I am welding 3/16" to 3/16" fillet at around 120-130 amps, gas flow (argon) at 20 cfh. Filler is ER70S-2. The problem is somewhat sporadic in that one tack may turn out shiny and colorful (which ive gathered is ideal?), and the next is dull and bluish gray. The dull ones sometimes instantly develop a tiiiiny crack right down the middle of the bead, so of course it is easily snapped off. Even when no visible crack develops the dull welds can be broken as well with a gentle tap from a hammer. Looking at the cross-section of a freshly snapped crap-weld, the filler area appears finely porous and dull in color. In my experiences this points to insufficient gas flow. As i said before I've had no technical training other than reading the owners manual to my machine and the awesome GTAW handbook that I picked up at my local welder supply store. Ive gone down the list of toubleshooting options for these characteristics and I'm at a loss. I have pretty much been through a lot of trial and error with gas flow rate, post flow rate, and also my machine is set properly to HF start, etc. I cant post any pics just yet but i hope to get them uploaded this evening. Whew, I think thats most of everything i wanted/needed to say. Any tips are much appreciated.

hartmetalworks

[H80N]

breeze??

are you maybe getting a sporadic breeze or gusts through the shop???

no cracks in the backcap? loose cup?

these are the first thing that I would look for.... sounds like something is disrupting your argon coverage....

[chart102]

i have no fan blowing on or near me. but all the factory doors being open does produce a SLIGHT puff of a breeze every now and then. but i even block those with my body when welding just in case. torch is fine except for a small crack in the outer handle (from what i can tell it does no sealing for anything). all the gas line connections are tight and in good shape. what im thinking is a possibility is that there is some minor kinkage somewhere along the whip or around the base of the torch handle that only rears its head when in certain positions. but what makes that not seem to be the case is that i specifically have gotten in the same position with 2 different results. My brain is melting.

[shovelon]

Leadloy?

[chart102]

I know how much TIG welding doesnt appreciate a breeze, but am I to take it that even the tinyest one can cause this?

[chart102]

Leadloy?

Ok here comes the lack of knowledge.......what? haha

[shovelon]

Ok here comes the lack of knowledge.......what? haha

Free machining steel with lead added increases machinabiliy, but welds poorly. Usually undercuts pretty bad, and cracks on sides and middle of the weld.

[Daniel]

I know how much TIG welding doesnt appreciate a breeze, but am I to take it that even the tinyest one can cause this?

Some times it's your gas line. I had problems like this with GMAW I'd press on the trigger and could hear the gas coming out, but once starting to weld sometimes I'd get porosity. New line and problem fixed.
Sometimes the gauge on the bottle wont give you correct reading, meaning what really is the pressure left in the bottle and flow coming out.
Porosity is caused by not to many factor.
- Dirty metal.
- Shielding problems

PS : dont forget millscale front and back of your joint can cause problems.

[jontheturboguy]

What size cup are you using?
How far out is your tungsten sticking out?
Are you running a gas lens?

[MMW]

Torch angle? Sometimes you don't realize your holding the torch at to much of an angle. Easy to do if making multiple tacks in a row. Sounds like gas issue but could also be scale on the material or in the joint & it's sucking it into the weld.

[Country Metals]

Is it good steel or is it made in china where the tin cans can still be seen? A lot of plate from china / india / wherever could have been made poorly.

If it is bad steel, change out to good material just to check. If it is working fine, quickly go back to the other plate and back and forth. That will tell you bad steel or not.

[Andy]

Is your base metal clean enough?

It doesn't take much breeze to blow the shielding gas away. Generally if you can feel a breeze it's too much.