Welding Tips and Tricks

Welding cold rolled steel sheet and even though I ground clean and wiped with mineral spirits had a few points that had contamination and a bit of pitting or porosity. Managed to go back over with filler. But is frustrating. Am I not grinding enough of the mill scale off of the material? I had it to shiny metal. Another tip needed to clean and prep better.

To be honest, I hardly prep cold rolled at all. The scale is usually trivial enough to get dealt with by the additives in the fill rod and they are almost always going to get painted over anyway. Pictures would probably help but that sounds like a shielding issue. What are you using as a flow rate and with what size and type of cup? Any chance it it getting hit with a bit of a breeze?

-Sandow

If you are getting bubbling/porosity, then there is a problem with gas shielding, which could be many many things. What have you checked?

I don't think mineral spirits would be a good metal cleaner, kind of an oily product that might be penetrating your steel and causing your problems. You need to use something that evaporates without leaving a residue like acetone. or even lacquer thinner in a pinch. Where I get my sheet steel, they apply a thin coat of oil to prevent rust and this coating needs to be removed before grinding off the mill scale, otherwise the grinder kind of forces it into the steel. Try a good wipedown with acetone on a clean rag.

I use a #6 gas lense 1/16 inch tungsten on 16 gauge 40 amp max (pedal control) and 18-20 cfh on argon.

What I have is a sparkle occur, then a crater pops on to surface. Almost like shield drops out, but then can go several inches with no issue. Glass cup screen is new, about an hour on it now.

I wonder if like mentioned using thinner instead of brake cleaner or acetone is an issue. I grind then clean so you may be on to something by saying I could be grinding and embedding contaminants, and should clean grind and clean a second time, with acetone or a chlorine free brake cleaner.

NEVER USE BRAKE CLEANER!

Sometimes a full penetration weld on thin material will draw impurities in from the back side of the puddle. On flat sheets you can limit this with a backing plate.

Len

sedanman wrote:NEVER USE BRAKE CLEANER!

Its the chlorine that causes the bad gas/posion
Note he said
"chlorine free brake cleaner."
and yes it is chlorine free and doesn't clean for "sh*%"

Okay so may need to clean with acetone before and after grinding clean. I use a #6 gas lense and 20 CFH so I am comfortable with shielding. I was holding temperature back to avoid sugaring the backside in this case and it was minimal for sure. No brake cleaner got it.

This was the second similar part I welded and the first went very nicely in one pass no issues, and prepped same way. Got lucky I guess.

Braehill wrote:Sometimes a full penetration weld on thin material will draw impurities in from the back side of the puddle. On flat sheets you can limit this with a backing plate.

Len

I may have overlooked cleaning backside good point.

I err on the side of caution when there is potential for neurological injury.

For what it is worth, phosgene is transient in effects so if it doesn't kill you it doesn't really screw you up.

Personally I like chlorine free brake cleaner prior to welding simply because you can push contaminants off the end of a part. I'll use acetone and MEK too but I really don't see a huge performance difference between them all.

Regardless, this still sounds like a shielding gas issue an not a cleaning problem. Your flow rates seem fine and if it is mostly ok while you weld, it means that there is a problem that is either transient like a breeze blowing your gas away or there is something intermittent going on with your gas flow. Could be a crack in a line that opens up when you flex the torch a particular way. Could be that your gas line is getting kinked shut. I think it is going to be something like that. I'd do a soapy water test along your lines and fittings.

-Sandow

Phosgene has a cumulative effect on sterility. If that's not screwing you up I don't know what is...

Coldman wrote:Phosgene has a cumulative effect on sterility. If that's not screwing you up I don't know what is...

That isn't what the msds or the toxicology books say. Where are you getting that from?

-Sandow

Had that drummed into me in two places. 1st was in the army nbc training and second in college for refrigeration trade because many of the synthetic refrigerants degrade to phosgene in the presence of a flame.

But if is a shielding gas leak or interruption issue why is it not an issue on all my other welding I do on other materials. Could see an intermittent breeze though. My entire welder and torch and all associated parts are less than 6 weeks old.

Let's back up! Is there a pic of the porosity you speak of? There are many possibilities or contributing factors. One hole in a few inches of weld is likely abnormal contamination. Many small holes is maby a gas or severe metal contamination. How many holes per inch of weld?

Sorry no pictures. But is about 3-5 small holes in a 1/2 inch that once cool I went over with filler and buried basically. Not a structural weld by any means. I really think some sort of residue was drawn into the puddle. I plan to buy some acetone or MEK and try this from now on and leave the paint thinner on the shelf.

bruce991 wrote:Sorry no pictures. But is about 3-5 small holes in a 1/2 inch that once cool I went over with filler and buried basically. Not a structural weld by any means. I really think some sort of residue was drawn into the puddle. I plan to buy some acetone or MEK and try this from now on and leave the paint thinner on the shelf.

Bruce, be sure to have the proper chemical resistant gloves when using acetone or MEK

It could very well be some kind of contamination, but until you replicate the issue, once you change variables, you might not know what the culprit is.

I find that too small a gas shroud can cause swirling and draw air in. Also the stickout distance of a normal shroud and collet body must be as small as possible as this can draw air in. Mild steel is a lot more sensitive to porosity, so a tiny gas leak can cause hurry curry.

Mick

Well I have been busy welding and have had no repeat issue

I am not a professional welder, but I am going to add my 2 cents. My problem, after experiencing something like you described, was contamination AND I am convinced it was something in the specific old steel I was welding (deep imbedded rust or something). It would be interesting to try another sample and see if the same result occurs. I don't know how big of an item you were welding so this is only a thought on my part. What type of weld was it, lap, joint,… I didn't do a good job cleaning the edge of a joint weld and got excellent contamination, the surface was cleaned ok, but it didn't matter.

HitMissTom wrote:I am not a professional welder, but I am going to add my 2 cents. My problem, after experiencing something like you described, was contamination AND I am convinced it was something in the specific old steel I was welding (deep imbedded rust or something). It would be interesting to try another sample and see if the same result occurs. I don't know how big of an item you were welding so this is only a thought on my part. What type of weld was it, lap, joint,… I didn't do a good job cleaning the edge of a joint weld and got excellent contamination, the surface was cleaned ok, but it didn't matter.

I was welding 16 gauge 11 inches long using no filler. Outside of a 135 degree joint. Moving fast as to prevent backside sugaring. In the picture was the top edge you see there on the part.

What I would try (experiment?) is to make some sort of argon dam under the V and apply some purging to it (maybe heavy aluminum foil if the heat can be controlled). Also, the argon cfh should be reduced about 25% on corner and edge welds (probably heard that on a Weldmonger video).