what did I do wrong ? bad weld

[mikeyr]

I had to weld up a plate, 1/8" thick to make is shorter, I did this with my MIG and it looked good but when I ground down the weld it was full of holes, its the first time its happened to me. I ground it all out and this time TIG'd it so its good now and not worried about it falling apart, but wondering what i did wrong. This is a front plate on a motor so it holds the motor mounts, i needed to cut 3" off the side to center the motor in the frame (not original motor).

 

[AldeanFan]

How clean was the metal?
We’re you using gas or flux wire?

 

[Bucko]

Almost looks like a gas mig setup and the gas was off or empty.

 

[G-ManBart]

Sure looks like a gas coverage issue. Any fans/heat vents pointing at where you were welding? Did you ensure proper gas flow before starting? For some reason I also see a lot of people use the same CFH for MIG that they do for TIG and that's wrong...MIG should be approximately twice what you use for TIG. When in doubt, try 25CFH...it's usually enough, but not way too much.

 

[imagineer]

Probably just not cleaned well enough.

In December, I was welding some pieces of 8" square x 3/8" wall steel tube to make a section of 8" x 6.75" rectangle tube and ended up making the worst welds I'd ever done. Horrible porosity. I checked all my set ups and shielding gas, ground out the welds and made another attempt. A little better but still full of porosity.

Discouraged, I decided to go inside for a cup of coffee to think through what might be the problem. In the house, my wife asked if I'd been using WD-40 on something. Turns out, it was on the rag in my back pocket. The same rag I used to wipe down the steel before welding.
Apparently it was so cold out in my workshop, I didn't feel or smell that the rag was soaked in WD-40; and was basically oiling the metal right before welding.

 

[slowtwitch73]

Holes= gas problem, contaminates, laser or plasma cut edges that haven't been 'taken back' to unaffected metal.

 

[Bodj Built]

Is your mig wire rusty? Could also be bad batch of gas, hole in your liner (so you have less gas flow at the nozzle)...

 

[MoonRise]

google-fu on "mig porosity problem" returned 588,000 results in 0.54 seconds.

Some selected results:

https://www.millerwelds.com/resources/article-library/troubleshooting-weld-defects#:~:text=Porosity%2C%20one%20of%20the%20most,flow%2C%20increasing%20it%20as%20necessary.

Porosity in Welding - Defects / Imperfections in Welds

The characteristic features and principal causes of porosity imperfections are described. Best practice guidelines are given so welders can minimise porosity risk during fabrication

www.twi-global.com

22 possible causes for porosity in welding

Porosity in welding is a common defect that is fairly easy to fix. What issues contribute to weld porosity? Read our checklist to learn what the problem may be.

www.thefabricator.com

Porosity in Welding - Defects / Imperfections in Welds

The characteristic features and principal causes of porosity imperfections are described. Best practice guidelines are given so welders can minimise porosity risk during fabrication

www.twi-global.com

MIG Problems and Remedies

MIG Problems and Remedies

www.lincolnelectric.com

summary: MIG porosity problems are usually caused by improper prep aka poor cleaning, or shielding gas problems (too low of a flow rate, too high of a flow rate, gas line problem, gas cylinder problem like running low or out or rarely contaminated gas cylinder, draft, gun/nozzle positioning/angle, crudded up nozzle or gas diffuser, bad o-ring in the gas line connection, not fully seated gun cable connection to the machine that maybe got yanked a little hard and is now leaking, gas regulator problem, etc).

 

[mikeyr]

well the thing was plasma cut but i thought i went back into good metal before welding. I can't imagine not noticing that the gas was off, its usually instataneous "oh ****" when I forget to turn it on. I do wonder if something was wrong with my MIG wire since I did have some issues getting a good weld with the TIG yesterday, had to grind in pretty deep to get rid of the bubbles and they were only on the last inch or so, implying I had gas since the first part of the weld was good. When I get home i will check out my MIG and see if I find anything odd with it. I do prefer to TIG anyway and even was going to get rid of the MIG then i had to do a floorboard replacement and the MIG was so much quicker that I kept it. Funny, I have been welding for 20-25 years and never ran into this before. Thanks for comments.

 

[oscar1953]

I had a similar experience with porosity in my welds. What I found was the gun/stinger had pulled out of the machine slightly causing gas leaking around the o rings.
Reseated the stinger Problem solved

 

[Bigblue&Goldie]

My buddy was struggling with his tig welder for a long time. I was trying to dial it in with inconsistent results. It turns out the gas hose had cracked and depending on how it was bent determined how much gas was escaping.

 

[bb29510]

you lost your gas