Welding Basics: Techniques for Tig, Mig & Arc Welds : Welding Troubleshooting

Welding Basics: Techniques for Tig, Mig & Arc Welds : Welding Troubleshooting


Hello! My name is Mac and on behalf of expertvillage.com
I am here to discuss MIG welding. Today I would like to talk to you about weld defects.
Now there are a number of weld defects that can cause a weld to fail. There is porosity,
cold lap, cracking, burn through; there are any number of these things that can occur,
lack of fusion is other one for instance. Of the different types of weld defects probably
one of the most common is a situation called porosity, and it occurs when the gas coverage
on the weld from the inert gas is not inadequate and oxygen gets at the weld and causes it
to bubble or be full of little gas pockets that look like bubbles. This can be caused
by a number of things and normally it is some kind of stray air movement. For instance,
an overhead ceiling fan or unit heater blowing downwards can blow your gas coverage away,
someone can open a door or a window and let in a breeze or you can get porosity from welding
over paint or on wet steel for instance. A lot of welders make the mistake of thinking
that the porosity is caused by not having enough gas. In the case of porosity, if the
welder goes to his regulator and starts to turn up his gas pressure and you know the
old saying about if a little bit is good then a whole lot must be better, is not always
the case. What can happen is, the gas pressure can get so high that as it exits the gun the
velocity is so great that it begins to cause a Venturi effect. The gas flowing forward
at a very high rated of speed begins to draw air in around the edge of the cup the air
deludes the shielding gas introduces nitrogen and oxygen into the weld puddle and contaminates
with porosity. So if you are having porosity problems look somewhere else first. Solve
all of the air infiltration problems, of forklifts driving by very quickly creating a breeze,
open windows and doors, fans running close by, unit heaters and things like that. They
are more than likely the cause of your porosity. The another cause of weld failure is cracks
and sometimes the cracks occur simply by welding on steel that is too cold or chilled. The
manufacturers of the welding wire will not guarantee the quality of the welds if you
weld on steel in ambient temperatures below 50 degrees Fahrenheit. So if the weld is fairly
cool, you can get cracks. The weld puddle cools off far too quickly.

10 thoughts on “Welding Basics: Techniques for Tig, Mig & Arc Welds : Welding Troubleshooting

  1. This bloke reminds me of a guy I know. He's been welding pipe for 51 yrs.I'm thinking of chopping and dropping a beach cruiser.I think i'll give him a shout.

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