I don't see the keyhole...

[stokestack]

Hi all. I'm a welding student, in my second quarter of class. The first was oxy-acetylene, during which I understood the "keyhole" technique.

Recently I had to do a butt joint on 3/8" steel, with angled edges and a 1/4" gap. I've read that even with MIG you're supposed to open up a keyhole; but even with experimentation I never saw any evidence that this would happen, because there's wire being pushed into the gap continuously. Is it realistic to open up a hole with this type of welding? If so, how does it occur when wire's being fed into the gap?

 

[stokestack]

Hm, where's the Edit button? I forgot to make it clear that I'm doing MIG now.

 

[Mark 2]

Well, I'll ask.
What is a/the keyhole technique?

 

[chrismac]

Well, I'll ask.
What is a/the keyhole technique?

The keyhole technique is when the straight/parallel prep opens up to a circle just where the arc is effectively looking like a keyhole in a door, if you have an imagination...

 

[tom2207]

yes , its a thing , you just need faith and a few practice goes where you dont mind the whole thing turning into a hole thing.
slow down and give the pool time to form well , its not so much of an actual keyhole , think of it more as a pear or a teardrop and you will soon get the hang of it , after gas ..mig is a cruise , but you need to get a good feel for your machine.

 

[chrismac]

Hi all. I'm a welding student, in my second quarter of class. The first was oxy-acetylene, during which I understood the "keyhole" technique.

Recently I had to do a butt joint on 3/8" steel, with angled edges and a 1/4" gap. I've read that even with MIG you're supposed to open up a keyhole; but even with experimentation I never saw any evidence that this would happen, because there's wire being pushed into the gap continuously. Is it realistic to open up a hole with this type of welding? If so, how does it occur when wire's being fed into the gap?

If your prep bevels are down to very near a point the root pass will burn/open up a little giving you a key hole, you need to voltage and wire speed set correct to achieve this though.

 

[Morrisman]

If your prep bevels are down to very near a point the root pass will burn/open up a little giving you a key hole, you need to voltage and wire speed set correct to achieve this though.

That’s usually just before a big hole appears….

 

[colnerov]

... followed by a lot of practice filling the hole in.

 

[zzr1200]

That’s usually just before a big hole appears….

Especially when your gas welding aluminium......