Not Gonna Show You the Pictures

I was soldering all around some RF filter cans shortly after taking a welding class, and for fun tried to duplicate that look. It was easy to do with solder by moving the puddle forward and back with the iron, or by dipping more solder in the puddle to cool it. That might be a good way to practice since you can see what you are doing so much more easily.

Jim Wilkins

ROFL. I sure been there and done that.

I had to read your reply three times, because I sure there was a seed of actual advice in there.

My experience with aluminum is that it is hot short. When you have enough on there for it to be right, it all drops in one big globule onto the floor.

Steve

Go longer?

-- Peter

Advice: when welding aluminum, pay attention to hot shortness. Other than that, can't give you a lot of info on aluminum.

Steve

Sorry, I'm really bad at asking questions these days. What does that mean?

I believe it means that aluminum with it's high thermal conductivity and relatively low melting point is counter intuitive - you have to hit it with high welding power (amp or volt depending on process) to melt the weld puddle fast and get the weld done quickly before the weld puddle grows and consumes the entire piece. i.e. hot and short (quick).

Hot-Shortness refers to a metal that loses cohesion rapidly above a temperature where similar metals are unaffected.

Most modern complex tool-steels suffer from hot-shortness. It makes it difficult to use them in blacksmithing . You get above a specific temperature and they fall apart into glowing cottage cheese.

With aluminum this isn't really hot-shortness. Aluminum just has a low melting temp and a high thermal conductivity. With melting temperatures around 1200 DegF, it is very easy to hit the melting point on smaller pieces. Large aluminum structures don't suffer from this since the additional material with almost always drain off enough heat to prevent excessive melting.

Smaller aluminum parts just have to be monitored for heat as you weld. You have to reduce your heat input as the part gets hotter. You can monitor the heat using simple indicators like Tempilaq, or Tempilsticks.

Hot shortness is a welding and metallurgical term which applies particularly to aluminum. When the metal reaches its melting point, it has the tendency to collapse under its own weight. If you google it, it has heavy references to sulfur content in steel or wrought iron which causes brittleness. I remember it from learning about aluminum because the words are so uncommon.

Basically, it means that you have to watch the size of the puddle when doing aluminum, or it all falls on the floor.

Ernie, can you help me out a little here? I didn't realize that it applied to so many different metals. I thought it was only aluminum.

Steve

Ayup....when I first welded Aluminum..I used the "creep up on it" method....slowly add heat until it started to get "that look"..and had the entire thing turn to slush and wind up splashing all over my welding table, with me madly semi sucessfully dodging the splattering molton aluminum.

Now when I tig, I set up the start current to full balls to the wall for the material, and hit it fast, add my filler and get back out.

Gunner

--Hey Ernie I went to the tempil site; would you recommend the paint sticks or the noncontact probe for this sort of thing. What I can't figure out is how you'd "read" either way while you've got a welding mask on..

tered.motzarella.org...

Definition of =93hot-short=94 in metallurgy:

I recently came across the website of an interesting guy who designed and built his own submarine using 5000 series aluminum. He has tips on MIG welding aluminum:

Tempilaq is good for monitoring a slow rising heat. Tempilsticks are really easy to use and are great for weld preheats. Infrared thermometers are quick, but you have to be careful about beam spread, and distance.