Plasma Arc Welding Aluminum

Date 04-07-2009 19:31

Hello. I am using the variable polarity plasma arc welding process in an experiment to test the maximum thickness capability of the machine. I have some 0.380" 2219 aluminum plate and I was looking for the correct joint preparation procedure. Would this just be a square groove butt joint?

The 2nd joint is 0.500" 2219 aluminum. I have read that you can make a single pass weld using this VPPA process, but it's unclear to me as to how the joint should be prepared. Should I be using a v-groove joint design or square groove? If I need to v-groove it, how do I determine the correct root face, groove angle, etc.

Thanks.

By defaced (**)

Date 04-07-2009 19:55

If you put a groove in it, aren't you kind of defeating the purpose of your test? And if you have to put a groove in it, toss out the books and develop something that works. There generally aren't too many rules when you're developing a procedure.

I'd run it with a square butt until the machine starts to cry, then back off a little and say that's my max. If you're going to be using this in any form of high duty cycle scenario, then be mindful of the duty cycle and output ratings.

By OBEWAN

Date 04-07-2009 20:00

I agree and would say that it even defeats the purpose of the process. A V-groove would require filler. The advantage of a plasma keyhole weld is one pass with no filler. That means a square groove with a reasonably good fit-up.

By Lawrence (*****)

Date 04-07-2009 20:19

http://www.thefabricator.com/ArcWelding/ArcWelding_Article.cfm?ID=44

The welding journal has been periodically producing papers about Variable polarity PAW since about the mid-80's

You might try to look them up on the AWS.0rg website search.

By Zeek

Date 04-07-2009 20:30

Thanks for the advice. I've done some research on the web and there definitely is some useful information out there.

I read somewhere that when you are running in the keyhole mode of plasma welding, that you need a backup bar that is with or without purging and that the groove has to be deep enough so that it does not disturb the arc jet. If I'm running aluminum that doesn't need backside purging and I have tooling to hold the joint in place, what is the purpose of the backup bar? Is it only there to act as a chill or doest it have some sort of impact when operating in this keyhole mode?