root pass/aluminum

By IRV Date 03-18-2001 00:39

I've been having problems trying to understand welding alum.When I get done with the root pass and look at it man it looks terrible.It's about1/4" wide but it looks like it has a crack in it.When I grind it out to make it flush there is no evidence of a crack .I'm using TIG process open-but.Mostly on sch10 but sometimessch40.I've tried to gap it 16th and add rod and tried to fuse it both processes I have to add rod.The root is there but it is thick and the indent in the middle any help I would be very thankful R

By Marc A Brach (*)

Date 03-19-2001 14:38

Sounds to me like a shielding problem. Are you sheilding the backside of the joint? You need to shield the backside/penetration. Either using a backer or by filling the pipe with shielding gas. Not sure exactly what to tell you to do as I am no expert on the subject but it sounds like this is the problem. If you give more specifics people will be able to give you a more specific answer. I have seen and recieved great advice from the people that visit this board and have learned that by leaving out a single variable can change everything. Good Luck!
Marc

By IRV Date 03-20-2001 02:46

I contacted hobart they said that a sheilding was was not required is that true or false?I'm not sure what other specs. to give you what do you need?But I'll try the purge next time thankyou for your time.

By Dirk

Date 03-21-2001 23:13

The problem is you will have a very difficult time doing this with GTAW open root.

Typically the "extended land" or J prep is employed which is similar to that used for "orbital" or mechanized GTAW welding.

There is no root gap employed and back side purging will make or break you.

Does the weld appear (on the ID) dull grey with a fish bone type pattern forming what appears to be a crack at the weld centerline???