Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

GTAW process of Carpenter 20cb3

GTAW process of Carpenter 20cb3

GTAW process of Carpenter 20cb3

  I am welding 3/4" up tp 2" schedule 10 Carpenter 20 cb3 with ER320.  Does anyone have idea what the black specs of trash that form in the weld puddle and are left on top of the solidified weld are and how they form?

RE: GTAW process of Carpenter 20cb3

I have to admit that I haven't seen this problem before, so here is some general information that might prompt you (onsite) to identify the source of the problem.

A few items to check:
-    What gas is being used? Generally, 100% Argon is used with GTAW of Alloy20 (20Cb3)
-    Eliminate any contamination from grinders, i.e., get new grinding wheels (Aluminum Oxide not Silicon Carbide).
-    Use a large cup to dispense the gas over the area.
-       Use an Argon Purge on the backside of the weld.
-    Consider using E320LR  (Low Residuals).
-    Cleanliness is important, do not use crayons to mark.

Here is a link to the Technical Data BLUE SHEET from Allegheny Ludlum Corporation  Pittsburgh, PA for Alloy 20 http://www.alleghenyludlum.com/ludlum/pages/products/pdf/al20.pdf

RE: GTAW process of Carpenter 20cb3

Thank you for your reply.  We have been doing everything you have mentioned above except using the low residual filler material.  I think that the low residual filler material helps with the hot cracking situations.  I have also already read the Blue Sheet on this material and I could not find anything pertaining to this.  I only notice this on small diameter thin sections of pipe not on the thicker sections which leads me to believe it is caused by heat but still not sure.  Thank you very much for your suggestions.

RE: GTAW process of Carpenter 20cb3

Here is a few other ideas. You have me stumped. I have used the alloy many times, from small diameter sch 5 pipe up through 12" sch 120 pipe without problems except for the occasional crater crack.

- Nickel Oxide is black in color. Could the welder be using too much Gas and creating turbulence, hence pulling oxygen into the weld pool?  
- Does the Black material react to Nitric acid? (Check for Iron)

- Have you carefully ground out the defect. Is it all on the surface is dispersed throughout?

- If you can get a sample of the black material is it magnetic?

- Take a sample of the black material and put in in a small vial add household ammonia (small amount), shake, doe the ammonia change color? what color? If it turns blue (Royal Blue)it is probally a copper compound.

I wish I had a better answer. It concerns me that it is forming in the weld puddle.  


RE: GTAW process of Carpenter 20cb3

If the "trash" is visible only after cooling, It may be excessive heat input.

If it forms while welding I'd think it is foreign material.

3/4" Schedule 10 would be pretty tough to weld and control heat input.

Have a good day

G Austin

RE: GTAW process of Carpenter 20cb3

I realy appreciate your help guys!  Rich I will try your ideas they are great!  I will check the gas flow on the tig torch it should not be anymore than about thirty or so but I will check it out.  G.Austin I can see it in the puddle as I am welding so I am still stumped.  Everything is extremely clean, I even sand my filler wire, and your right it is extremely hard to control heat input on the very small diameters.  It is not a major problem just a little aggravating, I am a bit of a perfectionist. If you all can think of anything else let me know.  Once again thank you all very much for your time and knowledge.


RE: GTAW process of Carpenter 20cb3

Do you wipe off the wire after sanding. The silica could be a cause.

G Austin

RE: GTAW process of Carpenter 20cb3

Try using a different heat number of filler and if that doesn't change the condition, change the heat number of the pipe.

"There's no such thing as a welding problem, just welding puzzles of assorted sizes!"

RE: GTAW process of Carpenter 20cb3

Oops, I forgot to mention this in my previous reply as a possibility.  

Your description of "black" specks could be construed as a chrome oxide that exhibits itself on the puddle surface in the P4x's when using too high of heat input.  I've observed & experienced this phenomenon and have been actually able to move the oxide around on the molten puddle similar to a jumble of sticks with the tip of my filler rod.  Though when the puddle is solidified, I personally can't describe the condition as exactly "black specks" but I could understand why somebody might describe them as such.

"There's no such thing as a welding problem, just welding puzzles of assorted sizes!"

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close