FCAW-G using DCEN vs DCEP 1

[jays66amc]

There recently has been a project completed at my work and an issue has been brought up that I do not know how to proceed on. The welders had manufactured a large structure using Flux core with gas, it was Hobart Excel Arc 71 wire. But they had the machine set up in DCEN. With most of the heat being applied to the base material, do you feel like the penetration would be sufficient or is it something that the welds would need to be ground out and redone in DCEP or would a lack of fusion at the root be a concern. I understand an easy answer is scrap it but I am curious if there is a way to salvage it, if you feel like there even is much of a concern. Thanks for any of your insight on this.

 

[cloa]

You would need to specify as many parameters of the welds- geometry, welding parameters for anyone to estimate how much of mess you are in? Quality assurance checks..... Was it really all the welds in wrong setup?

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[david339933]

Polarity is a supp. ess. variable...for Sec. IX I see though that this wire is designed for DCEP.

 

[kingnero]

make a WPQR with the polarity and parameters used, and see if it passes all tests.
That would be my first step.

This way, you can show your client what happened, what the practical results are like, and whether or not he accepts this.

 

[metengr]

I would suspect you will have LOF weld defects. I agree you can attempt to simulate what was done and after the fact but I would bet less than a 50% chance of the client accepting it.

 

[jays66amc]

For parameters they had the machine setup at 22v 250ipm, apparently all positions. Material 1.5"x3"x.188"wall. QA was apparently self visual checks. And it sounds like 90% were dcen and once found started grinding and correcting the "ugly" welds.

 

[DekDee]

jays66amc,
What polarity was your PQR qualified with ?
What polarity were the welders qualified with ?
You mentioned a "structure" so there is a possibility you are working to AWS D1.1.
Change in polarity is an essential variable so if it is AWS D1.1 then none of the welds comply and you have a serious problem.
Good luck,
Regards,
DD

 

[jays66amc]

From what I understand is his pqr for fcaw-g was dcep and his fcaw-s was dcen. It is a structure but the dwg only says internal qualification required with a visual inspection. First time this company supplied our drawings. I'm thinking at this time they will become familiar with their grinders... I do appreciate your insight.

 

[gtaw]

The manufacturer lists DCEP. Who knows what the mechanical properties are when the wrong polarity is used? A test coupon welded with the parameters used during fabrication and subjected to the full regiment of NDE and mechanical testing will provide some insight to what can be expected of the production welds. However, who can say with any degree of certainty what parameters were used for the production welds?

Best regards - Al