using DCSP for E6010 root pass

Date 05-08-2003 13:10

I’ve seen in catalogue of OERLICON Co. and BOHLER Co. that is recommended to weld root pass by E6010 electrode and DC NEGATIVE and balance by DC POSITIVE. As I know cellulosic electrode can be welded just by DC positive.
May somebody tell me why it’s recommended to use DC negative for root pass?

By JTMcC

Date 05-08-2003 14:01

DC + is normally used in the U.S. Other places DC - is more common. DC - melts off rod faster and travel speed is higher. Hollow bead defects and internal undercut are less likely with DC -. DC - will also help with burn thru on thin wall pipe.

JTMcC.

By George-kh (**)

Date 05-08-2003 16:15

Thank you for your reply.
You’ve explained about benefits of DC negative. But please consider that first, according to AWS classification it’s not allowed to use DC negative for E6010 and second, in catalogues of these companies it’s recommended to use DC negative JUST for root pass.

By sayeeprasad (*)

Date 05-12-2003 10:46

DC -ve means that ~1/3rd heat of arc as a thumb rule is concentrated on the electrode. So I would rather expect that the melting rate is lower. Thats the reason why DCEN is used for GTAW, to prevent heating up of the Tungsten electrode. At the same time I do agree that the weld bead being smaller and the control better, generally a much better root profile is achievable using DCEN for root with cellulosic electrodes. Though the classification specifies that E6010 is to be used with DCEP, the manufacturer recommends DCEN to be used, and on this basis we have been able to conbvince client(s) and use accordingly.

By JTMcC

Date 05-12-2003 16:07

In spite of what you would expect, the melt off rate is higher in actual experience, mine and others. Lincoln confirms this as well. In the US, negative beads are commonly used when the bead hands are trying to increase production, you really can truck down the side of the pipe but don't get caught.

JTMcC.