DC welding

[Genetix]

Hi respected welding engineers.

In SMAW DC welding:
DCEN = shallow penetration
DCEP = deep penetration

IN GTAW
DCEN = deep penetration
DCEP = shallow penetration

Can someone explain why DC polarity effect is different for SMAW and TIG.
Thank you very much.

 

[kingnero]

For GTAW, it's especially important not to overheat the W electrode. As it is on the (-) side, electrons "leave" the W electrode (the jump requires energy) and "bash" into the base metal with a very high speed => deep penetration.

For stick welding, it is not always true what you say. most basic rods require DCEP polarisation, having a better penetration. Rods made for DC- welding will also have good penetration.
The elements in the coating help with this. Further do you have active metal transfer inbetween the electrode and the base metal, whereas you do not have this in GTAW welding.

Typically, the positive side will be the hottest side as that's where the electrons bash into. In SMAW and GMAW, this heat is used to melt the electrode down.
And then there's still something with the Lorentz force on the liquid metal droplets, which help to accelerate these particles towards the cathode (-) side.

http://www.fusionpoint.be

http://be.linkedin.com/in/fusionpoint

 

[metengr]

http://www.lincolnelectric.com/en-u...eory/Pages/understanding-polarity-detail.aspx

http://www.lincolnelectric.com/en-us/support/welding-solutions/Pages/polarity-for-smaw.aspx