Re: [MW:6575] Conflict about heat available on electrode/work for the SMAW & GTAW process even having same polarity

CK,

 

In case of thermionic cathodes, tungsten is Very good emitter than any metal. (Work Function =4.5eV, First Ionization Potential = 8.1 V)

GTAW-DCEN= Electrons emitted (at High temperature) from the cathode and majority of heat concentrated on the work through arc column, which in turns 2/3 heat at work

 

In case of non-thermionic electrodes, temperature required to for thermionic emission is low.

 

Electron emission is through the oxide films , by setting up the electromagnetic field though oxide

 

SMAW-DCEN= Due strong electromagnetic field through the oxide , 2/3 of heat is concentrating the at electode itself, and emission is occurring at low temperature. (It assumed , only 20% of Cathode heat is concentrated at work)

 

But ,results in shallow penetration due to the melt of rate of consumable is high. Because of this reason, this polarity may utilized for the single pass welding (ie E6022 ) applications.

 

Hope  it is clear.

 

If any thing wrong, pls let me know.

 

Regards,

 

K.Babu

Singapore

 

----- Original Message -----

From: Chaitanya Purohit

To: materials-welding@googlegroups.com

Sent: Wednesday, August 18, 2010 6:45 PM

Subject: Re: [MW:6560] Conflict about heat available on electrode/work for the SMAW & GTAW process even having same polarity

Can you please elaborate for the benefit of whole group as all the people will not have the opportunity to look into the ASM handbook...seldom used at site.

Regards.
CK

On 18 August 2010 10:36, Kathalingam Babu <kathalingam.qaqc@ppl.com.sg> wrote:

Maulik,

It is not the conflict.

Pls understand the difference between the Thermionic & Non-Thermionic cathodes,

That will explains the heat distribution. Pls go through the topic of Arc Physics in ASM Welding Handbooks

Rgds,

K.Babu
Singapore


----- Original Message ----- From: "MAULIK" <mlkthakkar2@gmail.com>
To: "Materials & Welding" <materials-welding@googlegroups.com>
Cc: <bhavesh.patel@isgec.com>
Sent: Wednesday, August 18, 2010 1:47 AM
Subject: [MW:6549] Conflict about heat available on electrode/work for the SMAW & GTAW process even having same polarity

Dear all,


1. For SMAW-DCEN-2/3 heat to the electrode.

2. For GTAW-DCEN-2/3 heat to the work.

Why this is conflict?
Theoretically more heat is produced where the bombardment of electrons
is carried out.
Please give me clarification justification with proper evidence.

Regards,
Maulik H. Thakkar
Welding engineer

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