The choice of polarity is generally not determined by the base metal but by the process or process parameters. For SMAW the choice of electrode will often dictate the optimum polarity. Polarity issues/selection for various processes are discussed in the ASM Handbook, Volume 6, the AWS Welding Handbook, Volume 2, or many basic welding text books.
One exception would be materials that develop a very tenacious, fast reforming, refractory oxide layer such as aluminum. In that case, AC is often preferred for some processes, such as GTAW. The alternating current helps to break and lift off the oxide layer.
John A. Henning
Welding & Materials
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Sinadurai Sripadmanaban
Sent: Thursday, June 20, 2013 8:14 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:17989] RE: 17965] Clarification on Current and Polarity Abbreviations
Please give a list of metals & other items including stainless steel for which +ve to be connected to electrode as well as for which metal -ve to be connected to electrode.
Sinnadurai.S
On Tue, Jun 18, 2013 at 11:12 PM, John Henning <jhenning@deltak.com> wrote:
As I understand from welding people even older than I; in the beginning days of welding, DC welding was performed with direct current power supplies with the electrode being the negative pole. As welding progressed some, people found that SMAW welding with cellulosic coverings “ran” better with the electrode positive or “reverse” polarity. This may be a true story or it may just be propagated mythology. At any rate -
For basic welding you can have an alternating current (AC) power supply or a direct current (DC) power supply. With DC you have two options: (1) electrode as the negative pole and the work piece the positive pole or (2) electrode as the positive pole and the work as the negative pole.
DC straight polarity (DCSP) is the same as DC electrode negative (DCEN). There may also be non-standard designations such as DC-, or DC-VE.
DC reverse polarity (DCRP) is the same as DC electrode positive (DCEP). Or similar to above, non-standard DC+, or DC+VE.
Hope this helps.
John A. Henning
Welding & Materials
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Anban
Sent: Tuesday, June 18, 2013 4:47 AM
To: materials-welding@googlegroups.com
Subject: [MW:17965] Clarification on Current and Polarity Abbreviations
Dear Experts
Pls enlighten me if thse abbr. are same and explain the correlation and difference
1 - DCEP x DC+VE x DCSP
2 - DCEN x DC-VE x DCRP
DCEP - Direct Curent Electrode Positive
DCSP - Direct Current Straight Polarity
DCRP - Direct Current Reverse Polarity
Appreciation in advance
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