AFFECT POLARITY IN HEAT INPUT

[Ali Asghari]

Hi All

all know that heat input is independent from polarity.but  i see in GTAW that in DCEN ,70%HEAT generated in arc concentrated in parent metal & in DCEP 30% HEAT concentrated in base metal.

can anybody clarify it?

regards.

[Darcy Morin]

The current-carrying capacity of the tungsten electrode is tremendously reduced at DCEP.  A 6mm diameter electrode can carry about 125 amps on DCEP. Whereas, a 1.6mm electrode can carry 125 amps on DCEN.

  

On DCEP, more heat is released at the electrode this causing the 'balling-up' effect and consequent consumption of the tungsten.

Thank you,

Darcy  

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[george....@gr.bureauveritas.com]

It is because of the difference of the electrons flow I think

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  From: Ali Asghari [asgha...@rocketmail.com]
  Sent: 11/02/2010 23:44 PST
  To: material...@googlegroups.com
  Subject: [MW:4291] AFFECT POLARITY IN HEAT INPUT

Hi All

all know that heat input is independent from polarity.but  i see in GTAW that in DCEN ,70%HEAT generated in arc concentrated in parent metal & in DCEP 30% HEAT concentrated in base metal.

can anybody clarify it?

regards.

[ali asghari]

thank you

but my inyention is distribution of heat is differed by polarity , therefore H.I depend to polarity.is it true?

regards

[Endri Prasetyo]

Agree with George. At DCEP the electrone will flow from tungsten to base metal and at DCEN will flow from base metal to tungsten. This electron flow will affect to the penetration.

Regards,
Endri

Sent from my BlackBerry®

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From: george....@gr.bureauveritas.com

Date: Fri, 12 Feb 2010 23:34:31 +0100

To: materials-welding<material...@googlegroups.com>

Subject: Re: [MW:4294] AFFECT POLARITY IN HEAT INPUT

[Darcy Morin]

The formula for determining heat input has the following variables: Amperage, Voltage, Distance and Time.  AxVx60/Inches per Minute. Polarity is not considered in the heat input calculation.

[george....@gr.bureauveritas.com]

Yes because when the electrons flow to the electrode the base metal is heated less

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[Chaitanya Purohit]

Dear All,

What I guess is the Question what Ali is asking was not understood properly by the group. He want confirmation that the Polarity will change the heat input or Not ?

Answer is in your Question Ali "heat input is independent from polarity" 

Now coming to your doubt on the statement you read somewhere where the percentage of Heat generated at Positive or negetive pole.... It is not only in GTAW but its applicable to all the Welding proces.

Please understand that the staement shows the distribution of total heat generated (100%) between the Electrdoe and Base Metal where the distribution of heat is always 70% on positve pole and 30% on negetive pole (again this % is approximate only). If you reverse the polarity % distribution between electrdoe and Base metal will interchange but total will remain 100%. .

Hope this suffice your doubt.

Regards.
C. K. Purohit
Eng-Tech Weld1
Sr Welding Inspector

[Singh Rishi (TIPO - QA/QC)]

If one checks the heat input formula, there is no variable for the polarity.

 Therefore , as per standard,  Polarity  doesn’t influence the H.I .

 

 We all understand that actual H.I differs from calculated  H.I as current / voltage/ travel speed are never a single value ( specially in manual welding )

Best Regards,

Rishi Raj Singh

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From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of ali asghari
Sent: Saturday, February 13, 2010 9:59 AM
To: material...@googlegroups.com
Subject: Re: [MW:4297] AFFECT POLARITY IN HEAT INPUT

 

thank you

but my inyention is distribution of heat is differed by polarity , therefore H.I depend to polarity.is it true?

regards

On Sat, Feb 13, 2010 at 2:04 AM, <george....@gr.bureauveritas.com> wrote:

It is because of the difference of the electrons flow I think

---

  From: Ali Asghari [asgha...@rocketmail.com]
  Sent: 11/02/2010 23:44 PST
  To: material...@googlegroups.com
  Subject: [MW:4291] AFFECT POLARITY IN HEAT INPUT

 

Hi All

all know that heat input is independent from polarity.but  i see in GTAW that in DCEN ,70%HEAT generated in arc concentrated in parent metal & in DCEP 30% HEAT concentrated in base metal.

can anybody clarify it?

regards.

 

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[John Henning]

The Code recognises that a change in polarity will affect heat input.  Thats why Sc IX assigns a change in polarity, QW-409.4 is a supplementary essential variable, and any change in polarity must be requalified with a new PQR.  Without impacts QW-409.4 is a non-essential variable and must only be appropriately addressed on the WPS.

 

John

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From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Singh Rishi (TIPO - QA/QC)
Sent: Sunday, February 14, 2010 11:40 PM
To: material...@googlegroups.com
Subject: RE: [MW:4314] AFFECT POLARITY IN HEAT INPUT

[sreedhar ch]

A little notes.... that i remember

current will flow from the negative side of the voltage source, through the resistor, and then to the positive side of the voltage source. This is exactly how a welding circuit works. Current flows from the negative side of the welder, through the arc, and then back to the positive side of the welder. A  effect of this is that more heat goes in the direction of current flow–Approximately 2/3rds of the heat will go to the positive side of the circuit.So if you’ve got your electrode hooked up to the negative terminal of the welder, (DCEN-DC electrode negative), approximately 2/3rds of the heat will be put into the workpiece.The opposite is true for (DCEP), 2/3rds of the heat will be biased towards the electrode.
This is how the Heat input varies.

 

Regards

Chitturi

[rupesy]

I think what is missing in the discussion is that the amps, volts and
travel speeds will need to be adjusted to run an acceptable bead in
either DCEP and DCEN. This change in variables will cause your heat
input to change. If you force the amps, volts and travel speed to be
the same for both polaritys, your heat input will be the same,
however, the quality of your weld may not be acceptable. That is also
why the code recognizes this change as an essential when impacts are
required. You will most likely need to change your amps, volts, and
travel to run acceptable beads in either polarity.

Any thoughts?

> On Sat, Feb 13, 2010 at 2:04 AM, <george.dilin...@gr.bureauveritas.com>

> wrote:
>
> It is because of the difference of the electrons flow I think
>
> ________________________________
>

>   From: Ali Asghari [asghari...@rocketmail.com]
>   Sent: 11/02/2010 23:44 PST
>   To: material...@googlegroups.com
>   Subject: [MW:4291] AFFECT POLARITY IN HEAT INPUT
>
> Hi All
>
> all know that heat input is independent from polarity.but  i see in GTAW
> that in DCEN ,70%HEAT generated in arc concentrated in parent metal & in
> DCEP 30% HEAT concentrated in base metal.
>
> can anybody clarify it?
>
> regards.
>
> --
> To post to this group, send email to material...@googlegroups.com
> To unsubscribe from this group, send email to
> materials-weld...@googlegroups.com

> For more options, visit this group's bolg athttp://materials-welding.blogspot.com/

> The views expressed/exchnaged in this group are members personel views
> and meant for educational purposes only, Users must take their own
> decisions w.r.t. applicable code/standard/contract documents.
>
> --
> To post to this group, send email to material...@googlegroups.com
> To unsubscribe from this group, send email to
> materials-weld...@googlegroups.com

> For more options, visit this group's bolg athttp://materials-welding.blogspot.com/

> The views expressed/exchnaged in this group are members personel views
> and meant for educational purposes only, Users must take their own
> decisions w.r.t. applicable code/standard/contract documents.
>
> --
> To post to this group, send email to material...@googlegroups.com
> To unsubscribe from this group, send email to
> materials-weld...@googlegroups.com

> For more options, visit this group's bolg athttp://materials-welding.blogspot.com/

> The views expressed/exchnaged in this group are members personel views
> and meant for educational purposes only, Users must take their own
> decisions w.r.t. applicable code/standard/contract documents.
>
> --
> To post to this group, send email to material...@googlegroups.com
> To unsubscribe from this group, send email to
> materials-weld...@googlegroups.com

> For more options, visit this group's bolg athttp://materials-welding.blogspot.com/

[Darcy Morin]

The current carrying capacity of the tungsten electrode is tremendously
reduced @ DCEP (10% of DCEN)...In almost any circumstance, this renders the
process impracticable on this polarity...There are some highly advanced
waveform AC power sources that may enable a user to realize some of the
benefit of the EP side of the sine wave (ie. cathodic cleaning). Yet, for
GTAW, the applications for DCEP are extremely limited (sheet metal).