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[MW:1353] Fw: [MW:1352] Re: Usage of AC in aluminium welding.

By Materials & Welding

Dear Friend,

AC has following advantages over DC power source

1. If we  use DC SP 70% of heat will be generated on base plate & 30% heat gererated on Tungsten electrode.
    Because of this penetration is good but oxide cleaning action is poor. ( Alluminum will form thin tenacious oxide layer & this layer               should be removed before welding by scrapping or acid cleaning methodes).
2. If we use DCRP 70%H on Tungsten electrode & 30% on base plate. ( Current carrying capacity of Tungsten electrode is 1/3 of DCSP). Result is poor penetration but good oxide cleaning action.
( Oxide cleaning action can be seen as a white etched line besides the weld bead).

3. In AC, Polarity changes alternatively, we can get optimum penetration & oxide cleaning action.

4. Now a days, all machines are equipped with Square wave AC rather than normal AC.

5. Normal AC requires HF unit in the Circuit  to reignite the arc ( AC will have arc rectification problem). HF unit can be avoided with Square wave AC.

6. Peak current levels for a given heat input is Square wave AC is less. Heat input required for a given plate thickness is also less.


Regards
P.K
 




----- Forwarded by Kataiah/BelleliSA on 25/11/2008 10:49 ص -----
"Sukamal Naskar" <sukamalbecmet@gmail.com>
Sent by: materials-welding@googlegroups.com

25/11/2008 08:35 ص
Please respond to materials-welding

       
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        Subject:        [MW:1352] Re: Usage of AC in aluminium welding.



yes, AC has less heat input as well as less weld penetration.
 
Regards
On 11/25/08, Muhammed Ibrahim <ibratech@gmail.com> wrote:
Hi friends,
 
Anybody can give an explanation why AC current is recommended for Aluminium welding?
 
Is there any effect in heat input when using AC intead of DC?


Thanks & Regards
Muhammed Ibrahim PK

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