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[MW:10771] Re: high frequency

By Materials & Welding
Hi,

High Frequency (HF) units are mainly used for GTAW process.

Starting the Arc:
After gas flow is established and providing HF is used, the electrode
does not have to touch the workpiece or starting block to effect arc
ignition. The superimposed high frequency current bridges the gap
between the electrode and the workpiece or starting block and thus
establishes a path for the welding current to follow.

High Frequency (HF):
The high frequency mode will initiate and maintain the arc during the
zero crossing of the A.C. sine wave. Three positions exist on most
GTAW machines.

1. Start - This mode helps arc initiation without making actual
contact to the work with the tungsten welding electrode. The "Start"
mode is most often used in D.C. welding.

2. Continuous - this also helps initiate the arc and continues
throughout the process to maintain the arc during periods when current
(amperage) is at the zero crossing point of the sine wave. This mode
is most often used in A.C. welding. This type of mode is often a built
in feature on most CIGWELD GTAW machines, and occurs automatically
when AC current for GTA welding is selected.

3. Off - The high frequency system does not engage during any part of
the process in this mode. Contact between the tungsten electrode and
work surface must occur before the arc can be initiated. A "Touch
Start or Scratch Start Practice" to initiate the arc can cause
contamination of the the tungsten electrode in the GTAW process. The
"Off" mode is often used for DC- TIG or stick welding (MMAW) where
scratch starting will initiate the arc.

Hope this will some information.

Cheers!

Raj

On Apr 20, 12:13 pm, senins welo <senins...@gmail.com> wrote:
> sir,
>
> What are the advantages of using *high frequency welding machine ?*
>   THANKS

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