CIGWELD 200i Instruction Manual download pdf (Page 37)

TRANSTIG 300 AC/DC

January 16, 2008

7-1

SECTION 7:

BASIC TIG WELDING GUIDE

7.01 Explanation of “Fluttery Arc”

when AC TIG Welding on

Aluminum

The following will assist in understanding the

phenomenon of Arc Flutter, also referred to as Arc

Rectification.

The basic thesis is that the fluttering is caused by

lack of oxide in the weld pool.

The oxide layer on the plate reduced the energy for

electron emission. Electron emission from the weld

pool (DC+) causes the oxide layers to be disrupted,

the so-called “cleaning action”. However once the

cleaning action has produced a mirror like surface on

the weld pool, the effect of the oxide layer is limited

because the oxide layer has dissipated. This makes

electron emission from the weld pool more difficult

and increases the chance of arc instability.

This idea is supported by the observation that once

fluttering starts it can be made to stop by working

the arc away from the mirror like weld pool to an area

of oxide coated material. As soon as this is done the

arc settles back to a stable condition. So while the

arc is “consuming” oxide coated plate the instability

does not occur. But once the arc is stationary, the

pool becomes thoroughly “cleaned” by election

emission, the fluttering begins.

Tests conducted on various types of AC TIG power

sources, Fluttery Arc is not confined to one type of

power source or its' design, both conventional and

inverter types suffer from the same problem.

AC TIG on aluminum

1. The Problem: Arc appears unstable and pulses or flutters. ie. appears to rapidly change welding current

Conditions that accentuate arc flutter: Conditions that minimizes arc flutter:

• Cold work piece • Preheat the work piece

• Very short arc length • Increase the arc length

• Weld pool crater about 0.39” to 0.47”

(10 to 12mm) diameter

• Introduce filler rod material to the weld

pool, which introduces oxides

• Arc field in one spot to produce

“mirror” clean weld pool

• Move the weld pool around to introduce

oxides to the weld pool

• Increased cleaning action

i.e. Prolonged oxide emission from a

stationary weld pool increases the

likelihood of arc flutter

• Decrease the cleaning action by turning

the

WAVE BALANCE

to below 50% or

move the weld pool around

• Accentuated when tungsten running

near its current capacity, i.e. Molten ball

on end

• Use a larger diameter tungsten electrode

Table 7-1: Reduction of Arc Flutter

2. Conclusion: Fluttery Arc in AC TIG is a physical phenomenon independent of machine design.

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 67 68

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CIGWELD 200i Instruction Manual Page 37

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