Explanation Of Tig Parameters, Functions And Welding Terms - Everlast Typhoon 500 Operator's Manual

Component Identification and Explanation

Explanation of TIG Parameters, Functions and Welding Terms

Alternating Current (AC). Used in TIG mode on this welder to weld Alumi-
num and Magnesium. It is composed of the flow of electrons rapidly alter-
nating between Electrode Negative and Electrode Positive polarity.
AC Balance. Used to weld Aluminum and Magnesium, the AC wave form
is formed by alternating the arc polarity rapidly between the electrode neg-
ative and electrode positive poles which changes the flow direction of the
electrons. The electrode negative portion of the wave form provides most
of the penetration and heat that goes into the weld. The Electrode positive
portion imparts a smaller amount of heat to the weld as the flow of elec-
trons travels from the puddle to the Tungsten. However, the Electrode
Positive phase of the cycle does provide a scouring action which cleans
the weld by removing the oxide layer by literally breaking and ripping up
the oxidation, leaving an etched area under the weld puddle area and
along the sides of the weld. If the two wave form halves are equal in length
this means an equal time is spent between the positive and negative phas-
es of the AC cycle. Even though cleaning is needed, there are problems
with AC positive polarity. When the AC cycle enters the positive polarity
phase, excess heat builds up on the Tungsten and it begins to ball due to
electrons flowing from the weld to the tungsten. Little heat is put back into
the weld. Another issue is the excess cleaning can occur and the weld will
have wide areas of etching (cleaning) on the sides of the weld, which are
generally undesirable. Some transformer welders were able to slightly
skew the "balance" of the wave form, making one "half" of the wave form
longer than the other "half". In other words instead of having a 50/50 bal-
ance, they were able to create a 40/60 balance, but this adjustment was
limited With modern inverters, the wave forms are much more adjustable
and the balance has even greater adjustment range. In testing even with
5% Electrode Positive can provide enough cleaning to weld, while the
other 95% of the arc energy can be put into heating the weld and provid-
ing penetration. The ability to adjust the balanced between the positive and
negative cycles allows more penetration with less amps, narrower, less
unsightly cleaning lines, and the ability to weld without a ball on the end of
the tungsten. With the ability to weld without a ball on the tungsten, the
arc stays more stable, and is focused more back into the weld. The range
on this unit is expressed as a percent of AC positive, with the idea in mind
that "full" AC cleaning is 100% Electrode Positive and 0% electrode nega-
tive. Some brands express this with a reciprocal value of Electrode Nega-
tive. So what would be a "safe" 30% electrode positive setting on the Ever-
last, becomes a 70% electrode negative setting on other brands. Everlast,
along with other brands has chosen this way polarity orientation since the
amount of cleaning is always discussed as a primary concern when weld-
ing aluminum. Increasing over 40% on AC balance will cause tungsten to
begin to ball. There are legitimate reasons for welding over 40%, as in
when the plate is heavily contaminated or oxidized, but if you need over
40% cleaning, you will need to change to a larger tungsten that will hold
the point better. Once the tungsten begins to ball excessively, the arc will
begin to wander or may break up completely. Signs of too little cleaning
action while welding aluminum include soot, porosity, and dull looking
(scummy) welds. A dedicated stainless-steel brush and suitable aluminum
cleaner such as acetone should be used before starting any aluminum
weld to help break up the heaviest oxide layer so less Positive polarity
cleaning action is needed and better penetration can be achieved by using
more Negative polarity during one complete AC cycle.
What is AC Balance?
See the example below on how the AC balance functions. Keep in mind
the AC balance of this welder is a percent of Positive Polarity. A setting
of 30%, would be 30% cleaning, and 70% penetration.
AC Wave Form Balanced to 50/50 (Not Ideal)
50%
Electrode Positive +
Cleaning
AC Wave Form Skewed to 30/70 (Typical)
30%
Electrode Positive +
Cleaning
What is the effect of AC Balance?
30% Positive
60% Positive
Symptoms of too much Positive Balance: Tungsten balling, wide etched
area, grainy weld. Arc instability can become an issue as well.
What Balance Setting is Best?
Start with an AC balance setting of 25 to 35%. This will offer a good
compromise between cleaning and penetration. Rarely exceed 40%. 35-
40% would be a setting used on dirty cast Aluminum or heavily oxidized
material that may have been subjected to salt water previously. Settings
above 45% will begin to significantly ball the tungsten and cause arc
instability. Maximum setting may cause the Tungsten to erode rapidly.
52
One AC Cycle
50%
Electrode Negative -
Penetration
One AC Cycle
70%
Electrode Negative
Penetration
50% Positive
Cleaning/Etched Area of Aluminum