Ca
rb
on
ro
d
fe
ed
in
g
di
re
ct
io
n
Gouging direction
1
2
3
5
4
α
L
Fig. 14-3-1: CAC-A process
1- Carbon rod 2- Gouging torch chuck 3- Compressed air 4- Work piece 5- Arc L- Carbon rod extension length α-Angle
between carbon rod and work piece
Welding parameter for CAC-A and effects
12 Power source polarity
CAC-A usually choose DC reversed polarity (work piece connect to negative electrode). So the arc is stable, melting metal
mobility is better, freezing point is lower, so reversed polarity ensure stable gouging process, arc sends out continuous swish
sound, width of dadoing is equal, smooth and bright. If it is wrongly connected, arc is not stable and sends out inconsistently
blare sound.
Current and carbon rod diameter
Current is proportional to carbon rod diameter. Generally consult the follow formula to choose current:
I=(30
～
50)D
I- Welding current
（
A
）
D- Carbon rod diameter
（
mm
）
For a certain diameter carbon rod, if current is small, then arc is not stable, and carbon inclusion defect occurs easily;
increase current appropriately, can improve gouging speed, smooth surface of dadoing, increase its width. In practice,
choose larger current generally. But if current is over, carbon rod burns quickly, even melt, cause serious carburize. Diameter
chosen for carbon rod is according to dadoing width, the bigger of diameter, and the broader of dadoing is. Generally,
diameter is 2~4 mm smaller than dadoing width. Carbon rod standard and suitable current, please refer to the following table:
85
Sectional form shape
Round
Suitable current/A
150~180
150 200
150 250
180 300
200 350
250 400
350 450
350 500
~
~
~
~
~
~
~
Carbon rod standard /mm
φ3×355
φ4×355
φ5×355
φ6×355
φ7×355
φ8×355
Φ9×355
φ10×355
