Jasic EVO 2.0 EM-160C, Operator'S Manual

Page: 41 / 82

41
GUIDE TO MIG/MAG WELDING
Before starting any welding activity ensure that you have suitable eye protection and
protective clothing. Also take the necessary steps to protect any persons within the welding
area.
Modes of Transfer
Dip or short circuit mode
In the dip or short circuit, the wire (electrode) touches the work piece and a short circuit is created. The
wire will short circuit the base metal between 90 and 200 times per second. This method has the benefit
of creating a small, quickly solidifying weld puddle. The deposition rates, wire speed and voltages are
usually lower than other modes of transfer and the low heat input makes it a flexible mode for both thick
and thin metals in all positions.
A - Consumable wire feed to work piece and short circuit is created
B - Wire starts to melt due to short circuit current
C - Wire pinches off
D - Arc length opens due to burn off
E - Wire advances towards the work piece
F - Wire short circuits and the process cycles again
Some of the disadvantages of this method are limited wire feed speed and hence weld deposition
rates. On thicker material there can also be a danger of “ cold lapping ” occurring. This occurs when
there is not enough energy in the weld puddle to fuse properly.
Another disadvantage is that this mode produces an increased amount of spatter due to the short circuits
especially compared to the other transfer methods.
An inductance is used to control the surge in current when the wire dips into the weld pool.
Modern electronic power sources can automatically set the inductance to give a smooth arc and metal
transfer.
Globular Transfer Mode
The globular transfer method is in effect an uncontrolled short circuit which occurs when the voltage
and wire are above the dip range but too low for spray. Large irregular globules of metal are transferred
between the torch and work piece under the force of gravity.
The disadvantages of this method of transfer are that it produces a large amount of spatter as well as
high heat input. In addition, globular transfer is limited to flat and
horizontal fillet welds above 3mm. Lack of fusion is often common
because the spatter disrupts the weld puddle. Also, because globular
transfer uses more wire it is generally considered less efficient.
The advantages of globular transfer are that it runs at high wire feed
speeds and amperages for good penetration on thick metals. Also,
when weld appearance is not critical it can be used with inexpensive,
CO2 shielding gas.