Operating instructions

12
BOC Smootharc Advance II MIG 250C Operating manual
2.4 Fundamentals of MIG, FCAW and MCAW
Welding Technique
Successful welding depends on the following factors:
1 Selection of correct consumables
2 Selection of the correct power source
3 Selection of the correct polarity on the power source
4 Selection of the correct shielding gas
5 Selection of the correct application techniques
a Correct angle of electrode to work
b Correct electrical stickout
c Correct travel speed
6 Selection of the welding preparation
Selection of Correct Consumable
Chemical composition
As a general rule the selection of a wire is straightforward, in that it
is only a matter of selecting an electrode of similar composition to
the parent material. It will be found, however, that there are certain
applications that electrodes will be selected on the basis of its
mechanical properties or level of residual hydrogen in the weldmetal.
Solid MIG wires are all considered to be of the 'low Hydrogen type'
consumables.
The following table gives a general overview of the selection of some of
the BOC range of MIG wires for the most common materials.
Common Materials Welded with BOC MIG Wire
Material BOC MIG Wire
AS2074 C1,C2,C3, C4-1,C4-2,C5,C6 BOC Mild Steel MIG Wire
BS3100 AW1,A2,A3 BOC Mild Steel MIG Wire
BS1504-430,480,540 BOC Mild Steel MIG Wire
ASTM A36,A106,EN8,8A BOC Mild Steel MIG Wire
Stainless Steel
Grade 304 BOC Stainless Steel 308LSi
Grade 309 BOC Stainless Steel 309LSi
Grade 316 BOC Stainless Steel 316LSi
Physical condition
Surface condition
The welding wire must be free from any surface contamination including
mechanical damage such as scratch marks.
A simple test for checking the surface condition is to run the wire
through a cloth that has been dampened with acetone for 20 secs. If a
black residue is found on the cloth the surface of the wire is not properly
cleaned.
Cast and Helix
The cast and helix of the wire has a major inuence on the feedability of
MIG wire.
If the cast is too large the wire will move in an upward direction from the
tip when welding and if too small the wire will dip down from the tip.
The result of this is excessive tip wear and increased wear in the liners.
If the helix is too large the wire will leave the tip with a corkscrew e󹟽ect.
Typical Metal Transfer Mode
Process
Dip
Transfer
Globular
Transfer
Spray Transfer
Metal Inert Gas
(MIG)
✓ ✕ ✓
Flux Cored
(Gas Shielded)
✓ ✓ ✓*
Flux Cored
(Self Shielded)
✓ ✓ ✕
Metal Cored
✓ ✕ ✓
* Not True Spray
Cast
Helix
Cast – Diameter of the circle
Helix – Vertical height
Cast and Helix