Basic Information Regarding Mig Welding; Connection And Preparation Of Equipment For Welding; Welding; Carbon Steel Welding - Oerlikon CITOLINE 3000T Safety Instruction For Use And Maintenance

5.0 BASIC INFORMATION REGARDING MIG

WELDING

MIG WELDING PRINCIPLES
MIG welding is autogenous, i.e. it permits welding of pieces made
of the same metal (mild steel, stainless steel, aluminium) by fu-
sion, while granting both physical and mechanical continuity. The
heat required for melting is generated by an electric arc that
strikes between the wire (electrode) and the piece to be welded.
A shield gas protects both the arc and the molten metal from the
atmosphere.
6.0 CONNECTION AND PREPARATION OF
EQUIPMENT FOR WELDING
Connect welding accessories carefully to avoid power loss
or leakage of dangerous gases.
Carefully follow the safety standards
N.B. DO NOT ADJUST SWITCHES DURING WELDING OPER-
ATIONS TO AVOID DAMAGE TO THE EQUIPMENT.
CHECK THAT GAS IS DELIVERED FROM THE NOZZLE AND
ADJUST FLOW BY MEANS OF THE PRESSURE REDUCER
VALVE.
CAUTION: SCREEN GAS FLOW WHEN OPERATING IN OUT-
DOOR OR VENTILATED SITES; WELDING OPERATIONS
MAY NOT BE PROTECTED DUE TO DISPERSION OF INERT
SHIELDING GASES.
6.1 WELDING
1. Open the gas cylinder and regulate gas outlet flow as re-
quired. Fit the earth clamp on a part of the welding piece with-
out any paint, plastic or rust.
2. Select the welding current by means of switches (Ref. 11 - Pic-
ture 1 Page 4., - Picture 2 Page 5.); bear in mind that the greater
the welding thickness, the more power is required. The first
switch setting is suitable for minimum thickness welding.Also
take into account that each setting features a specific wire drive
speed which can be selected by means of adjustment knob (Ref.
4 - Picture 1 Page 4., - Picture 3 Page 5.).
6.2

CARBON STEEL WELDING

For MIG welding, proceed as follows:
1. Use a binary shielding gas (commonly a AR/CO2 mixture
with percentages ranging from 75-80% of Argon and from 20-
25% of CO2), or ternary mixtures such as AR/CO2/O2.
These gases provide welding heat and a uniform and com-
pact bead, although penetration is low. Use of carbon dioxide
(MAG) as a shielding gas achieves a thin and well-penetrat-
ed bead but ionisation of the gas may impair arc stability.
2. Use a wire feed of the same quality of that of the steel for
welding. Always use good quality wire; welding with rusty
wires can cause welding defects.
In general the applicable current range for wire use is:
- Ø wire mm x 100 = minimum Amps.
- Ø wire mm x 200 = minimum Amps.

BASIC INFORMATION REGARDING MIG WELDING

For optimal welding, keep the
torch in the same direction as the
wire feed, as illustrated in figure.
Example: Ø filo 1.2 mm= minimum Amps 120 mm/maximum
Amps 240. The above range is used with binary AR/CO2 gas
mixtures and with short-circuiting transfer (SHORT).
3. Do not weld parts where rust, oil or grease is present.
4. Use a torch suited to welding current specifications.
5. Periodically check that the earth clamp pads are not dam-
aged and that the welding cables (torch and earth) are not cut
or burnt which could impair efficiency.
6.3

STAINLESS STEEL WELDING

MIG Welding of 300 series (austenitic) stainless steel must be car-
ried out with a shielding gas that has a high Argon content and a
small percentage of O2 to stabilise the arc. The most commonly
used mixture is AR/O2 98/2.
- Never use CO2 or AR/CO2 mixtures.
- Never touch the wire.
The filler material used must be of a higher quality than the base
material and the welding zone must be completely clean.
6.4

ALUMINIUM WELDING

To MIG weld aluminium, use the following:
1. 100% Argon shielding gas.
2. Filler wire with a composition suited to the base welding ma-
terial. To weld ALUMAN and ANTICORODAL use 3-5% sili-
con wire.To weld PERALUMAN and ERGAL use 5%
magnesium wire.
3. Use a torch designed for aluminium welding.
6.5

SPOT WELDING

This type of welding is used for spot welding two overlapping
sheets, and requires the use of a special gas nozzle.
Fit the spot welding gas nozzle, press it against the piece to be
welded. Press the torch button; note that the welder will eventually
detach from the piece. This time period is fixed by the TIMER con-
trol (Ref. 5 - Picture 1 Page 4., - Picture 3 Page 5.), and must be
set depending on the thickness of the material.
7.0

MIG WELDING FAULTS

FAULT CLASSIFICATION AND DESCRIPTION
MIG welds may be affected by various defects, which are impor-
tant to identify. These faults do not differ in form or nature from
those encountered during manual arc welding with coated elec-
trodes. The difference between the two applications lies rather in
the frequency of defects: porosity, for example, is more common
in MIG welding, while inclusion of slag is only encountered in
welding with coated electrodes.
The causes and prevention of faults are also quite different. The
following table illustrates the various faults.
6 EN
EN