mig co2 welding

8/21/2019 Mig Co2 Welding

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MIG CO2 Welding Process


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Advantages of MIG Co2welding

over stick arc welding (SMAW)

1. Higher weld metal deposition rate.2. Less heat input, hence decrease

distortion.

3. High weld metal recovery, hence

economical.

4. As there is no flux, weld deposit is

visible during welding process, hence

better control on welding.

5. Elimination of atmospheric

contamination gives stronger andmore consistent weld.

6. No entrapment of slag (While using

solid wire).

7. Little or no post weld clean up.

8. Large gaps can be filled easily.9. Thin weld can be easily welded.

10.Can be used in all positions.

11.Less skill required.

12.Choice of weld metal transfer mode

available.


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Disadvantages of MIG Co2

process

1. Drafty conditions can blow the shielding

gas away.

2. Cold lapping can happen low heat

input melts wire but not the work piece.

3. Equipment is more expensive and less

portable compared to SMAW.

4. High level of radiated light, heat and arc

intensity can be uncomfortable for some

operators.

5. More prone to poor penetration during

high welding speed.


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MIG Co2Welding Machine &

Accessories

MIG Co2Welding Setup.The machine consists of;

a. Power Source

b. Wire Feeder

c. Welding Torch.

Gas

a. Gas Cylinder

b. Gas Regulator

c. Heater

Accessories1. Protective equipment


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Selection of power source

1. Out put Current at 100% duty cycle.

2. Class of insulation.

3. Core winding (Aluminium or Copper).

4. Power consumption.Types of power source.

1. Silicon Diod

2. Thyristor

3. Inverter

Advantages of inverter;

1. Smooth arc.

2. Low spatter.

3. Finer controls.

4. Low power consumption.5. AC/DC out put from same source.


Accessories

Types of wire feeder

1. 2 rolls drive

2. 4 rolls drive


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Accessories

Functions of welding torch

1. Guiding the welding wire.

2. Carrying the shielding gas to

the weld pool.

3. Carrying the welding current

to the contact tip.4. Circulating water for cooling.

(Heavy duty welding).

Types of welding torches:

1. Air-cooled.

2. Water-cooled.

Shade Number Current Amps

10 Under 8011 80 - 125

12 125 - 175

13 175 - 300

14 300 - 500

15 Over 450

Recommended shade number of

filter for MIG Co2welding


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Shielding GasesShielding gases used in MIG Co

1. Carbon Dioxide.

2. Mixed gases, prime gas being Argon.

Effect of shielding gas on the

weld bead profile.


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Weld-Metal Transfer Mode

Principal modes of weld metal transfer.

1. Spray

2. Pulsed

3. Dip or short circuit

4. Globular


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Fig.3 Spray Transfer


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Pulsed arc metal transfer.

following variables:

1. Frequency The number of times

the current is raised and lowered

to form a single pulse. Frequency

is measured in pulses per second.

2. Amplitude The amperage or

current level of power at the peakor maximum, expressed in

amperage

3. Width of the pulses The amount

of time the amperage is allowed to

stay on.


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Short Circuit or Dip Transfer

Globular Transfer


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Parameter settingWire melting and deposition rate.

Deposition efficiency

M = Weight of Weld Deposit

E = Weight of welding electrode consumed

D =

M--- x 100E


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Parameter setting

Welding power supply

Molten weld pool control

The GMAW molten weld pool can

be controlled by varying.

Shielding gas

Power settingWeave pattern

Travel speed

Electrode extension

Gun angle.


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Parameter setting

Electrode extension (stick-out)

Heat buildup


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Parameter setting


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Welding techniques

Back hand

Fore hand


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MIG Co2 Welding wire (Solid)

Cast & Helix


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Flux cored welding wire

Manufacturing process

Cross section of the wire

Types of wires

Rutile

Basic

Metal cored


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Flux cored welding wire

Flux contains the following agents,

Deoxidisers

Slag formers

Fluxing agents

Arc stabilizers

Alloying elements

Function of slag formers


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Flux cored wire advantages &

disadvantages

High deposition rate

Minimum electrode waste

Less edge preparation

Minimum pre-cleaning

All position

Flexibility

Excellent control

mig co2 welding

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