Resistance Welding:

 Spot Welding
 Projection Welding
 Seam Welding
 Upset Butt Welding
 Flash Butt Welding
Arc Welding
 MIG –Metal Inert Gas (Consumable Electrode + Inert Gas Argon,Helium Mixture)
 MAG –Metal Arc Gas (Consumable Electrode + C02 Gas)
 TIG –Tungsten Inert Gas (Non- Consumable Electrode+ Gas- Argon ,Helium Mixture)
 C02 Welding (MAG welding)
 Sub merged Arc welding
 SMAW –Shield Metal Arc Welding (No Gas –Arc Welding))
 GMAW – Gas Metal Arc Welding (MIG,MAG & TIG)
 Brazing (Induction Brazing ,Pot Brazing, Manual Brazing)
 Soldering
Welding Process Variables (GMAW / MIG /Co2)
o Machine Used ( 250 A / 400 A)-Based on machine wire size and Torch Selection
o Current (A)
o Voltage (V) (Recomm 20 -30 V)
o Wire Size (0.8 /1.0 mm)
o Type of Shielding gas (Argon,Co2,O2) –(i) Co2 -100% (ii) 25% Co2 +75% Argon (iii)2% Co2+98% Argon
o Gas Flow Rate (15-20 Lpm)
o Stick out Distance (10-15 mm)
o Electrode Angle (70° -80° )
o Weld Joint Position
o Operator Skill
o Travel Speed (Automatic)
o Wire Feed Rate (mm/Minute)
o Base Material (Carbon Steel – Alloy Steel-Aluminium etc)
o Filler Material (ER70S-6)
Technique of Welding:
o Forehand Technique (Push Type)
o Backhand Technique (Pull Type) -Recommended
o Clock Wise (Push Type of Fore Hand Technique)
o Anti Clock Wise (Pull Type or Back hand Technique)
Metal Transfer Across the Arc :
o Short Circuit Transfer
o Globular Transfer
o Spary Transfer
o Pulsed Spary Transfer
**Metal Transfer depends on the Parameters Setting**
** Normally Short Circuit Trnasfer used for Simple Application of Automobile**
Short Circuit Transfer :
It is used on thinner metals. This transfer type produces a fast, high pitch crackling sound.
This type of transfer is set-up by using a high percentage of Co2 shielding gas or 100% carbon dioxide.
In order to have a short circuit transfer, the voltage needs to be set on the lower range. For most hobbyists, this
is the type of transfer that will be used.
Globular Transfer :
Globular transfer requires more voltage and a higher percentage of Argon gas. This transfer type has a popping
sound to it. Globular transfer is used on thicker metals, and in some cases, when welding stainless steel.

Spray Transfer :
Spray transfer uses a high percentage of Argon gas or pure Argon depending on the type of metal welded. True
spray transfer has a hum or hissing sound to it. When it comes to welding thicker metals, spray transfer is
sometimes defined by a minimum voltage and amperage setting. In this case, it will have a deep, fast crackling
sound when welding. It may seem like short circuit, but the fact is the wire is being sprayed into the weld joint.

Pulse Spray Transfer :

Pulse or pulse spray transfer is a special setting on high end MIG welders. What this does is create a pulsing
action with the voltage and amperage while welding. This helps control the puddle when welding out of
position and is commonly used when MIG welding pipe

Power Source :
 MIG welding is carried out on DC electrode (welding wire) positive polarity (DCEP). However DCEN is
used (for higher burn off rate) with certain self- shielding and gas shield cored wires
 DC output power sources are of a transformer-rectifier design, with a flat characteristic (constant
voltage power source). The most common type of power source used for this process is the switched
primary transformer rectifier with constant voltage characteristics from both 3-phase 415V and 1-
phase 240V input supplies.
 To Avoid Thyristor & Diode Type Machine
 Prefer Only Inverter Type & Pulse Rate machine to be used

Carbon Equivalent (CE) :

CE = C + Mn/5 + Mo/5 + Cr/5 +Ni/15 + Cu/15 + Ph/3

If CE ≤ 0.4 – No Adjustment required – Alloy is Weldable

If 0.4 < CE ≤ 0.6 – Need Used Low Hydrogen Electrode
If CE > 0.6 – Need Use Low Hydrogen Electrode & Increase Welding heat input ,preheat,Postheat or Impose Post Cooling
Rate
Key Notes of GMAW (MIG/MAG/TIG) Welding:
 Carbon Content of the material should be less than 0.4% Carbon in the Welded Materials
 If more than 0.4% Carbon of Welded Material possibility of Weld Crack -Pre-heating is required (200° C)
 Hardness of the Welded HAZ (Heat Affected Zone) not more than 400 HV . if More Post-heating/ Sand Cooling is
required
 Penetration Checking (As per ASTME )
o Above 5mm Thickness = 0.5 -2.0 mm depth based on Load Application
o Below 5 mm Thickness = 10% - 20% Minimum Sheet Thickness
o HAZ Should not Exceed 400HV
Root Fusion must be completed –(Root fusion zero is not Acceptable)
 Stick out 0.8 Wire = 5-10 mm & 1.2 Wire = 10-15 mm
 Preferred Gas : Argon -86% & Co2 -12% & O2 -2%
 Input Power Should Min Power : 410 V Min (Ref :Single Phase : 230V If 3 Phase 460 V---Avg 410 V)
 To Avoid Thyristor & Diode Based Welding machines
 Only Preferred Pulse synergic (or) Invertor based machine to be used which have good Control
  Welding position (1F, 2F, 3F, 4F) to be maintained appropriately
 Gas Heater to be provided in the Gas Flow Area to avoid the Moisture formation
 Low Voltage Machine can’t weld Thicker Materials
 Commonly used electrode for Mild steel is ER70S-6 with thick of 0.8mm
o “ER” Stands Electrode or Filler Rod
o “70” Stands for Welding Strength (70,000 Pounds of Tensile strength Per SQ Inch)
o “S” Stands for Solid Wire
o “6” Stands for amount of Cleaner that is added to the wire to improve weld Quality
 Carbon Content in the Material not affect the Penetration – Only Welding Crack
 Hardness of the material increases surface tension of material increases which effect the Penetration

Recommend:
 12 Gauge or 2.5mm mild steel requires 18.5 volts and 180 IPM wire feed speed.
 3/16” or 4.7mm mild steel requires 19 volts and 225 IPM wire feed speed.
 1/4” or 6.35mm mild steel requires 20 volts and 260 IPM wire feed speed.
 3/8”or 9.525mm mild steel requires 21 volts and 310 IPM wire feed speed.

 Arc Current (A) Changes : Bead Height Increases / Decreases – Penetration Increases/Decreases
 Voltage (V) Changes Bead Width Increases and Penetration Decreases
 Current (A) is directly Proportion Penetration (Bead Height )to Each Other
 Voltage (V) is Reverse Proportion to Penetration (Bead Width) – Voltage Increases Bead Width Increases -

GMAW – Gas Metal Arc Welding (MIG –MAG-TIG)

SMAW-Shielded Metal Arc Welding

MIG / MAG - Welding Principle:

Generation of Welding Machine:
 Diode Type
 Thyristor Type
 Inventor Type
Different Types of Weld : (i) Groove Weld (ii) Flat Weld
 Groove welds - Producing butt joints.
 Fillet welds - used in overlap, T- and corner joints.
 Backing welds are applied to back or root side of the joint.
 Plug or slot welds - used for prepared holes of overlap joints.
 Arc spot welds can be produced from one side of lap joints without prepared holes.
 Seam welds are the continuous welds which extend across the entire length of the joint from one end
to another.
 Surfacing welds - Filling the worn surfaces of machine parts with stringer or weave beads.
 Tack welds are often used to assist assembly or to maintain edge alignment during welding.

Welding Position:
 Flat position: In this position, the filler metal is deposited from the upper side of the joint and the face
of the weld is approximately horizontal. In welding terminology this is also called the down-hand
position for both groove welds and fillet welds.
 Horizontal position: The position of welding in which the weld is performed on the upper side on a
horizontal surface and against an approximately vertical surface.
 Overhead position: The weld is deposited from the underside of the joint and the face of the weld is
horizontal.
 Vertical position: The weld axis is approximately vertical. The welding direction can be changed up and
down.

Compare MIG & MAG Welding?

MIG – Metal Inert Gas Welding (Inert Gas : Argon ,HeliumC02 )
MAG – Metal Active gas welding (Active Gas : Co2 ,O2 & Argon)
MIG stands for Metal Inert Gas.

Only inert gases or gas mixtures are used for the shielding gas when MIG welding. Typical inert gases used for
MIG welding are argon and helium. These gases are usually used for MIG welding of aluminium and other non-
ferrous metals.

MAG stands for Metal Active Gas.

Active gas mixtures have been developed primarily for welding steels. Typical shielding gases are mixtures of
argon, carbon dioxide and oxygen e.g. CO2 , Ar + 2 to 5% O2 , Ar + 5 to 25% CO2 and Ar + 10% CO2 + 5% O 2 .

The composition of the shielding gas has a substantial effect on the stability of the arc, metal transfer and the
amount of spatter. The shielding gas also affects the behaviour of the weld pool, particularly its penetration and
the mechanical properties of the welded joint.

In the US, both MIG and MAG welding are described by the term GMAW ( Gas Metal Arc Welding)