Esab Training Ppt
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ESAB India Your partner for welding
•Employs around 750 persons •ESAB is represented in almost every part of the country•Sales and support is established every industrial location•5 manufacturing plants•Sales regions:
– North– South– East– West– Central
Taratala (Kolkata)Taratala (Kolkata)
Sriperumbudur (Chennai)Sriperumbudur (Chennai)
ESAB IndiaEquipment production centers
ESAB IndiaEquipment sales offices
New Delhi
Mumbai
Kolkata
Chennai
Nagpur
MMAW / SMAW PROCESS
i) This is a group of processes in which the heat required for fusion is generated by the electric arc formed between a metallic electrode and the base metal. The electrode is consumed in the arc and provides the filler metal for the joint.ii) Electric arc was discovered by Sir Humphrey Davy in 1801.iii) Oscar Kjellberg of Sweden is credited with being the pioneer of modern coated arc welding electrodes. In 1907, he was granted a patent on covered electrodes. By 1907 first welding generator was introduced in the U.S. market.iv) The electric arc is an ideal source of welding heat. v) Among the arc processes MMAW is the most common, versatile and inexpensive one and accounts for over 60% of the total welding in advanced countries and over 90% of the total welding in India.
THE WELDING ARC
A welding arc is the passage of electricity across a gap between an electrode and the parent metal or work.
Arc length is related to arc voltage.
Common Welding Power Sources
Transformer – AC In AC Out Conventional Rectifier- AC In DC
Out Inverter Based Rectifier – AC In DC
Out
Equipment for every arc welding process
Common Welding Processes
Manual Metal Arc Welding (MMAW)
Metal Inert Gas/Metal Active Gas (MIG/MAG) Welding
Tungsten Inert Gas (TIG) Welding
Submerged Arc Welding (SAW)
Advantages Of MIG Welding
The MIG /MAG welding process provides many advantages in manual and automatic metal joining for both low and high production applications. Its combined advantages when compared to MMAW ,TIG & SAW :
• Welding can be done in all positions.• No slag removal required. High weld metal deposition rate.• Overall times for weld completion about 1/2 that of covered
electrode.• High welding speeds. Less distortion of the workpiece.• High weld quality.• Large gaps filled or bridged easily, making certain kinds of
repair welding more efficient.• No stub loss as with covered electrode.
18
Process Variables – GMAWVARIABLES DESCRIPTION
Welding Current Has a non-linear relationship with electrode feed speed or melting rate
Polarity(Straight / Reverse)
DCEN – Direct Current Electrode Negative or Straight Polarity
DCEP – Direct Current Electrode Positive or Reverse Polarity
Arc Voltage An approximate means of starting the physical arc length
Travel Speed The linear arc rate at which the arc is moved along the weld joint
Stick Out The distance between the end of the electrode and the contact tube
Burn Back A time delay between wire feed unit starts to brake the wire until the power unit shuts off the welding current
Electrode Diameter
Higher electrode diameter requires higher current than comparatively smaller diameter electrodes and produce
higher weld deposition
Shielding Gas Shields the molten metal from atmospheric contact
20
Shielding Gases used in GMAW
Shielding Gases provide a shielding to the weld metal from
the atmospheric contact and have a pronounced effect on
• Arc characteristics• Mode of metal transfer
• Penetration and weld bead profile• Speed of welding
• Undercutting tendency• Cleaning action
• Weld metal mechanical properties
Types of shielding gases used in GMAW are
• Carbon Dioxide (CO2)• Argon
• Helium• Oxygen
• Mixtures of above Gases
PARAMETERS DESCRIPTION
Arc Voltage It is the electrical potential between the electrode and the work-piece
Slope Measured at two stable arc conditions of the CV characteristics
Inductance The inductance in the circuit controls the rate of current rise and in turn the pinch effect.
WELDING PREPRATION- GMAW
The GMAW Power Source should have a Drooping Characteristics.
When welding is in progress the relation between the Welding Voltage (V) and the Welding Current (I) is expressed by the following mathematical formula
V = 14 + 0.05 I
24
ESAB GMAW Product Range
Diode based GMAW
• MIGMATIC 250• MIGMATIC 400
• POWER COMPACT 255
Thyristorised GMAW
• AUTO K 400• AUTO K 600
Inverter based GMAW
• ESABMIG 300i / C300i• ARISTOMIG 300 / C300• ARISTOMIG 400 / U400• ARISTOMIG 500 / U500
Principle of Material Transfer
MIG/MAG welding is performed in two waysdepending on the transfer of the metal;
SPRAY TRANSFER WELDING
OR
DIP TRANSFER WELDING
27
Wire feed speed = welding current
Increased current (= wire feed speed) gives deeper penetration
Date/Month/Year. 28
Voltage, Mig/Mag
Increasing the voltage• increases the arc length
• produces a hotter, wider weld pool• reduces the short-circuiting frequency when
using short-arc welding (=larger droplets)• produces more spatter.
Too low a voltage produces a tendency to spatter.
When welding thin sheet materials, short-arc welding facilitates high production speeds without burning through the material. For such applications, use a low arc voltage
setting, with stable arc (use a high short-circuiting frequency)
High Voltage Medium Voltage Low VoltageLong arc length Medium arc length Short arc length
weld profile butt weld
weld profile fillet weld
With constant wire feed speed
Date/Month/Year. 30
InductanceInductance affects MIG/MAG welding when
short arc welding.When welding with spray arc inductance influences only
the start.
Low inductance:• a distinct and concentrated arc
• somewhat more spatter• for welding thin wires and low currents
High inductance:• softer arc
• hotter process• pool spreads somewhat better
• used for thicker wires
too high inductance results in fewer short circuits, unstable arc and sputtering tendencies at low arc
voltages
Low Medium High
32
Welding torch – front end parts
•Learn to identify parts & correct assembly
• Check front end parts• Clean periodically
• Learn nozzle cleaning and liner replacement procedure
33
Choose the right contact tip
Size ofelectrode
Recommended nozzle opening
Short arcCO2
Spray arcAr/CO2 or pure Ar
Nozzle Diff. Nozzle Diff.0,6 0,8 0,2 0,9 0,30,8 1,0 0,2 1,1 0,31,0 1,2 0,2 1,5 0,51,2 1,5 0,3 1,7 0,51,6 1,9 0,3 2,1 (1,9) 0,5
Date/Month/Year. 34
Wire feed unit - rollers
Feed roller types:• Feed rollers must suit the wire diameter in use. • Rollers are grooved for two or more different wire diameters.
Turn roller 180 degrees for other groove. • V type rollers for harder mild steel, stainless and cored wires• VK type rollers are for cored wires (V groove, knurled)• U type rollers for softer Aluminium wires
Date/Month/Year. 35
•Electricity
•Electromagnetic fields
•UV,IR and visible light radiation
•Air pollution
•Fire and Spatter
•Noise
•Ergonomics
The welder’s working environment
Welders are members of an occupational group which is exposed to a number of difrrent enviromental problems
Effective protection can reduce the health risk
Date/Month/Year. 36
Electricity
Risk of electric shocks• The level and duration of
the current• The current path through
the body• The frequencey of the
current
Human beings are extremely sensitive to current that passes through thier bodiesSeriuos injury can be caused by curremt of just 20 to 30 mA
Date/Month/Year. 37
Welding equipment
EN 60974-1
Open circuit voltage
DC Max 113V
AC Max 80 V rms
Date/Month/Year. 38
UV,IR and visible light radiation
• Eye damage• Skin damage• Thermal radiation
The diffrent welding methods give diffrent levelof radiation
Mig/MagMMA
Tig
Date/Month/Year. 39
Air pollution- FumeWelding fumes are a result of the vaporisation and oxidation of different substances
In the arc which is caused by high temperature
Material safety data sheet are availble for each product specifying the level and
conatent of the fume
Date/Month/Year. 40
Fire and spatter
Date/Month/Year. 41
Noise
Date/Month/Year. 42
ErgonomicsWhen welding heavy material manually and during assembly welding
the loads are very static. Positioning welding also give high load.