gas tungsten arc welding
TRANSCRIPT
Gas Tungsten Arc Welding
By HARDISH TRIVEDI
1PRESENT BY:HARDISH TRIVEDI
GTAW
• Fusion Welding Process
• Arc Between Non-Consumable Tungsten Rod And Work
• Arc & Weld Pool Shielded By Argon
• Filler Wire Separately Added To Weld Pool
• Welding Torch & Tungsten Rod Cooled by Flow OF Argon / Cooling Water
2PRESENT BY:HARDISH TRIVEDI
Shielding Gas• Inert Gas - Argon , Helium• Common Shielding Gas – Argon• When Helium Is Used – Called “Heli – Arc” Welding• When Argon Is Used – Called “Argon Arc” Welding• Inert Gas Prevents Contamination Of Molten Metal• It Prevents Oxidation Of Tungsten Rod• It Ionizes Air Gap and Stabilizes Arc• It Cools Welding Torch & Tungsten Rod
3PRESENT BY:HARDISH TRIVEDI
Equipment & Accessories
– +
Argon Gas In
Flow Meter
Welding Cable & Cooling Water In Tube
HF Unit & Water Cooling
System
Argon Cylinder
Pressure Regulator
Cooling Water In
Cooling Water OutArgon Shielding
Tungsten Rod
Power Source
Work
Arc
+High Frequency
Connection
Solenoid Valve
Ceramic Cup
Pedal Switch
Gas Lens
Collet
4PRESENT BY:HARDISH TRIVEDI
GTAW Equipment & Accessories
• Power Source – Inverter, Thyrester,Rectifier, Generator
• High Frequency Unit• Water Cooling System• Welding Torch- (Ceramic Cup, Tungsten Rod,
Collet, Gas-lens) • Pedal Switch• Argon Gas Cylinder • Pressure Gauge, Regulator, Flow Meter • Earthing Cable With Clamp
5PRESENT BY:HARDISH TRIVEDI
Types Of GTAW Power Source
• Inverter- DC
• Thyrester – DC
• Motor Generator – DC
• Rectifier – DC
• Transformer – AC (For Aluminium Welding Only)
6PRESENT BY:HARDISH TRIVEDI
Power Source
• Provides Electric Energy – Arc – Heat
• Drooping Characteristic
• OCV – Appx. 80V,
• Current Range 40 A to 300 A ( Capacity Of M/s)
• Arc Voltage 18V to 26V
7PRESENT BY:HARDISH TRIVEDI
Characteristic Of GTAW Power Source
A
Vertical Curve
V1
V2
A1 A2
Drooping – Constant Current
V
8PRESENT BY:HARDISH TRIVEDI
High Frequency Unit
• Provides High Voltage Electric Energy With Very high Frequency – 10000 Cycles / Sec.
• Initiates low energy Arc / Spark & Ionize Air Gap.
• Electrically charges Air Gap For welding Current to Jump Across the Tungsten Tip & BM to Form An Arc.
• HF Gets Cut Off, Once Welding Arc Struck.9PRESENT BY:HARDISH TRIVEDI
Water Cooling System
• Provides Cooling Water To Welding Torch.
• Cools Tungsten Rod, Torch handle & Welding Cable.
• Cooling Water Returns through Flexible Tube Which Carries welding cable within.
10PRESENT BY:HARDISH TRIVEDI
Pedal Switch
Sequence
When M/c On• Power source gets energized• Pump starts pumping cooling water to torch When Pedal Switch Pressed with tungsten rod held close to BM within 3mm• Solenoid valve opens, Argon starts flowing • After 5 seconds of pre-purging, high Frequency current jumps from tungsten
rod generating sparks • Immediately welding current makes arc across tungsten rod and work
through the HF sparks. • High frequency gets cut off from the system when welding arc is initiated and
welding is started. When Pedal Released without lifting the torch1 Current gets cut off, Arc extinguishes, Gas flow continues as post purging.2 Gas flow remains for few more seconds before it stops.3 Torch to be lifted only after post purging stops
12PRESENT BY:HARDISH TRIVEDI
Argon Gas Cylinder- Pressure Regulator + Flow Meter
• Cylinder Stores Argon At High Pressure
• Regulator Regulates Cylinder Pressure to Working Pressure
• Flow Meter Controls Flow Rate
Argon Cylinder
Flow Meter
Pressure Regulator
Flow Regulator
Pressure gauges
Cylinder Valve
Connection To Torch
13PRESENT BY:HARDISH TRIVEDI
Shielding Gas• Argon - Purity 99.99%
• Impure Argon Results In Porosities
• Purity Verified by Fusing BQ CS plate
• Leakage of Argon in Torch Results in Porosity.
• Check Leakage by Closing the Ceramic Cup With Thumb
14PRESENT BY:HARDISH TRIVEDI
Argon Gas Cylinder• Light Blue In Colour
• Full Cylinder Pressure: 1800 psi ( 135 Kgs / Cm2 )
• Volume Of Argon In Full Cylinder: 7.3 M3
• Commercial Argon (99.99%) Cost: Rs 90/- Per M3
• High Purity Argon (99.999) Cost: Rs 110/- Per M3
15PRESENT BY:HARDISH TRIVEDI
Back Purging
Purging Gas Commercial Argon or Nitrogen
• Applicable to Single Sided full penetration
• Prevents oxidation of root pass from opposite side of weld
• Essential for high alloy steels, nonferrous metals and alloys
• Desirable For All Material
Welding Torch
Root Pass
Purging Gas InPurging Gas Out
Purging chamber
Filler Wire
16PRESENT BY:HARDISH TRIVEDI
Tools For GTAW
• Head Screen
• Hand gloves
• Chipping Hammer
• Wire Brush
• Spanner Set
17PRESENT BY:HARDISH TRIVEDI
Tungsten Rod
• Non Consumable Electrode.
• Maintains Stable Arc
• Tip to be Ground to a cone Shape of 60º to 30º angle
• Thoriated Tungsten for General Application, Zerconiated Tungsten for Aluminium Welding
• Sizes :- 2, 2.4 & 3 mm Ø
Tungsten Rod
Ground to 50º ankle
18PRESENT BY:HARDISH TRIVEDI
Pulsed GTAW
• Power Source Provides Two different Current Levels“Background” and “Peak”at regular interval
• “Background” & “Peak” are above and below the Average Current
• Best Suitable for Full Penetration Open Root Pass Welding
• Ideal for Root Pass by Automatic Machine Welding
19PRESENT BY:HARDISH TRIVEDI
Filler Wire
• Added Separately to the weld pool.
• Compatible to base metal
• Used in cut length for manual welding.
• Used from layer wound spool for automatic welding.
• Sizes :- 0.8, 1, 1.2, 1.6, 2, 2.4 & 3 mm
20PRESENT BY:HARDISH TRIVEDI
ASME Classification Of Filler Wire
SS Filler Wire:
SFA-5.9, ER 308, 308L, 316, 316L, 347, 309
LAS Filler Wire:
SFA 5.28, ER 70S A1, ER 80S B2, ER90S D2,
ER 80S Ni2
CS Filler Wire:
SFA- 5.18 , ER 70S2 C = 0.07%, Mn = 0.9% – 1.4%, Si = 0.4 – 0.7%, P = 0.025%, S = 0.035%
21PRESENT BY:HARDISH TRIVEDI
Dos & Don'ts In GTAW
• Always Connect Electrode – Ve
• Keep Always Flow Meter Vertical
• Check & Confirm Argon Purity
• Clean Groove & Filler wire With Acetone
• Grind Tungsten Tip to Point
• Don’t Strike Arc With Electrode + Ve
• Don’t strike Arc Without Argon Flow
• Don’t Strike Arc By touching Tungsten Rod
• Don’t Touch Weld Pool With Tungsten Rod
• Don’t Lift and break Arc
Dos Don’ts
22PRESENT BY:HARDISH TRIVEDI
Dos & Don'ts In GTAW
• Break The Arc Only By Pedal Switch
• Lift The Torch only After 5 Sec Of Arc Break.
• Ensure Pre Purging & Post Purging of 5Sec
• Ensure Argon Flow & Water Circulation To Torch
• When Arc is Stopped Don’t Lift Torch immediately.
• Don’t Weld With Blunt Tungsten Rod
• Don’t Weld With Argon Leaking Torch
• Don’t Weld Without Water Circulation
Dos Don’ts
23PRESENT BY:HARDISH TRIVEDI
Dos & Don'ts In GTAW
• Provide Back Purging For Single Sided Full Penetration Welds
• Use N2 or Argon as Back Purging Gas For CS & LAS
• Use Argon As Back Purging Gas For SS & Non Ferrous Alloys
• Don’t Weld Single Sided Full Penetration Welds Without Back Purging
• Don’t Use N2 As Back Purging Gas For Non Ferrous Alloys
• Don’t Empty Ag Cylinders Fully.
Dos Don’ts
24PRESENT BY:HARDISH TRIVEDI
Defects In GTAW
1. Cracks 2. Lack Of Fusion
3. Porosity 4. Undercut
5.Lack Of Penetration 6. Excess Penetration
7.Overlap 8. Suck Back
9. Under Flush 10. Burn Through
11. Tungsten Inclusion 11.Stray Arcing
25PRESENT BY:HARDISH TRIVEDI
Crack
Cause Remedy
1) Wrong Consumable
2) Wrong Procedure
3) Improper Preheat
4) Inadequate Thickness In Root Pass
1) Use Right Filler Wire
2) Qualify Procedure
3) Preheat Uniformly
4) Add More Filler Wire in root Pass
crack
26PRESENT BY:HARDISH TRIVEDI
Lack Of Fusion
Cause Remedy
1) Inadequate Current
2) Wrong Torch angle
3) Improper bead placement
1) Use Right Current
2) Train /Qualify welder
3) Train/Qualify Welder
Lack Of Fusion
27PRESENT BY:HARDISH TRIVEDI
PorosityCause Remedy
1) Impure Argon Gas
2) Argon Leak Within Torch
3) Defective Filler Wire
4) Wet surface of BM
5) Rusted / Pitted Filler wire
6) Improper Flow Of Argon
1) Replace Argon Cylinder
2) Replace Leaking Torch
3) Replace Filler Wire
4) Clean & Warm BM
5) Clean Filler Wire
6) Provide Gas lens
Porosity . .
28PRESENT BY:HARDISH TRIVEDI
Undercut
Cause Remedy
1) Excess Current
2) Excess Voltage
3) Improper Torch angle
1) Reduce the Current
2) Reduce Arc length
3) Train & Qualify the Welder
Under cut
29PRESENT BY:HARDISH TRIVEDI
Lack Of Penetration*Cause Remedy
1) Excess Root Face
2) Inadequate Root opening
3) Over size Filler Wire
4) Wrong Direction of Arc
5) Improper bead placement
6) Improper weaving technique
1) Reduce Root Face
2) Increase Root Opening
3) Reduce Filler Wire size
4) Train / Qualify Welder
5) Train / Qualify Welder
6) Train & Qualify Welder
LOP
* Applicable to SSFPW
30PRESENT BY:HARDISH TRIVEDI
Excess Penetration*Cause Remedy
1)Excess root opening
2) Excess Current
3) Inadequate root face
4) Excess Weaving
5) Wrong Direction Of Arc
1) Reduce root gap
2) Reduce Current
3) Increase Root face
4) Train Welder
5) Train Welder
Excess Penetration
* Applicable to SSFPW
31PRESENT BY:HARDISH TRIVEDI
Overlap
Cause Remedy
1) Wrong Direction Of Arc
2) Inadequate Current
3) Excess Filler Wire
1) Train & Qualify Welder
2) Increase Current
3) Reduce Filler Metal
Overlap
32PRESENT BY:HARDISH TRIVEDI
Suck Back*Cause Remedy
1) Excess weaving in root
2) Excess Current
3) Inadequate root face
4) Wrong Electrode angle
1) Reduce weaving
2) Reduce Current
3) Increase root face
4) Train / Qualify Welder
Suck Back
* Applicable to SSFPW in 4G, 3G & 2G
33PRESENT BY:HARDISH TRIVEDI
Under flushCause Remedy
1) Inadequate weld beads in
final layer
2) Inadequate understanding on
weld reinforcement
3) Wrong selection of filler wire
size
1) Weld some more beads
in final layer
2) Train / Qualify welder
3) Train / Qualify Welder
Under flush
34PRESENT BY:HARDISH TRIVEDI
Burn through*Cause Remedy
1) Excess Current
2) Excess Root opening
3) Inadequate Root face
4) Improper weaving
1) Reduce the Current
2) Reduce root opening
3) Increase root face
4) Train / Qualify Welder
Burn trough
*Applicable to root pass
35PRESENT BY:HARDISH TRIVEDI
Tungsten InclusionCause Remedy
1) Ineffective HF
2) Improper Starting of Arc
3) Tungsten Tip Comes in
Contact With Weld
1) Rectify HF Unit
2) Never Touch Weld
With Tungsten Rod
3) Train / Qualify welder
Tungsten Inclusion
36PRESENT BY:HARDISH TRIVEDI
Stray Arcing
Cause Remedy
1) HF Not In Operation
2) Inadequate Skill of Welder
1) Rectify HF Unit
2) Train the Welder
Arc Strikes
37PRESENT BY:HARDISH TRIVEDI
Thanks
38PRESENT BY:HARDISH TRIVEDI