Gas Tungsten Arc Welding

Gas Tungsten Arc Welding By HARDISH TRIVEDI

PRESENT BY:HARDISH TRIVEDI

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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 PRESENT BY:HARDISH TRIVEDI

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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 PRESENT BY:HARDISH TRIVEDI

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Equipment & Accessories Pressure Regulator Flow Meter Tungsten Rod Argon Gas In Cooling Water In

Solenoid Valve

Collet

Argon Cylinder

Gas Lens Ceramic Cup Arc

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Welding Cable & Cooling Water In Tube Cooling Water Out Argon Shielding

Work Pedal Switch

HF Unit & Water Cooling System

High Frequency Connection

Power Source PRESENT BY:HARDISH TRIVEDI

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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

PRESENT BY:HARDISH TRIVEDI

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Types Of GTAW Power Source • Inverter- DC • Thyrester – DC • Motor Generator – DC • Rectifier – DC • Transformer – AC (For Aluminium Welding Only)

PRESENT BY:HARDISH TRIVEDI

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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

PRESENT BY:HARDISH TRIVEDI

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Characteristic Of GTAW Power Source Drooping – Constant Current V V1 V2

Vertical Curve

A1 A2 PRESENT BY:HARDISH TRIVEDI

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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. PRESENT BY:HARDISH TRIVEDI

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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.

PRESENT BY:HARDISH TRIVEDI

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GTAW TORCH

Torch Handle

Cap with collet For Holding Tungsten

Cooling Water Outlet Argon Gas Inlet

Cooling Water Inlet Tube with cable Ceramic Cup Argon Shielding Gas

Tungsten Rod

Base Metal Earthing Cable

Arc PRESENT BY:HARDISH TRIVEDI

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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 torch 1 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 PRESENT BY:HARDISH TRIVEDI

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Argon Gas Cylinder- Pressure Regulator + Flow Meter

Cylinder Valve Pressure gauges Flow Meter Flow Regulator

• Cylinder Stores Argon At High Pressure • Regulator Regulates Cylinder Pressure to Working Pressure

Pressure Regulator Connection To Torch

• Flow Meter Controls Flow Rate

Argon Cylinder PRESENT BY:HARDISH TRIVEDI

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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 PRESENT BY:HARDISH TRIVEDI

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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 PRESENT BY:HARDISH TRIVEDI

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Back Purging Purging Gas Commercial Argon or Nitrogen Filler Wire

Purging Gas Out

Welding Torch

Purging Gas In Purging chamber

Root Pass

• 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

PRESENT BY:HARDISH TRIVEDI

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Tools For GTAW • Head Screen • Hand gloves • Chipping Hammer • Wire Brush • Spanner Set PRESENT BY:HARDISH TRIVEDI

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Tungsten Rod

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

Ground to 50º ankle

• Sizes :- 2, 2.4 & 3 mm Ø PRESENT BY:HARDISH TRIVEDI

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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 PRESENT BY:HARDISH TRIVEDI

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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 PRESENT BY:HARDISH TRIVEDI

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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%

PRESENT BY:HARDISH TRIVEDI

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Dos & Don'ts In GTAW Dos

Don’ts

• 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

PRESENT BY:HARDISH TRIVEDI

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Dos & Don'ts In GTAW Dos

• 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

Don’ts

• 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

PRESENT BY:HARDISH TRIVEDI

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Dos & Don'ts In GTAW Dos

• 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’ts • 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.

PRESENT BY:HARDISH TRIVEDI

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Defects In GTAW 1. Cracks 3. Porosity 5.Lack Of Penetration 7.Overlap 9. Under Flush 11. Tungsten Inclusion

2. Lack Of Fusion 4. Undercut 6. Excess Penetration 8. Suck Back 10. Burn Through 11.Stray Arcing

PRESENT BY:HARDISH TRIVEDI

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Crack 1) 2) 3) 4)

Cause Wrong Consumable Wrong Procedure Improper Preheat Inadequate Thickness In Root Pass

1) 2) 3) 4)

Remedy Use Right Filler Wire Qualify Procedure Preheat Uniformly Add More Filler Wire in root Pass

crack

PRESENT BY:HARDISH TRIVEDI

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Lack Of Fusion Cause Remedy 1) Inadequate Current 1) Use Right Current 2) Wrong Torch angle 2) Train /Qualify welder 3) Improper bead placement 3) Train/Qualify Welder

Lack Of Fusion

PRESENT BY:HARDISH TRIVEDI

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Porosity Cause 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

Porosity

Remedy 1) Replace Argon Cylinder 2) Replace Leaking Torch 3) Replace Filler Wire 4) Clean & Warm BM 5) Clean Filler Wire 6) Provide Gas lens

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PRESENT BY:HARDISH TRIVEDI

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Undercut Cause 1) Excess Current 2) Excess Voltage 3) Improper Torch angle

Remedy 1) Reduce the Current 2) Reduce Arc length 3) Train & Qualify the Welder

Under cut

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Lack Of Penetration* Cause 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

Remedy 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

* Applicable to SSFPW

PRESENT BY:HARDISH TRIVEDI LOP

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Excess Penetration* Cause 1)Excess root opening 2) Excess Current 3) Inadequate root face 4) Excess Weaving 5) Wrong Direction Of Arc

1) 2) 3) 4) 5)

Remedy Reduce root gap Reduce Current Increase Root face Train Welder Train Welder

* Applicable to SSFPW

Excess PenetrationPRESENT BY:HARDISH TRIVEDI

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Overlap Cause 1) Wrong Direction Of Arc 2) Inadequate Current 3) Excess Filler Wire

Remedy 1) Train & Qualify Welder 2) Increase Current 3) Reduce Filler Metal

Overlap

PRESENT BY:HARDISH TRIVEDI

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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

* Applicable to SSFPW in 4G, 3G & 2G

Suck Back

PRESENT BY:HARDISH TRIVEDI

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Under flush Cause

Remedy

1) Inadequate weld beads in 1) Weld some more beads final layer in final layer 2) Inadequate understanding on 2) Train / Qualify welder weld reinforcement 3) Wrong selection of filler wire 3) Train / Qualify Welder size

Under flush

PRESENT BY:HARDISH TRIVEDI

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Burn through* Cause 1) Excess Current 2) Excess Root opening 3) Inadequate Root face 4) Improper weaving

Remedy 1) Reduce the Current 2) Reduce root opening 3) Increase root face 4) Train / Qualify Welder

*Applicable to root pass Burn trough

PRESENT BY:HARDISH TRIVEDI

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Tungsten Inclusion Cause

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

PRESENT BY:HARDISH TRIVEDI

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Stray Arcing Cause Remedy 1) HF Not In Operation 1) Rectify HF Unit 2) Inadequate Skill of Welder 2) Train the Welder Arc Strikes

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Thanks

PRESENT BY:HARDISH TRIVEDI

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