What is TIG welding?
Definition: TIG welding (also known as Gas Tungsten Arc Welding (GTAW)) is a type of welding process that uses non-consumable tungsten electrode to produce the weld. The heat is generated by an electric arc between the tungsten electrode and the workpiece.
During the TIG welding process, the tungsten electrode and the workpiece are shielded from the surrounding atmosphere using inert gas (like helium or argon).
(Note: Tungsten Inert Gas (TIG) welding process is also known as Gas Tungsten Arc Welding process or GTAW process)
Having discussed the definition of TIG welding, now further I have explained TIG welding process with its diagram and procedure (i.e How TIG welding works?)
So let’s begin with the procedure of TIG welding (or GTAW welding process (Gas Tungsten Arc Welding Process).
TIG welding procedure (or Gas Tungsten Arc Welding process)
TIG welding diagram is shown in the above image.
You can see all the major components of TIG welding (or GTAW welding process) labeled in the diagram itself.
TIG welding process (10 steps)
Follow these 10 steps TIG welding process to get your welding done.
Step 1: Select the electrode
Step 2: Prepare the electrode by properly grinding it
Step 3: Insert the tungsten electrode in the electrode holder
Step 4: Make the recommended settings on the TIG welder as per requirement
Step 5: Turn on gas cylinders
Step 6: Clean the workpiece surface
Step 7: Wear safety glasses, helmet, welding coat, etc
Step 8: Start welding the workpiece
Step 9: Close the valve of gas cylinder
Step 10: Turn off welder after welding is completed
Detailed explanation of TIG welding procedure
If you have read the above 10 steps of TIG welding, then you might have got the overview of the entire process. But there are lot more things to consider while welding using a TIG welder.
As shown in the above TIG welding diagram, the non-consumable tungsten electrode is used for TIG welding process.
The arc is maintained between this tungsten electrode and the workpiece which is to be welded.
What are tungsten electrodes made of?
These electrodes contain around 1% of zirconium or thorium. Generally the tungsten electrode containing zirconium is used for welding the workpiece by using an AC welding power source.
Tungsten electrodes alloyed with zirconium have good arc starting characteristics and they are also resistant to contamination.
The thoriated tungsten electrodes are generally preferred with DC welding source and they have high emissivity and good current carrying capacity.
Pure tungsten electrodes are prefered for welding of aluminum and magnesium with AC power source. Pure tungsten electrodes have lower current carrying capacity as compared to thoriated tungsten electrodes.
What is the purpose of shielding gas in TIG welding?
During the Tungsten Inert Gas welding process, the tungsten electrode, heat affected zone (HAZ), as well as the molten metal are shielded with the shielding gas, which protects them from atmospheric contamination.
You can see the inert gas shielding in the diagram above. The inert gas (usually argon or helium is used) enters the TIG welding torch from the gas cylinder (see the image shown in the beginning of this article).
The inert gases (i.e argon and helium) are chemically inert, meaning they do not react with the weld metal or any other gases.
These gases are also odourless and transparent, so they do not disturb the visibility of the arc.
In TIG welding process, sometimes hydrogen gas is added with the inert gases which helps in welding with higher travel speed.
TIG welding is used for …?
Gas Tungsten Arc Welding process (GTAW or TIG process) is generally used for welding of stainless steel, nickel alloys, titanium, aluminum, brass, bronze, magnesium as well as gold.
GTAW process is also used for welding of dissimilar metals like copper with brass, stainless steel with mild steel.
What should be the dimensions of tungsten electrode?
Tungsten electrodes used in TIG welding are somewhat expensive, but the advantage is that it can be used for a very long time.
It is also necessary to have the proper sharpness of the tungsten electrode to achieve good quality welds.
The recommended dimensions of the tungsten electrode is mentioned in the diagram below.
What are the effects of different shielding gases on TIG welding?
Different shielding gases and their effects are mentioned in the table below.
|Characteristics||Argon||Helium||Argon + Helium|
|Travel speed||Reduced travel speed||Faster travel speed||Depends on mixture, more helium – more travel speed|
|Penetration||Reduced penetration||Increased penetration||Depends on mixture, more helium – improved penetration|
|Cleaning||Good cleaning action||Less cleaning action||Cleaning properties closer to argon|
|Arc starting||Easier arc starting||Difficult arc starting||Depends on mixture, more argon – more easier arc starting|
|Arc stability||Good arc stability||Lower arc stability at lower current||Depends on mixture, more argon – more stable arc|
|Arc voltage||Lower arc voltage||Higher arc voltage||Moderate arc voltage|
|Flow rate||Lower flow rate||Higher flow rate||Higher flow rate than argon|
|Cost||Lower cost and greater availability||Higher cost than argon||Comparatively higher cost due to argon|
TIG welding voltage and current range
The Tig welding voltage range is between 10-15 V with the current range between 50-350 amps for argon shielding.
While for helium shielding, the voltage range is 15-25 V with current range of 50-250 amps.
Why is tungsten electrode used in TIG welding?
Tungsten is a metal which has a high melting point (3410 °C).
Also tungsten is a strong emitter of electrons which provides the path to the arc, and helps in maintaining the stable arc.
TIG welding equipments
TIG welding equipment are listed below.
- Welding torch
- Tungsten electrode
- Filler material
- Power source
- Inert gas cylinder, pressure regulator and flow regulator
- Solenoid valve
Having said that, now let’s discuss the Advantages and Disadvantages of Tungsten Inert Gas welding (TIG welding).
Advantages of Tig welding (GTAW)
The advantages of gas tungsten arc welding are mentioned below.
- The arc produced by tungsten electrode is highly concentrated which results in very narrow heat affected zone (HAZ).
- There is no use of welding flux in TIG welding process. So the slag formation does not take place.
- If the welding metal is free of contaminants, then there will be no issue of weld spatter.
- Very less fumes are produced in GTAW process as compared to other welding process like stick welding.
- Various types of metals (including similar metals and dissimilar metals) can be joined by using Tig welding process.
- Tig welding is suitable for welding metals having less thickness (from 1 mm to 7 mm).
Disadvantages of Tig welding (GTAW)
Disadvantages of gas tungsten arc welding are mentioned below.
- The arc travel speed is slower than stick welding process.
- Deposition rate of the filler metal (or filler rod) is also low.
- The coordination of hand and eye is very important and it requires a skilled welder.
- The UV rays produced in TIG welding are brighter than other welding process.
- The cost of equipments are higher. Also the cost of tungsten electrode is higher.
- During the Tig welding procedure, if filler metal comes out of the shielding atmosphere, then it may cause weld metal contamination.
TIG welding: Image by Prowelder87, CC BY-SA 4.0, via Wikimedia Commons
Gas tungsten arc welding procedure: Image by Duk, CC BY-SA 3.0, via Wikimedia Commons and Spanginee derivative work: Malyszkz, Public domain, via Wikimedia Commons
Tungsten electrode image credit: India Mart