PRESENTATIONWORKSHOP TECHNOLOGY 2

JJ204GROUP MEMBERS

KATHIRAVAN S/O PARAMASIWANNAAVINDRA PRASAD S/O GANESAN

SIM KAH TIANG

INTRODUCTION GAS SHIELDED ARC WELDING

The primary goal of any welding operation is to make a weld that has the same properties as the base metal.

The only way to produce such-a weld is to protect the molten puddle from the atmosphere

The two general types of gas shielded-arc welding processes are gas tungsten-arc welding (GTA) and gas metal-arc welding (GMA).

GTA is often tilled TIG (tungsten inert gas) and GMA is referred to

as MIG(metal inert gas).

The term inert refers to a gas that will not combine chemically with other elements

GAS SHIELDED ARC WELDING PRINCIPLE

TUNGSTEN INERT GAS

Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding

Is an arc welding process that uses a non-consumable tungsten electrode to produce the weld

Enables the metals and wide range of ferrous alloys to be welded without the use of flux

The weld area is protected from atmospheric contamination by an inert shielding gas (argon or helium)

GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminum, magnesium, and copper alloys

METAL INERT GAS

• Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) welding or metal active gas (MAG) welding

• Is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt, and join

• Is a process which suitable for welding aluminium,magnesium alloys,plain and low alloy steels,stainless and heat-resistant steel,copper and bronze

• The process can be semi-automatic or automatic

DIFFERENCE BETWEEN GAS SHIELDED ARC WELDING

AND

NORMAL ARC WELDING

ARC WELDING

• Arc welding is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point

• They can use either direct (DC) or alternating (AC) current,

GAS SHIELDED ARC WELDING

• Shielding gases are inert or semi-inert gases that are commonly used in several welding processes

• Inert gases:helium,argon Semi-inert:oxygen,carbon dioxide,hydrogen,nitrogen

• Their purpose is to protect the weld area from oxygen, and water vapour.

• Depending on the materials being welded, these atmospheric gases can reduce the quality of the weld or make the welding more difficult

• Other arc welding processes use other methods of protecting the weld from the atmosphere as well

Shielded metal arc welding (SMAW) - also known as "stick welding", uses an electrode that has flux, the protectant for the puddle, around it. The electrode holder holds the electrode as it slowly melts away. Slag protects the weld puddle from the outside world.

Gas tungsten arc welding (GTAW) - also known as TIG (tungsten, inert gas), uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas such as Argon or Helium.

Gas metal arc welding (GMAW) - commonly termed MIG (metal, inert gas), uses a wire feeding gun that feeds wire at an adjustable speed and sprays an argon-based shielding gas or a mix of argon and carbon dioxide (CO2) over the weld puddle to protect it from the outside world.

METHOD OF WELDING FORTIG WELDING

1.Put on safety

gear

2.Connect the TIG

torch

3.Plug your foot

pedal into the machine

4.Select the polarity.

5.Grind the tungsten

6.Set up the gas flow.

7.Set the amperage

8.Clean your

welding material

9.Insert the tungsten

electrode into its collet

10.Clamp the

parts together

11.Tack weld the parts together

12.Hold the TIG torch in your

hand

15.Use your torch to heat up the

base metal

13.Practice using the foot pedals to control the

heat

14.Pick up the filler rod in your other

hand

METHOD OF WELDING FOR MIG WELDING

1.Assemble

your safety gear

2.Select a

comfortable MIG gun

3.Prepare the area to be welded in

4.Obtain the proper wire

5.Prepare the reel

6.Feed the wire to the torch

7.Adjust the

tension

8.Set the welding

machine polarity to

DCEP.

9.Keep a

consistent electrode

length

10.Use the proper

shielding gas

11.Weld a joint using a drag or push

welding technique.

EXAMPLE OF TIG WELDING MACHINE

EXAMPLE OF MIG WELDING MACHINE

Shielding gases for MIG welding

• The basic gas for MIG welding is inert – argon (Ar) or helium (He), or a mixture of both.

• However, small additions of oxygen (O2) or carbon dioxide (CO2) can further stabilize the arc, improve the fluidity and also improve the quality of the weld deposit.

• For stainless steels there are also gases available containing small amounts of hydrogen (H2).

Shielding gases for TIG

• The normal gas for TIG welding is argon or helium, or a mixture.

• In some cases nitrogen (N2) and/or hydrogen (H2) is added in order to achieve special properties.

• For instance, an addition of hydrogen can be used for many conventional stainless steels to increase productivity.

• Alternatively, if nitrogen is added, the weld deposit properties can be improved.

• Oxidizing additions are not used because they destroy the tungsten electrode.

TYPES OF CURRENT

• Both direct current (DC) and alternating current (AC) are used for welding.

• The form of the weld pool and of the weld seam can be influenced by current type and electrode polarity.

EFFECTS OF POLARIITY

• Direct current, straight polarity (electrode negative, DC-EN) → deep penetration

• Direct current, reverse polarity (electrode positive, DC-EP) → low penetration

• Alternating current (AC) → medium penetration

Thus there are three possibilities for welding:• 1.DC-EP The welding current has to be

reduced 10% of the normal welding current

• 2.DC-EN Pure helium is required as a shielding gas and no reduction of the welding current is necessary

• 3.AC The current is required to be reduced to 50-60% of the normal current

ADVANTAGES OF TUNGSTEN INERT GAS WELDING

• Tungsten Inert Gas Welding produces high quality welds.

• The weld is automatically protected by the inert gas during the welding process.

• No slag is produced.

• TIG Welding can be done in any position.

DISADVANTAGES OF TUNGSTEN INERT GAS WELDING

• Tungsten inert gas welding is a slow process.

• Highly skilled labour is needed.

• Welder is exposed to huge intensities of light

.

• TIG welding is more expensive when compared to MIG welding

ADVANTAGESOFMETAL INERT GASWELDING

• Simple to use MIG welding is a simple process. In just a few hours,

welders will be able to learn how to MIG weld. As a matter of fact, the basic MIG welding training can only last for 20 minutes.

• Increases productivity A lot of welders have improved productivity with the

use of MIG welding. They don’t need to regularly change rods or even repeatedly brush the weld. As a result, they will able to work faster and in a cleaner way.

• Great and Simple Welds MIG welding offers better weld pool visibility. The

welding process is very simple and gives you better control. As a result, you will be able to produce a great looking weld.

• Versatile MIG welding has the ability to weld various types of

alloys and metals. You can operate it in a fully automatic or semi automatic way. As a matter of fact, a lot of industries are benefitting a lot from the use of MIG welding. It is used for various metals like copper, mild steel, aluminum, nickel, magnesium, mild steel, and many more.

• Efficient welding MIG welding does not only improve the welding speed,

but it as well improves the quality and overall weld control.

• Cleanliness and efficiency With the use of MIG welding, the loss of alloying

elements will be reduced and minor weld spatter is produced.

DISADVANTAGES OFMETAL INERT GASWELDING

• Expensive MIG welding is actually more expensive primarily

because of the complexity of usage. The frequent replacement of nozzles can actually add up to the total cost.

• Not recommended for outdoor welding MIG welders are highly discouraged to work outside

because MIG welding uses shielding gas and welding outside can actually affect the purity of the weld. The wind outside can compromise the quality of the weld.

• Fast Cooling Rates MIG welding is not covered with slag and so you can

expect that the welded metal will cool at higher rates

• Not recommended for welding thick metals One of the limitations of MIG welding is its

inability to weld thick metals. Because of the property of thick metals, MIG weld will not be able to penetrate deeply. It is only advisable to use in thin metals.

• The use of shielding gas Replacing the shielding gas may actually take

some time and can cause delay while welding.

• Longer preparation time When welding using MIG, the metal should be

prepared thoroughly. The metal should be free from dirt and rust to ensure high quality welding.

DEFECTS OFTUNGSTEN INERT GAS WELDINGANDMETHOD TOPREVENT IT

POOR GAS COVERAGE LEADS TO CONTAMINATION

Weld contamination can occur when shielding gas is not turned on, there is too little or too much gas shielding or the gas is blown away

Check the gas cylinder label to make sure you’re using the right type of gas for TIG welding (generally 100 percent argon, or an argon/helium mix for aluminum)

Consider using a gas lens instead of the standard collet body to provide better gas shielding.

Check all fittings and hoses for leaks. Use a gas leak detection fluid, available at most welding suppliers, over the hose and all fittings. If bubbles form, you have a leak and need to replace defective components.

• SUGARING ON STAINLESS Sugaring (oxidation) occurs around the weld

when it is exposed to oxygen in the air. The best way to prevent sugaring is to ensure you have adequate gas coverage on the front and back of the weld and to be sure that you do not overheat the weld.

• TOO MUCH AMPERAGE ON ALUMINUM Setting the amperage too high on aluminum

creates a wider profile, an ill-defined bead and can potentially lead to burn-through. To solve this problem, reduce amperage and/or increase travel speed.

• CRATERS Craters occur at the end of the weld and lead to

cracking. Causes include instantly dropping the weld power and removing the filler rod too quickly. Adjust your technique and continue to feed the filler rod while slowly reducing current at the end to fill in the crater. Using a TIG welder with a “crater control” function may also help.

• DIRTY BASE AND/OR FILLER METAL All base and filler metals need to be cleaned, whether

it’s mill scale, oxide on aluminum, or dirt and grease. Grind, brush and wipe away all potential contaminants. For cleaning aluminum, dedicate a stainless steel brush to the task to prevent contamination from other metals. Never use brake cleaner!

DEFECTS OF METAL INERT GAS WELDINGAND METHODS TOPREVENT IT

Porosity Gas flow too low or too high Blocked nozzle Leaking gas lines Draughty conditions Nozzles distance from work is too great Painted, wet or oily plate Wet or rusty electrode/wire

Lack of penetration -Current too low Preparation too narrow Root face too large Root gap too small Worn contact tip causing irregular arc Incorrect alignment of plates

Undercut -Speed too fast

• Current too high

• Poor technique

Lack of fusion -Voltage too low

• Current too low or too high

• Irregular surface

• Wrong torch angle

THANK YOU