Welding All

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Welding



• Welding is a materials joining process which prcoalescence of materials by heating them to stemperatures with or without the application of pres

by the application of Heat alone, and with or withoutof filler material. . Heat may be obtained by chreaction, electric arc, electrical resistance, frictionasound and light energy. If no filter metal is usedwelding then it is termed as Autogenous Welding Proc

• Welding is used for making permanent joints.

• It is used in the manufacturing of automobile bodies, aircraftrailway wagons, machine frames, structural works, tanks, fboilers, general repair work and ship building.



Subsequently other developments are as follows:

• Thermit Welding (1903)

• Arc Stud Welding (1918)

• Seam Welding of Tubes (1922)

• Mechanical Flash Welder for Joining Rails (1924)

• Extruded Coating for MMAW Electrodes (1926)

• Submerged Arc Welding (1935)

• Air Arc Gouging (1939)

• Inert Gas Tungsten Arc (TIG) Welding (1941)

• Iron Powder Electrodes (1944)

• Inert Gas Metal Arc (MIG) Welding (1948)

• Electro Slag Welding (1951)



• Flux Cored Wire with CO 2 Shielding (1954)

• Electron Beam Welding (1954)

• Constricted Arc (Plasma) for Cutting (1955)

• Friction Welding (1956)

• Plasma Arc Welding (1957)

• Electro Gas Welding (1957)

• Short Circuit Transfer for Low Current, Low Voltage Welding with CO2

Shielding (1957)

• Vacuum Diffusion Welding (1959)

• Explosive Welding (1960)

• Laser Beam Welding (1961)

• High Power CO2 Laser Beam Welding (1964)



Advantages of welding

• A good weld is as strong as the base metal.

• General welding equipment is not very costly.

• Portable welding equipment's are available.

• A large number of metals/alloys both similar and dissimilar can bewelding.



Disadvantages of welding

• Welding gives out harmful radiations (light), fumes and spatter.

• Welding results in residual stresses and distortion of the work pieces.

• Jigs and fixtures are generally required to hold and position the parts to welded.

• Edge preparation of the work pieces is generally required beforwelding them.

• A skilled welder is a must to produce a good welding job.



Choice of welding process



GAS WELDING

• Gas welding process was introduced in 1903.

• Gas welding is a fusion welding process.

• It join metals, using the heat of combustion of an oxygen/air anfuel gas (i.e. acetylene, hydrogen, propane or butane) mixture.

• Intense heat (flame) thus produces melts and fuses together theedges of the parts to be welded, with addition of a filler metal.

• Oxy-acetylene flame temp 3480 degree Celsius



Oxyfuel Gas Welding (OFW)

Group of fusion welding operations that burn various fuels moxygen

• OFW employs several types of gases, which is the primary damong the members of this group

• Oxyfuel gas is also used in flame cutting torches to cut and s

metal plates and other parts• Most important OFW process is oxyacetylene welding



Fuels

• Propane (LPG) C3H8

• Natural Gas CH4

• Acetylene C2H2

• MAPP (Methylacetylene-propadiene)

• Hydrogen



Oxyacetylene Welding (OAW)

Fusion welding performed by a high temperature flame fromcombustion of acetylene and oxygen

• Flame is directed by a welding torch

• Filler metal is sometimes added

• Composition must be similar to base metal

• Filler rod often coated with flux to clean surfaces and prevent o



Oxyacetylene Welding



Acetylene (C2H2)

• Most popular fuel among OFW group because it is capable otemperatures than any other

• Up to 3480C (6300F)

• Two stage reaction of acetylene and oxygen:

• First stage reaction (inner cone of flame)

C2H2 + O2 2CO + H2 + heat

• Second stage reaction (outer envelope)

2CO + H2 + 1.5O2 2CO2 + H2O + heat



• Maximum temperature reached at tip of inner cone, while outeenvelope spreads out and shields work surface from atmospher

• Shown below is neutral flame of oxyacetylene torch indicatingtemperatures achieved

Oxyacetylene Torch



GAS WELDING EQUIPMENT...

1. Gas Cylinders

Pressure

Oxygen – 125 kg/cm2

Acetylene – 16 kg/cm2

2. Regulators

Working pressure of oxygen 1 kg/cm2

Working pressure of acetylene 0.15 kg/cm2

Working pressure varies depends upon the thickness of the wor

pieces welded.3. Pressure Gauges

4. Hoses

5. Welding torch

6. Check valve

7. Non return valve



Oxy Acetylene welding



TypicalPortableOxygen/ Fuel

Cutting Rig



Green = Oxyg

Red = Fuel



Typical Cutting Torch



TYPES OF FL MES…

• Oxygen is turned on, flame immediately changes into a long white innerarea (Feather) surrounded by a transparent blue envelope is calledCarburizing flame (30000c)

• Addition of little more oxygen give a bright whitish cone surrounded by ttransparent blue envelope is called Neutral flame (It has a balance of fuegas and oxygen) (32000c)

• Used for welding steels, aluminium, copper and cast iron

• If more oxygen is added, the cone becomes darker and more pointed, wthe envelope becomes shorter and more fierce is called Oxidizing flame

• Has the highest temperature about 34000c

• Used for welding brass and brazing operation



Three basic types of oxyacetylene flames used in oxyfuel-gas welding and cuttingoperations: (a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing flam



Three basic types of oxyacetylene flames used in oxyfuel-gas welding a

cutting operations:

(a) neutral flame; (b) oxidizing flame; (c) carburizing, or reducing flame.



Gas Welding Techniques

1. Fore hand Welding 2. Back hand welding



1. Fore hand Welding



2. Back hand welding

Ad f ldi



Advantages of gas welding

• It is probably the most versatile processes. It can be appliedwide variety of manufacturing and maintenance situations.

• Since the sources of heat and of filler metal are separate, the whas control over filler- metal deposition rates.

• The equipment is versatile, low cost, self- sufficient and us portable.

• The cost and maintenance of the welding equipment is low wcompared to that of some other welding processes.

Disadvantages



Disadvantages• Heavy sections cannot be joined economically.

• Flame temp is less than the temp of the arc.

• Fluxes used with certain welding and brazing opera produce fumes that are irritating to the eyes, nose, thand lungs.

• Refractory metals (e.g., tungsten, molybdenum, tantaetc.) and reactive metals (e.g., titanium and zirconium)not be gas welded.

• More safety problems are associated with the handlingstoring of gases.



Arc Welding (AW)

• A fusion welding process in which coalescence of the metalsachieved by the heat from an electric arc between an electrthe work

• Electric energy from the arc produces temperatures ~ 10,00C), hot enough to melt any metal

• Most AW processes add filler metal to increase volume and of weld joint



What is an Electric Arc?

• An electric arc is a discharge of electric current across a gap

circuit

• It is sustained by an ionized column of gas ( plasma) throughthe current flows

• To initiate the arc in AW, electrode is brought into contact wand then quickly separated from it by a short distance



• A pool of molten metal is formed near electrode tip

and as electrode is moved along joint, molten weldpool solidifies in its wake

Arc Welding

M l A W ldi



Manual Arc Weldingand Arc Time• Problems with manual welding:

• Weld joint quality• Productivity

• Arc Time = (time arc is on) divided by (hoursworked)

• Also called “arc-on time”

• Manual welding arc time = 20%• Machine welding arc time ~ 50%



Two Basic Types of AW Electrodes

• Consumable – consumed during welding process

• Source of filler metal in arc welding• Nonconsumable – not consumed during welding

process

• Filler metal must be added separately if it is added



Consumable Electrodes

• Forms of consumable electrodes

• Welding rods (a.k.a. sticks) are 9 to 18 inches and 3/8 inch or less iand must be changed frequently

• Weld wire can be continuously fed from spools with long lengths oavoiding frequent interruptions

• In both rod and wire forms, electrode is consumed by the ar

added to weld joint as filler metal



Nonconsumable Electrodes

• Made of tungsten which resists melting

• Gradually depleted during welding (vaporization is principalmechanism)

• Any filler metal must be supplied by a separate wire fed intopool



Arc Shielding

• At high temperatures in AW, metals are chemically reactive t

nitrogen, and hydrogen in air• Mechanical properties of joint can be degraded by these reactions

• To protect operation, arc must be shielded from surrounding air inprocesses

• Arc shielding is accomplished by:

• Shielding gases, e.g., argon, helium, CO2

• Flux



Flux

A substance that prevents formation of oxides and other cont

in welding, or dissolves them and facilitates removal

• Provides protective atmosphere for welding

• Stabilizes arc

• Reduces spattering



Various Flux Application Methods

• Pouring granular flux onto welding operation

• Stick electrode coated with flux material that melts during wcover operation

• Tubular electrodes in which flux is contained in the core andas electrode is consumed



Power Source in Arc Welding

• Direct current (DC) vs. Alternating current (AC)

• AC machines less expensive to purchase and operate, but generallto ferrous metals

• DC equipment can be used on all metals and is generally noted forcontrol

Consumable Electrode



Consumable ElectrodeAW Processes

• Shielded Metal Arc Welding

• Gas Metal Arc Welding

• Flux-Cored Arc Welding

• Electrogas Welding

• Submerged Arc Welding

Arc Welding Electrical Terms



Arc Welding Electrical Terms

1. Electrical Circuit

2. Direct current (DC)

3. Alternating current (AC)

4. Ampere

5. Volt

6. Resistance

7. Ohms Law

8. Constant potential

9. Constant current

10. Voltage drop

11. Open circuit voltage

12. Arc voltage

13. Polarity

14. Watt

To understand how an electric arc welder produces the correct hea

for arc welding, you must understand the following fourteen (14)

electrical terms.

Terms



Terms1 - Electrical Circuit

• An electrical circuit is a completepath for electricity.

• Establishing an arc completes anelectric circuit .

Current will not flow through an open circuit.

2 Di C



2 - Direct Current

• Direct current: A type

of current where theflow of electrons is in

one direction.

• In arc welding the direction

of flow is called the polarity.



3 - Alternating Current

• Alternating current: The type

of current where the flow ofelectrons reverses direction

at regular intervals.

4 Ampere



4 - Ampere

• Amperes: the unit of measure for current flow.

• One ampere is equal to 6.24150948×1018

electrons passing by a point per second.

• Electricity passing through a resistance causesheat.

• An air gap is a high resistance

Arc welding requires large electrical currents 100-1000A.

5 V lt



5 - Voltage

• Voltage is the measure of

electromotive force (Emf).

• Emf is measured in units of volts

• The voltage at the electrode for MAW

determines the ease of starting and

the harshness of the arc.



6 - Resistance

• Resistance is the characteristic of a material that

impedes the flow of an electrical current.• Measured in units of Ohm’s ( )

• When an electrical current passes through a resistanceheat is produced.

7 Ohm’s Law



7 - Ohm s Law

• Commonly expressed as:• Voltage is equal to amps x

resistance

• For arc welding rearrangedas:• Amperage is the voltage

divided by the resistance.

E = I R

I =E

R

8 Constant Potential



8 - Constant Potential

A constant potential power supply is designed to produca relatively constant voltage over a range of amperagechanges.

Primarily used forGMAW

FCAW

Constant Current



• In a constant current power supply, the current (amperage)

stays relatively constant over a narrow range of voltages.

• Primarily used for:

SMAW

TIG

10 V l D



10 - Voltage Drop

• Voltage drop is the reduction in voltage in an electrical circuibetween the source and the load.

• Primary cause is resistance.

• Excessive voltage drop reduces the heat of the arc.

11 O Ci it V lt



11 - Open Circuit Voltage

• Open circuit voltage is the potential voltage between theelectrode and the work when the arc is not present.

• The higher the OCV the easier the arc is to start.

• The higher the OCV the steeper the volt – amp curve.

12 Arc Voltage



12 - Arc VoltageArc voltage is the electrical potential between the electrodeand the metal after the arc has started.

The arc voltage depends only upon the arc length

V = k1 + k2l Volts

Where l is the arc length in mm and k1 and k2 are constants,

k1 = 10 to 12; and k2 = 2 to 3

The minimum Arc voltage is given by

Vmin = (20 + 0.04 l) Volt

13 - Polarity



y

Polarity (positive & negative) is present in all electrical circuits.

Electricity flows from negative to positive

Controlling the polarity allows the welder to influence the locatio

of the heat.When the electrode is positive (+) it will be slightly hotter than thebase metal.

When the base metal is positive (+) the base metal will be slightly hotter

than the electrode.

What abbreviations are used to indicate the polarity of the electrode?

DCEN or DCSP [direct current electrode negative or direct current straigh

polarity]

DCEP or DCRP [direct current electrode positive or direct current reverse

polarity]



Arc welding equipment's

1. Droppers: Constant current welding machines

Good for manual welding

2. Constant voltage machines

Good for automatic welding

5



14 - Watt

Watts are a measure of the amount of electrical energy beingconsumed.

Watts = Volts x Amps

The greater the Watts of energy flowing across an air gap thegreater the heat produced.

Power to drive the operation is the product of the current I passinthrough the arc and the voltage E across it.

This power is converted into heat, but not all of the heat istransferred to the surface of the work.

Convection, conduction, radiation, and spatter account for lossesthat reduce the amount of usable heat

Arc Welding Power Supplies



The type of current and the polarity of the weldingcurrent are one of the differences between arcwelding processes.

• SMAW Constant current (CC), AC, DC+ or DC-

• GMAW Constant voltage (CV) DC+

• FCAW Constant voltage (CV) DC-

• GTAW Constant Current (CC) ), AC, DC+ or DC-

1: AmperageOutput



Output• The maximum output of the power

supply determines the thickness ofmetal that can be welded before

joint beveling is required.

• 185 to 225 amps is a common size.

• Welding current depends upon: thethickness of the welded metal,type of joint, welding speed,position of the weld, the thicknessand type of the coating on theelectrode and its working length.

• Welding current, I = k. d, amperes;d is dia. (mm)

2: Duty cycle



• The amount of continuous welding time a powersupply can be used is determined by the duty cycleof the power supply.

• Duty cycle is based on a 10 minute interval.

• Many power supplies have a sloping duty cycle.

2: Duty cycle



The percentage of time in a 5 min period that a weldingmachine can be used

at its rated output without overloading.

Time is spent in setting up, metal chipping, Cleaning andinspection.

For manual welding a 60% duty cycle is suggested and foautomatic welding

100% duty cycle.

6

Atomic hydrogen welding



An a.c. arc is formed between two tungsten electrodes along which streams hydrogen are fed to the welding zone.

The molecules of hydrogen are dissociated by the high heat of the arc in the

between the electrodes.

The formation of atomic hydrogen proceeds with the absorption of heat:

This atomic hydrogen recombines to form molecular hydrogen outside the aparticularly on the relatively cold surface of the work being welded,

releasing the heat gained previously:

6



Atomic hydrogen welding

T t f b t 3700 ˚C



• Temperature of about 3700 ˚C.

• Hydrogen acts as shielding also.

• Used for very thin sheets or small diameter wires.

• Lower thermal efficiency than Arc welding.

• Ceramics may be arc welded.

• AC used.

6



THERMIT WELDING

It is a process in which a mixture of aluminum powder and a metal oxid

called Thermit is ignited to produce the required quantity of molten m

By an exothermic non violent reaction .



Arc Welding processes

MIG



• GMAW stands for Gas Metal Arc Welding

• GMAW is commonly referred to as MIG or Metal Inert Gas w• During the GMAW process, a solid metal wire is fed through

gun and becomes the filler material

• Instead of a flux, a shielding gas is used to protect the moltefrom the atmosphere which results in a weld without slag

GMAW Equipment



• Power Supply

• Wire Feeder

• Electrical mechanical device that feed required amount of filler maconstant rate of speed

GMAW Equipment



• Welding filler electrode

• Small diameter consumable electrode that is supplied to the weldthe roller drive system

• Shielding Gas

• Gas used to protect the molten metal from atmospheric contamin

• 75%Argon (inert gas) & 25% Carbon Dioxide most common gas used for GM



GMAW Components



• Let’s look a little closer at the GMAW proces

Travel direction

Electrode

1Arc2

Weld Puddle

3

Shielding Gas4

5Solidified Weld Metal

Generally, drag on thin sheet metal

and push on thicker materials

1 - Electrode



• A GMAW electrode is:

– A metal wire

– Fed through the gun by

the wire feeder

– Measured by its diameter

GMAW electrodes are commonly

packaged on spools, reels and coils

2 - Arc



•An electric arc occurs

in the gas filled space

between the electrode

wire and the work

piece

Electric arcs can generate

temperatures up to 10,000°F

3 - Weld Puddle



• As the wire electrode

and work piece heat up

and melt, they form apool of molten material

called a weld puddle

• This is what the welder

watches and

manipulates whilewelding.045” ER70S-6 at 400 ipm wire feed

speed and 28.5 Volts with a 90% Arg

10% CO2 shielding gas

4 - Shielding Gas



• GMAW welding

requires a shielding gas

to protect the weld

puddle

• Shielding gas is usually

inert gases , CO2 or a

mixture of both

The gauges on the regulator show g

flow rate and bottle pressure

5 - Solidified WeldMetal



• The welder “lays a

bead” of molten metalthat quickly solidifies

into a weld

• The resulting weld is

slag free

An aluminum weld done

with the GMAW process

Advantages of GMAW

h f



• High operating factor

• Easy to learn

• Limited cleanup• Use on many different

metals: stainless steel,

mild (carbon) steel,

aluminum and more

• All position

• Great for small scale

use with 115V and

230V units

Limitations of GMAW

L t bl



• Less portable

• GMAW equipment is more

expensive than SMAW

equipment

• External shielding gas can

be blown away by winds

• High radiated heat

• Difficult to use in out of

position joints

TIG



• Gas tungsten arc welding (GTAW), also knowntungsten inert gas (TIG) welding, is an arc weld

process that uses a non-consumable tungsten electrto produce the weld. The weld area is protected fratmospheric contamination by an inert shielding(argon or helium), and a filler metal is normally usthough some welds, known as autogenous welds,not require it. A constant-current welding power supproduces energy which is conducted across thethrough a column of highly ionized gas and metal vapknown as a plasma.

TIG



TIG



Water cooled torch of TIG



TIG Shielding Gases



Argon• Good arc starting

• Good cleaning action

• Good arc stability

• Focused arc cone

• Lower arc voltages

• 10-30 CFH flow rates

Helium• Faster travel speeds

• Increased penetration

• Difficult arc starting

• Less cleaning action

• Less low amp stability

• Flared arc cone

• Higher arc voltages• Higher flow rates (2x)

• Higher cost than argon

TIG Shielding Gases



Argon/Helium Mixtures• Improved travel speeds over pure argon

• Improved penetration over pure argon• Cleaning properties closer to pure argon

• Improved arc starting over pure helium

• Improved arc stability over pure helium

• Arc cone shape more focused than pure helium

• Arc voltages between pure argon and pure helium

• Higher flow rates than pure argon• Costs higher than pure argon



SAW

SAW



• The molten weld and the arc zone are protected from atcontamination by being "submerged" under a blanket ofusible flux consisting of lime, silica, manganese oxidefluoride, and other compounds. When molten, the fluxconductive, and provides a current path between the electhe work. This thick layer of flux completely covers the mothus preventing spatter and sparks as well as suppressing t

ultraviolet radiation and fumes that are a part of the shiearc welding (SMAW) process.



Advantages



• High deposition rates (over 100 lb/h (45 kg/h) have been reported).

• High operating factors in mechanized applications.

• Deep weld penetration.• Sound welds are readily made (with good process design and control).

• High speed welding of thin sheet steels up to 5 m/min (16 ft/min) is possible.

• Minimal welding fume or arc light is emitted.

• Practically no edge preparation is necessary.

• The process is suitable for both indoor and outdoor works.

•Low distortion

• Welds produced are sound, uniform, ductile, corrosion resistant and have good imp

• Single pass welds can be made in thick plates with normal equipment.

• The arc is always covered under a blanket of flux, thus there is no chance of spatter

• 50% to 90% of the flux is recoverable.

Limitations



• Preferred for ferrous (steel or stainless steels) and some nicalloys.

• Normally limited to long straight seams or rotated pipes or v

• Requires relatively troublesome flux handling systems.

• Flux and slag residue can present a health and safety concer

• Requires inter-pass and post weld slag removal.

Also Known AS



• Wire Feed

• MIG = Metal Inert Gas• Inert Gas= Inactive gas that does not combine chemically with bas

metal

• MAG= Metal Active Gas

• Active Gas= Gas will combine chemically with base or filler metal

Advantages

f l

Disadvantages



• Variety of Metals

• All Position Welding

• Quality Welds

• Little to No Slag

• Low Spatter

• Cost

• Portability

• Clean Base Material

GMAW Equipment



• Power Supply

• Wire Feeder

• Electrical mechanical device that feed required amount of filler maconstant rate of speed

GMAW Equipment



• Welding filler electrode

• Small diameter consumable electrode that is supplied to the weldthe roller drive system

• Shielding Gas

• Gas used to protect the molten metal from atmospheric contamin

• 75%Argon (inert gas) & 25% Carbon Dioxide most common gas used for GM

Principles of the GMAW Process



GMAW Process Parameters



Steel Material .035” wire Short- Arc Mode

Thickness Gas75%AR -25%CO2

Amps Wire

Speed

Vo

1/8” 18-19 140-150 280-300 23-

3/16” 18-19 160-170 320-340 24-

1/4” 21-22 180-190 360-380 24-5/16” 21-22 200-210 400-420 25-

3/8” 23-24 220-250 420-520 26-

TIG

• Gas tungsten arc welding (GTAW) also known



• Gas tungsten arc welding (GTAW), also knowntungsten inert gas (TIG) welding, is an arc weld

process that uses a non-consumable tungsten electrto produce the weld. The weld area is protected fratmospheric contamination by an inert shielding(argon or helium), and a filler metal is normally usthough some welds, known as autogenous welds,not require it. A constant-current welding power sup

produces energy which is conducted across thethrough a column of highly ionized gas and metal vapknown as a plasma.



TIG



Water cooled torch of TIG



The tungsten arc process is being employed widely for the precision joining of

critical components which require controlled heat input. The small intense heat

source provided by the tungsten arc is ideally suited to the controlled melting of



source provided by the tungsten arc is ideally suited to the controlled melting of

the material. Since the electrode is not consumed during the process, as with th

MIG or MMA welding processes, welding without filler material can be done

without the need for continual compromise between the heat input from the arcand the melting of the filler metal.

TIG Shielding Gases

Argon Helium



Argon• Good arc starting

• Good cleaning action• Good arc stability

• Focused arc cone

• Lower arc voltages

• 10-30 CFH flow rates

Helium• Faster travel speeds

• Increased penetration• Difficult arc starting

• Less cleaning action

• Less low amp stability

• Flared arc cone

• Higher arc voltages• Higher flow rates (2x)

• Higher cost than argon



SAW

SAW

Th lt ld d th t t d f t



• The molten weld and the arc zone are protected from atcontamination by being "submerged" under a blanket o

fusible flux consisting of lime, silica, manganese oxidefluoride, and other compounds. When molten, the fluxconductive, and provides a current path between the electhe work. This thick layer of flux completely covers the mothus preventing spatter and sparks as well as suppressing t

ultraviolet radiation and fumes that are a part of the shiearc welding (SMAW) process.



Fluxes are fused or agglomerated consisting of MnO, SiO2, CaO, MgO, ATiO2, FeO, and CaF2 and sodium/potassium silicate



2 2 p

The ratio of contents of all basic oxides to all acidic oxides in some

proportion is called basicity index of a flux. CaO, MgO, BaO, CaF2, Na

K2O, MnO are basic constituents while SiO2, TiO2, Al2O3 are considereacidic constituents.

Electrode wire size, welding voltage, current and speed are four mostimportant welding variables apart from flux.



Welding voltage has nominal effect on the electrode wire melting rate bu

voltage leads to flatter and wider bead, increased flux consumption and to porosity caused by rust or scale and helps bridge gap when fill up is p

voltage produces resistance to arc blow but high narrow bead with poor removal. Welding voltages employed vary from 22 to 35 V

If the welding speed is increased, power or heat input per unit length

weld is decreased, less welding material is applied per unit length o



weld, and consequently less weld reinforcement results and penetrat

decreases. Travel speed is used primarily to control bead size and

penetration. It is interdependent with current.

Excessive high travel speed decreases wetting action, increases

tendency for undercut, arc blow, porosity and uneven bead shapes wh

slower travel speed reduces the tendency to porosity and slag inclusi



Influence of Welding Parameters on Bead Shape.

Advantages

• High deposition rates (over 100 lb/h (45 kg/h) have been reported).



g p ( / ( g/ ) p )

• High operating factors in mechanized applications.

• Deep weld penetration.

• Sound welds are readily made (with good process design and control).

• High speed welding of thin sheet steels up to 5 m/min (16 ft/min) is possible.

• Minimal welding fume or arc light is emitted.

• Practically no edge preparation is necessary.

• The process is suitable for both indoor and outdoor works.

• Low distortion

• Welds produced are sound, uniform, ductile, corrosion resistant and have good imp

• Single pass welds can be made in thick plates with normal equipment.

• The arc is always covered under a blanket of flux, thus there is no chance of spatter

• 50% to 90% of the flux is recoverable.

Limitations

• Preferred for ferrous (steel or stainless steels) and some nic



Preferred for ferrous (steel or stainless steels) and some nicalloys.

• Normally limited to long straight seams or rotated pipes or v

• Requires relatively troublesome flux handling systems.

• Flux and slag residue can present a health and safety concer

• Requires inter-pass and post weld slag removal.

Welding All

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