Welding Processes

Welding Process in Construction

Classification of Welding Processes

Wel

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Pro

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ion

Method of Application

Arc Welding-The Concept

Power Sources In Arc Welding & Polarity

Shielding Requirement and Application

Consumable & Non Consumable Electrodes

Shielded Metal Arc Welding - SMAW

Gas Tungsten Arc Welding – GTAW / TIG

Gas Metal Arc Welding – GMAW / MIG

Flux Cored Arc Welding – FCAW

Submerged Arc Welding – SAW

Plasma Arc Welding - PAW

Advanced Welding Techniques In Construction

Welding Processes In Construction

Classification

Of WeldingProcesses

Welding Processes

Arc Welding (AW)

Brazing (B)

Others

OXYFUEL Gas Welding (OFW)

Resistance Welding (RW)

Soldering (S)

Solid State Welding (SSW)

GAS TUNGSTEN ARC WELDING (GTAW)GAS METAL ARC WELDING (GMAW)

SHIELDED METAL ARC WELDING (SMAW)

FLUX CORED ARC WELDING (FCAW)SUBMERGED ARC WEDLING (SAW)

PLASMA ARC WELDING (PAW)

ELECTROSLAG ARC WELDING (ESAW)STUD ARC WEDLING (SW)CARBON ARC WELDING (CAW)ELECTROGAS WEDLING (EGW)BARE METAL ARC WEDLING (BMAW)ATOMIC HYDROGEN WELDING (AHW)

ARC BR (AB)BLOCK BR (BB)

CARBON ARC BR (CAB)DIFFUSION BR (DFB)

DIP BR (DB)FURNACE BR (FB)

FLOW BR (FB)INDUCTION BR (IB)INFRARED BR (IRB)

RESISTANCE BR (RB)TORCH BR (TB)

ELECTRON BEAM (EBW)ELECTROSLAG (ESW)

FLOW (FLOW)INDUCTION (IW)

LASER BEAM (LBW)PERCUSSION (PEW)

THERMITE (TW)

AIR ACETYLENE WELDING (AAW)OXYACETYLENE WELDING (OAW)

OXYHYDROGEN WELDING (OHW)PRESSURE GAS WELDING (PGW)

FLASH WELDING (FW)PROJECTION WELDING (PW)RESISTANCE SEAM WELDING (RSEW)RESISTANCE SPOT WELDING (RSW)UPSET WELDING (UW)

DIP SLD(DS)FURNACE SLD (FS)

INDUCTION SLD (IS)INFRARED SLD(IRS)

IRON SLD (INS)RESISTANCE SLD (RS)

TORCH SLD (TS)WAVE SLD (WS)

ULTRASONIC (USW)DIFFUSION (DFW)COEXTRUSION (CEW)FORGE(FOW)COLD(CW) EXPLOSION(EXW)FRICTION(FRW)HOT PRESS(HPW)ROLL(ROW)


Classification

Of WeldingProcesses

A group of welding processes that produce coalescence of work pieces by heating them with an arc. The processes are used with or without the application of pressure and with or without filler metal.

ARC WELDING

A group of welding processes that produces coalescence of work pieces by heating them with an oxy-fuel gas flame. The processes are used with or without the application of pressure and with or without filler metal.

OXYFUEL WELDING

A group of welding processes that produces coalescence of the faying surfaces with the heat obtained from resistance of work pieces to the flow of the welding current in a circuit and by the application of pressure.

RESISTANCE WELDING

A group of welding processes that produces coalescence by the application of pressure without melting any of the joint components.

SOLID STATE WELDING


Classification

Of WeldingProcesses

A group of joining processes wherein a joint is produced by heating, generally below 800°F and using a nonferrous filler metal that has a melting point below that of the base metals. The filler metal is distributed between the properly fitted parts by capillary attraction.

SOLDERING

A group of joining processes that are identical to soldering except that the joining takes place at temperatures above 800°F. The filler metal is distributed between the properly fitted parts by capillary attraction.

BRAZING


Methods Of Welding Application Methods of

Application

MANUAL

SEMI-AUTOMATIC

AUTOMATIC

MACHINE

ROBOTIC

ADAPTIVE


Methods Of Welding Application

Welding with the torch, gun, or electrode holder held and manipulated.

MANUAL WELDING (MA)

Manual welding with equipment that automatically controls one or more of the welding conditions.

SEMI-AUTOMATIC WELDING (SA)

Requires manual adjustment of the equipment controls in response to visual observation, with torch, gun or electrode holder by a mechanical device.

MACHINE WELDING (ME)

Requires only occasional or no observation of the welding and no manual adjustment of the equipment controls.

AUTOMATIC WELDING (AU)



Welding that is performed and controlled by robotic

equipment.

ROBOTIC WELDING (RO)

Welding with a process control system that determines changes in welding conditions automatically and directs the equipment to take appropriate action.

ADAPTIVE CONTROL WELDING (AD)



MANUAL WELDING

SEMI-AUTOMATICWELDING

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MACHINE WELDING

AUTOMATIC WELDING



ROBOTIC WELDING

ADAPTIVE WELDING


ARC Welding

(The Concept)

The basic arc-welding circuit is illustrated in the Figure below. An AC or DC power source, fitted with whatever controls may be needed, is connected by a work cable to the work piece and by a "hot" cable to an electrode holder of some type, which makes an electrical contact with the welding electrode.


ARC Welding

(The Concept)

An arc is an electric current flowing between two electrodes through an ionized column of gas. A negatively charged cathode and a positively charged anode create the intense heat of the welding arc. Negative and positive ions are bounced off of each other in the plasma column at an accelerated rate.

In welding, the arc not only provides the heat needed to melt the electrode and the base metal, but under certain conditions must also supply the means to transport the molten metal from the tip of the electrode to the work.


ARC Welding

(The Concept)

A welding arc is a sustained high-current, low-voltage electrical discharge through a high conducting plasma that produces sufficient thermal energy which is useful for joining metals by fusion.

The welding arc occurs between the end of an electrode and a work piece that carries current. An arc from 1A ----3000A Voltage from 10V ----40V

The arc occurs when electrons are emitted from the surface of the negative pole (cathode) and flow across a region of hot electrically charged plasma to the positive pole (anode), where they are absorbed.

There are two basic types of welding arcs: One uses a non consumable electrode and the other uses a consumable electrode.


ARC Welding

(The Concept)

The arc occurs when electrons are emitted from the surface of the negative pole (cathode) and flow across a region of hot electrically charged plasma to the positive pole (anode), where they are absorbed.

The non consumable electrode does not melting the arc, and filler metal is not carried across the arc gap. The most welding processes are that uses non consumable electrode are: Gas Tungsten Arc Welding, Plasma Arc Welding, and Carbon Arc Welding


ARC Welding

(The Concept)


Power Sources &

Polarity

All Arc-welding processes require a continuous supply of electrical current in sufficient amount ( Amperage) and of proper voltage to maintain an arc.

This current could be AC or DC but must be supplied to the welding electrode through a device that enables its precise control.

Various types of power sources provide a range of voltage across the welding arc form 13 to 45 volts. The power source may range from less than 10A to 1500 Amps

Power sources are classified according to the type of current ( AC or DC) and according to their output , which may be constant current or constant voltage


Power Sources &

Polarity

AC POWER SOURCES

TRANSFOMER POWER SOURCES

DC AND AC-DC POWER SOURCES

TRANSFOMER-RECTIFIER POWER SOURCES

DC POWER SOURCE

DC GENERATOR WITH AN ARMATURE ROTATING IN A MAGNAETIC FIELD

INVERTER POWER SOURCE

STATE-OF-THE-ART DC TRANSFORMER


Power Sources &

Polarity

POLARITY is the direction of movement of charged particles across the welding arc

AC (Alternating Current)

DCEP (Direct Current Electrode Positive-Also called DCRP-Reverse Polarity)

DCEN (Direct Current Electrode Negative- Also called DCSP –Straight Polarity)


Shielding Requirement

SHIELDING is the means of protecting the Molten Weld Pool.

When molten metal reacts with the atmosphere:

Oxides and nitrides are formedDiscontinuities such as porosityPoor weld metal properties

All Arc Welding processes employ some means of shielding the molten weld pool from the air.


Shielding Application

Welding Fluxes

Three forms:

Granular

Electrode wire coating

Electrode core

Fluxes melt to form a protective slag over the weld pool

Other purposes:

Contain scavenger elements to purify weld metal.

Contain metal powder added to increase deposition rate.

Add alloy elements to weld metal

Decompose to form a shielding gas


Shielding Application

Shielding Gases

Shielding gas forms a protective atmosphere over the molten weld pool to prevent contamination

Inert shielding gases, argon or helium, keep out oxygen, nitrogen, and other gases

Active gases, such as carbon dioxide, are sometimes added to improve variables such as arc stability and spatter reduction


Consumable &Non

Consumable Electrodes

Consumable Electrode Arc Welding

An electric current is used to strike an arc between the base material and a consumable electrode rod or 'stick'. The electrode rod is made of a material that is compatible with the base material being welded. The consumable electrode continuously melts while establishing the arc. The Arc can’t be established without the filler metal rod. Some of the welding processes are:

SHIELDED METAL ARC WEDLING (SMAW)GAS METAL ARC WEDLING (GMAW)FLUX CORED ARC WEDLING (FCAW)SUBMERGED ARC WEDLING (SAW)


Consumable &Non


Consumable Electrode Arc Welding


Consumable &Non


Non-Consumable Electrode Arc Welding

An electric current is used to strike an arc between the base material and a non-consumable electrode . The non-consumable electrode does not melt in the arc, and filler metal is not carried across the arc gap. The Arc can be established without the filler metal rod. The welding processes are:

GAS TUNGSTEN ARC WELDING (GTAW)PLASMA ARC WELDING (PAW)CARBON ARC WEDLING (CAW)


Consumable &Non




Consumable &Non-



GTAW Welding


SMAWPROCESS

It is a manual arc welding process that uses an arc between a

consumable electrode and the weld pool ( base metal).

The process is a manual arc welding process that uses a consumable electrode coated in flux to lay the weld

As the weld is laid, the flux coating of the electrode disintegrates, giving off vapours that serve as a shielding gas and providing a layer of slag, both of which protect the weld area from atmospheric contamination.


SMAWPROCESS

This process is also know as: MMA (MANUAL ARC WELDING) STICK WELDING

The process uses DCEP (Direct Current Reverse Polarity)


SMAWPROCESS

ADVANTAGES: It has maximum flexibility and can weld

many metals in all positions from near minimum to maximum thickness.

The most popular Arc Welding Process It is used in manufacturing and in field

work for construction and maintenance. The method of application is manual.

Semiautomatic and mechanised methods are not used. Automatic method can be used.

Can be used on carbon steels, low alloy steels, stainless steels, cast irons, copper, nickel, aluminum

Welding in the horizontal, vertical and overhead positions are possible depends on the type and size of the electrode, as well as the welding current and the skill of the welder.


SMAWPROCESS

DISADVANTAGES:Lower Quality than GTAW Not as productive as continuous wire

processes Likely to be more costly to deposit a

given quantity of metal Frequent stop/starts to change electrode Relatively high metal wastage (electrode

stubs) Slag entrapment and lack of fusion to

the base metal


SMAWPROCESS


GTAWPROCESS

It is an arc welding process that uses an arc between a tungsten

electrode (non-consumable) and the weld pool.

The process is used with shielding gas and without the application

of pressure.

The process uses DCEN (Direct Current Straight Polarity)


GTAWPROCESS

This process is also know as: TIG ( Tungsten Inert Gas) in UK

WIG ( Wolfram Inert Gas) in Germany

GTAW in USA

The arc area is protected from the atmosphere by the inert

shielding gas flown from the nozzle of the torch.

The shielding gas displaces the air, so that the oxygen and the nitrogen of the air do not come in contact with the molten metal or the hot tungsten electrode.

The main component is the welding power source. The constant-

current (CC) power source is used.


GTAWPROCESS

ADVANTAGES:High quality of welds in almost all metals and alloysVery little, if any, post weld cleaning is requiredThe arc and weld pool are clearly visible to the

welderThere is no filler metal carried across the arc, so little

or no spatterPerformed in all positionsNo slag produced that might be trapped in the weldExtreme control for precision work and high qualityHeat can be controlled very closely and the arc can

be accurately directedUsed for mainly thinner materialsVery useful for maintenance and repair workWelding for unusual metalsJoining thin wall tubing and making root passes in a

pipe joints


GTAWPROCESS

DISADVATAGES:The major limitation is the low

productivityHigh welding skills requiredMore expensive than SMAW


GTAWPROCESS

The shielding gas:Must be inert gasOnly Argon and Helium are usedGas selection is based on metal to be weldedArgon is more commonly used, and is heavier

than air which provides for a more efficient arc shielding. Argon is better for arc starting and operates at a lower arc voltage.

Helium is much lighter than argon and higher flow rates are required.

In some cases, Helium and Argon are mixed for the optimum shielding gas


GTAWPROCESS


GMAWPROCESS

It is an arc welding process that uses an arc between a continuous filler metal electrode and the weld pool.

The process is used with shielding from an externally supplied gas and without the application of pressure.

There are many variations depending on the type of shielding gas, the type of metal transfer, the type of metal welded etc.

This is also called as metal inert gas (MIG) or metal active gas (MAG) welding.


GMAWPROCESS

MIG welding utilizes the heat of an arc between a continuously fed consumable electrode and the work to be welded.

Shielding of the molten pool, the arc, and the surrounding area is provided by an envelope of gas fed through the nozzle.

The shielding gas may be an inert gas, an active gas, or a mixture, surrounds the arc area to protect it from contamination from the atmosphere.


GMAWPROCESS

General purpose shielding gases for MIG welding are mixtures of argon, oxygen and CO2, and special gas mixtures may contain helium.

The MIG process uses semiautomatic, mechanised, or automatic equipment.


GMAWPROCESS


GMAWPROCESS

ADVANTAGES: MIG welding is one of the most popular arc welding

process. Continuous wire feed High deposition rate and minimal number of

stop/start locations Welder has good visibility of weld pool and joint line Little or no post weld cleaning Can be used in all positions Wide range of application: sheet metal industry, pipe

welding.


GMAWPROCESS

DISADVANTAGES: High level of equipment maintenance Major Quality issues if not applied and controlled

properlyJoint and part access is not as good as TIG


GMAWPROCESS

TRANDFER MODE GLOBULAR SPRAY ARC SHORT - CIRCUITING MODIFIED SHORT – CIRCUITING PULSED SPRAY STT (SURFACE TENSION TRANSFER)

Spray Globular

Pulsed-SprayShort-Circuit


FCAWPROCESS

Flux-cored arc welding (FCAW or FCA) is a semi-automatic or automatic arc welding process. FCAW requires a continuously-fed consumable tubular electrode containing a flux

An externally supplied shielding gas is sometimes used, but often the flux itself is relied upon to generate the necessary protection from the atmosphere. The process is widely used in construction because of its high welding speed and portability.

FCAW was first developed in the early 1950s as an alternative to shielded metal arc welding (SMAW). The advantage of FCAW over SMAW is that the use of the stick electrodes used in SMAW is unnecessary. This helped FCAW to overcome many of the restrictions associated with SMAW.


FCAWPROCESS


SAWPROCESS

SAW is an arc welding process that uses an arc or arcs between a bare metal electrode or electrodes and the weld pool.

The arc and molten metal are shielded by a blanket of granular flux on the work pieces.

SAW utilizes the heat of an arc between a continuously fed electrode and the work.

Shielding is obtained from a blanket of granular flux, which is laid directly over the weld area.

The electrode is fed into the arc automatically and travel can be manual or by machine.


SAWPROCESS


SAWPROCESS

ADVANTAGES:High quality weld metalExtremely high deposition rate and

speedSmooth, uniform finished weld with no

spatterLittle or no smokeNo arc flash, thus minimal need for

protectionHigh utilization of electrode wireEasily automated for high operator

factor


SAWPROCESS

MAJOR USES: Welding of structural shapes and the

longitudinal seam of larger diameter pipe

Manufacture of machine components of heavy industry

Vessels and tanks for pressure and storage

Shipbuilding(fabrication of subassemblies)

Steels & pipes in medium and heavy


PAWPROCESS

PAW is an arc welding process that uses a constricted arc between a non consumable electrode and the weld pool (transferred arc) or between the electrode and the constricted nozzle (non-transferred arc).

Shielding is obtained from the ionized gas issuing from the torch, which may be supplemented by an auxiliary source of shielding gas.

PAW is also used for metal cutting and for metal spraying.

If an electric arc between a tungsten electrode and the work is constricted or reduced in cross-sectional area, its temperature increases since it carries the same amount of current. This constricted arc is called plasma.

There are two modes of operation: non-transferred arc and transferred arc.


PAWPROCESS

Advantages of PAW when compared to TIG stem from the fact that PAW has a higher energy concentration. Its higher temperature, constricted cross-sectional area, and the velocity of the plasma jet create a higher heat content.

PAW is normally applied as a manual process. Automatic and mechanized app. (limited)


PAWPROCESS


ADVANCED WELDING

TECHNIQUES IN CONSTRUCTION

Welding Processes

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