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ArcArc

weldingwelding

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CCOONNTTEENNTTSS

INTRODUCTIONINTRODUCTION

ARC COLUMNARC COLUMN

CONDITION FOR MAX.UTILISATION OF POWERCONDITION FOR MAX.UTILISATION OF POWER

METAL INERT GAS WELDING (M.I.G)METAL INERT GAS WELDING (M.I.G)

TUNGSTEN INERT GAS WELDING (T.I.G)TUNGSTEN INERT GAS WELDING (T.I.G)

RESISTANCE WELDINGRESISTANCE WELDING

STUD WELDINGSTUD WELDING

SOLDERING & BRAZINGSOLDERING & BRAZING

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INTRODUCTIONINTRODUCTION

Welding is the process of joining twoWelding is the process of joining two

materials with or without applicationmaterials with or without applicationof heat, pressure or filler material.of heat, pressure or filler material.

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ARC WELDING EQUIPMENTSARC WELDING EQ

UIPMENTS

AC or DC machineAC or DC machine ElectrodeElectrode Electrode holderElectrode holder Cables, cable connectorsCables, cable connectors

Cable lugCable lug Chipping hammerChipping hammer Earthlings clampsEarthlings clamps Wire brushWire brush

HelmetHelmet Safety gogglesSafety goggles Hand glovesHand gloves Aprons, sleeves.Aprons, sleeves.

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WEL

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ELECTRODES FOR ARC WELDINGELECTRODES FOR ARC WELDING

Basically electrodes are classified intoBasically electrodes are classified into

1. consumable electrode1. consumable electrodea. Bare electrodea. Bare electrode

b. Coated electrodeb. Coated electrode

2. Non-consumable electrode2. Non-consumable electrode

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Specification of electrodeSpecification of electrode

TYPE OF COATING

WELDING POSITION

% ELONGATION

CURRENT CONDITIONS

STRENGTH OF ELECTRODE

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ARC COLUMNARC COLUMN

The arc column is generated between an anode, which is theThe arc column is generated between an anode, which is thepositive pole of D.C.power supply and the cathode.positive pole of D.C.power supply and the cathode.

ELECTRICAL THEORY OF ARC COLUMNELECTRICAL THEORY OF ARC COLUMN

Approximately 1Kw-hr of electricity will create 3413 Btu,Approximately 1Kw-hr of electricity will create 3413 Btu,

i.e.3.6MJ of heat will be liberated.i.e.3.6MJ of heat will be liberated.

Three areas of heat are liberated in the arc stream.Three areas of heat are liberated in the arc stream.

Cathode areaCathode areaPlasma areaPlasma area

Anode areaAnode area

Of the above anode area is the high heat areaOf the above anode area is the high heat area..

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INITIATION OF ARCINITIATION OF ARC

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TYPES OF WELDSTYPES OF WELDS

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METAL INERT GAS WELDINGMETAL INERT GAS WELDING

WORKING PRINCIPLEWORKING PRINCIPLE

Metal inert gas welding or Gas metal-arcMetal inert gas welding or Gas metal-arc

welding is a gas shielded metal-arc welding process,welding is a gas shielded metal-arc welding process,

which uses the high heat of an electric arc between awhich uses the high heat of an electric arc between acontinuously fed, consumable electrode wire and thecontinuously fed, consumable electrode wire and the

material to be welded in the presence of an inert gas.material to be welded in the presence of an inert gas.

CURRENT RANGECURRENT RANGE: 100 to 400A: 100 to 400A

Welding wire :Welding wire :citofilcitofilof diameter of 0.9 to 1.6mmof diameter of 0.9 to 1.6mm

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Block Diagram of MIG weldingBlock Diagram of MIG welding

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Working PrincipleWorking Principle

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MIG welding is done in combination ofMIG welding is done in combination of

For welding aluminium/copper, argon orFor welding aluminium/copper, argon or

argon-helium mixtures are used.argon-helium mixtures are used.

For stainless steel, argon-oxygen or helium-For stainless steel, argon-oxygen or helium-

argon gas mixtures are used.argon gas mixtures are used.

Titanium requires pure argon gas shielding.Titanium requires pure argon gas shielding.

Copper-nickel and high-nickel alloys useCopper-nickel and high-nickel alloys useargon-helium mixture.argon-helium mixture.

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ADVANTAGES OF MIG

No flux required.No flux required.

High welding speed.High welding speed.

Increased corrosion resistance.Increased corrosion resistance.

Easily automated welding.Easily automated welding.

Welds all metals including aluminium and stainless steel.Welds all metals including aluminium and stainless steel.

High economy.High economy.

Up to 25-30 mm plates can be welded in single pass.Up to 25-30 mm plates can be welded in single pass.

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TUNGSTEN INERT GAS WELDINGTUNGSTEN INERT GAS WELDING

WORKING PRINCIPLEWORKING PRINCIPLE

This process uses the intense heat of an electric arc between a non-This process uses the intense heat of an electric arc between a non-consumable tungsten electrode and the material to be welded. Theconsumable tungsten electrode and the material to be welded. Theshielding is obtained from an inert gas such as helium or argon or ashielding is obtained from an inert gas such as helium or argon or amixture of two.mixture of two.

ELECTRODE: TungstenELECTRODE: Tungsten

FLUX : Argon or Helium ( Inert gas)FLUX : Argon or Helium ( Inert gas)

The TIG process lends itself able to the fusion welding of aluminium andThe TIG process lends itself able to the fusion welding of aluminium andit's alloys, stainless-steel, magnesium alloys, nickel base alloys, copperit's alloys, stainless-steel, magnesium alloys, nickel base alloys, copper

base alloys, carbon steels. TIG welding can also be used for the combiningbase alloys, carbon steels. TIG welding can also be used for the combiningof dissimilar metals, hard facing, and the surfacing of metals. But thisof dissimilar metals, hard facing, and the surfacing of metals. But this

process is not used, as often on plate over 6.4 mm thick, but it is easierprocess is not used, as often on plate over 6.4 mm thick, but it is easierthan MIG welding for thin plates and small parts.than MIG welding for thin plates and small parts.

In general, an AC power source is best for TIG welding non-ferrous alloysIn general, an AC power source is best for TIG welding non-ferrous alloysexcept deoxidized copper. For ferrous alloys the DC power with straightexcept deoxidized copper. For ferrous alloys the DC power with straightpolarity is better.polarity is better.

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ADVANTAGES OF TIG WELDINGADVANTAGES OF TIG WELDING

It produces high quality welds in non-ferrousIt produces high quality welds in non-ferrous

metals.metals.

Practically no weld cleaning is necessary.Practically no weld cleaning is necessary.

The arc and weld pool are clearly visible to theThe arc and weld pool are clearly visible to the

welder.welder.

Developed for most reactive materials.Developed for most reactive materials.

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DISADVANTAGES OF TIG WELDINGDISADVANTAGES OF TIG WELDING

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DISADVANTAGESDISADVANTAGES

The flux needs preplanning of the same on theThe flux needs preplanning of the same on the

joint that is not always possible.joint that is not always possible.

The process is limited to welding in flatThe process is limited to welding in flat

position and on metal more than 4.8 mm thick.position and on metal more than 4.8 mm thick.

Flux is subject to contamination that mayFlux is subject to contamination that may

cause weld porosity.cause weld porosity.

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Coated electrodes serve several purposesCoated electrodes serve several purposes

To facilitate the establishment and maintenance of theTo facilitate the establishment and maintenance of thearc, coating of potassium compounds is provided.arc, coating of potassium compounds is provided.

To protect the molten metal from the oxygen andTo protect the molten metal from the oxygen andnitrogen.nitrogen.

To provide the formation of slag so as to protect theTo provide the formation of slag so as to protect thewelding seam from rapid cooling. For this, rutilewelding seam from rapid cooling. For this, rutilecoating is provided.coating is provided.

To provide a means of introducing alloying elementsTo provide a means of introducing alloying elements

not contained in the core wire.not contained in the core wire. Shielding gas protection, for this, cellulose coatingShielding gas protection, for this, cellulose coating

will be applied.will be applied.

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MERITSMERITS

Because of high heat concentration, considerablyBecause of high heat concentration, considerably

higher welding speeds can be used.higher welding speeds can be used.

Because of high heat concentration and faster weldingBecause of high heat concentration and faster welding

speeds distortion is much less.speeds distortion is much less. Welding is carried out without sparks, smoke, flashWelding is carried out without sparks, smoke, flash

and spatter.and spatter.

Weld metal deposited possesses uniformity, goodWeld metal deposited possesses uniformity, goodductility, corrosion resistance and good impactductility, corrosion resistance and good impact

strength.strength.

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SOLDERINGSOLDERING

For soldering temperature should be either less than 427For soldering temperature should be either less than 427ooCC ororless than melting point of metals to be joined, whichever isless than melting point of metals to be joined, whichever isminimum.minimum.

Air-acetylene is used as heat source for soldering earlier butAir-acetylene is used as heat source for soldering earlier but

now electrical resistance is used as heating source.now electrical resistance is used as heating source. Filler material: Lead + Tin Soft solderFiller material: Lead + Tin Soft solder If percentage of tin increases weld ability and joint strengthIf percentage of tin increases weld ability and joint strength

but cost is high.but cost is high.

Lead + Tin + Silver Hard solderingLead + Tin + Silver Hard soldering By using this joint is much more but cost is very high.By using this joint is much more but cost is very high. For space and aircraft industries it is used.For space and aircraft industries it is used.

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BRAZINGBRAZING

For Brazing, temperature should be eitherFor Brazing, temperature should be either

greater than 427greater than 427ooCCor less than melting pointor less than melting point

of metals to be joined.of metals to be joined.

FILLER MATERIALFILLER MATERIAL:: Copper + zincCopper + zinc

Due to capillary action, molten metal passDue to capillary action, molten metal pass

through joint is known asthrough joint is known asBrazing.Brazing.

Due to gravity action, molten metal passDue to gravity action, molten metal pass

through joint is known asthrough joint is known asBraze welding.Braze welding.

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WELDABILITYWELDABILITY

Melting point of material.Melting point of material.

Thermal conductivity.Thermal conductivity.

Thermal expansion.Thermal expansion. Electrical resistance.Electrical resistance.

Surface condition.Surface condition.

Reactiveness with Oxygen.Reactiveness with Oxygen.

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yytt

MIG (Metal Iner

Welding) uses an

filler material. The

filler -material iscontrolled by the

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