welding of aerospace alloys

7/23/2019 Welding of Aerospace Alloys

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MATERIALMATERIAL

JOININGJOINING

CVS Murthy, ScFCVS Murthy, ScF

P.Mastanaiah, ScCP.Mastanaiah, ScC


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WELDING

Joining of two materials to produce the weld

Weld:

Alocalized coalescence of metals or non-metals which is producedeither by heating the materials to a suitable temperature with or without the

application of the pressure Or by the application of pressure alone and with

or without the use of filler metal


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ROLE OF WELDING IN AEROSPACE APPLICATIONS

ECONOMY AND DESIGN FLEXIBILITY

OPERATING FLEXIBILITY

MECHANISATION

PROCESS ALTERNATIVES

JOINING OF DISSIMILAR MATERIALS


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DIFFERENT WELDING PROCESSES

SMAW DIFFUSION

BONDING

GTAW ULTRASONIC

GMAW FRICTION

RESISTANCE

ELECTRON BEAM

LASER BEAM


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Features of fusion welded jointFusion

zone Heat Affected ZoneBase

Metal

Weld

Interface

Fusion zone - a mixture of filler metal and base metal melted

together homogeneously due to convection as in casting.

Epitaxial grain growth

Weld interface a narrow boundary immediately solidifiedafter melting.

Heat Affected Zone (HAZ) below melting but substantial

microstructural change in the base material.

Unaffected base metal zone
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JOINT DESIGN


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WELDING FACILITIES

ATDRDL


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WELDING APPLICATIONS IN DRDL

PROPELLENT TANK

ROCKET MOTAOR CASING

THRUST FRAME

AIR FRAME COMPONENTS

AIR BOTTLE

AIR INTAKE ASSEMBLY

INTER STAGE ASSEMBLY


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COMMON MATERIALS USED AT DRDL

STAINLESS STEELS

ALUMINIUM ALLOYS

HIGH STRENGTH STEELS

TITANIUM ALLOYS

NICKEL BASED SUPER ALLOYS

PRECIPITATION HARDENED STEELS


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STAINLESS STEELS

SS 304SS 304L

SS 316

SS 316L

SS 321

SS 430

PROCESS: TIG WELDING

PROBLEMS: Cr- Carbide Precpitation and weld decay


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ALUMINIUM ALLOYS

NON- HEATTREATABLE

( Si, Fe, Mn, Mg)

HEAT TREATABLE

( Cu, Mg, Zn, Si )

SOLID SOLUTION IN

ALUMINIUMPRESENT AS DISPERSED PHASES

SOLID SOLUTION STRENGTHENING


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ALUMINIUM ALLOYS

AA 6061 H20

AA2014 H15

AA2219

AA 5083 NS6

AA5086 NS8

PROCESS : TIG


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WELDABILITY

A weldable material is one that can be fused with out the formation ofdeleterious Phases or constituents either in weld or in HAZ, has sufficient

ductility both in weld and HAZ from the melting temperature to room

temperature to resist cracking and has suitable strength and fracture

resistance either in the as welded condition or on completion of poet weld

thermal processing

A weldable material should also be amenable to repair welding procedure

without inherent tendencies towards the formation of new defects orSignificant reduction in properties


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WELDABILITY OFWELDABILITY OF

ALUMINIUM ALLOYSALUMINIUM ALLOYS

Non-heat treatable alloysNon-heat treatable alloys::

When welded these alloys mayWhen welded these alloys may

lose the effects of work hardeninglose the effects of work hardeningresulting in softening of HAZ.resulting in softening of HAZ.

Heat treatable alloysHeat treatable alloys::

Fusion welding redistributes theFusion welding redistributes thehardening constituents in the HAZhardening constituents in the HAZ

which locally reduces materialwhich locally reduces material

strength.strength.


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ETALLURGICAL EFFECTS OF WELDING ALUMINIUM ALLOY

BASE METAL - PROCESS , HEAT INPUT

WELDMENT - RATE OF SOLIDIFICATION- HEAT INPUT

COMPOSITION Al-Mg

- PROCESS

- THICKNESS

NON- HEATREATABLE ALLOYS

- WELD METAL

- ANNEALED

- UNAFFECTED

AS WELDED PROPERTIES

FW UTS ANNEALED PS %E

1100 1100 9 8 4 30

3003 1100 11 10 5 245086 5356 28 25 12 18


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FILLER ALLOY SELECTIONFILLER ALLOY SELECTION

Factors considered in selection ofFactors considered in selection of

filler alloyfiller alloy

Weld crack sensitivityWeld crack sensitivity

Tensile and shear strength of the weldTensile and shear strength of the weld

Corrosion resistanceCorrosion resistance

DuctilityDuctility

Response to heat treatmentResponse to heat treatment

Color match after anodizingColor match after anodizing


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HEAT TREATABLE ALUMINIUM ALLOY WELD MACRO STRUCTURE


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HEAT TREATABLE ALUMINIUM ALLOY WELD MACRO STRUCTURE

Weld metal

Fusion Zone

Solid Solution ZonePartially annealed

and overaged zone

Unaffectedbase metal


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Titanium & Its alloysTitanium & Its alloys

HIGH STRENGTH TO WEIGHT RATIO

EXCELLENT CORROSION RESISTANCE

CREEP STRENGTH & FATIGUE STRENGTH

FRACTURE TOUGHNESS

DUCTILITY

AEROSPACE INDUSTRIES 50-60%

CHEMICAL & ELECTRO CHEMICAL INDUSTRIES

FERTILIZER & FOOD INDUSTRY

PAPER & PULP INDUSTRY


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PRECAUTIONS FOR GAS SHIELDED PROCESSPRECAUTIONS FOR GAS SHIELDED PROCESS

100 % SHIELDING OF THE WELD & HEAT AFFECTED ZONEINVOLVING PRIMARY & SECONDARY & BACKINGSHIELDING.

PERFECT CLEANING OF THE BASE METAL & FILLER METAL

HIGH PURITY & DRY INERT GAS ( 99, 95 % MIN) ONLYSHOULD BE USED

ADVISABLE TO USE OPTIMUM GAS FLOW RATES TO

AVOID TURBULENCE & ENTRAPMENT OF AIR.

SHORT ARC LENGTH


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TITANIUM WELDINGTITANIUM WELDING

OPEN TIG ARCWITH FLUX

RESISTANCEELECTRON BEAM WELDING

ASER WELDING

GTAW WITH PRIMARY/ SECONDARY

& BACKING SHIELDING METHODSGLOVE BOX

TORCH TRAILING SHIELD FOR GAS SHIELDEDTORCH TRAILING SHIELD FOR GAS SHIELDED


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TORCH TRAILING SHIELD FOR GAS SHIELDEDTORCH TRAILING SHIELD FOR GAS SHIELDED

ARC WELDING OF TITANIUM ALLOYSARC WELDING OF TITANIUM ALLOYS

WELDING DIRECTION

inert gasinlet metalchamber

torchnozzle

POROUS METALDIFUSIONSCREEN

Trailing shield

imary shielding : Fusion zone by Torch nozzleHot solidified weld metal by Trailing

SECONDARY INERT GAS SHIELDINGSECONDARY INERT GAS SHIELDING


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SECONDARY INERT GAS SHIELDINGSECONDARY INERT GAS SHIELDING

INCORPORATED IN THE WELDING FIXTUREINCORPORATED IN THE WELDING FIXTURE

Shield gas flowthrougth torch nozzle shielding gas diffuse

hold down bars

base

shielding - gas port

F

FF

F

Shieldinggas port

Provides 3 way shielding 2 at the sides1 at root side

ki hi ldiB ki hi ldi


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Backing gas in

Shielding provided in backing bars

Employed in Fillet & Corner welds

Backing shieldingBacking shielding


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Glove box weldingGlove box welding

100 % Shielding

Inert gas is filled in the chambafter evacuation 2 to 3 times.

A positive pressure is alwaysmaintained.

Welding is done manuallyautomatically

Avoids wastage of costly argongas

CO G O O C O GCONFIGURATION OF ELECTRON BEAM WELDING M


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CONFIGURATION OF ELECTRON BEAM WELDING MCONFIGURATION OF ELECTRON BEAM WELDING M

THERMIONIC EMISSION

WHEN CERTAIN MATERIALS LIKE TUNGSTEN/ TANTALUM

ARE HEATED TO 25000C , THEY EMIT ELECTRONS.


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O O O


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KEYHOLE FORMATION

THE BUTT JOINT

PRIOR TO WELDING

MELTING OCCURS AT THE IMPINGEMENT

OF THE ELECTRON BEAM

KEY HOLE FORMATION THE KEY HOLE AND ITS

MOLTEN POOL HAVE

PENETRATED

THE WORK PIECE

THE WELD SEAM FORMED

ON SOLIDIFICATION


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TYPICAL HEAT INPUTS& COOLING RATES FO


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PROCESSPROCESS HEATHEATINPUT(KJ/C)INPUT(KJ/C)

COOLINGCOOLINGRATERATE

(( 00C/Sec)C/Sec)

MANUALMANUAL

GTAWGTAW

3030 1414

PLASMA ARCPLASMA ARC

WELDINGWELDING2222 3636

AUTOMATICAUTOMATIC

GTAWGTAW

1010 7070

EBWEBW 2.82.8 535535

LASERLASER

WELDINGWELDING

1.61.6 >535>535

TYPICAL HEAT INPUTS& COOLING RATES FOVARIOUS WELDING PROCESSES


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welding of aerospace alloys

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