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WELDABILITY OF TITAINIUMALLOYS

BY

12021D0415

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WELDABILITY :WELDABILITY is the capacity of a metal orcombination of metals to be welded into a suitablydesigned structure and for the resulting weld jointsto possess the required metallurgical properties toperform satisfactorily in the intended service.

A material's weldability is used to determine thewelding process and to compare the final weldquality to other materials

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FACTORS EFFECTING WELDABILITY

1. Welding process

2. Base metal properties3. Filler metal

4. Surface conditions

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Good weldability is characterised by ease with whichthe welding process is accomplished by Absence of weld defects Acceptable strength

Ductility Toughness

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WELDABILITY OF TITAINIUM ALLOYS

Commercially pure titanium and most of titaniumalloys can be welded by procedures and equipmentused in welding austenitic stainless steel and

aluminum. Because of the high reactivity of titanium and

titanium alloys at temperatures above 550C,additional precautions must be applied.

Also, titanium base metal and filler metal must beclean to avoid contamination during weld.

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Characteristics of Titanium

phase : Titanium is a closely packedhexagonal structure known as phase up to885c.

phase : The temperature above 885c thestructure is body centred cubic this is knownas a phase.

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1.Commercially pure titanium2.Alpha and near alpha alloys

3.Alpha-beta alloys4. Beta alloys

CLASSIFICATION OF TITANIUM ALLOYS

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Commercially pure titanium:

This is classified on basis of mechanicalproperties and maximum interstaticalimpurities.

The interstatical elements like o 2,N2,c andfe increases ,strength also increases.

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Alpha and near alpha alloys:

This always contain high percentage of alphaphase in their microstructure.

Alpha-beta alloys:It contains mixture of and phases in theirmicrostructure.

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Beta alloys: It contains high percentage of phase stabilising elements.

Agening at low temperature increases itstrength .

Most of the alloys are weldable in eitherannealed or heat treated condition.

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PHYSICAL PROPERTIES OF TIATANIUM

Density =4.43 g/cm2

Melting point=1668 c

Coeffecient of thermal expansion at 20 c=8.4m 11

Specific heat at 20 c=552j/kg k

Modulus of elasticity=117 gpa

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WELDING PROCESSES

Joint design Pre cleaning

Preheating Protection during Joining

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The following fusion-welding processes are usedfor joining titanium and titanium alloys: Gas-tungsten arc welding (GTAW)

Gas-metal arc welding (GMAW) Plasma arc welding (PAW) Electron-beam welding (EBW)

Laser-beam welding (LBW) Friction welding (FRW) Resistance welding (RW)

WELDING PROCESS

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Advantages

High corrosion resistance Good ductility

Less weight High strength

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APPLICATIONS

Aircrafts Missiles

Nuclear Industries

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