Welding of Al alloys, Ti alloys, Cu alloys & Ni alloys

1. Welding of Non-Ferrous Alloys
• Welding of Al alloys
• Welding of Ti alloys
• Welding of Cu alloys
• Welding of Ni alloys

2. Welding of Aluminum Alloys

3. ALUMINIUM AND ITS ALLOYS
•Melting point of Al 660 C
•Light weight, density is about 1/3 that of steel or copper alloys
•Certain aluminum have a better strength to weight ratio than that of high strength steel
•Have good malleability and formability, high corrosion resistance and high electrical and thermal conductivity.
•An ultra pure form of Al is used as photographic reflectors.
•Non tarnishing characteristics Non toxic, non magnetic, and non sparking Electrical conductivity of the electric conductor
grade is about 62% that of copper.
•Relatively soft and weak.
•Strength can be increased by cold working, alloying and heat treatment.

4. Alloy designation: a four digit number for wrought Al and wrought Al alloys 1XXX, 2XXX, 3XXX, 4XXX,…………, 8XXX
AW 1XXX – commercially pure aluminium.
• AW 2XXX – aluminium–copper alloys.
• AW 3XXX – aluminium–manganese alloys.
• AW 4XXX – aluminium–silicon alloys.
• AW 5XXX – aluminium–magnesium alloys.
• AW 6XXX – aluminium–magnesium–silicon alloys.
• AW 7XXX – aluminium–zinc–magnesium alloys.
• AW 8XXX – other elements e.g. lithium, iron.
• AW 9XXX – no alloy groups assigned.
CAST Aluminium
1XX.X, 2XX.X, ……,8XX.X
Alloying elements in Commercial Al alloys include Cu, Si, Mg, Mn, and occasionally Zn, Ni, and Cr. The alloying
elements may enhance the mechanical properties by
• Solid solution hardening
• Responding to precipitation hardening or
• Strain hardening by cold work

5. Temper designation:
F – as fabricated
O – Annealed, recrystallized
H – Strain hardened
 H1 – Strain hardened only
 H2 – Strain hardened Then partially annealed
 H3- Strain hardened and then stabilized
W – Solution heat treated
•T – thermally treated
•T2 – Annealed ( cast products only)
•T3 – Solution heat treated and then cold
•worked
•T4 – Solution heat treated and naturally aged
•T5 – artificially aged only
•T6 – solution heat treated and then artificially aged
•T7 – Solution heat treated and then stabilized
•T8 – solution heat treated, cold worked and
•then artificially aged
•T9 – Solution heat treated, artificially aged and
•then cold worked
•T10- Artificially aged and then cold worked

6. Filler Metals for Al & Al Alloys
GTAW & GMAW are mostly used.
It depends on
• Base metal composition
• Joint design
• Dilution
• Cracking techdencies
• Strength and ductility requirements
• Corrosion in service
• Appearance

7. Other Factor to be consider in welding Al alloys
•Cleaning of base metal
•Weld backing
•Preheating &
•Tack welding
Cleaning of base metal
•Components for welding may be flat, preformed, sheared, sawn or milled.
•Lubricants, oxides, greases, oils, paints must be removed if weld quality is to be maintained.
•Degreasing may be accomplished by wiping, brushing, spraying or vapour degreasing with commercially
available solvents.
•Scraping is also an excellent method for removing the oxide film.
•Stainless steel wire brushes, stainless steel wire wool or files may also be used to remove the oxide.

8. To achieve freedom from porosity, chemical cleaning or pickling may be required

10. Weld Backing
•Used when full penetration weld
•To controle the amount of reinforcement & shape of the
root surface.
•Temporary Backing
•Permanent Backing
Temporary Backing
Copper, Carbon steel, or stainless steel
Permanent Backing
Al

12. Pre-Heating
Not necessary – increase the width of the HAZ & Reduce the mechanical properties
Sometime higher thickness need pre-heat (<165 C)
If Mg= 3%-5.5% ----- Pre-heat (<120 C) & Interpass temp (<165 C)
Tack Welding
Used to Hold the component parts
To attach tab-in and tab-out
Improper tack weld- Leads to porosity in welds and
incomplete fusion

13. Porosity
Welding Problems
•Porosity- H2 solidification of weld bead
•If in the form of large discontinuous cavities or
long continuous holes - Due to excessive current-
this defects is know as tunneling
In the case of GMAW of aluminum wrought products,
the filler electrode, shielding gas, and base-metal surface
contaminants may contribute to gas porosity.
HYDROGEN SOLUBILITY IN PURE ALUMINUM

14. Cracking
•Solidification cracking
•Liquation cracking
•Stress corrosion cracking
Solidification cracking, or hot tearing, occurs when high levels of thermal stress and solidification shrinkage.
The hot tearing sensitivity of aluminum alloy is influenced by a combination of mechanical, thermal, and metallurgical
factors.
Hot tearing occurs within the weld fusion zone and is affected by weld-metal composition and welding parameters.
High heat inputs, such as high currents and slow welding speeds
It follows that processes that result in minimal heat input, such as electron-beam welding, reduce weld crack sensitivity.
The primary method for eliminating cracking in aluminum welds is to control weld-metal composition through filler
alloy additions.

15. Crack sensitivity, determined experimentally as a function of weld composition, is shown in for various binary aluminum
systems (Al-Li, Al-Si, Al-Cu, Al-Mg, and the quasibinary Al-Mg2Si)

16. Liquation Cracking
An important element of the HAZ for precipitation-hardenable alloys is the thin boundary layer adjacent to
the fusion zone that is referred to as the partially melted region.
This region is produced when eutectic phases or constituents that have low melting points (melting points
below the melting point of the bulk material) liquate, or melt, at grain boundaries during welding

17. Joint Design
Root opening and large groove angle are normally used because Al is more fluid.
V-groove angle – 600 t > 3mm, for higher thickness J-Groove is used.
Electrode selection
W Electrode selected based on the welding current
Pure tungsten (EWP)
Zirconated tungsten (EWZr) Electodes
Thoriated tungsten electrode (EW Th-3)
EW Th -1 or EW Th-2
Used for DC or SWAC
( Both have higher emissivity,
better current carrying capacity and
long life than other electrodes)
Used for conventional AC
(Keep Hemisphere shape)
GTAW of Al alloys

18. Shielding Gas:
Ar is most commonly used shielding gas
Provides better arc starting characteristics than He gas and improve cleaning action
He is used - Machine welding with DCEN power
- Welding at higher speed
- Greater penetration than Ar
He-Ar mixture - 75He-25Ar – higher travel speed
- 90He-10Ar – better arc starting characteristics with DC than pure He

19. Conventional AC (50 HZ)
Ar or Ar-He mixture shielding gas are used
Surface oxide is removed by arc action.
Bright weld bead with silvery border indicates proper gas shielding and arc cleaning
Oxide weld bead – due to unstable arc , low current input, poor shielding gas
or excess arc length
Welding Procedure
Power supplies
I) Conventional AC (50 HZ)
II) DC with electrode negative (DCEN)
III) DC with electrode positive (DCEP)
IV) Square wave AC (SWAC)

20. DC with electrode negative (DCEN)
DCEN power - Advantages than Ac power
(short arc length, thin sections, higher welding speed)
Surface appearance – Dull – due to formation of thin oxides films
(because cleaning action is only done by electrode +ve)
But oxide layer is layer is removed by wire brushing.
Ar shielding gas is used – but penetration is less than He shielding gas
Square groove – used for higher thickness
In V- groove root space is higher than Ac arc weld.
DC with electrode positive (DCEP)
Good surface cleaning action
Section thickness < 1.25mm – because W electrode heating
Ar shield gas is used because He or Ar- He mixture makes electrode over heating
Weld backing are recommended

21. Square wave AC (SWAC)
SWAC – designed to produce a D.C. power with arrangement to rapidly shift the
polarity to produce A.C. waves from the adjustable frequency.
SWAC power – Combines the surface cleaning (AC power) and deep penetration (DCEN)
Ar shielding gas is preferred
Ar- He mixture or He are used were deep penetrations need.
x

22. GMAW of Al alloys
Electrode Feeding
feeding system - Push , Pull or Push-Pull are used depends on wire material and
mode of welding (Semi-Automatic Welding & Automatic Welding)
Shielding gas
Ar -Mostly used for manual welding with
spray type metal transfer.
(Provide excellent arc stability, bead shape ,
and penetration in all weld positions )
He- suitable for Machine and automatic welding
with high current.
He-Ar mixture – instead of He for arc stability provided by Ar
(20%-90% He used)
Increasing in He content – Increase Arc voltage, penetration and spatter

23. Semi-Automatic Welding
GMAW - Arc should be started at a location on the joint that will be melted
into the weld metal.
Arc should not start on the outside of base metal – because the arc strike might
cause surface discontinuity – cause failure at service time.
End of the nozzle – 20mm above the base metal (reduced during Al-Mg alloys to avoid
loss of Mg vaporization )
Short arc – for small fillet weld
Low voltage – cause excessive spatter tends to increase porosity
High voltage – cause incomplete root penetration and contamination of weld metal
So, For first pass low voltage is used and for other passes the higher voltage is used

24. Heat treatable Al Alloys – Stringer bead technique is used and cooled to 650 C between passes with this
Heat input is minimized and HAZ is narrow
Non-Heat treatable Al alloys(5xxx) - welded with larger beads
Biggest dia electrode – section thickness, joint design & welding position
Larger dia electrode – favorable for surface to volume ratio- minimize porosity
Automatic Welding
Higher travel speed than Semi-automatic welding
Longer joints welded without interrupting in welding
This reduce no. of weld craters cracks
Higher current can be used
Square groove – upto 13mm can weld with single pass
25mm can weld with single pass with higher current and large electrode

25. Welding of titanium alloys

26. Physical properties of titanium
• Crystal structure
• HCP (<882.5oC)
• BCC (>882.5oC)
• Density (g.cm-3) 4.54
• Melting point - 1667 oC
• Experiences allotropic transformation (α ->β) at 882.5oC.
• Highly react with oxygen, nitrogen, carbon and hydrogen.(Burn in pure O2 at 600oC)
• Difficult to extract & expensive.
• Used mainly in wrought forms for advanced applications where cost is not critical.
• High strength and toughness

27. Advantages of titanium alloys

28. 1. Commercially pure (CP) titanium
2. Alpha titanium alloys and
3. Near Alpha titanium alloys(Ti-5Al-2.5Sn)
• Generally non-heat treatable and weldable
• Medium strength, good creep strength, good corrosion resistance
4. Alpha-beta titanium alloys(Ti-6Al-4V & Ti-5Al-2Sn-2Zr-4Mo-4Cr)
• Heat treatable, good forming properties
• Medium to high strength, good creep strength
• Weldability depends on beta %, High beat alloy % causes
embrittlement
5. Beta titanium alloys(Ti-13V-11Cr-3Al)
• Heat treatable and readily formable
• Very high strength, low ductility
• Good Weldability at annealed conditions – ageing – high strength
Classification of titanium alloys

29. Alloying system of titanium
Alpha stabilisers
Al, O, N
Beta stabilisers
Mo, V, W, Nb, Ta, Fe, Cr, Cu, Ni, Co, Mn.
Neutrual
Zr, Si, Sn

30. Welding of titanium alloys
• α and α+β titanium alloys are readily weldable.
• β titanium alloys are not readily weldable due to high
amounts of alloying element  macro/micro segregation.
• Tungsten Inert Gas Welding
• Electron Beam Welding
• Laser Beam Welding
• Friction welding

31. • Most widely used technique for titanium welding.
• Require no vacuum
• Lower operating cost
• Provide relatively coarser weld structure than those
obtained from EBW and LBW.
• High heat input  relatively high distortion.
Tungsten inert gas welding
Arc is produced between a nonconsumable
tungsten electrode and the metals in the presence
of shielding gas (He, Ar).

32. • Electron beam is used as a heat source.
• Vacuum and non-vacuum process clean.
• Relatively high operating cost and equipment.
• Multiple or single -pass arc welding
• Low heat input  minimum distortion
Electron beam welding

33. • Laser is used as a heat source.
• Correct choice of shielding gas
• Adequate shielding methods
• Pre-cleaning (de-greasing)
• Good joint surface quality
Laser beam welding
Advantages of laser beam welding
• High productivity (nearly 10 times faster than
TIG).
• Low heat input and therefore low distortion.
• Ease of automation for repeatability.
• No need for filler wire, thus reducing costs

34. Friction welding is carried out by moving one part in a
linear reciprocating motion to effect the heat at the
joint.
• High cost of welding machines.
• Can use to join dissimilar metals.
• Very small distortion.
• Limited to non-round and non-complex component.
Friction welding

35. • Titanium and titanium alloys are highly reactive to oxygen, therefore care
must be taken for titanium welding.
Should be carried out in vacuum or appropriate shielding gas such as Ar or He.
The main defects occur in titanium welding are;
• Weld metal porosity
- Most frequent defects caused by gas bubbles trapped between dendrites
during solidification.
• Embrittlement
- Due to oxygen, nitrogen or hydrogen contamination at T> 500oC. need
effective shielding.
• Contamination cracking
- Due to iron contamination reducing corrosion resistance, separate from steel
fabrication.
Defects in titanium welding
Macroscopic pore observed in TIG
welding of beta titanium alloy

37. Welding of Copper Alloys

38. Copper And Copper Alloys
• Excellent electrical and thermal conductivities
• Outstanding resistance to corrosion
• Ease of fabrication
• Good strength and fatigue resistance

39. Copper Alloys
• COPPERS, WHICH CONTAIN A MINIMUM OF 99.3% CU
• HIGH-COPPER ALLOYS, WHICH CONTAIN UP TO 5% ALLOYING ELEMENTS
• COPPER-ZINC ALLOYS (BRASSES), WHICH CONTAIN UP TO 40% ZN
• COPPER-TIN ALLOYS (PHOSPHOR BRONZES), WHICH CONTAIN UP TO 10%
SN AND 0.2% P
• COPPER-ALUMINUM ALLOYS (ALUMINUM BRONZES), WHICH CONTAIN UP
TO 10% AL
• COPPER-SILICON ALLOYS (SILICON BRONZES), WHICH CONTAIN UP TO 3% SI
• COPPER-NICKEL ALLOYS, WHICH CONTAIN UP TO 30% NI
• COPPER-ZINC-NICKEL ALLOYS (NICKEL SILVERS), WHICH CONTAIN UP TO
27% ZN AND 18% NI

40. Factors Affecting Weldability
• Effect of Thermal Conductivity.
• Cu has high thermal conductivities
• the type of current and shielding gas must be selected to provide maximum heat
input to the joint
• preheating may be decided based on thickness
• Counteracts the rapid head dissipation
• Cold worked Cu alloys tend to become weaker and softer at HAZ
hot cracking may occur in heavily cold worked
• Welding Position
• highly fluid nature
• flat position is used whenever possible
• Vertical, overhead and the horizontal position- seldom used

41. • Precipitation-Hardenable Alloys
• Beryllium, chromium, boron, nickel, silicon, and zirconium.
• Care must be taken to avoid oxidation and incomplete fusion.
• Reduction in mechanical properties due to overageing
• Should be welded in the annealed condition, followed by precipitation hardening treatment
• Hot Cracking
• copper-tin and copper-nickel, are susceptible to hot cracking
• wide liquidus-to-solidus temperature range
• Severe shrinkage stresses produce interdendritic separation during metal solidification

42. • Porosity
• zinc, cadmium, and phosphorus have low boiling points.
• Vaporization of these elements during welding may result in porosity.
• Higher travel speed and filler metals with less volatile element content
• Surface Condition
• Oxides formed are difficult to remove
• Cleaning and shielding helps to avoid oxide formation

43. Welding of Cu
• Difficulties: High oxygen content and impurities
• Electrode: Ecu and filler: ERCu
• Preheating : thickness, conductivity

44. Preheating

45. Effect of shielding gas

46. • GTAW
• Upto 3.2mm thickness but more for flat position
• Shielding: upto 1.6mm Ar and over 1.6mm He, deeper penetration
• Pulsed current can be used
• GMAW
• Shielding: Ar or mixture of Ar and He
• Filler: ERCu
• Spray transfer and pulsed current
• SMAW
• ECuSi, ECuSn-A
• DCEP
• Flat position

47. Other processes for welding of Cu
• Laser beam welding
• Difficulties: high reflection of laser beam and high thermal conductivity
• Absorption increases with temperature
• Shorter wavelength has better welding
• Electron beam welding
• Thin and thick sections
• Resistance spot welding
• Lower conductivity alloys readily spot welded
• Not practical for unalloyed Cu

48. • Flash welding
• Leaded Cu (upto 1% Pb) can be flash welded
• Rapid upsetting at minimum pressure
• Low melting point and narrow plastic range
• Premature termination of current: lack of fusion
• Delayed termination: over heating
• Solid state welding
• Annealed Cu can be welded at room temperature: good malleability
• Diffusion welded or explosive welding

50. Welding of Nickel Alloys

51. Crystal structure FCC
Atomic number 28
Atomic weight 58.71
Density (g.cm-3) 8.89
Melting point (oC) 1455
Nickel and its alloys
Properties
• Silvery shiny appearance
• High toughness and ductility
• Good high and low temperature strength
• High oxidation resistance
• Good corrosion resistance
• Ferro-magnetic
• Relatively high cost
• Not mixed with cheap alloying elements.

52. The defects and metallurgical difficulties encountered in the arc welding of
nickel alloys include:
• Porosity
• Susceptibility to high-temperature embrittlement by sulfur and other
contaminants
• Cracking in the weld bead, caused by high heat input and excessive
welding speeds
• Stress-corrosion cracking in service
Weld Defects in nickel

53. Porosity
Oxygen, carbon dioxide, nitrogen, or hydrogen can cause porosity in welds.
Presence of deoxidizers or nitride-forming elements (aluminum and
titanium) in SMAW and SAW processes type of electrode serves to reduce
porosity.
These elements have a strong affinity for oxygen and nitrogen and form
stable compounds with them.

54. Cracking
Hot cracking of welds can result from contamination by sulfur, lead, phosphorus, cadmium, zinc, tin, silver,
boron, bismuth, or any other low-melting-point elements, which form intergranular films and cause severe
liquid-metal embrittlement at elevated temperatures.
Cracking in the heat-affected zone is often caused by intergranular penetration of contaminants from the base-
metal surface. Sulfur, which is present in most cutting oils used for machining, is a common cause of cracking in
nickel alloys. The removal of foreign material from the surfaces of the work metal is imperative.
Weld metal cracking also can be caused by heat input that is too high, as a result of high welding current and
low welding speed. Welding speeds have a large effect on the solidification pattern of the weld. High welding
speeds create a tear-drop molten weld pool, which leads to uncompetitive grain solidification at the center of
the weld. At the weld centerline, residual elements will collect and cause centerline hot cracking or lower
transverse tensile properties.
In addition, cracking may result from undue restraint. When conditions of high restraint are present, as in
circumferential welds that are self restraining, all bead surfaces should be slightly convex. Although convex
beads are virtually immune to centerline splitting, concave beads are particularly susceptible to centerline
cracking. In addition, excessive width-to depth or depth-to-width ratios can result in cracking that may be internal
(that is, subsurface cracking).

55. Stress-Corrosion Cracking
When the alloys are intended to contact substances such as concentrated caustic
soda, fluorosilicates, and some mercury salts,
The welds may need to be stress relieved to avoid stress-corrosion cracking.
Effect of Slag on Weld Metal
If slag is not removed in the latter type of application, then crevices and
accelerated corrosion can result.
Slag inclusions between weld beads reduce the strength of the weld.
Fluorides in the slag can react with moisture or elements in the environment to
create highly corrosive compounds.