Welding of Non – Ferrous
Metals and Alloys
Contents





Aluminium and aluminium alloys
Copper and copper alloys
Nickel and nickel alloys
Titanium and its alloys
Magnesium and its alloys
What are non-ferrous alloys?
 Alloys in which iron (Fe) is not the
major component are termed as NonFerrous Alloys
Common non-ferrous metals
(All metals and alloys in which iron is not the
major component are termed as non-ferrous)





Copper
Nickel
Aluminum
Titanium
Magnesium
Cu
Steel
Ti
Al
Be
Attractions:
Low density
High environmental resistance
Low DBTT
Mg
0
2
4
6
8
Density (kg/m3)
Applications in aerospace, automobile, chemical, petro-chemical, and
several other industries.
10
Common non-ferrous metals
Free energy of formation of some non-ferrous metal oxides
A large negative free energy shows a strong affinity for oxygen. This
property has a major influence on the type of shielding required during
welding and the processes that can be used.
Important Properties of Aluminium









Pure Al. - Low strength
:70-90 MPa.
Al. Alloys - Mod. Strength
: 90-500 MPa.
Light weight
: D  2.7 g/cc.
High strength to weight ratio.
Good corrosion resistance and non toxic.
Ductile. Good ductility at subzero temperature
Good formability.
Low temperature toughness.
High electrical and thermal conductivity.
Applications
 Transportation
 Aerospace & Defence
 Building & Architecture
automobile, railway,
marine
Aircraft, launch vehicles for
space & missiles, naval ships,
speedboats
 Packaging, Containers, Cryo-vessels
 Electrical cables & Bus-bars
 Household & consumer durables
 Machinery
General consideration for Fusion
Welding
Most of Al. alloys are weldable. Some are of course
sensitive to cracking. Only it is necessary to
understand that Welding characteristics of
aluminium are distinctly different from those of steel.
Problems in Welding Aluminium:
High affinity for oxygen.
High thermal conductivity.
Softening in HAZ of age hardened alloys.
Susceptibility to cracking.
General consideration for Fusion
Welding
High affinity for oxygen results in quick
formation of tenacious Aluminium Oxide skin.
 Melting temp.of Al. oxide is high (2050C)
 3 times of Aluminium ( 650C)
 Al. Oxide promotes lack of bonding.
 In-process cleaning of oxide is achieved by
cathodic cleaning in TIG and MIG welding.
(Meticulous cleaning before welding required)
Problems in Welding Aluminium
Al. oxide skin
Mp.2050°C
Aluminium
Mp.650°C
Aluminium metal melts.
Aluminium oxide skin remains
unmelted.
Aluminium oxide in weldpool impedes bonding
Problems in Welding Aluminium
High affinity for oxygen
Solution: In-process cleaning
of oxide during welding is
required.
Cathodic cleaning of oxide is
utilized in AC TIG welding in
Electrode + half cycle.
Oxide cleaning
in DCEP mode
Problems in Welding Aluminium
Softening in HAZ in Age Hardened alloy.
Reasons:
Re-solutionizing of age hardening
precipitates.
Over-ageing of precipitates.
Resolutioned B.M
Weld
Unaffected
B.M
Resulting in:
Joint Efficiency in as welded condition
60-70% of age hardened alloy.
Over aged B.M
Cracking
 In general the non-heat treatable aluminium
alloys can be welded with a filler metal of the
same basic composition as the base alloy.
 The heat-treatable alloys are most sensitive to
‘hot short’ cracking during welding. A
dissimilar filler metal having a lower melting
temperature and similar or lower strength than
the base metal is used.
 Solidification cracks in weld.
 Liquation cracks in weld & HAZ (PMZ)
Cracking in Aluminium Alloy
Welding --- Prevention
1.
Select an weldable alloy, which is less crack
susceptible.
2.
3.
Select a filler alloy to avoid crack sensitive weld
metal composition.
Dilution can lead to crack
Use less heat-input.
4.
Avoid rigid clamping / fixtures.
sensitive weld composition
Sq.butt jt. Max dilution
B.M :1100, F.M: 4043 (Al-5% Si)
If Dilution : 80%
Weld metal will have about 1% Si
which is crack sensitive
Less Dilution in V-groove
Cracking in Aluminium Alloy
Welding --- Prevention
Crack sensitive Base Metals usually have wide solidification range.
(Large difference between Solidus and Liquidus temperatures is
caused by minor alloy additions made to increase strength).
Alloy
Composition
Solidus
ºC
Liquidus
ºC
Weld rating
Strength
MPa
7075
Zn: 5.6
Mg: 2.5
Cu: 1.6
477
635
C
572 (T6)
7079
Zn: 4.3
Mg: 3.3
Cu: 0.6
482
638
C
538 (T6)
7178
Zn: 6.8
Mg: 2.8
Cu: 2.0
477
629
C
607 (T6)
Cracking in Aluminium Alloy
Welding --- Prevention
Avoid Crack Sensitive Weld Metal Composition
Mg2Si
Cracking susceptibility with Al-Mg2Si Addition.
6xxx BM if welded w/o filler, or same filler : Weld Metal will
be in Crack Sensitive Range.
Recommended Filler :4043(Al-5%Si), 5356 (Al-5%Mg)
Cracking in Aluminium Alloy
Welding --- Prevention
Avoid Crack Sensitive Weld Metal Composition
(A) Without filler addition
(B) With filler addition ER 5356
6061 pipe welding (Root run )
Filler Metal Selection Criterion
1. Base metal composition.
2. Ease of welding / Freedom from Cracking tendency.
3. Strength and ductility of the weld.
4. Corrosion resistance.
5. Service temperature.
6. Colour match between weld and base metal after
anodising.
Welding processes for Aluminium
and Aluminium alloys
Most widely used processes :
 AC TIG
 MIG (conventional)
Other Special processes :
DCSP TIG
Pulsed MIG
Plasma Arc Welding (key hole mode)
Electron Beam Welding
Welding processes for Aluminium and
Aluminium alloys
AC TIG Welding of Aluminium

Most widely used method to weld Al.

Good oxide cleaning by the arc.

Average penetration.

Suitable for manual welding in all positions and
mechanised welding.

Use pure or zirconiated tungsten electrodes with
hemispherical tip.
DCSP TIG Welding of Aluminium and
Aluminium alloys
Requirements:
Advantages:
Short arc length
Weld and HAZ width are narrower.
Less softening of HAZ.
Helium shielding
Sq. butt joints produced in Single pass
Mechanised welding
Faster welding speed
Top Bead
DCSP TIG Weld, 7.4mm Sq. butt
Single Pass, 350mm /min.
Root Penetration Bead
DCSP TIG Weld, 7.4mm Sq. butt
Single Pass, 350mm /min.
MIG Welding of Aluminium and
Aluminium alloys
MIG Welding of Aluminium requires
“Spray” type of metal transfer.
Process Options :

Conventional MIG (Un-pulsed)

Pulsed MIG.
MIG Welding of Aluminium and
Aluminium alloys
Spray type of metal transfer
 Has a typical fine arc column with
pointed wire tip.
 Very small drops are formed and
detached at rate of hundreds per sec.
 Drops are accelerated axially across
the arc gap. (helps in overhead
welding).
MIG Welding of Aluminium and
Aluminium alloys
Pulsed MIG Welding
Welding current is pulsed
between a high peak
current (in the spray
region) and a low
background current (below
spray region) in a given
pulsing frequency.
Average current remains
below spray region, but
with spray transfer.
Key-Hole Plasma Arc Welding of Aluminium
and Aluminium alloys
PAW in Key hole
Advantages :
Clean weld.
Square Butt Joint in
single pass upto
8mm thickness.
Current, ampere
mode produces a
small weld pool with
a hole penetrating
thro’ the joint.
Electrode
negative part
time, ms
Electrode
positive part
Variable Polarity Wave Form for Plasma
Key-hole Welding of Aluminium
Electron Beam Welding of Aluminium
Advantages :
Welding of very thick plates.
Narrow weld bead.
Narrow HAZ.
High speed welding in thin sheets
Disadvantages :
High Cost.
Vacuum Chamber required.
Shielding Gases for TIG & MIG welding
of Aluminium Alloys
Argon (AC TIG, MIG).
Helium (DC TIG, MIG).
Argon-Helium mixture.
(80/20 – AC TIG), (50/50 - MIG)
Control of impurity important for high quality welds.
Moisture, oxygen, nitrogen and hydrocarbons are impurities.
Welding Techniques for Aluminium
Always Forehand and
Vertical up in Welding
Aluminium
6’O clock to 12’O clock in
5G positional welding.
Use min. or no preheat.
Preheat <200ºC.
Direction of welding
Stringer bead preferred.
Avoid wide weaving.
Direction of welding
Defects in Aluminium welds
1. Pores
2. Lack of fusion/bonding.
Remedy: Adjust parameter (heat input),
Improve cleanliness.
3. Cracks
Remedy: Reduce heat input,
Select proper B.M
& filler metal combination.
Defects in Aluminium welds
Pores :
Caused by dissolution of
hydrogen in weld metal.
Causes :
Impurity from gas,
filler metal, base metal
and environment.
Remedy:
Keep B.M., F.M. clean.
Use argon with high purity
(Controlled moisture content).
Note : Aluminium has a very low
solubility for hydrogen at the
freezing point but a substantial
solubility at higher temperature.
Thus hydrogen is prime cause of
porosity in aluminium welds.
Applications & relevant properties
of Copper & its alloys
Applications
Relevant Property
Electrical conductors, bus Electrical conductivity
bars
Tubing
Ductility, corrosion
resistance
Chemical Plants
Corrosion resistance
Valves, fittings, marine
propellers
Corrosion resistance
Copper and Copper alloys
Copper is a ductile metal and it has a low melting point but very
high thermal and electrical conductivity. It is used primarily for its
electrical and thermal properties and its excellent corrosion
resistance in certain environments, particularly sea water.
Copper is available in 3 forms
•Tough pitch copper – oxygen bearing
•Phosphorous de-oxidised copper
•Oxygen-free copper
Copper forms solid solution with a wide range of elements. The
most important alloys are :
Copper alloys
Alpha Brasses (upto 30% Zn )
Single phase solid solution & work
hardening. Improved corrosion
Alpha-beta brasses eg. muntz metal
(40% Zn), naval brass (40Zn-1Sn)
2-phase solid solution hardening.
Improved corrosion
Nickel silvers ( 20 – 45% Zn + Ni )
Improved strength and corrosion
resistance
Phosphor bronze (10% Sn),
Gun metal ( P-Bronze +5%Zn )
Si-bronze (3% Si),
Improved strength and corrosion
resistance
Al bronze (5-10% Al + Fe / Ni ) - single
phase
Al Bronze ( 12%Al + 5%Fe) 2-phase
Improved strength and corrosion
resistance
Cupro-nickels
( upto 30%Ni )
Moderate strength, corrosion and
oxidation resistance
Cu-chrome , Cu-Be alloys
Precipitation hardening alloys for high
strength
Weldability of copper and its alloys.

Pure copper – High conductivity requires pre-heat above 5mm
thickness. Porosity and embrittlement in HAZ in tough pitch copper
and porosity in autogenous welds of P-deoxidised copper

Brasses - Zinc vaporization during welding gives porosity and toxic
white fumes of zinc oxide. Low Zinc brasses ( upto 20% ) weldable
by fusion welding with zinc free filler metal. Higher Zinc brasses
difficult to weld. Brazing or braze-welding preferred.

Tin and phosphor Bronzes – susceptible to hot cracking

Al – Bronze – Formation of Al oxide thus gas shielded processes
preferred TIG ( AC ) or MIG. Low thermal conductivity – no pre-heat.

Copper – Be or Copper – Cr alloys - Precipitation hardening alloys
reduction in strength / cracking in HAZ. Weld in solution annealed
condition and then heat treat

Cupro – nickels – Single phase good weldability. Susceptible to hot
cracking in presence of sulphur.
Copper / Pre-heat Requirement
Thermal conductivity of copper is
more than 6 – 7 times that of steel.
Due to high thermal conductivity of
copper, heat moves away quickly
from the weld. Supplemental heat
given in the form of Pre-heat to
create adequate molten pool.
Pre-heat temperature depends on
copper alloy composition,
thickness, welding process and
shielding gas.
Joining processes for Copper and
copper alloys
SMAW – Normally used for maintenance and surfacing of worn
out parts with Si- bronze or Sn- bronze electrodes
GTAW – Argon or Ar + He mixtures ( increased heat input ). AC
used for Al-Bronze and Cu-Be alloys.
PAW – Advantage of reduced Tungsten inclusion and lower
furmes in Cu – Zn, Cu-Sn and Cu-Al alloys
GMAW – Ar + He mixtures used for heavier sections
Gas welding – Can be used for pure copper
Brazing / Braze welding – Widely used ( except for Al-bronze)
with Cu-P, Cu-Ag-P & Si-bronze alloys
Nickel and Nickel alloys
 Nickel has FCC structure over the complete
range of temperature upto its melting point. This
structure makes nickel ductile.
 Nickel is useful as an engineering material for its
corrosion resistance and its excellent high
temperature properties when appropriately
alloyed.
 Applications: Chemical and Petro-chemical plant
piping and heat exchangers, Food processing
equipment, Breweries, aero-engine parts etc.
Applications & relevant properties
of Nickel & its alloys
Applications
Relevant Property
Food Processing
Equipments
Corrosion resistance
Chemical Plants
Corrosion resistance
High temperature vessels High temperature strength
Aero-engine parts
Nickel alloys
 Copper and nickel have complete solubility
 Monel with 30-45% copper
 Ni-Cr (Nimonic) and Ni-Cr-Fe (Inconel) alloys
 Solid solution strengthened
 Corrosion and oxidation resistance
 Precipitation hardened alloys (with Al, Ti and
Nb)
 High temperature service
 Hastelloys (Ni-Cr-Mo and Ni-Mo alloys)
 Precipitation hardening
 Excellent corrosion resistance
Fig. Phase diagram for the copper-nickel system.
Note the complete range of solid solubility.
Nickel and Nickel alloys
Nickel Pure nickel ( Nickel 200 )
Monel 400 ( 70Ni / 30Cu )
Solid solution, moderate
strength, good corrosion
resistance
Ni-Cr alloys - Nimonic 75,
Brightray S
Solid solution
Ni-Cr-Fe alloys - Inconel 718, Solid solution / precipitation
Inconel 600 Inconel 800
hardening
Ni-Mo alloys Hastealloy B-2
Ni-Cr-Mo alloys Hastealloy
C-22, Inconel 625
Precipitation hardening strength & improved
corrosion resistance
do
Weldability of Nickel and its alloys.
 Solid solution alloys are generally welded in the annealed
condition, have good weldability and normally do not require any
post weld heat treatment..
 Precipitation hardening alloys are subject to post weld heat
treatment cracking in the weld or HAZ. To be welded in solution
annealed condition and then aged. In specific applications in HF
acid or fluo-silicates stress relief is given to prevent SCC.
 Porosity – caused by O2, N2 from air or oxides and H2 grease etc
 Susceptibility to high temperature embrittlement by S, Pb, P and
other contaminants existing in grease, paint, cutting fluids snd
lubricants. Plates must be thoroughly cleaned before welding
 Hot cracking due to sulphur etc and excess heat input and stress.
 Oxide inclusions and lack of inter-run fusion. Oxides are very high
melting and may not fuse fully during welding
Hot Cracking in Nickel & its alloys
•
Nickel and many of its alloys are prone to hot cracking in
the weld metal due to sulphur and other impurities
Fig. Part of the nickel-sulphur phase diagram. Note the lack of
solubility of sulphur in the solid nickel and the low melting
point - 1175°F (635°C) of the eutectic.
Welding processes for Nickel and
Nickel alloys
SMAW – Suitable for all alloys with matching filler
metal. Ti Al and or Nb maybe added to minimise risk
of porosity and cracking.
GTAW – Argon, Ar-He or Ar-H2 mixtures maybe
used. Back purging recommended to avoid porosity.
GMAW – Argon and Ar -He mixtures (used for heavier
sections )
SAW – Restricted to solid solution alloys, less widely
used.
Basic considerations in Welding Nickel
Higher thermal conductivity than carbon and alloy steels attributes
great difficulties in fusion.
To minimise fusion problem joint should be design with wide angles.
Fig. Typical joint preparations for welding nickel. Even with
thin material filler metal is necessary.
Titanium and its Alloys
 Titanium has an HCP structure, the alpha phase, at room
temperature but undergoes a transformation to BCC, betaphase, on heating about 885°C.
 Most alloy elements stabilizes the beta-phase and allow
beta-phase to be present in the microstructure at room
temperature.
 Aluminium, however, stabilizes the alpha-phase.
 The presence of beta-phase improves toughness, increases
strength, enhances hot working behaviour, but generally
has a negative effect on weldability.
 Titanium alloys of the alpha-beta or beta type can be
strengthened through heat treatment involving solution
treating, quenching and aging.
TITANIUM & its ALLOYS
Silver coloured, reactive, exotic metal.
High specific strength, modulus & toughness.
Exceptional corrosion and fatigue resistance.
High temperature serviceability.
Lighter than steel
(D  4.5g /cc).
LIMITATIONS
 High Reactivity at Elevated Temperature.
 HIGH COST.
 Fusion welding with steel or most other
metals not feasible.
 Used only for Special Applications
Applications & relevant properties
of Titanium & its alloys
Applications
Relevant Property
Aerospace, Defence
Sports Equipments
Low Density, High strength
Chemical plants
Surgical implants
Marine application
Corrosion resistance
High resistance to sea
water corrosion
Titanium alloys
Titanium
Pure titanium ( 98.5-99.5% )
Work hardening
Alpha alloys (Ti-3Al-2.5V)
Solution & work hardened
Alpha-beta alloys (Ti-6Al-4V) Age hardened
Beta alloys (Ti-3Al-13V-1Cr)
Age hardened
Weldability of Titanium Alloys
Material
Weldability issues
CP Ti and α alloys
Weldable
Good ductility (α′ forms, but it is not brittle
(low β stabilizing elements))
Near-α and α+β
alloys
Weldable
Inferior ductility (large amount of α′)
Metastable β alloys
Weldable
Good as-welded ductility
Low strength
Segregation problems
Basic Characteristics
 Ti oxidises rapidly at elevated temperature.
 Ti dissolves O2, N2, H2 interstitially at high
temperature encountered in welding causing
embrittlement.
 Inert gas shielded welding methods needed.
 Requires additional shielding of hot solidified
weld bead till cooled to 350ºc.
Special Requirements

Primary shielding of the weld pool thro’ the TIG
torch alone is not adequate.

Solidified hot weld & HAZ on the trailing side of the
torch to be provided shielding till cooling down to below
300C.

Underside (root) of the weld joint also to be
protected with inert gas shielding.

Colour of weld indicates contamination with
atmosphere and brittleness
Welding of Titanium Alloys
 Extremely reactive and sensitive to contamination
 GTAW, GMAW, PAW
 High purity shielding gases
 Backing and trailing gas arrangements
 Glove box welding
 No serious hot cracking problems
 Matching fillers often used
 Limited availability of filler wires
 Undermatching fillers with generous reinforcement
 Go for EBW and LBW
 Most alloys suffer from poor weld ductility
Joining Processes for Titanium
FUSION WELDING PROCESSES:
TIG WELDING
MIG WELDING
PLASMA ARC WELDING
ELECTRON BEAM WELDING
TIG Welding of Titanium
WELDING IN INERT ATMOSPHERE CHAMBERS
(FLOW PURGED & VACUUM PURGED).
OPEN AIR WELDING WITH AUX. SHIELDING.
TIG Welding of Titanium
WELDING IN INERT ATMOSPHERE CHAMBER :
Welding in Flow
purged chamber
Welding in Vacuum
purged chamber
TIG Welding of Titanium
OPEN AIR WELDING WITH AUXILIARY SHIELDING:
Primary shielding
: Thro’ TIG torch
for weld-pool
Secondary shielding
: Thro’ Trailing shield for
solid weld & HAZ.
Back side shielding
: Thro’ Grooved backing
bar for root bead shielding
Open Air Ti Welding
Root shielding
gas inlet
Protection of solidified weld & HAZ with
trailing shield (Ar)
TIG torch
Open Air Ti Welding
TIG welding of titanium pipe
with trailing shield
Contamination colours in
Titanium welds.
Shining Silver colour
Reqd. No oxidation.
Golden colour.
Slight oxidation.
Mostly accepted.
Oxidised bead.
Not acceptable.
Highly Oxidised bead.
Not acceptable.
Magnesium and its alloys
 Magnesium is very light metal with good
corrosion resistance making it suitable for a
wide range of applications including aerospace, highspeed equipment such as
printing
machines,
material
handling
equipment, ladders and light weight casting.
 Magnesium has a HCP structure that renders
it difficult to cold work.
 Forming operation are always carried out hot
between about 200-300°C.
Magnesium and its alloys
(Contd.)
• The elements is highly reactive with
oxygen and the magnesium powder can
ignite and burn spontaneously in air.
• The addition of beryllium upto 0.001%
reduces the tendency to ignition and filler
metal for GMAW and GTAW commonly
have 0.0002- 0.0008% beryllium
Its low density is the most
important property of magnesium
Metal
Density
lb/ft3
kg/m3
Steel
489
7.83
Aluminum
173
2.77
Magnesium
111
1.78
Applications & relevant properties
of Magnesium & its alloys
Applications
Relevant Property
Printing equipment
Low Moment of Inertia
Conveyors, ladders
Low Density
Aerospace
Low Density
Magnesium and its alloys
 Over 50% of Mg produced is consumed in:
 Al alloys
 Removal of sulfur from iron and steel
 Most Mg alloys are cast alloys
 Mg-Al-Zn system still dominates




Al, Zn Alloying for precipitation hardening
Mn improves corrosion resistance
Zr refines grain structure
Rare-earths increase creep resistance
Fig. Part of the phase diagram for the magnesium-aluminum
system. The rising solubility of aluminum in magnesium
allows this alloy to be precipitation hardened.
Common Mg Alloys
 AZ91: Mg-9Al-1Zn-0.2Mn
 General casting alloy
 Properties
 Yield Strength: 100MPa
 UTS: 165MPa
 Ductility: 2.5%
 AE42: Mg-4Al-2.5RE
 Mg engine blocks
 Properties
 Yield Strength: 145MPa
 UTS: 235MPa
 Ductility: 11%
Common Mg Alloys
 ZK60: Mg-5Zn0.5Zr
 Forged car wheel
 Properties
 Yield Strength:
270MPa
 UTS: 325MPa
 Ductility: 11%
Weldability of Mg alloys
 Problems with MgO
 Mechanical cleaning essential
 Preferred polarity: AC
 Low Zn (up to 2%) alloys are fusion
weldable
 Ca promotes hot cracking
 Welds normally fail in HAZ (grain
coarsening)
Fig. For a given current the volume of weld metal deposited
from a magnesium electrode is more than three times that
from a steel electrode.
Welding processes for Magnesium
and Magnesium alloys
GTAW – Argon or Ar-He mixtures maybe
used. Back purging recommended to avoid
porosity.
GMAW – Argon and Ar -He mixtures (used for
heavier sections )
Other processes - PAW, EBW, Laser and
Friction and resistance welding
Joint design
Fig. Typical joint geometries for GMAW in magnesium
Thank You