Download - 4 Unit 2- Solid State Welding (SSW)
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
1/33
MANUFACTURINGTECHNOLOGY ISUBCODE: MEC230
Unit 2Welding (Metal Joining) Processes
Metal Forming Processes
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
2/33
Unit 2 : Solid State Welding (SSW)
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
3/33
Solid State Welding (SSW): Solid State Welding two pieces are joined under pressure& at a
temperatureessentially below the melting point Bonding of the materials is a result of diffusionof their interface
atoms
Joining of parts is achieved by Pressure, or Heat & pressure
If both heat and pressure are used, Heat is not enough to meltwork surfaces
For SSW processes, time is also a factor No filler metal is added
Each SSW process has its own way of creating a bond at the
surfaces
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
4/33
Solid State Welding (SSW): Essential factors for a successful solid state weld are
Very clean surfaces
In very close physical contact with each other to permit
atomic bonding
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
5/33
Advantages of Solid State Welding: No Melting, then no heat affected zone, so metal around joint
retains original properties
Weld is free from microstructure defects (pores, non-metallic
inclusions, segregation of alloying elements)
No consumable materials (filler material, fluxes, shielding gases)are required
Dissimilar metals may be joined (steel - aluminum alloy steel -
copper alloy).
Disadvantages of Solid State Welding: Thorough surface preparation is required (degreasing, oxides
removal, brushing/sanding)
Expensive equipment.
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
6/33
The following are Solid State welding processes : Forge Welding (FOW)
Cold Welding (CW)
Roll Welding (RW)
Diffusion Welding (DFW)
Explosive Welding (EXW)
Friction Welding (FRW)
Ultrasonic Welding (USW)
Hot Pressure Welding (HPW)
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
7/33
Forge Welding (FOW): Welding process in which components to be joined are heated to
hot working temperature range and then forged together byhammeringor similar means Historic significance in development of manufacturing
technology
Process dates from about 1000 B.C., when blacksmiths learned
to weld two pieces of metal
Prior to Forge Welding, the parts are joined by bevelling or
notching them so that they fit over or into each other in order to
prevent entrapment of oxides in the joint.
Forge Welding is used in general blacksmith shops and for
manufacturing metal art pieces and welded tubes.
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
8/33
Advantages of Forge Welding: Good quality weld may be obtained Parts of intricate shape may be welded
No filler material is required.
Disadvantages of Forge Welding: Only low carbon steel may be welded
High level of the operators skill is required
Slow welding process
Weld may be contaminated by the coke used in heating furnace
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
9/33
Forge Welding (FOW):
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
10/33
Cold Welding (CW):
SSW process done by applying high pressure between cleancontacting surfaces at room temperature by deformation Intimate contact between these pure surfaces provide a strong
and defectless bonding.
Cleaning usually done by degreasing and wire brushingimmediately before joining
No heat is applied, but deformation raises work temperature
At least one of the metals, preferably both, must be very ductile
Soft aluminium and copper suited to CW
Applications: making electrical connections
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
11/33
Cold Welding (CW):
Aluminum alloys, Copper alloys, low carbon steels, Nickel alloys,and other ductile metals may be welded by Cold Welding.
Cold Welding is widely used for manufacturing Bi-metal steel
Aluminum alloy strips, for covering of aluminum alloy strips by
other aluminum alloys or pure aluminum (Corrosion protectioncoatings).
Bi-metal strips are produced by Rolling technology
Presses are also used for Cold Welding
Cold Welding may be easily automated
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
12/33
Roll Welding (ROW):
SSW process in which pressure sufficient to cause joining bymeans of rolls, either with or without external heat
Variation of either forge welding or cold welding, depending on
whether heating of workparts is done prior to process
If no external heat, called cold roll welding
If heat is supplied, hot roll welding
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
13/33
Roll Welding (ROW) Applications:
Covering stainless steel to mild or low alloy steel for corrosionresistance
Bimetallic strips for measuring temperature
"Sandwich" coins
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
14/33
Diffusion Welding (DFW):
SSW process uses heat and pressure, usually in a controlledatmosphere, with sufficient time for diffusionand joining to occur Temperatures 0.4 Tm
Plastic deformation at surfaces is minimal
Primary joining mechanism is solid state diffusion
In order to keep the bonded surfaces clean from oxides and
other air contaminations, the process is often conducted in
vacuum. Limitation: time required for diffusion can range from seconds to
hours
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
15/33
Advantages of Diffusion Welding:
Dissimilar materials may be welded (Metals, Ceramics, Graphite,glass)
Welds of high quality are obtained (no pores, inclusions,
chemical segregation, distortions)
No limitation in the work pieces thickness
Disadvantages of Diffusion Welding: Time consuming process with low productivity
Very thorough surface preparation is required prior to weldingprocess
The mating surfaces must be precisely fitted to each other
Relatively high initial investments in equipment
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
16/33
Diffusion Welding Applications:
Joining of high-strength and refractory metals in aerospace andnuclear industries
Diffusion Welding is able to bond dissimilar metals, which are
difficult to weld by other welding processes:
Steel to tungsten Steel to niobium
Stainless steel to titanium
Gold to copper alloys
For joining dissimilar metals, a filler layer of different metal is
often sandwiched between base metals to promote diffusion
Diffusion Welding is used in rocket industries, electronics
applications, manufacturing composite materials
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
17/33
Explosion Welding (EXW):
SSW process in which rapid joining of two metallic surfaces iscaused by the energy of a detonated explosive
No filler metal used
No external heat applied
No diffusion occurs - time is too short
Bonding is metallurgical, combined with mechanical interlockingthat results from a rippled or wavy interface between the metals
Commonly used to bond two dissimilar metals
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
18/33
Explosion Welding (EXW):(1) Setup in parallel configuration, and(2) during detonation of the explosive charge
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
19/33
Explosion Welding (EXW): One of the welded parts (base plate) is rested on an anvil, the
second part (flyer plate) is located above the base plate with an
angled or constant interface clearance.
Explosive charge is placed on the flyer plate.
Detonation starts at an edge of the plate and propagates at high
velocity along the plate.
The slags (oxides, nitrides and other contaminants) are expelled
by the jet created just ahead of the bonding front.
Most of the metals and alloys may be bonded (welded) by
Explosive Welding.
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
20/33
Advantages of Explosive Welding
Large surfaces may be welded High quality bonding: high strength, no distortions, no porosity,
no change of the metal microstructure
Low cost and simple process
Surface preparation is not required
Disadvantages of Explosive Welding: Brittle materials (low ductility and low impact toughness)
cannot be processed
Only simple shape parts may be bonded: plates, cylinders
Thickness of flyer plate is limited - less than 2.5(63 mm)
Safety and security aspects of storage and using explosives
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
21/33
Explosion Welding (EXW) Applications:Dissimilar metals may be joined by Explosive Welding:
Copper to steel
Nickel to steel
Aluminum to steel
Tungsten to steel
Titanium to steel
Copper to aluminum
Explosive Welding is used for manufacturing tubes and pipes,pressure vessels, aerospace structures, heat exchangers, bi-
metal sliding bearings, ship structures, corrosion resistant
chemical process tanks.
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
22/33
Friction Welding (FRW):
SSW process in which joining is achieved by frictional heatcombined with pressure
When properly carried out, no melting occurs at faying surfaces
No filler metal, flux, or shielding gases normally used
Process yields a narrow HAZ
Can be used to join dissimilar metals
Widely used commercial process, agreeable to automation and
mass production
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
23/33
Friction Welding (FRW):(1) Rotating part, no contact
(2) parts brought into contact to generate friction heat(3) rotation stopped and axial pressure applied and
(4) weld created
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
24/33
Friction Welding (FRW) Limitations:
At least one of the parts must be rotational Flash must usually be removed (extra operation)
Upsetting reduces the part lengths (which must be taken into
consideration in product design)
Friction Welding (FRW)Applications: Shafts and tubular parts
Industries: automotive, aircraft, farm equipment, petroleum andnatural gas
Carbon steels, Alloy steels, Tool and die steels, Stainless steels,
Aluminum alloys, Copper alloys, Magnesium alloys, Nickel alloys,
Titanium alloys may be joined by Friction Welding.
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
25/33
Friction Stir Welding (FSW):
SSW process in which a rotating tool is fed along a joint linebetween two work-pieces, generating friction heat and
mechanically stirring the metal to form the weld seam
Distinguished from FRW because heat is generated by a separate
wear-resistant tool rather than the parts Applications: butt joints in large aluminum parts in aerospace,
automotive, and shipbuilding
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
26/33
Friction Stir Welding (FSW):(1) Rotating tool just before entering work, and(2) partially completed weld seam
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
27/33
Advantages and Disadvantages of Friction Stir Welding:Advantages Good mechanical properties of weld joint
Avoids toxic fumes, warping, and shielding issues
Little distortion or shrinkage
Good weld appearance
Disadvantages
An exit hole is produce when tool is withdrawn Heavy duty clamping of parts is required
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
28/33
Ultrasonic Welding (USW) Two work pieces are bonded as a result of a pressure exerted to
the welded parts combined with application of high frequency
acoustic vibration.
Oscillatory shear stresses of ultrasonic
frequency are applied to interface to
cause joining
Oscillatory motion breaks down any
surface films to allow intimate contact
and strong metallurgical bonding
between surfaces
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
29/33
Ultrasonic Welding (USW)
Ultrasonic cycle takes about 1 sec. The frequency of acoustic vibrations is in the range 20 to 70 KHz.
Thickness of the welded parts is limited by the power of the
ultrasonic generator.
Temperatures are well below Tm No filler metals, fluxes, or shielding gases
Generally limited to lap joints on soft materials
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
30/33
Ultrasonic Welding (USW)(a) General setup for a lap joint; and(b) close-up of weld area
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
31/33
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
32/33
Ultrasonic Welding (USW) Applications:
Wire terminations and splicing in electrical and electronicsindustry
Eliminates need for soldering
Assembly of aluminum sheet metal panels
Welding of tubes to sheets in solar panels
Assembly of small parts in automotive industry
Bonding of work pieces in electronics
For manufacturing communication devices
Medical tools, watches, automotive industry
-
7/27/2019 4 Unit 2- Solid State Welding (SSW)
33/33
Advantages of Ultrasonic Welding:
Dissimilar metals may be joined Very low deformation of the work pieces surfaces
High quality weld is obtained
The process may be integrated into automated production lines
Moderate operator skill level is enough
Disadvantages of Ultrasonic Welding: Only small and thin parts may be welded
Work pieces and equipment components may fatigue at the
reciprocating loads provided by ultrasonic vibration
Work pieces may bond to the anvil