PLASMA
WELDING
•
Plasma is commonly known as fourth state of matter after solid, liquid and gas.
This is an extremely hot substance which consists of free electrons, positive
ions, atoms and molecules. It conducts electricity.
How it works:
By positioning the electrode within the body of the torch, the plasma arc can be
separated from the shielding gas envelope. Plasma is then forced through a
fine-bore copper nozzle which constricts the arc. There are three operating
modes which can be produced by varying bore diameter and plasma gas flow
rate:
•Microplasma: 0.1 to 15A.
•Medium current: 15 to 200A.
•Keyhole plasma: over 100A.
The plasma arc is usually operated with a DC, drooping characteristic power
source. Because its unique operating features are results of the special torch
arrangement and separate plasma and shielding gas flows, a plasma control
console can be added on to a normal TIG power source. Full plasma systems
are also available. The plasma arc is not stabilised with sine wave AC. Arc
reignition is difficult when there is a long electrode to workpiece distance and the
plasma is constricted, extreme heating of the electrode during the positive halfcycle causes balling of the tip which can disturb arc stability. Special-purpose
switched DC power sources are available. By misbalancing the waveform to
reduce the duration of electrode positive polarity, the electrode is kept passably
cool to maintain a pointed tip and achieve arc stability.
• Electrode
The electrode used for the plasma process is tungsten2%thoria and the plasma nozzle is copper. The electrode
tip diameter is not as critical as for TIG and should be
maintained at around 30-60 degrees. The plasma nozzle
bore diameter is critical and too small a bore diameter for
the current level and plasma gas flow rate will lead to
excessive nozzle erosion or even melting. Large bore
diameter should be carefully used for the operating current
level.
Because too large a bore diameter, may give problems
with arc stability and maintaining a keyhole.
Plasma and shielding gases
The normal combination of gases is argon for the plasma
gas, with argon plus 2 to 5% hydrogen for the shielding
gas. Helium can be used for plasma gas but because it is
hotter this reduces the current rating of the nozzle.
Helium's lower mass can also make the keyhole mode
more difficult.
• Applications:
Microplasma welding:
Microplasma was traditionally used for welding thin sheets
(down to 0.1 mm thickness), and wire and mesh sections.
The needle-like stiff arc minimises arc wander and
distortion. Although the alike TIG arc is widely used, the
newer transistorised (TIG) power sources can produce a
very stable arc at low current levels.
Medium current welding:
When used in the melt mode this is a substitute to normal
TIG.
The advantages are:
1-Deeper penetration (from higher plasma gas flow).
2-Greater tolerance to surface contamination including
coatings (the electrode is within the body of the torch).
The major disadvantage lies in the bulkiness of the torch,
making manual welding more difficult. In mechanised
welding, greater attention must be paid to maintenance of
the torch to ensure consistent performance.
• Keyhole welding:
This has several advantages which can be
exploited: deep penetration and high welding
speeds. Compared with the TIG arc, it can
penetrate plate thicknesses up to l0mm, but when
welding using a single pass technique, it is more
usual to limit the thickness to 6mm. The normal
methods is to use the keyhole mode with filler to
ensure smooth weld bead profile (with no
undercut). For thicknesses up to 15mm, a vee joint
preparation is used with a 6mm root face. A twopass technique is employed and here, the first
pass is autogenous with the second pass being
made in melt mode with filler wire addition.
• As the welding parameters, plasma gas flow
rate and filler wire addition (into the keyhole)
must be carefully balanced to maintain the
keyhole and weld pool stability, this
technique is only suitable for mechanised
welding. Although it can be used for
positional welding, usually with current
pulsing, it is normally applied in high speed
welding of thicker sheet material (over 3 mm)
in the flat position. When pipe welding, the
slope-out of current and plasma gas flow
must be carefully controlled to close the
keyhole without leaving a hole.
Gas
MIG/TIG
Weldi
ng
Plasma Arc
Weldi
ng
Laser
Laser
Weldi
ng
Cuttin
g
Plasma
Cuttin
g
Acetylene
Oxy-Fuel
Cuttin
g
X
Air
Alumaxx Plus
X
Argon
X
X
Argon/hydrogen
TIG
X
Carbon dioxide
MAG
X
Thermal
Spraying
X
X
X
X
X
X
X
X
X
Carbon monoxide
X
Cooling
X
Ferromaxx Plus
MAG
Ferromax 15
MAG
Ferromaxx 7
MAG
Helium
TIG
X
X
X
Hydrogen
X
Inomaxx Plus
MAG
Inomaxx 2
MAG
Inomaxx TIG
TIG
X
Nitrogen
X
Nitrogen/hydrogen
mixes
X
Oxygen
X
X
X
X
X
Propane
X
X
Propylene
X
X
Arc Spraying
Arc spraying is the highest
productivity thermal spraying
process.
A DC electric arc is struck between
two continuous consumable wire
electrodes which form the spray
material.
Compressed gas (usually air)
atomises the molten spray material
into fine droplets and propels them
towards the substrate
The process is simple to operate- Can be used manually or in an automated manner.
Possible to spray a wide range of metals, alloys and metal matrix composites
(MMCs) in wire form.
A limited range of cermet coatings (with tungsten carbide) can also be sprayed in
cored wire form, where the hard ceramic phase is packed into a metal sheath as a
fine powder.
The combination of high arc temperature (6000 K) and particle velocities in excess of
100 m.sec-1 gives arc sprayed coatings superior bond strengths and lower porosity
levels when compared with flame sprayed coatings.
However, the use of compressed air for droplet atomization and propulsion
gives rise to high coating oxide content.
PLASMA SPRAYING PROCESS
•Uses a DC electric arc to generate a
stream of high temperature ionised
plasma gas, which acts as the
spraying heat source.
•The arc is struck between two nonconsumable electrodes, a tungsten
cathode and a copper anode within the
•
torch.
•The torch is fed with a continuous
flow of inert gas, which is ionised by
•
the DC arc, and is compressed and
accelerated by the torch nozzle so that
it issues from the torch as a high
velocity (in excess of 2000 m/sec),
high temperature (12000–16000 K)
plasma jet.
•
•The coating material, in powder form,
is carried in an inert gas stream into
the plasma jet where it is heated and
propelled towards the substrate.
Because of the high temperature and
high thermal energy of the plasma jet,
materials with high melting points
can be sprayed.
Plasma spraying produces a high
quality coating by a combination of a
high temperature, high energy heat
source, a relatively inert spraying
medium and high particle velocities,
typically 200–300 m.sec-1.
However, inevitably some air
becomes entrained in the spray
stream and some oxidation of the
spray material may occur. The
surrounding atmosphere also cools
and slows the spray stream.
Applications
• Plasma spraying is widely applied in the production of high
quality sprayed coatings.
• Spraying of seal ring grooves in the compressor area of
aeroengine turbines with tungsten carbide/cobalt to resist
fretting wear.
• Spraying of zirconia-based thermal barrier coatings (TBCs) onto
turbine combustion chambers.
• Spraying of wear resistant alumina and chromium oxide ceramic
onto printing rolls for subsequent laser and diamond
engraving/etching.
• Spraying of molybdenum alloys onto diesel engine piston rings.
HIGH VELOCITY OXYFUEL SPRAYING
The most recent addition to the thermal
spraying family, high velocity oxyfuel
spraying (HVOF SPRAYING) has
become established as an alternative to
the proprietary, detonation (D-GUN)
flame spraying and the lower velocity,
air plasma spraying processes for
depositing wear resistant tungsten
carbide-cobalt coatings.
This differs from conventional flame spraying in that the combustion process is
internal, and the gas flow fates and delivery pressures are much higher than
those in the atmospheric burning flame spraying processes.
The combination of high fuel gas and oxygen flow rates and high pressure in the
combustion chamber leads to the generation of a supersonic flame with
characteristic shock diamonds.
Flame speeds of 2000ms-1 and particle velocities of 600–800ms-1 are claimed by
HVOF equipment suppliers.
A range of gaseous fuels is currently used, including propylene, propane,
hydrogen and acetylene.
• Although similar in principle, potentially significant
details, such as powder feed position, gas flow rates
and oxygen to fuel ratio, are apparent between each
system.
• The HVOF process produces exceptionally high
quality cermet coatings (e.g., WC-Co), but it is now
also used to produce coatings of metals, alloys and
ceramics. Not all HVOF systems are capable of
producing coatings from higher melting point
materials, e.g., refractory metals and ceramics. The
capability of the gun is dependent upon the range of
fuel gases used and the combustion chamber design.
• A liquid fuel (kerosene) HVOF system, has just
been launched, which is capable of much higher
deposition rates than the conventional gas-fuelled
units.
Applications
HVOF spraying is a very recent process development, yet the high
quality of the coatings produced at competitive cost has already seen its
introduction in a number of very significant industries. Potential
applications overlap with plasma and D-gun spraying, particularly for
WC-Co coatings.
Tungsten carbide-cobalt coatings for fretting wear resistance on
aeroengine turbine components.
Wear resistant cobalt alloys onto fluid control valve seating areas.
Tungsten carbide-cobalt coatings on gate valves.
Various coatings for printing rolls, including copper, alumina, chromia.
NiCrBSi coatings (unfused) for glass plungers.
NiCr coatings for high temperature oxidation/corrosion resistance.
Alumina and alumina-titania dielectric coatings.
Biocompatible hydroxylapatite coatings for prostheses.
Schematic of High Velocity Oxyfuel (HVOF) Spraying System
Process
Particle
Velocity
(m/s)
Adhesion (MPa)
Oxide Content
(%)
Porosity (%)
Deposition Rate
(kg/hr)
Typical Deposit
Thicknes
s (mm)
Flame
40
<8
10–15
10–15
1–10
0.2–10
Arc
100
10–30
10–20
5–10
6–60
0.2–10
Plasma
200–300
20–70
1–3
1–8
1–5
0.2–2
HVOF
600–800
>70
1–2
1–2
1–5
Comparison of Thermal Spraying Processes and Coating
Characteristics
Typical Deposit
Thickness
(mm)
Particle Velocity (m/s)
Adhesion (MPa)
Oxide Content (%)
Porosity (%)
Deposition Rate
(kg/hr)
Flame
40
<8
10–15
10–15
1–10
0.2–10
Arc
100
10–30
10–20
5–10
6–60
0.2–10
Plasma
200–300
20–70
1–3
1–8
1–5
0.2–2
HVOF
600–800
>70
1–2
1–2
1–5
Process
Thermal Spraying Gases
Process
Fuels that can be used
Other gases
HVOF
Acetylene, hydrogen, propylene, propane, or liquid
kerosene depending on material type
Oxygen and argon
Arc spraying
Flame spraying
Plasma spraying
Normally compressed air but can use nitrogen or argon
Mainly acetylene, but sometimes propane depending on
material
Oxygen
Argon and hydrogen
LASER BEAM WELDING(LBW)
• LASER- Light Amplification by Stimulated
Emission of Radiation
• Focusing of narrow monochromatic light into
extremely concentrated beams (0.001 mm
even)
• Used to weld difficult to weld materials,
hard to access areas, extremely small
components, In medical field to weld
detached retinas back into place
• Laser Beam- coherent
Laser production- complex process.
The LASER, an
acronym for "Light
Amplification by
Stimulated Emission
of Radiation," is a
device that produces
a concentrated,
coherent beam of
light by stimulating
molecular or
electronic transitions
to lower energy
levels, causing the
emission of photons.
PFN- Pulse Forming Network
Al2O3 + 0.05% Chromium
• solid state RubyLaser- Neon flash tube emits
light into specially cut ruby crystals- absorbs
light -electrons of chromium atoms get
stimulated• Increase in stimulation ---- electrons increase
from normal(ground) orbit to an exited orbit.
More energy input- energy absorbed exceeds
thermal energy- no longer to heat energy.
• Electrons drop back to intermediate orbitemits PHOTONS (light) called spontaneous
emission
• With continued emission, released photons
stimulate other exited electrons to release
photons- called stimulated emission
• Causes exited electrons to emit photons
LASER WELDING
Slide 17 of 18
LASER WELDING
Slide 18 of 18
• Power intensities > 10 kw/cm2
• No physical contact between work and welding
equipment
• 2 mirrors- coherent light reflected back and forth,
becomes dense, penetrates partially reflective
mirror, focused to the exact point
• Very little loss of beam energy
• Solid state, liquid, semiconductor and gas lasers
used.
• Solid state uses light energy to stimulate
electrons Ruby, Neodymium, YAG
• Gas lasers use electrical charge to stimulate
electrons Gas lasers- higher wattage outputs.
Used for thicker sections - CO2, N2, He
• Liquid- nitrobenzene; Gas- based on gallium
Laser Welding Facts
• Laser Welding Advantages
• Processes high alloy metals without difficulty
• Can be used in open air
• Can be transmitted over long distances with a
minimal loss of power
• Narrow heat affected zone
• Low total thermal input
• Welds dissimilar metals
• No filler metals necessary
• No secondary finishing necessary
• Extremely accurate
• Welds high alloy metals without difficulty
• CO2 Laser Welding Speeds
• The solid-state laser utilizes a single
crystal rod with parallel, flat ends. Both
ends have reflective surfaces. A highintensity light source, or flash tube
surrounds the crystal. When power is
supplied by the PFN (pulse-forming
network), an intense pulse of light
(photons) will be released through one end
of the crystal rod. The light being released
is of single wavelength, thus allowing for
minimum divergence
• One hundred percent of the laser light will be
reflected off the rear mirror and thirty to fifty
percent will pass through the front mirror,
continuing on through the shutter assembly to
the angled mirror and down through the focusing
lens to the workpiece.
• The laser light beam is coherent and has a high
energy content. When focused on a surface,
laser light creates the heat used for welding,
cutting and drilling.
• The workpiece and the laser beam are
manipulated by means of robotics. The laser
beam can be adjusted to varying sizes and heat
intensity from .004 to .040 inches. The smaller
size is used for cutting, drilling and welding and
the larger, for heat treating
Laser Welding Limitations
• Rapid cooling rate may cause
cracking in certain metals
• High capital cost
• Optical surfaces easily damaged
• High maintenance cost
Laser beam cutting
•
Along with beam, oxygen used to help
cutting. Ar, He, N, CO2 also for steel,
alloys etc.
Two ways to weld
1. Work piece rotated or moved past beam
2. Many pulses of laser (10 times/sec)used.
Narrow HAZ., speeds of 40 mm/sec to 1.5
m/sec
Cooling system to remove the heatgas and liquid cooling used
• Klyston tubes (glass to metal
sealing), capacitor bank, triggering
device, flash tube, focusing lens, etc.
in the setup.
• Cathode of molybdenum, tantalum or
titanium used.
ULTRASONIC WELDING
Ultrasonic welding is an industrial technique
whereby two pieces of plastic or metal are joined
together seamlessly through high-frequency
acoustic vibrations.
One component to be welded is placed upon a fixed
anvil, with the second component being placed on
top.
An extension ("horn") connected to a transducer is
lowered down onto the top component, and a very
rapid (~20,000 Hz), low-amplitude acoustic vibration
is applied to a small welding zone.
The acoustic energy is converted into heat energy
by friction, and the parts are welded together in less
than a second
• Unique - no connective bolts, nails, soldering
materials, or adhesives are necessary to bind the
two parts together.
• Thus, saves on manufacturing costs and creates
unnoticeable seams in products where
appearance is important.
• A largely automated process
• But, it is only applied to small components watches, cassettes, plastic products, toys, medical
tools, and packaging.
• For example, the chassis of an automobile cannot
be assembled with ultrasonic welding because the
energies involved in welding larger components
would be prohibitive.
• In 1960 Sonobond Ultrasonics, originally
known as Aeroprojects Incorporated,
developed the first metal ultrasonic
welding machine to be awarded a United
States Patent
• Since early 90s, rapid developments
occured
• The range of materials that can be joined
together using this technique is increasing
• Earlier, only non-flexible plastics could be
welded because their material properties
allowed the efficient transmission of acoustic
energy from part to part.
• Nowadays, less rigid plastics such as
semicrystalline plastics can be welded
because large amounts of acoustic energy
can be applied to the welding zone.
• As the technology matures and becomes
more versatile, it is likely to obsolete large
classes of historical techniques for joining
materials together.
• Ultrasonic welding.
When bonding material through
ultrasonic welding, the energy
required comes in the form of
mechanical vibrations.
The welding tool (sonotrode)
couples to the part to be
welded and moves it in
longitudinal direction.
The part to be welded on remains
static. Now the parts to be
bonded are simultaneously
pressed together.
The simultaneous action of static
and dynamic forces causes
fusion of the parts without
having to use additional
material.
This procedure is used on an
industrial scale for linking both
plastics and metals
1.
2.
3.
4.
Anvil
Parts to be welded
Sonotrode
Ultrasonic oscillation
Differences in the process
for welding plastics and
metals with ultrasonics
Systems are composed of the same basic elements:
• A press to put the 2 parts to be assembled under pressure
• A nest or anvil where the parts are placed, allowing the high frequency
vibration to be directed to the interfaces
• An ultrasonic stack composed of a converter or piezoelectric transducer,
• An optional booster and a sonotrode (Horn).
All three elements of the stack are specifically tuned to resonate at the same
exact ultrasonic frequency (Typically 20, 30, 35 or 40 kHz)
– Converter: Converts the electrical signal into a mechanical vibration
– Booster: Modifies the amplitude of the vibration. It is also used in standard
systems to clamp the stack in the press.
– Sonotrode: Applies the mechanical vibration to the parts to be welded.
An electronic ultrasonic generator (US: Power supply) delivering a high
power AC signal with frequency matching the resonance frequency of the
stack.
A controller controlling the movement of the press and the delivery of the
ultrasonic energy
The mechanisms during ultrasonic metal welding
• Principle of ultrasonic metal welding
– 1. Sonotrode
– 2, 3 Parts to be joined
– 4. Anvil
– 5. Welding area
Applications
• The applications are extensive and are in many
industries including electrical and computer, automotive
and aerospace, medical, and packaging.
• Too thick pieces cannot be joined. This is the main
obstacle in the welding of metals.
• However, wires, microcircuit connections, sheet metal,
foils, ribbons and meshes are often joined using
ultrasonic welding.
• Ultrasonic welding is a very popular technique for
bonding thermoplastics. It is fast and easily automated
with weld times often below one second and there is no
ventilation system required to remove heat or exhaust.
• This type of welding is often used to build assemblies
that are too small, too complex, or too delicate for more
common welding techniques
Computer & electrical industries
•
•
•
•
•
•
Used to join wired connections and to create connections in small, delicate
circuits. Junctions of wire harnesses are often joined using ultrasonic welding
Wire harnesses are large groupings of wires used to distribute electrical signals
and power.
Electric motors, field coils, transformers and capacitors may also be assembled
with ultrasonic welding.
It is also often preferred in the assembly of storage media such as flash drives
and computer disks because of the high volumes required. Ultrasonic welding of
computer disks has been found to have cycle times of less than 300 ms.
Mostly used in microcircuits, since it creates reliable bonds without introducing
impurities or thermal distortion into components. Semiconductor devices,
transistors and diodes are often connected by thin aluminum and gold wires using
ultrasonic welding.It is also used for bonding wiring and ribbons as well as entire
chips to microcircuits. An example: in medical sensors used to monitor the human
heart in bypass patients.
Has the ability to join dissimilar materials. Example: The assembly of battery
components. When creating battery and fuel cell components, thin gauge copper,
nickel and aluminum connections, foil layers and metal meshes are often
ultrasonically welded together. Multiple layers of foil or mesh can often be applied
in a single weld eliminating steps and cost.
Aerospace & automotive industries
• Used in the assembly of large plastic components and electrical
components such as instrument panels, door panels, lamps, air ducts,
steering wheels, upholstery and engine components. As plastics are
replacing other materials in the design and manufacture of automobiles,
the assembly and joining of plastic components has increasingly
become a critical issue. Some of the advantages for ultrasonic welding
are low cycle times, automation, low capital costs, and flexibility. Also,
ultrasonic welding does not damage surface finish, which is a crucial
consideration for many car manufacturers, because the high-frequency
vibrations prevent marks from being generated.
• Used in the aerospace industry when joining thin sheet gauge metals
and other lightweight materials. Aluminum which is a difficult metal to
weld using traditional techniques because of its high thermal
conductivity, is one of the easier materials to weld using ultrasonic
welding because it is a softer alloy metal and thus a solid-state weld is
simple to achieve.
• Also, with the advent of new composite materials, ultrasonic welding is
becoming even more prevalent. It has been used in the bonding of the
popular composite material carbon fiber. Numerous studies have been
done to find the optimum parameters that will produce quality welds for
this material.
Medical industry
• USW does not introduce contaminants or degradation into
the weld and the machines can be specialized for use in
clean rooms.
• The process can also be highly automated, provides strict
control over dimensional tolerances and does not interfere
with the biocompatibility of parts.
• Thus increases part quality and decreases production costs.
• Items such as arterial filters, anesthesia filters, blood filters,
IV catheters, dialysis tubes, pipettes, cardiometry reservoirs,
blood/gas filters, face masks and IV spike/filters can all be
made using ultrasonic welding.
• Another important application is in textiles. Items like
hospital gowns, sterile garments, masks, transdermal
patches and textiles for clean rooms can be sealed and
sewn using ultrasonic welding. This prevents contamination
and dust production and reduces the risk of infection.
Packaging industry
• Many everyday items are either created or
packaged using ultrasonic welding techniques.
• Eg: Sealing containers, tubes and blister packs
.Also in the packaging of dangerous materials such
as explosives, fireworks and other reactive
chemicals. These items tend to require hermetic
sealing but cannot be subjected to high
temperatures.
• One example of this application is the container
for a butane lighter. This container weld must be
able to withstand high pressure and stress and
must be airtight to contain the butane.
Another example is the packaging of ammunition and
propellants- which must be able to withstand high pressure
and stresses in order to protect the consumer from the
contents. When sealing hazardous materials safety is a
primary concern. Thus, the reliability and automation of this
process are strong benefits for companies.
It is fast, sanitary and can produce hermetic seals. Milk and
juice containers are examples of some products that are often
sealed using ultrasonic welding.
The paper parts to be sealed are coated with plastic, generally
polypropylene or polyethylene, and then welded together to
create an airtight seal. The main obstacle to overcome in this
process is the setting of the parameters. If over-welding
occurs then the concentration of plastic in the weld zone may
be too low and cause the seal to break. If it is under-welded
the seal is incomplete. Also, variations in the thicknesses of
materials can cause variations in weld quality. Therefore, the
preparation is extremely important. Other food items that are
sealed include candy bar wrappers, frozen food packages and
beverage containers.
• In summary, It is increasing in popularity
throughout many of the industries because of
low cycle times, automation, low capital costs,
flexibility, cleanliness, dimensional reliability and
the bonding of dissimilar materials.
• Some of the drawbacks of ultrasonic welding are
that its use is limited by the thickness of the
materials, it may require expensive specialized
tooling and it may generate noise. As these
drawbacks are overcome by continually
developing technologies, it will be interesting to
see how this unique welding technique
continues to be utilized.
Safety
There are risk of some hazards: exposure to high heat levels and
voltages. This equipment to be operated using the safety guidelines
provided by the manufacturer in order to avoid injury. Must never place
hands or arms near the welding tip when the machine is activated. Also,
operators should be provided with hearing protection and safety glasses.
Operators should be informed of the OSHA regulations for the ultrasonic
welding equipment and these regulations should be enforced.
• Machines must receive routine maintenance and inspection. Panel doors,
housing covers and protective guards need to be removed for
maintenance with the power to the equipment off and only by the trained
professional who is servicing the machine.
Sub-harmonic vibrations may create annoying
audible noise, may be in larger parts near the
machine due to the ultrasonic welding frequency.
This noise can be dampened by clamping these
large parts at one or more locations.
Also, high-powered welders with frequencies of
15 kHz and 20 kHz typically emit a potentially
damaging high-pitched squeal in the range of human
hearing. Shielding this radiating sound can be done
using an acoustic enclosure.
In short, there are hearing and safety concerns with
ultrasonic welding that are important to consider, but
generally they are comparable to those of other
welding techniques.
Bibliography
• Assembly Magazine (2007). Welding Still Ensures High-Strength Joints,
Ultrasonic Welding Retrieved on 2008-03-13.
• American Welding Society (1997). Jefferson’s Welding Encyclodpedia.
USA: American Welding Society. ISBN 0-87171-506-6.
• American Welding Society (2001). Welding Handbook: Welding Science
and Technology. USA: American Welding Society. ISBN 0-87171-657-7.
• Ahmed, Nasir (Ed.), (2005). New Developments in Advanced Welding.
Boca Raton, Florida: CRC Press LLC. ISBN-10: 0-8493-3469-1.
• Grewell, David A.; Benatar, Avraham; & Park, Joon B. (Eds), (2003).
Plastics and Composites Welding Handbook. Cincinnati, Ohio: Hanser
Gardner Publications, Inc. ISBN 1-56990-313-1.
• Harras, B.; Cole, K. C.; & Vu-Khanh, T. (1996) Optimization of the
Ultrasonic Welding of PEEK-Carbon Composites. Retrieved on 2008-0224.
• Plastics Design Library (1997). Handbook of Plastics Joining: A Practical
Guide. Norwich, New York: Plastics Design Library. ISBN 1-884207-17-0.
• Plastics Technology (2008). Close Up on Technology: Top 50 Update Who Was First In Hot Runners, Ultrasonic Welding & PET? Retrieved on
2008-03-13.
• The Welding Institute (2007). Ultrasonic Welding Technique. Retrieved on
2008-02-24.
Electro slag welding
Some references site Robert Hopkins for
having invented the Electroslag welding
process in the 1930's. Most of his patents
relate to Electroslag melting for ingot
manufacture, not welding. However one
US patent, number 2,191481 filed in June,
1939 does describe the surfacing of one
material on another. The illustration,
however looks more like a melting furnace
than welding. In fact the fellow who
invented Submerged Arc Welding, Harry
Kennedy, was granted a US patent in
October of 1950, number 2,631,344,
assigned to Union Carbide that more
closely related to Electroslag
welding. However it too falls short of
defining what we know today as this
simple welding process.
Electro Slag Welding
ELECTROGAS WELDING
Slide 14 of 18